1
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
Chemical:
Sodium
Chlorate
PC
Code:
073301
DP
Barcode:
D303884
MEMORANDUM
DATE:
January
31,
2005
SUBJECT:
Sodium
Chlorate
(
CAS
Reg.
No.
7775­
09­
9)
Reregistration
(
Terrestrial
Food/
Feed
and
Non­
food/
Non­
feed
Uses)
Reregistration
Case
4049
Ecological
Risk
Assessment
FROM:
Brian
Anderson,
Biologist
Silvia
Termes,
Chemist
Environmental
Risk
Branch
3
and
James
Hetrick,
Chemist
Environmental
Risk
Branch
1
Environmental
Fate
and
Effects
Division
(
7507C)

THRU:
Dan
Rieder,
Branch
Chief
Environmental
Risk
Branch
3
Environmental
Fate
and
Effects
Division
(
7507C)

TO:
Rosanna
Louie
Special
Review
and
Reregistration
Division
(
SRRD)
(
7505C)
2
Attached
please
find
the
Environmental
Fate
and
Effects
Division's
(
EFED)
environmental
risk
assessment
for
reregistration
of
sodium
chlorate
as
an
herbicide
(
defoliant/
desiccant)
on
agricultural
commodities
and
in
non­
agricultural
areas.
Sodium
chlorate
(
chlorate)
is
a
nonselective
contact
herbicide
that
can
kill
all
green
parts
of
plants.
It
penetrates
the
cuticle
causing
cell
death,
probably
by
altering
the
metabolic
processes.
Chlorate
has
been
used
in
the
United
States
as
a
defoliant/
desiccant
at
least
since
the
early
1940s.
It
is
used
primarily
in
the
southern
United
States
on
cotton,
but
is
also
used
on
a
number
of
other
agricultural
commodities
at
application
rates
that
range
from
approximately
4
to
12.5
lbs
a.
i./
Acre.
Chlorate
is
also
used
for
a
number
of
non­
agricultural
applications
at
much
higher
rates
(
up
to
620
lbs
a.
i./
Acre).
The
enduse
products
containing
sodium
chlorate
as
the
active
ingredient
include
soluble
concentrates,
granular
products,
and
pellets.
Sodium
chlorate
is
also
an
inert
ingredient
in
some
pesticide
formulations,
where
it
is
used
because
its
antimicrobial
effects
retard
biodegradation
of
the
pesticide,
resulting
in
prolonged
pesticidal
activity.

This
risk
assessment
covers
the
technical
chlorate
active
ingredient
(
a.
i.),
13
end­
use
products
for
non­
agricultural
uses,
and
20
end­
use
products
for
agricultural
uses.
Key
findings
of
this
risk
assessment
are
as
follows:

°
Fish:
There
appears
to
be
no
acute
risk
to
fish
at
levels
of
concern
to
the
Agency.
However,
some
data
suggest
that
brown
trout
could
be
substantially
more
sensitive
than
other
fish
species
tested
to
chlorate's
toxicity.
It
is
uncertain
if
these
data
are
reliable;
therefore,
additional
testing
in
brown
trout
would
reduce
uncertainty
in
this
assessment.
No
chronic
toxicity
studies
are
available
to
allow
for
chronic
risk
to
fish
to
be
quantified.

°
Aquatic
Invertebrates:
Potential
risk
to
aquatic
invertebrates
cannot
be
precluded
because
a
chlorate
reduction
product,
chlorite,
is
approximately
6000­
fold
more
toxic
than
chlorate
to
aquatic
invertebrates.
There
are
insufficient
data
available
to
characterize
potential
exposure
to
and
risk
from
chlorite
as
a
result
of
chlorate
use.
Therefore,
this
potential
risk
could
not
be
quantified.
No
chronic
toxicity
data
are
available
in
aquatic
invertebrates;
therefore,
chronic
risk
to
fish
or
invertebrates
could
not
be
assessed.

°
Aquatic
Plants:
Data
in
Selenastrum
capricornutum
(
a
freshwater
green
alga)
were
submitted.
Although
these
data
suggest
that
there
is
not
risk
to
aquatic
plants
at
levels
of
concern
to
the
Agency,
data
on
all
required
aquatic
plant
species
have
not
been
submitted.
Therefore,
additional
data
are
needed
to
allow
for
a
full
characterization
of
potential
risk
to
aquatic
plants.

°
Birds,
acute
exposures:
No
mortality
occurred
in
the
submitted
avian
subacute
toxicity
studies
at
the
highest
concentration
tested
(
5620
mg/
kg­
diet).
Therefore,
risk
from
chlorate's
agricultural
uses
is
presumed
lower
than
the
Agency's
concern
level.
However,
acute
risk
to
birds
cannot
be
precluded
for
chlorate's
non­
agricultural
uses
because
environmental
concentrations
from
these
uses
were
estimated
to
be
significantly
higher
than
5620
mg/
kg­
diet
on
some
food
items.
3
°
Mammals,
acute
exposures.
Risk
cannot
be
precluded
from
chlorate's
agricultural
or
non­
agricultural
uses.
Even
though
chlorate
is
of
low
toxicity
to
mammals
(
10%
mortality
occurred
at
5000
mg/
kg­
bw),
some
of
chlorate's
non­
agricultural
uses
could
result
in
ingestion
of
chlorate
at
levels
that
are
significantly
higher
than
5000
mg/
kg­
bw
for
some
food
items.
Also,
levels
of
concern
could
be
exceeded
for
chlorate's
agricultural
uses
if
the
LD50
is
in
close
proximity
to
5000
mg/
kg­
bw.

°
Birds
and
mammals,
chronic
exposures.
No
reproduction
toxicity
data
have
been
submitted
to
allow
for
calculation
of
risk
quotients.
Chronic
risk
to
birds
and
mammals
are
presumably
higher
than
the
Agency's
level
of
concern
because
chronic
exposure
is
possible
and
repeated­
dose
toxicity
studies
in
mammals
suggest
that
chlorate's
effects
are
cumulative
(
toxicity
increases
as
exposure
duration
increases).
These
studies
suggest
that
repeated
exposures
may
adversely
affect
reproduction,
survival,
or
growth
at
concentrations
that
are
lower
than
the
EECs
presented
in
this
assessment.

°
Terrestrial
plants:
Adequate
data
are
not
available
to
allow
for
derivation
of
risk
quotients.
However,
risk
to
plants
is
presumably
higher
than
the
Agency's
concern
level
based
on
chlorate's
non­
selective
mode
of
action
and
high
labeled
application
rates.

Data
Gaps
and
Key
Uncertainties
The
following
major
data
gaps
were
noted
in
this
assessment:

Field
dissipation
study
(
164­
1).
Terrestrial
field
dissipation
data
are
not
available
and
this
study
was
never
waived.
There
are
some
reports
that
sodium
chlorate
can
be
persistent
in
the
field
(
6
months
to
5
years,
depending
on
rate
applied,
soil
type,
fertility,
organic
matter,
moisture,
and
weather
conditions).
However,
the
cited
information
do
not
provide
any
data
to
support
this
claim.
("
Inorganic
Herbicides",
Chapter
21
in
Weed
Science:
Principles
and
Practices
,
edited
by
G.
Klingman
and
F.
Ashton,
Published
by
Wiley,
1982).
Also,
several
labels
report
that
sodium
chlorate
is
effective
for
the
control
of
weeds
for
up
to
a
year,
which
indicates
that
chlorate
may
persist
for
up
to
a
year.
Therefore,
the
range
of
persistence
of
sodium
chlorate
in
the
field
remains
a
major
uncertainty
in
the
environmental
fate
behavior
of
this
chemical.
Use
of
sodium
chlorate
in
the
field
requires
that
it
be
applied
in
conjunction
of
a
fire
retardant
to
minimize
fire
incidents.
It
is
unclear
how
the
fire
retardant
could
influence
the
persistence
in
the
field.
Therefore,
the
EFED
recommends
that
field
persistence
data
from
actual
use
sites
be
submitted
to
the
Agency
upon
agreement
of
a
protocol
to
conduct
the
studies.

Reproduction
toxicity
study
in
bobwhite
quail
and
mallard
ducks
(
71­
4).
Toxicity
data
were
not
submitted
that
allow
for
calculation
of
risk
quotients.
Mammalian
toxicity
data
suggest
that
chlorate
is
more
toxic
after
repeated
exposures.

2­
Generation
reproduction
toxicity
study
in
laboratory
rats
(
83­
4).
Toxicity
data
were
not
submitted
to
allow
for
calculation
of
risk
quotients.
Subchronic
studies
suggest
that
repeated
exposures
may
adversely
affect
reproduction,
survival,
or
growth
at
concentrations
that
are
lower
4
than
chlorate's
agricultural
and
non­
agricultural
estimated
environmental
concentrations
(
EECs)
calculated
in
this
assessment.

Chronic
toxicity
studies
in
fish
and
aquatic
invertebrates
(
72­
4).
No
chronic
studies
have
been
submitted
to
the
Agency.
Chlorate
is
practically
non­
toxic
to
fish
and
aquatic
invertebrates
after
acute
exposures.

Acute
toxicity
studies
in
non­
guideline
fish
and
aquatic
plant
species.
Open
literature
studies
suggest
that
chlorate
may
be
particularly
toxic
to
brown
trout
and
to
brown
algae.
However,
sufficient
detail
is
not
available
in
the
study
reports
identified
in
the
open
literature
to
allow
for
an
adequate
assessment
of
study
quality.
Therefore,
submission
of
reliable
studies
in
these
species
could
be
of
considerable
value
to
this
assessment.

Tier
II
terrestrial
plant
seedling
emergence
and
vegetative
vigor
studies
(
123­
1).
Chlorate
is
a
non­
selective
herbicide.
Submitted
Tier
I
studies
suggest
that
chlorate
is
toxic
to
non­
target
plants
at
high
application
rates.

Tier
II
aquatic
plant
toxicity
studies
(
123­
2).
No
studies
in
the
following
plant
species
have
been
submitted,
which
are
required
for
herbicides:
Lemna
gibba
(
duckweed),
Skeletonema
costatum
(
a
marine
diatom),
Anabaena
flos­
aquae
(
a
blue­
green
bacterium),
and
a
freshwater
diatom.

Additional
key
uncertainties
include
the
following:

Fate
and
Exposure
°
Many
of
the
labels
are
not
clear
regarding
the
maximum
allowable
annual
applications
(
number
of
applications
or
total
load).
The
Agency
assumed
a
maximum
of
2
annual
applications
(
30­
days
apart)
for
cotton
and
1
annual
application
for
all
other
uses.
Risk
may
be
under­
estimated
if
these
assumptions
do
not
accurately
reflect
chlorate's
applications.

°
Many
of
the
non­
agricultural
uses
will
likely
result
in
small
contiguously
treated
areas,
which
would
reduce
the
likelihood
that
an
animal
would
consume
100%
of
its
diet
from
chlorate
treated
areas.
This
uncertainty
likely
resulted
in
an
over­
estimation
of
risk.

°
Chlorate
is
a
strong
oxidizer
and
may
be
reduced
to
other
chemically
related
species
under
some
environmental
conditions.
The
extent
and
rate
to
which
this
occurs
will
depend
on
the
redox
chemical
species
(
including
organic
matter)
in
the
water
or
soil.
Extensive
spatial
and
temporal
variability
is
expected
for
the
reactions
of
chlorate
in
the
environment.
However,
the
currently
available
simulation
models
do
not
allow
for
a
quantitative
evaluation
of
the
potential
exposure
levels
of
each
the
reduced
products
of
chlorate
(
i.
e.,
speciation
and
predominance)
and
how
fast
these
chemical
species
may
form.
Therefore,
there
is
a
high
degree
of
uncertainty
in
the
exposure
and
risk
assessment.
5
This
is
important
because
a
reduction
product
of
chlorate
(
chlorite)
is
expected
to
be
more
toxic
to
most
aquatic
and
terrestrial
species,
particularly
aquatic
invertebrates.

°
Sodium
chlorate
could
be
particularly
attractive
to
salt­
thirsty
mammals.
Therefore,
chlorate
body
burdens
could
be
substantially
higher
in
those
mammals
resulting
in
increased
risk.

Toxicity
°
Open
literature
toxicity
data
were
located
that
suggest
that
some
fish
and
algal
species
may
be
significantly
more
sensitive
to
chlorate
toxicity
than
the
surrogate
species
used
in
this
assessment.
Therefore,
submission
of
confirmatory
studies
in
non­
guideline
fish
and
algal
species
would
reduce
uncertainty
in
this
assessment
(
see
Section
3
for
additional
discussion).

°
An
LD50
of
1200
mg/
kg­
day
was
reported
in
the
open
literature
for
mammals.
However,
this
study
report
has
not
been
obtained
and
evaluated
by
the
Agency.
If
these
data
are
reliable,
then
risk
may
have
been
underestimated.

Scope
of
Assessment
°
Some
formulated
products
that
contain
sodium
chlorate
also
contain
other
active
ingredients
such
as
sodium
metaborate,
and
all
formulated
products
contain
flame
retardants.
In
some
formulated
products,
sodium
chlorate
is
present
at
concentrations
that
are
lower
than
these
other
active
ingredients.
Potential
effects
that
these
other
chemicals
may
have
on
chlorate's
fate
or
toxicity
is
not
considered
in
this
assessment.
Also,
risk
from
direct
effects
from
these
other
active
ingredients
is
not
within
the
scope
of
this
risk
assessment.

°
The
effects
of
prolonged,
year­
after­
year
use
of
sodium
chlorate
in
the
same
field
is
not
known,
particularly
in
semiarid
sites
that
require
irrigation
(
e.
g.,
Arizona,
California),
where
there
is
a
potential
for
salt
build­
up
over
time.

Labels
EFED
recommends
that
labels
be
revised
for
consistency.
Many
labels
do
not
allow
direct
application
to
water
(
surface
water;
intertidal
areas),
use
through
irrigation
systems,
contaminating
water
by
cleaning
of
equipment
or
disposal
of
rinsates,
discharge
into
sewage
systems
without
notifying
the
pertinent
sewage
treatment
plant
authority
(
PTOW),
and
carry
NPDES
license
restriction.
However,
not
all
of
the
current
labels
contain
all
of
the
language
necessary
to
protect
water
resources.
This
is
particularly
notorious
for
the
Non­
food/
non­
feed
products.
Many
of
the
listed
uses
in
this
pattern
appear
to
contradict
the
limitations
specified
in
6
most
of
the
Food/
Feed
labels
(
e.
g.,
drainage
systems;
sewage
systems).
Moreover,
some
of
the
Non­
food/
Non­
feed
labels
carry
restrictions/
warnings
that
are
not
included
in
those
for
Food/
Feed
uses,
such
as
ground
water
restrictions,
warnings
that
the
chemical
is
toxic
to
aquatic
invertebrates,
fish,
and
wildlife,
or
restricting
applications
on
sandy
soils.
Environmental
Fate
and
Ecological
Risk
Assessment
for
the
Reregistration
of
Sodium
Chlorate
as
an
Active
Ingredient
in
Terrestrial
Food/
Feed
and
Non­
food/
Non­
feed
Uses
Reregistration
Case
Number
4049
PC
Code
073301
Chemical
Abstracts
Registry
No.
7775­
09­
9
Brian
Anderson,
Biologist
Silvia
C.
Termes,
Chemist
Ecological
Risk
Branch
3
James
A.
Hetrick,
Senior
Scientist
Ecological
Risk
Branch
1
Henry
Nelson,
Chemist
Exposure
Assessment
Division
Office
of
Science
and
Coordination
Policy
(
OSCP/
OPPTS/
USEPA)

Environmental
Fate
and
Effects
Division
TABLE
OF
CONTENTS
1.
Environmental
Risk
Conclusions
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
2.
Problem
Formulation
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
5
2.1.
Initial
Considerations
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
5
2.2.
Stressor
Identification,
Source,
and
Distribution
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
7
2.3.
Exposure
Assessment
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
16
2.4.
Conceptual
Model
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
18
2.5.
Effects
Assessment
Approach
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
21
2.6.
Risk
Characterization
Approach
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
23
2.7.
Key
Uncertainties
and
Information
Gaps
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
23
3.
Analysis
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
25
3.1.
Environmental
Fate
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
25
3.2.
Exposure
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
33
3.3.
Ecological
Effects
Characterization
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
41
4.
Risk
Characterization
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
48
4.1.
Aquatic
Organisms
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
48
4.2.
Risks
to
Birds,
Acute
and
Chronic
Exposures
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
54
4.3.
Risk
to
Mammals,
Acute
Exposures
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
55
4.4.
Potential
Risk
to
Mammals,
Chronic
Exposures
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
61
4.5.
Endocrine
Disruption
Potential
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
61
4.6.
Potential
Risk
to
Terrestrial
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
61
4.7.
Uncertainties
in
the
Terrestrial
Organism
Risk
Assessment
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
62
4.8.
Potential
Risk
to
Threatened
and/
or
Endangered
Species
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
63
5.
References
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
67
LIST
OF
APPENDICES
Appendix
A.
Status
of
Data
Requirements
for
Sodium
Chlorate
Appendix
B­
1.
The
Chemistry
of
Chlorate
Appendix
B­
2.
Discussion
on
Chlorate
Redox
Chemistry
as
it
Relates
to
Exposure
to
Aquatic
Organisms
in
the
Environment
Appendix
C.
Areas
in
the
United
States
That
Grow
Selected
Commodities
on
Which
Sodium
Chlorate
Is
Used
Appendix
D.
Percent
of
Irrigated
Acres
Estimated
for
Cotton
Appendix
E.
Maximum
Labeled
Application
Rates
and
Crops
for
all
Agricultural
End­
Use
Products
Appendix
F.
Estimated
Average
Percent
Crop
Treated
for
Sodium
Chlorate
on
Selected
Crops
Appendix
G.
Description
of
the
Risk
Quotient
Method
Appendix
H.
Discussion
of
Waived
Environmental
Fate
Data
Appendix
I.
Impact
of
Sodium
from
Sodium
Chlorate
on
Soil
Quality
(
soil
dispersion)
Appendix
J.
Discussion
on
Chlorate
Redox
Chemistry
as
it
Relates
to
Exposure
to
Aquatic
Organisms
in
the
Environment
Appendix
K.
Terrestrial
EECs
for
the
Maximum
Labeled
Application
Rates
for
all
of
Sodium
Chlorate's
Current
End­
Use
Products
Appendix
L.
Summary
of
Publically
Available
Data
in
EPA's
ECOTOX
Database
Appendix
M.
Summary
of
Key
Toxicity
Studies
for
This
Assessment
1
1.
Environmental
Risk
Conclusions
Tables
1­
1
and
1­
2
below
summarize
the
major
conclusions
from
chlorate's
agricultural
and
nonagricultural
uses,
respectively.
Additional
details
are
in
Section
4
(
Risk
Characterization).
Table
1­
3
below
identifies
data
gaps
and
characterizes
potential
value
that
additional
testing
may
provide.
See
Appendix
A
for
the
status
of
all
data
requirements
for
chlorate.
2
Table
1­
1.
Summary
of
Environmental
Risk
Conclusions
for
Aquatic
and
Terrestrial
Organisms
(
Agricultural
Uses)

Surrogate
Species
Duration
of
Exposure
Summarized
Characterization
of
Potential
Risks
Potential
risk
to
fisha
Acute
The
submitted
data
suggest
that
risk
is
presumably
lower
than
the
Agency's
level
of
concern
for
acute
effects.

Chronic
No
chronic
toxicity
data
are
available;
therefore,
chronic
risk
to
fish
could
not
be
assessed.

Potential
Risk
to
Aquatic
Invertebratesa
Acute
The
Agency's
levels
of
concern
for
acute
effects
were
not
exceeded.
However,
risk
cannot
be
precluded
because
chlorite,
a
reduction
product
of
chlorate,
is
.6000­
fold
more
toxic
to
daphnids
than
chlorate,
and
there
are
insufficient
data
available
to
characterize
the
potential
of
chlorite
to
form
under
environmental
conditions.

Chronic
No
chronic
toxicity
data
are
available;
therefore,
chronic
risk
invertebrates
could
not
be
assessed.

Potential
risk
to
mammals
Acute
Risk
cannot
be
precluded
even
though
chlorate
is
of
low
toxicity
to
mammals
(
10%
mortality
occurred
at
the
highest
dose
tested
of
5000
mg/
kg­
bw).
If
the
LD50
is
in
close
proximity
to
5000
mg/
kg­
bw
there
may
be
potential
risk
to
some
mammals
at
levels
of
concern
to
the
Agency.

Chronic
No
reproduction
toxicity
data
have
been
submitted
to
allow
for
calculation
of
risk
quotients.
Chronic
risk
to
terrestrial
organisms
is
presumably
higher
than
the
Agency's
level
of
concern
because
chronic
exposure
appears
possible,
and
repeated­
dose
toxicity
studies
in
mammals
suggest
that
chlorate's
effects
are
cumulative
(
toxicity
increases
as
exposure
duration
increases).
These
studies
suggest
that
repeated
exposures
may
adversely
affect
reproduction,
survival,
or
growth
at
concentrations
that
are
lower
than
the
EECs
presented
in
this
assessment.

Potential
risk
to
birds
Acute
Risk
is
presumably
lower
than
the
Agency's
level
of
concern
based
on
chlorate's
low
acute
toxicity
to
birds.

Chronic
No
reproduction
toxicity
data
in
birds
are
available.
Studies
in
mammals
suggest
that
chlorate's
effects
are
cumulative,
and
repeated
exposure
appears
possible.
Therefore,
there
may
be
chronic
risk
to
birds
at
levels
of
concern
to
the
Agency.

Terrestrial
Plants
Acute
Adequate
data
are
not
available
to
allow
derivation
of
risk
quotients.
However,
risk
to
plants
is
presumably
higher
than
the
Agency's
concern
level
based
on
chlorate's
non­
selective
mode
of
action
and
high
application
rates.
Table
1­
1.
Summary
of
Environmental
Risk
Conclusions
for
Aquatic
and
Terrestrial
Organisms
(
Agricultural
Uses)

Surrogate
Species
Duration
of
Exposure
Summarized
Characterization
of
Potential
Risks
3
Potential
risk
to
aquatic
plants
Acute
and
chronic
Risk
to
endangered
or
non­
endangered
algae
cannot
be
precluded.
Submitted
core
algal
toxicity
data
indicate
that
chlorate
is
practically
non­
toxic
to
green
algae;
however,
green
algae
is
generally
a
poor
surrogate
for
vascular
plants.
Data
located
in
the
open
literature
suggest
that
brown
algae
are
considerably
more
sensitive
than
green
algae
to
chlorate.
A
14­
day
EC50
of
0.012
mM
(.
1
mg/
L)
and
a
NOAEC
of
<
0.005
mM
(.
0.42
mg/
L)
was
reported
for
brown
algae
(
van
Wijk
et
al.,
1997,
described
in
Appendix
M).

Sufficient
detail
was
not
available
in
the
published
study
report
to
allow
for
a
comprehensive
assessment
of
data
adequacy.

However,
the
EECs
for
chlorate's
agricultural
uses
were
as
high
as
0.91
mg/
L,
which
exceeds
the
reported
NOAEC
for
brown
algae
of
.0.42
mg/
L.
For
this
reason,
there
may
be
risk
to
endangered
algal
species
that
exceed
the
Agency's
level
of
concern
for
aquatic
plants.
Also,
aquatic
plant
toxicity
data
in
several
required
species
have
not
been
submitted;
therefore,
potential
risk
to
aquatic
plants
may
have
been
underestimated.

a
Risks
are
similar
for
freshwater
and
saltwater
species.

Table
1­
2.
Summary
of
Environmental
Risk
Conclusions
for
Aquatic
and
Terrestrial
Organisms
(
Non­
Agricultural
Uses)

Surrogate
Species
Duration
of
Exposure
Summarized
Risk
Characterization
And
Important
Uncertainties
Potential
Risk
to
Fish
Acute
and
chronic
Risk
conclusions
are
equivalent
to
those
presented
in
Table
1­
1.

Potential
Risk
to
Aquatic
invertebrates
Acute
and
chronic
Risk
conclusions
are
equivalent
to
those
presented
in
Table
1­
1.

Potential
Risk
to
Birds
Acute
Risk
cannot
be
precluded.
No
mortality
occurred
in
the
submitted
subacute
toxicity
studies
at
the
highest
concentration
tested
(
5620
mg/
kg­
diet);
however,
EECs
on
several
food
items
for
some
of
the
non­
agricultural
uses
are
significantly
higher
than
5620
mg/
kg­
food
item.

Chronic
Risk
conclusions
are
equivalent
to
those
presented
in
Table
1­
1.
Table
1­
2.
Summary
of
Environmental
Risk
Conclusions
for
Aquatic
and
Terrestrial
Organisms
(
Non­
Agricultural
Uses)

Surrogate
Species
Duration
of
Exposure
Summarized
Risk
Characterization
And
Important
Uncertainties
4
Potential
Risk
to
Mammals
Acute
Risk
cannot
be
precluded
even
though
chlorate
is
of
low
toxicity
to
mammals
(
10%
mortality
occurred
at
5000
mg/
kg­
bw).
Some
of
the
non­
agricultural
uses
could
result
in
ingestion
of
chlorate
at
levels
that
are
significantly
higher
than
5000
mg/
kg­
bw
for
some
food
items.

Chronic
Risk
conclusions
are
equivalent
to
those
presented
in
Table
1­
1.

Potential
risk
to
terrestrial
plants
Acute
Risk
conclusions
are
equivalent
to
those
presented
in
Table
1­
1.

Potential
risk
to
aquatic
plants
Acute
and
chronic
Risk
to
endangered
or
non­
endangered
algae
cannot
be
precluded.
Data
located
in
the
open
literature
suggest
that
brown
algae
are
considerably
more
sensitive
than
green
algae
to
chlorate.
However,
the
EECs
for
the
nonagricultural
uses
ranged
from
3.1
to
39
mg/
L,
which
all
exceed
the
reported
EC50
for
brown
algae
of
.1
mg/
L.

For
this
reason,
there
may
be
risk
to
endangered
and
non­
endangered
algal
species
that
exceed
the
Agency's
level
of
concern
for
aquatic
plants.
Also,
EFED
noted
several
data
gaps
in
the
aquatic
plant
toxicity
data
base
that
may
have
resulted
in
an
underestimation
of
risk.
5
Table
1­
3.
Data
Gaps
Identified
in
this
Assessment
and
Value
of
Additional
Testing
to
This
Assessment
Data
Gap
Value
of
Additional
Testing
to
Satisfy
the
Data
Gap
Comments
Field
dissipation
study
(
164­
1)
High
No
field
dissipation
data
have
been
submitted
to
the
Agency,
and
this
data
requirement
has
not
been
waived.
A
core
field
dissipation
study
would
allow
the
Agency
to
determine
the
likelihood
of
chronic
exposures
and
to
determine
the
potential
of
more
toxic
reduction
products
such
as
chlorite
to
form
in
the
environment.

2­
Generation
reproduction
toxicity
study
in
mammals
(
83­
4)
Higha
Toxicity
data
were
not
submitted
to
allow
for
calculation
of
risk
quotients.
Subchronic
studies
suggest
that
repeated
exposures
may
adversely
affect
reproduction,
survival,
or
growth
at
concentrations
that
are
lower
than
the
EECs
presented
in
this
assessment.

Reproduction
toxicity
study
in
birds
(
71­
4)
Higha
An
avian
reproduction
toxicity
study
has
not
been
submitted.
Mammalian
toxicity
data
suggest
that
chlorate
is
more
toxic
after
repeated
exposures.

Tier
II
terrestrial
plant
toxicity
studies
(
123­
1)
High
Chlorate
is
a
non­
selective
herbicide.
Submitted
Tier
I
studies
suggest
that
chlorate
is
toxic
to
non­
target
plants
at
high
application
rates.

Tier
II
aquatic
plant
toxicity
studies
in
Lemna
gibba
(
duckweed),
Skeletonema
costatum
(
a
marine
diatom),
Anabaena
flos­
aquae
(
a
bluegreen
bacterium),
and
a
freshwater
diatom.
(
123­
2)
High
Chlorate
is
a
non­
selective
herbicide
that
has
been
shown
to
be
toxic
to
some
aquatic
plants.
Only
data
in
green
algae
have
been
submitted.
Studies
in
the
four
other
aquatic
plant
species
listed
are
required
for
herbicides
and
would
substantially
reduce
uncertainty
in
this
assessment.

Acute
toxicity
studies
in
guideline
fish
and
aquatic
invertebrate
species
(
72­
1,
72­
2,
and
72­
3)
Low
No
core
studies
have
been
submitted.
The
submitted
supplemental
studies
suggest
that
chlorate
is
practically
non­
toxic
to
aquatic
organisms
(
EC50/
LC50
values
>
1000
mg/
L).
Submission
of
core
studies
would
not
likely
alter
the
conclusions
of
this
assessment.

Acute
toxicity
studies
in
nonguideline
fish
and
algal
species
Potentially
high
Open
literature
studies
suggest
that
chlorate
may
be
particularly
toxic
to
brown
trout
and
to
brown
algae.
However,
sufficient
detail
is
not
available
in
these
studies
to
allow
for
a
comprehensive
assessment
of
study
adequacy.
Therefore,
submission
of
reliable
studies
in
these
species
could
be
of
considerable
value
to
this
assessment.

Chronic
toxicity
studies
in
fish
and
aquatic
invertebrates
(
72­
4)
Moderatea
No
chronic
studies
have
been
submitted
to
the
Agency.
Chlorate
is
practically
non­
toxic
to
fish
and
aquatic
invertebrates
after
acute
exposures.

a
If
data
from
a
field
dissipation
study
indicate
low
potential
for
chronic
exposure,
then
the
value
of
this
study
could
be
reduced.
6
2.
Problem
Formulation
2.1.
Initial
Considerations
Methods
used
to
assess
risk
from
exposure
to
a
pesticide
are
dependent
on
its
environmental
fate,
physicochemical
properties,
use
information
(
rates,
method,
and
frequency
of
application),
and
target
crop/
site).
Some
of
the
important
factors
considered
in
this
risk
assessment
are
provided
in
Table
2­
1
below.

Table
2­
1.
Selected
Factors
Considered
in
the
Ecological
Risk
Assessment
of
Sodium
Chlorate
Consideration
Sodium
Chlorate­
Specific
Data
Effect
on
Risk
Assessment
Toxicity
Database
Adequate
non­
target
plant
toxicity
data
are
not
currently
available.
Risk
to
non­
target
plants
cannot
be
quantified.
Because
chlorate
is
an
herbicide
with
a
non­
selective
mode
of
action,
the
Agency
presumes
that
risk
to
non­
target
plants
exists
at
levels
of
concern
to
the
Agency
for
all
labeled
uses.

Adequate
chronic
or
reproduction
toxicity
data
for
use
in
ecological
risk
assessment
are
not
available
in
any
aquatic
or
terrestrial
organism.
Chronic
exposure
values
will
not
be
estimated,
and
the
Agency
cannot
preclude
chronic
risk
to
any
organism.

Discrete
LD50s
or
LC50s
could
not
be
estimated
because
chlorate
did
not
induce
mortality
in
birds
and
induced
10%
mortality
in
mammals
at
the
highest
chlorate
levels
tested.
Acute
risk
quotients
will
not
be
calculated
because
the
proximity
of
the
LD50/
LC50
to
the
highest
chlorate
levels
tested
cannot
be
estimated.
Potential
risk
will
be
qualitatively
assessed
by
comparing
the
highest
levels
tested
in
the
toxicity
studies
to
the
estimated
environmental
concentrations
(
EECs).

Open
literature
data
suggest
that
chlorate
may
be
particularly
toxic
to
brown
algae
and
brown
trout.
These
open
literature
studies
are
used
to
qualitatively
characterize
potential
risk
to
these
surrogate
species.

Environmental
Fate
Database
There
are
no
guideline
environmental
fate
studies
that
have
been
submitted
to
the
Agency.
However,
the
following
studies
have
been
waived:
Abiotic
Hydrolysis
(
161­
1);
[
Direct]
Photodegradation
in
Water
(
161­
2).
The
rationale
for
waiving
these
data
requirements
is
in
Section
3.
The
behavior
of
chlorate
in
the
environment
is
dependent
on
the
redox
conditions
of
the
medium
(
nature
and
concentration
of
reductants;
oxic
or
anoxic
conditions).
A
high
spatial
and
temporal
variability
is
expected
throughout
the
sites
where
chlorate
is
used
as
a
defoliant/
desiccant.
Therefore,
extremely
conservative
assumptions
were
made
for
the
exposure
estimates.
Consideration
Sodium
Chlorate­
Specific
Data
Effect
on
Risk
Assessment
7
Degradation
It
is
assumed
that
chlorate
may
be
persistent
in
the
field
under
some
environmental
conditions,
but
the
source
of
the
data
is
obscure.
For
example,
some
labels
indicate
that
chlorate
may
control
plant
growth
for
up
to
a
year.

A
potential
reduction
product
of
chlorate
is
chlorite.
Chlorite
is
more
toxic
to
some
organisms,
particularly
aquatic
invertebrates.
In
the
absence
of
data
indicating
otherwise,
the
Agency
assumes
that
short­
term
and
long­
term
exposure
to
chlorate
and
its
reduced
products
may
occur.

However,
the
distribution
and
concentration
of
chlorate
and
its
reduced
products
in
soil
and
water
as
a
function
of
time
could
not
be
obtained
because
of
lack
of
kinetics
data.
It
is
unlikely
that
all
chlorate
converts
to
all
chlorite
because
other
chemical
species
(
e.
g.,
chlorine
oxyanions
in
lower
oxidation
states)
can
also
form
and
react
further
via
redox
reaction
and/
or
disproportionation).

Thermodynamic
equilibrium
data
and
predominance
diagrams
showed
that,
at
chemical
equilibrium,
the
end
product
is
chloride
(
Cl­
).
Even
though
chlorite,
other
oxyanions,
and
chloride
may
be
present
together,
the
concentration
of
chlorite
and
other
species
at
any
given
time
post­
application
cannot
be
estimated
because
of
lack
of
kinetics
data.

Application
Method
Sodium
chlorate
may
be
applied
via
aerial
or
ground
spray
(
agricultural)
or
dispersed
as
a
granule
(
non­
agricultural)
or
pellet.
Consumption
of
granules
will
be
considered
in
this
assessment
using
the
LD50/
ft2
method
in
addition
to
the
standard
methods
used
to
assess
risk
from
spray
applications.
EFED
does
not
currently
assess
chronic
risk
from
exposure
to
granular
pesticides
(
U.
S.
EPA,
2004).

Number
of
Annual
Applications
The
number
of
annual
applications
is
not
specified
on
many
of
the
labels.
The
Agency
is
assuming
that
chlorate
is
to
be
applied
once
per
year
for
all
uses
where
the
label
does
not
specify
the
number
of
annual
applications
or
maximum
annual
load
(
except
cotton,
where
the
Agency
is
assuming
two
applications).

Use
Sodium
chlorate
is
labeled
for
use
on
a
number
of
agricultural
crops
and
non­
agricultural
areas
of
unspecified
size.
Some
non­
agricultural
uses
are
"
as
needed"
and
some
uses
are
spot
treatments.
EFED's
exposure
models
are
not
currently
designed
to
predict
aquatic
concentrations
from
some
of
these
uses.
Therefore,
estimated
aquatic
concentrations
may
be
highly
conservative
for
some
uses.

The
maximum
labeled
application
rates
of
the
non­
food
uses
are
extremely
high
(
up
to
650
lbs
a.
i./
Acre).
Based
on
the
very
high
application
rates,
additional
exposure
analyses
may
be
needed.
For
example,
consumption
of
contaminated
soil
could
result
in
high
body
burdens
for
some
animals.
1
The
use
of
chlorate
to
generate
chlorine
dioxide
in­
situ
is
not
considered
in
this
assessment
as
the
two
uses
have
completely
different
exposure
scenarios
(
Refer
to
"
Environmental
Fate
section)

8
2.2.
Stressor
Identification,
Source,
and
Distribution
2.2.1.
Assessment
of
Chemicals
of
Concern
Sodium
chlorate
(
also
referred
to
as
chlorate
in
this
assessment),
specifically
the
chlorate
anion,
is
the
chemical
stressor
to
which
non­
target
plant
and
animal
populations
may
be
exposed
and
is,
therefore,
the
primary
focus
of
this
risk
assessment.
1
Chlorate
is
a
strong
oxidizer
and
may
be
reduced
to
a
variety
of
chemical
species
depending
on
the
environmental
conditions.
This
assessment
also
considers
potential
exposure
to
and
risk
from
these
chemical
species.
However,
the
currently
available
data
and
the
complexity
of
processes
involved
in
the
formation
of
these
chemical
species
do
not
allow
for
a
quantitative
evaluation
of
the
potential
exposure
levels
to
them.
Therefore,
potential
risks
from
these
products
are
only
qualitatively
described.
The
Environmental
Fate
and
Effects
Division
(
EFED)
is
particularly
concerned
with
potential
exposure
to
chlorite,
which
has
been
shown
to
be
considerably
more
toxic
than
chlorate
to
some
species,
particularly
aquatic
invertebrates.

Several
end­
use
products
of
chlorate
also
contain
other
active
ingredients
(
e.
g.,
sodium
metaborate)
in
addition
to
flame
retardants.
Potential
effects
that
these
other
chemicals
may
have
on
chlorate's
fate
or
toxicity
is
not
considered
in
this
assessment.

2.2.2.
Physical
and
Chemical
Properties
of
Sodium
Chlorate
Chlorate,
an
inorganic
salt,
is
not
a
naturally
occurring
chemical.
It
is
made
by
electrolysis
of
brine
(
sodium
chloride)
under
controlled
temperature
and
pH
conditions
(
Appendix
B­
1)
to
optimize
the
efficiency
of
the
process
and
yield.

Physical
and
chemical
properties
of
a
chemical
can
be
used
a
priori
to
identify
potential
routes
of
exposure.
For
example,
the
vapor
pressure
and
Henry's
Law
Constant
provide
an
indication
of
the
potential
to
volatilize
from
soil
and
water
(
partitioning
into
air),
and
the
n­
octanol/
water
partition
coefficient
provides
an
indication
of
the
potential
to
bioaccumulate
in
fish
or
other
aquatic
organisms.
The
physical
and
chemical
properties
of
chlorate
are
summarized
in
Table
2­
2.
2
Crystal
System:
Cubic.
The
chlorate
anion
is
pyramidal,
with
Cl
at
the
apex
(
near
C3v
symmetry)
and
the
X­
ray
diffraction
pattern
serve
to
identify
chlorate,
as
X­
ray
diffraction
patterns
serve
as
"
fingerprint"
identification
method.

9
Table
2­
2.
Physical
and
Chemical
Properties
of
Chlorate
Physical
and/
or
Chemical
Property
Data
Selected
Synonyms
Soda
chlorate;
chloric
acid,
sodium
salt
Structure
Chemical
Abstract
Registry
Number
7775­
09­
9
Chemical
Class
Inorganic
Salt
Chlorate
is
one
of
the
oxyanions
of
chlorine.
The
oxidation
state
of
chlorine
in
chlorate
is
5,
represented
as
Cl(
V)
or
Cl
5+

Chlorate
is
a
monovalent
anion
Empirical
Formula
NaClO3
Molecular
Weight,
Daltons
106.5
Physical
State
Crystalline
Solid
(
hygroscopic)
2
Melting
Point
248
°
C
Boiling
Point
Not
applicable.
Decomposes
above
300
°
C,
with
release
of
oxygen
(
violently)

Solubility
in
Water
1.0
x
106
mgL­
1
at
25
°
C
(
highly
soluble)

Dissociation
Constant
Fully
ionized
Vapor
Pressure,
25
°
C
Negligible
7.3
x
10­
16
mm
of
Hg
9.7
x
10­
14
Pa
Henry's
Law
Constant
Negligible
1.0
x
10­
22
atm­
m3mole­
1
(
Estimated)

Log
n­
octanol/
water
Partition
Coefficient
(
Log
Kow)
­
7.08
(
Estimated)
Table
2­
2.
Physical
and
Chemical
Properties
of
Chlorate
Physical
and/
or
Chemical
Property
Data
3
Unless
they
chemisorb
to
soil
or
sediment
particulates.
Chemisorption
of
chlorate
is
unlikely.

4
The
term
"
redox
chemistry"
is
used
as
an
overall
term
for
oxidation
and
reduction
reactions.
Other
terms
that
are
frequently
used
for
oxidizers
are
"
oxidants",
"
oxidizing
agents".
Reductants
are
frequently
referred
to
as
"
reducing
agents".
All
redox
reactions
require
an
oxidant
and
a
reductant.
Reductants
are
electron
donors,
while
oxidants
are
electron
acceptors.

10
Other
Chlorate
is
considered
a
hazardous
material.
Although
stable
by
itself,
it
can
be
highly
flammable
when
in
contact
with
organic
material,
including
agricultural
materials
such
as
peat,
powdered
sulfur
and
other
organic
matter.
Therefore,
end­
use
products
containing
chlorate
as
the
active
ingredient
must
also
contain
a
fire
retardant
Based
on
the
low
vapor
pressure,
chlorate
is
not
expected
to
volatilize
from
soil.
The
low
log
noctanol
water
partition
coefficient
indicates
that
chlorate
has
low
potential
to
bioaccumulate.
Chlorate
is
highly
soluble
and
is
completely
ionized
in
water,
thus
producing
Na+
and
the
chlorate
(
ClO
3
­)
anion.
Anions
do
not
bind
readily
to
soil
or
sediment
particulates3
and,
therefore,
are
expected
to
be
very
mobile.
Assuming
that
chlorate
does
not
undergo
any
redox
reactions,
it
is
expected
to
be
very
mobile
and
to
partition
predominantly
into
the
water.
However,
extensive
redox
reactions
are
expected
to
occur
in
the
environment
that
will
reduce
the
concentration
of
chlorate
in
the
water
column.

The
redox
chemistry4
of
chlorate
affects
its
behavior
in
soils
and
natural
water.
Therefore,
identification
of
the
conditions
(
pH;
redox
potential,
"
E
h
"
or
pE)
under
which
chlorate
and
other
oxyanions
of
chlorine
may
predominate
is
an
important
consideration
in
the
environmental
fate
and
risk
assessment
of
chlorate.
The
oxidation­
reduction
reactions
of
chlorate
with
organic
matter
and
other
inorganic
chemical
species
are
very
complex
and
depend
on
the
redox
conditions
of
the
media,
nature
and
concentration
of
reductants,
chlorate
concentration,
temperature,
pH,
and
degree
of
moisture
(
soils).
Nitrate
concentrations
in
soil
and
water
(
as
well
as
other
physical
and
chemical
properties
of
soil
and
water)
play
an
important
role
in
the
redox
chemistry
of
chlorate
in
the
environment.

Open,
peer­
reviewed
chemical
literature
and
descriptive
chemistry
of
the
chlorine
system
were
used
as
the
basis
for
understanding
the
redox
behavior
of
chlorate
(
at
least
on
a
qualitative
basis;
Refer
to
Appendix
B­
1)
and
for
generating
a
screening­
level
environmental
fate
assessment.
Targeted,
guideline
studies
designed
to
understand
the
environmental
fate
of
chlorate
are
not
available.
Laboratory
guideline
studies
were
waived
as
it
was
considered
that
the
studies
would
not
provide
any
additional
information
above
what
is
already
known
in
the
open
chemical
literature
(
See
Appendix
H).
However,
major
spatial
and
temporal
variability
in
the
environmental
conditions
that
may
affect
the
redox
chemistry
of
chlorate
is
anticipated.
Thus,
5
Confidential
business
information
(
CBI)
restrictions
preclude
the
Agency
from
identifying
the
pesticide
formulations
in
which
chlorate
is
used
as
an
inert
ingredient
in
this
assessment.

11
attempts
were
made
to
identify
geographical
locations
and
seasons
where
and
when
chlorate
might
be
more
persistent.
For
this
purpose,
the
USDA's
Census
of
Agriculture
(
2002)
was
used
to
gather
information
on
the
number
of
acres
harvested
(
by
state)
for
specific
agricultural
commodities
on
which
chlorate
is
used
(
See
Section
2.2.4,
Use
Characterization).
The
number
of
harvested
acres
was
taken
as
an
indicator
of
areas
of
the
country
where
chlorate
might
be
used.
Since
the
degree
of
soil
humidity
is
important
for
application
of
chlorate,
the
percent
of
irrigated
acres
was
also
estimated
for
cotton
(
Appendix
D),
the
crop
of
major
use
of
chlorate.

2.2.3.
Mode
of
Action
Chlorate
is
a
non­
selective,
contact
herbicide
that
can
kill
all
green
parts
of
plants.
Chlorate
is
well
known
to
be
a
strong
oxidizing
agent.
Chlorate
is
absorbed
rapidly
by
plants
through
both
root
and
leaf
systems.
When
applied
as
a
foliar
spray,
chlorate
penetrates
the
cuticle
causing
cell
death,
probably
by
altering
the
metabolic
processes.
Soil
applications
result
in
translocation
through
the
xylem
of
living
tissue
of
plant
and
foliage.
As
a
consequence
of
its
reaction
as
an
oxidant,
it
generates
reduced
chloro
species
(
i.
e.,
chlorine
in
lower
oxidation
states
than
chlorate),
such
as
chlorite
and/
or
hypochlorite.
These
chemical
species
appear
to
inactivate
the
nitrogen
reductase
enzyme
or
disrupt
other
physiological
processes.
However,
the
exact
mechanisms
are
not
fully
understood.
In
addition,
injured
plants
can
cause
an
increase
in
production
of
ethylene,
auxins,
and
abscissic
acid,
which
cause
leaf
abscission.

2.2.4.
Use
Characterization
and
End­
Use
Products
Chlorate
has
a
long
use
history.
It
has
been
used
in
the
United
States
as
a
defoliant/
desiccant
at
least
since
the
early
1940s,
mostly
on
cotton.
In
spite
of
this,
behavior
of
chlorate
in
the
field
is
not
well
documented
nor
are
its
long­
term
effects
on
soils.

The
end­
use
products
containing
chlorate
as
the
active
ingredient
include
soluble
concentrates,
granular
products,
and
pellets.
Chlorate
end­
use
products
must
contain
a
fire
retardant
because
it
can
ignite
readily
when
in
contact
with
organic
matter.
No
data
were
located
that
document
the
effects
of
flame
retardants
on
chlorate's
toxicity
or
environmental
fate.

There
are
two
terrestrial
use
patterns
for
chlorate:
Food/
Feed
Use
(
agricultural
commodities)
and
Food/
Non­
Feed
(
non­
agricultural
sites).
Each
use
pattern
is
described
below.
Chlorate
is
also
an
inert
ingredient
in
some
pesticide
formulations,
where
it
is
used
because
its
antimicrobial
effects
retard
biodegradation
of
the
pesticide,
resulting
in
prolonged
pesticidal
activity.
Risk
from
these
uses
was
not
considered
in
this
assessment
because
exposure
of
non­
target
organisms
to
chlorate
from
these
uses
is
considered
negligible.
5
However,
its
soil
sterilizing
properties
could
have
adverse
effects
on
soil
quality
and
productivity
over
time.
6Defoliant:
Defoliation
is
the
process
by
which
leaves
are
abscised
from
the
plant.
While
other
process
such
as
drought,
low
temperature,
or
disease
can
induce
abscised
leaves,
the
term
"
defoliant"
is
used
for
chemicals
that
promote
the
process.

7
Desiccant:
Desiccation
by
chemicals
is
the
rapid
killing
or
drying
of
the
leaf
blades
and
petioles,
with
the
leaves
remaining
in
a
withered
state
in
the
plant.

12
Agricultural
Food/
Feed
Uses
Currently,
chlorate
is
used
primarily
as
a
harvest
aid
(
defoliant6,
desiccant7,
or
both).
All
of
the
end­
use
products
formulated
for
agricultural
uses
are
soluble
concentrates.
The
major
Food/
Feed
Use
is
on
cotton
(>
90%
of
agricultural
uses),
but
it
is
also
used
on
other
field
crops
(
See
Table
2­
3).
Application
rates
associated
with
each
agricultural
commodity
are
also
in
Table
2­
3.
The
data
were
compiled
by
the
Agency's
review
of
existing
labels.
A
summary
of
all
labeled
uses
for
each
registered
end­
use
product
is
in
Appendix
E.

Table
2­
3.
Summary
of
Agricultural
Commodities
and
Associated
Application
Rates
for
Labeled
Sodium
Chlorate
Formulations
Use
Range
of
Max
Labeled
Application
Ratesa
(
lbs
a.
i./
Acre)
Comments
Pepper
(
Chili
Type)
8.775
­
12.5
Maximum
number
of
applications
or
maximum
annual
load
not
specified
Potato,
White/
Irish
6
­
12.5
Maximum
number
of
applications
or
maximum
annual
load
not
specified
Beans,
dried­
type
Guar;
Southern
peas;
Safflower
Sorghum;
Soybeans;
Sunflower;
Flax
Corn;
Rice
(
air
only)
6
­
7.5
Maximum
number
of
applications
or
maximum
annual
load
not
specified
Cotton
4.5
­
7.5
Two
applications
of
the
maximum
application
rate
(
30­
day
interval)
assumed
by
the
Agency.
Labels
that
specifically
allow
multiple
applications
have
lower
maximum
application
rates
than
7.5
lbs
a.
i./
Acre.
However,
multiple
applications
of
7.5
lbs
a.
i./
Acre
are
not
precluded
in
the
labels
and
are
therefore
used
as
the
maximum
application
rate
in
this
assessment.

Cucurbit
Vegetables
6.1875
Maximum
number
of
applications
or
maximum
annual
load
not
specified
Use
Range
of
Max
Labeled
Application
Ratesa
(
lbs
a.
i./
Acre)
Comments
8
Data
from
the
Office
of
Pesticide
Programs
Label
Use
Information
System
(
LUIS)
report,
Table
A2
"
Food/
feed
Use
Patterns
Summary
for
Chlorate
(
CASE
4049)".
June
14,
2004.

13
Agricultural
fallow
/
idleland;
gourds;
wheatb
6
Maximum
number
of
applications
or
maximum
annual
load
not
specified
a
The
loading
in
terms
of
sodium
ranges
from
1.01
to
2.7
lbs
per
acre.
b
Wheat
has
been
covered
under
a
FIFRA
Section
18
Emergency
Exemption
tolerance
for
25
years.
The
current
exemption
is
scheduled
to
expire
on
December
31,
2004.
The
following
states
have
requested
a
Section
18
wheat
tolerance
in
the
past:
Arkansas,
Georgia,
Kansas,
Louisiana,
Mississippi,
Missouri,
North
Dakota,
Nevada,
New
Mexico,
Oklahoma,
and
Texas.

Many
of
the
labels
do
not
specify
the
maximum
number
of
applications
or
annual
load;
however,
some
labels
for
cotton
indicate
that
multiple
applications
may
be
necessary.
The
Agency
has
assumed
that
chlorate
may
be
applied
twice
annually
to
cotton
at
all
application
rates
with
a
30­
day
application
interval
and
is
applied
once
annually
for
all
other
uses.
8
This
assumption
may
have
resulted
in
an
under­
estimation
of
risk
if
chlorate
may
be
applied
more
than
twice
annually
(
or
at
shorter
application
intervals)
to
cotton
or
more
than
once
annually
to
other
crops.
Typical
application
rates,
number
of
applications,
and
application
intervals
were
not
located.

