Memorandum
Amended
8/
26/
00
from
01/
13/
00
from
10/
07/
99
from
8/
26/
99
To:
Christina
Scheltema,
Chemical
Review
Manager
Special
Review
&
Reregistration
Division
7508W
From:
EFED
Disulfoton
Team
Henry
Craven,
Biologist
John
Jordan,
Microbiologist
James
Wolf,
Soil
Scientist
Mary
Frankenberry,
Statistician
Thru:
Arnet
Jones,
Chief
Environmental
Risk
Branch
III
Environmental
Fate
&
Effects
Division
7507C
Subject:
Reregistration
Eligibility
Document
for
Disulfoton
(
D237134)

Attached
to
this
memorandum
is
the
revised
EFED
RED
chapter
for
disulfoton.
EFED
has
reviewed
the
public
comments
and
has
modified
the
chapter
in
response
to
the
comments.
This
transmittal
memo
summarizes
EFED
 
s
findings
and
recommendations
for
potential
mitigation,
monitoring
and
labeling.

The
risk
assessment
was
performed
by
evaluating
use
information
listed
in
both
the
BEAD
LUIS
report
for
disulfoton
as
well
as
information
supplied
by
Bayer
Corporation,
the
major
registrant
for
disulfoton
products,
and
current
labels
(
EPA
Reg.
No.
3125­
172;
3125­
307)
.

Background
Disulfoton
is
an
organophosphate
insecticide/
acaricide
used
on
a
variety
of
terrestrial
food
crops,
terrestrial
feed
crops,
and
terrestrial
nonfood
crops.
Disulfoton
is
formulated
as
15%
granules,
8%
emulsifiable
systemic,
95%
cotton
seed
treatment,
systemic
granules
(
1,
2,
5,
10%
)
,
and
68%
concentrate
for
formulating
garden
products.
Directions
regarding
application
intervals,
number
of
applications
and
total
application
per
year
or
crop
cycle
are
not
always
specified
by
the
label.

1
Environmental
Fate
Summary
Parent
disulfoton
has
low
to
intermediate
potential
mobility
(
Kocs
386­
888)
and
is
neither
persistent
(
average
(
half­
life)
T1/
2
is
4.8
days)
nor
volatile.
Disulfoton
photo­
degrades
within
2.4
days
on
soil
and
in
water
under
natural
sunlight
the
T1/
2
is
4
days.
Disulfoton
is
essentially
stable
to
hydrolysis
at
20
E
C
at
pH
5,
7,
and
9,
but
hydrolyzes
much
more
rapidly
at
40
E
C.
Soil
applied
disulfoton
will
be
degraded
rapidly
oxidized
by
chemical
reaction
and
microbial
metabolism
to
its
corresponding
D.
sulfoxide
and
D.
sulfone.
Aerobic
soil
metabolism
data
indicated
that
the
sulfoxide
(
T1/
2
>
17days)
and
sulfone
(
T1/
2
>
120
days)
degradates
of
disulfoton
are
more
persistent
and
mobile
then
parent
disulfoton.
In
a
recently
submitted
leaching
study,
nine
additional
metabolism
products
were
identified,
at
least
three
may
have
human
toxicity
issues.
Field
dissipation
information
also
indicates
that
the
degradates
may
persist
longer
in
the
environment,
D.
sulfoxide
has
a
half­
life
of
8
to
10
weeks
and
D.
sulfone
remained
fairly
stable
over
a
294­
day
period.
There
is
insufficient
environmental
fate
information
on
the
degradates
to
fully
characterize
their
fate
and
transport.
The
half­
life
for
total
disulfoton
residues
was
greater
than
170
days.
Open
literature
suggests
that
D.
sulfoxide
can
be
reduced
to
back
to
disulfoton.
Information
is
not
available
to
assess
the
significance
of
the
reduction
of
D.
sulfoxide.
Aerobic
and
anaerobic
aquatic
metabolism
studies
which
could
provide
valid
model
inputs
for
the
degradates
disulfoton
sulfone
and
disulfoton
sulfoxide
have
not
been
submitted.
Although
the
registrant
provided
the
Agency
with
additional
information
concerning
the
fate
of
disulfoton
residues
in
water
under
controlled
artificial
conditions
(
MRID
43568501
and
LaCorte
et
al.
,
1995)
,
this
information
is
limited
and
should
not
be
used
for
model
inputs.
Specifically,
these
studies
provide
information
concerning
the
combined
effects
of
hydrolysis,
photolysis,
and
metabolism,
with
photodegradation
contributing
significantly
to
the
dissipation.

Water
Resources
Summary
The
Water
Resources
Assessment
considered
the
potential
of
disulfoton
and
its
degradates,
D.
sulfoxide
and
D.
sulfone,
to
contaminate
ground
water,
surface
water,
and
drinking
water
from
labeled
uses.
The
assessment
included
a
TIER
II
(
PRZM/
EXAMS)
analysis
which
estimates
environmental
concentrations
(
EECs)
in
surface
water
for
disulfoton
parent
and
for
total
disulfoton
residues,
TDR
(
sum
of
disulfoton,
sulfoxide,
and
sulfone)
,
applied
at
the
maximum
label
rate
and
number
of
applications
to
barley,
cotton,
potatoes,
spring
wheat,
and
tobacco.
The
OPP
standard
farm
pond
was
used
for
ecological
exposure
assessment
and
the
Index
Reservoir
and
Percent
Crop
Area
(
PCA)
were
factored
into
the
drinking
water
assessment.
These
crops
represent
major
uses
and
generally
reflect
the
highest
use
rates
and
total
amounts.
The
potential
for
disulfoton
parent
residues
(
and
TDR)
to
contaminate
ground
water
was
assessed
using
the
EFED
ground­
water
concentration
screening
model
(
SCI­
GROW)
and
monitoring
data
available
in
EFED
 
s
Pesticides
in
Ground
Water
Data
Base
(
PGWDB)
,
EPA'
s
STORET
data
base,
and
in
the
USGS
National
Water
Quality
Assessment
Program
(
NAWQA)
.
Surface­
water
monitoring
data
sources
available
in
the
USGS
NAWQA
program
and
the
EPA
 
s
STORET
data
base
were
also
considered.

Disulfoton
is
likely
to
be
found
in
runoff
water
and
sediment
from
treated
and
cultivated
fields.

2
The
fate
of
disulfoton
and
its
degradates
once
in
surface
water
and
sediments,
and
the
likely
concentrations
therein,
cannot
be
modeled
with
a
high
degree
of
certainty
since
data
are
not
available
for
the
aerobic
and
anaerobic
aquatic
degradation
rates.
Estimates
of
disulfoton
concentrations
in
ground
water
did
not
consider
the
anaerobic
soil
metabolism,
as
studies
have
been
submitted
by
the
registrant,
but
have
not
reviewed
by
EFED.
The
anaerobic
soil
metabolism
rate
for
disulfoton
appears
to
be
slower
than
the
aerobic
soil
metabolism
rate.
For
this
assessment,
the
aerobic
aquatic
metabolism
rate,
required
by
EXAMS,
was
estimated
by
using
EFED'
s
recommended
guidance
to
estimate
an
aerobic
aquatic
metabolism
rate
from
aerobic
soil
metabolism
rates
(
e.
g.
,
multiply
the
soil
aerobic
metabolism
rate
used
in
PRZM
by
0.5
(
doubles
the
half­
life)
)
.
In
lieu
of
actual
data
on
persistence
of
disulfoton
in
an
aquatic
environment,
the
assumed
aquatic
metabolism
rate
for
EXAMS
will
reduce
the
estimated
concentrations,
but
not
the
uncertainty.
Considering
the
relatively
rapid
rate
of
microbial
degradation
in
the
soil
and
aquatic
photolysis
in
surface
water,
parent
disulfoton
may
degrade
fairly
rapidly,
whereas
the
degradates
are
more
persistent
and
may
not
degrade
as
rapidly
in
water.
As
noted
above
the
registrant
has
submitted
additional
information
suggesting
a
fairly
rapid
degradation
of
disulfoton
and
D.
sulfoxide
and
D.
sulfone
in
natural
water
under
artificial
conditions.

Sorption
data
(
reflection
of
mobility,
e.
g.
,
Kds)
are
also
not
available
for
the
sulfoxide
and
sulfone
degradates
(
and
other
degradates)
,
were
considered
to
be
equal
to
the
parent
in
the
modeling.
Typically,
however,
the
D.
sulfoxide
and
D.
sulfone
degradates
are
more
mobile
than
the
parent.
The
peak
concentrations
of
parent
disulfoton
appear
capable
of
being
quite
high,
especially
when
high,
foliar
application
rates
are
used
and
coincide
with
a
rainfall
event.
Limited
monitoring
confirms
this
(
VA,
CO)
.
A
large
degree
of
latitude
available
in
the
disulfoton
labels
also
allows
for
wide
variation
in
possible
application
rates,
total
amounts
of
disulfoton
applied,
application
methods,
and
intervals
between
applications.
Lower
application
rates
would
result
in
lower
estimated
concentrations
(
EECs)
.
Additionally,
considerable
uncertainty
exists
because
the
percent
crop
area
or
PCA
value
was
not
known,
thus,
the
default
value
was
applied.

