UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
Chemical:
Sodium
Chlorate
PC
Code:
073301
DP
Barcode:
D303884
MEMORANDUM
DATE:
June
1,
2006
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:
Felicia
Fort
Special
Review
and
Reregistration
Division
(
SRRD)
(
7505C)
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES,
AND
TOXIC
SUBSTANCES
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
end­
use
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
possible
chlorate
reduction
product,
chlorite,
is
considerably
more
toxic
than
chlorate
to
aquatic
invertebrates.
However,
chlorite
is
a
transient
reduction
product,
and
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.

°
Aquatic
Plants:
Data
in
Selenastrum
capricornutum
(
a
freshwater
green
alga)
and
Lemna
minor
were
submitted.
Rqs
for
endangered
vascular
plants
were
exceeded
for
the
non­
agricultural
use
sites.
However,
the
EECs
for
the
non­
agricultural
use
sites
are
likely
conservative;
therefore,
additional
information
on
use
pattern
would
allow
for
characterization
of
potential
risks
to
aquatic
plants.
Also,
testing
on
three
additional
required
plant
species
is
required
for
herbicides.
Overall,
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
°
Birds,
potential
reproduction
risks.
LOCs
were
exceeded
for
both
agricultural
and
non­
agricultural
uses.
The
highest
RQ
was
11
for
agricultural
uses;
RQs
for
nonagricultural
sites
were
considerably
higher.
All
assessed
application
rates
resulted
in
LOC
exceedance
for
multiple
food
items.

°
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.

°
Mammals,
potential
reproduction
risks.
Risk
quotients
exceeded
the
LOC
of
1.0
for
all
uses
for
at
least
one
mammalian
weight
class.
However,
interpretation
of
the
reproduction
risk
quotients
is
difficult
becuase
the
assessment
was
based
on
a
free
standing
NOAEC
(
no
reproductive
effects
were
observed
at
any
dose
tested).
The
highest
RQ
for
agricultural
uses
was
2.6.
Risk
quotients
for
the
non­
agricultural
use
sites
would
be
considerably
higher
for
mammals
in
treated
areas.

°
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
as
an
herbicide.
4
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.
Even
though
the
persistence
of
chlorate
in
the
field
is
uncertain,
a
terrestrial
field
dissipation
data
from
a
study
conducted
as
per
164­
1
guideline
may
not
provide
adequate
data
because
of
the
complexity
of
the
chlorine
oxyanion
system
and
analytical
chemistry
methodology.

While
a
164­
1
guideline
study
may
not
be
appropriate
for
sodium
chlorate,
the
Agency
is
still
concerned
about
the
prolonged
use
of
sodium
chlorate
on
cotton
(
about
50
years).
Given
that
chloride
is
the
end
chemical
species
of
chlorate,
it
poses
the
question
of
increased
chloride
from
year­
after­
year
usage
(
i.
e.,
"
salinization")
and
leaching
of
chloride
to
ground
water.,
particularly
in
areas
where
chloride
is
not
a
significant,
natural
component
in
soil
and/
or
ground
water.

Therefore,
the
EFED
recommends
a
retrospective
monitoring
study
(
soil;
ground
water)
aimed
to
address
the
effect
of
prolong
use
of
sodium
chlorate
on
cotton.
The
study
must
be
conducted
upon
agreement
of
a
protocol,
but
monitoring
sites
in
coastal
areas
should
not
be
included.

Reproduction
toxicity
study
in
mallard
ducks
(
71­
4).
The
submitted
study
in
bobwhite
quail
produced
clear
signs
of
reproductive
impairment
at
a
dietary
concentration
of
964
ppm.
The
NOAEC
in
bobwhite
quail
was
271
ppm,
which
resulted
in
LOC
exceedances.

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:
Skeletonema
costatum
(
a
marine
diatom),
Anabaena
flos­
aquae
(
a
blue­
green
bacterium),
and
a
freshwater
diatom.
5
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
(
spot
treatments),
which
would
reduce
the
likelihood
that
an
animal
would
consume
100%
of
its
diet
from
chlorate
treated
areas.
This
uncertainty
likely
resulted
in
an
overestimation
of
risk.
Clarification
of
label
instructions
would
reduce
this
uncertainty.

°
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.
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.
1
Therefore,
chlorate
body
burdens
could
be
substantially
higher
in
some
animals
resulting
in
increased
risk.

Toxicity
°
Open
literature
toxicity
data
were
located
that
suggest
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.

1
Klingman,
1977
as
cited
by
the
Agricultural
Marketing
Service
of
USDA
(
2000);
on­
line
at
http://
www.
ams.
usda.
gov/
nop/
NationalList/
TAPReviews/
SodiumChlorate.
pdf.
6
°
No
chronic
studies
in
fish
(
72­
4)
have
been
submitted
to
the
Agency;
therefore,
this
endpoint
cannot
be
evaluated
at
this
time.