Figure
2­
1
below
illustrates
the
estimated
national
annual
chlorate
usage
rate
for
1998.
Appendix
C
illustrates
all
areas
in
the
United
States
that
grow
commodities
on
which
chlorate
is
used
where
such
data
are
available.
Percentage
of
each
agricultural
crop
on
which
chlorate
is
used
compared
with
the
total
amount
of
crop
grown
in
the
United
States
is
also
included
in
Appendix
F.
14
Figure
2­
1
1997
Use
Data
for
Sodium
Chlorate
Data
obtained
from
the
U.
S.
Geological
Survey
(
USGS)
and
are
available
at
the
following
url:
http://
ca.
water.
usgs.
gov/
cgi­
bin/
pnsp/
pesticide_
use_
maps_
1997.
pl?
map=
W8004
9
Chlorine
dioxide,
ClO2
(
Cl
oxidation
state
IV),
is
a
gas.
It
is
a
highly
energetic
molecule
and
a
free
radical
even
in
dilute
aqueous
solutions.
At
high
concentrations
it
reacts
violently
with
reductants.
It
is
only
stable
in
dilute
solutions
and
in
the
absence
of
light
(
i.
e.,
it
photolyzes).

15
Non­
Agricultural
Uses
Chlorate
is
used
to
control
perennial
weeds
(
morning
glory,
Canada
thistle,
and
Johnson
grass)
in
non­
agricultural
areas
and
for
vegetation
control
on
roadsides,
rights
of
ways,
and
other
public
and
industrial
areas.
The
maximum
labeled
application
rates
for
all
end­
use
products
are
in
Table
2­
4
below.
The
Agency
assumed
a
single
application
per
year
for
the
non­
agricultural
uses.
However,
many
of
the
labels
do
not
specify
the
maximum
number
of
annual
applications
or
maximum
annual
chlorate
load.
In
the
absence
of
such
data,
EFED
assumed
a
single
application.
This
assumption
may
have
resulted
in
an
under­
estimation
of
risk
if
multiple
applications
of
chlorate
are
allowed.

Chlorate
is
also
registered
as
a
biocide
for
drinking
water
treatment.
There
are
major
and
important
differences
between
its
use
as
a
biocide
and
its
use
as
a
defoliant/
desiccant.
As
a
disinfectant,
chlorate
is
used
to
generate
chlorine
dioxide
gas
in­
situ,
in
closed
containers
and
in
the
absence
of
light
(
i.
e.,
formation
of
stable
chlorine
dioxide
is
the
goal)
9.
As
a
defoliant/
desiccant,
chlorate
is
applied
to
an
open
field.
Thus,
it
is
exposed
to
an
open
environment
(
soil,
water,
air,
sunlight).
That
is,
the
scenarios
are
significantly
different
and,
therefore,
the
dissipation
behavior
is
expected
to
be
different.
The
present
assessment
only
considers
use
of
chlorate
in
terrestrial
fields.
Other
uses
are
assessed
by
the
Office
of
Pesticide
Program's
Antimicrobial
Division
and
the
Office
of
Water.
16
Table
2­
4.
Maximum
Application
Rates
for
Sodium
Chlorate's
Non­
Agricultural
Uses
Product
Max
App.
Rate
(
lbs
a.
i./
Acre)
a
Use
Description
Formulation
Ferti­
Lome
Special
Vegetation
Killer
650
(
under
asphalt)
325
(
other
uses)
Brick
walks,
patios,
parking
areas,
along
fences,
curbs,
gutters,
around
building,
graveled
pathways,
driveways,
under
asphalt
paving
Liquid
(
SC)

Perkerson's
Tri­
Ate
Weed
Killer
520
Parking
lots,
under
asphalt
paving,
fence
lines,
building
perimeters,
ditch
banks,
picnic
areas,
vacant
lots,
wood
decks,
bleachers,
cemeteries,
fuel
tanks,
runways,
helo
pads,
etc.
Granular
(
may
be
dissolved)

Barespot
Monobor
Chlorate
520
Bleachers,
fence
lines,
fire
hydrants,
guard
rails,
parking
lots,
under
driveways,
sidewalks,
asphalt
Granular
(
may
be
dissolved)

Barespot
weed
and
grass
390
Bleachers,
bridge
abutments,
buildings,
guard
rails,
helo
pads,
under
asphalt,
concrete,
gravel,
driveways,
sidewalks,
wood
decks.
Granular
Bareground
BD
240
Industrial
sites,
rights
of
way,
lumberyards,
petroleum
tank
farms,
around
farm
buildings,
along
fence
lines,
and
similar
areas
Liquid
(
SC)

Barespot
Ureabor
240
Bleachers,
fence
lines,
fire
hydrants,
helo
pads,
parking
lots,
runways,
vacant
lots.
Granular
Grass,
weed,
and
vegetation
killer
220
Driveways,
walks,
patios,
tennis
courts,
curbs,
garages,
etc.
Liquid
(
SC)

Tri­
Kil
nonselective
weed
and
grass
killer
160
Fence
rows,
rights­
of­
ways
and
similar
areas
Liquid
(
SC)

AllPro
Baracide
5PS
Pelleted
Herbicide
160
Around
buildings,
storage
areas,
fences,
recreational
areas,
guard
rails,
highway
medians,
industrial
sites.
Pelleted/
Tableted
Prometon
5PS;
Pramitol
5
PS
160
Around
buildings,
storage
areas,
fences,
pumps,
machinery,
fuel
tanks,
recreational
areas,
roadways,
guard
rails,
airports,
rights
of
ways.
Pelleted/
Tableted
Riverdale
Killsall
Liquid
140
Driveways,
parking
lots,
walks,
around
fences,
curbs,
similar
areas.
Not
for
use
on
lawns.
Liquid
(
SC)

Perkerson's
Tri­
Chlor
Weed
Killer
52
Industrial
sites
such
as
driveways,
paths,
brick
walks,
cobble
gutters,
tennis
courts
Liquid
(
SC)

a
Application
rates
were
generally
given
in
lbs
a.
i./
100
ft2
and
were
converted
to
lbs
a.
i./
Acre
(
100
ft2
=
0.0023
acres).
10
Although
a
bioconcentration
study
has
not
been
submitted
to
the
Agency,
the
extremely
low
Log
Kow
of
chlorate
indicates
that
it
will
not
bioconcentrate
or
bioaccumulate.

17
The
labels
for
the
non­
agricultural
terrestrial
uses
preclude
direct
application
to
water.
Therefore,
risk
to
aquatic
organisms
from
direct
application
to
water
was
not
assessed.

2.2.5.
Persistence,
Bioaccumulation,
and
Toxicity
(
PBT)
Screen
for
Sodium
Chlorate
Chlorate
is
toxic
to
plants
and
may
be
persistent
under
some
environmental
conditions;
however,
its
low
bioconcentration
potential
precludes
it
from
meeting
the
screening
level
characteristics
of
a
PBT
chemical.
10
See
Section
3
(
Analysis)
for
a
discussion
of
chlorate's
relevant
environmental
fate
properties
that
relate
to
its
persistence
and
bioaccumulation
potential
and
for
a
discussion
on
the
available
toxicity
data.

2.3.
Exposure
Assessment
Approach
2.3.1.
Aquatic
Organism
Exposure
Approach
The
GENeric
Expected
Environmental
Concentration
(
GENEEC­
2)
model
was
used
to
calculate
EECs
for
all
uses
included
in
this
assessment.
The
GENEEC­
2
program
is
a
simple
model
that
uses
a
chemical's
soil/
water
partition
coefficient
and
degradation
half­
life
values
to
estimate
runoff
from
a
ten
hectare
field
into
a
one
hectare
by
two
meter
deep
pond.
It
should
be
noted
that
none
of
EFED's
current
surface
water
simulation
models
that
calculate
EECs
are
designed
for
inorganic
chemicals
such
as
chlorate
for
which
formation
of
reaction
products
is
controlled
by
pH
and
redox
potential
nor
are
they
capable
of
indicating
the
distribution
and
concentration
of
the
reduced
products.
In
addition,
GENEEC­
2
estimates
will
likely
be
very
conservative
for
the
nonagricultural
uses
because
the
model
assumes
that
a
contiguous
drainage
basin
flows
into
a
pond
that
is10­
times
smaller
than
the
treated
area.
The
application
scenarios
for
the
non­
agricultural
uses
may
not
be
consistent
with
the
scenario
assumed
by
GENEEC­
2.

The
rate
and
extent
of
formation
of
reduction
products
of
chlorate
will
be
dependent
on
the
chemical
nature
and
concentration
of
environmental
reductants
present
in
the
environment
in
which
chlorate
is
released.
However,
data
on
chlorate­
specific
reductant
reaction
rates
(
i.
e.,
kinetics)
are
scarce
and
mostly
under
conditions
not
relevant
to
the
environment
(
e.
g.,
very
acid
or
very
alkaline
media;
reductants
not
likely
to
be
found
in
the
environment).
Therefore,
EFED
calculated
peak
EECs
under
the
assumption
that
chlorate
remains
stable.
This
assumption
likely
resulted
in
high­
end
chlorate
concentrations
in
aquatic
systems.
Chronic
exposure
values
(
21­
or
60­
day)
are
not
presented
in
this
assessment
because
no
chronic
toxicity
data
are
available
for
comparison.
11
Although
EXAMS
has
some
capability
to
introduce
redox
data,
kinetics
data
is
also
needed.
Given
the
lack
of
chlorate­
specific
reductant
kinetics
data,
at
this
time
EXAMS
is
not
adequate
to
handle
inorganic
chemicals
that
can
exist
in
more
than
one
oxidation
state.

18
Attempts
were
made
to
refine
the
aquatic
EECs
using
higher
tier
models
such
as
PRZM
and
EXAMS11.
However,
none
were
found
to
be
adequate
simulation
models
for
chlorate
as
they
cannot
adequately
handle
redox
systems.
Given
that
there
is
a
major
uncertainty
in
the
kinetics
and
reaction
products
under
field
conditions,
the
use
of
higher
tier
simulation
models
or
other
approaches
may
give
a
perception
of
higher
confidence
in
the
aquatic
EECs
than
is
justified
by
the
available
data.

Other
approaches
using
available
thermodynamics
data
were
also
attempted
(
Section
3.1).
However,
all
were
considered
to
be
inappropriate
as
they
were
not
able
to
determine
the
speciation
(
i.
e.,
which
chemical
species
will
form
and
their
distribution)
and
predominance
(
relative
amount
of
each
of
the
potential
chemical
species)
that
may
occur
under
environmental
conditions.
Thermodynamics
data
only
indicate
which
chemical
species
can
form,
but
do
not
indicate
that
they
will
form
and
at
what
rate.
Nevertheless,
EFED
used
thermodynamic
data
to
estimate
which
of
the
chlorine
species
could
be
found
within
the
pH­
pE
range
of
natural
waters
(
see
Section
3.1).

EFED
did
not
use
its
interim
rice
model
to
calculate
EECs
from
chlorate
use
on
rice
because
the
model
calculates
EECs
in
a
flooded
rice
paddy.
As
a
desiccant,
chlorate
will
likely
be
applied
after
the
rice
fields
have
been
drained.
Therefore,
GENEEC­
2
was
used
to
calculate
EECs
from
all
uses
considered
in
this
assessment.

2.3.2.
Terrestrial
Organism
Exposure
Approach
Chlorate
may
be
applied
as
a
spray
or
as
granules.
EFED's
methods
for
assessing
exposure
to
terrestrial
organisms
are
different
for
each
of
these
application
methods
and
are
discussed
below.

Spray
Applications
The
focus
of
terrestrial
wildlife
exposure
estimates
is
for
birds
and
mammals
with
an
exposure
route
emphasis
on
uptake
through
the
diet.
For
exposure
to
terrestrial
organisms,
the
Agency
estimates
the
residue
concentrations
of
pesticides
on
food
items
and
assumes
that
organisms
are
exposed
to
one
active
ingredient
in
a
given
exposure
scenario.
For
chlorate
spray
applications,
estimation
of
pesticide
concentrations
in
wildlife
food
items
focuses
on
quantifying
possible
dietary
ingestion
of
residues
on
vegetative
matter
and
insects.
The
residue
estimates
are
based
on
nomograms
that
relates
food
item
residues
to
pesticide
application
rate
(
Fletcher
et
al.,
1994).
The
nomograms
are
incorporated
into
a
first­
order
residue
decline
model,
"
ELL­
FATE",
which
allows
determination
of
residue
dissipation
over
time
by
incorporating
degradation
half­
life.
Two
nomograms
are
used
in
this
ecological
risk
assessment:
One
is
based
on
the
maximum
residue
concentrations
and
one
based
on
mean
residue
concentrations
reported
by
Fletcher
et
al.
(
1994).
19
Residues
may
be
compared
directly
with
dietary
toxicity
data
or
converted
to
an
oral
dose,
as
is
the
case
for
small
mammals.
For
mammals,
the
residue
concentration
is
converted
to
daily
oral
dose
based
on
fractions
of
body
weight
consumed
daily
as
estimated
through
mammalian
allometric
relationships.
In
all
screening­
level
assessments,
the
organisms
are
assumed
to
consume
100%
of
their
diet
as
one
food
type.
These
exposure
estimates
are
only
applicable
to
the
applied
pesticide,
chlorate.
It
is
uncertain
to
what
extent
exposure
to
reduced
species
of
chlorate,
such
as
chlorite,
may
occur.

Granular
applications
For
granular
applications,
estimation
of
chlorate
loading
per
unit
area
(
mg/
ft2)
are
calculated.
This
approach,
which
is
intended
to
represent
exposure
via
multiple
routes
(
e.
g.,
incidental
ingestion
of
contaminated
soil,
dermal
contact
with
treated
seed
surfaces
and
soil
during
activities
in
the
treated
areas,
preening
activities,
and
ingestion
of
drinking
water
contaminated
with
pesticide)
and
not
just
direct
ingestion,
considers
observed
effects
in
toxicity
studies
and
relates
them
to
the
pesticide
applied
to
surface
area.
The
maximum
labeled
application
rate
for
the
active
ingredient
is
the
basis
for
the
exposure
term.

2.3.3.
Terrestrial
Plant
Exposure
Approach
Adequate
toxicity
data
are
not
available
to
perform
a
risk
assessment
(
see
Section
3,
Analysis);
therefore,
risk
to
non­
target
terrestrial
plants
was
not
quantified.
Based
on
chlorate's
nonselective
mode
of
action,
EFED
presumes
high
risk
to
all
non­
target
plants
pending
receipt
of
adequate
toxicity
data.

2.4.
Conceptual
Model
In
order
for
a
chemical
to
pose
an
ecological
risk,
it
must
reach
ecological
receptors
in
biologically
significant
concentrations.
An
exposure
pathway
is
the
means
by
which
a
contaminant
moves
in
the
environment
from
a
source
to
an
ecological
receptor.
For
an
ecological
exposure
pathway
to
be
complete,
it
must
have
a
source,
a
release
mechanism,
an
environmental
transport
medium,
a
point
of
exposure
for
ecological
receptors,
and
a
feasible
route
of
exposure.
The
assessment
of
ecological
exposure
pathways,
therefore,
includes
an
examination
of
the
source
and
potential
migration
pathways
for
constituents,
and
the
determination
of
potential
exposure
routes
(
e.
g.,
ingestion,
inhalation,
dermal
absorption).

Ecological
receptors
that
may
potentially
be
exposed
to
chlorate
and
its
degradates
include
wildlife
and
plants
in
terrestrial
and
semiaquatic
areas
(
e.
g.,
mammals,
birds,
reptiles,
invertebrates).
In
addition
to
terrestrial
ecological
receptors,
aquatic
receptors
(
e.
g.,
freshwater
and
estuarine/
marine
fish
and
invertebrates,
amphibians,
reptiles)
may
also
be
exposed
to
potential
migration
of
pesticides
from
the
site
of
application
to
various
watersheds
and
other
aquatic
environments
via
runoff
and
spray
drift.
12
Chlorine
dioxide
(
gas)
is
among
the
chemical
species
that
can
result
from
reduction
of
chlorate.
However,
photolysis
is
a
major
and
rapid
dissipation
pathway
for
chlorine
dioxide.

20
The
source
and
mechanism
of
release
of
chlorate
is
application
via
foliar
spray
(
ground
or
aerial
application)
on
agricultural
crops
or
chlorate
application
of
foliar
spray
or
distribution
of
granules
to
non­
agricultural
areas.
Based
on
the
expected
high
mobility
of
chlorate,
surface
water
runoff
from
the
areas
of
application
is
assumed
to
be
the
primary
route
of
exposure
in
aquatic
systems.
Additional
release
mechanisms
include
spray
drift,
and
wind
erosion
of
soil
containing
residues
of
chlorate,
which
may
potentially
transport
site­
related
contaminants
to
the
surrounding
area.
Potential
emission
of
volatile
compounds
is
not
considered
as
a
viable
release
mechanism
for
chlorate
because
it
has
a
negligible
vapor
pressure
and
a
very
high
solubility
in
water.
Therefore
volatilization
is
not
expected
to
be
a
transport
route
for
chlorate12.
The
conceptual
model
below
generically
depicts
the
potential
source
of
chlorate,
release
mechanisms,
receiving
media,
and
biological
receptors
for
chlorate's
use.
21
Sodium
Chlorate
Application
Spray
Drift
Runoff
/
Erosion
Aquatic
Environments
(
redox
cycling)

Leaching
/
Subsurface
Transport
Dermal
Uptake
Gill
Uptake
Ingestion
Aquatic
Vertebrates
/
Invertebrates
Terrestrial
and
Semi­
Aquatic
Environments
(
redox
cycling)

Dermal
Uptake
Ingestion1
Birds
/
Mammals
Direct
Contact
/

Root
Uptake
Aquatic
Plants
Direct
Contact
/

Root
Uptake
Terrestrial
and
Semi­

Aquatic
Plants
1
Direct
ingestion
of
granules
or
ingestion
of
contaminated
food
items.

Spray
drift
is
considered
negligible
for
granular
applications
Absorption
into
Treated
Foliage
22
2.5.
Effects
Assessment
Approach
Assessment
endpoints
are
defined
as
"
explicit
expressions
of
the
actual
environmental
value
that
is
to
be
protected
(
U.
S.
EPA,
2004)."
Defining
an
assessment
endpoint
involves
two
steps:
1)
identifying
the
valued
attributes
of
the
environment
that
are
considered
to
be
at
risk,
and
2)
operationally
defining
the
assessment
endpoint
in
terms
of
an
ecological
entity
(
i.
e.,
a
community
of
fish
and
aquatic
invertebrates)
and
its
attributes
(
i.
e.,
survival
and
reproduction).
Therefore,
selection
of
the
assessment
endpoints
is
based
on
valued
entities
(
i.
e.,
ecological
receptors),
the
ecosystems
potentially
at
risk,
the
migration
pathways
of
pesticides,
and
the
routes
by
which
ecological
receptors
are
exposed
to
pesticide­
related
contamination.
The
selection
of
clearly
defined
assessment
endpoints
is
important
because
they
provide
direction
and
boundaries
in
the
risk
assessment
for
addressing
risk
management
issues
of
concern.

The
typical
assessment
endpoints
for
screening­
level
ecological
risk
assessments
include
reduced
survival
and
impairment
of
reproductive
and
growth
of
freshwater
and
saltwater
organisms
and
terrestrial
species.
Potential
effects
on
a
set
of
surrogate
species
are
used
to
extrapolate
risk
to
all
species.
Surrogate
aquatic
organisms
include
freshwater
and
saltwater
fish
and
invertebrates.
Benthic
organisms
were
not
specifically
assessed
for
chlorate
because
it
is
not
expected
to
partition
to
the
sediment.
In
the
absence
of
toxicity
data
on
amphibians,
it
is
assumed
that
aquatic­
phase
amphibians
are
approximately
as
sensitive
as
fish
to
potential
effects
of
a
pesticide.
Surrogate
terrestrial
animal
species
include
birds
and
mammals.
This
screening­
level
assessment
assumes
that
reptiles
and
terrestrial­
phase
amphibians
are
approximately
as
sensitive
to
pesticideinduced
effects
as
birds.
For
both
aquatic
and
terrestrial
animal
species,
direct
acute
and
direct
chronic
effects
are
considered.
Indirect
effects
to
listed/
endangered
species
resulting
from
direct
effects
on
food­
items
and
habitat
are
also
considered.

Each
assessment
endpoint
requires
one
or
more
"
measures
of
ecological
effect,"
which
are
defined
as
changes
in
the
attributes
of
an
assessment
endpoint
itself
or
changes
in
a
surrogate
entity
or
attribute
in
response
to
exposure
to
a
pesticide.
Ecological
measurement
endpoints
for
the
screening
level
risk
assessment
are
based
on
a
suite
of
toxicity
studies
performed
on
a
limited
number
of
organisms
in
the
broad
groupings
indicated
in
Table
2­
5
below.
Within
each
of
those
very
broad
taxonomic
groups
in
animals,
an
acute
and
chronic
endpoint
is
selected
from
the
available
test
data,
as
the
data
sets
allow.
Chronic
effects
in
plants
is
not
currently
assessed
by
EFED.

A
summary
of
the
assessment
and
measurement
endpoints
selected
to
characterize
potential
ecological
risks
associated
with
exposure
to
chlorate
is
provided
in
Table
2­
5
below.
A
more
comprehensive
discussion
of
all
toxicity
data
available
for
this
risk
assessment
and
the
resulting
measurement
endpoints
selected
for
each
taxonomic
group
are
included
in
Appendix
M
of
this
document.
23
Table
2­
5.
Summary
of
Assessment
and
Measurement
Endpoints
Surrogate
Species
Assessment
Endpoint
Measurement
Endpointa
Substance
Tested
Birds
Abundance
(
i.
e.,
survival,
reproduction,
and
growth)
of
bird
populations
Acute
Exposures:
LD50
in
mallard
ducks
and
bobwhite
quail
Short­
term
(
Subacute)
Exposures:
LC50
in
mallard
ducks
and
bobwhite
quail
Chronic
Exposures:
No
available
data
TGAIb
TGAIb
Mammals
Abundance
(
i.
e.,
survival,
reproduction,
and
growth)
of
mammal
populations
Acute
Exposures:
Laboratory
rat
acute
oral
LD50
(
mg/
kg­
bw)
Chronic
Exposures:
Developmental
toxicity
study;
subchronic
toxicity
studies*

*
A
2­
generation
reproduction
toxicity
study
in
rodents
is
typically
used
by
EFED
to
estimate
potential
risk
to
mammals
from
chronic
exposures;
however,
such
data
on
sodium
chlorate
were
not
available.
TGAIb
Freshwater
Aquatic
Organisms
Survival
and
reproduction
of
freshwater
fish
and
invertebrate
communities
Acute
Exposures:
Daphnia
Magna,
rainbow
trout,
and
bluegill
sunfish.

Chronic
Exposures:
No
chronic
studies
were
submitted.
TGAIb
NA
Estuarine/
marine
organisms
Survival
and
reproduction
of
estuarine/
marine
fish
and
invertebrate
communities
Acute
Exposures:
Acute
studies
in
fish
(
sheepshead
minnows)
and
invertebrates
(
mysid
shrimp
and
oysters).
Chronic
Exposures:
No
chronic
studies
were
submitted.
NA
Plants
(
terrestrial
and
semi­
aquatic
environments)
Perpetuation
of
populations
of
non­
target
terrestrial
and
semiaquatic
species
(
crops
and
non­
crop
plant
species)
Adequate
toxicity
data
are
not
available
for
screening
level
assessment.
TGAI
Plants
(
aquatic
environments)
Maintenance
and
growth
of
standing
crop
or
biomass
of
aquatic
plant
populations
EC50
and
NOAEC
from
96­
hour
study
in
green
algae.
TGAI
a
LD
50
=
Lethal
dose
to
50%
of
the
test
population.
NOAEC
=
No
observed
adverse
effect
concentration.
LOAEC
=
Lowest
observed
adverse
effect
concentration
LC
50
=
Lethal
concentration
to
50%
of
the
test
population.
EC
50
=
Effect
concentration
to
50%/
25%
of
the
test
population.
b
TGAI
=
Technical
grade
active
ingredient
24
2.6.
Risk
Characterization
Approach
Risk
characterization
is
the
integration
of
exposure
and
effects
characterization
to
determine
the
ecological
risk
from
the
use
of
the
pesticide
and
the
likelihood
of
effects
on
aquatic
life,
wildlife,
and
plants
based
on
varying
pesticide­
use
scenarios.
The
risk
characterization
provides
an
estimation
and
a
description
of
the
risk;
articulates
risk
assessment
assumptions,
limitations,
and
uncertainties;
synthesizes
an
overall
conclusion;
and
provides
the
risk
managers
with
information
to
make
regulatory
decisions
regarding
a
pesticide.

Results
of
the
exposure
and
toxicity
effects
data
are
used
to
evaluate
the
likelihood
of
adverse
ecological
effects
on
non­
target
species.
For
the
screening
level
assessment
of
chlorate
risks,
the
risk
quotient
(
RQ)
method
is
used
to
compare
exposure
and
measured
toxicity
values.
Estimated
environmental
concentrations
(
EECs)
are
divided
by
acute
and
chronic
toxicity
values
to
derive
risk
quotients.
The
RQs
are
compared
to
the
Agency's
levels
of
concern
(
LOCs).
These
LOCs
are
the
Agency's
interpretive
policy
and
are
used
to
analyze
potential
risk
to
non­
target
organisms
and
the
need
to
consider
refinement
or
regulatory
action.
These
criteria
are
used
to
indicate
when
a
pesticide
is
used
as
directed
on
the
label
has
the
potential
to
cause
adverse
effects
on
non­
target
organisms.
Appendix
G
of
this
document
summarizes
the
LOCs
used
in
this
risk
assessment.
Risk
characterization
is
composed
of
risk
estimation
and
risk
description.
Risk
quotients
are
calculated
in
the
risk
estimation
section
for
each
endpoint,
and
characterization
and
interpretation
of
risk
is
described
in
the
risk
description
section
for
each
endpoint
assessed.

2.7.
Key
Uncertainties
and
Information
Gaps
in
This
Assessment
The
following
uncertainties
and
information
gaps
were
identified
as
part
of
the
problem
formulation
(
additional
uncertainties
identified
in
this
assessment
are
reported
in
the
individual
sections
of
this
report):

Fate
and
Exposure
°
Many
of
the
labels
are
not
clear
regarding
the
maximum
allowable
annual
applications
(
number
of
applications
or
total
load).
The
Agency
assumed
a
maximum
of
2
annual
applications
(
30
days
apart)
for
cotton
and
1
annual
application
for
all
other
uses
for
this
assessment.
Risk
may
be
under­
estimated
if
these
assumptions
do
not
accurately
reflect
chlorate's
applications.

°
Chlorate
is
a
strong
oxidizer
and
may
be
reduced
to
other
chemically
related
species
under
some
environmental
conditions.
The
extent
and
rate
to
which
this
occurs
will
depend
on
the
redox
chemical
species
(
including
organic
matter)
in
the
water
or
soil.
Extensive
spatial
and
temporal
variability
is
expected
for
the
reactions
of
chlorate
in
the
environment.
However,
the
currently
available
simulation
models
do
not
allow
for
a
quantitative
evaluation
of
the
13
See
for
example
the
documents
on
chlorate
found
at
the
following
URLs:
http://
extoxnet.
orst.
edu/
pips/
sodiumch.
htm
(
For
the
issue
of
persistence
in
the
field
(
6
months
to
5
years),
primary
references
cited
in
this
review
were
consulted,
but
the
basis
of
these
claims
are
not
documented.
Therefore,
the
issue
of
persistence
in
the
field
remains
uncertain).
http://
wlapwww.
gov.
bc.
ca/
wat/
wq/
BCguidelines/
chlorate.
html#
properties
http://
www.
ams.
usda.
gov/
nop/
NationalList/
TAPReviews/
SodiumChlorate.
pdf
25
potential
exposure
levels
of
each
the
reduced
products
of
chlorate
(
i.
e.,
speciation
and
predominance).
Therefore,
there
is
a
high
degree
of
uncertainty
in
the
exposure
and
risk
assessment.

°
Terrestrial
field
dissipation
data
have
not
been
submitted
(
164­
1).
There
are
some
reports
that
chlorate
can
be
persistent
in
the
field
(
6
months
to
5
years,
depending
on
rate
applied,
soil
type,
fertility,
organic
matter,
moisture,
and
weather
conditions)
13.
However,
the
cited
information
is
not
readily
available
to
assess
the
validity
of
the
claims.
Also,
several
labels
report
that
chlorate
is
effective
for
the
control
of
weeds
for
up
to
a
year,
which
indicates
that
chlorate
may
persist
for
up
to
a
year.
Therefore,
the
range
of
persistence
of
chlorate
in
the
field
remains
as
a
major
uncertainty
in
the
environmental
fate
behavior
of
this
chemical.

Toxicity
°
The
toxicity
database
is
limited.
No
chronic
or
reproductive
toxicity
data
(
aquatic
or
terrestrial
organisms)
considered
adequate
for
screening
level
ecological
risk
assessment
were
available.
These
limitations
in
the
toxicity
database
introduce
considerable
uncertainty
in
this
risk
assessment.

°
Adequate
non­
target
terrestrial
plant
data
are
not
available
for
this
assessment.
Therefore,
risks
to
non­
target
plants
were
not
quantified.
In
the
absence
of
such
data,
and
based
on
the
non­
specific
mode
of
action
of
chlorate,
EFED
presumes
considerable
risk
to
non­
target
plants.

°
Open
literature
toxicity
data
were
located
that
suggest
that
some
fish
and
algal
species
may
be
more
sensitive
to
chlorate
toxicity
than
the
surrogate
species
used
in
this
assessment.
Therefore,
submission
of
confirmatory
studies
in
non­
guideline
fish
and
algal
species
would
reduce
uncertainty
in
this
assessment
(
see
Section
3
for
additional
discussion).
Also,
a
lower
LD50
value
in
rats
than
used
in
this
assessment
has
been
reported.
The
Agency
was
unsuccessful
in
locating
this
study
report
for
evaluation,
but
the
data
could
suggest
that
risk
to
mammals
may
have
been
under­
estimated.

Scope
of
Assessment
°
Surrogate
organisms
were
used
to
predict
potential
risks
for
species
with
no
data
(
i.
e.,
reptiles
and
amphibians).
It
was
assumed
that
use
of
surrogate
toxicity
data
are
sufficiently
14
Review
articles
on
the
use
of
sodium
chlorate
as
a
defoliant/
desiccant
mention
that
chlorate
can
be
persistent
in
the
field
(
6
months
to
as
long
as
5
years).
However,
the
primary
references
do
not
provide
any
supporting
data
for
these
claims.(
See
Footnote
13).

Chlorate
can
be
highly
flammable
when
in
contact
with
organic
material,
including
agricultural
materials
such
as
peat,
powdered
sulfur
and
other
organic
matter.
Therefore,
end­
use
products
containing
chlorate
as
the
active
ingredient
must
also
contain
a
fire
retardant,
which
in
turn
may
prolong
the
activity
of
chlorate
after
application.

26
conservative
and
would
capture
the
distribution
of
toxicity
to
the
broad
range
of
species
within
taxonomic
groups.
As
previously
discussed,
some
data
located
in
the
open
literature
suggest
that
there
may
be
more
sensitive
fish
and
algal
species
than
the
surrogate
species
used
in
this
assessment.

°
Inhalation
and
dermal
pathways
for
birds
and
mammals
were
not
evaluated.
Exposures
from
these
pathways
are
assumed
to
be
negligible
given
the
low
volatility
and
limited
expected
dermal
absorption
(
based
on
physicochemical
properties)
of
chlorate.

°
Risks
to
top­
level
carnivores
were
not
evaluated.
Ingestion
of
grass,
plants,
fruits,
insects,
and
seeds
by
terrestrial
wildlife
was
considered;
however,
consumption
of
small
mammals
and
birds
by
carnivores
was
not
evaluated.
In
addition,
food
chain
exposures
for
aquatic
receptors
(
i.
e.,
fish
consumption
of
aquatic
invertebrates
and/
or
aquatic
plants)
were
also
not
considered.
However,
chlorate's
low
Kow
suggests
that
the
substance
is
not
likely
to
bioaccumulate.

°
Sodium
Chlorate
is
formulated
with
other
active
ingredients
and
with
flame
retardants.
Potential
effects
that
these
other
chemicals
may
have
on
chlorate's
fate
or
toxicity
is
not
considered
in
this
assessment.
However,
the
fire
retardant
may
affect
the
persistence
of
chlorate
in
the
field.
14
°
The
effects
of
prolonged,
year­
after­
year
use
of
chlorate
in
the
same
field
is
not
known,
particularly
in
semiarid
sites
that
require
irrigation
(
e.
g.,
Arizona,
California),
where
there
is
a
potential
for
salt
build­
up
over
time.

°
Although
some
"
greenhouse"
studies
performed
in
the
early
1940s
claim
that
there
are
no
soil
sterility
issues,
it
is
uncertain
how
many
years
of
use
at
the
same
sites
have
affected
the
soil
physical
and
chemical
properties
and
microbial
population.

3.
Analysis
3.1.
Environmental
Fate
Environmental
fate
data
from
target,
guideline
laboratory
studies
are
not
available.
EFED
has
previously
waived
the
following
data
requirements:
(
161­
1),
Abiotic
Hydrolysis;
(
161­
2)
[
Direct]
15
The
EFED
considered
loading
of
Na+
to
soils
and
concluded
that
it
did
not
have
an
impact
in
soils
under
most
use
conditions
(
See
Appendix
I).

27
Photodegradation
in
Water;
(
161­
3),
Photodegradation
on
Soil;
(
162­
1/
162­
2),
Aerobic/
Anaerobic
Soil
Metabolism;
(
162­
3/
162­
4),
Anaerobic/
Aerobic
Aquatic
Metabolism
;
(
163­
1)
Mobility
in
Soil.
Also,
neither
the
vapor
pressure
nor
the
n­
octanol
water
partition
coefficient
trigger
the
need
for
volatility
from
soil
(
163­
2)
and
bioaccumulation
in
fish
(
165­
4)
studies.
These
study
requirements
were
waived
because
they
were
not
likely
to
produce
results
beyond
what
is
already
known
about
chlorate's
environmental
fate.
Discussion
on
the
justification
for
waiving
these
data
requirements
is
in
Appendix
H.
However,
the
field
dissipation
study
requirement
has
never
been
waived
and
remains
a
data
gap.
Based
on
the
lack
of
guideline
environmental
fate
studies,
this
environmental
fate
assessment
provides
a
qualitative
overview
of
chlorate's
expected
environmental
fate.

3.1.1.
Environmental
Fate
Assessment
of
Sodium
Chlorate
Chlorate
is
fully
ionized
in
water,
and
is
expected
to
dissociate
immediately
when
added
to
moist
soil.
The
very
low
vapor
pressure
and
very
high
solubility
of
chlorate
in
water
suggest
that
volatilization
of
chlorate
from
soil
and
water
is
an
unlikely
transport
route.
In
addition,
the
very
low
n­
octanol/
water
partition
coefficient
indicates
that
it
is
not
a
lipophilic
chemical
and
therefore,
has
low
potential
to
bioaccumulate
in
fish
or
other
aquatic
organisms.

As
an
anion,
chlorate
is
not
likely
to
adsorb
to
soil/
sediment
particulates.
Therefore,
on
this
basis
alone,
chlorate
has
a
high
leaching
and
run­
off
potential,
particularly
when
heavy
rainfall
occurs
immediately
after
application,
where
it
can
be
washed
out
of
the
site
of
applications.
These
general
routes
of
dissipation
assume
that
chlorate
remains
as
"
chlorate".
That
is,
that
redox
reactions
of
chlorate
are
not
taken
into
account.

The
pesticide
active
species
in
chlorate
is
the
chlorate
anion
(
ClO
3
­)
15.
Chlorate
is
a
strong
oxidizer
(
electron
acceptor)
and
its
mode
of
action
as
a
defoliant/
desiccant
is
linked
to
its
oxidizing
properties.
As
an
oxidizer
(
electron
acceptor),
the
reactions
of
chlorate
in
the
environment
are
dominated
by
natural
electron
donor
chemical
species
(
reductants).
Knowledge
of
the
redox
chemistry
of
chlorate
is
key
in
understanding
its
behavior
in
the
environment,
at
least
qualitatively.
Appendix
B­
1
contains
an
expanded
discussion
of
the
redox
chemistry
of
chlorate
and
related
chemical
species.
However,
an
attempt
has
been
made
to
qualitatively
identify
conditions
at
which
chlorate
may
be
less
persistent
and
the
products
that
may
potentially
form.

The
following
considerations
were
taken
into
account
to
qualitatively
characterize
the
behavior
of
chlorate
in
the
environment
and
are
discussed
below:

A.
Redox
conditions
in
the
environment
B.
Identification
of
electron
donors
(
reductants)
and
electron
acceptors
(
oxidizers)
in
the
environment
(
inorganic
and
organic).
16
Chlorate
is
obtained
via
electrolytic
reactions
of
brine
(
NaCl).
The
efficiency
of
chlorate
formation
by
this
process
is
controlled
by
temperature
and
pH.,
with
stability
(
as
measured
by
yield)
increasing
with
increasing
pH.
However,
the
presence
of
chemical
species
that
can
act
as
reductants
(
such
as
some
ionic
transition
metals)
decrease
the
efficiency
of
the
process.
This
is
a
good
example
of
how
the
presence
of
reductants
can
control
the
stability
of
chlorate.

17
The
pE
(
pE=
­
log
E)
scale
is
analogous
to
that
of
pH.

28
C.
Potential
reduction
products
of
chlorate
in
the
environment
A.
Reducing
and
Oxidizing
Conditions
in
the
Environment.

Chlorate
is
more
stable
under
alkaline
than
acidic
conditions16.
Thus,
based
on
pH
dependence
alone,
chlorate
would
be
predicted
to
be
less
persistent
in
acidic
than
alkaline
natural
waters.
However,
when
a
chemical
element,
such
as
chlorine,
can
exist
in
two
or
more
oxidation
states,
it
must
also
be
considered
whether
the
aqueous
environment
is
well
aerated
(
oxidizing
environment)
or
polluted
with
organic
wastes
or
other
chemical
species
that
may
serve
as
electron
donors
(
reducing
environment).
That
is,
the
predominance
of
specific
reduction
products
of
chlorate
is
dependent
on
pH
and
redox
potential
(
E
h
)
of
the
media.
The
redox
potential
can
also
be
expressed
in
a
pE
scale,
which
is
the
notation
used
in
this
assessment17.
Likewise,
the
redox
environment
of
the
soil
is
also
expected
to
control
the
redox
behavior
of
chlorate
in
soils.

Redox
Conditions
in
Natural
Waters
The
following
redox
conditions
have
been
identified
for
abiotic
transformation
in
water
and
are
classified
based
on
their
redox
potential
(
in
mV).

Table
3­
1.
Redox
Potentials
in
Water*

Redox
Conditions
Redox
Potentials,
mV
Strongly
Oxidizing
+
400
to
+
800
Moderately
Oxidizing
+
200
to
+
400
Moderately
Reducing
­
50
to
+
200
Reducing
­
200
to
­
50
Strongly
Reducing
­
400
to
­
200
*
Wolfe,
N.,
et
al.
1990.
Abiotic
transformations
in
water,
sediments
and
soil.
In
Pesticides
in
the
Soil
Environment,
Soil
Science
Society
of
America,
pp.
103­
110.
29
The
redox
conditions
of
the
water
body
can
control
the
persistence
of
chlorate.
In
reducing
environments
(
i.
e.,
low
E;
pE),
chlorate
would
be
less
persistent
than
in
oxidizing
environments
(
high
E;
pE).
Therefore,
a
seasonal
and
geographical
variability
in
the
nature
and
concentration
of
redox
species
and
pH
is
expected
across
the
use
area
and
time
of
application.
Table
3­
2
shows
how
redox
conditions
of
natural
waters
may
vary
in
natural
water
throughout
the
year.
The
pH
of
natural
waters
in
the
United
States
also
vary
by
region.
Generally,
acidic
waters
are
found
east
and
alkaline
waters
west
of
the
Mississippi
River.

Table
3­
2.
pH,
pE,
and
Seasonal
Variability
pH
pE
Seasonal
Variability
of
pE
<
7
Low
Summer;
Early
Fall
(
High
concentration
of
organic
species)

<
7
High
Winter;
Early
spring
>
7
Low
Summer;
Early
Fall
(
High
concentration
of
organic
species)

>
7
High
Winter;
Early
spring
Chlorate
is
used
as
a
harvest
aid.
For
most
agricultural
crops
in
the
US,
harvest
time
takes
place
in
late
Summer
to
early
Fall.
Therefore,
based
on
the
table
above,
the
conditions
at
time
of
application
are
such
that
they
would
favor
reduction
of
chlorate
(
reduce
persistence)
in
receiving
water
bodies.
At
that
time
of
the
year,
the
levels
of
dioxygen
in
natural
waters
are
low
and
organic
matter
(
mostly
from
plant
debris)
are
high.
These
two
conditions
favor
anoxic
(
reducing)
environments.
For
example,
for
cotton
grown
in
the
Mississippi
Basin
or
the
Eastern
states,
heavy
rainfall
and
high
temperatures
occur
at
that
time
of
the
year.
Assuming
that
all
chlorate
reaches
surface
water
by
runoff,
the
anoxic
conditions
would
in
principle
reduce
the
persistence
of
chlorate
in
the
receiving
water
body.
EFED
does
not
have
sufficient
information
for
all
crops
or
for
non­
food/
non­
feed
uses
to
correlate
the
timing
of
use
and
seasonal
conditions
affecting
persistence
of
chlorate
in
natural
water.

Redox
Conditions
in
Soils
If
a
pH
of
9
is
taken
as
the
upper
bound
for
a
soil
solution,
the
lower
extreme
value
of
pE
in
soil
is
­
9.
However,
a
pE
range
of
­
6
("
strongly
reduced")
to
+
12
("
strongly
oxidized")
is
more
representative.
Like
for
natural
waters,
the
redox
environment/
behavior
of
the
soil
depends
on
the
nature,
concentration,
and
pH­
pE
dependence
of
redox
species.
The
following
redox
environments
can
be
distinguished
in
soils
(
Table
3­
3).
18
The
functional
groups
included
in
Appendix
B­
1
represent
only
potential
redox
moieties.
They
may
or
may
not
be
present
in
all
soil/
natural
water
organic
matter.

19
For
example,
surface
reactions
of
some
chemical
species
dithiolates
with
semiconducting
minerals
(
e.
g.,
galena).
For
interfacial
reactions
such
as
these,
the
particle
size
distribution
of
the
mineral
phase
is
an
important
controlling
factor.
These
reactions
are
very
important
in
the
separation
of
minerals
by
froth
flotation.

30
Table
3­
3.
pE
and
Redox
Conditions
in
Soils
Medium
pE
Soil,
oxic
+
7
<
p
E
Soil,
suboxic
+
2<
p
E<
+
7
Soil,
anoxic
p
E
<
+
2
In
general,
chlorate
is
expected
to
be
less
persistent
in
anoxic
than
in
oxic
soils.

B.
Electron
Acceptors
(
Oxidizers)
and
Electron
Donors
(
Reductants)
in
Natural
Water
and
Soils
Organic
Species
In
natural
waters
and
in
soil,
organic
matter
is
present
at
percentage
amounts
and
is
likely
to
be
the
dominant
source
of
reducing
potential.
Even
though
the
actual
organic
matter
fractions
may
not
be
fully
characterized,
many
functional
groups
present
in
organic
matter
can
act
as
electron
donors
(
reductants)
or
electron
acceptors
(
oxidizers).
Appendix
B­
1
identifies
organic
functional
groups
that
are
capable
of
undergoing
redox
reactions18.
Other
factors
controlling
the
redox
chemistry
of
a
natural
environment
include
the
population
of
aerobic
and
anaerobic
microorganisms.

Inorganic
Species
Another
factor
controlling
the
redox
environment
in
soils
and
natural
water
is
the
nature
and
concentration
of
inorganic
redox
species.
Major
chemical
species
associated
with
reducing
environments
are
transition
metals
in
low
oxidation
states
(
e.
g.,
Fe(
II),
Mn(
II)),
N­
species
in
low
oxidation
states
(
NO
2
­
;
NH
4
+);
S(­
II)
(
e.
g
HS­,
S
2­;
polysulfido
species),
and
others.
Major
chemical
species
associated
with
oxidizing
environments
are
dissolved
dioxygen
(
O
2
),
transition
metals
in
high
oxidation
states
such
as
Fe(
III);
Mn(
III,
IV),
sulfate,
and
nitrate.
In
addition
to
"
straight"
redox
reactions,
many
of
the
redox
species
in
natural
waters
may
also
act
as
photosensitizers,
which
can
accelerate
the
photodegradation
of
organic
compounds.
In
addition,
many
of
the
transition
metals
may
be
present
as
mineral
phases
that
could
be
involved
in
interfacial
redox
reactions
(
i.
e.,
a
reductant
or
oxidizer
reacting
at
the
mineral
surface)
19.
31
C.
Potential
Chlorate
Reaction
Products
in
Environmental
Media
The
following
chlorine
chemical
species
(
bold
characters)
could
form
in
the
environment,
when
focusing
only
on
those
formed
by
reduction
of
chlorate
and
when
considering
thermodynamics
data
alone
(
Table3­
4).
The
source
of
the
electrons
(
e­)
can
be
any
oxidizable
moiety,
be
it
organic
matter
or
inorganic
species.
It
should
be
noted
that
in
the
environment
it
is
unlikely
that
a
single
reductant
is
present
in
the
soil
or
natural
water.
Therefore,
competitive
kinetics
in
natural
water/
soil
is
important
in
determining
which
are
the
predominant
reaction
products.
Even
if
a
reaction
product
is
thermodynamically
favored
(
i.
e.,
that
it
can
form),
it
does
not
imply
that
it
will
form.

The
chlorine
chemical
species
also
are
assessed
regarding
the
likelihood
of
their
formation
and
their
persistence
(
since
each
of
the
products
are
potent
oxidizers
themselves).
In
natural
waters
and
soils,
organic
matter
and
inorganic
species
in
soils
and
water
are
available
to
be
oxidized
by
any
of
the
reaction
products,
with
the
final
likely
redox
product
being
chloride
ion
(
Cl­).
20
Disproportionation
reactions
occur
in
when
chemical
species
of
an
element
can
exist
in
multiple
oxidation
states
(
e.
g.
the
chlorine
system).
The
disproportionation
products
are
a
chemical
species
in
a
lower
and
another
in
a
higher
oxidation
state
than
the
reactant.

32
Table
3­
4.
Reactions
Involving
Chlorate
anion.
(
The
Oxidation
State
in
Chlorate
is
V)

Redox
Half­
Cell
Name
of
the
Products
Under
environmental
conditions,
is
the
product
likely
to
.
.
.

Occur?
Persist?

1.
ClO3
­
+
6
3H2O
+
6e­
6
Cl­
+
6
OH­
Chloride;
Cl
(­
I)
Yes
Yes
2
ClO3
­
+
12
H+
+
10e­
6
Cl2
(
g)
+
6H2O
Chlorine;
Cl
(
0)
Possibly
No,
It
can
undergo
further
reactions
(
redox;
disproportionation)

3.
ClO3
­
+
2H2O
+
4e­
6
ClO­
+
4
OH­
Hypochlorite;
Cl(
I)
Possibly
No,
It
can
undergo
further
reactions
(
redox;
disproportionation)

4.
ClO3
­
+
3H+
+
3e­
6
HClO2
+
H2O
Chlorous
acid1;
Cl(
II)
Possibly
No,
It
can
undergo
further
reactions
(
redox;
disproportionation)

5.
ClO3
­
+
H2O
+
2e­
1
6
ClO2
­
+
2OH
Chlorite;
Cl
(
II)
Possibly
Possibly,
but
like
chlorate,
it
can
undergo
further
reactions
(
redox;
disproportionation)

6.
ClO3
­
+
2
H+
+
e­
6
ClO2
(
g)
+
H2O
7.
ClO3
­
+
H2O
+
e­
1
6
ClO2
(
g)
+
2OH
Chlorine
dioxide;
Cl(
IV)
Possibly
No
Chlorine
Dioxide
photoreacts
under
sunlight
8.
ClO4
­
+
2
H++
2e­
1
6
ClO3
­
+
H2O
9.
ClO4
­
+
H2O
+
2e­
1
6
ClO3
­
+
2OHPerchlorate
Cl
(
VII)
Not
Possible2
­

1
Forms
only
in
solution
(
i.
e.,
cannot
be
isolated)
2
Disproportionation
reactions20
of
chlorate
indicate
that
chlorite
and
perchlorate
(
the
highest
oxidation
state
of
chlorine)
would
be
the
reaction
products.
Even
though
formation
of
perchlorate
from
chlorate
is
a
reaction
favored
by
thermodynamics,
it
is
so
slow
(
even
at
100
°
C)
that
perchlorate
cannot
be
readily
formed.
Disproportionation
of
hypochlorite
to
yield
chlorite
is
not
thermodynamically
favored.
Therefore,
formation
of
perchlorate
from
chlorate
(
or
other
oxyanions
of
chlorine)
in
the
environment
are
not
likely
to
occur.
3
All
of
the
oxyanions
of
chlorine
are
strong
oxidizers
and,
therefore,
they
also
react
with
reductants.

These
equations
represent
only
half­
cell
reactions
(
Refer
to
Appendix
B­
1
for
their
Standard
Electrode
Potentials,
E
°
,
and
other
pertinent
information).
Although
these
chemical
species
can
21
In
the
environment,
it
is
unlikely
that
a
single
reductant
is
present
in
the
soil
or
natural
water.
Therefore,
competitive
kinetics
in
natural
water/
soil
would
important
in
determining
which
are
the
predominant
reaction
products.
Even
if
a
reaction
product
is
thermodynamically
favored
(
i.
e.,
that
it
can
form),
it
does
not
imply
that
it
will
form.

33
occur,
the
concentration
of
chlorate
as
well
as
the
nature
and
concentration
of
the
environmental
reductants
and
the
pH
of
the
media
are
also
important.
As
indicated
earlier,
very
high
variability
in
the
nature
and
concentration
of
environmental
reductants
in
soil
and
water
is
expected
throughout
the
vast
use
area
of
chlorate.
Again,
it
is
because
of
this
variability
that
the
assessment
can
only
be
made
at
a
qualitative
level.
Even
at
the
laboratory
level,
chemical
reactions
of
chlorine
species
are
extremely
complex
to
study,
particularly
their
reaction
kinetics.
Laboratory
studies
are
mainly
focused
on
reactions
with
single
reductants21.

In
summary,
the
chlorate
reduction
products
in
the
environment
are
oxyanions
of
chlorine
(
chlorite,
hypochlorite),
chlorous
acid,
and
chlorine
dioxide.
These
products
are
in
themselves
strong
oxidizers
that
can
react
in
the
environment
and
generate
products
in
lower
oxidation
states.
For
this
reason,
a
hundred
percent
conversion
of
chlorate
to
chlorite
alone
or
to
other
species
in
lower
oxidation
states
is
unlikely.
While
pH/
pE
chlorine­
species
predominance
diagrams
can
be
generated
for
aqueous
solutions
at
thermodynamic
equilibrium,
the
distribution
of
chlorine
species
in
actual
natural
waters
at
any
given
time
may
deviate
substantially
from
those
in
the
diagrams
because
natural
waters
are
not
themselves
at
equilibrium
and
very
rarely
approach
equilibrium.
(
See
Appendix
B­
1)

Based
on
thermodynamic
equilibrium
alone,
the
end
reduced
product
of
chlorate,
chlorite,
chlorous
acid,
hypochlorite,
and
chlorine
dioxide
is
chloride,
but
how
fast
all
of
these
chemical
species
convert
to
chloride
cannot
be
estimated.
22
The
EFED,
however,
has
utilize
chemical
speciation
models
to
identify
predominant
copper
species
in
aquatic
media,
but
models
exist
to
handle
speciation
of
metals
as
a
function
of
pE­
pH
(
MINTEQ).