The
low
concentrations
typically
reported
in
available
ground
water
and
surface
water
monitoring
data
of
parent
disulfoton
tends
to
confirm
fairly
rapid
degradation
and
low
mobility,
but
do
not
preclude
potentially
high
peak
values
(
few
reported
high
values)
.
Although
no
assessment
can
be
made
for
degradates
due
to
lack
of
data,
limited
data
suggests
that
the
degradates
are
more
persistent
than
disulfoton,
suggesting
their
presence
in
water
for
a
longer
period
of
time
than
the
parent
Surface
Water
Modeling:

In
the
Tier
II
PRZM/
EXAMS
assessment,
the
overall
estimate
of
the
multiple
year
mean
concentrations
of
disulfoton
in
a
farm
pond
over
multiple
years
simulated
ranged
from
0.21
µ
g/
L
for
two
applications
at
the
maximum
rate
(
1.00
lb
ai/
A)
to
barley
in
Virginia
to
1.14
µ
g/
L
for
potatoes
in
Maine
with
three
applications
at
the
maximum
application
rate
(
1.00
lb
ai/
A)
.
Maximum,
or
peak,
estimated
concentrations
of
26.75
µ
g/
L
occurred
for
one
4.00
lb.
ai/
ac
application
of
disulfoton
to
tobacco.
For
the
other
scenarios,
the
maximum
concentrations
ranged
from
7.14
to
18.46
µ
g/
L.

3
The
estimated
drinking
water
concentrations
using
the
Index
Reservoir
(
IR)
and
PCA
(
PCA)
concepts
for
the
same
scenarios
were
evaluated.
The
long
term
mean
of
the
parent
disulfoton
concentration
in
the
Index
Reservoir
and
by
PCA
ranged
from
0.23
to
1.31
µ
g/
L
for
cotton
and
tobacco,
respectively.
The
1­
in­
10
year
estimated
annual
mean
concentration
ranged
from
0.43
to
2.77
µ
g/
L
for
cotton
and
tobacco,
respectively.
The
peak
1­
in­
10
year
estimated
drinking
water
concentration
for
parent
disulfoton
ranged
from
7.13
to
44.20
µ
g/
L.

The
Tier
II
modeling
results
from
PRZM/
EXAMS
fall
within
the
range
of
concentrations
for
surface
water
reported
in
the
STORET
database
(
0.0
to
100
µ
g/
L,
96
percent
of
8137
samples
were
reported
as
less
than
16
µ
g/
L)
,
a
Virginia
monitoring
study
(
0.37
to
6.11
µ
g/
L)
and
NAWQA
(
0.010
to
0.060
µ
g/
L)
.
But
because
some
of
the
data
in
STORET
have
a
high
degree
of
uncertainty
because
many
samples
were
only
listed
as
 
actual
value
is
known
to
less
than
given
value
 
,
the
maximum
concentration
of
samples
was
not
always
known
(
see
Appendix
III)
.
The
modeled
concentration
estimates
are
generally
greater
than
those
seen
in
the
monitoring
data.
The
modeling
results
therefore
cannot
be
confirmed
by
the
monitoring
data.

Because
the
degradates
of
disulfoton
(
including
oxygen
analogs)
:
sulfoxide
and
sulfone
are
also
toxic,
the
EECs
of
the
total
disulfoton
residue
(
TDR)
in
a
farm
pond
was
also
considered.
The
overall
estimated
of
the
multiple
year
mean
concentrations
of
TDR
in
a
farm
pond
over
multiple
years
simulated
ranged
from
3.89
µ
g/
L
for
two
applications
at
the
maximum
rate
(
1.00
lb
ai/
A)
to
barley
in
Virginia
to
9.32
µ
g/
L
for
tobacco
in
Georgia
with
one
application
at
the
maximum
application
rate
(
4.00
lb
ai/
A)
.
Maximum,
or
peak,
estimated
TDR
concentrations
of
58.47
µ
g/
L
occurred
for
one
4.00
lb.
ai/
ac
application
of
disulfoton
to
tobacco.
For
the
other
scenarios,
the
maximum
TDR
concentrations
ranged
from
15.32
to
52.93
µ
g/
L.
There
are
no
monitoring
data
to
evaluate
these
concentration
estimates
from
PRZM/
EXAMS
modeling.

Total
disulfoton
residues
using
the
IR
and
PC
concepts
were
also
considered
for
drinking
water.
The
long
term
mean
of
the
total
disulfoton
residues
(
TDR)
in
the
Index
Reservoir
and
by
PCA
ranged
from
2.55
to
10.42
µ
g/
L
for
cotton
and
potatoes,
respectively.
The
1­
in­
10
year
estimated
annual
mean
TDR
concentrations
in
the
IR
ranged
from
5.10
to
16.72
µ
g/
L
for
cotton
and
potatoes,
respectively.
The
peak
1­
in­
10
year
estimated
TDR
concentrations
in
the
IR
ranged
from
20.83
to
104.92
µ
g/
L.
There
are
no
monitoring
data
to
evaluate
these
concentration
estimates
from
PRZM/
EXAMS
modeling.

Uncertainty
surrounds
these
estimates
because
the
sites
selected
for
modeling
represent
sites
though
to
be
representative
of
vulnerable
sites.
Additionally,
the
IR
was
generic
(
to
each
scenario)
and
data
to
fully
understand
of
the
fate
of
disulfoton
and
disulfoton
residues
is
available.
Evidence
suggests
that
the
concentrations
will
not
be
as
high
as
suggest
by
the
modeled
estimates.
The
PCA
values
have
been
estimated
by
OPP
for
spring
wheat
(
0.56)
and
cotton
(
0.20)
.
The
default
for
value
for
all
agricultural
land
of
0.87
was
used
for
the
barley,
potatoes,
and
tobacco
scenarios.
Better
estimates
of
the
PCA
for
these
crops
would
reduce
the
uncertainty
associated
with
the
estimated
drinking
water
concentrations.

4
Ground
Water
Modeling:

The
maximum
disulfoton
concentration
predicted
in
ground
water
by
the
SCI­
GROW
model
(
using
the
maximum
rate
4
lb.
a.
i.
/
ac
and
2
applications
­
potatoes)
was
0.05
µ
g/
L.
The
maximum
total
disulfoton
residue
concentration
predicted
in
ground
water
by
the
SCI­
GROW
model
for
the
same
scenario
is
3.19
µ
g/
L.
The
SCI­
GROW
model
represents
a
"
vulnerable
site"
,
but
not
necessarily
the
most
vulnerable,
treated
(
here)
with
the
maximum
rate
and
number
of
disulfoton
applications,
while
assuming
conservative
environmental
properties
(
90
percent
upper
confidence
bound
on
the
mean
aerobic
soil
half­
life
and
an
average
Koc
value)
.
Monitoring
data
has
reported
a
few
disulfoton
concentrations
higher
than
those
estimated
by
SCI­
GROW.

Disulfoton
Monitoring
Data:

Based
upon
the
fate
properties
of
disulfoton
parent,
which
is
not
very
persistent,
or
mobile
you
would
not
expect
to
observe
disulfoton
in
ground
water.
The
Pesticides
in
Ground
Water
Data
Base
(
USEPA,
1992)
summarizes
the
results
of
a
number
of
ground­
water
monitoring
studies
conducted
which
included
disulfoton
(
and
rarely
the
disulfoton
degradates
D.
sulfone
and
D.
sulfoxide)
.
Monitoring,
with
no
detections
(
limits
of
detections
ranged
from
0.01
to
6.0
µ
g/
L)
,
has
occurred
in
the
following
states
(
number
of
wells)
:
AL
(
10)
,
CA
(
974)
,
GA
(
76)
,
HI
(
5)
,
IN
(
161)
,
ME
(
71)
,
MS
(
120)
,
MN
(
754)
,
OK
(
1)
,
OR
(
70)
,
and
TX
(
188)
.
The
range
of
detection
limits,
especially
the
high
ones
(
e.
g.
,
6
µ
g/
L)
reduce
the
certainty
of
these
data.
Disulfoton
residues
were
detected
in
ground
water
in
Virginia
and
Wisconsin.
In
Virginia,
6
of
the
12
wells
(
8
monitoring
wells)
sampled
monthly
from
June
1986
through
December
1990
had
disulfoton
detections
ranging
from
0.04
to
2.87
µ
g/
L.
In
Wisconsin,
14
of
26
wells
(
municipal,
community,
and
home
wells)
sampled,
during
May
and
June
1982,
had
disulfoton
residues
ranging
from
4.0
to
100.0
µ
g/
L,
with
a
mean
of
concentration
of
38.4
µ
g/
L.
Although
the
Wisconsin
study
has
received
some
criticism,
particularly
over
QA/
QC
issues,
EFED
believes
that
this
study
needs
to
be
considered
in
the
risk
assessment.
The
Wisconsin
study
was
conducted
in
the
Central
Sand
Plain
of
Wisconsin
which
is
extremely
vulnerable
to
ground­
water
contamination.
Detections
of
other
pesticides
in
this
area
have
often
tended
to
be
orders
of
magnitude
greater
than
those
seen
other
areas.
One
hundred
twenty
wells
were
analyzed
in
MS
for
disulfoton
degradates
sulfone
and
sulfoxide
and
188
wells
were
analyzed
in
TX
for
sulfone.
Limits
of
detection
were
3.80
and
1.90
µ
g/
L
for
the
sulfone
and
sulfoxide
degrade,
respectively,
in
MS.
There
were
no
degradates
reported
in
these
samples.
In
a
more
recent
ground­
water
monitoring
study
conducted
in
North
Carolina,
there
were
no
detections
of
disulfoton,
disulfoton
sulfoxide,
and
disulfoton
sulfone.
Efforts
were
made
in
the
study
to
place
the
wells
in
vulnerable
areas
where
the
pesticide
use
was
known,
so
that
the
pesticide
analyzed
for
would
reflect
the
use
history
around
the
well.
Limitations
of
the
study
include
that
sites
were
sampled
only
twice
and
the
limits
of
detections
were
high
(
e.
g.
,
>
1.0
µ
g/
L)
for
some
of
disulfoton
analytes
(
NCIWG,
1997;
DP
Barcode
267486)
.