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,
particularly
for
the
nonagricultural
uses
contain
all
of
the
language
necessary
to
protect
water
resources.
Many
of
the
listed
uses
in
this
pattern
appear
to
contradict
the
limitations
specified
in
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.
7
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
8
TABLE
OF
CONTENTS
1.
Environmental
Risk
Conclusions...........................................................................................
10
2.
Problem
Formulation
............................................................................................................
13
2.1.
Initial
Considerations....................................................................................................................
13
2.2.
Stressor
Identification,
Source,
and
Distribution....................................................................
15
2.3.
Exposure
Assessment
Approach...............................................................................................
23
2.4.
Conceptual
Model
.........................................................................................................................
25
2.5.
Effects
Assessment
Approach
....................................................................................................
27
2.6.
Risk
Characterization
Approach
................................................................................................
29
2.7.
Key
Uncertainties
and
Information
Gaps
in
This
Assessment
...........................................
29
3.
Analysis
...............................................................................................................................
31
3.1.
Environmental
Fate.......................................................................................................................
31
3.2.
Exposure..........................................................................................................................................
38
3.3.
Ecological
Effects
Characterization
..........................................................................................
45
4.
Risk
Characterization...........................................................................................................
52
4.1
Aquatic
Organisms........................................................................................................................
52
4.2
Risks
to
Birds,
Acute
and
Chronic
Exposures.........................................................................
56
4.3
Risk
to
Mammals,
Acute
Exposures
.........................................................................................
58
4.4.
Potential
Reproduction
Risk
to
Mammals................................................................................
64
4.5.
Endocrine
Disruption
Potential
..................................................................................................
65
4.6.
Potential
Risk
to
Terrestrial
Plants
............................................................................................
65
4.7.
Uncertainties
in
the
Terrestrial
Organism
Risk
Assessment
................................................
66
4.8.
Potential
Risk
to
Threatened
and/
or
Endangered
Species.....................................................
67
5.
References
........................................................................................................................
71
9
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
10
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.
11
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
Acute
The
submitted
data
suggest
that
risk
is
presumably
lower
than
the
Agency's
level
of
concern
for
acute
effects.

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

Potential
Risk
to
Aquatic
Invertebratesa
Acute
and
chronic
The
Agency's
levels
of
concern
were
not
exceeded.

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.

Potential
risk
to
mammals
Chronic
LOCs
were
exceeded
for
all
weight
classes
for
at
least
one
food
item.
The
highest
RQ
was
2.6.
Rqs
were
based
on
a
free­
standing
NOAEC
(
no
effects
were
observed
in
the
study
at
any
concentration).

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

Potential
risk
to
birds
Chronic
LOCs
were
exceeded
for
all
assessed
application
rates.
The
highest
RQ
for
agricultural
uses
was
11.
Estimated
concentrations
were
generally
higher
than
the
LOAEC
from
the
submitted
bobwhite
quail
study
of
964
ppm
(
MRID
46729701).
At
this
dietary
concentration,
>
60%
reductions
in
egg
production
and
hatching
occurred.

Terrestrial
Plants
Acute
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
application
rates.

Potential
risk
to
aquatic
plants
Acute
and
chronic
LOCs
for
algae
and
duckweed
were
not
exceeded
for
agricultural
uses.
However,
aquatic
plant
toxicity
data
in
several
required
species
have
not
been
submitted;
therefore,
potential
risk
to
aquatic
plants
may
have
been
underestimated.
Also,
open
literature
data
suggest
that
brown
algae
may
be
considerably
more
sensitive
than
green
algae.

a
Risks
are
similar
for
freshwater
and
saltwater
species.
12
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.

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.

Potential
Risk
to
Birds
Reproduction
Risk
conclusions
are
similar
to
those
presented
in
Table
1­
1;
however,
the
magnitude
of
the
exceedances
are
presumably
considerably
higher
than
exceedances
for
the
agricultural
uses.
Interpretation
of
the
risk
quotients
is
difficult
because
the
non­
agricultural
uses
may
be
spot
treatments.
Therefore,
birds
may
be
less
likely
to
consume
a
large
portion
of
their
daily
diet
in
treated
areas.

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.

Potential
Risk
to
Mammals
Chronic
Risk
conclusions
are
similar
to
those
presented
in
Table
1­
1.
Risk
quotients
are
presumably
considerably
higher
than
the
LOC;
however,
these
conclusions
are
based
on
a
toxicity
study
that
produced
a
free­
standing
NOAEC
(
no
effects
were
observed
in
the
study
at
any
concentration).
Therefore,
the
magnitude
of
LOC
exceedances
is
uncertain.