23
For
a
definition
of
activity
and
activity
coefficients
see
Appendix
B­
1
24
20,000
m3
(
20,000,000
L)
water
volume,
2­
meter
deep
pond
with
no
outlets
34
3.2.
Exposure
3.2.1.
Aquatic
Organisms
Aquatic
Exposure
Assessment
At
the
present
time,
there
is
no
methodology
to
estimate
exposure
concentrations
in
water
for
non­
metal
inorganic
chemical
species
that
can
be
found
in
different
oxidation
states22
(
e.
g.,
for
inorganic
chemical
species
that
can
exhibit
an
extensive
pH­
pE
dependent
redox
chemistry,
such
as
the
chlorine
system).
As
an
approximation
on
the
impact
of
chlorate
on
surface
water
quality,
the
Tier
I
GENEEC­
2
simulation
model
was
used
to
estimate
exposure
concentrations
in
aquatic
systems.
Extreme
assumptions
in
the
environmental
persistence
of
chlorate
were
made
that
resulted
in
high­
end
exposure
concentrations
in
standard
ecological
pond
scenario
(
See
Table
3­
6).
The
predicted
chlorate
concentrations
are
believed
to
be
high
because
the
chemical
speciation
of
chlorate
was
not
considered
in
the
assessment.
As
discussed
in
Appendix
B­
2,
under
thermodynamic
equilibrium
conditions,
chloride
is
likely
the
predominant
species
in
natural
environments.
This
analysis,
however,
indicates
that
chlorate
can
be
reduced
to
chloride,
but
not
how
fast
the
reduction
will
occur.
Appendix
J­
2
presents
pE/
pH
predominance
and
3D
activity
fraction
diagrams
for
aqueous
chlorine­
system
species
at
thermodynamic
equilibrium23
and
it
is
an
extension
of
the
mole
fraction
computations
of
chlorine
species
mole
fractions
used
in
the
Drinking
Water
Assessment
(
D303556;
01/
05/
05).

Tier
I­
GENEEC­
2
Concentrations
in
Aquatic
Environments
Aquatic
estimated
environmental
concentrations
(
EECs)
were
calculated
using
the
GENEEC­
2
model,
which
assumes
removal
of
a
bulk
of
the
pesticide
at
one
time
from
a
10
hectare
field
into
a
1
acre
standard
ecological
pond.
24
Additional
details
on
this
model
may
be
obtained
from
the
following
url:

www.
epa.
gov/
oppefed1/
models/
water/
index.
htm
.

Agricultural
Uses
Aquatic
EECs
from
agricultural
uses
ranged
from
0.36
to
0.91
mg/
L
(
360
to
910
ug/
L)
and
are
presented
in
Table
3­
5
below.
GENEEC­
2
model
inputs
are
presented
in
Table
3­
6.
It
should
be
noted
that
there
are
no
input
parameters
that
take
into
account
the
redox
behavior
of
chlorate.
35
Therefore,
it
was
assumed
that
unchanged
chlorate
runs
off
into
surface
water,
where
it
remains
as
chlorate.

Table
3­
5.
Aquatic
EECs
of
Sodium
Chlorate
Calculated
by
GENEEC­
2
Agricultural
Uses
Maximum
Application
Rate
(
No.
Of
Applications
/
Interval)
Crops
Predicted
Peak
EEC
(
ug/
L)
a
7.5
lbs
a.
i./
Acre
(
2/
30)
Cotton
910*
*
Assuming
virtually
no
degradation
between
applications
12.5
lbs
a.
i./
Acre
Single
application
Chili
peppers;
potatoes
760
7.5
lbs
a.
i./
Acre
Single
application
Dried
beans;
corn;
cotton,
flax,
guar;
southern
peas;
safflower;
sorghum;
soybeans;
sunflower
450
6
lbs
a.
i./
Acre
Single
application
Agricultural
fallow
land;
dried
beans;
corn;
cucurbitsb,
flax,
gourds;
guar;
southern
peas;
white/
Irish
potatoes;
rice;
safflower;
sorghum;
soybeans;
sunflower,
wheat
360
a
Chronic
EECs
are
not
presented
because
no
chronic
toxicity
values
are
available
b
The
application
rate
for
cucurbits
is
6.1875
lbs
a.
i./
Acre
Table
3­
6.
Selected
Input
Parameters
Used
in
the
GENEEC­
2
Estimates
Information
Needed
by
GENEEC
Input
Parameter
Comment
Method
of
application
Maximum
application
rate
(
lbs
ai/
A)
Aerial
All
labels
allow
for
aerial
applications
for
agricultural
uses.

Kd
0
Chlorate
is
an
anion.
Thus,
it
is
expected
to
be
very
mobile
in
soils
(
high
leaching
and
runoff
potential)
In
addition,
it
has
a
very
low
potential
to
volatilize
from
soils
and
water
(
very
low
vapor
pressure
and
extremely
high
solubility
in
water)
Table
3­
6.
Selected
Input
Parameters
Used
in
the
GENEEC­
2
Estimates
Information
Needed
by
GENEEC
Input
Parameter
Comment
36
Aerobic
Soil
Metabolism
0
Persistence
in
soil
is
highly
dependent
on
type
of
soil,
pH,
other
chemical
species
present
in
soil,
soil
moisture
temperature,
precipitation
(
i.
e.
high
spatial
and
temporal
variability).
The
only
persistence
information
comes
from
a
USDA
report,
which
is
not
reported
in
terms
of
half­
lives.
Because
persistence
was
expressed
in
terms
of
"
toxic
persistence"
and
that
this
ranged
from
6
to
12
months
ad
minimum
the
half­
life
was
assumed
to
be
zero.
In
addition,
chlorate
is
a
soil
sterilant.

Aerobic
Aquatic
Metabolism
0
See
comment
under
"
Hydrolysis"

[
Direct]
Photolysis
in
Water
0
The
chlorate
anion
does
not
absorb
energy
in
the
wavelength
range
of
sunlight.
Therefore,
it
lacks
the
necessary
condition
for
a
chemical
to
undergo
direct
photolysis.
See
comment
under
"
Hydrolysis".

Hydrolysis
(
abiotic)
0
The
chlorate
anion
is
not
expected
to
react
with
water.
a
Solubility
in
water
(
mgL­
1;
ppm)
1
x
106
at
25
°
C
Chlorate
is
a
fully
ionized
salt
in
water
a
Theoretically,
it
may
be
possible
to
estimate
the
redox
potential(
s)
conditions
at
which
formation
chlorite
may
be
most
favored.
The
"
chlorine­
chlorine
anions­
oxyanions"
redox
chemistry
is
well
known.
GENEEC,
FIRST
and
SCI­
GROW
do
not
have
the
capability
to
handle
redox
data
and
to
predict
the
distribution
and
predominance
of
reduction
products
of
chlorate.
Even
EXAMS
cannot
provide
such
information.

The
behavior
of
chlorate
(
an
oxidant)
is
controlled
by
the
nature
and
concentration
of
reducing
(
i.
e.,
electron
donors)
chemical
species
in
water
and
other
environmental
media.
A
major
chemical
species
that
control
the
redox
behavior
of
chlorate
in
aqueous
media
is
the
concentration
of
nitrate.
An
important
reduced
species
of
chlorate
is
chlorite
(
ClO
2
­).
In
addition,
some
of
the
constituents
of
natural
waters
have
the
potential
to
act
as
photosensitizers
Non­
Agricultural
Uses
A
range
of
chlorate
EECs
from
its
non­
agricultural
uses
is
in
Table
3­
7.
Model
inputs
are
equivalent
to
those
in
Table
3­
6
except
that
ground,
instead
of
aerial,
application
was
modeled.
EECs
predicted
by
GENEEC­
2
ranged
from
3.1
to
39
mg/
L.
These
EECs
are
likely
very
conservative
because
the
model
assumes
that
a
contiguous
drainage
basin
flows
into
a
pond
that
is10­
times
smaller
than
the
treated
area.
The
application
scenarios
for
the
non­
agricultural
uses
may
not
be
consistent
with
the
scenario
assumed
by
GENEEC­
2.
Also,
the
environmental
fate
data
are
not
adequate
to
allow
for
further
refinement
of
aquatic
EECs
using
higher
tier
models
such
as
PRZM/
EXAMS
as
discussed
in
the
problem
formulation.
37
Table
3­
7.
Range
of
Aquatic
EECs
for
Sodium
Chlorate
Calculated
by
GENEEC­
2
(
Non­
Agricultural
Uses)

Application
Rate
Use
Predicted
Peak
EEC
(
ug/
L)
a
52
to
650
lbs
a.
i./
Acre
(
single
applications)
b
All
non­
Agricultural
uses
3,100
to
39,000
a
Chronic
EECs
are
not
reported
because
no
chronic
toxicity
values
are
available
for
comparison
b
The
application
rate
of
650
lbs
a.
i.
acre
is
only
labeled
for
pre­
paving
uses,
which
will
not
likely
result
in
exposure
to
aquatic
organisms.
The
highest
application
rate
that
would
likely
result
in
exposure
to
aquatic
organisms
is
520
lbs
a.
i./
acre.
Uses
for
this
rate
include
fence
lines,
building
perimeters,
ditch
banks,
picnic
areas,
vacant
lots,
and
cemeteries.
The
peak
EEC
for
this
application
rate
is
31,000
ug/
L.

3.2.2.
Exposure
to
Terrestrial
Organisms
­
Agricultural
Uses
ELL­
FATE
predicted
upper
90th
percentile
and
mean
chlorate
EECs
on
selected
terrestrial
animal
food
items
are
presented
in
Table
3­
8
below.
In
accordance
with
EFED
policy,
the
default
foliar
dissipation
half­
life
of
35
days
was
used
to
calculate
chlorate's
decline
in
residue
concentrations
between
applications
because
no
adequate
foliar
dissipation
half­
life
data
were
submitted.
This
only
affects
the
EEC
for
cotton
because
other
uses
were
not
modeled
using
multiple
applications.
38
Table
3­
8.
EECs
(
mg
ai/
kg­
food
item)
for
Terrestrial
Animal
Risk
Assessment
Calculated
by
ELL­
FATE
v.
1.4
Agricultural
Uses
Max.
Labeled
Application
Rate
(
No.
Of
Applications
/

Interval)
Crops
Predicted
90th
Percentile
Residue
Levels
Predicted
Mean
Residue
Levels
short
grass
tall
grass
broadleaf
forage,

small
insects
fruit,
pods,

seeds,
small
insects
short
grass
tall
grass
broadleaf
forage,

small
insects
fruit,
pods,

seeds,
small
insects
12.5
lbs
a.
i./
Acre
Single
application
Chili
peppers;
white/
Irish
potatoes
3000
1400
1700
190
1100
450
560
88
7.5
lbs
a.
i./
Acre
(
2/
30)
Cotton
2800
1300
1600
170
990
420
520
81
7.5
lbs
a.
i./
Acre
Single
application
Corn;
flax,
guar;
southern
peas;

rice;
safflower;
sorghum;

soybeans;
sunflower
1800
830
1000
110
640
270
340
53
6
lbs
a.
i./
Acre
Single
application
Agricultural
fallow
land;
dried
beans;
corn;
cucurbitsa,
flax,

gourds;
guar;
southern
peas;

white/
Irish
potatoes;
rice;

safflower;
sorghum;
soybeans;

sunflower
1400
660
810
90
510
220
270
42
a
The
application
rate
for
cucurbits
is
6.1875
lbs
a.
i./
Acre
39
3.2.3.
Terrestrial
Organisms
­
Non­
Agricultural
Uses
End­
use
products
for
the
non­
agricultural
uses
include
granule
(
broadcast
applications)
and
soluble
concentrates
(
spray
applications).
EFED
uses
different
methods
to
assesses
exposure
to
terrestrial
animals
for
each
of
these
end­
use
products.

Spray
Applications
EECs
for
the
spray
applications
were
determined
using
the
same
methods
described
for
the
agricultural
uses.
EECs
on
selected
food
items
resulting
from
application
rates
labeled
for
nonagricultural
uses
are
listed
in
Table
3­
9
below.
Only
the
highest
and
lowest
EECs
from
these
uses
are
presented.
EECs
from
all
non­
agricultural
uses
are
in
Appendix
K.

Table
3­
9.
EECs
(
mg
ai/
kg­
food
item)
for
Terrestrial
Animal
Risk
Assessment
Calculated
by
ELLFATE
v.
1.4
(
Non­
Agricultural
Uses)

Use
Application
rate
(
lbs/
Acre)
Predicted
90th
Percentile
Residue
Levels
Predicted
Mean
Residue
Levels
Short
grass
Tall
grass
Broadleaf
forage,
small
insects
Fruit,
pods,
seeds,
small
insects
Short
grass
Tall
grass
Broadleaf
forage,
small
insects
Fruit,
pods,
seeds,
small
insects
Industrial
sites
such
as
driveways,
paths,
brick
walks,
cobble
gutters,
tennis
courts
52
12500
5700
7000
780
4400
1900
2300
360
Parking
lots,
fence
lines,
building
perimeters,
ditch
banks,
picnic
areas,
vacant
lots,
wood
decks,
bleachers,
cemeteries,
fuel
tanks,
runways,
helo
pads,
etc.
520a
125,000
57,000
70,000
7800
44,000
19,000
23,000
3600
a
The
application
rate
for
pre­
paving
is
650
lbs
a.
i./
Acre;
however,
this
use
pattern
would
not
likely
result
in
exposure
to
terrestrial
organisms.
40
Granular
Applications
For
granular
applications,
estimation
of
pesticide
loading
per
unit
area
(
mg/
ft2)
was
calculated
(
Table
3­
10
below).
This
approach
is
intended
to
represent
exposure
via
multiple
routes
(
e.
g.,
incidental
ingestion
of
contaminated
soil,
dermal
contact
with
treated
seed
surfaces
and
soil
during
activities
in
the
treated
areas,
preening
activities,
and
ingestion
of
drinking
water
contaminated
with
pesticide)
and
not
just
direct
ingestion.
It
should
be
noted,
however,
that
most
of
chlorate's
exposure
will
be
via
the
oral
route
because
it
is
not
volatile
and
it
is
not
expected
to
appreciably
absorb
through
the
skin.
Although
a
bird's
or
mammal's
habitat
is
not
limited
to
a
square
foot,
there
is
presumably
a
direct
correlation
between
the
concentration
of
a
pesticide
in
the
environment
(
mg/
ft2)
and
the
chance
that
an
animal
will
be
exposed
to
a
concentration
that
could
adversely
affect
its
survival.
Further
description
of
the
mg/
ft2
index
is
in
U.
S.
EPA,
2004
and
U.
S.
EPA,
1992.
Chlorate
granules
are
applied
via
broadcast
treatment;
therefore,
EFED
assumes
that
100%
of
the
granules
are
unincorporated
for
the
exposure
assessment.
EFED
does
not
currently
assess
chronic
risk
from
long­
term
exposure
to
granules.

Table
3­
10.
Range
of
Terrestrial
EECs
(
Granular
Applications)
for
Sodium
Chlorate
Non­
Agricultural
Uses
Use
Application
Rate
(
lbs
a.
i./
Acre)
EEC
(
mg/
ft2)
a,
b
Parking
lots,
under
asphalt
paving,
fence
lines,
building
perimeters,
ditch
banks,
picnic
areas,
vacant
lots,
wood
decks,
bleachers,
cemeteries,
fuel
tanks,
runways,
helo
pads,
etc.
520
5400
Around
buildings,
storage
areas,
fences,
pumps,
machinery,
fuel
tanks,
recreational
areas,
roadways,
guard
rails,
airports,
rights
of
ways.
160
1700
a
EEC
=
Application
rate
(
lbs/
Acre)
x
453,000
mg/
lb
÷
43,600
sq
ft/
Acre
b
Only
calculations
for
the
high
and
low
extreme
application
rates
are
presented
3.2.4.
Terrestrial
Organisms,
Non­
Target
Plants
Adequate
toxicity
data
are
not
available
to
allow
for
a
characterization
of
potential
risk
to
nontarget
plants.
Therefore,
exposure
to
non­
target
plants
was
not
estimated.

3.2.5.
Uncertainties
in
the
Exposure
Assessment
A
number
of
uncertainties
were
identified
in
this
exposure
assessment:
41
Aquatic
and
Terrestrial
EECs
°
Stability
of
chlorate
in
terrestrial
and
aquatic
environments
is
uncertain,
but
it
is
expected
to
exhibit
wide
spatial
and
seasonal
variability.
Some
labels
indicate
that
chlorate
may
be
effective
as
an
herbicide
after
a
single
application
for
up
to
a
year,
which
suggests
that
there
is
potential
for
chronic
exposure.

°
As
discussed
in
the
problem
formulation
(
Section
2),
there
is
considerable
uncertainty
in
the
rate
of
formation/
decline
of
redox
products
of
chlorate
(
i.
e.,
the
kinetics
of
formation/
decline).
Although
thermodynamics
indicates
which
products
can
form
(
i.
e.,
speciation),
it
does
not
imply
that
they
will
form
and
at
what
rate.
Redox
kinetics
of
the
"
chlorine
system"
is
very
complex,
studies
are
very
difficult,
and
most
of
the
data
available
are
not
suitable
for
estimating
speciation
and
predominance
in
terrestrial
and
aquatic
environments.
GENEEC­
2
and
PRZM­
EXAMS
are
not
ideal
simulation
models
for
chemicals
in
which
one
of
the
elements
that
can
exist
in
more
than
one
oxidation
state.
Therefore,
conservative
assumptions
were
made
that
likely
resulted
in
an
over­
estimation
of
exposure
to
chlorate.
Even
simulation
models
used
in
drinking
water
chlorination
are
not
adequate
for
open
field
environments.

°
Chlorate
as
a
defoliant
on
cotton
is
used
in
the
late
summer
to
early
fall,
where
the
redox
conditions
in
water
and
soil
favor
dissipation
of
chlorate
by
reduction.
That
is,
high
temperature
and
humidity,
as
well
as
higher
reducing
conditions
of
the
media
are
such
that
chlorate
can
be
reduced
to
other
related
chemical
species.
However,
no
adequate
information
was
made
available
to
the
Agency
about
the
time
of
the
year
when
chlorate
is
used
for
other
crops
(
that
is,
the
typical
harvest
time
across
the
crop
sites).
Therefore,
it
is
uncertain
if
the
seasonal
redox
conditions
favor
dissipation
of
chlorate
for
these
crops.

Terrestrial
EECs
°
Many
of
the
non­
agricultural
uses
will
likely
result
in
small
contiguously
treated
areas,
which
would
reduce
the
likelihood
that
an
animal
would
consume
100%
of
its
diet
from
chlorate
treated
areas.

°
Inhalation
and
dermal
exposure
pathways
for
birds
and
mammals
were
not
evaluated.
Exposures
from
these
pathways
are
assumed
to
be
negligible
given
the
low
volatility
and
limited
expected
dermal
absorption
of
chlorate.

°
Because
the
herbicide
is
absorbed
by
plants
relatively
rapidly
and
kills
most
exposed
plants
within
several
days
to
several
weeks
after
exposure,
some
food
items
may
not
be
attractive
to
herbivores
for
an
extended
period
of
time
after
treatment.
25
Most
of
the
aquatic
toxicity
studies
were
previously
considered
invalid,
but
were
upgraded
based
on
the
results
of
a
confirmatory
acute
static
toxicity
study
in
daphnids.

26
http://
www.
epa.
gov/
ecotox
42
Aquatic
EECs
°
GENEEC­
2
assumes
no
foliar
interception,
which
likely
resulted
in
an
over­
estimation
of
exposure.
Foliar
interception
is
likely
to
occur
because
chlorate
absorbs
into
plants.
Any
chlorate
that
absorbs
into
the
plant
will
not
likely
enter
surface
water.

°
GENEEC­
2
assumes
a
contiguous
drainage
basin
that
flows
into
a
pond
that
is10­
times
smaller
than
the
treated
area.
The
application
scenarios
for
the
non­
agricultural
uses
may
not
be
consistent
with
the
scenario
assumed
by
GENEEC­
2.

3.3.
Ecological
Effects
Characterization
3.3.1.
Aquatic
Toxicity
Fish
Supplemental25
acute
96­
hour
flow­
through
toxicity
studies
in
bluegill
and
sheepshead
minnows
have
been
submitted
(
MRIDs
418872­
02
and
418872­
07)
and
are
summarized
in
Table
3­
11.
LC50s
from
these
studies
were
>
1000
mg/
L,
consistent
with
a
"
practically
non­
toxic"
designation.
No
effects
were
observed
in
sheepshead
minnows
or
bluegill
at
up
to
1000
mg/
L
(
nominal
concentrations).

A
supplemental
96­
hour
acute
flow­
through
study
in
rainbow
trout
was
also
submitted
(
MRID
418872­
03).
The
NOAEC
in
this
study
was
600
mg/
L
(
1/
10
rainbow
trout
died
at
1000
mg/
L).
However,
the
fish
appear
to
have
been
exposed
to
lower
concentrations
towards
the
end
of
the
study
as
indicated
by
a
reduction
in
conductivity
between
study
days
3
and
4.
Conductivity
is
directly
related
to
aqueous
chlorate
concentration.
Because
the
chlorate
concentration
associated
with
mortality
observed
in
this
study
is
uncertain,
submission
of
a
confirmatory
study
would
reduce
uncertainty
in
this
assessment.

Appendix
L
summarizes
publically
available
toxicity
data
on
chlorate
as
reported
in
EPA's
ECOTOX
database.
26
Published
acute
toxicity
data
in
fish
are
generally
consistent
with
a
"
practically
non­
toxic"
classification.
All
reported
LC50
values
are
>
1000
mg/
L
with
a
single
exception.
Woodiwiss
et
al.
(
1974)
(
summarized
in
Appendix
L)
reported
a
48­
hour
LC50
of
7.3
mg/
L
in
brown
trout
for
chlorate,
which
indicates
that
brown
trout
could
be
considerably
more
sensitive
to
chlorate
than
other
fish
species.
No
other
studies
in
brown
trout
were
located,
and
sufficient
information
was
not
available
in
the
publication
to
allow
for
an
evaluation
of
data
quality.
Also,
it
appears
that
chlorate
was
tested
in
the
presence
of
another
unspecified
flame
43
retardant.
Therefore,
it
is
uncertain
if
the
toxicity
observed
in
this
study
was
caused
by
chlorate,
the
other
unidentified
chemical,
or
a
combination
of
the
two.
Nonetheless,
these
data
could
suggest
that
there
may
be
considerable
variability
in
species
sensitivity
to
chlorate
toxicity.
Alternatively,
these
data
could
suggest
that
some
formulated
products
are
more
toxic
to
fish
because
all
chlorate
formulations
contain
fire
retardants.

No
chronic
toxicity
studies
have
been
submitted
to
the
Agency
or
were
identified
in
the
ECOTOX
database.
Chronic
toxicity
in
freshwater
and
saltwater
fish
remains
a
data
gap.

Aquatic
Invertebrates
Two
supplemental
48­
hour
studies
in
daphnids
(
MRIDs
418872­
04
and
438748­
01)
have
been
submitted
to
the
Agency.
The
EC50s
were
>
1000
mg/
L
and
920
mg/
L,
respectively
(
consistent
with
a
"
practically
non­
toxic"
designation).
In
MRID
418872­
04,
no
effects
were
observed
at
any
concentration
up
to
1000
mg/
L
(
nominal).
In
MRID
438748­
01,
the
NOAEC
was
410
mg/
L
(
55%
mortality
was
observed
at
1020
mg/
L).
This
study
was
considered
supplemental
because
the
pH
was
8.2
to
8.4,
which
is
higher
than
recommended
by
EPA
guidelines
(
7.2
­
7.6).
The
higher
pH
in
this
study
may
have
resulted
in
an
underestimation
of
toxicity
because
lower
pH
conditions
are
expected
to
promote
reduction
of
chlorate.
It
is
uncertain
if
higher
concentrations
of
more
toxic
reduction
products
such
as
chlorite
may
form
at
pH
environments
of
7.2
­
7.6
compared
with
the
pH
environments
used
in
MRID
438748­
01.
The
EC50
of
chlorite
in
a
core
study
submitted
to
the
Agency
(
MRID
940680­
09)
was
0.15
mg/
L.
Therefore,
the
higher
pH
in
this
study
may
have
resulted
in
an
underestimation
of
chlorate's
toxicity
under
some
environmental
conditions.

The
submitted
study
in
mysid
shrimp
(
MRID
418872­
06)
produced
results
that
were
consistent
with
the
results
from
the
submitted
daphnid
studies.
The
96­
hour
LC50
in
mysid
shrimp
was
>
1000
mg/
L;
2/
20
mysids
died
at
1000
mg/
L,
and
1/
20
died
at
590
mg/
L.
No
other
mortalities
or
signs
of
toxicity
were
noted
at
any
concentration
tested.
This
study
is
classified
as
supplemental
because
the
test
substance
concentrations
were
not
analytically
confirmed.
Additional
details
are
included
in
Appendix
M.

Also,
EC50s
for
Eastern
oysters
exposed
to
chlorate
via
flow
through
conditions
were
>
1000
mg/
L
(
MRID
418872­
05).
No
treatment
related
mortalities
occurred.
Shell
growth
at
250,
500,
and
1000
mg/
L
was
10%,
15%,
and
30%
lower
than
controls,
respectively.
Shell
growth
at
all
other
concentrations
was
equivalent
to
or
greater
than
controls.
Additional
details
are
included
in
Appendix
M
of
this
assessment.
This
study
is
classified
as
supplemental.

Publically
available
studies
identified
using
the
Agency's
ECOTOX
database
are
summarized
in
Appendix
L.
No
studies
were
located
that
report
toxicity
values
that
are
more
sensitive
than
the
submitted
studies
in
daphnids.
Therefore,
these
data
were
not
used
in
this
assessment.
No
chronic
studies
in
aquatic
invertebrates
have
been
submitted
to
the
Agency
or
were
identified
in
the
ECOTOX
database.
27
Key
missing
details
included
whether
the
study
conduct
followed
standard
guidelines,
whether
chlorate
concentrations
were
analytically
confirmed,
the
test
concentrations,
dose­
response
information
from
each
concentration,
water
quality
parameters
from
individual
cultures.

44
Aquatic
Plants
A
core
96­
hour
static
study
in
green
algae
(
MRID
418872­
01)
was
submitted.
The
EC50
in
this
study
was
133
mg/
L,
which
is
consistent
with
a
"
practically
non­
toxic"
designation.
The
NOAEC
was
62.5
mg/
L.
It
should
be
noted
that
green
algae
are
generally
poor
(
insensitive)
surrogates
for
aquatic
vascular
plants.
No
studies
in
the
following
plant
species
have
been
submitted,
which
are
required
for
herbicides:
Lemna
gibba
(
duckweed),
Skeletonema
costatum
(
a
marine
diatom),
Anabaena
flos­
aquae
(
a
blue­
green
bacterium),
and
a
freshwater
diatom.

Publically
available
studies
identified
using
the
Agency's
ECOTOX
database
are
summarized
in
Appendix
L.
Data
located
in
the
open
literature
suggest
that
brown
algae
may
be
considerably
more
sensitive
than
green
algae
to
chlorate.
A
14­
day
EC50
of
0.012
mM
(.
1
mg/
L)
and
NOAEC
of
<
0.005
mM
(.
0.42
mg/
L)
was
reported
for
brown
algae
(
van
Wijk
et
al.,
1997,
described
in
Appendix
M).
Sufficient
detail
was
not
available
in
the
published
study
report
to
allow
for
a
comprehensive
assessment
of
data
adequacy.
27
Nonetheless,
these
data
suggest
that
brown
algae
may
be
considerably
more
sensitive
than
green
algae
to
chlorate
toxicity.
Other
aquatic
plant
toxicity
values
identified
in
the
open
literature
were
not
more
sensitive
than
the
EC50
from
the
submitted
study
in
green
algae.
45
Table
3­
11.
Aquatic
Toxicity
Profile
for
Sodium
Chlorate
Endpoint
Environment/
Species
Toxicity
Value
Used
in
Risk
Assessment
Reference
Comment
Acute
Toxicity
to
Fish
Freshwater/
Rainbow
trout
Bluegill
LC50>
1000
mg/
L
MRID
418872­
03
Supplemental.
The
NOAEC
was
600
mg/
L
in
this
96­
hour
flow­
through
study
(
1/
10
fish
died
at
1000
mg/
L).
Based
on
conductivity
data
(
conductivity
increases
as
chlorate
concentrations
increase),
the
fish
appear
to
have
been
exposed
to
lower
concentrations
between
days
3
and
4
of
the
study,
which
may
have
resulted
in
an
underestimation
of
toxicity.
Chlorate
concentrations
were
not
analytically
confirmed.

LC50>
1000
mg/
L
MRID
418872­
02
Supplemental.
Chlorate
concentrations
were
not
analytically
confirmed.
No
effects
were
observed
at
any
concentration.

Saltwater/
Sheepshead
minnow
LC50
>
1000
mg/
L
MRID
418872­
07
Supplemental.
The
NOAEC
was
1000
mg/
L.
Test
concentrations
were
not
analytically
confirmed.

Chronic
Toxicity
to
Fish
Freshwater
No
Data
Not
applicable
No
data
are
available.
Chlorate
may
be
persistent
under
some
environmental
conditions.
Therefore,
submission
of
chronic
toxicity
data
would
reduce
uncertainty
in
this
assessment.
Saltwater
No
Data
Not
applicable
Acute
Toxicity
to
Invertebrates
Freshwater
Daphnia
magna
48­
hr
EC50:
920
mg/
L
MRIDs
438748­
01;
418872­
04
Supplemental.
In
MRID
438748­
01,
Daphnia
magna
were
tested
in
a
48­
hour
static
study.
The
NOAEC
and
LOAEC
was
410
mg/
L
and
1000
mg/
L,
respectively
(
55%
mortality
occurred
at
1000
mg/
L).
The
study
is
supplemental
because
the
pH
in
the
study
was
8.2
to
8.4,
which
is
higher
than
EPA
guidelines
(
7.2
­
7.6).
The
pH
conditions
used
may
have
resulted
in
an
underestimation
of
chlorate's
toxicity
because
some
reduction
products
of
chlorate
are
considerably
more
toxic
to
invertebrates.
In
MRID
418872­
04,
no
effects
occurred
at
up
to
1000
mg/
L.

Saltwater
Mysid
shrimp
96
hr
LC50:
>
1000
mg/
L
MRID
418872­
06
Supplemental.
The
test
concentrations
were
not
analytically
confirmed.
The
LC50
in
this
study
was
>
1000
mg/
L;
10%
(
2/
20)
mortality
occurred
at
1000
mg/
L.
Table
3­
11.
Aquatic
Toxicity
Profile
for
Sodium
Chlorate
Endpoint
Environment/
Species
Toxicity
Value
Used
in
Risk
Assessment
Reference
Comment
46
Saltwater
Eastern
oyster
EC50
>
1000
mg/
L
MRID
418872­
05
Supplemental.
Test
concentrations
were
not
analytically
confirmed
in
this
96­
hr
flowthrough
study.
A
10%,
15%,
and
30%
reduction
in
shell
growth
was
observed
at
250,
500,
and
1000
mg/
L,
respectively.

Chronic
Toxicity
to
Invertebrates
Freshwater
No
Data
Not
applicable
No
studies
were
submitted.

Saltwater
No
Data
Not
applicable
No
studies
were
submitted.

Toxicity
to
Aquatic
Plants
Freshwater
Selenastrum
capricornutum
EC50:
133
mg/
L
NOAEC:
62.5
mg/
L
MRID
418872­
01
Core.
The
NOAEC
and
LOAEC
was
62.5
and
125
mg/
L,
respectively.
No
other
aquatic
plant
toxicity
studies
have
been
submitted.
Data
in
four
other
aquatic
plant
species
are
required
for
herbicides
(
see
Table
1­
3).

Toxicity
of
Sodium
Chlorite
to
Aquatic
Organisms
Chlorite
has
been
shown
to
more
toxic
than
chlorate
to
fish
and
aquatic
invertebrates.
Scientifically
valid
chlorite
toxicity
data
that
have
been
submitted
to
and
evaluated
by
the
Agency
(
D16650)
are
summarized
below.

Acute
toxicity
to
fish
(
96­
hr
LC50s):
Rainbow
trout
(
MRID
94068007):
360
mg/
L
Bluegill
(
MRID
94068006):
420
mg/
L
Acute
toxicity
to
aquatic
invertebrates
(
48­
hr
EC50):
Daphnids
(
MRID
94068009):
0.15
mg/
L
3.3.2.
Terrestrial
Organism
Toxicity
Birds
The
data
indicate
that
chlorate
is
practically
non­
toxic
to
birds
after
acute
oral
gavage
or
subacute
dietary
exposures
(
Table
3­
12).
No
mortalities
or
signs
of
toxicity
were
observed
in
the
submitted
acute
or
subacute
toxicity
studies
in
mallard
ducks
or
bobwhite
quail
at
levels
that
exceeded
the
limit
dose
for
the
type
of
study
submitted.

No
reproduction
toxicity
studies
in
birds
have
been
submitted.
47
Mammals
Chlorate
is
practically
non­
toxic
to
mammals
after
single
oral
gavage
administration.
An
LD50
of
>
5000
mg/
kg­
bw
was
reported
in
an
acceptable
acute
oral
toxicity
study
in
rats.
In
this
study,
1/
10
animals
died
at
5000
mg/
kg­
bw.
Necropsy
findings
of
the
only
rat
that
died
during
the
study
showed
green
discoloration
of
the
intestines,
a
light
green
fluid
on
the
stomach,
pink
liquid
in
the
abdominal
cavity
and
dark
red
lung
discoloration.
No
gross
lesions
were
observed
in
the
9/
10
rats
that
survived
to
study
termination.

A
2­
generation
reproduction
toxicity
study
in
mammals
is
not
available
for
use
in
risk
assessment;
however,
multiple
subchronic
and
chronic
studies
are
available
(
Appendix
M).
EFED
does
not
use
these
types
of
studies
to
calculate
risk
quotients.
In
the
absence
of
a
2­
generation
toxicity
study,
short­
term
and
subchronic
studies
were
used
to
qualitatively
characterize
risk
to
mammals
(
data
summarized
in
Table
3­
12
below
and
further
described
in
Appendix
M).
These
studies
demonstrate
that
repeated
oral
exposures
to
chlorate
have
induced
effects
in
laboratory
animals
that
could
affect
fecundity,
growth,
or
reproductive
success
at
daily
doses
of
$
.100
mg/
kg­
bw.
Common
effects
observed
in
these
studies
include
reductions
in
growth
rate,
pituitary
and
thyroid
effects,
and
blood
toxicity.
NOAELs
from
repeated­
dose
oral
toxicity
studies
ranged
from
approximately
30
mg/
kg­
day
to
100
mg/
kg­
day.
Study
duration
ranged
from
21
days
to
90
days.
Submitted
developmental
toxicity
studies
suggest
that
chlorate
is
not
a
developmental
toxicant.

Table
3­
12.
Terrestrial
Toxicity
Profile
for
Sodium
Chlorate
Assessment
Endpoint
Species
Toxicity
Value
Used
in
Risk
Assessment
Reference
Comment
Acute
toxicity
to
birds,
LD50
Mallard
duck
>
2510
mg/
kg­
bw
MRID
421494­
01
Supplemental
study.
No
mortality
and
no
clinical
signs
of
toxicity
were
observed
in
this
study.
Treated
birds
generally
consumed
less
food
than
controls;
however,
a
clear
doseresponse
relationship
was
not
observed.
The
study
was
supplemental
because
chlorate's
purity
was
not
reported.

Subacute
toxicity
to
birds,
LC50
Mallard
and
bobwhite
>
5620
mg/
kg­
feed
(
both
species)
MRID
418199­
07
and
418199­
08
Acceptable
studies.
No
effects
were
observed
in
these
studies.

Reproductive
toxicity
to
birds
No
available
data
Acute
toxicity
to
mammals
Rat
LD50:
>
5000
mg/
kgbw
MRID
41819901
Acceptable
study.
At
5000
mg/
kg­
bw,
1/
10
animals
died.
Table
3­
12.
Terrestrial
Toxicity
Profile
for
Sodium
Chlorate
Assessment
Endpoint
Species
Toxicity
Value
Used
in
Risk
Assessment
Reference
Comment
48
Reproductive
Toxicity
in
Mammals
Sufficient
data
not
available
None
used
Not
applicable
A
2­
generation
toxicity
study
is
not
available.
Developmental
toxicity
studies
(
MRID
40460401;
NTP,
2002)
suggest
that
chlorate
is
not
a
developmental
toxicant
(
summarized
in
Appendix
M).

Chronic
toxicity
to
mammals
Rat
None
used
MRID
40444801;
MRID
40460402;
McCauley
et
al,
1995;
Kurokawa
et
al,
1985;
Heywood
et
al,
1972
NTP,
1999
Commonly
reported
toxic
effects
include
blood
toxicity,
thyroid
effects
(
hypertrophy
and
thyroid
hormone
level
changes),
pituitary
toxicity,
and
body
weight
reduction
(
See
Appendix
M).
NOAELs
ranged
from
approximately
30
mg/
kg­
day
to
100
mg/
kg­
day.

Terrestrial
Plants
Tier
I
studies
were
submitted
to
the
Agency
that
showed
an
application
of
348
lbs
a.
i./
Acre
was
toxic
to
monocots
and
dicots.
These
studies
are
summarized
below
and
are
further
described
in
Appendix
M.
Effects
of
a
single
application
of
chlorate
at
348
lbs
a.
i./
Acre
was
evaluated
in
10
plant
species.
In
the
vegetive
vigor
study,
almost
all
plants
were
dead
by
11
days
(
all
species).
Phytotoxic
effects
included
chlorosis,
necrosis
and
stunting.
Cucumber
exhibited
the
greatest
reduction
for
a
dicot,
with
95.4%
mean
fresh
weight
inhibition
and
sorghum
exhibited
the
greatest
reduction
for
a
monocot,
with
83.1%
mean
fresh
weight
inhibition.
The
EC
25
and
NOAEC
were
<
348
lbs
a.
i./
A
for
all
test
species.

In
the
seed
germination
and
seedling
emergence
studies,
an
increase
in
the
number
of
plants
that
failed
to
germinate
compared
with
controls
for
all
test
species
was
observed
compared
to
the
controls
by
Day
5.
The
348
lbs
a.
i./
A
treatment
group
percent
inhibitions
exceeded
25%
for
the
mean
fresh
weights
of
all
test
species.
Phytotoxic
effects
included
chlorosis,
necrosis,
stunting,
and
distortion.
Cucumber
exhibited
the
greatest
reduction
for
a
dicot,
with
98%
mean
fresh
weight
inhibition,
and
corn
exhibited
the
greatest
reduction
for
a
monocot,
with
90%
mean
fresh
weight
inhibition.
The
EC
25
and
NOAEC
for
this
study
were
<
348
lb
a.
i./
A
for
all
test
species.

Although
these
Tier
I
studies
were
adequately
conducted,
the
data
do
not
allow
for
derivation
of
EC25,
EC05,
or
NOAEC
values,
precluding
their
use
in
quantitative
risk
assessment.
28
Data
were
taken
from
EFED's
science
chapter
for
reregistration
eligibility
decision
for
sodium
chlorite
(
D16650,
1993)
and
from
U.
S.
EPA's
Drinking
Water
Health
Advisory
for
chlorine
dioxide,
chlorite
and
chlorate
(
1996).

49
Toxicity
of
Chlorite
to
Terrestrial
Organisms
Chlorite
has
been
shown
to
more
toxic
to
mammals
and
birds
than
chlorate.
Chlorite
toxicity
data
that
have
been
submitted
to
and
evaluated
and
considered
valid
by
the
Agency
are
summarized
below.

Acute
toxicity
to
birds
(
LD50):
Bobwhite
quail
(
MRID
254177):
467
mg/
kg­
bw
Subacute
toxicity
to
birds
(
LC50):
Bobwhite
quail
(
MRID
94068008):
>
5000
mg/
kg­
diet
Subacute
toxicity
to
birds
(
LC50):
Mallard
duck
(
MRID
94068005):
>
5000
mg/
kg­
diet
Acute
toxicity
to
mammals
(
LD50):
105­
136
mg/
kg­
bw26
Chronic
toxicity
to
mammals
(
NOAEC
from
a
2­
generation
toxicity
study
in
rats):
70
mg/
kg­
diet28
3.3.3.
Incident
Data
Review
A
review
of
the
EIIS
database
for
ecological
incidents
involving
chlorate
was
completed
on
October
25,
2004.
There
were
no
chlorate
incidents
in
the
database.

4.
Risk
Characterization
4.1.
Aquatic
Organisms
Summary
of
Conclusions
°
Risk
(
acute
exposure)
to
fish
is
presumably
lower
than
the
Agency's
level
of
concern
for
all
labeled
chlorate
uses.

°
No
acute
risk
to
aquatic
invertebrates
was
identified
at
levels
of
concern
to
the
Agency
from
exposure
to
chlorate;
however,
formation
of
chlorite
could
result
in
risk
to
aquatic
invertebrates
at
levels
of
concern
to
the
Agency.
These
potential
risks
cannot
be
quantified.

°
No
toxicity
data
are
available
to
allow
for
characterization
of
potential
risk
to
aquatic
organisms
from
chronic
exposures.

4.1.1.
Fish,
Freshwater
and
Saltwater
Risk
Estimation
Formal
risk
quotients
were
not
calculated
for
fish
because
the
proximity
of
the
LC50
to
the
highest
concentration
tested
(
1000
mg/
L)
could
not
be
estimated.
However,
1000
mg/
L
was
considered
a
toxic
concentration
to
fish
because
it
induced
10%
mortality
in
rainbow
trout
29
50
(
418872­
03).
29
Table
4­
1
below
presents
ratios
of
chlorate's
EECs
to
the
toxic
concentration
of
1000
mg/
L.
Because
these
values
are
not
LC50s,
which
are
the
toxicity
values
usually
used
to
derive
risk
quotients,
they
can
be
used
to
estimate
high­
end
risk
to
exposed
fish.

Table
4­
1.
Proximity
of
Chlorate's
EECs
to
the
Toxic
Concentration
of
1000
mg/
L
in
Fish
(
Agricultural
and
Non­
Agricultural
Uses)

Use
Highest
EEC
Toxic
Concentrationa
Ratio
of
EEC
to
the
Toxic
Concentration
All
agricultural
uses
#
0.91
mg/
L
1000
mg/
L
<
0.01
All
non­
Agricultural
#
39
mg/
L
1000
mg/
L
#
0.039
a
LC50s
are
from
supplemental
studies
in
bluegill,
rainbow
trout,
and
sheepshead
minnows.
No
evidence
of
toxicity
was
observed
at
up
to
1000
mg/
L
in
bluegill
or
sheepshead
minnows;
10%
mortality
was
observed
in
rainbow
trout
(
418872­
03)
at
1000
mg/
L.
Therefore,
1000
mg/
L
was
considered
to
represent
a
potentially
toxic
concentration
to
some
fish
species.
The
proximity
of
the
LC50
to
1000
mg/
L
is
uncertain.
However,
the
conductivity
data
suggest
that
fish
exposed
at
the
nominal
concentration
of
1000
mg/
L
may
have
been
exposed
to
lower
concentrations
(
see
Section
3
for
details).

Risk
Description
­
Interpretation
of
Direct
Effects
All
EECs
were
more
than
20­
fold
lower
than
the
toxic
concentration
observed
in
fish
of
1000
mg/
L
(
all
risk
quotients
would
be
<
0.05).
Therefore,
the
currently
labeled
chlorate
uses
presumably
do
not
pose
risk
at
levels
of
concern
to
the
Agency
from
agricultural
or
nonagricultural
uses.
Uncertainties
in
this
assessment
are
discussed
in
Section
4.1.4.

4.1.2.
Aquatic
Invertebrates
Risk
Estimation
Risk
quotients
based
on
an
EC50
from
a
supplemental
48­
hour
acute
toxicity
study
in
daphnids
and
EECs
calculated
by
GENEEC­
2
are
presented
in
Table
4­
2
below.
Formal
risk
quotients
were
not
calculated
for
saltwater
invertebrates
because
the
proximity
of
the
LC50
from
a
supplemental
96­
hr
study
(
MRID
438748­
01)
to
the
highest
concentration
tested
(
1000
mg/
L)
could
not
be
estimated.
However,
1000
mg/
L
was
considered
a
toxic
concentration
to
the
surrogate
saltwater
invertebrate
mysid
shrimp
because
it
induced
10%
mortality
at
that
concentration.
Table
4­
3
below
presents
ratios
of
chlorate's
EECs
to
the
toxic
concentration
of
1000
mg/
L.
51
Table
4­
2.
Acute
Freshwater
Aquatic
Invertebrate
Risk
Quotients
Agricultural
and
Non­
Agricultural
Uses
of
Sodium
Chlorate
Use
Application
Rate
Maximum
EEC
EC50a
RQ
LOC
Exceedance
Agricultural
uses
All
labeled
rates
#
0.91
mg/
L
920
mg/
L
<
0.01
No
LOC
exceeded
<
0.01
No
LOC
exceeded
Nonagricultural
uses
All
labeled
rates
#
39
mg/
L
920
mg/
L
#
0.041
No
LOC
exceeded
<
0.039
No
LOC
exceeded
a
The
freshwater
invertebrate
EC50
used
in
this
analysis
was
based
on
a
supplemental
acute
48­
hour
study
in
daphnids
(
438748­
01);
55%
mortality
occurred
at
1000
mg/
L.

Table
4­
3.
Proximity
of
Chlorate's
EECs
to
the
Toxic
Concentration
of
1000
mg/
L
in
Saltwater
Invertebrates
Agricultural
and
Non­
Agricultural
Uses
of
Sodium
Chlorate
Use
Application
Rate
Maximum
EEC
Toxic
Concentrationa
Ratio
of
EEC
to
the
Toxic
Concentration
Agricultural
uses
All
labeled
rates
#
0.91
mg/
L
Saltwater:
>
1000
mg/
La
<
0.01
<
0.01
Non­
agricultural
uses
All
labeled
rates
#
39
mg/
L
Saltwater:
>
1000
mg/
La
#
0.041
<
0.039
a
The
saltwater
invertebrate
LC50
was
>
1000
mg/
L;
10%
(
2/
20)
mortality
at
1000
mg/
L
(
MRID
418872­
06).

Risk
Description
­
Interpretation
of
Direct
Effects
For
chlorate's
agricultural
and
non­
agricultural
uses,
the
acute
risk
quotients
for
freshwater
aquatic
invertebrates
indicate
that
there
is
no
risk
that
exceed
the
Agency's
level
of
concern.
The
data
also
suggest
that
there
is
no
risk
to
saltwater
invertebrates
at
the
Agency's
level
of
concern
from
any
of
chlorate's
labeled
uses.
Uncertainties
in
this
assessment
are
discussed
in
Section
4.1.4.

4.1.3.
Aquatic
Plants
Risk
Estimation
Risk
quotients
based
on
a
vascular
plant
EC50
of
133
mg/
L
and
a
NOAEC
of
62.5
mg/
L
and
EECs
calculated
by
GENEEC­
2
are
in
Table
4­
4
and
Table
4­
5
below.
30
Key
missing
details
included
whether
the
study
conduct
followed
standard
guidelines,
whether
chlorate
concentrations
were
analytically
confirmed,
the
test
concentrations,
dose­
response
information
from
each
concentration,
and
water
quality
parameters
from
individual
cultures.

52
Table
4­
4.
Non­
Endangered
Species
Algal
Risk
Quotients
Agricultural
and
Non­
Agricultural
Uses
Use
Application
Rate
Maximum
Peak
EEC
EC50
or
LC50
RQ
LOC
Exceedance
Agricultural
uses
All
labeled
rates
#
0.9
mg/
L
133
mg/
L
<
0.01
No
LOC
exceeded
Non­
Agricultural
All
labeled
rates
#
39
mg/
L
133
mg/
L
#
0.29
No
LOC
exceeded
Table
4­
5.
Endangered
Species
Algal
Risk
Quotients
Agricultural
and
Non­
Agricultural
Uses
Use
Application
Rate
Maximum
Peak
EECa
NOAEC
RQ
LOC
Exceedance
Agricultural
uses
All
labeled
rates
#
0.9
mg/
L
62.5
mg/
L
#
0.014
No
LOC
exceeded
Non­
Agricultural
All
labeled
rates
#
39
mg/
L
62.5
mg/
L
#
0.62
No
LOC
exceeded
Risk
Description
­
Interpretation
of
Direct
Effects
No
LOCs
were
exceeded
from
chlorate's
agricultural
or
non­
agricultural
uses.
Also,
the
NOAEC
from
the
green
algae
study
was
62.5
mg/
L,
which
is
lower
than
the
peak
chlorate
EEC
of
39
mg/
L.
Therefore,
risk
to
endangered
species
is
also
presumably
lower
than
the
Agency's
level
of
concern.
However,
risk
to
algae
cannot
be
precluded.
No
studies
in
the
following
plant
species
have
been
submitted,
which
are
required
for
herbicides:
Lemna
gibba
(
duckweed),
Skeletonema
costatum
(
a
marine
diatom),
Anabaena
flos­
aquae
(
a
blue­
green
bacterium),
and
a
freshwater
diatom.

Also,
data
located
in
the
open
literature
suggest
that
brown
algae
are
considerably
more
sensitive
than
green
algae
to
chlorate.
A
14­
day
EC50
of
0.012
mM
(.
1
mg/
L)
was
reported
for
brown
algae
(
van
Wijk
et
al.,
1997,
described
in
Appendix
M).
Sufficient
detail
was
not
available
in
the
published
study
report
to
allow
for
a
comprehensive
assessment
of
data
adequacy.
30
However,
the
EECs
for
the
non­
agricultural
uses
ranged
from
3.1
to
39
mg/
L,
which
all
exceed
the
reported
EC50
for
brown
algae
of
.1
mg/
L.
For
this
reason,
there
may
be
risk
to
some
algal
species
that
exceed
the
Agency's
level
of
concern
for
aquatic
plants.
As
previously
discussed,
however,
additional
data
are
needed
to
address
the
considerable
uncertainty
in
the
aquatic
EECs
and
uncertainty
in
the
toxicity
data
before
risk
can
be
definitively
assessed.
53
4.1.4.
Uncertainties
in
the
Aquatic
Organism
Risk
Assessment
There
are
a
number
of
areas
of
uncertainty
in
the
aquatic
organism
risk
assessment
that
merit
discussion.
These
include
the
following:

Uncertainties
that
may
have
caused
an
under­
estimation
of
risk
°
The
risk
assessment
only
considers
the
most
sensitive
species
tested.
Aquatic
acute
and
chronic
risks
are
based
on
acceptable
toxicity
data
for
the
most
sensitive
fish,
invertebrate,
and
plant
species
tested.
Responses
to
a
toxicant
can
be
expected
to
be
variable
across
species.
Sensitivity
differences
between
species
can
be
considerable
(
several
orders
of
magnitude)
for
some
chemicals
(
Mayer
and
Ellersieck
1986).
It
is
uncertain
if
the
tested
laboratory
species
is
representative
of
most
species'
sensitivities
to
chlorate
toxicity.