Surface­
water
samples
were
also
collected
(
same
Virginia
study
as
noted
above)
in
study
to
evaluate
the
effectiveness
of
Best
Management
Practices
(
BMP)
in
a
Virginia
watershed.
Approximately
half
of
the
watershed
is
in
agriculture
and
the
other
half
is
forested.
Parent
5
disulfoton
was
detected
in
several
surface­
water
samples
with
concentrations
ranging
from
0.037
to
6.11
µ
g/
L.
These
levels
are
within
the
same
order
of
magnitude
of
the
estimated
environmental
concentrations
(
EECs)
obtained
from
the
PRZM/
EXAMS
models
for
parent
disulfoton
which
range
from
0.21
to
1.14
µ
g/
L
for
annual
mean
daily
concentrations
and
7.14
to
26.75
µ
g/
L
for
peak
daily
values.

Disulfoton
residues
have
been
detected
in
surface
water
at
a
low
frequency
in
the
USGS
NAWQA
study.
The
percentage
of
detections
with
disulfoton
concentrations
>
0.01
µ
g/
L
for
all
samples,
agricultural
streams,
urban
streams
were
0.27%
,
0.20,
and
0.61%
,
respectively.
The
corresponding
maximum
concentrations
were
0.060,
0.035,
and
0.037
µ
g/
L.
Disulfoton
has
not
been
detected
in
ground
water
in
the
NAWQA
study.
Although
pesticide
usage
data
is
collected
for
the
different
NAWQA
study
units,
the
studies
are
not
targeted,
specifically
for
disulfoton.

Limitations
for
the
monitoring
studies
include
the
use
of
different
limits
of
detection
between
studies,
lack
of
information
concerning
disulfoton
use
around
sampling
sites,
and
lack
of
data
concerning
the
hydro
geology
of
the
study
sites.

About
50
percent
of
the
well
samples
reported
in
STORET
had
low
levels
(
<
1
µ
g/
L)
of
disulfoton
residues.
However,
there
were
indications
of
some
high
concentrations
(
the
other
50%
were
reported
as
<
250
µ
g/
L)
,
which
may
be
a
reflection
of
how
the
data
were
reported
as
the
disulfoton
concentrations
in
the
monitoring
were
not
always
known.
This
is
because
the
detection
limit
was
extremely
high
or
not
specified,
and/
or
the
limit
of
quantification
was
not
stated
or
extremely
high.
Disulfoton
concentrations
were
simply
given
as
less
than
a
value.
Therefore,
considerable
uncertainty
exists
with
respect
to
the
STORET
monitoring
data.
The
spatial
and
temporal
relationship
between
disulfoton
use,
rainfall/
runoff
events
and
the
location
and
time
of
sampling
frequently
cannot
be
adequately
determined.

Toxicity
Summary
The
available
acute
toxicity
data
on
the
TGAI
indicate
that
disulfoton
is:
highly
to
very
highly
toxic
to
birds
on
an
acute
oral
basis
(
LD50
=
3.2
to
39
mg/
kg)
;
moderately
to
highly
toxic
to
birds
on
a
dietary
basis
(
LC50
=
333
to
622
ppm)
;
very
highly
toxic
to
mammals
on
an
acute
oral
basis
(
LD50
=
1.9
to
15
mg/
kg)
;
moderately
toxic
to
bees
(
LD50
=
4.1
µ
g/
bee)
;
very
highly
toxic
to
moderately
toxic
to
freshwater
fish
(
LC50
=
39
to
7,200
ppb)
;
very
highly
toxic
to
freshwater
invertebrates
(
LC50
=
3.9
to
52
ppb)
;
highly
toxic
to
marine/
estuarine
fish
(
LC50
=
520
ppb)
and
very
highly
toxic
to
marine/
estuarine
invertebrates
(
LC50
or
EC50
=
15
to
900
ppb)
.
Acute
toxicity
for
the
sulfone
degradate
indicate
that
it
is
highly
toxic
to
birds
on
an
acute
oral
basis
(
LD50
=
18
mg/
kg)
,
moderately
toxic
to
birds
on
a
dietary
basis
(
LC50
=
558
to
622
ppm)
,
highly
toxic
to
mammals
on
an
acute
oral
basis
(
LD50
=
11.24
mg/
kg)
,
highly
toxic
to
bees
(
LD50
=
0.96
F
g/
bee)
,
highly
to
moderately
toxic
to
freshwater
fish
(
LC50
=
112
to
>
9,200
ppb)
,
very
highly
toxic
to
freshwater
invertebrates
(
LC50
=
35.2
ppb)
,
and
moderately
toxic
to
marine/
estuarine
fish
(
LC50
=
1,060
ppb)
.
The
sulfoxide
metabolite
is
very
highly
toxic
to
birds
on
an
acute
oral
basis
(
LD50
=
9.2
mg/
kg)
;
moderately
to
highly
toxic
to
birds
on
a
dietary
basis
(
LC50
=
456
to
823
ppm)
;
moderately
toxic
6
to
bees
(
LD50
=
1.11
µ
g/
bee)
;
highly
to
slightly
toxic
to
freshwater
fish
(
LC50
=
188
to
60,300
ppb)
;
very
highly
toxic
to
freshwater
invertebrates
(
LC50
=
64
ppb)
;
and
slightly
toxic
to
marine/
estuarine
fish
(
LC50
=
11,300
ppb)
.

Chronic
toxicity
studies
on
disulfoton
established
the
following
NOAEC
values:
37
ppm
for
birds,
0.8
ppm
for
small
mammals,
220
ppb
for
freshwater
fish
(
4.6
ppb
for
bluegill
sunfish,
using
the
factor
of
chronic
to
acute
values
for
the
rainbow
trout)
,
0.037
ppb
for
freshwater
invertebrates,
16.2
ppb
for
marine/
estuarine
fish
early
life­
stage,
0.96
ppb
for
marine/
estuarine
fish
for
life­
cycle,
and
2.35
ppb
for
marine/
estuarine
invertebrates.
There
are
chronic
invertebrate
studies
on
the
2
major
degradates­
­
sulfone
(
NOAEC
0.14
ppb)
and
sulfoxide
(
NOAEC
1.53
ppb)
.