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
Risks
are
similar
to
those
presented
in
Table
1­
1
except
that
the
endangered
species
aquatic
plant
LOC
of
1
was
exceeded
for
vascular
plants.
The
aquatic
EECs
were
considered
conservative;
additional
use
information
would
allow
for
refinement
of
these
EECs.
13
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
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.
Reproduction
toxicity
study
in
mallard
ducks
(
71­
4)
High
A
mallard
reproduction
toxicity
study
has
not
been
submitted.
The
bobwhite
quail
study
resulted
in
LOC
exceedances
(
highest
RQ
=
11
for
agricultural
uses).
Tier
II
aquatic
plant
toxicity
studies
in
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
and
duckweed
have
been
submitted.
Studies
in
the
three
other
aquatic
plant
species
listed
are
required
for
herbicides
and
would
substantially
reduce
uncertainty
in
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
(
72­
4)
Low­
Moderate
Chlorate
is
practically
non­
toxic
to
fish
and
aquatic
invertebrates
after
acute
exposures,
and
did
not
produce
treatment­
related
effects
in
daphnids
at
concentrations
up
to
500
mg/
L.
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.
Field
dissipation
study
(
164­
1)
Low
(
alternative
study
proposed)
No
field
dissipation
data
have
been
submitted
to
the
Agency,
and
this
data
requirement
has
not
been
waived.
Although
the
persistence
of
chlorate
in
the
field
may
remain
as
an
uncertainty,
the
Agency
is
concerned
that
the
prolonged
use
of
sodium
chlorate
on
cotton
(
about
50
years)
may
have
altered
the
chemical
composition
of
soils
and/
or
ground.
Therefore,
retrospective
monitoring
data
of
soils
and/
or
ground
water
should
be
submitted
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.
14
Table
2­
1.
Selected
Factors
Considered
in
the
Ecological
Risk
Assessment
of
Sodium
Chlorate
Consideration
Sodium
Chlorate­
Specific
Data
Effect
on
Risk
Assessment
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.
Reproduction
studies
in
mallards
and
chronic
studies
in
fish
are
not
available.
These
endpoints
cannot
be
fully
evaluated.

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).
Toxicity
Database
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.
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
assesses
chronic
risk
from
exposure
to
granular
pesticides
on
a
case
by
case
basis.
15
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).
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.
Use
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.

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.
2
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
2
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)
16
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.

Table
2­
2.
Physical
and
Chemical
Properties
of
Chlorate
Physical
and/
or
Chemical
Property
Data
Selected
Synonyms
Soda
chlorate;
chloric
acid,
sodium
salt
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)
3
Melting
Point
248
E
C
Boiling
Point
Not
applicable.
Decomposes
above
300
E
C,
with
release
of
oxygen
(
violently)

Solubility
in
Water
1.0
x
106
mgL­
1
at
25
E
C
(
highly
soluble)
Dissociation
Constant
Fully
ionized
Vapor
Pressure,
25
E
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)

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
particulates4
and,

3
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.

4
Unless
they
chemisorb
to
soil
or
sediment
particulates.
Chemisorption
of
chlorate
is
unlikely.
17
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
chemistry5
of
chlorate
affects
its
behavior
in
soils
and
natural
water.
Therefore,
identification
of
the
conditions
(
pH;
redox
potential,
"
Eh"
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,
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
5
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.
18
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.
6
However,
its
soil
sterilizing
properties
could
have
adverse
effects
on
soil
quality
and
productivity
over
time.

Agricultural
Food/
Feed
Uses
Currently,
chlorate
is
used
primarily
as
a
harvest
aid
(
defoliant7,
desiccant8,
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.

6
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.

7
Defoliant:
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.

8
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.
19
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
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.
9
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.

9
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.
20
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
21
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)
10.
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.

10
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).
22
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).

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.
11
See
Section
3
(
Analysis)
for
a
discussion
of
chlorate's
relevant
environmental
11
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.
23
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
non­
agricultural
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
nonagricultural
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.

Attempts
were
made
to
refine
the
aquatic
EECs
using
higher
tier
models
such
as
PRZM
and
EXAMS12.
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
12
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.
24
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).
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.
25
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.

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
chlorate13.
The
conceptual
model
below
generically
depicts
the
potential
source
of
chlorate,
release
mechanisms,
receiving
media,
and
biological
receptors
for
chlorate's
use.

13
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.
26
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
27
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
pesticide­
induced
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.
28
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:
NOAEC
from
reproduction
study
in
bobwhite
quail.
TGAIb
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:
Reproduction
NOAEC
from
a
2­
generation
reproduction
toxicity
study
in
rats.
TGAIb
Freshwater
Aquatic
Organisms
Survival
and
reproduction
of
freshwater
fish
and
invertebrate
communities
Acute
Exposures:
Daphnia
Magna,
rainbow
trout,
and
bluegill
sunfish.