Open
literature
toxicity
data
were
located
that
suggest
that
some
fish
and
algal
species
may
be
more
sensitive
to
chlorate
toxicity
than
the
surrogate
species
used
in
this
assessment.
Therefore,
submission
of
confirmatory
studies
in
non­
guideline
fish
and
algal
species
would
reduce
uncertainty
in
this
assessment
(
see
Section
3
for
additional
discussion).

°
The
risk
assessment
only
considered
a
subset
of
possible
use
scenarios.
Although
chlorate
has
a
label
for
a
limited
number
of
crops
and
non­
agricultural
uses,
they
encompass
a
large
geographic
area.
Also,
the
non­
agricultural
uses
may
presumably
be
used
without
geographic
limits.
Some
uses
that
may
pose
higher
risks
include
those
occurring
in
sensitive
locations
(
close
proximity
to
aquatic
environments
and
high
runoff
potentials).

°
The
risk
quotients
assume
that
exposure
only
occurs
to
chlorate.
In
some
environments,
chlorate
may
be
reduced
to
chlorite,
which
has
been
shown
to
be
more
toxic
to
aquatic
organisms
than
chlorate.
This
is
of
particular
concern
for
invertebrates
because
the
chlorite
EC50
for
daphnids
is
0.15
mg/
L,
which
is
approximately
6000­
fold
lower
than
the
EC50
for
chlorate
of
920
mg/
L.
Therefore,
formation
of
even
small
amounts
of
chlorite
could
result
risk
to
endangered
and
non­
endangered
aquatic
invertebrates
at
levels
of
concern
to
the
agency.

°
The
effect
of
pH
on
chlorate
toxicity
is
uncertain.
The
available
toxicity
studies
used
pH
environments
that
are
slightly
alkaline.
The
toxicity
of
chlorate
is
expected
to
be
dependent
on
pH
as
well
as
redox
condition.
Therefore,
submission
of
data
that
characterizes
the
effect
of
pH
and
redox
condition
of
the
media
on
chlorate
toxicity
to
invertebrates
would
be
of
considerable
value
to
this
assessment,
provided
that
the
chemical
species
in
the
test
media
are
adequately
characterized
(
qualitatively
and
quantitatively).
Submission
of
such
chlorate
in
toxicity
studies
for
aquatic
invertebrates
would
reduce
uncertainty
in
this
assessment
because
pH
conditions
as
low
as
5.5
are
not
uncommon,
particularly
in
the
Northeastern
United
States.
54
°
Many
of
the
labels
do
not
specify
the
maximum
number
of
applications
or
annual
load;
however,
some
labels
for
cotton
indicate
that
multiple
applications
may
be
necessary.
The
Agency
has
assumed
that
chlorate
may
be
applied
twice
annually
to
cotton
at
all
application
rates
with
a
30­
day
application
interval
and
is
applied
once
annually
for
all
other
uses.
This
assumption
may
have
resulted
in
an
under­
estimation
of
risk
if
chlorate
may
be
applied
more
than
twice
annually
(
or
at
shorter
application
intervals)
to
cotton
or
more
than
once
annually
to
other
crops.

Uncertainties
that
may
have
resulted
in
an
over­
estimation
of
risk
°
As
previously
discussed,
there
is
considerable
uncertainty
in
the
rate
of
formation/
decline
of
redox
products
of
chlorate
(
i.
e.,
the
kinetics
of
formation/
decline).
Redox
kinetics
of
the
chlorine
system
is
complex,
studies
are
very
difficult,
and
most
of
the
data
available
are
not
suitable
for
estimating
speciation
and
predominance
in
terrestrial
and
aquatic
environments.
GENEEC­
2
and
PRZM­
EXAMS
are
not
ideal
simulation
models
for
chemicals
in
which
one
of
the
elements
that
can
exist
in
more
than
one
oxidation
state.
Therefore,
conservative
assumptions
were
made
that
likely
resulted
in
an
over­
estimation
of
exposure
to
chlorate.

°
GENEEC­
2
assumes
a
contiguous
drainage
basin
that
flows
into
a
pond
that
is10­
times
smaller
than
the
treated
area.
The
application
scenarios
for
the
non­
agricultural
uses
may
not
be
consistent
with
the
scenario
assumed
by
GENEEC­
2.

°
GENEEC­
2
assumes
no
foliar
interception,
which
likely
resulted
in
an
over­
estimation
of
exposure.
Foliar
interception
is
likely
to
occur
because
chlorate
absorbs
into
plants.
Any
chlorate
that
absorbs
into
the
plant
will
not
likely
enter
surface
water.

Uncertainties
that
may
have
resulted
in
an
under­
estimation
or
an
over­
estimation
of
risk
°
Surrogate
species
were
used
to
predict
potential
risks
for
species
with
no
data
(
i.
e.,
reptiles
and
amphibians).
It
was
assumed
that
use
of
surrogate
species
toxicity
data
are
sufficiently
conservative
to
apply
the
broad
range
of
species
within
taxonomic
groups.
If
other
species
are
more
or
less
sensitive
to
chlorate
and
its
degradates
than
the
surrogates,
risks
may
be
under­
or
over­
estimated,
respectively.
31
The
application
rate
for
pre­
paving
is
650
lbs
a.
i./
Acre;
however,
this
use
pattern
would
not
likely
result
in
exposure
to
birds.

55
4.2.
Risks
to
Birds,
Acute
and
Chronic
Exposures
Summary
of
Conclusions
°
Agricultural
Uses:
Based
on
chlorate's
low
acute
and
subacute
toxicity
to
birds
(
LD50
>
2510
mg/
kg­
bw;
LC50
>
5620
mg/
kg­
feed),
risk
to
endangered
and
non­
endangered
birds
is
presumably
lower
than
the
Agency's
level
of
concern
for
all
agricultural
uses.

°
Non­
agricultural
Uses:
Even
though
chorate
is
of
low
acute
toxicity
to
birds,
EECs
for
chlorate's
non­
agricultural
uses
were
as
high
as
125,000
ppm.
Therefore,
acute
risk
to
birds
cannot
be
precluded.
However,
such
risks
cannot
be
quantified.

°
Absence
of
reproduction
toxicity
data
precludes
a
quantitative
assessment
of
chronic
risk
to
birds.
However,
mammalian
data
suggest
that
chlorate's
effects
are
cumulative
(
more
toxic
after
repeated
exposures).
Therefore,
the
Agency
presumes
that
potential
risk
to
birds
exists.

4.2.1.
Risk
Estimation
­
Integration
of
Exposure
and
Effects
Data
Acute
risk
quotients
were
not
calculated
because
no
mortality
or
signs
of
toxicity
were
observed
in
the
submitted
subacute
or
acute
toxicity
studies
at
concentrations
that
are
above
the
limit
for
these
types
of
studies.

Chronic
risk
quotients
were
not
calculated
because
a
reproduction
toxicity
study
has
not
been
submitted
to
the
Agency.

4.2.2.
Risk
Description
­
Interpretation
of
Direct
Effects
No
acute
risk
to
birds
was
identified
at
levels
of
concern
to
the
Agency
from
chlorate's
agricultural
uses
based
on
its
low
acute
toxicity
to
birds.
However,
EFED
cannot
preclude
acute
risk
from
the
non­
agricultural
uses.
Chlorate
is
applied
at
rates
of
52
to
520
lbs/
Acre
for
these
uses.
31
The
corresponding
EECs
are
12,500
and
125,000
ppm,
respectively,
which
are
approximately
2.5
to
25­
fold
higher
than
the
highest
concentration
tested
in
the
subacute
bird
toxicity
studies.
Therefore,
acute
risk
to
birds
from
these
high
application
rates
cannot
be
precluded.

EFED
cannot
preclude
chronic
risk
because
no
reproduction
toxicity
data
are
available.
A
field
dissipation
study
has
not
been
submitted;
therefore,
the
potential
for
chronic
exposure
has
not
been
fully
assessed.
However,
chlorate
is
expected
to
be
persistent
under
some
environmental
conditions;
therefore,
the
Agency
assumes
that
repeated
exposure
is
possible.
The
available
56
studies
in
mammals
suggest
that
chlorate
is
significantly
more
toxic
after
repeated
exposures
compared
with
single
exposures
(
i.
e.,
toxicity
increases
as
study
duration
increases).
A
similar
relationship
between
exposure
duration
and
toxicity
is
presumed
in
birds
as
well.
Therefore,
lack
of
reproduction
toxicity
data
is
an
important
data
gap.

4.3.
Risk
to
Mammals,
Acute
Exposures
Summary
of
Conclusions
°
Risk
from
acute
exposure
cannot
be
precluded
for
chlorate's
agricultural
or
non­
agricultural
uses.

°
A
2­
generation
reproduction
toxicity
study
is
not
available
to
allow
for
derivation
of
chronic
risk
quotients,
and
other
studies
were
considered
inappropriate
for
risk
quotient
calculations.
However,
based
on
subchronic
toxicity
studies,
there
appears
to
be
risk
to
mammals
at
levels
of
concern
to
the
Agency
from
both
agricultural
and
non­
agricultural
uses.

4.3.1.
Risk
Estimation,
Integration
of
Exposure
and
Effects
Data
Acute
risk
quotients
were
not
calculated
for
mammals.
The
LD50
from
a
core
acute
oral
toxicity
study
in
rats
was
>
5000
mg/
kg­
bw
(
MRID
418199­
01).
In
this
study,
10%
(
1/
10)
of
the
rats
administered
5000
mg/
kg
died.
Mortality
was
not
observed
at
any
other
dose.
Therefore,
the
data
were
not
sufficient
to
allow
for
characterization
of
the
dose­
response
relationship,
and
the
proximity
of
the
LD50
to
5000
mg/
kg­
bw
is
uncertain.
For
this
reason,
formal
risk
quotients
were
not
calculated.
However,
Tables
4­
6
and
4­
7
below,
respectively,
present
a
comparison
of
the
body
weight
adjusted
LD50s
to
the
agricultural
and
non­
agricultural
EECs.
These
ratios
can
be
used
to
estimate
high­
end
risk
to
exposed
mammals.
57
Table
4­
6.
Proximity
of
the
lowest
observed
acute
toxic
dose
in
mammals
to
the
upper
90th
percentile
EEC
(
mg/
kg­
bw)
for
small
(
15­
gram),
medium
(
35­
gram),
and
large
(
1000­
gram)
mammals
(
Range
of
Maximum
Application
Rate
for
all
Agricultural
Uses).

Food
Item
Size
of
Mammal
(
grams)
Adjusted
lowest
observed
toxic
dose
from
MRID
41819901
(
mg/
kg­
bw)
a
Range
of
EECs
(
mg/
kg­
bw)
b
Ratio
of
lowest
observed
toxic
dose
to
the
upper
90th
percentile
EEC
(
unitless)

Short
grass
15
10,989
1400
­
2900
0.13
­
0.26
35
8891
950
­
2000
0.11
­
0.22
1000
3846
200
­
450
0.052
­
0.12
Tall
grass
15
10,989
630
­
1300
0.057
­
0.12
35
8891
440
­
910
0.049
­
0.10
1000
3846
99
­
210
0.026
­
0.055
Broadleaf
plants/
small
insects
15
10,989
770
­
1600
0.070
­
0.15
35
8891
540
­
1100
0.061
­
0.12
1000
3846
120
­
250
0.031
­
0.065
Fruits,
pods,
large
insects
15
10989
86
­
180
<
0.01
­
0.016
35
8891
59
­
120
<
0.01
­
0.013
1000
3846
14
­
28
<
0.01
­
<
0.01
a
The
acute
oral
toxic
dose
was
adjusted
for
body
weight
based
on
the
formula
recommended
by
Mineau
et
al.
1996:
Adj.
LD50
=
LD50
(
TW/
AW)
0.25
:
TW=
weight
of
test
organism
(
reference
body
weight
of
adult
rat
is
.350
grams);
AW
=
weight
of
assessed
organism.
b
EECs
were
calculated
by
assuming
that
small,
medium,
and
large
mammals
consume
95%,
66%,
and
15%
of
their
body
weight
daily.
Only
the
highest
and
lowest
EECs
from
chlorate's
agricultural
uses
are
used
in
this
assessment.
These
values
are
based
on
EECs
presented
in
Table
3­
8.
58
Table
4­
7.
Proximity
of
the
lowest
observed
acute
toxic
dose
in
mammals
to
the
predicted
EEC
(
mg/
kg­
bw)
for
small
(
15­
gram),
medium
(
35­
gram),
and
large
(
1000­
gram)
mammals
(
Based
on
the
Range
of
Maximum
Application
Rates
for
all
Non­
Agricultural
Uses).

Food
Item
Size
of
Mammal
(
weight,
grams)
Adjusted
lowest
observed
toxic
dose
(
mg/
kg­
bw)
a
Range
of
EECs
(
mg/
kg­
bw)
b
Ratio
of
lowest
observed
toxic
dose
to
the
upper
90th
percentile
EEC
(
unitless)

Short
grass
15
10989
11,900
­
119,000
1.1
­
11
35
8891
8200
­
82,000
0.93
­
9.3
1000
3846
1900
­
19,000
0.49
­
4.9
Tall
grass
15
10989
5400
­
54,000
0.49
­
4.9
35
8891
3800
­
38,000
0.43
­
4.3
1000
3846
860
­
8600
0.22
­
2.2
Broadleaf
plants/
small
insects
15
10989
6700
­
67,000
0.61
­
6.1
35
8891
4600
­
46,000
0.52
­
5.2
1000
3846
1100
­
11,000
0.27
­
2.7
Fruits,
pods,
large
insects
15
10989
740
­
7400
0.07
­
0.7
35
8891
520
­
5200
0.06
­
0.6
1000
3846
120
­
1200
0.03
­
0.3
a
The
acute
oral
toxic
dose
was
adjusted
for
body
weight
based
on
the
formula
recommended
by
Mineau
et
al.
1996
for
adjusting
LD50s:
Adj.
LD50
=
LD50
(
TW/
AW)
0.25
:
TW=
weight
of
test
organism
(
reference
body
weight
of
adult
rat
is
350
grams);
AW
=
weight
of
assessed
organism.
b
EECs
were
calculated
by
assuming
that
small,
medium,
and
large
mammals
consume
95%,
66%,
and
15%,
respectively,
of
their
body
weight
daily,
and
were
calculated
using
the
highest
and
lowest
labeled
application
rates
(
52
lbs
a.
i./
Acre
and
520
lbs
a.
i./
Acre)
that
are
most
likely
to
result
in
exposure.

4.3.2.
Risk
Description
­
Interpretation
of
Direct
Effects
Agricultural
Uses
For
chlorate's
agricultural
uses,
the
ratio
of
the
lowest
body
weight
adjusted
observed
toxic
dose
in
mammals
(
5000
mg/
kg­
bw)
to
the
upper
90th
percentile
EEC
was
as
high
as
0.26
for
small
32Campbell
G
S.
1985.
Soil
Physics
with
BASIC.
Developments
in
Soil
Science
14.
Elsevier
publishers.
New
York
NY,
USA.
This
soil
density
is
considered
a
representative,
mid­
range
value.

33
650
lbs
a.
i./
Acre
×
0.37
kg/
lb
=
240.5
kg
a.
i./
Acre
×
1E6
mg/
kg
=
2.4E8
mg
a.
i./
Acre
1.2E8
cm3/
Acre
x
1.3
g
soil/
cm3
=
1.6
E8
g
soil/
Acre
(
1.6E5
kg
soil/
Acre)
2.4E8
mg
a.
i./
Acre
÷
1.6E5
kg
soil/
Acre
=
1500
mg
a.
i./
kg­
soil
59
mammals,
0.22
for
medium
sized
mammals,
and
0.12
for
large
mammals
(
short
grass
food
items).
For
other
food
items,
the
ratios
were
#
0.15.
If
the
LD50
is
in
close
proximity
to
5000
mg/
kgday
there
may
be
potential
risk
at
levels
of
concern
to
the
Agency
to
non­
endangered
small
and
medium
sized
mammals
that
forage
on
short
grass
and
potential
risk
to
large
(
1000
grams)
endangered
mammals
that
feed
on
short
grass
and
small
and
medium­
sized
endangered
mammals
that
forage
on
several
other
food
items.
However,
proximity
of
the
LD50
to
5000
mg/
kg­
day
cannot
be
determined
based
on
the
submitted
data.
Additional
uncertainties
in
this
assessment
are
discussed
in
Section
4.7.

Non­
Agricultural
Uses,
Spray
Applications
The
ratios
presented
in
Table
4­
7
above
suggest
that
there
could
be
considerable
risk
to
mammals
of
all
sizes
that
forage
in
the
area
where
chlorate
is
used
for
the
non­
agricultural
applications.
However,
potential
risk
was
likely
over­
estimated
for
the
following
reasons:

°
An
LD50
has
not
been
established.
The
highest
dose
tested
in
the
available
toxicity
studies
(
5000
mg/
kg­
bw)
induced
10%
mortality.
The
proximity
of
the
LD50
to
5000
mg/
kg­
bw
is
uncertain.
°
Many
of
the
non­
agricultural
uses
will
likely
result
in
small
contiguously
treated
areas.
Therefore,
the
likelihood
that
an
animal
will
consume
100%
of
its
diet
from
chlorate
treated
areas
is
low
for
some
of
these
uses.

Nonetheless,
the
EECs
were
predicted
to
be
up
to
11
times
higher
than
the
toxic
dose
of
5000
mg/
kg­
bw
for
the
non­
agricultural
uses.
Therefore,
there
appears
to
be
risk
to
mammals
at
levels
of
concern
to
the
Agency.

Also,
based
on
the
very
high
application
rates
associated
with
the
non­
agricultural
uses
of
chlorate,
ingestion
of
contaminated
soil
could
represent
a
significant
exposure
pathway.
Therefore,
incidental
ingestion
via
contaminated
soil
was
estimated.
Based
on
a
maximum
application
rate
of
650
lbs
a.
i./
Acre
and
a
soil
density
of
1.3
grams/
cm3
(
Campbell
1985),
32
chlorate
concentrations
in
the
first
3
centimeters
of
soil
could
be
as
high
as
1500
mg/
kg­
soil
(
ppm).
33
This
application
rate
is
only
labeled
for
pre­
paving,
which
is
not
likely
to
result
in
exposure.
Also,
this
calculation
assumes
no
foliar
interception
(
direct
application
to
soil).
For
these
reasons,
this
calculation
represents
a
high­
end
estimate.
Using
daily
food
intake,
as
estimated
by
Nagy
(
1987)
(
EQ
1),
a
20­
gram
mammal
is
estimated
to
consume
approximately
3.7
grams
of
food
(
wet
weight)
daily:
34
Extrapolations
from
one
mammal
species
to
another
needs
to
consider
differences
in
the
scaling
of
toxicity
for
differences
in
body
weight.
Therefore,
the
acute
oral
LD50
was
adjusted
for
body
weight
based
on
the
formula
recommended
by
Mineau
et
al.
1996:
Adj.
LD50
=
LD50
(
TW/
AW)
0.25
:
TW=
weight
of
test
organism
(
reference
body
weight
of
adult
rat
is
.350
grams);
AW
=
weight
of
assessed
organism.

60
F
BW
W
=
 
0
621
1
0
564
.
*

(
)
.

where
F
is
the
food
intake
in
grams
of
fresh
weight
per
day,
BW
is
the
body
mass
(
wet
weight)
of
the
organism
in
grams,
and
W
is
the
mass
fraction
of
water
in
the
food
(
assumed
to
be
0.1).
Therefore,
the
estimated
dose
of
chlorate
from
dietary
consumption
of
100%
soil
would
be
5.6
mg/
day
(
3.7
g
soil
day­
1
×
0.001
kg
g­
1
×
1500
mg
a.
i.
kg­
1).
This
intake
level
corresponds
to
a
body
weight
adjusted
internal
dose
of
280
mg/
kg­
day
for
a
20­
gram
mammal
(
5.6
mg/
day
÷
0.02
kg
=
280
mg/
kg­
day).
Direct
comparison
of
this
maximum
possible
soil
intake
value
to
the
body
weight
adjusted
acute
oral
LD50
of
>
10,989
mg/
kg­
bw34
would
not
result
in
risk
to
mammals
at
levels
of
concern
to
the
Agency.

In
addition,
Beyer
et
al.
(
1994)
reported
that
high­
end
mammals
with
respect
to
soil
consumption
(
e.
g.,
armadillos)
consume
#
17%
soil
in
their
diet,
and
small
mammals
(
mice
and
voles)
consume
less
than
2.5%
soil
in
their
diet.
Therefore,
this
analysis
likely
resulted
in
an
over­
estimation
of
exposure
and
risk.
However,
risk
from
repeated
ingestion
of
contaminated
soil
cannot
be
precluded,
because
adequate
toxicity
data
are
not
available
for
comparison
to
these
exposure
values.

Non­
Agricultural
Uses,
Granular
Applications
Risk
Estimation
Formal
risk
quotients
were
not
calculated
for
reasons
previously
discussed.
However,
Table
4­
8
below
presents
a
comparison
of
the
body
weight
adjusted
lowest
observed
toxic
dose
in
rats
of
5000
mg/
kg­
day
from
MRID
41819901
to
the
granular
application
EECs
(
mg/
ft2).
These
ratios
are
used
to
qualitatively
describe
potential
risk.
61
Table
4­
8.
Range
of
Ratios
of
Chlorate's
Body
Weight
Adjusted
LD50
to
Granular
EECs
(
mg/
ft2)
for
Sodium
Chlorate's
Non­
Agricultural
Uses
(
Granular
Formulations)

Use
Body
Weight
(
g)
Rat
LD50Adj
mg/
kg­
bwa
EEC
(
mg/
ft2)
b
Ratio
of
LD50adj
to
EECc
Parking
lots,
under
asphalt
paving,
fence
lines,
building
perimeters,
ditch
banks,
picnic
areas,
vacant
lots,
wood
decks,
bleachers,
cemeteries,
fuel
tanks,
runways,
helo
pads,
etc.
520
lbs
a.
i./
Acre
15
10,989
5400
33
35
8891
5400
17
1000
3846
5400
1.4
Around
buildings,
storage
areas,
fences,
pumps,
machinery,
fuel
tanks,
recreational
areas,
roadways,
guard
rails,
airports,
rights
of
ways.
160
lbs
a.
i./
Acre
15
10,989
1700
10
35
8891
1700
5.4
1000
3846
1700
0.43
a
Adj.
LD50
=
LD50
(
TW/
AW)
0.25
:
TW=
weight
of
test
organism
(
reference
body
weight
of
adult
rat
is
.350
grams);
AW
=
weight
of
assessed
organism.
b
EEC
=
Application
rate
(
lbs/
Acre)
x
453,000
mg/
lb
÷
43,600
sq
ft/
Acre
c
Ratio
=
EEC
÷
(
LD50adj
×
bw
in
kg)

Risk
Description
Granular
applications
of
chlorate
appear
to
pose
risk
to
small,
medium,
and
large
mammals
at
levels
of
concern
to
the
Agency.
It
was
estimated
that
granular
applications
would
result
in
chlorate
concentrations
that
are
between
0.42­
and
33­
times
the
mass
of
chlorate
in
every
ft2
of
chlorate­
treated
areas
that
has
been
shown
to
be
toxic
to
mammals.
Although
the
habitat
and
feeding
area
of
mammals
are
substantially
greater
than
a
ft2,
the
mg/
ft2
index
is
used
to
evaluate
whether
there
is
sufficient
mass
of
chlorate
within
a
treated
area
to
potentially
cause
adverse
effects
to
exposed
mammals.
U.
S.
EPA
1992
and
U.
S.
EPA
2004
can
be
referenced
for
additional
discussion
on
the
LD50/
ft2
index.

The
LD50/
ft2
method
is
used
to
encompass
exposure
via
all
routes
(
oral,
dermal,
inhalation).
However,
as
an
ionic
salt,
chlorate
will
not
likely
appreciably
absorb
through
the
skin,
and
its
low
Henry's
law
constant
and
volatility
suggest
that
inhalation
will
likely
be
negligible.
Therefore,
exposure
will
likely
be
limited
largely
to
the
oral
route
(
drinking
water,
contaminated
food
items,
direct
consumption
of
granules,
preening
activity).
Although
chlorate
is
a
strong
oxidant,
it
is
not
a
strong
irritant;
therefore,
mammals
are
not
expected
to
intentionally
avoid
chlorate.
In
fact,
chlorate
could
be
particularly
attractive
to
salt­
thirsty
mammals
resulting
in
higher
chlorate
body
burdens
in
these
mammals.

Other
uncertainties
in
this
assessment
are
presented
in
Section
4.7.
62
4.4.
Potential
Risk
to
Mammals,
Chronic
Exposures
Sufficient
toxicity
data
are
not
available
to
allow
for
risk
quotient
calculations.
However,
the
available
subchronic
data
suggest
that
mammals
may
be
at
considerable
risk
from
repeated
exposures
to
chlorate.
Chlorate
is
presumably
stable
under
some
environmental
conditions;
therefore,
repeated
exposures
to
chlorate
is
possible.
Subchronic
toxicity
studies
ranging
in
duration
from
21
to
90
days
suggest
that
chlorate
may
induce
effects
that
could
affect
the
growth,
survival,
or
reproduction
in
exposed
mammals
at
doses
of
approximately
100
mg/
kg­
bw
per
day,
which
is
a
dose
that
is
50
times
lower
than
the
acute
oral
LD50
of
>
5000
mg/
kg­
bw.
Effects
observed
in
the
repeated­
dose
toxicity
studies
included
decreased
body
weight
(
up
to
approximately
30%
decrease
compared
with
control
(
unexposed)
animals),
blood
toxicity,
and
pituitary
and
thyroid
effects
(
including
changes
in
hormone
levels).

4.5.
Endocrine
Disruption
Potential
Effects
observed
in
repeated­
dose
toxicity
studies
in
mammals
indicate
that
chlorate
could
affect
the
endocrine
system.
For
example,
thyroid
hormone
levels
were
affected
in
rats
maintained
on
drinking
water
supplemented
with
chlorate
for
90
days.

EPA
is
required
under
the
Federal
Food,
Drug,
and
Cosmetic
Act
(
FFDCA),
as
amended
by
the
Food
Quality
Protection
Act
(
FQPA),
to
develop
a
screening
program
to
determine
whether
certain
substances
(
including
all
pesticide
active
and
other
ingredients)
"
may
have
an
effect
in
humans
that
is
similar
to
an
effect
produced
by
a
naturally
occurring
estrogen,
or
other
such
endocrine
effects
as
the
Administrator
may
designate."
Following
the
recommendations
of
its
Endocrine
Disruptor
Screening
and
Testing
Advisory
Committee
(
EDSTAC),
EPA
determined
that
there
was
scientific
bases
for
including,
as
part
of
the
program,
the
androgen
and
thyroid
hormone
systems,
in
addition
to
the
estrogen
hormone
system.
EPA
also
adopted
EDSTAC's
recommendation
that
the
Program
include
evaluations
of
potential
effects
in
wildlife.
For
pesticide
chemicals,
EPA
will
use
The
Federal
Insecticide,
Fungicide,
and
Rodenticide
Act
(
FIFRA)
and,
to
the
extent
that
effects
in
wildlife
may
help
determine
whether
a
substance
may
have
an
effect
in
humans,
FFDCA
authority
to
require
the
wildlife
evaluations.
As
the
science
develops
and
resources
allow,
screening
of
additional
hormone
systems
may
be
added
to
the
Endocrine
Disruptor
Screening
Program
(
EDSP).
When
the
appropriate
screening
and/
or
testing
protocols
being
considered
under
the
Agency's
EDSP
have
been
developed,
chlorate
may
be
subjected
to
additional
screening
and/
or
testing
to
better
characterize
effects
related
to
endocrine
disruption.

4.6.
Potential
Risk
to
Terrestrial
Plants
Based
on
chlorate's
non­
selective
mode
of
action
and
lack
of
adequate
toxicity
data,
EFED
presumes
risk
to
non­
target
plants
at
levels
above
the
Agency's
level
of
concern
for
all
uses.
However,
such
risks
cannot
be
quantified
based
on
the
currently
available
data.
63
4.7.
Uncertainties
in
the
Terrestrial
Organism
Risk
Assessment
There
are
a
number
of
areas
of
uncertainty
in
the
terrestrial
risk
assessment
that
merit
discussion,
which
were
previously
discussed
in
Sections
2
and
3.
These
are
summarized
below.

Exposure
°
Many
of
the
labels
are
not
clear
regarding
the
maximum
allowable
annual
applications
(
number
of
applications
or
total
load).
The
Agency
assumed
a
maximum
of
2
annual
applications
(
30­
days
apart)
for
cotton
and
1
annual
application
for
all
other
uses.
Risk
may
be
under­
estimated
if
these
assumptions
do
not
accurately
reflect
chlorate's
applications.

°
Stability
of
chlorate
in
terrestrial
and
aquatic
environments
is
uncertain,
but
it
is
expected
to
exhibit
wide
spatial
and
seasonal
variability.

°
There
is
considerable
uncertainty
in
the
rate
of
formation/
decline
of
redox
products
of
chlorate
(
i.
e.,
the
kinetics
of
formation/
decline).

°
Many
of
the
non­
agricultural
uses
will
likely
result
in
small
contiguously
treated
areas,
which
would
reduce
the
likelihood
that
an
animal
would
consume
100%
of
its
diet
from
chlorate
treated
areas.

°
Chlorate
is
a
dessicant
that
kills
parts
of
plants
that
are
generally
edible
to
herbivorous
organisms.
Because
the
herbicide
is
absorbed
by
plants
relatively
rapidly
and
kills
most
exposed
plants
within
several
days
to
several
weeks
after
exposure,
some
contaminated
food
items
may
not
be
attractive
to
herbivores
for
an
extended
period
of
time
after
treatment.

°
The
risk
assessment
assumes
that
100%
of
the
exposure
organism's
diet
is
relegated
to
single
food
types
foraged
only
from
treated
fields.
These
assumptions
are
likely
to
be
conservative
for
many
species
and
will
tend
to
overestimate
potential
risks.
The
assumption
of
100%
diet
from
a
treated
area
may
be
realistic
for
acute
exposures,
but
long­
term
exposures
modeled
as
single
food
types
composed
entirely
of
material
from
a
treated
field
is
uncertain.

Toxicity
°
The
toxicity
database
is
limited.
No
chronic
or
reproductive
toxicity
data
(
aquatic
or
terrestrial
organisms)
considered
adequate
for
screening
level
ecological
risk
assessment
were
available.

°
Adequate
non­
target
terrestrial
plant
data
are
not
available
for
this
assessment.
In
the
absence
of
such
data,
and
based
on
the
non­
specific
mode
of
action
of
chlorate,
EFED
presumes
considerable
risk
to
non­
target
plants.
35
Hayes,
Wayland
J.,
Jr.
Pesticides
Studied
in
Man.
Baltimore/
London:
Williams
and
Wilkins,
1982..

64
°
None
of
the
submitted
acute
toxicity
studies
in
rats,
mysid
shrimp,
or
fish
produced
toxicity
at
or
above
the
LD50
or
LC50
(<
50%
of
tested
organisms
were
affected
by
exposure)
resulting
in
an
over­
estimation
of
risk.
The
available
data
from
these
studies
do
not
allow
for
an
approximation
of
the
highest
dose
or
concentration
tested
to
the
LD50
or
LC50.
Therefore,
the
magnitude
of
the
over­
estimation
of
risk
on
the
risk
assessment
from
using
these
toxicity
values
is
uncertain.

°
An
LD50
of
1200
mg/
kg­
day
in
rats
has
been
reported
in
secondary
sources.
35
However,
this
study
report
has
not
been
obtained
and
evaluated
by
the
Agency.
If
these
data
are
reliable,
then
risks
characterized
in
this
assessment
may
have
been
under­
estimated.

Scope
of
Assessment
°
Surrogate
organisms
were
used
to
predict
potential
risks
for
species
with
no
data
(
i.
e.,
reptiles
and
amphibians).

°
The
risk
assessment
only
considers
the
most
sensitive
species
tested.
Terrestrial
acute
and
chronic
risks
are
based
on
toxicity
data
for
the
most
sensitive
bird,
mammal,
and
plant
species
tested.
Responses
to
a
toxicant
can
be
expected
to
be
variable
across
species.
The
position
of
the
tested
species
relative
to
the
distribution
of
all
species'
sensitivities
to
chlorate
is
unknown.

°
Sodium
Chlorate
is
formulated
with
other
active
ingredients
and
with
flame
retardants.
Potential
effects
that
these
other
chemicals
may
have
on
chlorate's
fate
or
toxicity
is
not
considered
in
this
assessment.
The
effects
of
prolonged,
year­
after­
year
use
of
chlorate
in
the
same
field
is
not
known,
particularly
in
semiarid
sites
that
require
irrigation
(
e.
g.,
Arizona,
California),
where
there
is
a
potential
for
salt
build­
up
over
time.

4.8.
Potential
Risk
to
Threatened
and/
or
Endangered
Species
4.8.1.
Aquatic
Organisms
There
are
no
geographical
limitations
on
the
non­
agricultural
chlorate
uses;
therefore,
the
Agency
assumes
that
there
is
considerable
potential
for
exposure
to
endangered
aquatic
species.
No
chronic
toxicity
data
are
available
in
freshwater
or
saltwater
fish
or
invertebrates;
therefore,
chronic
risk
to
these
surrogate
organisms
cannot
be
precluded.
Although
levels
of
concern
were
not
exceeded,
potential
risk
to
listed
fish,
aquatic
invertebrates,
or
aquatic
plants
cannot
be
precluded
for
the
following
reasons:
36
The
48­
hour
acute
EC50
in
daphnids
is
0.15
mg/
L
(
MRID
940680­
09).

65
°
Fish.
The
data
located
in
the
open
literature
suggest
that
brown
trout
could
be
considerably
more
sensitive
than
other
fish
species
that
have
been
tested.
Woodiwiss
et
al.
(
1974)
(
summarized
in
Appendix
M)
reported
a
48­
hour
LC50
of
7.3
mg/
L
in
brown
trout
for
chlorate.
No
other
studies
in
brown
trout
were
located,
and
sufficient
information
was
not
available
in
the
publication
to
allow
for
an
evaluation
of
data
quality.
However,
this
LC50
would
trigger
endangered
species
concerns
for
all
chlorate
agricultural
and
non­
agricultural
uses.
Also,
it
appears
that
chlorate
was
tested
in
the
presence
of
another
unspecified
flame
retardant
in
this
study.
Therefore,
it
is
uncertain
if
the
toxicity
observed
in
this
study
was
caused
by
chlorate,
the
other
unidentified
chemical,
or
a
combination
of
the
two.
Nonetheless,
these
data
could
suggest
that
there
may
be
considerable
variability
in
species
sensitivity
to
chlorate
toxicity.
Alternatively,
these
data
could
suggest
that
formulated
products
are
more
toxic
to
fish
because
all
chlorate
formulations
contain
fire
retardants.

°
Aquatic
Invertebrates.
Chlorite
could
form
from
the
reduction
of
chlorate
in
the
environment.
Chlorite
is
6000­
fold
more
toxic
than
chlorate
to
daphnids.
36
However,
the
currently
available
data
do
not
allow
for
a
realistic
estimation
of
the
amount
of
chlorite
that
may
form
in
the
environment.
Therefore,
submission
of
data
that
characterize
the
potential
for
chlorate
to
be
reduced
to
chlorite
in
natural
waters
would
be
of
considerable
value
to
this
assessment.

°
Aquatic
Plants.
The
data
located
in
the
open
literature
suggest
that
brown
algae
are
considerably
more
sensitive
than
green
algae
to
chlorate.
A
14­
day
EC50
of
0.012
mM
(.
1
mg/
L)
was
reported
for
brown
algae
(
van
Wijk
et
al.,
1997).
The
EECs
for
the
nonagricultural
uses
ranged
from
3.1
to
39
mg/
L,
which
exceed
the
EC50
for
brown
algae
of
.1
mg/
L.
Therefore,
there
may
be
risk
to
some
algal
species
that
exceeds
the
Agency's
level
of
concern
for
aquatic
plants.
As
previously
discussed,
however,
additional
data
are
needed
to
address
the
considerable
uncertainty
in
the
aquatic
EECs
before
risk
can
be
definitively
characterized.
Also,
no
studies
in
the
following
plant
species
have
been
submitted,
which
are
required
for
herbicides:
Lemna
gibba
(
duckweed),
Skeletonema
costatum
(
a
marine
diatom),
Anabaena
flos­
aquae
(
a
blue­
green
bacterium),
and
a
freshwater
diatom..

Uncertainties
in
this
assessment
are
equivalent
to
those
presented
in
Section
4.1.4.
Listed
species
that
reside
in
areas
where
chlorate
may
be
used
were
not
located
because
its
uses
have
no
geographical
restrictions.
For
example,
rights­
of­
ways
and
airport
fields
are
located
in
virtually
every
county
in
the
United
States.
Therefore,
the
Agency
presumes
that
there
is
considerable
potential
for
exposure
to
chlorate
by
listed
species.

4.8.2.
Terrestrial
Organisms
Potential
Risk
to
Endangered
Birds
66
No
effects
were
observed
in
subacute
dietary
studies
in
mallard
ducks
or
bobwhite
quail
at
up
to
5620
mg/
kg­
diet.
However,
acute
risk
to
endangered
birds
cannot
be
precluded
for
chlorate's
non­
agricultural
uses
because
the
EECs
were
significantly
higher
(
up
to
125,000
mg/
kg­
food
item)
than
the
highest
concentration
tested
in
subacute
dietary
toxicity
studies.

No
reproduction
toxicity
data
are
available
to
allow
for
an
estimation
of
risk
from
chronic
exposures
to
chlorate.
However,
mammalian
toxicity
data
indicate
that
chlorate
is
more
toxic
after
repeated
exposures.
The
Agency
presumes
that
chlorate
is
also
more
toxic
to
birds
after
repeated
exposures.
Therefore,
chronic
risk
to
birds
cannot
be
precluded.

Potential
Acute
Risk
to
Endangered
Mammals
For
chlorate's
agricultural
uses,
the
ratio
of
the
lowest
observed
toxic
dose
to
mammals
(
5000
mg/
kg­
bw)
to
the
upper
90th
percentile
EEC
was
as
high
as
0.26
for
small
mammals,
0.22
for
medium
sized
mammals,
and
0.12
for
large
mammals
(
short
grass
food
items).
For
other
food
items,
the
ratios
were
#
0.15.
If
the
LD50
is
in
close
proximity
to
5000
mg/
kg­
day,
there
may
be
risk
at
levels
of
concern
to
the
Agency
to
endangered
small,
medium,
and
large
mammals
that
forage
on
short
grass
and
risk
to
small
and
medium
sized
endangered
mammals
that
forage
on
several
other
food
items.

There
appears
to
be
considerable
potential
acute
risk
to
endangered
mammals
of
all
sizes
that
forage
in
the
area
where
chlorate
is
used
for
the
non­
agricultural
applications.
The
EECs
were
up
to
11
times
higher
than
the
toxic
dose
of
5000
mg/
kg­
bw
for
the
non­
agricultural
uses.
Therefore,
there
appears
to
be
risk
to
mammals
at
levels
of
concern
to
the
Agency.

A
number
of
uncertainties
were
noted
in
this
assessment,
which
have
previously
been
described
in
detail
and
are
summarized
in
Section
4.7.

Potential
Chronic
Risk
to
Endangered
Birds
and
Mammals
No
chronic
toxicity
data
have
been
submitted
to
the
Agency
or
are
available
in
the
open
literature
for
any
surrogate
species
used
in
this
assessment;
therefore,
risk
cannot
be
precluded
for
any
species
assessed.
The
available
studies
in
mammals
suggest
that
chlorate
is
significantly
more
toxic
after
repeated
exposures
compared
with
single
exposures
(
i.
e.,
toxicity
increases
as
study
duration
increases).
A
similar
relationship
between
exposure
duration
and
toxicity
is
presumed
in
birds
as
well.
Based
on
the
expected
persistence
of
chlorate
under
some
environmental
conditions
and
the
demonstrated
cumulative
toxicity
observed
in
mammals,
risk
to
endangered
birds
and
mammals
is
presumed
to
exceed
the
Agency's
level
of
concern.

The
Agency
presumes
that
there
is
potential
for
exposure
to
a
large
number
and
large
variety
of
endangered
species
because
these
uses
would
presumably
encompass
every
county
in
the
United
States.
Therefore,
states
or
counties
with
endangered
species
that
reside
in
areas
that
may
be
treated
with
chlorate
were
not
identified
as
part
of
this
screening
level
assessment.
67
Potential
Risk
to
Endangered
Terrestrial
Plants
Sufficient
toxicity
data
have
not
been
submitted
to
the
Agency
to
allow
for
a
characterization
of
potential
risk
to
terrestrial
plants.
Based
on
chlorate's
non­
selective
toxicity
to
plants,
the
Agency
presumes
that
there
is
risk
to
endangered
plants
at
levels
of
concern
to
the
Agency
from
the
use
of
chlorate
on
agricultural
and
non­
agricultural
areas.

Critical
Habitat
In
the
evaluation
of
pesticide
effects
on
designated
critical
habitat,
consideration
is
given
to
the
physical
and
biological
features
(
constituent
elements)
of
a
critical
habitat
identified
by
the
U.
S
Fish
and
Wildlife
and
National
Marine
Fisheries
Services
as
essential
to
the
conservation
of
a
listed
species
and
which
may
require
special
management
considerations
or
protection.
The
evaluation
of
impacts
for
a
screening
level
pesticide
risk
assessment
focuses
on
the
biological
features
that
are
constituent
elements
and
is
accomplished
using
the
screening­
level
taxonomic
analysis
(
risk
quotients,
RQs)
and
listed
species
levels
of
concern
(
LOCs)
that
are
used
to
evaluate
direct
and
indirect
effects
to
listed
organisms.

The
screening­
level
risk
assessment
has
identified
potential
concerns
for
indirect
effects
on
listed
species
for
those
organisms
dependant
upon
species
at
risk
from
chlorate
exposure.
Considerable
uncertainty
in
the
potential
for
direct
effects
to
listed
species
from
chlorate's
use
identified
in
this
assessment
precludes
a
meaningful
analysis
of
the
potential
of
indirect
effects
to
listed
species.
In
light
of
the
potential
for
indirect
effects,
the
next
step
for
EPA
and
the
Service(
s)
is
to
identify
which
listed
species
and
critical
habitat
are
potentially
implicated.
Analytically,
the
identification
of
such
species
and
critical
habitat
can
occur
in
either
of
two
ways.
First,
the
agencies
could
determine
whether
the
action
area
overlaps
critical
habitat
or
the
occupied
range
of
any
listed
species.
If
so,
EPA
would
examine
whether
the
pesticide's
potential
impacts
on
non­
endangered
species
would
affect
the
listed
species
indirectly
or
directly
affect
a
constituent
element
of
the
critical
habitat.
Alternatively,
the
agencies
could
determine
which
listed
species
depend
on
biological
resources,
or
have
constituent
elements
that
fall
into,
the
taxa
that
may
be
directly
or
indirectly
impacted
by
the
pesticide.
Then
EPA
would
determine
whether
use
of
the
pesticide
overlaps
the
critical
habitat
or
the
occupied
range
of
those
listed
species.
At
present,
the
information
reviewed
by
EPA
does
not
permit
use
of
either
analytical
approach
to
make
a
definitive
identification
of
species
that
are
potentially
impacted
indirectly
or
critical
habitats
that
is
potentially
impacted
directly
by
the
use
of
the
pesticide.
EPA
and
the
Service(
s)
are
working
together
to
conduct
the
necessary
analysis.

This
screening­
level
risk
assessment
for
critical
habitat
provides
a
listing
of
potential
biological
features
that,
if
they
are
constituent
elements
of
one
or
more
critical
habitats,
would
be
of
potential
concern.
These
correspond
to
the
taxa
identified
above
as
being
of
potential
concern
for
indirect
effects.
This
list
should
serve
as
an
initial
step
in
problem
formulation
for
further
assessment
of
critical
habitat
impacts
outlined
above,
should
additional
work
be
necessary.
68
5.
References
Fletcher,
J.
S.,
J.
E.
Nellsen,
and
T.
G.
Pfleeger.
1994.
Literature
review
and
evaluation
of
the
EPA
food­
chain
(
Kenaga)
nomogram,
an
instrument
for
estimating
pesticide
residues
on
plants.
Env.
Toxicol.
Chem.
13:
1381­
1391.

Heywood
R,
Sortwell
RJ,
Kelly
PJ,
Street
AE.
Toxicity
of
sodium
chlorate
to
the
dog.
Vet
Rec.
1972.
90(
15):
416­
8.

Hoerger,
F.
and
E.
E.
Kenaga.
1972.
Pesticide
residues
on
plants:
correlation
of
representative
data
as
a
basis
for
estimation
of
their
magnitude
in
the
environment.
in:
F.
Coulston
and
F.
Corte
(
editors),
Environmental
Quality
and
Safety:
Chemistry,
Toxicology,
and
Technology.
Vol
I.
Georg
Thieme
Publishers,
Stuttgart,
West
Germany,
pp.
9­
28.

Kurokawa
Y,
et
al.
1985.
Lack
of
promoting
effect
of
potassium
chlorate
and
sodium
chlorate
in
two­
stage
rat
renal
carcinogenesis.
Journal
of
the
American
College
of
Toxicology.
4(
6):
331­
337.

McCauley
P.
T.,
Robinson
M.,
Daniel
F.
B.,
Olson
G.
R.
The
effects
of
subchronic
chlorate
exposure
in
Sprague­
Dawley
rats.
Drug
Chem
Toxicol.
1995
18(
2­
3):
185­
99.

National
Toxicology
Program
(
NTP).
1999.
Toxicology
and
Carcinogenesis
Studies
of
Sodium
Chlorate
(
CAS
No.
7775­
09­
9)
in
F344/
N
Rats
and
B6C3F1
Mice
(
Drinking
Water
Studies).
TR517.
Abstract
available
on­
line
at
http://
ntp.
niehs.
nih.
gov.

U.
S.
EPA.
1992.
Comparative
analysis
of
acute
avian
risk
from
granular
pesticides.
Office
of
Pesticide
Programs.
Washington
DC.
March,
1992.

U.
S.
EPA.
2000.
Wildlife
Exposure
Factors
Handbook.
Office
of
Research
and
Development,
Washington,
D.
C.
EPA/
600/
R­
93/
187.
December
1993.

U.
S.
EPA.
2004.
Overview
of
the
Ecological
Risk
Assessment
Process
in
the
Office
of
Pesticide
Programs,
U.
S.
Environmental
Protection
Agency.
Office
of
Prevention,
Pesticides
and
Toxic
Substances.
Office
of
Pesticide
Programs.
Washington,
D.
C.
January
23,
2004.
Sodium
Chlorate
Appendices
­
1
Appendices
Environmental
Fate
and
Ecological
Risk
Assessment
for
the
Reregistration
of
Sodium
Chlorate
as
an
Active
Ingredient
in
Terrestrial
Food/
Feed
and
Non­
food/
Non­
feed
Uses
Sodium
Chlorate
Appendices
­
2
Appendix
A.
Status
of
Data
Requirements
for
Sodium
Chlorate
37
Photoreactions
induced
by
transfer
of
energy
from
photosensitizers
in
natural
water
and
soils
may
contribute
to
the
transformation
of
chlorate
in
the
environment
(
that
is,
indirect
photolysis
contribution).
Many
chemical
reductants
present
in
natural
environments
may
also
behave
as
photoreductants.

Sodium
Chlorate
Appendices
­
3
Table
A­
1.
Status
of
Data
Requirements
for
Sodium
Chlorate
(
Food/
Feed
and
Non­
food/
Non­
feed
Uses.
(
Waivers:
EFGWB
DPBarcode
D186156,
03/
15/
93;
Transmittal
Memo
to
SRRD
05/
05/
93)

Data
Requirement
Status
Comment
Environmental
Fate
Data
161­
1
Abiotic
Hydrolysis
Waived
The
chemistry
of
chlorate
in
water
is
dominated
by
redox
reactions
that
require
the
presence
of
reductants
(
inorganic
and/
or
organic).
Because
the
161­
1
Hydrolysis
study
is
conducted
in
abiotic
media
and
in
types
of
buffer
solutions
that
are
not
likely
to
act
as
reductants,
this
study
was
waived
as
it
was
concluded
that
the
study
was
not
going
provide
any
useful
or
very
limited
information,
unless
known
environmental
reductants
were
included
in
the
aqueous
media.
Moreover,
the
redox
chemistry
of
chlorate
in
water
is
extensively
documented
in
the
chemical
literature.

161­
2
Direct
Photolysis
in
Water
Waived
The
161­
2
study
is
conducted
in
the
absence
of
chemical
photosensitizers.
That
is,
this
study
is
designed
to
address
the
role
of
direct
photolysis
in
aqueous
media.
A
necessary,
but
not
sufficient,
condition
for
direct
photolysis
in
environmentally
significant
aqueous
media
is
that
the
chemical
must
absorb
energy
(
photon)
in
the
sunlight
wavelength
range.
Chlorate
does
not
absorb
energy
in
this
range.
Therefore,
the
161­
2
study
was
waived
because
it
does
not
the
necessary
condition
for
direct
photolysis.
37.

161­
3
Photolysis
on
Soil
Waived
The
161­
2
study
is
conducted
in
the
absence
of
chemical
photosensitizers.
That
is,
this
study
is
designed
to
address
the
role
of
direct
photolysis
in
aqueous
media.
A
necessary,
but
not
sufficient,
condition
for
direct
photolysis
in
environmentally
significant
aqueous
media
is
that
the
chemical
must
absorb
energy
(
photon)
in
the
sunlight
wavelength
range.
Chlorate
does
not
absorb
energy
in
this
range.
Therefore,
the
161­
2
study
was
waived
because
it
does
not
the
necessary
condition
for
direct
photolysis..
Data
Requirement
Status
Comment
38
Although
laboratory
studies
conducted
on
soils
could,
in
principle,
provide
useful
information
on
the
persistence
of
chlorate
on
soil,
there
is
a
major
drawback
and
concern
in
the
case
of
chlorate
because
sodium
chlorate
can
react
violently
with
organic
material
and
cause
fire.
Therefore,
performing
these
studies
is
not
recommended.

The
persistence
of
chlorate
in
the
field
remains
an
issue
and
an
uncertainty.
While
there
are
claims
that
it
could
persist
as
long
as
5
years,
there
are
no
actual
data
to
support
this
claim.
Use
of
sodium
chlorate
as
a
desiccant/
defoliant
requires
that
it
is
used
in
conjunction
with
a
fire
retardant.
Thus,
how
the
fire
retardant
influences
the
persistence
of
chlorate
in
the
field
is
unknown.
Therefore,
a
field
study
is
recommended
according
to
agree
upon
protocols.
Terrestrial
field
dissipation
studies
must
be
conducted
with
a
typical
end­
use
product
formulation.