Risk
Assessment
Summary
Risk
Characterization
A.
Characterization
of
the
Fate
and
Transport
of
Disulfoton
I.
Water
Exposure
(
a)
Surface
Water
Disulfoton
is
likely
to
be
found
in
runoff
water
and
sediment
from
treated
and
cultivated
fields.
However,
the
fate
of
disulfoton
and
its
degradates
once
in
surface
water
and
sediments,
and
the
likely
concentrations
therein,
cannot
be
modeled
with
a
high
degree
of
certainty
since
data
are
not
available
for
the
aerobic
and
anaerobic
aquatic
degradation
rates.
Surface
water
concentrations
of
disulfoton
and
total
disulfoton
residues
were
estimated
by
using
PRZM3
and
EXAMS
models
using
several
different
scenarios
(
barley,
cotton,
potato,
tobacco,
and
spring
wheat)
.
The
large
degree
of
latitude
available
in
the
disulfoton
labels
also
allows
for
a
wide
range
of
possible
application
rates,
total
amounts,
application
methods,
and
intervals
between
applications.
Considering
the
relatively
rapid
rate
of
microbial
degradation
in
the
soil
(
<
20
day
aerobic
soil
metabolism
half­
life)
and
direct
aquatic
photolysis,
disulfoton
parent
may
degrade
fairly
rapidly
in
surface
water.
However,
peak
concentrations
of
disulfoton
in
the
farm
pond
appear
capable
of
being
quite
high,
with
1­
year­
in
10
peak
surface
water
concentrations
of
7.14
to
26.75
F
g/
L
and
90­
day
concentrations
of
1.73
to
6.87
µ
g/
L
for
the
parent
compound.
The
mean
EECs
of
the
annual
means
of
disulfoton
ranged
from
0.21
to
1.14
µ
g/
L.
Although
there
is
a
lack
of
some
environmental
fate
data
for
the
degradates,
the
assessment
suggests
that
the
degradates
will
reach
higher
concentrations
than
the
parent
because
they
are
more
persistent
and
probably
more
mobile.
The
estimated
peak
concentrations
for
the
total
disulfoton
residues
in
the
farm
pond
ranged
from
15.43
to
58.48
µ
g/
L,
90
day
average
ranged
from
12.20
to
35.30
µ
g/
L,
and
the
mean
of
the
annual
means
ranged
from
3.89
to
9.32
µ
g/
L.
Water
samples
collected
at
the
site
of
a
fish
kill
in
Colorado
contained
D.
sulfoxide
at
levels
of
29.5­
48.7
µ
g/
L,
and
D.
sulfone
at
0.0199­
0.214
µ
g/
L.
The
aerobic
soil
metabolism
studies
show
that
the
maximum
sulfoxide
residues
are
about
58
percent
of
total
radioactive
material,
thus,
the
sulfoxide
concentrations
suggest
that
parent
7
disulfoton
concentrations
could
range
from
50.8
to
83.9
µ
g/
L.
The
ratio
of
the
disulfoton
sulfoxide
concentration
to
the
average
maximum
disulfoton
concentration
was
higher
(
74%
)
in
the
microcosm
study
(
MRID
#
4356501)
than
in
the
soil
residues
(
58%
)
.

The
estimated
drinking
water
concentrations
(
EDWC)
for
parent
disulfoton
and
total
disulfoton
residues
were
also
determined
using
the
IR
and
PCA
concepts.
The
peak
concentrations
of
disulfoton
in
IR
appear
capable
of
being
quite
high,
with
1­
year­
in
10
peak
surface
water
concentrations
of
7.13
to
44.20
F
g/
L
and
annual
mean
concentrations
of
0.43
to
2.77
µ
g/
L
for
the
parent
compound.
The
mean
EECs
of
the
annual
means
of
disulfoton
ranged
from
0.23
to
1.31
µ
g/
L.
Although
there
is
a
lack
of
some
environmental
fate
data
for
the
degradates,
the
assessment
suggests
that
the
degradates
will
reach
higher
concentrations
than
the
parent
because
they
are
more
persistent
and
probably
more
mobile.
The
estimated
1­
in­
10
year
peak
concentrations
for
the
total
disulfoton
residues
in
the
IR
ranged
from
20.83
to
104.92
µ
g/
L
and
annual
mean
ranged
from
5.10
to
16.25
µ
g/
L,
and
the
mean
of
the
annual
means
ranged
from
2.55
to
10.42
µ
g/
L.
These
values
will
be
highly
effected
by
the
value
selected
for
PCA.
The
PCA
values
have
been
estimated
by
OPP
for
spring
wheat
(
0.56)
and
cotton
(
0.20)
.
The
default
for
value
for
all
agricultural
land
of
0.87
was
used
for
the
barley,
potatoes,
and
tobacco
scenarios.
Better
estimates
of
the
PCA
for
these
crops
would
reduce
the
uncertainty
associated
with
the
estimated
drinking
water
concentrations.

Surface­
water
samples
were
collected
in
a
study
to
evaluate
the
effectiveness
of
Best
Management
Practices
(
BMP)
in
a
Virginia
watershed.
Approximately
half
of
the
watershed
is
in
agriculture
and
the
other
half
is
forested.
The
detections
of
parent
disulfoton
in
surface­
water
samples
ranged
from
0.037
to
6.11
µ
g/
L
and
fell
within
an
order
of
magnitude
with
the
estimated
environmental
concentrations
(
EECs)
obtained
from
the
PRZM/
EXAMS
models.

Surface­
water
monitoring
by
the
USGS
in
the
NAWQA
(
USGS,
1998)
project
found
relatively
few
detections
of
disulfoton
in
surface
water
with
a
maximum
concentration
of
0.060
µ
g/
L.
As
noted
above
disulfoton
degradates
were
reported
in
surface
water,
when
a
rainfall
event
occurred
following
application
to
wheat,
where
fish
kills
occurred;
pesticide
residue
concentrations
ranged
from
29.5
to
48.7
µ
g/
L
for
D.
sulfoxide
and
0.02
to
0.214
µ
g/
L
(
Incident
Report
No.
I001167­
001)
.

A
search
of
the
EPA
 
s
STORET
(
10/
16/
97)
data
base
resulted
in
the
identification
of
disulfoton
residues
at
a
number
of
locations.
Often
the
values
ranged
from
0.01
to
100.0
F
g/
L
with
most
of
the
values
reported
as
 
actual
value
is
less
than
this
value.
 
Thus,
,
when
a
value
of
100.00
µ
g/
L
is
reported,
it
is
not
known
how
much
less
than
100.0
F
g/
A
the
actual
value
is
known
to
be
less.
Thus
there
is
considerable
uncertainty
surrounding
some
of
the
data
in
STORET.

(
b)
Ground
Water
The
SCI­
GROW
(
Screening
Concentration
in
Ground
Water)
screening
model
developed
in
EFED
was
used
to
estimate
disulfoton
concentrations
in
ground
water
(
Barrett,
1997)
.
SCI
­
GROW
represents
a
"
vulnerable
site"
,
but
not
necessarily
the
most
vulnerable
conditions,
treated
8
(
here)
with
the
maximum
rate
and
number
of
disulfoton
applications,
while
assuming
conservative
environmental
properties
(
90
percent
upper
confidence
bound
on
the
mean
aerobic
soil
half­
life
of
6.12
days
and
an
average
Koc
value
of
551
mL/
g)
.
The
maximum
disulfoton
concentration
predicted
in
ground
water
by
the
SCI­
GROW
model
(
using
the
maximum
rate
4
lb.
a.
i.
/
ac
and
2
applications
­
potatoes)
was
0.05
µ
g/
L.
The
maximum
total
disulfoton
residue
concentration
predicted
in
ground
water
by
the
SCI­
GROW
model
for
the
same
scenario
is
3.19
µ
g/
L
(
except
90
percent
upper
bound
on
mean
half­
life
of
total
residues
is
259.6
days)
.

Ground
water
monitoring
data
generally
confirms
fairly
rapid
degradation
and
low
mobility,
because
of
the
relatively
low
levels
and
frequency
of
detections
of
parent
disulfoton
in
ground
water.
There
were
no
ground­
water
detections
of
parent
disulfoton
in
the
USGS
NAWQA
(
USGS,
1998)
with
a
limit
of
detections
of
0.01
or
0.05
µ
g/
L,
depending
upon
method.
.
Most
of
the
studies
recorded
in
the
PGWDB
(
USEPA,
1992)
also
reported
no
disulfoton
detections.
Disulfoton
residues
ranging
from
0.04
to
100.00
µ
g/
L
were
reported
for
studies
conducted
in
Virginia
(
0.04
to
2.87
µ
g/
L)
and
Wisconsin
(
4.00
to
100.00
µ
g/
L)
.
Of
specific
interest
are
areas
where
the
concentrations
of
parent
disulfoton
reported
in
the
studies
(
VA
and
WI)
exceeded
the
estimate
of
0.05
µ
g/
L
obtained
from
EFED'
s
SCI­
GROW
(
ground­
water
screening
model)
model.
It
should
be
noted
that
the
Wisconsin
data
received
some
criticism
which
influences
the
certainty
of
these
detections,
no
such
criticisms
or
limitations
exist
for
the
Virginia
study.

The
major
issues,
concerning
the
Wisconsin
study
(
Central
Sands)
were
that
the
study
may
not
have
followed
QA/
QC
on
sampling
and
the
failure
of
follow­
up
sampling
to
detect
disulfoton
residues
in
ground
water
as
suggested
by
Holden
(
1986)
,
have
been
considered
by
EFED
in
the
ground­
water
quality
assessment.
The
Central
Sands
of
Wisconsin
are
known
to
be
highly
vulnerable
to
ground­
water
contamination.
There
are
regions
within
the
United
States
that
have
conditions
that
are
highly
vulnerable
to
ground
water
contamination
and
regularly
have
pesticides
detected
in
ground
water
which
far
exceeds
values
seen
elsewhere.
Several
of
these
areas
are
well
documented,
e.
g.
,
Long
Island,
Suffolk
County,
NY
and
Central
Sands
in
WI.
Although,
some
questions
have
been
levied
against
the
disulfoton
detections
in
Wisconsin,
the
occurrence
of
disulfoton
at
the
levels
reported
cannot
be
ruled
out.