Chronic
Exposures:
Reproduction
NOAEC
in
daphnids.
No
chronic
studies
in
fish
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
semi­
aquatic
species
(
crops
and
noncrop
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
and
duckweed.
TGAI
a
LD50
=
Lethal
dose
to
50%
of
the
test
population.
NOAEC
=
No
observed
adverse
effect
concentration.
LOAEC
=
Lowest
observed
adverse
effect
concentration
LC50
=
Lethal
concentration
to
50%
of
the
test
population.
EC50
=
Effect
concentration
to
50%/
25%
of
the
test
population.
b
TGAI
=
Technical
grade
active
ingredient
29
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
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.
30
°
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)
14.
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.
Moreover,
the
impact
of
prolonged
use
of
chlorate
(
as
its
end­
product
chloride)
on
soils
and
surface
water
is
not
well
established.

Toxicity
°
Reproduction
studies
in
mallard
ducks,
chronic
studies
in
fish,
and
toxicity
studies
in
some
required
aquatic
plant
species
for
herbicides
have
not
been
submitted.

°
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
effects
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
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.

14
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
31
°
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.
15Chlorate
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.

°
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]
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.

15
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).
32
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
(
ClO3
­)
16.
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:

Redox
conditions
in
the
environment
Identification
of
electron
donors
(
reductants)
and
electron
acceptors
(
oxidizers)
in
the
environment
(
inorganic
and
organic).

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

Chlorate
is
more
stable
under
alkaline
than
acidic
conditions17.
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
16
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).

17
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.
33
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
(
Eh)
of
the
media.
The
redox
potential
can
also
be
expressed
in
a
pE
scale,
which
is
the
notation
used
in
this
assessment18.
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.

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.

18
The
pE
(
pE=
­
log
E)
scale
is
analogous
to
that
of
pH.
34
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).

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
35
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
reactions19.
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
(
NO2
­
;
NH4
+);
S(­
II)
(
e.
g
HS­,
S
2­;
polysulfido
species),
and
others.
Major
chemical
species
associated
with
oxidizing
environments
are
dissolved
dioxygen
(
O2),
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)
20.

19
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.

20
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.
36
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).

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)
Low
probability
and
may
be
considered
as
a
transient
chemical
species
Low
probability.
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
­
37
1
Forms
only
in
solution
(
i.
e.,
cannot
be
isolated)
2
Disproportionation
reactions21
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
E
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
E
,
and
other
pertinent
information).
Although
these
chemical
species
can
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
reductants22.

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.

21
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.

22
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
be
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.
38
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
states23
(
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
equilibrium24
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.
25
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.
Therefore,
it
was
assumed
that
unchanged
chlorate
runs
off
into
surface
water,
where
it
remains
as
chlorate.

23
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).

24
For
a
definition
of
activity
and
activity
coefficients
see
Appendix
B­
1
25
20,000
m3
(
20,000,000
L)
water
volume,
2­
meter
deep
pond
with
no
outlets
39
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)
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
40
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.

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)
52
to
650
lbs
a.
i./
Acre
(
single
applications)
a
All
non­
Agricultural
uses
3,100
to
39,000
a
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.
41
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
42
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.
For
granular
applications,
estimation
of
pesticide
loading
per
unit
area
(
mg/
ft
)
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:

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.
44
°
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
could
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.

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.
45
3.3.
Ecological
Effects
Characterization
3.3.1.
Aquatic
Toxicity
Fish
Supplemental26
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
publicly
available
toxicity
data
on
chlorate
as
reported
in
EPA's
ECOTOX
database.
27
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
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
in
fish
have
been
submitted
to
the
Agency
or
were
identified
in
the
ECOTOX
database.

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
26
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.

27
http://
www.
epa.
gov/
ecotox
46
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.

Aquatic
Plants
An
acceptable
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.

In
an
acceptable
static
7­
day
acute
toxicity
study
in
freshwater
aquatic
vascular
plants
(
Lemna
minor),
sodium
chlorate
produced
an
EC50
of
43
mg/
L
and
a
NOAEC
of
3.1
mg/
L
(
MRID
46687601).

No
studies
in
the
following
plant
species
have
been
submitted,
which
are
required
for
herbicides:
Skeletonema
costatum
(
a
marine
diatom),
Anabaena
flos­
aquae
(
a
blue­
green
bacterium),
and
a
freshwater
diatom.
47
Publicly
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
(
approximately
1
mg/
L)
and
NOAEC
of
<
0.005
mM
(
approximately
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.
28
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.