Sodium
Chlorate
Appendices
­
4
162­
1
Aerobic
Soil
Metabolism38
Waived
This
study,
if
conducted
according
to
existing
guidelines,
would
not
likely
produce
useful
information
due
to
sodium
chlorate
antimicrobial
properties
that
can
destroy
the
microbial
populations
in
soil.
If
the
microbial
population
is
destroyed,
the
study
cannot
adequately
address
the
role
of
microorganisms
in
the
degradation
of
chlorate.
It
is
more
likely
that
the
nature
and
concentration
of
redox
species
control
the
chemistry
of
chlorate
in
soils
162­
2
Anaerobic
Soil
Metabolism
Waived
This
study,
if
conducted
according
to
existing
guidelines,
would
not
likely
produce
useful
information
due
to
sodium
chlorate
antimicrobial
properties
that
can
destroy
the
microbial
populations
in
soil.
If
the
microbial
population
is
destroyed,
the
study
cannot
adequately
address
the
role
of
microorganisms
in
the
degradation
of
chlorate.
It
is
more
likely
that
the
nature
and
concentration
of
redox
species
control
the
chemistry
of
chlorate
in
soils
162­
3
Anaerobic
Aquatic
Metabolism
Waived
This
study,
if
conducted
according
to
existing
guidelines,
would
not
likely
produce
useful
information
due
to
sodium
chlorate
antimicrobial
properties
that
can
destroy
the
microbial
populations
in
water­
sediment
systems.
If
the
microbial
population
is
destroyed,
the
study
cannot
adequately
address
the
role
of
microorganisms
in
the
degradation
of
chlorate.
It
is
more
likely
that
the
nature
and
concentration
of
redox
species
control
the
chemistry
of
chlorate
in
water­
sediment
systems.

162­
4
Aerobic
Aquatic
Metabolism
Waived
This
study,
if
conducted
according
to
existing
guidelines,
would
not
likely
produce
useful
information
due
to
sodium
chlorate
antimicrobial
properties
that
can
destroy
the
microbial
populations
in
water­
sediment
systems.
If
the
microbial
population
is
destroyed,
the
study
cannot
adequately
address
the
role
of
microorganisms
in
the
degradation
of
chlorate.
It
is
more
likely
that
the
nature
and
concentration
of
redox
species
control
the
chemistry
of
chlorate
in
water­
sediment
systems.

163­
1
Mobility
in
Soil
Waived
Sodium
chlorate
is
fully
ionized
in
water.
The
chlorate
anion
is
not
likely
to
adsorb
onto
soils
or
sediments.
Therefore,
high
mobility
was
anticipated.
Guideline
studies
would
not
provide
additional
information.

163­
2/­
3
Volatility
from
Soil
Waived
The
very
low
vapor
pressure
of
sodium
chlorate
(
9.7
x
10­
14
Pa
at
25
°
C)
does
not
trigger
the
volatility
from
soil
data
requirement
Data
Requirement
Status
Comment
Sodium
Chlorate
Appendices
­
5
164­
1
Terrestrial
Field
Dissipation
Not
Waived
This
data
requirement
has
never
been
waived.
There
is
major
uncertainty
on
how
long
sodium
chlorate
(
formulated)
may
remain
active
in
the
field.
Of
particular
concern
is
persistence
in
use
sites
in
semiarid
areas.
Additional
information
and/
or
actual
field
studies
is
needed.
The
open
literature
information
submitted
by
the
registrant
in
not
sufficient
to
decrease
the
uncertainty
on
field
persistence
of
sodium
chlorate
products.
(
Refer
to
Footnote
2)

165­
4
Bioaccumulation
in
Fish
There
is
no
waiver
request
for
this
data
requirement.
Although
this
data
requirement
may
be
waived,
the
registrant
must
formally
request
the
waiver
Sodium
chlorate
is
a
highly
hydrophilic
chemical.
Its
extremely
low
Log
n­
octanol/
water
partition
coefficient
of
­
7
does
not
trigger
this
data
requirement.

Table
A­
2.
Status
of
Ecotoxicity
Data
Requirements
Data
Requirement
Does
EPA
Have
Data
To
Complete
a
Risk
Assessment?
(
Yes,
No)
Bibliographic
Citation
Are
additional
data
needed?
Comment
71­
1(
a,
b)
Acute
Avian
Oral,
Quail/
Duck
Yes
421494­
01
No
71­
2(
a)
Acute
Avian
Diet,
Quail
Yes
418199­
08
No
71­
2(
b)
Acute
Avian
Diet,
Duck
Yes
418199­
07
No
71­
3
Wild
Mammal
Toxicity
No
N/
A
No
71­
4(
a)
Avian
Reproduction
Quail
No
N/
A
Yes
71­
4(
b)
Avian
Reproduction
Duck
No
N/
A
Yes
71­
5(
a)
Simulated
or
Actual
Terrestrial
Field
Study
No
N/
A
No
72­
1(
a,
b)
Acute
Fish
Toxicity
Rainbow
trout
and
Bluegill
Yes
418872­
02
418872­
03
No
72­
2(
a,
b)
Acute
Freshwater
Invertebrate
Toxicity
Yes
438748­
01;
418872­
04
No
Table
A­
2.
Status
of
Ecotoxicity
Data
Requirements
Data
Requirement
Does
EPA
Have
Data
To
Complete
a
Risk
Assessment?
(
Yes,
No)
Bibliographic
Citation
Are
additional
data
needed?
Comment
Sodium
Chlorate
Appendices
­
6
72­
3(
a)
Acute
Estuarine/
Marine
Toxicity
to
Fish
Yes
418872­
07
No
72­
3(
b)
Acute
Estu/
Marine
Invertebrate
Yes
418872­
05
418872­
06
No
72­
4(
a)
Early
Life­
Stage
Fish
No
N/
A
Yes
72­
4(
b)
Life­
Cycle
Aquatic
Invertebrate
No
N/
A
Yes
72­
5
Life­
Cycle
Fish
No
N/
A
No
72­
6
Aquatic
Org.
Accumulation
No
N/
A
No
72­
7(
a)
Simulated
Aquatic
Field
Study
No
N/
A
No
72­
7(
b)
Actual
Aquatic
Field
Study
No
N/
A
No
122­
1(
a)
Seed
Germ./
Seedling
Emerg.
Tier
I
Yes
463008­
02
No
122­
1(
b)
Vegetative
Vigor,
Tier
I
Yes
463008­
01
No
122­
2
Aquatic
Plant
Growth,
Tier
I
No
N/
A
No
123­
1(
a)
Seed
Germ./
Seedling
Emerg.,
Tier
II
No
N/
A
Yes
123­
1(
b)
Vegetative
Vigor
,
Tier
II
No
N/
A
Yes
123­
2
Aquatic
Plant
Growth
,
Tier
II
Yes
418872­
01
Yes
Only
data
on
green
algae
were
submitted.
Studies
in
four
other
aquatic
plant
species
are
required
for
herbicides.

124­
1
Terrestrial
Field
Study
No
N/
A
No
124­
2
Aquatic
Field
Study
No
N/
A
No
141­
1
Honey
Bee
Acute
Contact
Yes
N/
A
Yes
Study
was
submitted;
however,
a
new
copy
of
the
study
needs
to
be
submitted
to
the
Agency
for
evaluation
because
a
readable
copy
no
longer
exists.
Table
A­
2.
Status
of
Ecotoxicity
Data
Requirements
Data
Requirement
Does
EPA
Have
Data
To
Complete
a
Risk
Assessment?
(
Yes,
No)
Bibliographic
Citation
Are
additional
data
needed?
Comment
Sodium
Chlorate
Appendices
­
7
141­
2
Honey
Bee
Residue
on
Foliage
No
N/
A
No
141­
5
Field
Test
for
Pollinators
No
N/
A
No
OECD,
Section
2
#
207
Earthworm
Acute
Toxicity
Test
No
N/
A
No
Sodium
Chlorate
Appendices
­
8
Appendix
B­
1.
The
Chemistry
of
Chlorate
39
The
convention
of
using
Roman
numerals
to
express
the
oxidation
state
of
an
element
that
can
exist
in
more
than
one
oxidation
states
has
the
advantage
of
identifying
the
oxidation
state
of
oxidants
and
reductants
regardless
of
their
chemical
nature.
For
example,
aqua
ions,
complexes,
amorphous
or
crystalline
mineral
phase.

40
The
most
important
oxides
of
chlorine
are
"
Chlorine
Monoxide,
Cl2O"
and
"
Chlorine
Dioxide,
ClO2".
Both
are
gases
at
room
temperature.
"
Cl2O"
is
the
anhydride
of
hypochlorous
acid.
Chlorine
dioxide
is
explosive
as
a
liquid
or
concentrated
gas
and,
for
this
reason
it
is
generated
in­
situ
when
it
is
used
as
antimicrobial
or
wood­
pulp
bleaching
agents.
It
is
usually
prepared
by
reducing
sodium
chlorate.
The
oxidation
state
of
chlorine
in
chlorine
dioxide,
ClO2,
is
IV
(+
4).

Sodium
Chlorate
Appendices
­
9
A.
Oxidation
States
of
Chlorine
Chlorine
(
oxidation
state
0)
can
form
chemical
species
that
include
chlorine
in
different
oxidation
states.
In
aqueous
media,
the
predominant
species,
their
concentration,
and
reaction
kinetics
depend
on
pH,
temperature,
and
the
presence
and
nature
of
chemical
species
that
can
undergo
redox
reactions.
That
is,
chlorine
speciation
(
i.
e.,
reduced
and
oxidized
forms)
in
aqueous
media
is
driven
by
thermodynamics
(
equilibria)
as
well
as
by
kinetics.
Table
B­
1
shows
the
oxidation
states
of
chlorine
and
the
names
given
to
these
species39.

Table
B­
1.
Chlorine
and
Chlorine
Species
in
Aqueous
Media40.

Oxidation
State
Name
of
the
Acid
Form
Chemical
Representatiof
the
Acid
Form
Chemical
Name
of
the
Anion/
Salts
Chemical
Representation
of
the
Anion
0
Not
Applicable
Elemental
chlorine,
Cl2
(
gas)
Not
Applicable
Not
Applicable
­
I
(­
1)
Hydrochloric
acid
HCl
Chloride/
Chlorides
Cl­

I
(+
1)
Hypochlorous
acida
HOCl
Hypochloriteb/
Hypochlorites
"
ClO­"

III
(+
3)
Chlorous
acida
HOClO
Chloriteb/
Chlorites
ClO2
­

V
(+
5)
Chloric
Acida
HOClO2
Chlorateb/
Chlorates
ClO3
­

VII
(+
7)
Perchloric
Acid
HOClO3
Perchlorateb/
Perchlorates
ClO4
­

a
Stable
only
in
aqueous
solutions;
b
Oxyanion.
The
oxidation
state
of
chlorine
in
chlorine
dioxide
(
ClO2)
is
IV
Synthesis
of
Sodium
Chlorate
Sodium
chlorate
is
not
a
naturally
occurring
material.
It
is
prepared
by
electrolysis
of
sodium
chloride
(
NaCl
brine)
and
it
is
an
energy­
intensive
process.
It
requires
6
Faradays
to
produce
one
41
"
H+"
represents
the
hydrated
proton,
"
H3O+".

42
The
standard
hydrogen
electrode
(
SHE)
is
also
represented
by
the
symbol
"
NHE"
(
normal
hydrogen
electrode)

43
Chlorate,
an
oxidizing
agent,
accepts
electrons
and
generates
Cl
species
at
oxidation
states
lower
than
V(
i.
e,
it
gets
reduced).
In
all
redox
reactions
there
is
an
electron
donor
(
reducing
agent;
reductant)
and
an
electron
acceptor
(
oxidizing
agent;

oxidizer;
oxidant).
Thus,
the
electron
donor
species
gets
oxidized
while
the
electron
acceptor
gets
reduced.
That
is,
redox
processes
involves
electron
transfer.

Sodium
Chlorate
Appendices
­
10
mole
of
chlorate
and
the
reaction
is
endothermic
(
in
practice,
it
takes
5
kW"
hr
to
generate
1
kg
of
chlorate).
The
reaction
proceeds
via
intermediates
in
a
higher
oxidation
state
than
chloride,
such
as
chlorine
(
oxidation
state
­
I)
and
hypochlorite/
hypochlorous
acid
(
oxidation
state
I).
The
efficiency
of
chlorate
formation
by
an
electrolytic
process
is
controlled
by
temperature
and
pH.
The
efficiency
of
chlorate
formation
may
also
decrease
by
non­
electrolytic
processes,
such
as
by
the
presence
of
some
ionic
transition
metal
species
that
can
act
as
reductants
that
can
reduce
chlorate
to
chloro
species
in
lower
oxidation
states.
Transition
metals
are
metals
that
can
exist
in
two
or
more
oxidation
states,
such
as
Fe
and
Mn.
Chloric
acid,
the
corresponding
acid
form
of
chlorate,
exists
only
in
solution
and
it
is
a
strong
acid.

The
electrochemical
reactions
involved
in
the
preparation
of
sodium
chlorate
are:
Anode:
Oxidation
of
Chloride
to
chlorine
(
Cl­
6
½
Cl2
+
e­);
Cathode:
H2O
+
e­
6
½
H2
+
OHMixing
Cl2
+
2
OH­
6
Cl­
+
O
Cl­
+
H2O
(
disproportionation,
i.
e.,
reaction
producing
chemical
species
at
a
lower
and
a
higher
oxidation
state)
Further
disproportionation:
3O
Cl­
6
ClO3
­
+
Cl­
Further
anodic
oxidation:
O
Cl­
+
2
H2O
6
ClO3
­
+
2
H2
Source:
Kirk­
Othmer
Encyclopedia
of
Chemical
Technology
Cotton,
F.
A.
and
Wilkinson,
G.
"
Advanced
Inorganic
Chemistry",
5th
Edition,
Wiley
Interscience,
1988.
Greenwood
and
Earnshaw,
"
Chemistry
of
the
Elements",
Pergamon
B.
Oxidation­
Reduction
(
Redox)
Chemistry
of
Chlorate
Chlorate
is
a
strong
oxidizing
agent
(
oxidant;
oxidizer).
As
such,
chlorate
can
oxidize
chemical
species
considered
to
be
in
their
"
reduced"
state.
That
is,
any
oxidation
requires
a
reductant.
As
a
result,
the
oxidizer
gets
reduced
and
the
reductant
gets
oxidized.
Therefore,
an
oxidizer
is
an
electron
acceptor
and
the
reductant
is
the
electron
donor.

The
standard
electrode
potential
(
Eo,
defined
in
terms
of
standard
state
conditions
of
reactants
and
products;
Standard
state
conditions
are
25
°
C,
298
°
K
,
1
atm,
and
activity
=
1.0
for
all
reactants
and
products)
represents
a
redox
reaction
whose
left­
hand
electrode
is
a
hydrogen
electrode.
By
convention,
the
hydrogen
electrode
half
reaction
is
represented
as
H+
(
aqueous
41at
activity
a=
1)
+
e­
at
equilibrium
with
½
H
2
(
g,
1
atm)
and
taken
as
0.0
Volt42.
The
redox
couples
presented
here
follow
the
IUPAC
convention43
(
Eo
is
also
represented
as
Eo
h
).
Thus,
the
electrode
potential
of
a
44
The
activity
of
ions
in
water
is
the
effective
concentration
and
it
is
thermodynamically
more
precise
than
the
molar
concentration.
The
activity
of
any
ion
ai,
is
related
to
the
concentration
ci
by
the
activity
coefficient
(
i,
(
ai,
=
(
i
c
i
).
Discussion
of
methods
for
calculating
(
i
are
beyond
the
scope
of
this
Appendix.

45
The
Nernst
equation
correlates
the
emf
with
the
Gibbs
Free
Energy,
ª
G.
The
ª
G.
is
the
negative
value
of
the
maximum
electric
work,
W
(
ª
G
=
­
W=
q
ª
E
),
where
q
is
related
to
the
amount
of
charge
transferred
at
the
completion
of
the
reaction
and
q
is
related
to
the
number
of
electrons,
n,
involved
in
the
reaction.
Thus,
q=
nF,
where
F
is
the
Faraday
Constant,

Sodium
Chlorate
Appendices
­
11
cell
(
E)
is
taken
as
the
potential
of
the
right­
hand
terminal
with
respect
to
that
of
the
left­
hand
terminal.
If
the
cell
is
written
down
in
the
opposite
direction,
the
sign
of
E
must
be
reversed.

The
standard
electrode
potentials
for
reactions
involving
chlorate
are
presented
in
Table
B­
2
Equations
1
through
7
represent
potentials
at
which
chlorate
is
reduced
(
i.
e.,
accepts
electrons)
and
which
are
the
reduced
products
at
different
electrode
potentials.
Equations
8
and
9
represent
the
reduction
of
perchlorate
to
chlorate.
Note
that
the
nature
and
redox
potential
for
the
reduced
products
of
chlorate
are
pH
and
well
as
temperature
dependent.

Table
B­
2.
Standard
Electrode
Potentials
for
Redox
Reactions
of
Chlorate
(
Half­
cell
Potentials)

Redox
Couplea
E
°
/
E
°
b,
volts
(
V)
d
E
°
(
E
°
b)/
dT,
mVK
­
1
(
K=
°
Kelvin)

ClO3
­
+
6
3H2O
+
6e­
6
Cl­
+
6
OH­
(
1)
E
°
b,
=
0.622
dE
°
b)/
dT
=
­
1.333
2
ClO3
­
+
12
H+
+
10e­
6
Cl2
(
g)
+
6H2O
(
2)
E
°
=
1.468
dE
°
/
dT
=
­
0.347
ClO3
­
+
2H2O
+
4e­
6
ClO­
+
4
OH­
(
3)
E
°
b,=
0.488
dE
°
b/
dT
=
­
1.467
ClO3
­
+
3H+
+
3e­
6
HClO2
+
H2O
(
4)
E
°
=
1.181
dE
°
/
dT
=
­
0.180
ClO3
­
+
H2O
+
2e­
1
6
ClO2
­
+
2OH­
(
5)
E
°
b,
=
0.295
dE
°
b/
dT=
­
1.467
ClO3
­
+
2
H+
+
e­
6
ClO2
(
g)
+
H2O
(
6)
E
°
=
1.175
dE
°
/
dT
=
1.026
ClO3
­
+
H2O
+
e­
1
6
ClO2
(
g)
+
2OH­
(
7)
E
°
b,
=
­
0.481
dE
°
b/
dT
=
­
0.646
ClO4
­
+
2
H++
2e­
1
6
ClO3
­
+
H2O
(
8)
E
°
=
1.201
dE
°
/
dT
=
­
0.416
ClO4
­
+
H2O
+
2e­
1
6
ClO3
­
+
2OH­
(
9)
E
°
b,
=
0.374
dE
°
b/
dT
=
­
1.252
a
Defined
as
any
pair
of
the
same
element
in
different
oxidation
states.
Source:
Standard
Potentials
in
Aqueous
Solutions.
Edited
by
Bard,
A.
J.,
Parsons,
R.,
and
Jordan,
J.
IUPAC,
Commission
on
Electrochemistry
and
Electroanalytical
Chemistry,
Published
by
Marcel
Dekker,
Inc.,
New
York,
1985.
Most
of
these
redox
couples
were
experimentally
determined
Redox
Reactions­
General
The
tendency
for
a
redox
reaction
to
proceed
is
determined
by
the
electromotive
potential
(
emf).
That
is,
the
emf
is
the
driving
force
of
the
reaction.
Because
redox
reactions
involve
chemical
species
that
get
reduced
and
chemical
species
that
get
oxidized,
any
redox
reaction
can
be
written
as
the
sum
of
two
half­
reactions.
Under
real
conditions,
the
activity
of
reactants
and
products
deviate
from
the
unit
activity44
of
standard
conditions.
Therefore,
Eo
needs
to
be
corrected.
This
is
done
using
the
Nernst
relationship45.
For
any
redox
reaction
at
25
°
C
(
298
°
K)
which
is
the
charge
of
each
mole
of
electrons
(
F=
96,485
Coulombs/
mole).
Therefore,
ª
G
=
­
nF
ª
E
and
ª
G
°
=
­
nF
ª
E
°
for
standard
conditions
and
"
0.059"
applies
only
to
the
standard
temperature
of
298
°
K.

46
Likewise,
all
reduction
reactions
result
in
oxidation
of
the
reductant.

Sodium
Chlorate
Appendices
­
12
between
a
moles
of
reactant
A
and
b
moles
of
B
to
produce
c
moles
of
C
and
d
moles
of
D
(
i.
e,
aA
+
bB
=
cC
+
dD),

E
=
E
°
­
(
0.059/
n)
ln
[
C]
c
[
D]
d/
[
A]
a
[
B]
b
=
E
°
­
(
0.059/
n)
ln
K,

where
K
is
the
Equilibrium
Constant
If
[
D]=
[
H+]
and
[
B]=
[
H
2
]
and
since
[
H+]=
[
H
2
]=
1,
the
equation
reduces
to
E
=
E
°
­
(
0.059/
n)
ln
[
C]
c/[
A]
a
where
[
C]=
[
R]=
concentration
of
the
reduced
form
and
[
A]=
the
concentration
of
the
oxidized
form,
both
corrected
for
activity
((),

E
=
E
°
­
(
0.059/
n)
ln
[
R](
R
/[
O](
O
Since
all
oxidation
reactions
result
in
reduction
of
the
oxidizer46,
the
overall
redox
has
also
to
consider
the
half­
cell
of
the
reductant.
The
sum
of
the
two
half­
cells
(
i.
e.,
the
standard
reduction
and
oxidation
half­
cells)
give
the
net
potential
(
E
net
).
It
is
E
net
what
determines
the
thermodynamic
feasibility
of
specific
redox
reactions,

ÎG=
­
nF
(
E
net
)=
­
nF
(
E
red
+
E
ox
),
where
n
is
the
number
of
electrons
exchanged
in
the
net
reaction
Reactions
with
a
negative
ÎG
(
ÎG
<
0;
or
E
net
>
0)
can
occur
spontaneously.

Predominance
of
Chemical
Species
in
the
Environment
The
effects
of
pH
on
the
form
in
which
an
element
in
a
given
oxidation
state
exists
in
natural
waters
can
be
summarized
with
chemical
species
predominance
diagrams.
Knowledge
of
the
environmental
pH
is
not
sufficient
for
predicting
the
form
(
i.
e.,
oxidation
state;
chemical
species;
phase)
in
which
an
element,
the
chlorine
system
in
this
case,
will
exist
in
natural
waters.
When
a
chemical
element
can
exist
in
two
or
more
oxidation
states,
it
must
also
be
taken
into
consideration
whether
the
aqueous
environment
is
well
aerated
(
oxidizing)
or
polluted
with
organic
wastes
(
reducing).
Therefore,
it
becomes
necessary
to
add
the
redox
variable
to
expand
the
predominance
diagram
to
include
the
reduction
potential
of
the
environment
as
well
as
the
pH.
47
Pourbaix,
M.
Atlas
d'équilibres
èlectrochimiques
à
25
°
C.
Gauthier­
Villars,
Paris,
1963.
Pourbaix
diagrams
are
routinely
used
in
corrosion
and
minerals
processing
work.

48
For
example,
the
conversion
of
Diamond­
carbon
to
Graphite
carbon
is
favored
thermodynamically,
but
has
a
very
slow
kinetics.

49
See
"
Reactions
with
Organic
Matter"

50
For
example,
surface
reactions
with
minerals
that
are
semiconductors
(
galena).
For
interfacial
reactions
such
as
these,
the
particle
size
distribution
of
the
mineral
phase
is
an
important
controlling
factor
Sodium
Chlorate
Appendices
­
13
This
type
of
predominance
diagram
is
known
as
a
Pourbaix­
diagram
or
E­
pH
diagram47,
which
can
also
be
expressed
in
a
pE
scale.
The
pE
(
pE=
­
log
E)
scale
is
analogous
to
that
of
pH.
It
represents
the
concentration
of
the
standard
reducing
agent
and
is
obtained
from
the
reduction
potential
by
dividing
by
0.059.
Low
E
(
pE)
values
represent
a
reducing
environment,
while
high
E
(
pE)
values
represent
an
oxidizing
environment.

Thermodynamics
versus
Kinetics
The
Standard
Redox
Potentials,
as
well
as
the
predominance
diagrams
are
based
on
equilibria
relationships
(
i.
e.,
thermodynamics).
In
the
environment,
particularly
in
heterogeneous
media
such
as
soils,
suspended
particulates
in
natural
water,
redox
species
are
not
generally
in
equilibrium
and
the
concentrations
of
ionic
species
deviate
from
unit
activity.
In
addition,
redox
potentials
do
not
tell
how
fast
the
redox
reactions
take
place
(
i.
e.,
the
kinetics
of
the
redox
reactions).
Thus,
a
redox
reaction
that
may
be
thermodynamically
favored
might
be
kinetically
very
slow48.
In
summary,
the
redox
reactions
based
on
thermodynamic
equilibria
indicates
that
the
reaction
can
occur,
but
it
does
not
mean
that
they
will
occur
and
how
fast.

Natural
Redox
Environments
A
major
factor
controlling
the
redox
environment
is
the
nature
and
concentration
of
redox
species.
Major
chemical
species
associated
with
reducing
environments
are
transition
metals
in
low
oxidation
states
(
e.
g.,
Fe(
II),
Mn(
II)),
N­
species
in
low
oxidation
states
(
NO
2
­
;
NH
4
+);
S(­
II)
(
e.
g
HS­,
S
2­;
polysulfido
species),
and
organic
matter49.
Major
chemical
species
associated
with
oxidizing
environments
are
dissolved
dioxygen
(
O
2;
moleular
oxygen),
transition
metals
in
high
oxidation
states
such
as
Fe(
III);
Mn(
III,
IV),
sulfate,
and
nitrate.
In
addition
to
"
straight"
redox
reactions,
many
of
the
redox
species
in
natural
waters
may
also
act
as
photosensitizers.
Other
factors
controlling
the
redox
chemistry
of
a
natural
environment
are
the
population
of
aerobic
and
anaerobic
microorganisms.
In
addition,
many
of
the
transition
metals
may
be
present
as
mineral
phases
that
could
be
involved
in
surface­
catalyzed
reactions50.
The
half­
cell
reactions
for
important
environmental
reductants
are
presented
below
for
selected
species
Nitrogen
System
Table
B­
3.
Half­
cell
reactions
for
important
environmental
reductants
Sodium
Chlorate
Appendices
­
14
Redox
Couple,
E
°
/
E
°
b,
volts
(
V)

NO3
­
+
2H+
+
2e­
1
6
NO2
­
+
H2O
E
°
=
0.835
=
0.965
(
pH
4­
7)

NO3
­+
+
H2O
+
2e­
1
6
NO2
­
+
2OH­
E
°
b
=
0.01
NO3
­+
+
H2O
+
2e­
1
6
NO2
­
+
2OH­
E
°
b
=
0.01
NO3
­
+
10H+
+
6e­
1
6
NH4
+
+
3
H2O
E
°
=
0.87
NO2
­
+
8H+
+
8e­
1
6
NH4
+
+
2
H2O
E
°
=
0.897
NO2
­
+
7H+
+
8e­
1
6
NH3(
aq)
+
2
H2O
E
°
=
0.806
NO2
­+
6H+
+
8e­
1
6
NH3
(
g)
E
°
=
0.789
The
Iron
System
In
aqueous
solutions,
Fe(
II)
and
Fe(
III)
are
the
common
oxidation
states,
yet
the
chemistry
of
Fe(
II)/
Fe(
III)
is
extremely
complex.
In
addition
to
pH­
pE
dependent
reactions,
Fe(
II)/
Fe(
III)
can
generate
a
wide
range
of
chemical
species
than
can
occur
as
discreet
aqua
ions,
colloidal
species,
and
distinct
mineral
phases
of
varied
composition,
all
of
which
can
undergo
specific
redox
reactions.
In
acid
solutions
(
pH
<
2
and
in
the
absence
of
complexing
anions,
the
predominant
species
is
the
hexaaqua
Fe(
II)
complex
,
[
Fe(
H
2
O)
6
]
2+,
which
hydrolyzes
to
first
form
FeOH+
.
With
increasing
pH,
oxidation
of
Fe(
II)
to
Fe(
III)
species
takes
place
via
a
series
of
hydroxo
complexes,
precipitated
hydroxides,
and
mineral
oxides/
hydroxyoxides
(
e.
g.,
hematite/
magnetite;
goethite).
While
oxidation
involving
dioxygen
(
molecular
oxygen)
occurs,
other
oxidants
can
also
oxidize
Fe(
II).
Given
the
complexity
of
natural
systems
in
terms
of
types
and
concentration
of
natural
oxidants
(
e.
g.,
nitrate/
nitrite),
competitive
redox
reactions
are
expected
to
occur
in
the
environment.

In
acid
solution
(
pH
0),

Fe(
III)
+
e
6
Fe
(
II),
E
°
=
+
0.771
V
In
alkaline
solution,

Fe
(
III)
(
as
FeO
4
2­)
+
e
6
Fe
(
III)
(
as
FeO
2
­)
E
°
=
+
0.55
V
The
Sulfur
System
Like
with
chlorine,
sulfur
can
exist
in
more
than
one
oxidation
states.
The
oxidation
state
of
sulfur
in
the
sulfide
system
is
­
II.
The
inorganic
sulfide
species
that
might
be
present
in
anoxic
natural
waters
are:
H
2
S
(
hydrogen
sulfide,
gas;
hydrogen
sulfide
aqueous),
HS­,
and
S
2­.
The
predominance
of
each
of
these
species
depends
on
pH
and
is
governed
by
the
dissociation
51
At
18
°
C
in
water,
K1
=
9.1
x
10­
8,
H2S
(
aq)
6
H+
+
HSK2
=
1.2
x
10­
12,
HS­
6
H+
+
S
2­

Sodium
Chlorate
Appendices
­
15
constants,
K
1
and
K
2
,
of
hydrogen
sulfide
in
water51.
In
addition,
polysulfides
S
n
2­
may
be
present
in
some
aqueous
environment.
Sulfide
species
are
often
found
as
complexes
with
some
metal
ions.
Higher
oxidation
states
of
sulfur
(
e.
g.,
II,
IV,
VI)
are
more
predominant
in
oxic
systems,
of
which
sulfate
(
SO
4
2­,
S(
VI))
is
an
example.
Like
for
chlorine,
the
higher
oxidation
states
of
sulfur
are
oxyanions,
but
the
sulfur
oxyanions
are
more
numerous
and
complex
than
those
of
chlorine.

Organic
Material
The
reactions
below
are
examples
of
how
different
functional
groups
undergo
redox
reactions.
Many
of
these
functional
groups
are
present
in
natural
organic
matter,
for
example,
hydroxyl
groups
in
humic
acids,
but
other
simpler
organic
species
such
as
oxalate
may
also
be
present
in
natural
water.

Table
B­
4.
Redox
Reactions
with
Organic
Functional
Groups
Type
of
Oxidation
Reactions
Type
of
Reduction
Reactions
Alkanes
to
alcohols
(
R­
H
6
R­
OH)
Reductive
dehalogenation
(
R­
X
6
R­
H)

Alcohols
to
aldehydes
(
R­
OH
6
RCHO)
Vicinal
dehalogenation
(
X­
R­
R­
X6
R=
R)

Aldehydes
to
acids
(
RCHO
6
RCOOH)
Nitro
reduction
(
R­
NO2
6
R­
NH2)

Dehydrogenation
(­
CH­
CH­
6
­
C=
C­)
Azo
reduction
(
Ar­
N=
N­
Ar
6
2Ar­
NH2)

Oxidative
coupling
(
2R­
OH6
R­
O­
R)
Disulfide
to
thiol
(
R­
S­
S­
R6
2R­
SH)

Hydroquinones
to
quinones
(
HO­
Phenyl­
OH6
O=
Phenyl=
O)
Deoxygenation
of
sulfoxo
and
sulfoxides
(
R­
SO2­
R6R­
SO­
R6R­
S­
R)

Thiooxidation
(
R­
S­
R6
R­
SO­
R;
R­
SO2­
R)
Nitrosamine
Reduction
(
R2N­
N=
O6R2N­
H
+
HNO)

Fomation
of
disulfide
linkages
(
2R­
SH
6
R­
S­
S­
R)
Quinones
to
hydroquinones
(
O=
Phenyl=
O6HO­
Phenyl­
OH)

­
Dealkylation
(
R­
Y­
R'
6
R­
YH
+
R'H)

Redox
Conditions
in
Soils
and
Water
Controlling
the
Behavior
of
Chlorate
in
the
Environment
Soils
If
a
pH=
9
is
taken
as
the
upper
bound
of
a
soil
solution,
the
lower
extreme
value
of
pE
is
­
9
(
assuming
that
H
2
,
gas,
is
at
the
state
of
1
atm
and
298
°
K).
The
theoretical
range
of
pE
in
soil
is­
9
<
pE
<
+
16.6.
However,
a
pE
range
of
­
6
<
pE
<
12
is
more
realistic.
A
pE
of
­
6
corresponds
to
the
"
strongly
reduced"
boundary
and
+
12
to
the
"
strongly
oxidized"
boundary.
Like
for
52
Factors
contributing
to
the
acidity
of
natural
waters
in
the
Middle
Atlantic/
Northeast
of
the
USA
are
acid
mine
drainaged
and/
or
deposition
of
acid
rain.

Sodium
Chlorate
Appendices
­
16
natural
waters,
the
redox
environment/
behavior
of
the
soil
depends
on
the
nature,
concentration
and
E
h
­
pH
dependence
of
redox
species.

Table
B­
5.
pE
and
Redox
Conditions
of
Soils
Medium
pE
Soil,
suboxic
+
2<
p
E<
+
7
Soil,
oxic
+
7
<
p
E
Soil,
anoxic
p
E
<
+
2
Water
Chlorate
is
more
stable
under
alkaline
than
acidic
conditions.
Thus,
based
on
pH
dependence
alone,
it
would
be
less
persistent
in
acidic
than
alkaline
natural
waters.
In
general,
it
could
be
said
that
it
would
be
less
persistent
in
areas
of
the
country
where
the
pH
of
natural
water
is
<
7.
Acidic
natural
waters
are
predominantly
found
east
of
the
Mississippi
River,
with
acidity
increasing
with
latitude52.
Likewise,
chlorate
would
be
more
persistent
in
the
more
alkaline
water
bodies
West
of
the
Mississippi
River.

However,
as
previously
indicated,
pH
is
not
the
only
controlling
factor
in
the
persistence
of
chlorate
because
pH­
dependent
redox
reactions
must
be
taken
into
consideration.
Thus,
the
redox
conditions
of
the
water
body
also
controls
the
persistence
of
chlorate.
In
reducing
environments
(
i.
e.,
low
E;
pE),
chlorate
would
be
less
persistent
than
in
oxidizing
environments
(
high
E;
pE).

In
general,
the
variability
in
persistence
of
chlorate
in
natural
waters
has
a
spatial
and
temporal
component.
Spatial
variability
would
be
related
to
the
geographical
location
of
the
use
site
(
pH
and
nature
of
redox
species)
and
temporal
(
seasonal
variations
and
concentration
of
redox
species).
Therefore,
where,
when,
and
how
the
chemical
is
used
are
contributing
factors
to
the
persistent
of
chlorate
in
water.
Sodium
Chlorate
Appendices
­
17
Table
B­
6.
Spatial
and
temporal
variability
related
to
the
geographical
location
use
site
pH
pE
pH
of
Natural
Water
Systems
Seasonal
Variability
of
pE
<
7
Low
East
of
the
Mississippi
River,
particularly
in
the
Mid­
Atlantic
and
Northeastern
regions
Summer;
Early
Fall
(
High
concentration
of
organic
species)

<
7
High
East
of
the
Mississippi
River,
particularly
in
the
Mid­
Atlantic
and
Northeastern
regions
Winter;
Early
spring
>
7
Low
West
of
the
Mississippi
River
Summer;
Early
Fall
(
High
concentration
of
organic
species)

>
7
High
West
of
the
Mississippi
River
Winter;
Early
spring
A
spatial
and
temporal
variability
of
chlorate
is
also
expected
in
soils.
Factors
like
pH,
organic
matter
content
and
type,
moisture
content,
microbial
population.
Sodium
Chlorate
Appendices
­
18
Appendix
B­
2.
Discussion
on
Chlorate
Redox
Chemistry
as
it
Relates
to
Exposure
to
Aquatic
Organisms
in
the
Environment
Sodium
Chlorate
Appendices
­
19
MEMORANDUM:
January
27,
2005
SUBJECT:
pE/
pH
Predominance
and
3D
activity
ratio
diagrams
for
aqueous
chlorine
species
at
thermodynamic
equilibrium
TO:
Daniel
Rieder,
Chief
Environmental
Risk
Branch
3
Environmental
Fate
and
Effects
Division/
Office
of
Pesticide
Programs/
USEPA
Silvia
Termes,
Ph.
D.,
Chemist
Environmental
Risk
Branch
3
Environmental
Fate
and
Effects
Division/
Office
of
Pesticide
Programs/
USEPA
FROM:
Henry
Nelson,
Ph.
D.,
Chemist
Exposure
Assessment
Division
Office
of
Science
and
Coordination
Policy
(
OSCP/
OPPTS/
USEPA)

This
memo
provides
pE/
pH
predominance
and
3D
activity
fraction
diagrams
for
aqueous
chlorine
species
at
thermodynamic
equilibrium.
Chlorine
species
distributions
in
actual
natural
waters
at
any
given
time
may
deviate
substantially
from
such
equilibrium
computations
since
natural
waters
are
not
at
equilibrium
and
very
rarely
even
approach
equilibrium.

Aqueous
chlorine
reactions
considered
along
with
associated
equilibrium
expressions
and
equations
used
to
generate
activity
ratios
and
redox
pair
boundary
lines
in
the
formation
of
predominance
diagrams
are
listed
in
Attachment
A.
A
thermodynamic
spreadsheet
used
to
compute
)
G0
rxn
and
log
K
equil
=
)
G0
rxn
/(­
2.3RT)
(
where
K
eq
=
thermodynamic
activity
based
equilibrium
constant)
for
the
various
reactions
listed
in
Attachment
A
is
provided
in
Attachment
B.
The
format
of
the
thermodynamic
spreadsheet
provided
in
Attachment
B
was
developed
by
Dr.
Jim
Hetrick.
Free
energies
of
formation
are
in
kJ/
mol.
This
memo
is
an
extension
of
Dr.
Hetrick's
computations
of
chlorine
species
mole
fractions.

Mixed
equilibrium
constants
are
referred
to
as
"
mixed"
because
their
expressions
contain
chemical
species
concentrations
but
H+
and
e­
activities.
Mixed
equilibrium
constants
are
often
used
in
equilibrium
computations
(
Jensen
2004)
because
while
the
use
of
concepts
such
as
mass
balance
generally
requires
the
use
of
chemical
species
concentrations
rather
than
activities,
pH
and
redox
electrodes
respond
to
H+
and
e­
activities
rather
than
concentrations
where
(
)
(
)
pH
H
pE
e
=
 
=
 
+
 
log
log
Thermodynamic
activity
based
equilibrium
constants
are
equal
to
the
product
of
the
quotient
of
activity
coefficients
for
the
chemical
species
times
mixed
equilibrium
constants.
For
example
consider
the
following
reaction:

(
eq.
1)
Cl
H
O
ClO
H
e
 
 
+
 
+
 
+
+
2
2
2
Sodium
Chlorate
Appendices
­
20
The
thermodynamic
activity
based
equilibrium
constant
for
the
reaction
is
related
to
the
mixed
equilibrium
constant
for
the
reaction
by:

(
eq.
2)
(
)(
)(
)
(
)
[
](
)
(
)
[
]
K
ClO
H
e
Cl
ClO
H
e
Cl
K
eq
ClO
Cl
ClO
Cl
mixed
=
=
=
 
+
 

 
 
+
 

 
 

 
 

 
2
2
2
2
 
 
 
 
where
(
eq.
3)
[
](
)
(
)
[
]
K
ClO
H
e
Cl
mixed
=
 
+
 

 
2
2
and
(
=
activity
coefficients
(
)
=
designates
activities
[
]
=
designates
concentrations
The
construction
of
predominance
diagrams
relies
on
considerations
of
mass
balance
and
assumptions
of
equivalence
of
molar
concentrations
along
redox
couple
boundaries
which
in
turn
requires
the
use
of
chemical
species
concentrations
instead
of
activities.
At
the
same
time
it
is
convenient
to
maintain
the
H+
and
e­
levels
as
activities
as
previously
discussed.
The
most
accurate
way
of
generating
predominance
diagrams
is
to
convert
thermodynamic
activity
based
equilibrium
constants
(
which
are
computed
from
standard
free
energies
of
formation)
to
mixed
thermodynamic
activity
based
and
concentration
based
equilibrium
constants
by
dividing
the
activity
based
equilibrium
constants
by
quotients
of
the
activity
coefficients
of
the
chemical
species.
For
example,
from
eq.
2
above,
it
can
be
seen
that
the
K
mix
for
the
eq.
1
reaction
is
given
by:

(
eq.
4)

(
)
K
K
K
mix
eq
ClO
Cl
Cl
ClO
eq
=
=

 
 
 

 
 
 
 
 
The
mixed
equilibrium
constants
are
then
set
equal
to
mixed
quotients
that
use
concentrations
for
the
chemical
species
but
activities
for
H+
and
e­.
However,
predominance
diagrams
are
semiqualitative
(
they
predict
general
predominance
areas
rather
than
the
actual
activities
or
concentrations
of
various
species).
Therefore,
equations
for
generating
predominance
diagrams
are
often
approximations
based
on
the
assumption
that
the
expressions
for
the
mixed
equilibrium
constants
are
approximately
equal
to
the
thermodynamic
equilibrium
constants.
That
assumption
is
used
in
the
generation
of
the
predominance
diagrams
in
this
document.
The
accuracy
of
that
assumption
depends
upon
how
close
the
quotient
of
activity
coefficients
is
to
one.
The
chlorine
species
considered
here
are
either
neutral
or
univalent.
Most
freshwaters
have
ionic
strengths
between
0.001
M
and
0.01
M
(
Jensen
2004).
In
freshwaters
with
ionic
strengths
between
0.001
and
0.01
M,
the
activity
coefficients
of
neutral
species
will
be
close
to
one.
Based
on
the
use
of
Sodium
Chlorate
Appendices
­
21
the
Debye­
Huckel
equation
for
ionic
strengths
up
to
0.005
M
and
the
extended
Debye­
Huckel
equation
for
ionic
strengths
between
0.005
M
and
0.01
M,
the
activity
coefficients
of
univalent
ions
range
from
approximately
0.9
in
waters
with
ionic
strength
=
0.01
M
to
close
to
one
in
waters
with
ionic
strengths
=
0.001
M
(
Langmuir
2002).
Therefore,
the
assumption
that
the
expressions
for
the
mixed
equilibrium
constants
are
approximately
equal
to
the
thermodynamic
equilibrium
constants
are
generally
adequate
for
generating
semi­
qualitative
pE/
pH
predominance
diagrams
for
freshwaters.

In
addition
to
generating
predominance
diagrams,
activity
fractions
are
generated
for
various
chlorine
species
as
a
function
of
pE
and
pH.
This
is
done
by
rearranging
the
equations
in
Attachment
A
to
give
the
activity
of
each
chlorine
species
considered
in
terms
of
the
activity
of
a
common
chlorine
species
(
Cl­
is
used
here
but
any
of
the
species
could
have
served
as
the
common
species).
The
ratio
of
the
activity
of
each
chlorine
species
(
in
terms
of
the
Cl­
activity)
to
the
total
activity
of
chlorine
species
(
in
terms
of
the
Cl­
activity)
is
then
computed.
By
performing
computations
for
pHs
>
4,
Cl
2(
aq)
does
not
have
to
be
included
in
the
activity
ratio
computations
because
the
construction
of
predominance
diagrams
indicates
that
Cl
2(
aq)
will
be
predominant
(
if
at
all
­
see
discussion
of
Case
1
versus
Case
2
below)
at
pEs
above
the
stability
of
water
and
at
pHs
<
2
well
below
the
lower
pH
limit
of
natural
waters
(
pH
5)
and
well
below
the
lower
pH
limit
of
our
calculations
(
pH
4).
Not
including
Cl
2(
aq)
in
the
activity
fraction
computations
allows
for
complete
cancellation
of
the
Cl­
activity
from
the
numerator
and
denominator
of
each
ratio.
The
activity
fractions
are
in
terms
of
the
thermodynamic
activity
based
equilibrium
constants
(
computed
in
the
Attachment
B
thermodynamic
spreadsheet),
pH,
and
pE.

Mole
fractions
could
not
be
computed
because
they
would
be
in
terms
of
the
mixed
equilibrium
constants
which
were
not
computed
(
only
thermodynamic
activity
based
equilibrium
constants
were
computed).
However,
for
low
ionic
strength
waters,
the
activity
fractions
provide
an
approximate
estimate
of
mole
fractions.

Two
cases
are
considered.
Case
1
considers
only
the
lower
oxidation
state
chlorine
species
(
Cl­,
Cl
2(
aq),
ClO­,
and
HClO).
Case
2
considers
higher
oxidation
state
chlorine
species
(
ClO
2
­,
ClO
2(
aq),
ClO
3
­,
and
ClO
4
­)
as
well
as
the
lower
oxidation
state
chlorine
species
(
Cl­,
Cl
2(
aq),
ClO­,
and
HClO).
Case
1
is
included
in
this
memo
only
because
it
is
the
case
considered
by
several
aquatic
chemistry
texts.
However,
Case
1
is
misleading
because
it
results
in
predominance
and
activity
fraction
diagrams
that
shows
predominance
areas
and
areas
of
high
activity
fractions
for
ClO­,
and
HClO
that
are
not
reflected
in
the
much
more
accurate
Case
2
predominance
and
activity
fraction
diagrams
that
consider
higher
oxidation
state
chlorine
species
as
well
as
lower
oxidation
state
chlorine
species.

The
more
accurate
Case
2
shows
predominance
areas
and
high
activity
fractions
for
only
ClO
4
­

and
Cl­.
Although
Case
1
and
Case
2
differ
substantially
for
ClO­,
HClO,
and
ClO4
­,
they
both
show
Cl­
as
the
only
predominant
species
at
thermodynamic
equilibrium
within
the
pE
and
pH
ranges
of
natural
waters.

Case
1:
Case
1
considers
only
the
lower
oxidation
state
chlorine
species
(
Cl­,
Cl
2(
aq),
ClO­,
and
HClO).
A
pE/
pH
predominance
diagram
considering
only
those
lower
oxidation
state
chlorine
Sodium
Chlorate
Appendices
­
22
species
is
provided
in
several
aquatic
chemistry
texts
(
e.
g.,
Stumm
and
Morgan
1995;
Pankow
1991;
Snoeyink
1980;
Jensen
2004).
That
diagram
is
recreated
independently
here
(
Chart
1a)
using
a
more
systematic
approach
involving
the
separate
determination
of
predominance
areas
for
each
chlorine
species
(
Attachment
C,
Charts
1b
through
1e)
and
then
combining
the
separate
diagrams
into
one
predominance
diagram
(
Chart
1a).
The
general
use
of
such
a
systematic
approach
for
generating
pE/
pH
predominance
diagrams
was
recommended
by
Benjamin
(
2002).

Because
of
the
2
to
1
chlorine
stoichiometry
of
Cl
2(
aq)
compared
to
other
aqueous
chlorine
species
considered
in
Case
1,
the
development
of
a
predominance
area
for
Cl
2(
aq)
in
an
overall
pE/
pH
predominance
diagram
for
aqueous
chlorine
species
requires
consideration
of
chlorine
mass
balance
and
an
assumption
concerning
total
chlorine
(
Stumm
and
Morgan
1995;
Pankow
1991;
Snoeyink
1980;
Jensen
2004).

Chart
1a
was
generated
using
the
same
assumption
(
total
chlorine
concentration
=
0.04
M)
as
used
in
those
references.
A
total
chlorine
concentration
of
0.04
M
is
somewhat
higher
than
typical
chlorine
background
concentrations
in
freshwater.
However,
the
use
of
a
higher
assumed
total
chlorine
results
in
a
slightly
larger
Cl
2(
aq)
predominance
area
in
Chart
1a
that
is
easier
to
illustrate
than
when
using
a
smaller
assumed
total
chlorine.
It
is
somewhat
academic
in
that
the
the
Cl
2(
aq)
predominance
area
in
Chart
1a
is
still
small
and
still
occurs
at
high
pEs/
low
pH
well
outside
the
pE
&
pH
ranges
of
natural
waters.

In
addition
to
a
small
predominance
area
for
Cl
2(
aq)
at
high
pEs
and
very
low
pHs,
Chart
1a
for
Case
1
predicts
predominance
areas
for
HClO
at
high
pEs
(
outside
those
of
natural
waters)
and
acidic
pHs,
for
ClO­
at
high
pEs
(
also
outside
those
of
natural
waters)
and
alkaline
pHs,
and
for
Cl­
at
lower
pEs
including
those
within
the
range
of
pE
and
pH
of
natural
waters
(
region
ABCD
in
Chart
1a).
The
Case
1
predominance
diagram
Chart
1a
is
misleading
because
it
shows
predominance
areas
for
ClO­,
and
HClO
that
are
not
reflected
in
the
Case
2
predominance
diagram
that
considers
higher
oxidation
state
chlorine
species
as
well
as
lower
oxidation
state
chlorine
species.

Case
1
activity
fraction
diagrams
were
generated
for
Cl­,
ClO­,
and
HClO
for
pHs
between
4
and
10
and
for
pEs
between
­
10
and
30.
The
Case
1
Cl­
activity
fraction
was
generated
from
equation
5
below.
The
Case
1
ClO­
and
HClO
activity
fractions
were
generated
from
equations
2f
and
3f,
respectively
in
Attachment
A.
Sodium
Chlorate
Appendices
­
23
(
)
(
)
(
)
(
)
(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)
(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
f
Cl
Cl
ClO
HClO
Cl
Cl
K
Cl
H
e
K
Cl
H
e
K
H
e
K
H
e
Cl
Case
eq
eq
eq
eq
K
pH
pE
K
pH
pE
pH
pE
pH
pE
eq
eq
 
=
+
+
=

+
+
=
+
+
=

+
+
=
+
+
 

 
 
 

 
 

+
 
 

+
 
+
 
+
 

 
 
 
 
 

 
 
 

 
 
(
)

log
log
.
.
1
2
2
2
3
2
2
2
2
3
2
2
2
58
1
2
2
50
6
2
1
1
1
1
10
10
10
10
10
10
1
1
10
10
10
10
10
10
2
3
(
eq.
5)

As
expected,
the
Case
1
activity
fraction
diagrams
for
Cl­,
ClO­,
and
HClO
(
Charts
2a,
2b,
and
2c,
respectively)
are
consistent
with
the
Case
1
predominance
diagram
1a
with
high
activity
fractions
approaching
1
in
areas
of
pE
and
pH
where
the
Case
1
predominance
diagram
1a
indicates
they
are
the
predominant
species.
However,
like
Case
1
predominance
diagram
Chart
1a,
Case
1
activity
fraction
diagrams
Charts
2b
and
2c
are
misleading
because
they
show
areas
of
high
activity
fractions
for
ClO­,
and
HClO
that
are
not
reflected
in
the
Case
2
activity
fraction
diagrams
that
consider
higher
oxidation
state
chlorine
species
as
well
as
lower
oxidation
state
chlorine
species.

Case
2:
Case
2
is
much
more
accurate
than
Case
1
because
it
considers
higher
oxidation
state
chlorine
species
(
ClO
2
­,
ClO
2(
aq),
ClO
3
­,
and
ClO
4
­)
as
well
as
the
lower
oxidation
state
chlorine
species
(
Cl­,
Cl
2(
aq),
ClO­,
and
HClO).
A
pE/
pH
predominance
diagram
considering
the
higher
oxidation
state
chlorine
species
as
well
as
the
lower
oxidation
state
chlorine
species
is
provided
in
Chart
3a.
A
systematic
approach
was
used
involving
the
separate
determination
of
predominance
areas
for
each
chlorine
species
(
Attachment
D,
Charts
3b
through
3i)
and
then
combining
the
separate
diagrams
into
one
predominance
diagram
(
Chart
3a).
As
previously
indicated,
the
general
use
of
such
a
systematic
approach
for
generating
pE/
pH
predominance
diagrams
was
recommended
by
Benjamin
(
2002).