There
were
no
detections
of
disulfoton,
disulfoton
sulfoxide,
and
disulfoton
in
the
ground­
water
monitoring
study
conducted
in
North
Carolina.
Efforts
were
made
to
place
the
wells
in
vulnerable
areas
where
the
pesticide
use
was
known,
so
that
the
pesticide
analyzed
for
would
reflect
the
use
history
around
the
well.
Seven
Christmas
tree,
one
wheat,
and
two
tobacco
growing
areas
were
sampled
for
disulfoton.
Limitations
of
the
study
include
that
sites
were
sampled
only
twice
and
the
limits
of
detections
were
high
(
e.
g.
,
>
1.0
µ
g/
L)
for
some
of
disulfoton
analytes.
Uncertainties
associated
with
the
study
include
whether
two
samples
from
eight
wells
are
adequate
to
represent
the
ground­
water
concentrations
of
disulfoton
residues,
did
DRASTIC
correctly
identify
a
site'
s
vulnerability,
and
were
the
wells
placed
down­
gradient
of
the
use
areas.

The
SCI­
GROW
model
represents
a
"
vulnerable
site"
,
but
not
necessarily
the
most
vulnerable.

9
Several
things
should
be
considered.
First,
the
Virginia
and
Wisconsin
monitoring
studies
were
probably
conducted
in
areas
vulnerable
to
ground­
water
contamination.
The
level
of
certainty
with
respect
to
vulnerability
is
probably
greater
for
Wisconsin
(
relatively
less
uncertainty)
than
for
Virginia
(
relatively
more
uncertainty
)
.
The
occurrence
of
preferential
flow
and
transport
processes
has
been
also
noted
in
Wisconsin
(
and
is
also
possible
in
Virginia)
and
may
(
speculation)
have
contributed
to
the
"
high"
concentrations
(
especially
in
WI)
when
the
initial
sampling
occurred,
but
not
necessarily
in
the
follow­
up
sampling)
.
The
knowledge
concerning
the
disulfoton
use
in
areas
in
association
with
the
wells
is
not
well
known
(
high
uncertainty)
.
Some
notable
limitations
of
modeling
and
monitoring
are
presented
elsewhere
in
this
document
(
c)
Drinking
Water
The
Agency
recommends
that
the
1­
out­
of­
10­
year
peak
values
be
used
the
acute
surface
drinking
water
level
for
parent
disulfoton,
and
for
chronic
levels
use
either
the
90­
day
and
annual
average.
The
maximum
values
are:
44.20,
2.77,
and
1.31
µ
g/
L
or
the
peak,
90­
day
mean,
and
long
term
mean,
respectively.
For
the
total
disulfoton
residues
the
peak,
90­
day
mean,
and
long
term
mean
are
104.92,
53.47,
and
10.42
µ
g/
L.
The
EDWCs
for
both
parent
disulfoton
and
TDR
exceed
the
DWLOC
values
estimated
by
the
Agency.
The
EDWCs
values
for
the
parent
disulfoton
have
less
uncertainty
than
the
total
residue,
because
there
is
more
certainty
surrounding
the
"
estimated"
aerobic
aquatic
metabolism
half­
life
for
the
estimated
aerobic
aquatic
half­
life
for
the
total
disulfoton
residues.
It
is
recommended
that
the
Virginia
data
be
considered
in
the
"
quantitative"
drinking
water
assessment
for
ground
water
exposure.
The
Wisconsin
data
should
be
noted
and
addressed
more
qualitatively.
Highly
vulnerable
areas,
such
as
the
Central
Sand
Plain,
do
not
represent
the
entire
use
area
and
can
probably
be
better
mitigated
or
managed
a
local
or
state
level.
Specifically,
it
is
recommended
that
the
2.87
µ
g/
L
be
used
for
acute
and
chronic
exposure
from
ground
water.
Based
upon
the
fate
properties
of
disulfoton,
the
sulfoxide
and
sulfone
degradates
(
more
persistent
and
probably
more
mobile)
have
a
greater
probability
of
being
found
in
ground
water.
It
is
likely
that
a
ground
water
study
(
ies)
may
be
required
to
better
assess
the
potential
exposure
from
the
degradates
(
and
also
parent)
.

B.
Characterization
of
risk
to
nontarget
species
from
Disulfoton
Birds:
Acute
risk
to
birds
is
predicted
especially
for
use
patterns
involving
the
15
G
formulation.
All
modeled
application
rates
and
methods
for
the
15
G
formulation
exceed
the
acute
risk
level
of
concern
for
birds,
regardless
of
size.
Robins
were
reported
to
have
been
killed
following
the
application
of
a
disulfoton
granular
product
to
a
tree
nursery.
Carcasses
were
found
during
terrestrial
field
testing
of
disulfoton
on
potatoes,
confirming
the
presumption
of
acute
risk
to
birds.
Since
disulfoton
is
a
systemic
pesticide,
the
granular
formulations
can
result
in
exposure
through
food
items
due
to
uptake
by
the
plant
tissues
in
addition
to
direct
exposure
to
any
unincorporated
granules.

Foliar
applications
of
liquid
formulations
present
the
greatest
risk
to
herbivorous
birds.
Based
on
10
the
results
of
field
studies,
the
residue
levels
on
sampled
invertebrates
are
well
below
those
predicted
by
EFED'
s
models,
consequently
insectivores
did
not
appear
to
be
at
risk.
However,
there
is
field
evidence
suggesting
that
some
species
are
extremely
sensitive
to
disulfoton
such
that
even
low
concentrations
caused
mortality.
The
Swainson
 
s
hawk
kill
appears
to
be
the
result
of
consuming
grasshoppers.
The
hawks
crop
contents
were
analyzed
and
contained
residues
around
8
ppm.
Finally,
live
blue
jays
collected
6
to
7
hrs
after
a
pecan
orchard
was
sprayed
at
0.72
lbs
ai/
A
had
brain
cholinesterase
inhibition
from
32
to
72%
(
White
et
al.
1990)
.
Although
it
is
unknown
whether
these
birds
would
eventually
die,
Ludke
et
al.
1975
suggest
that
inhibition
>
50%
in
carcasses
is
evidence
that
death
was
caused
by
some
chemical
agent.
Furthermore,
it
should
be
recognized
that
these
birds
were
not
only
feeding
on
contaminated
food,
but
also
were
impacted
by
dermal
and
inhalation
exposure.

Ground
applications
of
liquid
formulations
to
soil,
even
at
4.0
lb
ai/
A
would
not
be
expected
to
cause
mortality
to
birds.
Field
studies
have
demonstrated
that
residue
concentration
within
food
items
­
­
vegetation,
invertebrates
and
seeds
­
­
in
or
on
the
edge
of
fields
are
well
below
those
used
in
screening
level
assessments
and
empirically
derived
from
aerial
applications.
However,
in
light
of
the
points
made
in
the
previous
paragraph,
some
mortality
is
possible
given
the
possible
multiple
routes
of
exposure
and
hypersensitivity
of
some
species.

Chronic
risk
to
herbivorous
birds
are
predicted
from
exposure
to
disulfoton
when
assuming
birds
are
exposed
to
peak
residues
for
a
short
period
of
time
or
average
Fletcher
maximum
residues
for
longer
periods.
Based
on
reduced
hatchling
weight,
the
NOAEC
is
37;
both
for
bobwhite
quail
and
mallard
duck.
Foliar
applications
and
aerially
applied
soil
sprays
are
estimated
to
result
in
30
day
average
residues
(
based
on
maximum
Fletcher
values)
on
vegetation
exceeding
the
avian
chronic
level
of
concern
for
application
rates
equal
or
greater
than
a
single
application
of
1
lb
ai/
A.
A
residue
monitoring
study
for
Di­
syston
8E
in
potatoes
showed
the
peak
residues
on
vegetation
was
105
ppm
after
the
initial
application
and
152
ppm
following
a
second
application
6
to
10
days
later.
In
the
same
study,
the
means
of
the
3
applications
for
vegetation
in
and
adjacent
to
fields
were
41
and
14
ppm
respectively.
The
upper
bound
95%
mean
for
the
vegetation
adjacent
to
the
fields
was
71
ppm.
Therefore
even
empirically
derived
residues
suggest
that
the
chronic
LOC
is
exceeded
on
foliage,
but
not
invertebrates
for
a
short
time
following
aerial
applications.
It
is
anticipated
that
since
the
sulfone
and
sulfoxide
degradates
of
disulfoton
were
similar
in
acute
toxicity
to
parent
disulfoton
they
would
have
similar
chronic
NOAECs.
These
degradates
extend
the
time
that
total
disulfoton
residues
are
available
for
consumption.
Since
many
of
the
applications
of
disulfoton
occur
in
the
spring,
overlapping
the
breeding
season
for
most
bird
species,
there
is
the
potential
for
significant
reproductive
impacts.