Table
3­
11.
Aquatic
Toxicity
Profile
for
Sodium
Chlorate
Endpoint
Environment/
S
pecies
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
28
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.
48
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.
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
NOAEC:
500
mg/
L
MRID
46731301
A
LOAEC
was
not
observed;
no
treatmentrelated
effects
were
observed
at
any
concentration.
Toxicity
to
Aquatic
Plants
Freshwater
Selenastrum
capricornutum
EC50:
133
mg/
L
NOAEC:
62.5
mg/
L
MRID
418872­
01
Acceptable.
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).
Lemna
minor
EC50:
43
mg/
L
NOAEC:
3.1
mg/
L
EC05:
2.3
mg/
L
MRID
46687601
Acceptable
study.

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
49
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.

The
one­
generation
reproductive
toxicity
of
sodium
chlorate
was
studied
in
bobwhite
quail
(
MRID
46729701).
Egg
production
and
thickness,
embryonic
survival
(
early,
late,
and
at
hatch),
and
hatchling
body
weights
were
affected
by
treatment
at
the
964
mg
ai/
kg
diet
level.
The
NOAEC
was
271
mg/
kg­
diet
(
ppm).

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.

In
an
Acceptable
2­
generation
reproduction
study
(
MRID
46524001),
oral
administration
of
sodium
chlorate
(
99.68%
a.
i.)
did
not
result
in
frank
reproductive
effects
at
daily
doses
of
500
mg/
kg­
bw
and
lower.
Consequently,
the
reproductive
NOAEL
is
500
mg/
kg/
day.
A
dose
of
500
mg/
kg­
bw
corresponds
to
approximately
10,000
ppm
assuming
that
a
rat
consumes
approximately
5%
of
its
body
weight
daily
(
U.
S.
EPA
2004).
Effects
were
observed
at
daily
doses
of
70
mg/
kg­
bw
and
500
mg/
kg­
bw
including
effects
on
the
blood
and
thyroid.
However,
these
effects
are
not
clearly
directly
related
to
reduced
reproductive
success
or
survival.
Therefore,
a
reproduction
NOAEL
of
500
mg/
kg­
bw
was
used
in
risk
estimation.

In
addition,
multiple
subchronic
and
chronic
studies
are
available
(
Appendix
M).
EFED
does
not
use
these
types
of
studies
to
calculate
risk
quotients.
However,
these
data
provide
qualitative
characterization
to
the
mammalian
risk
assessment
(
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
approximately
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.
50
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
dose­
response
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
Bobwhite
quail
271
ppm
MRID
46729701
Acceptable
study.
The
LOAEC
was
964
ppm
based
on
effects
on
egg
production
and
thickness,
embryonic
survival
(
early,
late,
and
at
hatch),
and
hatchling
body
weight.
Acute
toxicity
to
mammals
Rat
LD50:
>
5000
mg/
kg­
bw
MRID
41819901
Acceptable
study.
At
5000
mg/
kg­
bw,
1/
10
animals
died.
Reproduction
Toxicity
in
Mammals
Laboratory
Rat
NOAEL:
500
mg/
kg­
bw
(
highest
dose
tested)
MRID
46524001
Acceptable
study.
Effects
were
observed
at
70
mg/
kg­
bw
and
above.
However,
those
effects,
which
included
thyroid
effects,
are
not
clearly
associated
with
reduced
reproductive
success
or
survival.
Chronic
toxicity
to
mammals
Laboratory
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.
51
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
EC25
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
EC25
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.

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
diet29
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.

29
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).
52
4.
Risk
Characterization
4.1
Aquatic
Organisms
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
(
418872­
03).
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
Up
to
0.91
mg/
L
1000
mg/
L
<
0.01
All
non­
Agricultural
Up
to
39
mg/
L
1000
mg/
L
<
0.04
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.
53
4.1.2.
Aquatic
Invertebrates
Risk
Estimation
Risk
quotients
based
on
an
EC50
from
the
acute
and
chronic
toxicity
studies
described
in
Section
3
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.

Table
4­
2.
Acute
and
Chronic
Freshwater
Aquatic
Invertebrate
Risk
Quotients
Agricultural
and
Non­
Agricultural
Uses
of
Sodium
Chlorate
Use
Application
Rate
Maximum
EEC
Acute
EC50a
Chronic
NOAEC
Acute
RQ
Chronic
RQ
LOC
Exceedance
Agricultural
uses
All
labeled
rates
Up
to
0.91
mg/
L
920
mg/
L
500
mg/
L
<
0.01
<
0.01
None
Non­
agricultural
uses
All
labeled
rates
Up
to
39
mg/
L
920
mg/
L
500
mg/
L
<
0.042
0.080
None
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.
The
chronic
NOAEC
was
500
mg/
L;
no
treatmentrelated
effects
were
observed
at
any
concentration
in
this
study
(
MRID
46524001).

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
Acute
LC50:
>
1000
mg/
La
<
0.01
Non­
agricultural
uses
All
labeled
rates
39
mg/
L
Acute
LC50:
>
1000
mg/
La
<
0.04
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.
54
4.1.3.
Aquatic
Plants
Risk
Estimation
Risk
quotients
based
on
an
algal
and
duckweed
EC50s
and
NOAECs
and
EECs
calculated
by
GENEEC­
2
are
in
Table
4­
4
and
Table
4­
5
below.