Chart
3a
for
Case
2
predicts
predominance
areas
for
only
ClO
4
­
at
high
pEs
(
above
those
of
natural
waters),
and
for
Cl­
at
lower
pEs
including
those
within
the
range
of
pE
and
pH
of
natural
waters
(
region
ABCD
in
Chart
3a).

Case
2
activity
fraction
diagrams
were
generated
for
Cl­,
ClO­,
HClO,
ClO
2
­,
ClO
2(
aq),
ClO
3
­,
and
ClO
4
­
for
pHs
between
4
and
10
and
for
pEs
between
­
10
and
30.
The
Case
2
Cl­
activity
fraction
was
generated
from
equation
6
below.
The
Case
2
ClO­,
HClO,
ClO
2
­,
ClO
2(
aq),
ClO
3
­,
and
ClO
4
­

activity
ratios
were
generated
from
equations
2g,
3g,
4f,
5f,
6f,
and
7f,
respectively,
in
Attachment
A.
Sodium
Chlorate
Appendices
­
24
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)(
)

(
)
(
)
(
)(
)
(
)
(
)
(
)
f
Cl
Cl
ClO
HClO
ClO
ClO
ClO
ClO
Cl
Cl
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
H
e
K
H
e
K
H
e
K
H
Cl
Case
aq
eq
eq
eq
eq
eq
eq
eq
eq
eq
eq
 
=
+
+
+
+
+
+
=

+
+
+
+
+
+
=

+
+
+
+
 

 
 
 
 
 

 

 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 

+
 
+
 
+
 
+
(
)

(
)
2
2
2
3
4
2
2
2
3
2
4
4
4
5
4
5
6
6
6
7
8
8
2
2
2
3
2
4
4
4
5
4
1
1
(
)
(
)
(
)
(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)

(
)(
)
(
)(
)
(
)
e
K
H
e
K
H
e
eq
eq
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
pH
pE
pH
pE
pH
eq
eq
eq
eq
eq
eq
 
+
 
+
 

 
 
 
 
 
 
 
 
 
 
 
 

 

 
 
 

 
 
 

 
+
+
=

+
+
+
+
+
+
=

+
+
+
5
6
6
6
7
8
8
2
2
2
4
4
4
5
6
6
8
8
58
1
2
2
50
6
2
109
1
1
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
1
1
10
10
10
10
10
10
10
10
2
3
4
5
6
7
log
log
log
log
log
log
.
.
.

(
)
(
)(
)
(
)(
)
(
)(
)
4
4
126
8
4
5
147
1
6
6
187
8
8
8
10
10
10
10
10
10
10
10
10
10
 
 

 
 
 

 
 
 

 
 
+
+
+
pE
pH
pE
pH
pE
pH
pE
.
.
.

(
eq.
6)

As
expected,
the
Case
2
activity
fraction
diagrams
for
predominant
species
Cl­
and
ClO
4
­
(
Charts
4a
and
4b)
are
consistent
with
the
Case
2
predominance
diagram
3a
with
high
activity
fractions
approaching
1
in
areas
of
pE
and
pH
where
the
Case
2
predominance
diagram
3a
indicates
they
are
the
predominant
species.
The
Case
2
activity
fraction
diagrams
for
the
other
species
(
ClO­,
HClO,
ClO
2
­,
ClO
2(
aq),
and
ClO
3
­)
(
Charts
4c
through
4g
in
Attachment
E)
are
also
consistent
with
the
Case
2
predominance
diagram
3a
in
that
none
are
shown
as
predominant
in
Case
2
predominance
diagram
3a
and
none
have
activity
ratios
>
10­
6.
Sodium
Chlorate
Appendices
­
25
Chart
1a:
Case
1
aqueous
chlorine
species
predominance
diagram:
(
Considering
only
Cl­,
Cl2(
aq),
ClO­,
and
HClO);
Chart
1a
from
combination
of
Charts
1b
­
1e
in
Attachment
C
;
Clpredominant
in
region
ABCD
representing
pE
&
pH
ranges
of
natural
waters.

­
10
­
8
­
6
­
4
­
2
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
pH
pE
3a
14a
2b
W1
W2
pH5
pH9
1a
2)
ClO
­/
Cl
­
3)
HClO/
Cl
­
14)
HClO/
ClO
­

O2(
g)

H2O(
l)

H2O(
l)

H2(
g)
HClO
predominance
ClO
­
predominance
Cl
­
predominance
Cl
­
predominance
in
pE
&
pH
ranges
of
natural
waters
A
B
C
D
1)
Cl2(
aq)/
Cl
­
Cl2(
aq)
predominance
HClO
Sodium
Chlorate
Appendices
­
26
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
­
2
­
4
­
6
­
8
­
10
4
6
8
10
0.000
0.200
0.400
0.600
0.800
1.000
Cl­
Activity
Fraction
pE
pH
Chart
2a:
Case
1
Cl­
activity
fraction
considering
only
Cl­,
HClO,
and
ClO­.

0.800­
1.000
0.600­
0.800
0.400­
0.600
0.200­
0.400
0.000­
0.200
Sodium
Chlorate
Appendices
­
27
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
­
2
­
4
­
6
­
8
­
10
4
6
8
10
0.000
0.200
0.400
0.600
0.800
1.000
HClO
Activity
Fraction
pE
pH
Chart
2b:
Case
1
HClO
activity
fraction
considering
only
Cl­,
HClO,
and
ClO­.

0.800­
1.000
0.600­
0.800
0.400­
0.600
0.200­
0.400
0.000­
0.200
Sodium
Chlorate
Appendices
­
28
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
­
2
­
4
­
6
­
8
­
10
4
6
8
10
0.000
0.200
0.400
0.600
0.800
1.000
ClO­
Activity
Fraction
pE
pH
Chart
2c:
Case
1
ClO­
activity
fraction
considering
only
Cl­,
HClO,
and
ClO­.

0.800­
1.000
0.600­
0.800
0.400­
0.600
0.200­
0.400
0.000­
0.200
Sodium
Chlorate
Appendices
­
29
Chart
3a:
Case
2
aq.
chlorine
species
predominance
diagram:
(
Considering
Cl­,
Cl2(
aq),
ClO­,

HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­);
Based
on
Charts
3b
­
3i
in
Attachment
D;
Clpredominant
in
region
ABCD
representing
pE
&
pH
ranges
of
natural
waters.

­
10
­
5
0
5
10
15
20
25
30
2
3
4
5
6
7
8
9
10
11
12
pH
pE
7
W1
W2
pH5
pH9
ClO4
­
predominance
Cl
­

Cl
­
predominance
in
pE
&
pH
ranges
of
natural
waters
H2O(
l)
O2(
g)

H2O(
l)

H2(
g)
A
B
C
D
7)
ClO4
­/
Cl
­
Sodium
Chlorate
Appendices
­
30
ATTACHMENT
A
to
Appendix
B­
2:

Primary
chlorine
species
in
aqueous
solution:

The
primary
chlorine
species
in
aqueous
solution
are
Cl­,
Cl
2(
aq),
ClO­,
HClO,
ClO
2
­,
ClO
2(
aq),
ClO
3
­,
and
ClO
4
­
in
which
Cl
exhibits
oxidation
states
of
­
I,
0,
I,
III,
IV,
V,
and
VII,
respectively.
HClO
3
and
HClO
4
are
completely
dissociated
strong
acids
and
HClO
2
has
a
pK
a
=
2.
Therefore
they
are
not
further
considered
here
for
computations
at
pHs
>
4.

Provided
below
are:

(
a)
28
reactions
between
each
aqueous
chlorine
species.
(
b)
Equations
for
the
thermodynamic
activity
based
equilibrium
constant
for
each
reaction
(
c)
Equations
for
the
mixed
equilibrium
constant
for
each
reaction
(
d)
The
logarithm
of
the
approximate
equation
for
the
equilibrium
constant
for
each
reaction
(
e)
Equations
for
boundary
lines
used
in
generating
pE/
pH
predominance
diagrams
for
aqueous
chlorine
species.
These
equations
are
derived
by
substituting
the
value
of
the
logarithm
of
the
equilibrium
constant
into
the
previous
equation
and
assuming
that
along
the
boundary
the
concentration
of
the
species
on
one
side
of
the
boundary
=
the
concentration
of
the
species
on
the
other
side
of
the
boundary.
(
f)
Equations
for
Case
1
and
Case
2
activity
fractions
for
each
reaction
The
thermodynamic
activity
based
equilibrium
constant
computations
were
performed
using
the
Attachment
B
Excel
spreadsheet.
The
format
of
the
spreadsheet
used
for
thermodynamic
computations
was
developed
by
Dr.
Jim
Hetrick.

Reactions
1
­
7
(
reactions
involving
Cl­):

Rxn
1:
(
eq.
1a)
2
2
2
Cl
Cl
e
aq
 
 
 
+
(
)

(
eq.
1b)
(
)(
)
(
)
K
Cl
e
Cl
eq
aq
1
2
2
2
=
 

 
(
)

(
eq.
1c)
[
](
)
[
]
K
Cl
e
Cl
mix
aq
1
2
2
2
=
 

 
(
)

For
generating
predominance
diagrams,
assume
that
K
eq1
~
K
mix1
such
that
Sodium
Chlorate
Appendices
­
31
(
eq.
1d)
[
]
[
]
(
)
[
]
[
]
log
log
log
log
log
(
)
(
)
K
K
Cl
Cl
e
Cl
Cl
pE
eq
mix
aq
aq
1
1
2
2
2
2
 
=
+
=
 
 
 
 

Along
the
Cl
2(
aq)/
Cl­
boundary
line,
it
is
reasonable
to
assume
that
[
Cl
tot
]
~
[
Cl­]
+
2[
Cl
2(
aq)].
Therefore,
along
the
boundary
for
a
total
chlorine
concentration
[
Cl
tot
]
=
0.04
mol/
L,
[
Cl­]
~
0.02
mol/
L
and
[
Cl
2(
aq)]
~
0.01
mol/
L.
From
the
attached
thermodynamic
spreadsheet,
logK
eq1
=
­
47.2.
Substituting
those
values
into
eq.
1d
and
rearranging
gives
the
following
equation
for
the
Cl
2(
aq)

/
Cl­
boundary
line:

[
]
[
]
(
)
2
472
001
002
47
2
25
47
2
14
48
6
24
3
2
pE
pE
=
+
=
+
=
+
=
 
=
.
log
.

.
.
log
.
.
.
.

(
eq.
1e)

Rxn
2:
(
eq.
2a)
Cl
H
O
ClO
H
e
 
 
+
 
+
 
+
+
2
2
2
(
eq.
2b)
(
)(
)(
)
(
)
K
ClO
H
e
Cl
eq2
2
2
=
 
+
 

 

(
eq.
2c)
[
](
)
(
)
[
]
K
ClO
H
e
Cl
mix2
2
2
=
 
+
 

 

For
generating
predominance
diagrams,
assume
that
K
eq2
~
K
mix2
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
Cl
H
e
ClO
Cl
pH
pE
eq
mix
2
2
2
2
2
2
 
=
+
+
=
 
 
 

 
+
 
 

 

(
eq.
2d)

Along
the
ClO­/
Cl­
boundary
line,
[
ClO­]
=
[
Cl­]
so
log{[
ClO­]/[
Cl­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq2
=
­
58.1.
Substituting
those
values
into
eq.
2d
and
rearranging
gives
the
following
equation
for
the
ClO­/
Cl­
boundary
line:

(
eq.
2e)
2
581
2
291
pE
pH
pE
pH
=
 
 
=
 
.
.
Sodium
Chlorate
Appendices
­
32
(
)
(
)
(
)
(
)
(
)
(
)
(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)

(
)
(
)
(
)(
)

(
)(
)

(
)(
)
(
)(
)
(
)(
)

(
)
f
ClO
Cl
ClO
HClO
K
Cl
H
e
Cl
K
Cl
H
e
K
Cl
H
e
K
H
e
K
H
e
K
H
e
ClO
Case
eq
eq
eq
eq
eq
eq
K
pH
pE
K
pH
pE
K
pH
pE
pH
pE
pH
eq
eq
eq
 
=
+
+
=

+
+
=
+
+
=

+
+
=
+
 

 
 
 

+
 

 
 

+
 
 

+
 
+
 

+
 
+
 

 
 

 
 
 
 
 

 
 

 

 
(
)

log
log
log
.

.
1
2
2
2
2
2
2
3
2
2
2
2
2
2
2
3
2
2
2
2
2
58
1
2
2
58
1
1
10
10
10
1
10
10
10
10
10
10
10
10
10
1
10
10
2
2
3
(
)
(
)(
)
2
2
50
6
2
10
10
10
10
 
 

 
 
+
pE
pH
pE
.

(
eq.
2f)

(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)
(
)

(
)
(
)

(
)
(
)
(
)(
)
f
ClO
Cl
ClO
HClO
ClO
ClO
ClO
ClO
K
Cl
H
e
Cl
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
H
e
K
H
e
K
H
e
ClO
Case
aq
eq
eq
eq
eq
eq
eq
eq
eq
eq
eq
 
=
+
+
+
+
+
+
=

+
+
+
+
+
+
=

+
+
 

 
 
 
 
 

 

+
 

 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 

+
 

+
 
+
 
(
)

(
)
2
2
2
3
4
2
2
2
2
2
2
3
2
4
4
4
5
4
5
6
6
6
7
8
8
2
2
2
2
2
2
3
2
1
(
)
(
)
(
)
(
)
(
)
(
)
(
)(
)

(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)

(
)
+
+
+
+
=

+
+
+
+
+
+
=
+
 
+
 
+
 
+
 

 
 

 
 
 
 
 
 
 
 
 
 
 
 

 

 
K
H
e
K
H
e
K
H
e
K
H
e
eq
eq
eq
eq
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
pH
eq
eq
eq
eq
eq
eq
eq
4
4
4
5
4
5
6
6
6
7
8
8
2
2
2
2
2
4
4
4
5
6
6
8
8
58
1
2
10
10
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
2
2
3
4
5
6
7
log
log
log
log
log
log
log
.

(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
2
58
1
2
2
50
6
2
109
1
4
4
126
8
4
5
147
1
6
6
187
8
8
8
 

 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
+
+
+
+
+
+
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
.
.
.
.
.
.

(
eq
2g)

Rxn
3:
(
eq.
3a)
Cl
H
O
HClO
H
e
 
+
 
+
 
+
+
2
2
(
eq.
3b)
(
)(
)(
)
(
)
K
HClO
H
e
Cl
eq3
2
=
+
 

 

(
eq.
3c)
[
](
)(
)
[
]
K
HClO
H
e
Cl
mix3
2
=
+
 

 
Sodium
Chlorate
Appendices
­
33
For
generating
predominance
diagrams,
assume
that
K
eq3
~
K
mix3
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
HClO
Cl
H
e
HClO
Cl
pH
pE
eq
mix
3
3
2
2
 
=
+
+
=
 
 
 
+
 
 

(
eq.
3d)

Along
the
HClO/
Cl­
boundary
line,
[
HClO]
=
[
Cl­]
so
log{[
HClO]/[
Cl­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq3
=
­
50.6.
Substituting
those
values
into
eq.
3d
and
rearranging
gives
the
following
equation
for
the
HClO/
Cl­
boundary
line:

(
eq.
3e)
2
50
6
253
05
pE
pH
pE
pH
=
 
 
=
 
.
.
.

(
)
(
)
(
)
(
)
(
)
(
)(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)(
)

(
)
(
)
(
)(
)

(
)(
)

(
)(
)
(
)(
)
(
)(
)

(
)(
)
f
HClO
Cl
ClO
HClO
K
Cl
H
e
Cl
K
Cl
H
e
K
Cl
H
e
K
H
e
K
H
e
K
H
e
HClO
Case
eq
eq
eq
eq
eq
eq
K
pH
pE
K
pH
pE
K
pH
pE
pH
pE
pH
pE
eq
eq
eq
(
)

log
log
log
.

.
1
3
2
2
2
2
3
2
3
2
2
2
2
3
2
2
2
2
50
6
2
58
1
2
2
1
10
10
10
1
10
10
10
10
10
10
10
10
10
1
10
10
10
3
2
3
=
+
+
=

+
+
=
+
+
=

+
+
=
+
+
 
 
 

+
 

 
 

+
 
 

+
 
+
 

+
 
+
 

 
 

 
 
 
 
 

 
 

 

 
 
(
)(
)
10
10
10
50
6
2
 

 
 
.

pH
pE
(
eq.
3f)

(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)(
)

(
)(
)

(
)
(
)
(
)(
)
f
HClO
Cl
ClO
HClO
ClO
ClO
ClO
ClO
K
Cl
H
e
Cl
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
H
e
K
H
e
K
H
e
K
HClO
Case
aq
eq
eq
eq
eq
eq
eq
eq
eq
eq
eq
eq
(
)

(
)
2
2
2
3
4
3
2
2
2
2
3
2
4
4
4
5
4
5
6
6
6
7
8
8
3
2
2
2
2
3
2
4
1
=
+
+
+
+
+
+
=

+
+
+
+
+
+
=

+
+
+
 
 
 
 
 

 

+
 

 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 

+
 

+
 
+
 
(
)
(
)
(
)
(
)
(
)
(
)
(
)(
)

(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)

(
)(
)
H
e
K
H
e
K
H
e
K
H
e
eq
eq
eq
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
pH
pE
eq
eq
eq
eq
eq
eq
eq
+
 
+
 
+
 
+
 

 
 

 
 
 
 
 
 
 
 
 
 
 
 

 

 
 
+
+
+
=

+
+
+
+
+
+
=

+
4
4
5
4
5
6
6
6
7
8
8
2
2
2
2
4
4
4
5
6
6
8
8
50
6
2
10
10
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
1
3
2
3
4
5
6
7
log
log
log
log
log
log
log
.

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
58
1
2
2
50
6
2
109
1
4
4
126
8
4
5
147
1
6
6
187
8
8
8
 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
+
+
+
+
+
.
.
.
.
.
.

pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
(
eq.
3g)
Sodium
Chlorate
Appendices
­
34
Rxn
4:
(
eq.
4a)
Cl
H
O
ClO
H
e
 
 
+
 
+
 
+
+
2
4
4
2
2
(
eq.
4b)
(
)(
)
(
)
(
)
K
ClO
H
e
Cl
eq4
2
4
4
=
 
+
 

 

(
eq.
4c)
[
](
)
(
)
[
]
K
ClO
H
e
Cl
mix4
2
4
4
=
 
+
 

 

For
generating
predominance
diagrams,
assume
that
K
eq4
~
K
mix4
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
Cl
H
e
ClO
Cl
pH
pE
eq
mix
4
4
2
2
4
4
4
4
 
=
+
+
=
 
 
 

 
+
 
 

 

(
eq.
4d)

Along
the
ClO
2
­/
Cl­
boundary
line,
[
ClO
2
­]
=
[
Cl­]
so
log{[
ClO
2
­]/[
Cl­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq4
=
­
109.1.
Substituting
those
values
into
eq.
4d
and
rearranging
gives
the
following
equation
for
the
ClO
2
­/
Cl­
boundary
line:

(
eq.
4e)
4
1091
4
27
3
pE
pH
pE
pH
=
 
 
=
 
.
.

(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)
(
)

(
)
(
)

(
)
(
)
(
)
f
ClO
Cl
ClO
HClO
ClO
ClO
ClO
ClO
K
Cl
H
e
Cl
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
H
e
K
H
e
K
H
e
ClO
Case
aq
eq
eq
eq
eq
eq
eq
eq
eq
eq
eq
2
2
2
2
2
3
4
4
4
4
2
2
2
3
2
4
4
4
5
4
5
6
6
6
7
8
8
4
4
4
2
2
2
3
1
 
=
+
+
+
+
+
+
=

+
+
+
+
+
+
=

+
+
 

 
 
 
 
 

 

+
 

 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 

+
 

+
 
+
(
)

(
)

(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)(
)

(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
 
+
 
+
 
+
 
+
 

 
 

 
 
 
 
 
 
 
 
 
 
 
 

 

 
+
+
+
+
=

+
+
+
+
+
+
=
2
4
4
4
5
4
5
6
6
6
7
8
8
4
4
2
2
2
4
4
4
5
6
6
8
8
109
1
10
10
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
4
2
3
4
5
6
7
K
H
e
K
H
e
K
H
e
K
H
e
eq
eq
eq
eq
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
eq
eq
eq
eq
eq
eq
eq
log
log
log
log
log
log
log
.

(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
4
4
58
1
2
2
50
6
2
109
1
4
4
126
8
4
5
147
1
6
6
187
8
8
8
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
 

 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
+
+
+
+
+
+
.
.
.
.
.
.

(
eq.
4f)
Sodium
Chlorate
Appendices
­
35
5
1268
4
254
0
8
pE
pH
pE
pH
=
 
 
=
 
.
.
.

(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)(
)

(
)
(
)

(
)
(
)
f
ClO
Cl
ClO
HClO
ClO
ClO
ClO
ClO
K
Cl
H
e
Cl
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
H
e
K
H
e
K
ClO
Case
aq
aq
eq
eq
eq
eq
eq
eq
eq
eq
eq
eq
aq
2
2
2
2
2
3
4
5
4
5
2
2
2
3
2
4
4
4
5
4
5
6
6
6
7
8
8
5
4
5
2
2
2
1
(
)(
)
(
)

(
)
=
+
+
+
+
+
+
=

+
+
+
+
+
+
=

+
+
 
 
 
 
 

 

+
 

 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 

+
 

+
 
(
)(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)

(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
3
2
4
4
4
5
4
5
6
6
6
7
8
8
4
5
2
2
2
4
4
4
5
6
6
8
8
126
10
10
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
5
2
3
4
5
6
7
H
e
K
H
e
K
H
e
K
H
e
K
H
e
eq
eq
eq
eq
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
eq
eq
eq
eq
eq
eq
eq
+
 
+
 
+
 
+
 
+
 

 
 

 
 
 
 
 
 
 
 
 
 
 
 

 
+
+
+
+
=

+
+
+
+
+
+
=
log
log
log
log
log
log
log
.

(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
8
4
5
58
1
2
2
50
6
2
109
1
4
4
126
8
4
5
147
1
6
6
187
8
8
8
10
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
 
 

 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
+
+
+
+
+
+
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
.
.
.
.
.
.
Rxn
5:
(
eq.
5a)
Cl
H
O
ClO
H
e
aq
 
+
 
+
 
+
+
2
4
5
2
2(
)

(
eq.
5b)
(
)(
)
(
)
(
)
K
ClO
H
e
Cl
eq
aq
5
2
4
5
=
+
 

 
(
)

(
eq.
5c)
[
](
)
(
)
[
]
K
ClO
H
e
Cl
mix
aq
5
2
4
5
=
+
 

 
(
)

For
generating
predominance
diagrams,
assume
that
K
eq5
~
K
mix5
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
(
)
(
)
K
K
ClO
Cl
H
e
ClO
Cl
pH
pE
eq
mix
aq
aq
5
5
2
2
4
5
4
5
 
=
+
+
=
 
 
 
+
 
 

(
eq.
5d)

Along
the
ClO
2(
aq)/
Cl­
boundary
line,
[
ClO
2(
aq)]
=
[
Cl­]
so
log{[
ClO
2(
aq)]/[
Cl­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq5
=
­
126.8.
Substituting
those
values
into
eq.
5d
and
rearranging
gives
the
following
equation
for
the
ClO
2(
aq)/
Cl­
boundary
line:

(
eq.
5e)

(
eq.
5f)
Sodium
Chlorate
Appendices
­
36
Rxn
6:
(
eq.
6a)
Cl
HO
ClO
H
e
 
 
+
 
+
 
+
+
3
6
6
2
3
(
eq.
6b)
(
)(
)
(
)
(
)
K
ClO
H
e
Cl
eq6
3
6
6
=
 
+
 

 

(
eq.
6c)
[
](
)
(
)
[
]
K
ClO
H
e
Cl
mix6
3
6
6
=
 
+
 

 

For
generating
predominance
diagrams,
assume
that
K
eq6
~
K
mix6
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
Cl
H
e
ClO
Cl
pH
pE
eq
mix
6
6
3
3
6
6
6
6
 
=
+
+
=
 
 
 

 
+
 
 

 

(
eq.
6d)

Along
the
ClO
3
­/
Cl­
boundary
line,
[
ClO
3
­]
=
[
Cl­]
so
log{[
ClO
3
­]/[
Cl­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq6
=
­
147.1.
Substituting
those
values
into
eq.
6d
and
rearranging
gives
the
following
equation
for
the
ClO
3
­/
Cl­
boundary
line:

6
1471
6
24
5
pE
pH
pE
pH
=
 
 
=
 
.
.
(
eq.
6e)

(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)

(
)
(
)

(
)
(
)
(
)
f
ClO
Cl
ClO
HClO
ClO
ClO
ClO
ClO
K
Cl
H
e
Cl
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
H
e
K
H
e
K
H
e
ClO
Case
aq
eq
eq
eq
eq
eq
eq
eq
eq
eq
eq
3
2
3
2
2
3
4
6
6
6
2
2
2
3
2
4
4
4
5
4
5
6
6
6
7
8
8
6
6
6
2
2
2
3
1
 
=
+
+
+
+
+
+
=

+
+
+
+
+
+
=

+
+
 

 
 
 
 
 

 

+
 

 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 

+
 

+
 
+
(
)

(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)(
)

(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
 
+
 
+
 
+
 
+
 

 
 

 
 
 
 
 
 
 
 
 
 
 
 

 

 
+
+
+
+
=

+
+
+
+
+
+
=
2
4
4
4
5
4
5
6
6
6
7
8
8
6
6
2
2
2
4
4
4
5
6
6
8
8
147
8
10
10
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
6
2
3
4
5
6
7
K
H
e
K
H
e
K
H
e
K
H
e
eq
eq
eq
eq
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
eq
eq
eq
eq
eq
eq
eq
log
log
log
log
log
log
log
.

(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
6
6
58
1
2
2
50
6
2
109
1
4
4
126
8
4
5
147
1
6
6
187
8
8
8
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
 

 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
+
+
+
+
+
+
.
.
.
.
.
.

(
eq.
6f)
Sodium
Chlorate
Appendices
­
37
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)
(
)(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)
(
)

(
)
(
)

(
)
(
)
(
)
f
ClO
Cl
ClO
HClO
ClO
ClO
ClO
ClO
K
Cl
H
e
Cl
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
Cl
H
e
K
H
e
K
H
e
K
H
e
ClO
Case
aq
eq
eq
eq
eq
eq
eq
eq
eq
eq
eq
4
2
4
2
2
3
4
7
8
8
2
2
2
3
2
4
4
4
5
4
5
6
6
6
7
8
8
7
8
8
2
2
2
3
1
 
=
+
+
+
+
+
+
=

+
+
+
+
+
+
=

+
+
 

 
 
 
 
 

 

+
 

 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 
 

+
 

+
 

+
 
+
(
)

(
)

(
)
(
)
(
)
(
)
(
)
(
)(
)
(
)(
)

(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
 
+
 
+
 
+
 
+
 

 
 

 
 
 
 
 
 
 
 
 
 
 
 

 

 
+
+
+
+
=

+
+
+
+
+
+
=
2
4
4
4
5
4
5
6
6
6
7
8
8
8
8
2
2
2
4
4
4
5
6
6
8
8
187
8
10
10
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
7
2
3
4
5
6
7
K
H
e
K
H
e
K
H
e
K
H
e
eq
eq
eq
eq
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
K
pH
pE
eq
eq
eq
eq
eq
eq
eq
log
log
log
log
log
log
log
.

(
)(
)

(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
(
)(
)
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
pH
pE
8
8
58
1
2
2
50
6
2
109
1
4
4
126
8
4
5
147
1
6
6
187
8
8
8
10
1
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
 

 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
 

 
 
+
+
+
+
+
+
.
.
.
.
.
.
Rxn
7:
(
eq.
7a)
Cl
H
O
ClO
H
e
 
 
+
 
+
 
+
+
4
8
8
2
4
(
eq.
7b)
(
)(
)(
)
(
)
K
ClO
H
e
Cl
eq7
4
8
8
=
 
+
 

 

(
eq.
7c)
[
](
)(
)
[
]
K
ClO
H
e
Cl
mix7
4
8
8
=
 
+
 

 

For
generating
predominance
diagrams,
assume
that
K
eq7
~
K
mix7
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
Cl
H
e
ClO
Cl
pH
pE
eq
mix
7
7
4
4
8
8
8
8
 
=
+
+
=
 
 
 

 
+
 
 

 

(
eq.
7d)

Along
the
ClO
4
­/
Cl­
boundary
line,
[
ClO
4
­]
=
[
Cl­]
so
log{[
ClO
4
­]/[
Cl­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq7
=
­
187.8.
Substituting
those
values
into
eq.
7d
and
rearranging
gives
the
following
equation
for
the
ClO
4
­/
Cl­
boundary
line:

(
eq.
7e)
8
187
8
8
235
pE
pH
pE
pH
=
 
 
=
 
.
.

(
eq.
7f)
Sodium
Chlorate
Appendices
­
38
Reactions
8
­
13
(
remaining
reactions
involving
Cl2(
aq):

Rxn
8:
(
eq.
8a)
Cl
H
O
ClO
H
e
aq
2
2
2
2
4
2
(
)+
 
+
+
 
+
 

(
eq.
8b)
(
)(
)(
)
(
)
K
ClO
H
e
Cl
eq
aq
8
2
4
2
2
=
 
+
 

(
)

(
eq.
8c)
[
](
)
(
)
[
]
K
ClO
H
e
Cl
mix
aq
8
2
4
2
2
=
 
+
 

(
)

For
generating
predominance
diagrams,
assume
that
K
eq8
~
K
mix8
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
(
)
(
)
K
K
ClO
Cl
H
e
ClO
Cl
pH
pE
eq
mix
aq
aq
8
8
2
2
2
2
4
2
4
2
 
=
+
+
=
 
 
 
+
 
 

(
eq.
8d)

Along
the
ClO­/
Cl
2(
aq)
boundary
line,
it
is
reasonable
to
assume
that
[
Cl
tot
]
~
[
ClO­]
+
2[
Cl
2(
aq)].
Therefore,
along
the
boundary
for
a
total
chlorine
concentration
[
Cl
tot
]
=
0.04
mol/
L,
[
ClO­]
~
0.02
mol/
L
and
[
Cl
2(
aq)]
~
0.01
mol/
L.
From
the
attached
thermodynamic
spreadsheet,
logK
eq8
=
­
69.0.
Substituting
those
values
into
eq.
8d
and
rearranging
gives
the
following
equation
for
the
ClO­/
Cl
2(
aq)
boundary
line:

(
eq.
8e)
[
]
[
]
2
690
002
001
4
690
14
4
676
4
2
676
4
338
2
2
pE
pH
pH
pH
pE
pH
pE
pH
=
+
 
=
 
 
=
 
 

=
 
 
=
 
.
log
.

.
.
.
.

.
.

Rxn
9:
(
eq.
9a)
Cl
H
O
HClO
H
e
aq
2
2
2
2
2
2
(
)+
 
+
+
+
 

(
eq.
9b)
(
)(
)
(
)
(
)
K
HClO
H
e
Cl
eq
aq
9
2
2
2
2
=
+
 

(
)
Sodium
Chlorate
Appendices
­
39
(
eq.
9c)
[
](
)
(
)
[
]
K
HClO
H
e
Cl
mix
aq
9
2
2
2
2
=
+
 

(
)

For
generating
predominance
diagrams,
assume
that
K
eq9
~
K
mix9
such
that
[
]

[
]
(
)
(
)
[
]

[
]
log
log
log
log
log
log
(
)
(
)
K
K
HClO
Cl
H
e
HClO
Cl
pH
pE
eq
mix
aq
aq
9
9
2
2
2
2
2
2
2
2
 
=
+
+
=
 
 
+
 

(
eq.
9d)

Along
the
HClO/
Cl
2(
aq)
boundary
line,
it
is
reasonable
to
assume
that
[
Cl
tot
]
~
[
HClO]
+
2[
Cl
2(
aq)].
Therefore,
along
the
boundary
for
a
total
chlorine
concentration
[
Cl
tot
]
=
0.04
mol/
L,
[
HClO]
~
0.02
mol/
L
and
[
Cl
2(
aq)]
~
0.01
mol/
L.
From
the
attached
thermodynamic
spreadsheet,
logK
eq9
=
­
53.9.
Substituting
those
values
into
eq.
9d
and
rearranging
gives
the
following
equation
for
the
HClO/
Cl
2(
aq)
boundary
line:

(
eq.
9e)
[
]
[
]
2
539
002
001
2
539
14
2
525
2
2
525
2
263
2
pE
pH
pH
pH
pE
pH
pE
pH
=
+
 
=
 
 
=
 
 

=
 
 
=
 
.
log
.

.
.
.
.

.
.

Rxn
10:
(
eq.
10a)
Cl
H
O
ClO
H
e
aq
2
2
2
4
2
8
6
(
)+
 
+
+
 
+
 

(
eq.
10b)
(
)(
)(
)
(
)
K
ClO
H
e
Cl
eq
aq
10
2
2
8
6
2
=
 
+
 

(
)

(
eq.
10c)
[
](
)
(
)
[
]
K
ClO
H
e
Cl
eq
aq
10
2
2
8
6
2
=
 
+
 

(
)

For
generating
predominance
diagrams,
assume
that
K
eq10
~
K
mix10
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
(
)
(
)
K
ClO
Cl
H
e
ClO
Cl
pH
pE
eq
aq
aq
10
2
2
2
2
2
2
8
6
8
6
 
+
+
 
 
 
 
+
 
 

(
eq.
10d)
Sodium
Chlorate
Appendices
­
40
Along
the
ClO
2
­
/
Cl
2(
aq)
boundary
line,
it
is
reasonable
to
assume
that
[
Cl
tot
]
~
[
ClO
2
­
]
+
2[
Cl
2(
aq)].
Therefore,
along
the
boundary
for
a
total
chlorine
concentration
[
Cl
tot
]
=
0.04
mol/
L,
[
ClO
2
­
]
~
0.02
mol/
L
and
[
Cl
2(
aq)]
~
0.01
mol/
L.
From
the
attached
thermodynamic
spreadsheet,
logK
eq10
=
­
171.1.
Substituting
those
values
into
eq.
10d
and
rearranging
gives
the
following
equation
for
the
ClO
2
­
/
Cl
2(
aq)
boundary
line:

(
eq.
10e)
[
]
[
]
6
1711
002
001
8
1711
14
8
169
7
8
6
169
7
8
28
3
133
2
pE
pH
pH
pH
pE
pH
pE
pH
=
+
 
=
 
 
=
 
 

=
 
 
=
 
.
log
.

.
.
.
.

.
.
.

Rxn
11:
(
eq.
11a)
Cl
H
O
ClO
H
e
aq
aq
2
2
2
4
2
8
8
(
)
(
)
+
 
+
+
+
 

(
eq.
11b)
(
)(
)(
)
(
)
K
ClO
H
e
Cl
eq
aq
aq
11
2
2
8
8
2
=
+
 
(
)

(
)

(
eq.
11c)
[
](
)(
)
[
]
K
ClO
H
e
Cl
mix
aq
aq
11
2
2
8
8
2
=
+
 
(
)

(
)

For
generating
predominance
diagrams,
assume
that
K
eq11
~
K
mix11
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
(
)

(
)
(
)

(
)
K
K
ClO
Cl
H
e
ClO
Cl
pH
pE
eq
mix
aq
aq
aq
aq
11
11
2
2
2
2
2
2
8
8
8
8
 
=
+
+
=
 
 
+
 

(
eq.
11d)

Along
the
ClO
2(
aq)
/
Cl
2(
aq)
boundary
line,
it
is
reasonable
to
assume
that
[
Cl
tot
]
~
[
ClO
2(
aq)
]
+
2[
Cl
2(
aq)].
Therefore,
along
the
boundary
for
a
total
chlorine
concentration
[
Cl
tot
]
=
0.04
mol/
L,
[
ClO
2(
aq)
]
~
0.02
mol/
L
and
[
Cl
2(
aq)]
~
0.01
mol/
L.
From
the
attached
thermodynamic
spreadsheet,
logK
eq11
=
­
206.3.
Substituting
those
values
into
eq.
11d
and
rearranging
gives
the
following
equation
for
the
ClO
2(
aq)
/
Cl
2(
aq)
boundary
line:
Sodium
Chlorate
Appendices
­
41
(
eq.
11e)
[
]
[
]
8
206
3
002
001
8
206
3
14
8
204
9
8
8
204
9
8
25
6
2
pE
pH
pH
pH
pE
pH
pE
pH
=
+
 
=
 
 
=
 
 

=
 
 
=
 
.
log
.

.
.
.
.

.
.

Rxn
12:
(
eq.
12a)
Cl
H
O
ClO
H
e
aq
2
2
3
6
2
12
10
(
)+
 
+
+
 
+
 

(
eq.
12b)
(
)(
)
(
)
(
)
K
ClO
H
e
Cl
eq
aq
12
3
2
12
10
2
=
 
+
 

(
)

(
eq.
12c)
[
](
)
(
)
[
]
K
ClO
H
e
Cl
mix
aq
12
3
2
12
10
2
=
 
+
 

(
)

For
generating
predominance
diagrams,
assume
that
K
eq12
~
K
mix12
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
(
)
(
)
K
K
ClO
Cl
H
e
ClO
Cl
pH
pE
eq
mix
aq
aq
12
12
3
2
2
3
2
2
12
10
12
10
 
=
+
+
=
 
 
 
+
 
 

(
eq.
12d)

Along
the
ClO
3
­
/
Cl
2(
aq)
boundary
line,
it
is
reasonable
to
assume
that
[
Cl
tot
]
~
[
ClO
3
­
]
+
2[
Cl
2(
aq)].
Therefore,
along
the
boundary
for
a
total
chlorine
concentration
[
Cl
tot
]
=
0.04
mol/
L,
[
ClO
3
­
]
~
0.02
mol/
L
and
[
Cl
2(
aq)]
~
0.01
mol/
L.
From
the
attached
thermodynamic
spreadsheet,
logK
eq12
=
­
247.0.
Substituting
those
values
into
eq.
12d
and
rearranging
gives
the
following
equation
for
the
ClO
3
­
/
Cl
2(
aq)
boundary
line:

[
]
[
]
10
247
0
002
001
12
247
0
14
12
245
6
12
10
2456
12
24
6
12
2
pE
pH
pH
pH
pE
pH
pE
pH
=
+
 
=
 
 
=
 
 

=
 
 
=
 
.
log
.

.
.
.
.

.
.
.

(
eq.
12e)

Rxn
13:
(
eq.
13a)
Cl
H
O
ClO
H
e
aq
2
2
4
8
2
16
14
(
)+
 
+
+
 
+
 
Sodium
Chlorate
Appendices
­
42
(
eq.
13b)
(
)(
)
(
)
(
)
K
ClO
H
e
Cl
eq
aq
13
4
2
16
14
2
=
 
+
 

(
)

(
eq.
13c)
[
](
)
(
)
[
]
K
ClO
H
e
Cl
mix
aq
13
4
2
16
14
2
=
 
+
 

(
)

For
generating
predominance
diagrams,
assume
that
K
eq13
~
K
mix13
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
(
)
(
)
K
K
ClO
Cl
H
e
ClO
Cl
pH
pE
eq
mix
aq
aq
13
13
4
2
2
4
2
2
16
14
16
14
 
=
+
+
=
 
 
 
+
 
 

(
eq.
13d)

Along
the
ClO
4
­
/
Cl
2(
aq)
boundary
line,
it
is
reasonable
to
assume
that
[
Cl
tot
]
~
[
ClO
4
­
]
+
2[
Cl
2(
aq)].
Therefore,
along
the
boundary
for
a
total
chlorine
concentration
[
Cl
tot
]
=
0.04
mol/
L,
[
ClO
4
­
]
~
0.02
mol/
L
and
[
Cl
2(
aq)]
~
0.01
mol/
L.
From
the
attached
thermodynamic
spreadsheet,
logK
eq13
=
­
328.3.
Substituting
those
values
into
eq.
13d
and
rearranging
gives
the
following
equation
for
the
ClO
4
­
/
Cl
2(
aq)
boundary
line:

[
]
[
]
14
328
3
002
001
16
328
3
14
16
326
9
16
14
326
9
16
234
114
2
pE
pH
pH
pH
pE
pH
pE
pH
=
+
 
=
 
 
=
 
 

=
 
 
=
 
.
log
.

.
.
.
.

.
.
.

(
eq.
13e)

Reactions
14
­
18
(
remaining
reactions
involving
ClO­):

Rxn
14:
(
eq.
14a)
ClO
H
HClO
 
+
+
 

(
eq.
14b)
(
)
(
)(
)
K
HClO
ClO
H
eq14
=
 
+

(
eq.
14c)
[
]
[
](
)
K
HClO
ClO
H
mix14
=
 
+
Sodium
Chlorate
Appendices
­
43
For
generating
predominance
diagrams,
assume
that
K
eq14
~
K
mix14
such
that
(
eq.
14d)
[
]
[
]
(
)
[
]
[
]
log
log
log
log
log
K
K
HClO
ClO
H
HClO
ClO
pH
eq
mix
14
14
 
=
 
=
+
 
+
 

Along
the
HClO/
ClO­
boundary
line,
[
HClO]
=
[
ClO­]
so
log{[
HClO]/[
ClO­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq14
=
7.6.
Substituting
the
values
into
eq.
14d
and
rearranging
gives
the
following
equation
for
the
HClO/
ClO­
boundary
line:

(
eq.
14e)
pH
=
7
6
.

Rxn
15:
(
eq.
15a)
ClO
H
O
ClO
H
e
 
 
+
 
+
 
+
+
2
2
2
2
(
eq.
15b)
(
)(
)
(
)
(
)
K
ClO
H
e
ClO
eq15
2
2
2
=
 
+
 

 

(
eq.
15c)
[
](
)
(
)
[
]
K
ClO
H
e
ClO
mix15
2
2
2
=
 
+
 

 

For
generating
predominance
diagrams,
assume
that
K
eq15
~
K
mix15
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
ClO
H
e
ClO
ClO
pH
pE
eq
mix
15
15
2
2
2
2
2
2
 
=
+
+
=
 
 
 

 
+
 
 

 

(
eq.
15d)

Along
the
ClO
2
­/
ClO­
boundary
line,
[
ClO
2
­]
=
[
ClO­]
so
log{[
ClO
2
­]/[
ClO­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq15
=
­
51.0.
Substituting
the
values
into
eq.
15d
and
rearranging
gives
the
following
equation
for
the
ClO
2
­/
ClO­
boundary
line:

(
eq.
15e)
2
510
2
255
pE
pH
pE
pH
=
 
 
=
 
.
.

Rxn
16:
(
eq.
16a)
ClO
H
O
ClO
H
e
aq
 
+
 
+
 
+
+
2
2
2
3
(
)
Sodium
Chlorate
Appendices
­
44
(
eq.
16b)
(
)(
)
(
)
(
)
K
ClO
H
e
ClO
eq
aq
16
2
2
3
=
+
 

 
(
)

(
eq.
16c)
[
](
)
(
)
[
]
K
ClO
H
e
ClO
mix
aq
16
2
2
3
=
+
 

 
(
)

For
generating
predominance
diagrams,
assume
that
K
eq16
~
K
mix16
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
(
)
(
)
K
K
ClO
ClO
H
e
ClO
ClO
pH
pE
eq
mix
aq
aq
16
16
2
2
2
3
2
3
 
=
+
+
=
 
 
 
+
 
 

(
eq.
16d)

Along
the
ClO
2(
aq)/
ClO­
boundary
line,
[
ClO
2(
aq)]
=
ClO­
so
log{[
ClO
2(
aq)]/[
ClO­]}
=
log
1
=
0.
From
the
thermodynamic
spreadsheet,
logK
eq16
=
­
68.6.
Substituting
the
values
into
eq.
16d
and
rearranging
gives
the
following
equation
for
the
ClO
2(
aq)/
ClO­
boundary
line:

(
eq.
16e)
3
68
6
2
22
9
0
67
pE
pH
pE
pH
=
 
 
=
 
.
.
.

Rxn
17:
(
eq.
17a)
ClO
HO
ClO
H
e
 
 
+
 
+
 
+
+
2
4
4
2
3
(
eq.
17b)
(
)(
)
(
)
(
)
K
ClO
H
e
ClO
eq17
3
4
4
=
 
+
 

 

(
eq.
17c)
[
](
)
(
)
[
]
K
ClO
H
e
ClO
mix17
3
4
4
=
 
+
 

 

For
generating
predominance
diagrams,
assume
that
K
eq17
~
K
mix17
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
ClO
H
e
ClO
ClO
pH
pE
eq
mix
17
17
3
3
4
4
4
4
 
=
+
+
=
 
 
 

 
+
 
 

 

(
eq.
17d)
Sodium
Chlorate
Appendices
­
45
Along
the
ClO
3
­/
ClO­
boundary
line,
[
ClO
3
­]
=
[
ClO­]
so
log{[
ClO
3
­]/[
ClO­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq17
=
­
89.0.
Substituting
those
values
into
eq.
17d
and
rearranging
gives
the
following
equation
for
the
ClO
3
­/
ClO­
boundary
line:

(
eq.
17e)
4
89
0
4
22
3
pE
pH
pE
pH
=
 
 
=
 
.
.

Rxn
18:
(
eq.
18a)
ClO
H
O
ClO
H
e
 
 
+
 
+
 
+
+
3
6
6
2
4
(
eq.
18b)
(
)(
)
(
)
(
)
K
ClO
H
e
ClO
eq18
4
6
6
=
 
+
 

 

(
eq.
18c)
[
](
)
(
)
[
]
K
ClO
H
e
ClO
mix18
4
6
6
=
 
+
 

 

For
generating
predominance
diagrams,
assume
that
K
eq18
~
K
mix18
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
ClO
H
e
ClO
ClO
pH
pE
eq
mix
18
18
4
4
6
6
6
6
 
=
+
+
=
 
 
 

 
+
 
 

 

(
eq.
18d)

Along
the
ClO
4
­/
ClO­
boundary
line,
[
ClO
4
­]
=
[
ClO­]
so
log{[
ClO
4
­]/[
ClO­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq18
=
­
129.7.
Substituting
those
values
into
eq.
18d
and
rearranging
gives
the
following
equation
for
the
ClO
4
­/
ClO­
boundary
line:

(
eq.
18e)
6
129
7
6
216
pE
pH
pE
pH
=
 
 
=
 
.
.

Reactions
19
­
22
(
remaining
reactions
involving
HClO):

Rxn
19:
(
eq.
19a)
HClO
H
O
ClO
H
e
+
 
+
+
 
+
 
2
2
3
2
(
eq.
19b)
(
)(
)(
)
(
)
K
ClO
H
e
HClO
eq19
2
3
2
=
 
+
 
Sodium
Chlorate
Appendices
­
46
(
eq.
19c)
[
](
)(
)
[
]
K
ClO
H
e
HClO
mix19
2
3
2
=
 
+
 

For
generating
predominance
diagrams,
assume
that
K
eq19
~
K
mix19
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
HClO
H
e
ClO
HClO
pH
pE
eq
mix
19
19
2
2
3
2
3
2
 
=
+
+
=
 
 
 
+
 
 

(
eq.
19d)

Along
the
ClO
2
­
/
HClO
boundary
line,
[
ClO
2
­]
=
[
HClO]
so
log{[
ClO
2
­]/[
HClO]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq19
=
­
58.6.
Substituting
the
values
into
eq.
19d
and
rearranging
gives
the
following
equation
for
the
ClO
2
­
/
HClO
boundary
line:

(
eq.
19e)
2
58
6
3
29
3
15
pE
pH
pE
pH
=
 
 
=
 
.
.
.

Rxn
20:
(
eq.
20a)
HClO
H
O
ClO
H
e
aq
+
 
+
++
 
2
2
3
3
(
)

(
eq.
20b)
(
)(
)(
)
(
)
K
ClO
H
e
HClO
eq
aq
20
2
3
3
=
+
 
(
)

(
eq.
20c)
[
](
)(
)
[
]
K
ClO
H
e
HClO
mix
aq
20
2
3
3
=
+
 
(
)

For
generating
predominance
diagrams,
assume
that
K
eq20
~
K
mix20
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
(
)
(
)
K
K
ClO
HClO
H
e
ClO
HClO
pH
pE
eq
mix
aq
aq
20
20
2
2
3
3
3
3
 
=
+
+
=
 
 
+
 

(
eq.
20d)

Along
the
ClO
2(
aq)
/
HClO
boundary
line,
[
ClO
2(
aq)]
=
[
HClO]
so
log{[
ClO
2(
aq)]/[
HClO]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq20
=
­
76.2.
Substituting
the
values
into
eq.
20d
and
rearranging
gives
the
following
equation
for
the
ClO
2(
aq)
/
HClO
boundary
line:

(
eq.
20e)
3
76
2
3
254
pE
pH
pE
pH
=
 
 
=
 
.
.
Sodium
Chlorate
Appendices
­
47
Rxn
21:
(
eq.
21a)
HClO
H
O
ClO
H
e
+
 
+
+
 
+
 
2
5
4
2
3
(
eq.
21b)
(
)(
)(
)
(
)
K
ClO
H
e
HClO
eq21
3
5
4
=
 
+
 

(
eq.
21c)
[
](
)(
)
[
]
K
ClO
H
e
HClO
mix21
3
5
4
=
 
+
 

For
generating
predominance
diagrams,
assume
that
K
eq21
~
K
mix21
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
HClO
H
e
ClO
HClO
pH
pE
eq
mix
21
21
3
3
5
4
5
4
 
=
+
+
=
 
 
 
+
 
 

(
eq.
21d)

Along
the
ClO
3
­
/
HClO
boundary
line,
[
ClO
3
­]
=
[
HClO]
so
log{[
ClO
3
­]/[
HClO]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq21
=
­
96.6.
Substituting
the
values
into
eq.
21d
and
rearranging
gives
the
following
equation
for
the
ClO
3
­
/
HClO
boundary
line:

(
eq.
21e)
4
96
6
5
24
2
125
pE
pH
pE
pH
=
 
 
=
 
.
.
.

Rxn
22:
(
eq.
22a)
HClO
H
O
ClO
H
e
+
 
+
+
 
+
 
3
7
6
2
4
(
eq.
22b)
(
)(
)
(
)
(
)
K
ClO
H
e
HClO
eq22
4
7
6
=
 
+
 

(
eq.
22c)
[
](
)
(
)
[
]
K
ClO
H
e
HClO
mix22
4
7
6
=
 
+
 

For
generating
predominance
diagrams,
assume
that
K
eq22
~
K
mix22
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
HClO
H
e
ClO
HClO
pH
pE
eq
mix
22
22
4
4
7
6
7
6
 
=
+
+
=
 
 
 
+
 
 

(
eq.
22d)
Sodium
Chlorate
Appendices
­
48
Along
the
ClO
4
­
/
HClO
boundary
line,
[
ClO
4
­]
=
[
HClO]
so
log{[
ClO
4
­]/[
HClO]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq22
=
­
137.2.
Substituting
the
values
into
eq.
22c
and
rearranging
gives
the
following
equation
for
the
ClO
4
­
/
HClO
boundary
line:

(
eq.
22e)
6
137
2
7
22
9
117
pE
pH
pE
pH
=
 
 
=
 
.
.
.