Mammals:
Acute
risk
to
mammals
is
expected
for
use
patterns
involving
the
15
G
formulation.
All
modeled
application
rates
and
methods
exceed
the
acute
risk
level
of
concern
for
mammals,
regardless
of
the
mammals
 
size.
.
Small
mammal
carcasses
were
found
during
terrestrial
field
testing
of
disulfoton
on
potatoes,
confirming
the
presumption
of
acute
risk
to
mammals.
Since
disulfoton
is
a
systemic
pesticide,
the
granular
formulations
can
result
in
exposure
through
food
items
due
to
uptake
by
the
plant
tissues
in
addition
to
direct
exposure
to
any
unincorporated
granules.

11
Applications
of
the
liquid
formulations
especially
by
air
can
result
in
mammals
being
exposed
to
multiple
routes
of
exposure
­
­
dermal,
inhalation,
drinking
contaminated
water
as
well
as
ingestion
of
contaminated
food
items.
The
persistent
sulfone
and
sulfoxide
degradates
are
also
toxic
to
mammals,
thereby
increasing
the
potential
risk
from
the
application
of
disulfoton.
The
registrant
has
suggested
that
mammals
as
well
as
birds
can
consume
an
equivalent
of
2
to
3
LD50'
s
as
part
of
their
diet
and
not
be
adversely
effected.
Although
this
may
be
true
for
a
population
of
laboratory
test
animals,
individuals
will
vary
in
their
sensitivity
and
can
die
as
a
result
of
inability
to
avoid
predation,
secure
prey
or
thermoregulate.
Numerous
pen
studies
were
conducted
with
cottontail
and
jack
rabbits
exposed
to
single
applications
ranging
from
1
to
25
lbs
ai/
A.
While
no
mortality
occurred
to
cottontails,
at
the
2
lb
ai/
A
rate
and
above
jackrabbits
suffered
100%
mortality.
Secondary
poisoning
did
not
occur
when
the
jackrabbit
carcasses
were
fed
to
a
number
of
avian
and
mammalian
carnivores.
The
apparent
difference
between
the
pen
study
results
and
the
acute
mortality
predicted
in
the
risk
assessment
screen
is
largely
due
to
the
possibility
that
the
calculated
1
day
LC50s
(
ranging
from
2
to
12.7
ppm)
discounts
the
rapid
metabolism
of
disulfoton.
However,
using
the
demeton
LC50
of
320
ppm
with
its
wide
ranging
confidence
interval
(
0
to
infinity)
also
adds
uncertainty
to
the
question
of
disulfoton
 
s
acute
risk
to
mammals.

Chronic
risk
to
mammals
is
predicted.
As
was
previously
discussed
in
the
above
acute
and
chronic
sections
for
birds,
there
are
several
reasons
why
small
mammals
are
likely
to
be
at
even
greater
risk,
not
the
least
of
which
is
the
extremely
low
NOAEC
of
0.8
ppm.
All
modeled
and
empirically
derived
residues
for
all
sites
exceed
the
chronic
risk
level
of
concern
for
mammals.
Finally,
the
persistence
of
the
sulfone
and
sulfoxide
degradates,
which
are
also
toxic
to
mammals,
increases
the
likelihood
of
chronic
risk
to
mammals.

Non­
target
Insects:
Disulfoton
and
its
sulfoxide
and
sulfone
degradates
are
moderately
to
highly
toxic
to
bees,
however
a
residual
study
with
honey
bees
indicated
no
toxicity
for
applications
up
to
1
lb
ai/
A.

Freshwater
Fish:
Most
of
the
modeled
use
patterns
did
not
exceed
the
acute
risk
levels
of
concern
for
freshwater
fish.
Only
the
two
soil
applications
at
4.0
lb
ai
\
A
of
the
liquid
formulation
exceeded
acute
risk.
All
other
scenarios
exceeded
the
restricted
use
and
endangered
species
levels
of
concern.
There
is,
however,
a
large
amount
of
variation
in
freshwater
fish
species
 
sensitivity
to
disulfoton,
,
as
evidenced
in
the
toxicity
data
table.
The
microcosm
study
included
bluegill
sunfish.
Following
the
last
application
of
30
ppb,
10%
of
the
fish
died.
Several
kills
of
freshwater
fish
have
occurred
from
applications
of
disulfoton
to
different
crops­
­
both
as
registered
uses
as
well
as
from
misuse.

Chronic
risk
to
freshwater
fish
may
occur
from
uses
where
single
application
rates
are
equal
to
4
lb
ai/
a
and
from
3
applications
of
1
lb
ai/
A.
.
The
single
freshwater
fish
species
(
rainbow
trout)
,
for
which
chronic
toxicity
data
was
available,
demonstrates
significantly
less
sensitivity
to
disulfoton
than
several
other
species
(
bluegill
sunfish,
bass,
guppy)
.
Therefore,
an
estimated
chronic
NOEC
value
was
calculated
using
the
chronic
to
acute
ratio
for
the
rainbow
trout,
as
described
earlier.
Based
on
the
estimated
chronic
NOAEC
for
bluegill,
chronic
effects
would
12
occur
from
the
present
uses
on
tobacco,
foliar
treatments
of
potatoes
and
repeated
soil
treatments
of
cotton.
Christmas
tree
plantations
were
not
modeled,
however
the
high
application
rate
(
possibly
47
lbs
ai/
A)
and
sloped
land
may
be
a
potentially
risky
site.

Freshwater
Invertebrates:
All
modeled
crop
scenarios
exceeded
the
acute
risk
level
of
concern,
but
the
highest
risk
quotients
were
less
than
10.
Again,
the
risk
is
further
increased
due
to
the
toxicity
and
persistence
of
the
degradates
of
disulfoton.
Microcosm
study
results
indicated
that
there
was
recovery
of
most
phyla
examined
at
3
ppb
and
long
term
impacts
for
most
phyla
at
30
ppb.
Therefore
10
ppb
is
probably
a
concentration
where
short
term
effects
will
occur,
but
recovery
can
be
anticipated.

Chronic
risk
to
freshwater
invertebrates
is
predicted
to
from
the
use
of
disulfoton.
All
of
the
modeled
crop
scenarios
greatly
exceeded
the
level
of
concern,
sometimes
by
a
factor
of
several
hundred.
Invertebrate
life­
cycle
testing
with
disulfoton
shows
that
it
impacts
reproductive
parameters
(
number
of
young
produced
by
adults)
in
addition
to
survival
and
growth.
The
21
day
average
EECs
for
the
modeled
sites
ranged
from
4.3
to
17.9
ppb.
For
the
most
part
these
EECs
are
within
the
range
where
recovery
was
occurring
in
the
microcosm.
However
there
is
uncertainty
as
to
how
much
more
reliable
the
microcosm
may
be
as
a
predictor
of
safety.

Estuarine
and
Marine
Fish:
Although
acute
and
restricted
risk
levels
of
concern
were
not
exceeded
for
estuarine
and
marine
fish,
the
endangered
species
level
of
concern
was
exceeded
for
several
of
the
modeled
crop
scenarios
(
cotton,
potatoes
and
wheat)
.
As
was
note
among
the
freshwater
fish,
there
can
be
substantial
species
differences
in
sensitivity
to
disulfoton.
Therefore,
it
is
possible
that
the
single
marine/
estuarine
fish
species
tested
(
Sheepshead
minnow)
does
not
fully
represent
the
true
range
of
sensitivity
found
in
a
marine
or
estuarine
ecosystem,
and
this
assessment
may
therefore
underestimate
the
true
risk
to
marine/
estuarine
fish.
There
is
also
some
uncertainty
in
using
the
PRZM/
EXAMS
EECs
derived
for
ponds
to
predict
exposure
to
marine/
estuarine
organisms.
The
scenarios
modeled
are
based
on
hydrologic
data
for
freshwater
habitats.
The
exposure
in
a
marine
or
estuarine
habitat
may
be
higher
or
lower
than
that
predicted
for
a
freshwater
habitat,
resulting
in
higher
or
lower
risk
to
marine/
estuarine
organisms.

Chronic
risk
to
estuarine
and
marine
fish
is
predicted
from
the
use
of
disulfoton.
Both
early
life­
stage
and
full
life­
cycle
testing
demonstrated
a
variety
of
effects
at
low
levels
of
disulfoton.
Risk
quotients
based
on
the
early
life­
stage
toxicity
endpoint
exceeded
the
level
of
concern
for
cotton,
potatoes
and
tobacco.
The
highest
risk
quotients
were
based
on
numerous
life­
cycle
toxicity
endpoints
­
­
fecundity,
hatching
success
and
growth;
consequently
the
chronic
level
of
concern
was
exceeded
for
all
modeled
scenarios.
Estuarine
fish
spawning
in
the
upper
reaches
of
tributaries
of
bays
would
be
a
greatest
risk.
However
the
likelihood
of
this
risk
is
uncertain
for
several
reasons:
1)
the
required
time
the
adults
must
be
exposed
to
disulfoton
in
order
for
their
reproductive
systems
to
be
effected
and
2)
the
residency
time
of
disulfoton
residues
in
tidal
or
flowing
water.
Even
if
adults
are
effected
after
an
exposure
of
only
a
week,
disulfoton
may
be
moved
out
of
an
area
within
several
days.