Table
4­
4.
Non­
Endangered
Species
Aquatic
Plant
Risk
Quotients
Agricultural
and
Non­
Agricultural
Uses
Use
Maximum
Peak
EEC
Algal
EC50
Duckweed
EC50
Algal
RQ
Duck
weed
RQ
LOC
Exceedance
Agricultural
uses
up
to
0.9
mg/
L
133
mg/
L
43
mg/
L
<
0.01
0.02
None
Non­
Agricultural
Up
to
39
mg/
L
133
mg/
L
43
mg/
L
Up
to
0.29
0.91
None
Table
4­
5.
Endangered
Species
Algal
Risk
Quotients
Agricultural
and
Non­
Agricultural
Uses
Use
Maximum
Peak
EECa
Algal
NOAEC
Duckweed
NOAEC
Algal
RQ
Duckweed
RQ
LOC
Exceedance
Agricultural
Up
to
0.9
mg/
L
62.5
mg/
L
3.1
mg/
L
Up
to
0.014
Up
to
0.29
None
Non­
Agricultural
Up
to
39
mg/
L
62.5
mg/
L
3.1
mg/
L
Up
to
0.62
Up
to
12.6
Vascular
plant
LOC
of
1.0
Risk
Description
­
Interpretation
of
Direct
Effects
No
algal
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
algae
is
lower
than
the
Agency's
level
of
concern
for
all
uses
assessed.
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
(
approximately
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.

Risk
quotients
for
the
surrogate
vascular
plant,
duckweed
(
Lemna
minor),
were
lower
than
the
Agency's
LOC
for
endangered
and
non­
endangered
plants
for
all
agricultural
uses
assessed.
The
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.
55
endangered
species
LOC
was
exceeded
for
sodium
chlorate's
non­
agricultural
uses.
The
highest
RQ
was
approximately
13.
The
most
sensitive
endpoint
in
this
study
was
reduction
in
dry
weight.
At
the
highest
EEC
of
39
mg/
L,
the
magnitude
of
effect
would
be
expected
to
be
somewhat
greater
than
40%
because
a
41%
reduction
in
dry
weight
was
observed
at
29
mg/
L
in
the
submitted
study.
However,
as
previously
discussed,
EECs
from
the
non­
agricultural
uses
are
considered
conservative.

No
studies
in
the
following
plant
species
have
been
submitted,
which
are
required
for
herbicides:
Skeletonema
costatum
(
a
marine
diatom),
Anabaena
flos­
aquae
(
a
blue­
green
bacterium),
and
a
freshwater
diatom.

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.
56
 
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.

 
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.

4.1
Risks
to
Birds,
Acute
and
Chronic
Exposures
57
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.

Table
4­
6
below
presents
avian
reproduction
risk
quotients.
These
RQs
were
based
on
a
NOAEC
of
271
ppm
(
MRID
46729701).
At
the
LOAEC
of
964
ppm,
effects
on
egg
production
and
thickness,
embryonic
survival
(
early,
late,
and
at
hatch),
and
hatchling
body
weight
occurred.
Rqs
for
all
crops
and
all
avian
food
items
assessed
except
fruits,
pods,
seeds,
and
small
insects
exceeded
the
Agency's
LOC
of
1.0.
The
highest
RQ
was
11.

Table
4­
6.
Avian
Reproduction
Risk
Quotients
Based
on
a
NOAEC
of
271
ppm
(
MRID
46729701)
and
Estimated
Upper
90th
Percentile
Residue
Levels
Crops
Application
Rate
(
No.
Of
Applications
/
Interval)
Predicted
90th
Percentile
Residue
Levels
short
grass
tall
grass
broadleaf
forage,
small
insects
fruit,
pods,
seeds,
small
insects
Chili
peppers;
white/
Irish
potatoes
12.5
lbs
a.
i./
Acre
Single
application
EEC:
3000
RQ:
11
EEC:
1400
RQ:
5.2
EEC:
1700
RQ:
6.3
EEC:
190
RQ:
0.7
Cotton
7.5
lbs
a.
i./
Acre
(
2/
30)
EEC:
2800
RQ:
10
EEC:
1300
RQ:
4.8
EEC:
1600
RQ:
5.9
EEC:
170
RQ:
0.63
Corn;
flax,
guar;
southern
peas;
rice;
safflower;
sorghum;
soybeans;
sunflower
7.5
lbs
a.
i./
Acre
Single
application
EEC:
1800
RQ:
6.6
EEC:
830
RQ:
3.1
EEC:
1000
RQ:
3.7
EEC:
110
RQ:
0.41
Agricultural
fallow
land;
dried
beans;
corn;
cucurbitsa,
flax,
gourds;
guar;
southern
peas;
white/
Irish
potatoes;
rice;
safflower;
sorghum;
soybeans;
sunflower
6
lbs
a.
i./
Acre
Single
application
EEC:
1400
RQ:
5.2
EEC:
660
RQ:
2.4
EEC:
810
RQ:
3.0
EEC:
90
RQ:
0.33
a
The
application
rate
for
cucurbits
is
6.1875
lbs
a.
i./
Acre
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
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.
58
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.