Reactions
23
­
25
(
remaining
reactions
involving
ClO2
­
):

Rxn
23:
(
eq.
23a)
ClO
ClO
e
aq
2
2
 
 
 
+
(
)

(
eq.
23b)
(
)(
)
(
)
K
ClO
e
ClO
eq
aq
23
2
2
=
 

 
(
)

(
eq.
23c)
[
](
)
[
]
K
ClO
e
ClO
mix
aq
23
2
2
=
 

 
(
)

For
generating
predominance
diagrams,
assume
that
K
eq23
~
K
mix23
such
that
[
]
[
]
(
)
[
]
[
]
log
log
log
log
log
(
)
(
)
K
K
ClO
ClO
e
ClO
ClO
pE
eq
mix
aq
aq
23
23
2
2
2
2
 
=
+
=
 
 
 
 

(
eq.
23d)

Along
the
ClO
2(
aq)
/
ClO
2
­
boundary
line,
[
ClO
2(
aq)]
=
[
ClO
2
­]
so
log{[
ClO
2(
aq)]/[
ClO
2
­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq23
=
­
17.6.
Substituting
the
values
into
eq.
23d
and
rearranging
gives
the
following
equation
for
the
ClO
2(
aq)
/
ClO
2
­
boundary
line:

(
eq.
23e)
pE
=
17
6
.

Rxn
24:
(
eq.
24a)
ClO
HO
ClO
H
e
2
2
3
2
2
 
 
+
 
+
 
+
+

(
eq.
24b)
(
)(
)
(
)
(
)
K
ClO
H
e
ClO
eq24
3
2
2
2
=
 
+
 

 
Sodium
Chlorate
Appendices
­
49
(
eq.
24c)
[
](
)
(
)
[
]
K
ClO
H
e
ClO
mix24
3
2
2
2
=
 
+
 

 

For
generating
predominance
diagrams,
assume
that
K
eq24
~
K
mix24
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
ClO
H
e
ClO
ClO
pH
pE
eq
mix
24
24
3
2
3
2
2
2
2
2
 
=
+
+
=
 
 
 

 
+
 
 

 

(
eq.
24d)

Along
the
ClO
3
­
/
ClO
2
­
boundary
line,
[
ClO
3
­]
=
[
ClO
2
­]
so
log{[
ClO
3
­]/[
ClO
2
­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq24
=
­
38.0.
Substituting
the
values
into
eq.
24d
and
rearranging
gives
the
following
equation
for
the
ClO
3
­
/
ClO
2
­
boundary
line:

(
eq.
24e)
2
38
0
2
19
0
pE
pH
pE
pH
=
 
 
=
 
.
.

Rxn
25:
(
eq.
25a)
ClO
HO
ClO
H
e
2
2
4
2
4
4
 
 
+
 
+
 
+
+

(
eq.
25b)
(
)(
)
(
)
(
)
K
ClO
H
e
ClO
eq25
4
4
4
2
=
 
+
 

 

(
eq.
25c)
[
](
)
(
)
[
]
K
ClO
H
e
ClO
mix25
4
4
4
2
=
 
+
 

 

For
generating
predominance
diagrams,
assume
that
K
eq25
~
K
mix25
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
ClO
H
e
ClO
ClO
pH
pE
eq
mix
25
25
4
2
4
2
4
4
4
4
 
=
+
+
=
 
 
 

 
+
 
 

 

(
eq.
25d)

Along
the
ClO
4
­
/
ClO
2
­
boundary
line,
[
ClO
4
­]
=
[
ClO
2
­]
so
log{[
ClO
4
­]/[
ClO
2
­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq25
=
­
78.6.
Substituting
the
values
into
eq.
25c
and
rearranging
gives
the
following
equation
for
the
ClO
4
­
/
ClO
2
­
boundary
line:

(
eq.
25e)
4
78
6
4
19
7
pE
pH
pE
pH
=
 
 
=
 
.
.
Sodium
Chlorate
Appendices
­
50
Reactions
26
­
27
(
remaining
reactions
involving
ClO2(
aq)
):

Rxn
26:
(
eq.
26a)
ClO
H
O
ClO
H
e
aq
2
2
3
2
(
)+
 
+
+
 
+
 

(
eq.
26b)
(
)(
)
(
)
(
)
K
ClO
H
e
ClO
eq
aq
26
3
2
2
=
 
+
 

(
)

(
eq.
26c)
[
](
)
(
)
[
]
K
ClO
H
e
ClO
mix
aq
26
3
2
2
=
 
+
 

(
)

For
generating
predominance
diagrams,
assume
that
K
eq26
~
K
mix26
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
(
)
(
)
K
K
ClO
ClO
H
e
ClO
ClO
pH
pE
eq
mix
aq
aq
26
26
3
2
3
2
2
2
 
=
+
+
=
 
 
 
+
 
 

(
eq.
26d)

Along
the
ClO
3
­
/
ClO
2(
aq)
boundary
line,
[
ClO
3
­]
=
[
ClO
2(
aq)]
so
log{[
ClO
3
­]/[
ClO
2(
aq)]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq26
=
­
20.4.
Substituting
the
values
into
eq.
26d
and
rearranging
gives
the
following
equation
for
the
ClO
3
­
/
ClO
2(
aq)
boundary
line:

(
eq.
26e)
pE
pH
=
 
20
4
2
.

Rxn
27:
(
eq.
27a)
ClO
H
O
ClO
H
e
aq
2
2
4
2
4
3
(
)+
 
+
+
 
+
 

(
eq.
27b)
(
)(
)
(
)
(
)
K
ClO
H
e
ClO
eq
aq
27
4
4
3
2
=
 
+
 

(
)

(
eq.
27c)
[
](
)
(
)
[
]
K
ClO
H
e
ClO
mix
aq
27
4
4
3
2
=
 
+
 

(
)

For
generating
predominance
diagrams,
assume
that
K
eq27
~
K
mix27
such
that
Sodium
Chlorate
Appendices
­
51
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
(
)
(
)
K
K
ClO
ClO
H
e
ClO
ClO
pH
pE
eq
mix
aq
aq
27
27
4
2
4
2
4
3
4
3
 
=
+
+
=
 
 
 
+
 
 

(
eq.
27d)

Along
the
ClO
4
­
/
ClO
2(
aq)
boundary
line,
[
ClO
4
­]
=
[
ClO
2(
aq)]
so
log{[
ClO
4
­]/[
ClO
2(
aq)]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq27
=
­
61.0.
Substituting
the
values
into
eq.
27d
and
rearranging
gives
the
following
equation
for
the
ClO
4
­
/
ClO
2(
aq)
boundary
line:

(
eq.
27e)
3
610
4
20
3
133
pE
pH
pE
pH
=
 
 
=
 
.
.
.

Reaction
28
(
last
remaining
reaction
involving
ClO3
­
):

Rxn
28:
(
eq.
28a)
ClO
H
O
ClO
H
e
3
2
4
2
2
 
 
+
 
+
 
+
+

(
eq.
28b)
(
)(
)
(
)
(
)
K
ClO
H
e
ClO
eq28
4
2
2
3
=
 
+
 

 

(
eq.
28c)
[
](
)
(
)
[
]
K
ClO
H
e
ClO
mix28
4
2
2
3
=
 
+
 

 

For
generating
predominance
diagrams,
assume
that
K
eq28
~
K
mix28
such
that
[
]
[
]
(
)
(
)
[
]
[
]
log
log
log
log
log
log
K
K
ClO
ClO
H
e
ClO
ClO
pH
pE
eq
mix
28
28
4
3
4
3
2
2
2
2
 
=
+
+
=
 
 
 

 
+
 
 

 

(
eq.
28d)

Along
the
ClO
4
­
/
ClO
3
­
boundary
line,
[
ClO
4
­]
=
[
ClO
3
­]
so
log{[
ClO
4
­]/[
ClO
3
­]}
=
log
1
=
0.
From
the
attached
thermodynamic
spreadsheet,
logK
eq28
=
­
40.6.
Substituting
the
values
into
eq.
28d
and
rearranging
gives
the
following
equation
for
the
ClO
4
­
/
ClO
3
boundary
line:

(
eq.
28e)
2
40
6
2
20
3
pE
pH
pE
pH
=
 
 
=
 
.
.

See
Next
Page
Sodium
Chlorate
Appendices
­
52
Water
oxidation
and
reduction
reactions
(
Benjamin
2002):

Rxn
1W
Oxidation
of
Water:
(
eq.
1Wa)
2
4
4
2
2
H
O
O
H
e
g
 
+
++
 
(
)

(
eq.
1Wb)
(
)(
)
(
)
K
O
H
e
eqW
aq
1
2
4
4
=
+
 
(
)

(
)
(
)
(
)
(
)
log
log
log
log
log
(
)
(
)
K
O
H
e
O
pH
pE
eqW
g
g
1
2
2
4
4
4
4
=
+
+
=
 
 
+
 

(
eq.
1Wc)

(
eq.
1Wd)
(
)
4
831
021
4
206
pE
pH
pE
pH
=
+
 
 
=
 
.
log
.
.

Rxn
2W
Reduction
of
Water:
(
eq.
2Wa)
2
2
2
2
2
H
O
e
H
OH
g
+
 
+
 
 
(
)

(
eq.
2Wb)
(
)(
)
(
)
K
H
OH
e
eqW
g
2
2
2
2
=
 

 
(
)

(
)
(
)
(
)
(
)
(
)
log
log
log(
)
log
log
log
(
)
log
(
)
(
)

(
)
(
)
K
H
OH
e
H
pOH
pE
H
pH
pE
H
pH
pE
eqW
g
g
g
g
2
2
2
2
2
2
2
2
2
2
14
2
2
2
28
=
+
 
=
 
+
=

 
 
+
=
+
+
 
 
 

(
eq.
2Wc)

(
eq.
2Wd)
(
)
2
5
10
2
2
6
30
2
32
7
pE
pH
pE
pH
pE
pH
=
 
×
 
 
=
 

 
=
 
 
log
.

.
Sodium
Chlorate
Appendices
­
53
Attachment
B:
Computations
of
delta
G0
of
reactions
and
equilbrium
constants
for
aqueous
chlorine
species
reactions
and
for
oxidation
and
reduction
of
water
reactions.
(
Spreadsheet
format
developed
by
Dr.
Jim
Hetrick).

Reactants
#
mols
delG0
form
delG0
reacts
Products
#
mols
delG0
form
delG0
prods
delG0
rxn
logKeq
Rxn
1
Cl­
2
­
131.3
­
262.6
Cl2(
aq)
1
6.9
6.9
0
e­
2
0
0
0
­
262.6
6.9
269.5
­
47.2
Rxn
2
Cl­
1
­
131.3
­
131.3
ClO­
1
­
36.8
­
36.8
H2O
1
­
237.18
­
237.18
H+
2
0
0
e­
2
0
0
Sum(
rea):
­
368.48
Sum(
pro):
­
36.8
331.7
­
58.1
Rxn
3
Cl­
1
­
131.3
­
131.3
HClO
1
­
79.9
­
79.9
H2O
1
­
237.18
­
237.18
H+
1
0
0
e­
2
0
0
Sum(
rea):
­
368.48
Sum(
pro):
­
79.9
288.6
­
50.6
Rxn
4
Cl­
1
­
131.3
­
131.3
ClO2
­
1
17.1
17.1
H2O
2
­
237.18
­
474.36
H+
4
0
0
e­
4
0
0
Sum(
rea):
­
605.66
Sum(
pro):
17.1
622.8
­
109.1
Rxn
5
Cl­
1
­
131.3
­
131.3
ClO2(
aq)
1
117.6
117.6
H2O
2
­
237.18
­
474.36
H+
4
0
0
e­
5
0
0
Sum(
rea):
­
605.66
Sum(
pro):
117.6
723.3
­
126.8
Rxn
6
Cl­
1
­
131.3
­
131.3
ClO3
­
1
­
3.35
­
3.35
H2O
3
­
237.18
­
711.54
H+
6
0
0
e­
6
0
0
Sum(
rea):
­
842.84
Sum(
pro):
­
3.35
839.5
­
147.1
Rxn
7
Cl­
1
­
131.3
­
131.3
ClO4­
1
­
8.62
­
8.62
H2O
4
­
237.18
­
948.72
H+
8
0
0
e­
8
0
0
Sum(
rea):
­
1080.02
Sum(
pro):
­
8.62
1071.4
­
187.8
Rxn
8
Cl2(
aq)
1
6.9
6.9
ClO­
2
­
36.8
­
73.6
H2O
2
­
237.18
­
474.36
H+
4
0
0
e­
2
0
0
Sum(
rea):
­
467.46
Sum(
pro):
­
73.6
393.9
­
69.0
Rxn
9
Cl2(
aq)
1
6.9
6.9
HClO
2
­
79.9
­
159.8
H2O
2
­
237.18
­
474.36
H+
2
0
0
e­
2
0
0
Sum(
rea):
­
467.46
Sum(
pro):
­
159.8
307.7
­
53.9
Rxn
10
Cl2(
aq)
1
6.9
6.9
ClO2
­
2
17.1
34.2
H2O
4
­
237.18
­
948.72
H+
8
0
0
e­
6
0
0
Sum(
rea):
­
941.82
Sum(
pro):
34.2
976.0
­
171.1
Attachment
C
to
Appendix
B­
2:
Charts
1b
through
1e
Sodium
Chlorate
Appendices
­
54
Rxn
11
Cl2(
aq)
1
6.9
6.9
ClO2(
aq)
2
117.6
235.2
H2O
4
­
237.18
­
948.72
H
+
8
0
0
e
­
8
0
0
Sum(
rea):
­
941.82
Sum(
pro):
235.2
1177.0
­
206.3
Rxn
12
Cl2(
aq)
1
6.9
6.9
ClO3
­
2
­
3.35
­
6.7
H2O
6
­
237.18
­
1423.08
H
+
12
0
0
e
­
10
0
0
Sum(
rea):
­
1416.18
Sum(
pro):
­
6.7
1409.5
­
247.0
Rxn
13
Cl2(
aq)
1
6.9
6.9
ClO4
­
2
­
8.62
­
17.24
H2O
8
­
237.18
­
1897.44
H
+
16
0
0
e
­
14
0
0
Sum(
rea):
­
1890.54
Sum(
pro):
­
17.24
1873.3
­
328.3
Rxn
14
ClO
­
1
­
36.8
­
36.8
HClO
1
­
79.9
­
79.9
H
+
1
0
0
Sum(
rea):
­
36.8
Sum(
pro):
­
79.9
­
43.1
7.6
Rxn
15
ClO
­
1
­
36.8
­
36.8
ClO2
­
1
17.1
17.1
H2O
1
­
237.18
­
237.18
H
+
2
0
0
e
­
2
0
0
Sum(
rea):
­
273.98
Sum(
pro):
17.1
291.1
­
51.0
Rxn
16
ClO
­
1
­
36.8
­
36.8
ClO2(
aq)
1
117.6
117.6
H2O
1
­
237.18
­
237.18
H
+
2
0
0
e
­
3
0
0
Sum(
rea):
­
273.98
Sum(
pro):
117.6
391.6
­
68.6
Rxn
17
ClO
­
1
­
36.8
­
36.8
ClO3
­
1
­
3.35
­
3.35
H2O
2
­
237.18
­
474.36
H
+
4
0
0
e
­
4
0
0
Sum(
rea):
­
511.16
Sum(
pro):
­
3.35
507.8
­
89.0
Rxn
18
ClO
­
1
­
36.8
­
36.8
ClO4
­
1
­
8.62
­
8.62
H2O
3
­
237.18
­
711.54
H
+
6
0
0
e
­
6
0
0
­
748.34
­
8.62
739.7
­
129.6
Rxn
19
HClO
1
­
79.9
­
79.9
ClO2
­
1
17.1
17.1
H2O
1
­
237.18
­
237.18
H
+
3
0
0
e
­
2
0
0
Sum(
rea):
­
317.08
Sum(
pro):
17.1
334.2
­
58.6
Rxn
20
HClO
1
­
79.9
­
79.9
ClO2(
aq)
1
117.6
117.6
H2O
1
­
237.18
­
237.18
H
+
3
0
0
e
­
3
0
0
Sum(
rea):
­
317.08
Sum(
pro):
117.6
434.7
­
76.2
Sodium
Chlorate
Appendices
­
55
Rxn
21
HClO
1
­
79.9
­
79.9
ClO3
­
1
­
3.35
­
3.35
H2O
2
­
237.18
­
474.36
H
+
5
0
0
e
­
4
0
0
Sum(
rea):
­
554.26
Sum(
pro):
­
3.35
550.9
­
96.6
Rxn
22
HClO
1
­
79.9
­
79.9
ClO4
­
1
­
8.62
­
8.62
H2O
3
­
237.18
­
711.54
H
+
7
0
0
e
­
6
0
0
Sum(
rea):
­
791.44
Sum(
pro):
­
8.62
782.8
­
137.2
Rxn
23
ClO2
­
1
17.1
17.1ClO2(
aq)
1
117.6
117.6
0
e
­
1
0
0
0
17.1
117.6
100.5
­
17.6
Rxn
24
ClO2
­
1
17.1
17.1ClO3
­
1
­
3.35
­
3.35
H2O
1
­
237.18
­
237.18
H
+
2
0
0
e
­
2
0
0
Sum(
rea):
­
220.08
Sum(
pro):
­
3.35
216.7
­
38.0
Rxn
25
ClO2
­
1
17.1
17.1ClO4
­
1
­
8.62
­
8.62
H2O
2
­
237.18
­
474.36
H
+
4
0
0
e
­
4
0
0
Sum(
rea):
­
457.26
Sum(
pro):
­
8.62
448.6
­
78.6
Rxn
26
ClO2(
aq)
1
117.6
117.6
ClO3
­
1
­
3.35
­
3.35
H2O
1
­
237.18
­
237.18
H
+
2
0
0
e
­
1
0
0
Sum(
rea):
­
119.58
Sum(
pro):
­
3.35
116.2
­
20.4
Rxn
27
ClO2(
aq)
1
117.6
117.6
ClO4
­
1
­
8.62
­
8.62
H2O
2
­
237.18
­
474.36
H
+
4
0
0
e
­
3
0
0
Sum(
rea):
­
356.76
Sum(
pro):
­
8.62
348.1
­
61.0
Rxn
28
ClO3
­
1
­
3.35
­
3.35
ClO4
­
1
­
8.62
­
8.62
H2O
1
­
237.18
­
237.18
H
+
2
0
0
e
­
2
0
0
Sum(
rea):
­
240.53
Sum(
pro):
­
8.62
231.9
­
40.6
Rxn
H2O
2
­
237.18
­
474.36
O2(
g)
1
0
0
1W
H
+
4
0
0
e
­
4
0
0
Sum(
rea):
­
474.36
Sum(
pro):
0
474.4
­
83.1
Rxn
H2O
2
­
237.18
­
474.36
H2(
g)
1
0
0
2W
e
­
2
0
OH
­
2
­
157.3
­
314.6
0
Sum(
rea):
­
474.36
Sum(
pro):
­
314.6
159.8
­
28.0
Sodium
Chlorate
Appendices
­
56
Attachment
C
to
Appendix
B­
2:
Charts
1b
through
1e
Sodium
Chlorate
Appendices
­
57
Chart
1b:
Case
1
Cl­
predominance
(
below
bolded
lines)
considering
only
Cl­,
Cl2(
aq),
ClO­,
and
HClO.

10
12
14
16
18
20
22
24
26
28
30
32
34
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
pH
pE
2a
3b
2b
3c
1a
1b
3a
2)
ClO
­/
Cl
­
3)
HClO/
Cl
­
1)
Cl2(
aq)/
Cl
­

Cl
­
predominance
Sodium
Chlorate
Appendices
­
58
Chart
1c:
Case
1
Cl2(
aq)
predominance
considering
only
Cl­,
Cl2(
aq),
ClO­,
and
HClO.

0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
pH
pE
1a
1b
8a
9a
9b
9c
8b
8)
ClO
­/
Cl2(
aq)
9)
HClO/
Cl2(
aq)
1)
Cl2(
aq)/
Cl
­

Cl2(
aq)
predominance
Sodium
Chlorate
Appendices
­
59
Chart
1d:
Case
1
ClO­
predominance
(
enclosed
by
bolded
lines)
considering
only
Cl­,
Cl2(
aq),
ClO­,
and
HClO.

5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
pH
pE
2a
2b
14a
14b
8
2)
ClO
­/
Cl
­
14)
HClO/
ClO
­

ClO
­
predominance
8)
ClO
­/
Cl2(
aq)
Sodium
Chlorate
Appendices
­
60
Chart
1c:
Case
1
Cl2(
aq)
predominance
considering
only
Cl­,
Cl2(
aq),
ClO­,
and
HClO.

0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
pH
pE
1a
1b
8a
9a
9b
9c
8b
8)
ClO
­/
Cl2(
aq)
9)
HClO/
Cl2(
aq)
1)
Cl2(
aq)/
Cl
­

Cl2(
aq)
predominance
Chart
1e:
Case
1
HClO
predominance
(
enclosed
by
bolded
lines)
considering
only
Cl­,
Cl2(
aq),
ClO­,
and
HClO.

10
12
14
16
18
20
22
24
26
28
30
32
34
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
pH
pE
3b
14a
3c
14b
9a
9b
3a
3)
HClO/
Cl
­
14)
HClO/
ClO
­

HClO
predominance
9)
HClO/
Cl2(
aq)
Sodium
Chlorate
Appendices
­
61
Attachment
D
to
Appendix
B­
2.
Charts
3b
to
3i.
Sodium
Chlorate
Appendices
­
62
Chart
3b:
Case
2
Cl­
predominance
(
below
the
bolded
line)
considering
Cl­,
Cl2(
aq),
HClO,
ClO­,

ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.

10
12
14
16
18
20
22
24
26
28
30
2
3
4
5
6
7
8
9
10
11
12
pH
pE
2
3
4
5
6
7
1
2)
ClO
­/
Cl
­

3)
HClO/
Cl
­
4)
ClO2
­/
Cl
­

5)
ClO2(
aq)/
Cl
­

6)
ClO3
­/
Cl
­

7)
ClO4
­/
Cl
­
1)
Cl2(
aq)/
Cl
­

Cl
­
predominance
Sodium
Chlorate
Appendices
­
63
Chart
3c:
Case
2
Cl2(
aq)
predominance
(
none
­
no
overlap
between
Cl2(
aq)
regions
above
and
below
bolded
lines)
considering
Cl­,
Cl2(
aq),
ClO­,
HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.

5
7
9
11
13
15
17
19
21
23
25
27
29
2
3
4
5
6
7
8
9
10
11
12
pH
pE
1
8
9
10
11
12
13
1)
Cl2(
aq)/
Cl
­
8)
ClO
­/
Cl2(
aq)

9)
HClO/
Cl2(
aq)
10)
ClO2
­/
Cl2(
aq)

11)
ClO2(
aq)/
Cl2(
aq)

12)
ClO3
­/
Cl2(
aq)
13)
ClO4
­

/
Cl
Cl2(
aq)
predominance
?
No
­
no
overlap
with
region
below
bolded
line
13
Cl2(
aq)
predominance
?
No
­
no
overlap
with
region
above
bolded
line
1
Sodium
Chlorate
Appendices
­
64
Chart
3d:
Case
2
ClO­
predominance
(
none
­
no
overlap
between
ClO­
regions
bordered
by
bolded
lines)
considering
Cl­,
Cl2(
aq),
ClO­,
HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­

5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
2
3
4
5
6
7
8
9
10
11
12
pH
pE
2a
14a
15
16
17
18a
2b
14b
14c
18b
8
2)
ClO
­/
Cl
­
14)
HClO/
ClO
­

15)
ClO2
­/
ClO
­
16)
ClO2(
aq)/
Cl
O
­

17)
ClO3
­/
ClO
­
18)
ClO4
­/
ClO
­
8)
ClO
­/
Cl2(
aq)
ClO
­
predominance
?
No
­
no
overlap
with
mirror
region
below
ClO
­
predominance
?
No
­
no
overlap
with
mirror
region
above
Sodium
Chlorate
Appendices
­
65
Chart
3e:
Case
2
HClO
predominance
(
none
­
no
overlap
between
HClO
regions
bordered
by
bolded
lines)
considering
Cl­,
Cl2(
aq)
ClO­,
HClO,
ClO2
­,
ClO3
­,
and
ClO4
­.

5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
2
3
4
5
6
7
8
9
10
11
12
pH
pE
3a
14a
19
20
21
22a
3b
22b
14b
14c
9
3)
HClO/
Cl­
14)
HClO/
ClO­

19)
ClO
2
­/
HClO
20)
ClO
2(
aq)/
HClO
21)
ClO
3
­/
HClO
22)
ClO
4
­/
HClO
HClO
predominance
?
No
­
no
overlap
w
ith
similar
region
below
9)
HClO/
Cl
2(
aq)

HClO
predominance
?
No
­
no
overlap
w
ith
similar
region
above
Sodium
Chlorate
Appendices
­
66
Chart
3f:
Case
2
ClO2
­
predominance
(
none
­
no
overlap
between
ClO2
­
regions
above
and
below
bolded
lines)
considering
Cl­,
Cl2(
aq),
ClO­,
HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.

5
7
9
11
13
15
17
19
21
23
25
2
3
4
5
6
7
8
9
10
11
12
pH
pE
15
23
24
25
4
19
10
4)
ClO2
­/
Cl
­
15)
ClO2
­

­

23)
ClO2(
aq)/
ClO2
­

19)
ClO2
­/
HClO
25)
ClO4
­/
ClO2
­
24)
ClO3
­/
ClO2
­

10)
ClO2
­/
Cl2(
aq)
ClO2
­
predominance
?
No
­
no
overlap
with
region
below
bolded
line
24
ClO2
­
predominance
?
No
­
no
overlap
with
region
above
bolded
line
4
Sodium
Chlorate
Appendices
­
67
Chart
3g:
Case
2
ClO2(
aq)
predominance
(
none
­
no
overlap
between
ClO2(
aq)
regions
above
and
below
bolded
lines)
considering
Cl­,
Cl2(
aq),
ClO­,
HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.

­
5
­
3
­
1
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
2
3
4
5
6
7
8
9
10
11
12
pH
pE
5a
16
20
23a
26
27
5b
23b
11
5)
ClO2(
aq)/
Cl
­

16)
ClO2(
aq)/
ClO
­
20)
ClO2(
aq)/
HClO
23)
ClO2(
aq)/
ClO2
­

26)
ClO3
­

/
ClO
27)
ClO4
­/
ClO2(
aq)
11)
ClO2(
aq)/
Cl2(
aq)
ClO2(
aq)
predominance
?
No
­
no
overlap
with
region
below
bolded
line
26
ClO2(
aq)
predominance
?
No
­
no
overlap
with
region
above
bolded
portions
of
lines
5
&
23
Sodium
Chlorate
Appendices
­
68
Chart
3h:
Case
2
ClO3
­
predominance
(
none
­
no
overlap
between
ClO3
­
regions
above
and
below
bolded
lines)
considering
Cl­,
Cl2(
aq),
ClO­,
HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.

­
10
­
8
­
6
­
4
­
2
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
2
3
4
5
6
7
8
9
10
11
12
pH
pE
6
17
21
24
26
28
12
17)
ClO3
­/
ClO
­

21)
ClO3
­/
HClO
24)
ClO3
­/
ClO2
­
6)
ClO3
­/
Cl
­

26)
ClO3
­/
ClO2(
aq)
28)
ClO4
­/
ClO3
­

12)
ClO3
­/
Cl2(
aq)
ClO3
­
predominance
?
No
­
no
overlap
with
region
below
bolded
line
28
ClO3
­
predominance
?
No
­
no
overlap
with
region
above
bolded
line
6
Sodium
Chlorate
Appendices
­
69
Chart
3i:
Case
2
ClO4
­
predominance
(
above
the
bolded
line)
considering
Cl­,
Cl2(
aq),
ClO­,

HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.

0
2
4
6
8
10
12
14
16
18
20
22
24
2
3
4
5
6
7
8
9
10
11
12
pH
pE
7
18
22
25
27
28
13
7)
ClO4
­/
Cl
­

18)
ClO4
­/
ClO
­

25)
ClO4
­/
ClO2
­
22)
ClO4
­/
HClO
28)
ClO4
­/
ClO3
­

27)
ClO4
­/
ClO2(
aq)

13)
ClO4
­

/
Cl
ClO4
­
predominance
Sodium
Chlorate
Appendices
­
70
Attachment
E
to
Appendix
B­
2.
Charts
4c
to
4g
Sodium
Chlorate
Appendices
­
71
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
­
2
­
4
­
6
­
8
­
10
4
6
8
10
0
5E­
13
1E­
12
1.5E­
12
2E­
12
2.5E­
12
3E­
12
3.5E­
12
ClO­
Activity
Ratio
pE
pH
Chart
4c:
Case
2
ClO­
Activity
ratio
considering
Cl­,
ClO­,
HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.

3E­
12­
4E­
12
3E­
12­
3E­
12
2E­
12­
3E­
12
2E­
12­
2E­
12
1E­
12­
2E­
12
5E­
13­
1E­
12
0­
5E­
13
Sodium
Chlorate
Appendices
­
72
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
­
2
­
4
­
6
­
8
­
10
4
8
0.0E+
00
1.0E­
09
2.0E­
09
3.0E­
09
4.0E­
09
5.0E­
09
6.0E­
09
7.0E­
09
8.0E­
09
9.0E­
09
1.0E­
08
HClO
Activity
Ratio
pE
pH
Chart
4d:
Case
2
HClO
Activity
ratio
considering
Cl­,
ClO­,
HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.
Sodium
Chlorate
Appendices
­
73
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
­
2
­
4
­
6
­
8
­
10
4
8
0.00E+
00
5.00E­
17
1.00E­
16
1.50E­
16
2.00E­
16
2.50E­
16
3.00E­
16
3.50E­
16
ClO2
­
Activity
Fraction
pE
pH
Chart
4e:
Case
2
ClO2
­
Activity
fraction
considering
Cl­,
ClO­,
HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.

3E­
16­
4E­
16
3E­
16­
3E­
16
2E­
16­
3E­
16
2E­
16­
2E­
16
1E­
16­
2E­
16
5E­
17­
1E­
16
0­
5E­
17
Sodium
Chlorate
Appendices
­
74
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
­
2
­
4
­
6
­
8
­
10
4
8
0.0E+
00
2.0E­
15
4.0E­
15
6.0E­
15
8.0E­
15
1.0E­
14
1.2E­
14
1.4E­
14
1.6E­
14
1.8E­
14
2.0E­
14
ClO2(
aq)
Activity
Fraction
pE
pH
Chart
4f:
Case
2
ClO2(
aq)
Activity
fraction
considering
Cl­,
ClO­,
HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.

1.8E­
14­
2E­
14
1.6E­
14­
1.8E­
14
1.4E­
14­
1.6E­
14
1.2E­
14­
1.4E­
14
1E­
14­
1.2E­
14
8E­
15­
1E­
14
6E­
15­
8E­
15
4E­
15­
6E­
15
2E­
15­
4E­
15
0­
2E­
15
Sodium
Chlorate
Appendices
­
75
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
­
2
­
4
­
6
­
8
­
10
4
9
0.0E+
00
5.0E­
08
1.0E­
07
1.5E­
07
2.0E­
07
2.5E­
07
3.0E­
07
3.5E­
07
ClO3
­
Activity
Fraction
pE
pH
Chart
4g:
Case
2
ClO3
­
Activity
fraction
considering
Cl­,
ClO­,
HClO,
ClO2
­,
ClO2(
aq),
ClO3
­,
and
ClO4
­.

0.0000003­
0.00000035
0.00000025­
0.0000003
0.0000002­
0.00000025
0.00000015­
0.0000002
0.0000001­
0.00000015
0.00000005­
0.0000001
0­
0.00000005
Sodium
Chlorate
Appendices
­
76
Appendix
C.
Areas
in
the
United
States
That
Grow
Selected
Commodities
on
Which
Sodium
Chlorate
Is
Used
Sodium
Chlorate
Appendices
­
77
Sodium
Chlorate
Appendices
­
78
Sodium
Chlorate
Appendices
­
79
Sodium
Chlorate
Appendices
­
80
Sodium
Chlorate
Appendices
­
81
Sodium
Chlorate
Appendices
­
82
Sodium
Chlorate
Appendices
­
83
Sodium
Chlorate
Appendices
­
84
Sodium
Chlorate
Appendices
­
85
Appendix
D.
Percent
of
Irrigated
Acres
Estimated
for
Cotton
53
The
maturity
of
the
crop
is
measured
in
terms
of
the
maturity
of
the
bolls
and
depends
on
the
time
of
the
year
when
cotton
was
set.
Boll
maturity
is
determined
by
visual
observation
of
bolls
in
the
field
intended
for
harvest
Sodium
Chlorate
Appendices
­
86
Cotton
Sodium
chlorate
is
used
on
cotton
as
a
harvest
aid
(
defoliant,
desiccant,
or
both).
Timing
of
use
as
a
defoliant
depends
on:
(
a)
Maturity
of
the
crop;
(
b)
Condition
of
the
crop;
(
c)
Prevailing
weather
conditions
and
(
d)
Harvest
schedule.
However,
timing
depends
mainly
on
maturity
of
the
bolls53
and
harvest
schedule.
Too
late
defoliation
can
increase
the
likehood
of
rot
bolls
and
fiber
damage.
Lower
temperatures
as
the
Fall
season
progresses
(
i.
e.,
below
60
°
F;
<
16
°
C)
may
inhibit
the
activity
of
defoliant.
In
general,
good
conditions
for
defoliation
are
high
temperature,
high
humidity,
low
wind
velocity,
and
high
to
adequate
soil
moisture.
Stressed
cotton
by
drought
or
retarded
growth
from
cold
weather
can
result
in
unsatisfactory
defoliation.
Therefore,
there
is
a
temporal
and
spatial
variability
in
the
timing
of
application
of
sodium
chlorate.
Thus,
this
spatial
and
temporal
variability
reflects
also
on
the
environmental
fate
of
chlorate
(
refer
to
the
"
Environmental
Fate"
section).

Cotton
constitutes
the
crop
of
most
extensive
use
of
sodium
chlorate,
at
about
90%
of
the
total
use
of
this
chemical
on
agricultural
commodities.
However,
not
all
of
the
harvested
cotton
may
use
sodium
chlorate
as
a
harvest
aid.
Table
D­
1
summarizes
the
number
of
harvested
acres
(
in
descending
order
of
total
harvested
acreage)
in
the
major
cotton
growing
states.
The
Table
also
includes
the
percent
of
crops
that
is
irrigated.
Note
that
all
Pima
cotton
is
irrigated,
but
the
percent
of
irrigated
upland
cotton
varies
with
region.
The
lowest
percent
of
irrigation
is
in
some
eastern
and
south
eastern
states
(
FL,
VA,
SC,
TN,
AL).

Table
D­
1.
Cotton
Production
(
Harvest
Acres)
and
Percent
of
Irrigated
Acreage
(
Source;
USDA,
Census
of
Agriculture,
2002)

State
Upland
Cotton,
Acres
Harvested
Upland
Cotton,
%
Irrigated
Pima
Cotton
Acres
Harvested
Pima
Cotton
%
Irrigated
Texas
4,638,240
40
18,789
100
Georgia
1,267,150
26
None
None
Mississippi
1,157,432
35
None
None
North
Carolina
924,097
2.5
None
None
Arkansas
921,316
77
None
None
Tennessee
533,755
1.8
None
None
Alabama
523,123
6.2
None
None
California
495,943
100
198,710
100
Louisiana
474,784
32
None
None
State
Upland
Cotton,
Acres
Harvested
Upland
Cotton,
%
Irrigated
Pima
Cotton
Acres
Harvested
Pima
Cotton
%
Irrigated
Sodium
Chlorate
Appendices
­
87
Missouri
395,880
52
None
None
Arizona
214,880
100
7,842
100
South
Carolina
208,420
7
None
None
Oklahoma
172,228
39
None
None
Florida
101,766
8
None
None
Virginia
Kansas
New
Mexico
92,809
55,953
45,994
0.9
45
100
None
None
NM
7,051
None
None
100
Sodium
Chlorate
Appendices
­
88
Appendix
E.
Maximum
Labeled
Application
Rates
and
Crops
for
all
Agricultural
End­
Use
Products
Sodium
Chlorate
Appendices
­
89
Table
E­
1.
Maximum
Labeled
Application
Rates
and
Crops
for
all
Agricultural
End­
Use
Products
Label
Crop
Application
rate
(
lbs
a.
i./
Acre)
Application
method
Helena
2
lb.
Sodium
chlorate
defoliantdesiccant
Cotton
5
Aerial
or
ground
Second
application
may
be
required
for
cotton
Grain
6
Helena
3
lb.
Sodium
chlorate
defoliantdesiccant
Chili
Peppers
7.5
Aerial
or
ground
Corn,
beans,
flas,
grain
sorghum,
guar
beans,
rice,
safflowers,
southern
peas,
soybeans,
sunflower
6
Cotton
4.5
Helena
6
lb
sodium
chlorate
defoliant
desiccant
Dry
beans,
guar
beans,
flax,
corn,
rice,
safflower,
soybeans,
sunflower
6
Aerial
or
ground
Chili
peppers
7.5
Cotton,
grain
sorghum
4.5
Leafex
2
defoliantdesiccant
Cotton
5.3
(
Arizona)
4.7
(
all
other
states)
Allows
no
more
than
two
applications
(
reapplication
interval
not
specified)

Leafex
3
defoliantdesiccant
Cotton
5.25
(
Arizona)
4
(
all
other
states)
Allows
no
more
than
two
applications
(
reapplication
interval
not
specified)

Grain
sorghum,
corn,
rice,
soybean,
sunflower
6
Maximum
number
of
applications
not
specified
Shed­
a­
leaf
"
L"
Cotton
3.75
Ground
or
aerial
Rice
(
MS
only)
4.5
Soybean
(
MS
only),
6
Riverside
sodium
chlorate
Corn
6
Aerial
Cotton
3.75
Ground
or
aerial
Dry
beans,
grain
sorghum,
safflower,
southern
peas,
soybeans,
sunflower
6
Ground
or
aerial
Table
E­
1.
Maximum
Labeled
Application
Rates
and
Crops
for
all
Agricultural
End­
Use
Products
Label
Crop
Application
rate
(
lbs
a.
i./
Acre)
Application
method
Sodium
Chlorate
Appendices
­
90
Rice
6
Aerial
Sodium
chlorate
6
Dry
beans,
grain
sorghum,
guar
beans,
safflower,
southern
peas,
soybeans,
sunflower
6
Ground
or
aerial
Corn,
flax,
rice
6
Aerial
Cotton
4.5
Ground
or
aerial
Chili
peppers
7.5
Ground
or
aerial
D­
Leaf­
M
cotton
defoliant
Cotton
4
Ground
or
aerial
Britz
cotton
defoliant
concentrate
Cotton
4.58
Ground
or
aerial
First
choice
cotton
defoliant
concentrate
Cotton
5.52
Ground
or
aerial
Chili
peppers
9.2
Ground
or
aerial
Grain
sorghum
4.97
Ground
or
aerial
Drexel
Defol
Chili
peppers
7.5
Ground
or
aerial
Corn,
rice
6
Aerial
Cotton
4.5
Ground
or
aerial
Dry
beans,
flas,
grain
sorghum,
guar
beans,
potatoes,
safflower,
southern
peas,
soybeans,
sunflower
6
Ground
or
aerial
Ornamental
gourds
6
Georgia
only
Ground
or
aerial
Drexel
Defol
6
Chili
peppers
7.5
Ground
or
aerial
Corn,
rice
6
Aerial
Cotton
4.5
Ground
or
aerial
Table
E­
1.
Maximum
Labeled
Application
Rates
and
Crops
for
all
Agricultural
End­
Use
Products
Label
Crop
Application
rate
(
lbs
a.
i./
Acre)
Application
method
Sodium
Chlorate
Appendices
­
91
Dry
beans,
flax,
cucurbits,
grain
sorghum,
guar
beans,
potatoes,
safflower,
southern
peas,
soybeans,
sunflower
6
Ground
or
aerial
Drexel
Defol
6W
Chili
peppers
7.5
Ground
or
aerial
Corn,
rice
6
Aerial
Cotton
4.5
Ground
or
aerial
Dry
beans,
flax,
cucurbits,
grain
sorghum,
guar
beans,
potatoes,
safflower,
southern
peas,
soybeans,
sunflower,
fallow
ground
6
Ground
or
aerial
Drexel
defol
5
Chili
peppers
7.5
Ground
or
aerial
Corn,
rice
6
Aerial
Cotton
4.5
Ground
or
aerial
Dry
beans,
flax,
cucurbits,
grain
sorghum,
guar
beans,
potatoes,
safflower,
southern
peas,
soybeans,
sunflower
6
Ground
or
aerial
Drexel
defol
750
Chili
peppers
7.5
Ground
or
aerial
Corn,
rice
6
Aerial
Cotton
4.5
Ground
or
aerial
Dry
beans,
flax,
cucurbits,
grain
sorghum,
guar
beans,
potatoes,
safflower,
southern
peas,
soybeans,
sunflower
6
Ground
or
aerial
Clean
crop
sodium
chlorate
Cotton
4.5
Ground
or
aerial
Table
E­
1.
Maximum
Labeled
Application
Rates
and
Crops
for
all
Agricultural
End­
Use
Products
Label
Crop
Application
rate
(
lbs
a.
i./
Acre)
Application
method
Sodium
Chlorate
Appendices
­
92
Grain
sorghum,
safflower,
soybeans,
sunflower,
rice
6
Ground
or
aerial
(
except
rice
­
aerial
only)
California
restriction
on
safflower,
soybeans,
sunflower
MAPCO
brand
poly
foliant
Cotton
5.76
Ground
or
aerial
Moore
AG
Brand
Poly­
Foliant
Dry
beans,
guar
beans,
cotton,
flax,
grain
sorghum,
corn,
rice,
safflower,
soybean,
sunflower,
southern
peas
7.5
Ground
or
aerial
Chili
peppers,
potatoes
12.5
Ground
or
aerial
Flax,
corn,
rice
7.5
Aerial
Pick­
Mor
Cotton
4.7
Ground
or
aerial
Sodium
Chlorate
Appendices
­
93
Appendix
F.
Estimated
Average
Percent
Crop
Treated
for
Sodium
Chlorate
on
Selected
Crops
Sodium
Chlorate
Appendices
­
94
Estimate
of
Average
Percent
Crop
Treated
(
PCT)
for
Sodlium
Chlorate
on
Selected
Crops
Alan
Halvorson,
BEAD/
EAB,
10/
26/
04
Avg
PCT
Data
Source
Beans,
Lima,
Fresh
<
1%
Source
(
1):
1998
&
2000
Beans,
Lima,
Process
2%
Source
(
1):
2000
Beans,
Snap
<
1%
Source
(
1):
1998,
2000
&
2002,
and
source
(
3)

Beans/
Peas,
Dry
<
1%
Source
(
3)

Corn,
Field
<
1%
Source
(
2):
1998
­
2003,
and
source
(
3)

Corn,
Sweet
<
1%
Source
(
1):
1998,
2000
&
2002,
and
source
(
3)

Cotton
5%
SLUA
with
data
for
1998
­
2002,
and
source
(
2):
2003
Flax
<
1%
Source
(
3)

Guar
­
No
data
available
Peas,
Green
<
1%
Source
(
1):
1998,
2000
&
2002,
and
source
(
3)

Peppers,
Non­
Bell
<
1%
Source
(
1):
1998,
2000
&
2002,
and
source
(
3)

Potatoes
<
1%
SLUA
with
data
for
1998
­
2002
and
source
(
2):
2003
Rice
<
1%
SLUA
with
data
1998
­
2002
Safflower
2%
Source
(
4)

Sorghum
<
1%
Source
(
2):
1998
&
2003,
and
source
(
3)

Soybeans
<
1%
Source
(
2):
1998
&
2003
Sunflower
<
1%
Source
(
2):
1999,
and
source
(
3)

Wheat
<
1%
Source
(
2):
1998,
2000
&
2002,
and
source
(
3)

Data
Sources:

(
1)
USDA/
NASS
Agricultural
Chemical
Usage:
Vegetables
(
2)
USDA/
NASS
Agricultural
Chemical
Usage:
Field
Crops
(
3)
EPA
proprietary
usage
data,
1998
­
2003
(
4)
CA
DPR,
California
Use
Reports,
2000
­
2002
Sodium
Chlorate
Appendices
­
95
Appendix
G:
Description
of
the
Risk
Quotient
Method
Sodium
Chlorate
Appendices
­
96
The
Risk
Quotient
Method
is
the
means
used
by
EFED
to
integrate
the
results
of
exposure
and
ecotoxicity
data.
For
this
method,
risk
quotients
(
RQs)
are
calculated
by
dividing
exposure
estimates
by
ecotoxicity
values
(
i.
e.,
RQ
=
EXPOSURE/
TOXICITY),
both
acute
and
chronic.
These
RQs
are
then
compared
to
OPP's
levels
of
concern
(
LOCs).
These
LOCs
are
criteria
used
by
OPP
to
indicate
potential
risk
to
non­
target
organisms
and
the
need
to
consider
regulatory
action.
EFED
has
defined
LOCs
for
acute
risk,
potential
restricted
use
classification,
and
for
endangered
species.

The
criteria
indicate
that
a
pesticide
used
as
directed
has
the
potential
to
cause
adverse
effects
on
nontarget
organisms.
LOCs
currently
address
the
following
risk
presumption
categories:
(
1)
acute
­
there
is
a
potential
for
acute
risk;
regulatory
action
may
be
warranted
in
addition
to
restricted
use
classification;
(
2)
acute
restricted
use
­
the
potential
for
acute
risk
is
high,
but
this
may
be
mitigated
through
restricted
use
classification
(
3)
acute
endangered
species
­
the
potential
for
acute
risk
to
endangered
species
is
high,
regulatory
action
may
be
warranted,
and
(
4)
chronic
risk
­
the
potential
for
chronic
risk
is
high,
regulatory
action
may
be
warranted.
Currently,
EFED
does
not
perform
assessments
for
chronic
risk
to
plants,
acute
or
chronic
risks
to
non­
target
insects,
or
chronic
risk
from
granular/
bait
formulations
to
mammalian
or
avian
species.

The
ecotoxicity
test
values
(
i.
e.,
measurement
endpoints)
used
in
the
acute
and
chronic
risk
quotients
are
derived
from
required
studies.
Examples
of
ecotoxicity
values
derived
from
shortterm
laboratory
studies
that
assess
acute
effects
are:
(
1)
LC
50
(
fish
and
birds),
(
2)
LD
50
(
birds
and
mammals),
(
3)
EC
50
(
aquatic
plants
and
aquatic
invertebrates),
and
(
4)
EC
25
(
terrestrial
plants).
Examples
of
toxicity
test
effect
levels
derived
from
the
results
of
long­
term
laboratory
studies
that
assess
chronic
effects
are:
(
1)
LOAEL
(
birds,
fish,
and
aquatic
invertebrates),
and
(
2)
NOAEL
(
birds,
fish
and
aquatic
invertebrates).
The
NOAEL
is
generally
used
as
the
ecotoxicity
test
value
in
assessing
chronic
effects.

Risk
presumptions,
along
with
the
corresponding
RQs
and
LOCs
are
summarized
in
Table
G­
1.
Sodium
Chlorate
Appendices
­
97
Table
G­
1:
Risk
Presumptions
and
LOCs
Risk
Presumption
RQ
LOC
Birds1
Acute
Risk
EEC/
LC
50
or
LD
50
/
sqft
or
LD
50
/
day
0.5
Acute
Restricted
Use
EEC/
LC
50
or
LD
50
/
sqft
or
LD
50
/
day
(
or
LD
50
<
50
mg/
kg)
0.2
Acute
Endangered
Species
EEC/
LC
50
or
LD
50
/
sqft
or
LD
50
/
day
0.1
Chronic
Risk
EEC/
NOAEC
1
Wild
Mammals1
Acute
Risk
EEC/
LC
50
or
LD
50
/
sqft
or
LD
50
/
day
0.5
Acute
Restricted
Use
EEC/
LC
50
or
LD
50
/
sqft
or
LD
50
/
day
(
or
LD
50
<
50
mg/
kg)
0.2
Acute
Endangered
Species
EEC/
LC
50
or
LD
50
/
sqft
or
LD
50
/
day
0.1
Chronic
Risk
EEC/
NOAEC
1
Aquatic
Animals2
Acute
Risk
EEC/
LC
50
or
EC
50
0.5
Acute
Restricted
Use
EEC/
LC
50
or
EC
50
0.1
Acute
Endangered
Species
EEC/
LC
50
or
EC
50
0.05
Chronic
Risk
EEC/
NOAEC
1
Terrestrial
and
Semi­
Aquatic
Plants
Acute
Risk
EEC/
EC
25
1
Acute
Endangered
Species
EEC/
EC
05
or
NOAEC
1
Aquatic
Plants2
Acute
Risk
EEC/
EC
50
1
Acute
Endangered
Species
EEC/
EC
05
or
NOAEC
1
1
LD
50
/
sqft
=
(
mg/
sqft)
/
(
LD
50
*
wt.
of
animal)
LD
50
/
day
=
(
mg
of
toxicant
consumed/
day)
/
(
LD
50
*
wt.
of
animal)

2
EEC
=
(
ppm
or
ppb)
in
water
Sodium
Chlorate
Appendices
­
98
Appendix
H.
Discussion
of
Waived
Environmental
Fate
Data
Sodium
Chlorate
Appendices
­
99
Hydrolysis
(
161­
1)
(
Abiotic
Hydrolysis)
The
chemistry
of
chlorate
in
water
is
dominated
by
redox
reactions
that
require
the
presence
of
reductants
(
inorganic
and/
or
organic).
Because
the
161­
1
Hydrolysis
study
is
conducted
in
abiotic
media
and
in
types
of
buffer
solutions
that
are
not
likely
to
act
as
reductants,
this
study
was
waived
as
it
was
concluded
that
the
study
was
not
going
provide
any
useful
or
very
limited
information,
unless
known
environmental
reductants
were
included
in
the
aqueous
media.
Moreover,
the
redox
chemistry
of
chlorate
in
water
is
extensively
documented
in
the
chemical
literature.

Photodegradation
in
water
(
161­
2)
(
Direct
Photolysis)
The
161­
2
study
is
conducted
in
the
absence
of
chemical
photosensitizers.
That
is,
this
study
is
designed
to
address
the
role
of
direct
photolysis
in
aqueous
media.
A
necessary,
but
not
sufficient,
condition
for
direct
photolysis
in
environmentally
significant
aqueous
media
is
that
the
chemical
must
absorb
energy
(
photon)
in
the
sunlight
wavelength
range.
Chlorate
does
not
absorb
energy
in
this
range.
Therefore,
the
161­
2
study
was
waived
because
it
does
not
the
necessary
condition
for
direct
photolysis..

Photodegradation
on
soil
(
161­
3)
This
study
was
waived
because
the
combined
soil
sterilization
and
variability
in
nature
and
concentration
of
reductants
in
soil
are
not
likely
to
provide
data
that
can
identify
that
photolysis
on
soil
contributes
to
the
degradation
of
chlorate.