Estuarine
and
Marine
Invertebrates:
Three
of
the
five
modeled
scenarios
(
cotton,
potatoes,
and
tobacco)
resulted
in
exceedences
of
the
estuarine/
marine
invertebrate
acute
risk
level
of
concern.
All
the
remaining
uses
exceeded
the
restricted
use
level
of
concern.
Similar
uncertainty
13
exists
as
to
the
validity
of
the
exposure
scenario
for
invertebrates
as
was
just
described
for
estuarine
fish.

Chronic
risk
to
marine/
estuarine
invertebrates
is
predicted.
All
of
the
modeled
crop
scenarios
exceeded
the
chronic
level
of
concern.
The
much
shorter
life
cycle
of
invertebrates
as
compared
to
fish,
increases
the
likelihood
that
only
a
brief
exposure
(
a
few
day
or
even
hours)
of
adults
to
disulfoton
concentrations
around
the
NOAEC
is
sufficient
to
negatively
impact
reproduction.
The
degree
to
which
the
freshwater
microcosm
is
a
predictor
of
safety
for
the
estuarine
invertebrates
in
highly
uncertain.
Only
the
mysid
shrimp
has
been
tested
and
it
was
acutely
and
chronically
less
sensitive
than
freshwater
Daphnia.
Therefore,
on
the
basis
of
this
limited
data,
the
chronic
impact
to
estuarine
invertebrates
not
only
appears
to
be
lower
than
for
freshwater
invertebrates,
but
is
likely
to
be
low.

Nontarget
Plants:
Currently,
terrestrial
and
aquatic
plant
testing
is
not
required
for
pesticides
other
than
herbicides
except
on
a
case­
by­
case
basis.
Nontarget
plant
testing
was
not
required
for
disulfoton,
so
the
risk
to
plants
could
not
be
assessed
at
this
time.
There
are
phytotoxicity
statements
on
the
label,
however,
as
well
as
some
incident
reports
of
possible
plant
damage
from
the
use
of
disulfoton,
so
there
is
the
potential
for
risk
to
nontarget
plants.

Summary
of
Risk
Assessment
of
North
Carolina
24c
for
use
in
Christmas
Tree
Farms
Christmas
tree
farms
and
the
adjacent
areas
­
­
forests
and/
or
pasture
 
provide
excellent
habitat
for
a
great
variety
of
wild
life.
The
use
of
granular
disulfoton
suggests
that
there
is
acute
risk
to
small
birds
and
mammals.
The
North
Carolina
Christmas
Tree
community
has
submitted
numerous
testimonials
emphasizing
the
ever
increasing
numbers
and
diversity
of
wild
life
.
This
includes
game
animals
such
as
turkey
rearing
young
amidst
the
Christmas
trees,
song
birds,
rodents
and
foxes.
Although
this
information
is
intended
to
suggest
there
is
little
or
no
negative
impact
from
not
only
disulfoton,
but
other
pesticides
or
cultural
practices
as
well,
the
Agency
would
prefer
to
receive
documented
surveys
or
research
before
making
a
final
determination.

There
were
no
detections
of
disulfoton
or
its
metabolites
in
the
ground­
water
monitoring
study
conducted
in
North
Carolina
by
the
North
Carolina
Departments
of
Agriculture
and
Environment,
Health,
and
Natural
Resources.
Seven
Christmas
tree,
one
wheat,
and
two
tobacco
growing
areas
were
sampled
for
disulfoton
residues.
Limitations
of
the
study
include
that
sites
were
sampled
only
twice
and
the
limits
of
detections
were
high
(
e.
g.
,
>
1.0
µ
g/
L)
for
some
of
disulfoton
analytes.
Uncertainties
associated
with
the
study
include
whether
two
samples
from
eight
wells
are
adequate
to
represent
the
ground­
water
concentrations
of
disulfoton
residues,
did
DRASTIC
correctly
identify
a
site'
s
vulnerability,
and
were
the
wells
placed
down­
gradient
of
the
use
areas.

The
use
of
Disulfoton
15
G
in
Christmas
tree
farms
at
this
time
cannot
be
modeled
for
potential
surface
water
contamination.
EFED
assumes
the
estimated
concentration
for
the
North
Carolina
24
(
c)
use
pattern
­
­
2.75
lbs
ai/
A
unincorporated
­
­
may
be
similar
to
the
values
for
the
single
4.0
lb
ai/
A
incorporated
application
of
granular
disulfoton
to
tobacco.
Based
on
this
assumption
there
is
acute
risk
to
aquatic
invertebrates
and
chronic
risk
to
freshwater
fish
and
aquatic
invertebrates.

14
The
North
Carolina
Christmas
tree
industry
submitted
two
surveys
of
streams
in
the
Westerns
region.
The
surveys
followed
a
protocol
for
looking
at
macro
invertebrates
to
assess
the
impact
of
agricultural
practices
associated
with
Christmas
tree
farming.
In
summary,
the
two
surveys
suggests
that
when
conservation
measures
associated
with
Christmas
tree
farming
in
the
Western
counties
of
North
Carolina
are
implemented,
there
may
be
only
slight,
short
term
impact
to
aquatic
macro
invertebrates
from
disulfoton
use.
Aquatic
macro
invertebrates
appear
to
have
the
capacity
to
recover
from
any
impact
that
could
be
caused
by
disulfoton
use
on
Christmas
trees
in
Western
North
Carolina.

C.
Mitigation
The
use
of
disulfoton
at
single
application
rates
of
1.0
lb
ai/
A
and
greater,
and
multiple
application
rates
of
0.5
lb
ai/
A
and
greater,
poses
an
acute
risk
to
birds,
mammals,
fish,
and
aquatic
invertebrates,
as
well
as
to
nontarget
insects.
EFED
believes
that
amending
label
rates
to
the
lowest
efficacious
rate
as
a
maximum,
as
well
as
restricting
the
number
of
applications
per
year
and
lengthening
the
application
interval,
would
reduce
acute
risk
to
terrestrial
and
aquatic
organisms.
Requiring
in­
furrow
applications
wherever
feasible,
and
eliminating
banded
applications
of
granular
disulfoton
with
narrow
row
spacing,
would
also
reduce
the
risk
to
nontarget
organisms,
especially
birds
and
mammals.
Eliminating
aerial
applications
of
disulfoton
and
imposing
buffer
strips
around
aquatic
habitats
would
reduce
the
risk
to
aquatic
organisms.
Risk
to
bees
and
other
nontarget
insects
could
be
lowered
by
not
applying
disulfoton
when
the
insects
are
likely
to
be
visiting
the
area.

Qualitative
comparative
ecological
risk
assessment
between
present
and
proposed
disulfoton
uses.

Bayer
has
proposed
the
following
changes
to
some
use
patterns
assessed
by
the
Agency
that
would
reduce
the
ecological
risk
from
Di­
syston
8E:

*
cancel
aerial
applications
to
cotton
and
wheat.
*
cancel
foliar
applications
to
cotton.

The
table
reflects
additional
changes
proposed
by
Bayer.

15
Table
1
Comparison
of
present
and
proposed
changes
in
4
use
patterns
of
Di­
syston
8E
Present
Use
Proposed
Use
Rate
/
Number
of
Applications
/
Interval
/
Incorp.
Depth/
method
1
Rate/
Number
of
Applications
/
Interval/
Incorp.
Depth/
method
1
lb.
ai/
A
/
#
app.
/
days
/
inches
lb.
ai/
A
/
#
app.
/
days
/
inches
cotton
1.0/
3/
21/
0/
gs
cotton
1.0/
1/
­
/
0/
gs
potatoes
4.0/
2/
14/
2.5/
gs
potatoes
3.0/
1/
­
/
2.5/
gs
potatoes
1.0/
3/
14/
0/
af
potatoes
0.5/
3/
14­
/
0/
af
wheat
0.75/
2/
30/
0/
gs
wheat
0.75/
1/
­
/
0/
gs
1
Method
of
application:
f
=
foliar
and
s
=
soil;
gs
=
ground
spray,
af
=
aerial
spray­
foliar
Risk
to
Birds
and
Mammals
Canceling
aerial
application
to
wheat
and
cotton
reduces
significantly
the
potential
for
exposing
edge
of
field
food
items
and
vegetation.
Canceling
foliar
applications
to
cotton
reduces
the
opportunity
for
exposure,
by
reducing
the
food
items
that
are
directly
sprayed.
As
the
discussion
below
explains,
field
monitoring
indicates
that
ground
spray
to
soil
reduces
substantially
the
residues
on
food
items
from
those
residues
predicted
from
the
nomograph.

Potato
aerial
foliar
at
0.5
lb
ai/
acre
Biological
field
testing
(
MRID
41359101)
suggests
that
significant
acute
risk
to
mammals
from
foliar
sprays
is
unlikely
at
a
single
application
of
1
lb
ai/
acre
or
lower.
Reducing
the
potato
rate
from
1
lb
ai/
acre
3
times,
to
0.5
lb
ai/
acre
3
times,
substantially
lowers
the
acute
risk
to
mammals.