Chronic
RQs
exceeded
the
Agency's
LOC
of
1.0
for
all
agricultural
uses
assessed
for
short
grass,
tall
grass,
broadleaf
forage,
and
small
insects.
EECs
for
a
majority
of
the
uses
and
classes
of
food
items
were
higher
than
the
LOAEC
in
bobwhite
quail
of
964
ppm.
At
the
LOAEC,
frank
reproductive
effects
occurred
including
a
67%
reduction
in
eggs
laid
and
64%
reduction
in
number
of
hatchlings
per
egg
laid
(
other
reproductive
effects
were
observed
as
well).
Therefore,
the
magnitude
of
potential
effects
could
be
greater
than
67%
if
birds
are
exposed
during
the
reproductive
season.
The
duration
of
exposure
needed
to
produce
reproductive
effects
is
an
uncertainty.

Risk
quotients
were
not
presented
for
chlorate's
non­
agricultural
uses.
However,
risk
quotients
would
be
considerably
higher
for
birds
foraging
where
chlorate
is
applied
at
the
rates
assessed
for
the
non­
agricultural
uses.
EECs
ranged
from
12,500
to
125,000,
which
would
result
in
risk
quotients
of
46
to
460.
The
size
of
the
treated
areas
for
these
uses
is
uncertain;
therefore,
the
likelihood
that
a
bird
would
consume
100%
of
its
diet
from
a
treated
area
is
uncertain.

4.3
Risk
to
Mammals,
Acute
Exposures
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.
Risk
quotients
would
be
lower
than
the
values
in
Tables
4­
6
and
4­
7.
59
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.
60
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
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
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
61
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
2.4E8
mg
a.
i./
Acre
÷
1.6E5
kg
soil/
Acre
=
1500
mg
a.
i./
kg­
soil
This
application
rate
is
only
labeled
for
pre­
paving,
which
is
not
likely
to
result
in
exposure
to
non­
target
terrestrial
animals.
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:

32
Campbell
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)
62
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
370
mg/
kg­
day
for
a
15­
gram
mammal
(
5.6
mg/
day
÷
0.015
kg
=
370
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
and
adjusted
reproduction
NOAEL
of
1100
mg/
kg­
bw
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
up
to
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
overestimation
of
exposure
and
risk.

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.

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.
63
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
animals
resulting
in
higher
chlorate
body
burdens
in
these
animals
(
Klingman,
1977
as
cited
by
the
Agricultural
Marketing
Service
of
USDA
(
2000);
on­
line
at
http://
www.
ams.
usda.
gov/
nop/
NationalList/
TAPReviews/
SodiumChlorate.
pdf).
64
Other
uncertainties
in
this
assessment
are
presented
in
Section
4.7.

4.4.
Potential
Reproduction
Risk
to
Mammals
A
free­
standing
NOAEL
of
500
mg/
kg­
day
was
observed
in
a
2­
generation
reproduction
toxicity
study
in
rats.
Resulting
risk
quotients
are
in
Table
4­
9
below.
Interpretation
of
these
risk
quotients
is
difficult
given
that
the
available
2­
generation
toxicity
study
did
not
observe
reproduction
effects
at
any
dose
tested.
Therefore,
the
reproduction
NOAEL
could
be
considerably
higher
than
500
mg/
kg­
bw.
However,
LOCs
were
exceeded
for
all
weight
classes
of
mammals
for
at
least
one
food
item.