Note:
Photoreactions
induced
by
transfer
of
energy
from
photosensitizers
in
natural
water
and
soils
may
contribute
to
the
transformation
of
chlorate
in
the
environment
(
that
is,
indirect
photolysis
contribution).
Many
chemical
reductants
present
in
natural
environments
may
also
behave
as
photoreductants.

Anaerobic/
aerobic
aquatic
metabolism
(
162­
3/
162­
4)
and
Aerobic/
Anaerobic
soil
metabolism
(
162­
1/­
2)
These
studies
would
not
likely
produce
useful
information
due
to
sodium
chlorate
antimicrobial
properties
that
destroy
the
microbial
populations
in
soil
and
water­
sediment
systems.
If
the
microbial
population
is
destroyed,
the
study
cannot
adequately
address
the
role
of
microorganisms
in
the
degradation
of
chlorate.

Mobility
in
soil
(
163­
1)
Sodium
chlorate
is
fully
ionized
in
water.
The
chlorate
anion
is
not
likely
to
adsorb
onto
soils
or
sediments.
Therefore,
high
mobility
was
anticipated.
Guideline
studies
would
not
provide
additional
information.

Bioaccumulation
in
fish
(
165­
4)
The
estimated
log
n­
octanol
water
partition
coefficient
is
­
7
(
i.
e.,
it
is
a
highly
hydrophilic
chemical)
Therefore,
the
n­
octanol
water
partition
coefficient
does
not
trigger
the
need
for
a
165­
4
study.
54
There
are
no
direct
applications
to
water
bodies
for
uses
as
an
herbicide.
However,
sodium
chlorate
can
be
used
to
generate
chlorine
dioxide
in
situ,
which
is
used
as
an
antimicrobial
agent
in
drinking
water
disinfection
and
in
microorganism
control
in
water
cooling
systems.
The
focus
of
the
present
ecological
risk
assessment
is
solely
for
the
terrestrial
field
uses
of
sodium
chlorate.
Aquatic
uses
are
regulated
under
the
jurisdiction
of
the
Antimicrobial
Division
and
Office
of
Water.

Sodium
Chlorate
Appendices
­
100
Aquatic
field
dissipation
(
164­
2)

There
are
no
direct
applications
of
sodium
chlorate
to
water
bodies
(
aquatic
field).
Therefore,
this
study
is
not
required54.
Sodium
Chlorate
Appendices
­
101
Appendix
I.
Impact
of
sodium
from
sodium
chlorate
on
soil
quality
(
soil
dispersion).
Sodium
Chlorate
Appendices
­
102
The
analysis
was
designed
to
assess
the
sodium
adsorption
ratio
(
SAR)
in
acid­
near
neutral
and
alkaline
soils.
These
conditions
were
selected
because
they
represent
two
different
soil
chemical
equilibrium
conditions
for
Ca
and
Mg,
major
competing
cations
on
soil
adsorption
sites.
Under
the
acid­
near
neutral
soil
conditions,
the
Ca
and
Mg
activities
in
soil
solution
are
likely
controlled
simple
cation
exchange.
These
activities
are
described
in
chemical
equilibrium
terms
as
soil­
Ca
and
soil­
Mg.
Under
alkaline
conditions,
the
Ca
and
Mg
activities
in
soil
solution
are
expected
to
be
controlled
by
calcite
(
CaCO
3
)
and
dolomite
(
MgCO
3
)
(
Lindsay,
1978).
The
sodium
activity
in
soil
solution
(
under
ideal
conditions)
was
assumed
to
be
controlled
by
the
sodium
chlorate
application
rate.

Predicted
Na
Concentration
in
soil
solution
Assumption:

A
soil
bulk
density
of
1.3
g/
cc,
20%
field
capacity­­
the
Na
concentration
in
soil
solution
=
6.74
mg/
L=
2.933E­
4
moles/
L=
0.29
moles/
m3
Predicted
Ca
Concentration
in
Soil
Solution:

Acidic
and
Near­
Neutral
Soil=
Soil­
Ca­
Ca
(
log
K=­
2.5)=
Ca
activity=
0.003
moles/
L=
3
moles/
m3
Alkaline
Soil
(
Assuming
CaCO
3
equilibria)=
CaCO
3
+
2H+­
Ca
2+
+
C0
2
(
g)
+
H
2
0
(
Log
K=
9.74)
(
log
Ca
2+
=
9.74
­
2pH
­
log
CO
2
(
g))
At
CO
2
(
g)
=
0.0003
atm
and
pH=
8.5
=
Ca
activity=
0.00018
moles/
liters=
0.18197
moles/
m3
At
CO
2
(
g)=
0.003
atm
and
pH=
8.5=
Ca
activity=
0.000018
moles/
liter=
0.018197
moles/
m3
Predicted
Mg
Concentration
in
Soil
Solution
Acidic
and
Neutral
Soil=
Soil­
Mg­
Mg
(
log
K=­
3.00)=
Mg
activity=
0.001
moles/
liter=
1
mole/
m3
Alkaline
Conditions
(
Assume
equilibrium
with
calcite
and
dolomite)
MgCa(
CO
3
)
+
2H+­
Mg
2+
+
CO
2
(
g)
+
H
2
O
+
CaCO
3
(
Log
K=
8.72)
(
log
Mg
2+=
8.72­
logC0
2
(
g)­
2pH)

At
CO
2
(
g)=
0.0003
atm
and
pH
8.5
=
1.7
x
10­
5
mole/
L=
0.01737
moles/
m3
At
CO
2
(
g)=
0.003
atm
and
pH
8.5
=
1.7X
10­
6
moles/
L=
0.001737
moles/
m3
Predicted
Na
concentration
in
Soil
Solution
Sodium
Chlorate
Appendices
­
103
Using
the
SAR
equation=
Na/(
Ca+
Mg)^
1/
2
(
Sposito,
1989)

Acid­
Near
Neutral
Soil
Conditions
SAR
(
acid/
neutral
soils)=
0.29/(
3+
1)^
1/
2=
0.145
Alkaline
Soils
(
pH
8.5)
and
CO
2
(
g)=
0.0003
SAR
(
alkaline,
pC02=
3.52)=
0.29/(
0.18197+
0.01737)^
1/
2=
0.29/
0.44=
0.6590
Alkaline
Soils
(
pH
8.5)
and
CO
2
(
g)=
0.003
SAR
(
alkaline,
pCO2=
2.52)=
0.29/
0.018197
+
0.001737)^
1/
2=
0.29/
0.14=
2.07
Sodium
Chlorate
Appendices
­
104
Appendix
J.
Discussion
on
Chlorate
Redox
Chemistry
as
it
Relates
to
Exposure
to
Aquatic
Organisms
in
the
Environment
55
See
"
Water
Chlorination:
Chemistry,
Environmental
Impact
and
Health
Effects",
Volume
5.
Edited
by
Jolley,
R.
L.,
et
al.
Lewis
Publishers,
1985.

56
See
http://
www.
epa.
gov/
oppefed1/
models/
water/
index.
htm
57
"
Standard
Potentials
in
Aqueous
Solutions",
Edited
by
A.
J.
Bard,
R.
Parsons,
and
J.
Jordan
for
the
International
Union
of
Pure
and
Applied
Chemistry,
Physical
and
Analytical
Chemistry
Divisions,
Commissions
on
Electrochemistry
and
Electroanalytical
Chemistry.
Published
by
Marcel
Dekker,
New
York,
1985.

Sodium
Chlorate
Appendices
­
105
Although
there
are
some
models55
available
that
are
used
in
water
chlorination,
they
are
not
suitable
for
uses
that
have
a
direct
application
to
a
terrestrial
environment
(
i.
e.,
environmental
conditions
for
chlorination
in
water
treatment
plants
are
markedly
different
than
those
found
in
terrestrial
environments).

Because
the
chlorate
chemistry
is
highly
dependent
on
pH­
pE
(
redox)
conditions
in
the
environment,
these
factors
need
to
be
considered
in
modeling
the
environmental
fate
and
transport
of
chlorate.
One
problem
is
that
environmental
fate
and
transport
models
for
pesticides
(
GENEEC,
SCI­
GROW,
FIRST,
PRZM)
do
not
have
the
capability
to
quantitatively
assess
the
impact
of
environmental
redox
potentials
(
pH­
pE)
on
chemical
speciation.
Although
the
EXAMS
component
of
PRZM­
EXAMS
has
the
capability
to
use
redox
potential
as
an
input
parameter
with
specific
chemical
species,
it
also
needs
kinetics
data
(
which
is
difficult
to
obtain
for
redox
systems
such
as
the
chlorine)
56
.
Moreover,
even
if
the
kinetics
data
were
available,
the
nature
and
predominance
(
relative
concentrations)
of
reduction
products
cannot
be
obtained
using
EXAMS.

Further
refinement
of
the
exposure
assessment
was
conducted
to
investigate
the
impact
of
redox
conditions
on
the
distribution
of
chemical
speciation
of
chlorine
including:
(
1))
Chlorate,
ClO
3
­;
Cl(
V);
(
2)
Chlorite,
ClO
2
­;
Cl
(
III);
Hypochlorite,
ClO­
;
Cl
(
I);
and
Chloride,
ClO­;
Cl
(­
I).

A
chemical
equilibrium
modeling
approach
was
used
as
a
first
approximation
on
the
distribution
of
chemical
species
of
chlorine
as
function
redox
potential.
This
approach,
however,
does
not
consider
reaction
kinetics.
Reaction
kinetics
have
been
shown
to
be
an
important
consideration
in
determining
the
stability
of
chlorate
(
ClO
3
­)
in
soil
and
aquatic
environments
(
see
reference).
As
discussed
in
3.1.1,
reaction
kinetics
of
the
chlorine
system
is
extremely
complex
and
most
of
data
comes
from
study
conditions
that
are
not
relevant
to
conditions
found
in
the
environment.
However,
thermodynamic
data
is
readily
available
and
was
obtained
from
peer­
reviewed
data
included
in
publications
widely
used
as
reference
(
see
Appendix
A)
57
A
mole
fraction
diagram
for
chlorate
and
redox
species
for
the
reactions
was
constructed
to
show
the
relative
predominance
of
chlorine
species
as
function
of
redox
potential
(
Figure
1).
This
exercise
demonstrated
that
chlorate
(
ClO
3
­)
and
chlorite
(
Cl0
2
­)
under
equilibrium
conditions
are
not
expected
to
be
predominant
Cl
species
under
normal
environmental
redox
potentials
(
pe+
pH<
17).
Hypochlorite
was
the
predominant
Cl
species
pe+
pH
>
~
17,
which
is
outside
the
environmentally
significant
pe
+
pH
range.
As
expected,
the
chloride
ion
(
Cl­)
was
the
Sodium
Chlorate
Appendices
­
106
pe
+
pH
2
4
6
8
10
12
14
16
18
20
Mole
Fraction
0
20
40
60
80
100
CL02
­

CL0
­

Cl­
NO3
­
­
N02
­

Fe
+
3
­
Fe
+
2
SO4+
2­
vs
S­
2
predominant
Cl
species
under
normal
environmental
redox
potentials
(
pe+
pH
<
17)
These
data
suggest
that
chlorate
and
chlorite
are
not
expected
to
be
stable
under
normal
environmental
redox
conditions
in
surface
water.
This
assessment,
however,
assumes
the
kinetics
of
reactions
do
not
control
the
rates
of
reduction
and
oxidation
of
the
various
chloride
species.
As
previously
discussed,
the
nature
and
concentration
of
redox
species
in
natural
water
should
also
be
taken
into
account.
However,
given
the
extensive
spatial
and
temporal
variability
of
redox
species
in
natural
water,
a
quantitative
assessment
cannot
be
performed.

Both
the
mole
fraction
and
the
activity
fraction
diagrams
(
Appendix
B­
2)
showed
that,
at
thermodynamic
equilibrium,
chloride
is
the
predominant
chlorine
chemical
species
under
environmental
conditions.
The
fraction
diagram
is
illustrated
in
Figure
J­
1
below.
Sodium
Chlorate
Appendices
­
107
Appendix
K.
Terrestrial
EECs
for
the
Maximum
Labeled
Application
Rates
for
all
of
Sodium
Chlorate's
Current
End­
Use
Products
Sodium
Chlorate
Appendices
­
108
Table
K.
Calculated
EECs
(
mg
ai/
kg­
food
item)
for
Terrestrial
Animal
Risk
Assessment
(
Non­
agricultural
Uses)

Use
Application
rate
(
lbs
a.
i./
Acre)
Predicted
90th
Percentile
Residue
Levels
(
ppm)
Predicted
Mean
Residue
Levels
(
ppm)

short
grass
tall
grass
broadleaf
forage,

small
insects
fruit,
pods,
seeds,

small
insects
short
grass
tall
grass
broadleaf
forage,

small
insects
fruit,
pods,
seeds,

small
insects
Industrial
sites
such
as
driveways,
paths,

brick
walks,
cobble
gutters,
tennis
courts
52
12500
5700
7000
780
4400
1900
2300
360
Driveways,
parking
lots,
walks,
around
fences,
curbs,
similar
areas.
Not
for
use
on
lawns.
140
33600
15400
18900
2100
11900
5040
6300
980
Fence
rows,
rights­
of­
ways
and
similar
areas;
Around
buildings,
storage
areas,
fences,

recreational
areas,
guard
rails,
highway
medians,
industrial
sites;

Around
buildings,
storage
areas,
fences,

pumps,
machinery,
fuel
tanks,
recreational
areas,
roadways,
guard
rails,
airports,
rights
of
ways.
160
38400
17600
21600
2400
13600
5760
7200
1120
Driveways,
walks,
patios,
tennis
courts,

curbs,
garages,
etc.
220
52800
24200
29700
3300
18700
7920
9900
1540
Table
K.
Calculated
EECs
(
mg
ai/
kg­
food
item)
for
Terrestrial
Animal
Risk
Assessment
(
Non­
agricultural
Uses)

Sodium
Chlorate
Appendices
­
109
Industrial
sites,
rights
of
way,
lumberyards,

petroleum
tank
farms,
around
farm
buildings,
along
fence
lines,
and
similar
areas;
Bleachers,
fence
lines,
fire
hydrants,
helo
pads,
parking
lots,
runways,
vacant
lots.
240
57600
26400
32400
3600
20400
8640
10800
1680
Brick
walks,
patios,
parking
areas,
along
fences,
curbs,
gutters,
around
building,

graveled
pathways,
driveways,
under
asphalt
paving
330
79200
36300
44550
4950
28050
11880
14850
2310
Bleachers,
bridge
abutments,
buildings,

guard
rails,
helo
pads,
under
asphalt,

concrete,
gravel,
driveways,
sidewalks,

wood
decks.
390
93600
42900
52650
5850
33150
14040
17550
2730
Parking
lots,
under
asphalt
paving,
fence
lines,
building
perimeters,
ditch
banks,

picnic
areas,
vacant
lots,
wood
decks,

bleachers,
cemeteries,
fuel
tanks,
runways,

helo
pads,
etc.;

Bleachers,
fence
lines,
fire
hydrants,
guard
rails,
parking
lots,
under
driveways,

sidewalks,
asphalt
520
125000
57000
70000
7800
44000
19000
23000
3600
Pre­
paving
650
157000
72000
88000
9800
56000
24000
29000
4600
Sodium
Chlorate
Appendices
­
110
Appendix
L.
Summary
of
Publically
Available
Data
in
EPA's
ECOTOX
Database
Sodium
Chlorate
Appendices
­
111
Fish
Common
Name
Endpoint
Test
Duration
Duration
Units
Ref
#
LC50
(
ug/
L)

Brown
trout
LC50
48
h
448
LC50:
7,300
Cherry
salmon,
yamame
trout
LC50*
96
h
6034
LC50:
1,100,000
Cherry
salmon,
yamame
trout
LC50*
48
h
6034
LC50:
3,300,000
Cherry
salmon,
yamame
trout
LC50*
24
h
6034
LC50:
4,000,000
Cherry
salmon,
yamame
trout
NR­
ZERO
4
d
8138
NR
Cherry
salmon,
yamame
trout
NR
2
d
8138
NR
Cherry
salmon,
yamame
trout
NR
1
d
8138
NR
Fathead
minnow
LC50
96
h
6051
LC50:
13,500,000
Fathead
minnow
LC50
96
h
6051
LC50:
13,600,000
Fathead
minnow
LC50
96
h
6051
LC50:
13,800,000
Goldfish
NR
4
d
916
Endpoint
Not
Reported:
1,000,000
Harlequinfish,
red
rasbora
LC50*
24
h
542
LC50:
8,600,000
Hasu
fish
LC50
96
h
12402
LC50:
2,340,000
Japanese
barbel
LC50*
10
d
6034
LC50:
2,000,000
Japanese
barbel
LC50*
96
h
6034
LC50:
3,300,000
Japanese
barbel
LC50*
48
h
6034
LC50:
3,800,000
Japanese
barbel
LC50*
48
h
6034
LC50:
3,800,000
Japanese
barbel
LC50*
96
h
6034
LC50:
3,800,000
Japanese
barbel
LC50*
24
h
6034
LC50:
4,000,000
Japanese
barbel
LC50*
24
h
6034
LC50:
4,200,000
Japanese
barbel
LC50*
12
h
6034
LC50:
4,700,000
Japanese
barbel
LC50*
6
h
6034
LC50:
4,900,000
Minnow
LC50
96
h
12402
LC50:
2,340,000
Rainbow
trout,
donaldson
trout
LC50
48
h
344
LC50:
<
1,100,000
Rainbow
trout,
donaldson
trout
NR
NR
wk
8139
Endpoint
Not
reported:
No
effects
at
60,000
Hasu
fish
LC50
96
h
12402
LC50:
2,340,000
Sodium
Chlorate
Appendices
­
112
Fungi
Scientific
Name
Endpoint
Test
Duration
Ref
#
Concentration
(
mM)

Penicillium
verrucosum
NOEC
48
hr
19279
>=
7.48
Trichoderma
hamatum
NOEC
48
hr
19279
>=
7.48
Aquatic
Invertebrates,
Laboratory
Studies
Scientific
Name
Common
Name
Test
Duration
Duration
Units
Ref
#
Concentration
(
ug/
L,
except
where
noted)

Asellus
hilgendorfi
Aquatic
sowbug
96
h
6034
LC50:
2,100,000
Asellus
hilgendorfi
Aquatic
sowbug
96
h
6034
LC50:
2,800,000
Asellus
hilgendorfi
Aquatic
sowbug
48
h
6034
LC50:
3,100,000
Asellus
hilgendorfi
Aquatic
sowbug
48
h
6034
LC50:
3,400,000
Asellus
hilgendorfi
Aquatic
sowbug
24
h
6034
LC50:
4,100,000
Haliplus
sp.
Beetle
10
d
6696
NOEC:
105,500
Stenopsyche
griseipennis
Caddisfly
96
h
6034
LC50:
2,700,000
Stenopsyche
griseipennis
Caddisfly
24
h
6034
LC50:
3,100,000
Stenopsyche
griseipennis
Caddisfly
48
h
6034
LC50:
3,100,000
Cloeon
dipterum
Mayfly
24
h
6954
LD50:
>
40,000
Cloeon
dipterum
Mayfly
3
h
6954
LD50:
>
40,000
Cloeon
dipterum
Mayfly
48
h
6954
LD50:
>
40,000
Cloeon
dipterum
Mayfly
6
h
6954
LD50:
>
40,000
Baetis
tricaudatus
Mayfly
10
d
6696
NOEC:
104,000
Tricorythodes
minutus
Mayfly
10
d
6696
NOEC:
109,000
Polycelis
nigra
Planarian
48
h
10013
LT50:
0.15
(
M)

Rutilus
rutilus
Roach
96
h
12402
LC50:
2,340,000
Petromyzon
marinus
Sea
lamprey
24
h
638
Endpoint
Not
Reported:
5,000
Isoperla
longiseta
Stonefly
10
d
6696
NOEC:
52,000
Isoperla
transmarina
Stonefly
10
d
6696
NOEC:
104,000
Daphnia
magna
Water
flea
48
h
6696
LC50:
3,162,000
Sodium
Chlorate
Appendices
­
113
Daphnia
magna
Water
flea
48
h
2130
Lethal
concentration:
4,240,000
Daphnia
magna
Water
flea
48
h
607
NOEC:
1,000,000
Dasycorixa
hybrida
10
d
6696
NOEC
107,000
Table
Notes.
Aquatic
Invertebrates,
Field
Studies
Scientific
Name
Common
Name
Effect
Trend
Test
Duration
Duration
Units
Ref
#
Exposure
Concentration
(
ug/
L)
Application
Rate
(
kg/
ha)
Application
Frequency
Application
Date
Not
Specified
POP
CHG
NR
wk
8139
<=
60,000
NR
NR
NR
Not
Specified
POP
DEC
7
h
8139
20,000
­
60,000
NR
NR
NR
Not
Specified
POP
CHG
NR
d
8138
0
­
57,000
200
1
X
10/
13/
69
Not
Specified
POP
CHG
NR
d
8138
0
­
57,000
200
1
X
10/
13/
69
Not
Specified
POP
CHG
4
d
8138
0
­
57,000
200
1
X
10/
13/
69
Ephemera
japonica
Mayfly
MOR
DEC
4
d
8138
800
­
57,000
200
1
X
10/
13/
69
Gammarus
sp.
Scud,
Amphipod
MOR
DEC
4
d
8138
800
­
57,000
200
1
X
10/
13/
69
Note:
Significance
of
Effects
were
not
indicated
Aquatic
Plants
Scientific
Name
Common
Name
Test
Duration
Ref
#
Concentration
Units
Nostoc
calcicola
Blue­
green
algae
14
days
19279
NOEC:
3.74
mM
Nostoc
calcicola
Blue­
green
algae
14
days
19279
NOEC:
3.74
mM
Ectocarpus
variabilis
Brown
algae
14
days
19279
NOEC:
<
0.005
mM
Ectocarpus
variabilis
Brown
algae
14
days
19279
LOEC:
0.005
mM
Ectocarpus
variabilis
Brown
algae
14
days
19279
EC50:
0.012
mM
Ectocarpus
variabilis
Brown
algae
14
days
19279
LOEC:
0.04
mM
Ectocarpus
variabilis
Brown
algae
14
days
19279
NOEC:
0.04
mM
Ectocarpus
variabilis
Brown
algae
14
days
19279
EC50:
0.14
mM
Phaeodactylum
Diatom
72
hours
19369
NOEC:
50
mg/
L
Scientific
Name
Common
Name
Test
Duration
Ref
#
Concentration
Units
Sodium
Chlorate
Appendices
­
114
tricornutum
Phaeodactylum
tricornutum
Diatom
72
hours
19369
LOEC:
100
mg/
L
Phaeodactylum
tricornutum
Diatom
72
hours
19369
NOEC:
100
mg/
L
Phaeodactylum
tricornutum
Diatom
72
hours
19369
LOEC:
200
mg/
L
Phaeodactylum
tricornutum
Diatom
72
hours
19369
EC50:
298
mg/
L
Phaeodactylum
tricornutum
Diatom
72
hours
19369
EC50:
444
mg/
L
Lemna
perpusilla
Duckweed
7
days
15281
Endpoint
Not
Reported:
1000000
ug/
L
Selenastrum
capricornutum
Green
algae
96
hours
19279
NOEC:
0.75
mM
Selenastrum
capricornutum
Green
algae
96
hours
19279
NOEC:
>=
0.93
mM
Selenastrum
capricornutum
Green
algae
96
hours
19279
LOEC:
0.93
mM
Selenastrum
capricornutum
Green
algae
5
days
344
EC50:
133
ppm
Scenedesmus
quadricauda
Green
algae
96
hours
17729
NOEC:
>=
784
ug/
L
Scenedesmus
subspicatus
Green
algae
NR
19370
NOEC:
1569
mg/
L
Scenedesmus
subspicatus
Green
algae
NR
19370
NOEC:
1569
mg/
L
Scenedesmus
quadricauda
Green
algae
4
days
607
Endpoint
Not
reported:
3000
ug/
L
Scenedesmus
subspicatus
Green
algae
72
hours
19370
LOEC:
>
3137
mg/
L
Scenedesmus
subspicatus
Green
algae
72
hours
19370
LOEC:
>
3137
mg/
L
Scenedesmus
subspicatus
Green
algae
NR
19370
LOEC:
3137
mg/
L
Scenedesmus
subspicatus
Green
algae
NR
19370
LOEC:
3137
mg/
L
Scenedesmus
subspicatus
Green
algae
72
hours
19370
NOEC:
3137
mg/
L
Scenedesmus
subspicatus
Green
algae
72
hours
19370
NOEC:
3137
mg/
L
Sodium
Chlorate
Appendices
­
115
Appendix
M.
Summary
of
Key
Toxicity
Studies
for
This
Assessment
Sodium
Chlorate
Appendices
­
116
Fish
MRID
418872­
03
Rainbow
trout
(
20/
concentration)
were
exposed
to
sodium
chlorate
at
150,
240,
380,
600,
and
1000
mg/
L
for
96
hours
under
flow­
through
conditions.
Dissolved
oxygen
was
9.0
to
9.8
mg/
L,
pH
was
6.8
to
7.3,
and
the
temperature
was
11.0
to
11.6
°
C.
The
NOAEC
was
600
mg/
L
(
1/
20
fish
died
at
1000
mg/
L).
There
was
evidence
that
the
chlorate
concentrations
were
lower
at
the
end
of
the
study
as
indicated
by
a
decline
in
conductivity
between
days
3
and
4
of
the
study.
Conductivity
is
directly
related
to
chlorate
concentration.
Therefore,
this
study
is
classified
as
supplemental.

MRID
418872­
02
Bluegill
(
20/
concentration)
were
exposed
to
sodium
chlorate
at
140,
240,
380,
600,
and
1000
mg/
L
for
96
hours
under
flow­
through
conditions.
Dissolved
oxygen
was
8.3
to
9.4
mg/
L,
pH
was
8.0
to
8.7,
and
the
temperature
was
21.1
to
22.9
°
C.
The
NOAEC
was
1000
mg/
L.
Chlorate
concentrations
were
not
analytically
confirmed.
Also,
variability
in
some
of
the
water
quality
parameters
were
observed.
This
variability,
however,
did
not
likely
affect
the
results
of
this
study,
and
submission
of
a
new
study
in
bluegill
would
not
likely
affect
the
conclusions
of
this
risk
assessment.
As
discussed
in
Section
3
of
this
assessment,
this
study
was
previously
considered
invalid
by
the
Agency.
Submission
of
a
confirmatory
study
in
daphnids
was
submitted,
which
allows
this
fish
study
to
be
upgraded
from
invalid
to
supplemental.
Therefore,
this
study
is
classified
as
supplemental.

MRID
418872­
07
Sheepshead
Minnows
(
20/
concentration)
were
exposed
to
sodium
chlorate
at
140,
240,
380,
600,
and
1000
mg/
L
for
96
hours
under
flow­
through
conditions.
The
NOAEC
was
1000
mg/
L.
Chlorate
concentrations
were
not
analytically
confirmed.
As
discussed
in
this
assessment,
this
study
was
previously
considered
invalid
by
the
Agency.
Submission
of
a
confirmatory
study
in
daphnids
was
submitted,
which
allows
this
fish
study
to
be
upgraded
from
invalid
to
supplemental.
Therefore,
this
study
is
classified
as
supplemental.

Aquatic
Invertebrates
MRID
418872­
04
Daphnids
(
20/
concentration)
were
exposed
to
sodium
chlorate
at
150,
240,
380,
600,
and
1000
mg/
L
for
48
hours
under
flow­
through
conditions.
Temperature
was
19.5­
20.9
B
C.
Dissolved
oxygen
was
8.5­
9.0
mg/
L,
and
pH
was
7.3­
7.7.
The
NOAEC
was
1000
mg/
L.
Chlorate
concentrations
were
not
analytically
confirmed.
As
discussed
in
this
assessment,
this
study
was
previously
considered
invalid
by
the
Agency.
Submission
of
a
confirmatory
study
in
daphnids
was
submitted,
which
allows
this
fish
study
to
be
upgraded
from
invalid
to
supplemental.
Therefore,
this
study
is
classified
as
supplemental.

MRID
438748­
01
The
48­
hour
acute
toxicity
of
sodium
chlorate
to
the
water
flea
was
studied
under
static
conditions.
Daphnids
(
20/
concentration)
were
exposed
to
the
test
material
at
mean
measured
concentrations
of
0,
52,
103,
208,
405,
and
1019
mg/
L.
The
EC50
was
920
mg/
L,
and
the
NOAEC
was
405
mg/
L
based
on
55%
mortality
at
1019
mg/
L.
This
study
is
classified
as
supplemental
because
the
pH
and
water
hardness
were
outside
the
range
recommended
by
EPA
guidelines.
pH
could
affect
the
toxicity
of
chlorate
because
a
reduction
product
(
chlorite)
is
particularly
toxic
to
daphnids.

MRID
418872­
06
The
96­
hour
acute
toxicity
of
sodium
chlorate
to
mysid
shrimp
was
studied
under
flow­
through
conditions.
Mysid
shrimp
(
20/
concentration)
were
exposed
to
sodium
chlorate
at
nominal
concentrations
of
0,
130,
220,
360,
590,
and
1000
mg/
L.
Dissolved
oxygen
was
7.4
to
8.9
mg/
L,
pH
was
7.6
to
7.8,
and
the
temperature
was
21.4
to
23.0*
C.
2/
20
mysids
died
at
1000
mg/
L,
and
1/
20
died
at
590
mg/
L.
No
other
mortalities
or
signs
of
toxicity
were
Sodium
Chlorate
Appendices
­
117
noted.
This
study
is
classified
as
supplemental
because
the
test
substance
concentratins
were
not
analytcally
confirmed.
This
study
was
previously
assigned
a
classification
of
invalid;
however,
as
discussed
in
this
assessment,
submission
of
a
confirmatory
study
in
daphnids
was
submitted,
which
allows
this
fish
study
to
be
upgraded
from
invalid
to
supplemental.

MRID
418872­
05
Eastern
oysters
(
20/
concentration)
were
exposed
to
sodium
chlorate
at
nominal
concentrations
of
0,
70,
120,
250,
500,
and
1000
mg/
L
for
96
hours
under
flow­
through
conditions.
Temperature
was
20­
23*
C,
dissolved
oxygen
was
7.2­
7.5,
pH
was
7.7­
8.0,
and
salinity
was
21­
24
ppt
(
parts
per
thousand).
EC50
was
>
1000
mg/
L.
No
treatment
related
mortalities
occurred.
Shell
growth
at
250,
500,
and
1000
mg/
L
was
10%,
15%,
and
30%
lower
than
controls,
respectively.
Shell
growth
at
all
other
concentrations
were
equivalent
to
or
greater
than
controls.
Chlorate
concentrations
were
not
analytically
confirmed.
As
discussed
in
this
assessment,
submission
of
a
confirmatory
study
in
daphnids
was
submitted,
which
allows
this
fish
study
to
be
upgraded
from
invalid
to
supplemental.
Therefore,
this
study
is
classified
as
supplemental.

Aquatic
Plants
MRID
418872­
01
Green
algae
were
exposed
to
sodium
chlorate
at
nominal
concentrations
of
0,
62.5,
125,
250,
500,
and
1000
mg/
L
(
nominal)
for
96
hours
under
flow­
through
conditions.
Temperature
was
23.5­
25.5
B
C
and
pH
was
7.2­
7.6.
The
EC50
was
133
mg/
L
and
the
NOAEC
was
62.5
mg/
L.
This
study
is
classified
as
Core.

Van
Wijk,
Kroon,
and
Irmgard.
1998.
Toxicity
of
chlorate
and
chlorite
to
selected
species
of
algae,
bacteria,
and
fungi.
Ecotoxicology
and
Environmental
Safety.
40:
206­
211.
Green
algae,
brown
algae,
and
blue­
green
algae
were
exposed
to
unreported
chlorate
concentrations
for
14
days
(
brown
and
blue­
green
algae)
or
96
hours
(
green
algae).
Initial
cell
density
was
not
reported.
Temperature
was
22
to
24
B
C
and
pH
was
maintained
at
7.8
to
9.
EC50
values
were
estimated
by
linear
regression.
Organisms
were
grown
using
either
ammonium
or
nitrate
as
the
sole
nitrogen
source.
The
EC50
for
brown
algae
was
0.012
mM
to
0.14
mM
depending
on
the
nitrogen
source.
A
NOEC
was
not
observed
(
effects
were
observed
at
the
lowest
concentrations
tested,
0.04
to
0.005
mM).
EC50s
were
not
estimated
for
green
algae
or
blue­
green
algae.
The
NOEC
and
LOEC
for
green
algae
was
0.75
mM
and
0.93
mM,
respectively.
No
effects
were
observed
in
bluegreen
algae
at
concentrations
up
to
3.74
mM.

Terrestrial
Plants
MRID
463008­
01
Vegetative
vigor
was
studied
on
10
plant
species
after
application
of
Sodium
chlorate
at
348
lb
a.
i./
A.
Test
species
included
buckwheat,
corn,
cucumber,
mustard,
oats,
onion,
radish,
sorghum,
soybean,
and
tomato.
The
348
lb
a.
i./
A
treatment
group
percent
inhibitions
exceeded
25%
for
the
mean
fresh
weights
of
all
test
species.
For
all
test
species,
almost
all
plants
were
dead
by
11
days
and
the
phytotoxic
effects
included
chlorosis,
necrosis
and
stunting
in
the
348
lb
a.
i./
A
treatment
group.
Cucumber
exhibited
the
greatest
reduction
for
a
dicot,
with
95.4%
mean
fresh
weight
inhibition
and
sorghum
exhibited
the
greatest
reduction
for
a
monocot,
with
83.1%
mean
fresh
weight
inhibition.
The
EC25
and
NOEC
were
<
348
lb
a.
i./
A
for
all
test
species.
A
Tier
II
study
is
recommended.
This
study
is
classified
as
Core
for
a
Tier
I
vegetative
vigor
study.

MRID
463008­
02
Seed
germination
and
seedling
emergence
were
studied
on
10
plant
species
after
application
of
sodium
chlorate
at
348
lb
a.
i./
A.
Test
species
included
buckwheat,
corn,
cucumber,
mustard,
oats,
onion,
radish,
sorghum,
soybean,
Sodium
Chlorate
Appendices
­
118
and
tomato.
By
5
days
in
the
petri
dish
bioassay,
the
348
lb
a.
i./
A
treatment
groups
had
failed
to
germinate
for
all
test
species
compared
to
the
controls.
By
14
days,
the
percent
inhibitions
for
emergence
were
10,
3,
97,
81,
5,
0,
27,
21,
8,
and
82%
for
buckwheat,
corn,
cucumber,
mustard,
oats,
onion,
radish,
sorghum,
soybean,
and
tomato,
respectively,
compared
to
the
control.
The
348
lb
a.
i./
A
treatment
group
percent
inhibitions
exceeded
25%
for
the
mean
fresh
weights
of
all
test
species.
For
all
test
species,
the
phytotoxic
effects
included
chlorosis,
necrosis,
stunting,
and
distortion
in
the
348
lb
a.
i./
A
treatment
group.
Cucumber
exhibited
the
greatest
reduction
for
a
dicot,
with
98%
mean
fresh
weight
inhibition
and
corn
exhibited
the
greatest
reduction
for
a
monocot,
with
90%
mean
fresh
weight
inhibition.
The
EC25
and
NOEC
for
this
study
was
<
348
lb
a.
i./
A
for
all
test
species.
A
Tier
II
study
is
recommended.
This
study
is
classified
as
Core
for
a
Tier
I
seedling
emergence
study.

Sodium
Chlorite
Two
toxicity
studies
using
sodium
chlorite
on
non­
target
plants
were
submitted.
These
studies
were
not
considered
in
this
assessment
on
sodium
chlorate
because
non­
target
plant
exposure
to
chlorite
from
use
of
sodium
chlorate
is
uncertain,
and
the
relative
toxicity
of
chlorite
to
chlorate
is
uncertain.
Also,
the
maximum
concentration
used
in
these
studies
was
equivalent
to
7.0
lbs
ai./
Acre.
Chlorate
is
used
at
up
to
12.5
lbs
a.
i./
Acre.
Nonetheless,
a
summary
of
these
studies
are
presented
below.

MRID
419485­
01
Seed
germination
(%
germination
and
radicle
length)
and
seedling
emergence
(%
emergence
and
fresh
weight)
were
studied
on
10
plant
species
after
application
of
Sodium
Chlorite
at
3.5
ppm
(
7.0
lb
a.
i./
A).
Test
species
included
buckwheat,
corn,
cucumber,
mustard,
oats,
onion,
radish,
sorghum,
soybean,
and
tomato.
Buckwheat
was
the
only
species
which
exhibited
>
25%
inhibition,
based
on
reductions
in
radicle
length.
In
addition
to
this
negative
effect,
oat
and
onion
radicle
length
were
also
significantly
reduced
in
the
treatment
group
(
however,
reductions
did
not
exceed
25%
for
these
species).
No
other
species
was
significantly
affected
by
treatment
for
radicle
length,
%
emergence,
or
fresh
weight
endpoints.
The
EC25
and
NOEC
for
buckwheat
radicle
length
were
<
7
lb
a.
i./
A.
Based
on
the
sensitivity
of
buckwheat
radicle
length
(
i.
e.,
>
25%
reduction),
a
Tier
II
study
with
this
species
is
suggested.

This
study
is
classified
as
Supplemental.
However,
this
study
cannot
fulfill
the
guideline
requirements
for
a
vegetative
vigor
study
for
sodium
chlorate
(
Subdivision
J,
§
122­
1
(
TIER
I))
because
the
test
substance
was
not
sodium
chlorate.
Also,
missing
information
needs
to
be
provided
to
ensure
that
the
study
is
scientifically
sound.
Additional
water
was
applied
to
the
soil
surface
immediately
after
application
in
the
emergence
test
(
reportedly
to
ensure
contact
of
the
test
chemical
with
the
seed).
Chlorite
is
expected
to
be
very
soluble
in
water
and
very
mobile
in
soil.
Therefore,
this
watering
may
have
resulted
in
decreased
exposure
to
chlorite.

MRID
419485­
02
Vegetative
vigor
(
fresh
weight)
was
studied
on
10
plant
species
after
application
of
Sodium
Chlorite
at
3.5
ppm
(
7.0
lb
a.
i./
A).
Test
species
included
buckwheat,
corn,
cucumber,
mustard,
oats,
onion,
radish,
sorghum,
soybean,
and
tomato.
The
7.0
lb
a.
i./
A
treatment
group
percent
inhibitions
were
<
25%
for
the
mean
fresh
weights
of
all
test
species.
No
mortalities
occurred
throughout
the
duration
of
the
test.
Chlorosis
was
observed
in
three
replicates
of
oats,
new
leaf­
distortion
was
observed
in
all
tomatoes.
These
observations
were
observed
in
treated
and
control
plants.
These
symptoms
were
manifested
throughout
the
course
of
the
test
for
oats
and
tomatoes.
Corn
experienced
symptoms
of
nitrogen
deficiency
during
the
first
week
of
testing,
but
these
symptoms
were
not
present
at
the
conclusion
of
the
test.
The
EC25
and
NOEC
were
>
7.0
lb
a.
i./
A
for
all
test
species.

This
study
is
classified
as
Supplemental.
This
study
cannot
fulfill
the
guideline
requirements
for
a
vegetative
vigor
study
for
sodium
chlorate
(
Subdivision
J,
§
122­
1
(
TIER
I))
because
the
test
substance
was
not
sodium
chlorate.
Also,
this
study
did
not
evaluate
some
toxicological
parameters
including
dry
weight
and
plant
height.
In
addition,
overhead
watering
used
in
this
study
on
two
occasions
could
have
facilitated
chlorite's
dissipation
and
reduced
exposure
time.
Sodium
Chlorate
Appendices
­
119
Birds
MRID
421494­
01
Mallard
ducks
(
10/
dose)
were
administered
a
single
acute
oral
dose
via
gavage
at
398,
631,
1000,
1590,
or
2510
mg/
kg­
bw.
No
mortality
or
signs
of
toxicity
were
observed
at
any
dose.
This
study
is
classified
as
acceptable.

MRID
418199­
07
Bobwhite
quail
(
10/
dose)
were
maintained
on
a
diet
supplemented
with
sodium
chlorate
at
measured
concentrations
of
562,
1000,
1780,
3160,
or
5620
ppm
for
5
days.
No
mortality
or
signs
of
toxicity
were
observed
at
any
concentration.
This
study
is
classified
as
acceptable.

MRID
418199­
08
Mallard
ducks
(
10/
dose)
were
maintained
on
a
diet
supplemented
with
sodium
chlorate
at
measured
concentrations
of
562,
1000,
1780,
3160,
or
5620
ppm
for
5
days.
No
mortality
or
signs
of
toxicity
were
observed
at
any
concentration.
This
study
is
classified
as
acceptable.

Mammals
Acute
exposures
In
an
acute
oral
toxicity
study
(
MRID
41819901),
groups
of
fasted,
young
adult
Sprague
Dawley
albino
rats
(
5/
sex)
were
given
a
single
oral
dose
of
sodium
chlorate
crystal
(
100
%
a.
i.,
batch/
lot
DL­
1)
in
50%
w/
w
solution
of
distilled
water
at
doses
of
2
or
5
g/
kg
bw
and
observed
for
14
days.
These
doses
were
based
on
a
range
finding
study
of
1
rat/
sex
dosed
at
0.3,
0.6,
1.25,
2.5,
or
5.0
g/
kg
bw,
where
there
no
mortalities
observed.
Oral
LD50
is
equal
or
greater
than
5000
mg/
kg
bw
(
both
sexes).
Sodium
chlorate
is
of
SLIGHT
oral
Toxicity
based
on
the
oral
LD50
in
males
and
females
(
Toxicity
Category
IV).
All
animals
in
the
2
g/
kg
group
survived
with
only
transient
hunched
posture
in
one
male
2­
4
hours
post­
dosing.
In
the
5g/
kg
dose,
one
female
died
one
day
after
dosing.
Several
other
animals
appeared
lethargic
and
had
hunched
posture
shortly
after
exposure
that
lasted
for
the
first
24
hours.
Necropsy
findings
of
the
dead
female
showed
green
discoloration
of
the
intestine,
a
light
green
fluid
on
the
stomach,
pink
liquid
in
the
abdominal
cavity
and
dark
red
lung
discoloration.
Necropsy
findings
of
the
survivors
were
unremarkable.
This
acute
oral
toxicity
study
is
classified
acceptable/
guideline.
This
study
satisfies
does
satisfy
the
guideline
requirement
for
an
acute
oral
toxicity
study
on
the
technical
material
(
OPPTS
870.1100;
OECD
401)
in
the
rat.
Other
acute
studies
are
summarized
in
Table
M­
1
below.
Sodium
Chlorate
Appendices
­
120
Table
M­
1.
Acute
Toxicity
Profile
in
Mammals
Guideline
No./
Study
Type
Study
Type
­
Species
MRID
No.
Results
870.1100
Acute
oral
­
Rats
41819901
5000
mg/
kg
(
rat)

870.1200
Acute
dermal
­
Rabbits
41819902
42497601
LD50
=
>
2000
mg/
kg
(
dry
crystal)
LD50
=
>
2000
mg/
kg
(
moistened)

870.2400
Acute
eye
irritation
­
Rabbit
00085090;
00102998
41819904
mildly
irritating
mildly
irritating
870.2500
Acute
dermal
irritation
­
Rabbit
41819905
42497602
non­
irritating
(
dry
crystal)
minimally
irritating
(
moistened)
Sodium
Chlorate
Appendices
­
121
Table
M­
2.
Summary
of
Selected
Repeated­
Dose
Toxicity
Studies
Using
Sodium
Chlorate
in
Laboratory
Animalsa
Guideline
No./
Study
Type
MRID
No.
(
year)/
Classification
/
Doses
Results
870.3100
90­
Day
oral
toxicity
(
Sprague­
Dawley
Rats)

Non­
Guideline
90­
Day
oral
toxicity
(
Sprague­
Dawley
Rats)

Non­
Guideline
90­
Day
oral
toxicity
(
F344
rats
and
B6C3F1
mice)
40444801(
1997)
Acceptable/
guideline
0,
10,
40,
100
or
1000
mg/
kg/
day,
oral
gavage
McCauley
et
al,
1995
SD
rats
(
10/
sex/
group)
NaClO3
in
the
drinking
water
3.0,
12.0,
or
48
mM
for
90
days
M:
30,
100
and
512
mg/
kg/
day
F:
42,
158,
and
800
mg/
kg/
day
Hooth
et
al,
2001
NaClO3
in
drinking
water
at
0,
0.125,
0.25,
1.0
or
2
g/
L
for
21
days
or
90
days
in
rats
and
mice
M:
14,
28,
112,
225
mg/
kg/
day
F:
20,
40,
160
mg/
kg/
day
at
0,
0.5,
1.0,
2.0,
4.0,
or
6
g/
L
NOAEL
=
100
mg/
kg/
day
LOAEL
=
1000
mg/
kg/
day
based
on
hematological
effects
(
hemoglobin
concentration,
hematocrit,
RBC
counts
were
statistically
significantly
decreased,
and
reticulocyte
count
was
statistically
significantly
increased
in
females.
In
males,
only
the
hematocrit
was
statistically
significantly
decreased.
The
adrenal
weight
was
depressed
in
both
males
and
females.

NOAEL
=
30
and
42
mg/
kg/
day
in
males
and
females.
LOAEL
=
100
mg/
kg/
day
in
males
and
150
mg/
kg/
day
in
females,
based
on
the
pituitary
effects
(
vacuolization)
and
thyroid
gland
effects
(
colloid
depletion),
the
body
weight
decrease
and
organ
weight
changes
and
reduction
in
erythrocyte
counts
and
hemoglobin
content.

NOAEL
=
0.25
g/
L
(
28
&
40
mg/
kg/
day
for
males
and
females,
respectively)
LOAEL
=
1.0
g/
L
based
on
colloid
depletion
and
follicular
cell
hyperplasia,
(
112
&
160
mg/
kg/
day
for
males
and
females,
respectively)
Total
serum
triiodothyronine
(
T3)
and
thyroxine
(
T4)
concentrations
were
decreased
significantly
and
TSH
levels
increased
significantly
in
male
and
female
rats
after
4
days
of
treatment
with
1.0
or
2.0
g/
L
and
after
21
days
of
treatment
with
2.0
g/
L.
TSH
levels
also
increased
significantly
in
male
rats
after
21
days
of
treatment
with
1.0
g/
L.
Serum
T3
and
T4
levels
were
comparable
to
controls
in
male
and
female
rats
after
90
days
of
treatment,
but
TSH
levels
were
increased
in
both
sexes.
Follicular
cell
hyperplasia
was
not
present
in
male
or
female
mice.
Table
M­
2.
Summary
of
Selected
Repeated­
Dose
Toxicity
Studies
Using
Sodium
Chlorate
in
Laboratory
Animalsa
Guideline
No./
Study
Type
MRID
No.
(
year)/
Classification
/
Doses
Results
Sodium
Chlorate
Appendices
­
122
870.3150
90­
Day
oral
toxicity
(
Beagle
Dogs)
MRID
40460402
(
1987)
Acceptable/
Guideline
oral
gavage
0,
30,
60
or
360
mg/
kg/
day
for
90
d
NOAEL
=
360
mg/
kg/
day
(
HDT)
LOAEL
=
greater
than
360
mg/
kg/
day
based
on
lack
of
detectable
adverse
effects.
Higher
dose
levels
were
not
possible
due
to
occurrence
of
emesis
at
higher
doses.
Non­
Guideline
subacute
study
in
dogsHeywood
et
al,
1972
doses
of
200
to
326
mg/
kg/
day
of
sodium
chlorate
administered
daily
by
intubation
as
50
ml
of
6%
solution
to
8
dogs
for
5
days
sodium
chlorate
caused
reduction
of
packed
cell
volume,
hemoglobin
and
red
blood
cells.
A
consistent
increase
in
plasma
urea
concentration
was
also
observed.
Two
animals
that
received
308
or
326
mg/
kg/
day
suffered
appetite
loss,
body
weight
decline
and
appearance
of
blood
in
their
urine
or
feces.
One
of
the
animals
died
after
4
days
of
exposure.
Postmortem
examination
of
both
animals
revealed
typical
signs
of
chlorate
poisoning,
including
cyanotic
kidney
surface
and
evidence
of
necrosis
and
hemolysis
in
the
kidney.
Five
of
the
8
animals
displayed
tissue
pathology
indicative
of
hemolysis
such
as
Kupffer
cells
containing
brown
pigment.

Non­
Guideline
21
day
oral
toxicity
study
(
B6C3F1
mice)
NTP
Study
(
1999a)
10/
sex/
dose:
0,
125,
500,
1000
or
2000
mg/
L
M:
22,
43,
173
or
348
mg/
kg/
day
0,
20,
44,
F:
94,
192
or
363
mg/
kg/
day
Sodium
chlorate
had
no
effect
on
survival,
body
weights,
clinical
signs,
water
consumption,
hematology
parameters,
methemoglobin
concentration,
or
organ
weights
of
either
sex.
There
were
no
gross
or
microscopic
lesions
that
were
considered
to
be
due
to
sodium
chlorate
treatment.

Non­
Guideline
21
day
oral
toxicity
study
(
Fisher
344
rats)
NTP
Study
(
1999b)
10/
sex/
dose:
0,
125,
500,
1000
or
2000
mg/
L
M:
0,
20,
36,
77
or
170
mg/
kg/
day
F:
0,
21,
38,
73,
152
or
338
mg/
kg/
day
Sodium
chlorate
had
no
effect
on
survival,
body
weights,
clinical
signs
or
water
consumption.
A
moderate
to
severe
neutropenia
was
observed
in
both
sexes
on
day
4
and
22.
Very
mild
decreases
in
erythrocyte
counts,
hemoglobin,
and
hematocrit
were
considered
not
to
be
biologically
significant.
The
only
gross
or
microscopic
lesion
that
was
considered
to
be
treatment
related
was
a
minimal
to
mild
follicular
cell
hyperplasia
of
the
thyroid
gland
seen
in
males
at
500
mg/
L
or
greater
and
in
females
at
250
mg/
L
or
greater.

870.3700a
Prenatal
developmental
(
rats)
MRID
40460401(
1987)
Acceptable/
Guideline
oral
gavage
0,
10,
100
or
1000
mg/
kg/
d
on
GD
6­
15
Maternal
NOAEL
=
1000
mg/
kg/
day
(
HDT)
LOAEL
=
>
1000
mg/
kg/
day.
Developmental
NOAEL
=
1000
mg/
kg/
day
(
HDT)
LOAEL
=
>
1000
mg/
kg/
day
based
on
lack
of
effects
Table
M­
2.
Summary
of
Selected
Repeated­
Dose
Toxicity
Studies
Using
Sodium
Chlorate
in
Laboratory
Animalsa
Guideline
No./
Study
Type
MRID
No.
(
year)/
Classification
/
Doses
Results
Sodium
Chlorate
Appendices
­
123
870.3700b
Prenatal
developmental
(
Rabbits)
NTP
(
2002)
Acceptable/
Guideline
0,
100,
250,
or
475
mg/
kg/
d
on
GD
6­
29.
Range
finding
study:
0,
100,
250,
500,
750
or
1000
mg/
kg/
d
Maternal
NOAEL
=
475
mg/
kg/
day
(
HDT)
LOAEL
=
500
mg/
kg/
day
based
on
mortality
in
range
finding
study.
Developmental
NOAEL
=
475
mg/
kg/
day
(
HDT)
LOAEL
=
>
475
mg/
kg/
day
a
Data
compiled
by
the
Health
Effects
Division
of
EPA.