Table
4­
9.
Mammalian
Reproduction
Risk
Quotients
Use
Food
Item
RQ
15­
gram
mammal
NOAELAdj:
1100
mg/
kg­
bw
RQ
35­
gram
mammal
NOAELAdj:
890
mg/
kg­
bw
RQ
1000­
gram
mammal
NOAELAdj:
380
mg/
kgbw
Single
application
of
12.5
lbs
a.
i./
Acre
Chili
peppers;
white/
Irish
potatoes
Short
Grass
EEC:
2900
RQ:
2.6
EEC:
1980
RQ:
2.2
EEC:
460
RQ:
1.2
Tall
Grass
EEC:
1300
RQ:
1.2
EEC:
910
RQ:
1.0
EEC:
210
RQ:
0.55
Broadleaf
plants/
sm
insects
EEC:
1600
RQ:
1.5
EEC:
1100
RQ:
1.3
EEC:
260
RQ:
0.67
Fruits/
pods/
lg
insects
EEC:
180
RQ:
0.16
EEC:
120
RQ:
0.14
EEC:
29
RQ:
0.07
7.5
lbs
a.
i./
Acre
(
2
applications,
30­
day
interval)
Cotton
Short
Grass
EEC:
2700
RQ:
2.4
EEC:
1800
RQ:
2.1
EEC:
430
RQ:
1.1
Tall
Grass
EEC:
1200
RQ:
1.1
EEC:
840
RQ:
0.95
EEC:
195
RQ:
0.51
Broadleaf
plants/
sm
insects
EEC:
1500
RQ:
1.4
EEC:
1000
RQ:
1.2
EEC:
240
RQ:
0.62
Fruits/
pods/
lg
insects
EEC:
170
RQ:
0.15
EEC:
120
RQ:
0.13
EEC:
27
RQ:
0.07
7.5
lbs
a.
i./
Acre
(
single
application)
a
Short
Grass
EEC:
1700
RQ:
1.6
EEC:
1200
RQ:
1.3
EEC:
280
RQ:
0.72
Tall
Grass
EEC:
790
RQ:
0.72
EEC:
540
RQ:
0.61
EEC:
130
RQ:
0.33
Broadleaf
plants/
sm
insects
EEC:
970
RQ:
0.88
EEC:
670
RQ:
0.75
EEC:
150
RQ:
0.40
Corn;
flax,
guar;
southern
peas;
rice;
safflower;
sorghum;
soybeans;
sunflower
Agricultural
fallow
land;
dried
beans;
corn;
cucurbitsa,
flax,
gourds;
guar;
southern
peas;
white/
Irish
potatoes;
rice;
safflower;
sorghum;
soybeans;
sunflower
(
see
Table
note
a)
Fruits/
pods/
lg
insects
EEC:
110
RQ:
0.10
EEC:
74
RQ:
0.08
EEC:
17
RQ:
0.04
a
EECs
and
Rqs
are
similar
for
the
6.0
and
7.5
single
applications,
and
LOC
exceedances
are
equivalent;
therefore,
only
results
from
the
single
application
of
7.5
lbs
a.
i./
Acre
are
presented.
65
In
addition,
the
available
subchronic
data
suggest
that
mammals
may
be
at
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).

Reproduction
risk
quotients
were
not
calculated
for
chlorate's
non­
agricultural
uses.
However,
based
on
the
high
application
rates
and
resulting
high
potential
EECs,
risks
from
chlorate's
nonagricultural
uses
could
be
considerably
higher
than
risks
presented
for
agricultural
uses.

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.
66
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
underestimated
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
studies
in
mallard
ducks
are
available.
Therefore,
the
relative
sensitivity
of
these
two
surrogate
species
has
not
been
evaluated.
Also,
the
2­
generation
reproduction
toxicity
study
did
not
observe
any
toxic
effects
at
any
dose
tested
(
up
to
500
mg/
kg­
bw/
day).
Therefore,
the
reproduction
NOAEL
could
be
higher
than
500
mg/
kg­
bw/
day.

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.
67
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:

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
35
Hayes,
Wayland
J.,
Jr.
Pesticides
Studied
in
Man.
Baltimore/
London:
Williams
and
Wilkins,
1982..
68
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,
chlorite
is
expected
to
be
a
transient
environmental
redox
product,
and
the
currently
available
data
do
not
allow
for
a
realistic
estimation
of
the
amount
of
chlorite
that
may
form
in
the
environment.

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
non­
agricultural
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
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.

The
reproduction
study
in
bobwhite
quail
suggests
that
clear
reproduction
effects
occurred
at
964
ppm.
EECs
in
this
assessment
were
generally
considerably
higher
than
964
ppm
for
agricultural
and
non­
agricultural
uses.
Therefore,
potential
direct
effects
to
listed
bird
species
is
above
the
Agency's
concern
level
for
all
uses.

36
The
48­
hour
acute
EC50
in
daphnids
is
0.15
mg/
L
(
MRID
940680­
09).
69
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.
However,
there
is
uncertainty
regarding
the
high
EECs
resulting
from
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
Mammals
Even
though
no
reproduction
effects
were
observed
at
up
to
500
mg/
kg­
bw/
day
in
the
submitted
2­
generation
reproduction
toxicity
study
in
mammals
(
the
highest
concentration
tested),
the
Agency
cannot
preclude
risk
to
mammals
because
potential
exposure
levels
in
some
mammalian
weight
classes
are
higher
than
the
highest
dose
tested
for
all
agricultural
and
non­
agricultural
uses.

Based
on
the
potential
use
sites,
EFED
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.

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.
70
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.
71
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.

073301
D303884
REDRevised