Wheat,
potato
and
cotton
ground
spray
to
soil
Field
residue
monitoring
(
MRID
41118901)
indicates
that
residues
on
food
items
following
ground
applications
to
soil
are
significantly
lower
than
would
be
expected
from
direct
application
to
vegetation.
Peak
residues
following
the
first
of
two
treatments
at
3
lb
ai/
acre
(
in
furrow)
ranged
from
0.9
ppm
(
invertebrates
and
edge
of
field
vegetation)
,
to
26
ppm
(
potato
foliage)
.
The
second
treatment
at
3
lb
ai/
acre
side
dressing
(
6­
7
weeks
later)
resulted
in
peak
residues
of
1.8
(
invertebrates)
,
44
ppm
potato
foliage,
and
54
ppm
(
edge
of
field
vegetation)
.
The
residues
from
these
applications
are
not
only
lower
than
those
estimated
using
the
nomograph,
but
also
lower
than
the
field
residues
resulting
from
foliar
applications.
In
the
foliar
residue
monitoring
study
(
3
aerial
applications
at
1.0
lb
ai/
acre)
the
peaks
were:
invertebrates
(
16
ppm)
and
vegetation
(
154
ppm)
.
The
proposed
changes
would
greatly
reduce
exposure
terrestrial
species.

16
Table
2
Comparison
of
potential
acute
and
chronic
risk
resulting
from
proposed
changes
in
4
use
patterns
of
Di
­
syston
8E
for
birds
and
mammals
Present
Use
Birds
Mammals
Proposed
Use
Birds
Mammals
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
lb.
ai/
A
/
#
app.
/
days
/
inches
lb.
ai/
A
/
#
app.
/
days
/
inches
cotton
1.0/
3/
14/
0/
gs
E
Y
R
Y
cotton
1.0/
1/
­
/
0/
gs
no
Y
E
Y
potatoes
4.0
/
2/
14/
2.5/
gs
R
Y
A
Y
potatoes
3.0/
1/
­
/
2.5/
gs
E
Y
R
Y
potatoes
1.0/
3/
14/
0/
af
R
Y
A
Y
potatoes
0.5/
3/
14­
/
0/
af
R
Y
R
Y
wheat
0.75/
2/
30/
0/
gs
E
Y
R
Y
wheat
0.75/
1/
­
/
0/
gs
no
Y
E
Y
1
Method
of
application:
f
=
foliar
and
s
=
soil;
g
=
ground
and
a
=
aerial
Acute
=
ac;
Chronic
=
ch
Acute
risk
LOC
is
exceeded=
A;
Restricted
use
LOC
is
exceeded=
R;
Endangered
Species
LOC
is
exceeded=
E;
No
acute
LOC
is
exceeded=
no;
LOC
for
chronic
risk
is
exceeded=
Y;
LOC
for
chronic
risk
is
not
exceeded=
N.

Risk
to
fish
and
aquatic
invertebrates
The
following
table
summarizes
the
results
of
modeling
the
proposed
new
uses.
The
EECs
were
reduced
from
the
present
registered
use
patterns:

17
Table
3
Tier
II
Upper
Tenth
Percentile
EECs
for
Disulfoton
Parent
based
on
proposed
new
maximum
label
rates
and
management
scenarios
for
cotton,
potatoes,
and
spring
wheat
in
farm
pond.
Estimated
using
PRZM3/
EXAMS.

Crop
Disulfoton
Application
Concentration
(
µ
g/
L)

(
1­
in­
10
annual
yearly
maximum
value)
Mean
of
Annual
Means
(
µ
g/
L)

Rate
/
Number
of
Apps
/
Interval
/
Incorp.

Depth/
method
1
lb.
ai/
A
/
#
/
days
/
inches
Peak
96­
Hour
Avg.
21­
Day
Avg.
60­
Day
Avg.
90­
Day
Avg.
Annual
Avg.

Cotton
1.
00/
1/
­
/
0/
gs
10.31
9.38
6.83
3.54
2.42
0.62
0.23
Potatoes
3.00/
1/
­
/
2.5/
gs
2.42
2.18
1.67
0.84
0.57
0.15
0.12
Potatoes
0.5/
1/
­
/
0/
af
7.51
6.62
5.20
3.45
2.42
0.62
0.57
Spr.
Wheat
0.75/
1/
­
/
0/
gs
1.02
0.91
0.67
0.41
0.28
0.08
0.05
1
Method
of
application:
f
=
foliar
and
s
=
soil;
g
=
ground
and
a
=
aerial
18
The
following
tables
reflect
a
qualitative
comparative
risk
assessment
for
aquatic
and
estuarine
organisms.

Table
4
Comparison
of
potential
acute
and
chronic
risk
resulting
from
proposed
changes
in
4
use
patterns
of
Di
­
syston
8E
for
freshwater
fish
and
invertebrates
Present
Use
Fish
Invertebrates
Proposed
Use
Fish
Invertebrates
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
lb.
ai/
A
/
#
/
days
/
inches
lb.
ai/
A
/
#
/
days
/
inches
cotton
1.0/
3/
14/
0/
gs
R
Y
A
Y
cotton
1.0/
1/
­
/
0/
gs
R
N
A
Y
potatoes
4.0/
2/
14/
2.5/
gs
R
Y
A
Y
potatoes
3.0/
1/
­
/
2.5/
gs
E
N
A
Y
potatoes
1.0/
3/
14/
0/
af
R
Y
A
Y
potatoes
0.5/
3/
14­
/
0/
af
R
N
A
Y
wheat
0.75/
2/
30/
0/
gs
R
N
A
Y
wheat
0.75/
1/
­
/
0/
gs
no
N
R
Y
1
Method
of
application:
f
=
foliar
and
s
=
soil;
g
=
ground
and
a
=
aerial
Acute
=
ac;
Chronic
=
ch
Acute
risk
LOC
is
exceeded=
A;
Restricted
use
LOC
is
exceeded=
R;
Endangered
Species
LOC
is
exceeded=
E;
No
acute
LOC
is
exceeded=
no;
LOC
for
chronic
risk
is
exceeded=
Y;
LOC
for
chronic
risk
is
not
exceeded=
N.

Table
5
Comparison
of
potential
acute
and
chronic
risk
resulting
from
proposed
changes
in
4
use
patterns
of
Di
­
syston
8E
for
estuarine
fish
and
invertebrates
Present
Use
Fish
Invertebrates
Proposed
Use
Fish
Invertebrates
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
lb.
ai/
A
/
#
/
days
/
inches
lb.
ai/
A
/
#
/
days
/
inches
cotton
1.0/
3/
14/
0/
gs
no
Y
A
Y
cotton
1.0/
1/
­
/
0/
gs
no
Y
A
Y
potatoes
4.0/
2/
14/
2.5/
gs
no
Y
R
Y
potatoes
3.0/
1/
­
/
2.5/
gs
no
N
R
N
potatoes
1.0/
3/
14/
0/
af
no
Y
A
Y
potatoes
0.5/
3/
14­
/
0/
af
no
Y
A
Y
wheat
0.75/
2/
30/
0/
gs
no
Y
A
Y
wheat
0.75/
1/
­
/
0/
gs
no
N
E
N
1
Method
of
application:
f
=
foliar
and
s
=
soil;
g
=
ground
and
a
=
aerial
Acute
=
ac;
Chronic
=
ch
Acute
risk
LOC
is
exceeded=
A;
Restricted
use
LOC
is
exceeded=
R;
Endangered
Species
LOC
is
exceeded=
E;
No
acute
LOC
is
exceeded=
no;
LOC
for
chronic
risk
is
exceeded=
Y;
LOC
for
chronic
risk
is
not
exceeded=
N.

19
Summary
EFED
supports
the
proposed
use
modifications,
and
concurs
that
generally
they
reduce
risk
to
nontarget
organisms
to
varying
degrees.
Although
there
remains
the
concern
for
hypersensitive
birds
and
mammals,
the
acute
risk
to
most
birds
and
mammals
is
reduced
substantially.
The
greatest
risk
reduction
to
fish
and
aquatic
invertebrate
are
soil
applications
to
potatoes
and
wheat.
There
appears
to
be
little
changes
in
acute
risk
to
aquatic
organisms
from
the
proposed
modifications
to
cotton
and
potatoes
(
aerial
application)
.
Chronic
risk
to
terrestrial
and
aquatic
organisms
are
likely
to
be
reduced;
but
with
less
certainty,
because
the
duration
of
exposure
required
to
produce
adverse
chronic
effects
in
the
field
are
not
available.

Data
Gaps:

The
following
environmental
fate
requirements
are
not
satisfied
for
disulfoton,
D.
sulfoxide,
and
D.
sulfone:
162­
3:
Anaerobic
Aquatic
Metabolism
162­
4:
Aerobic
Aquatic
Metabolism
163­
1:
Mobility
­
Leaching
and
adsorption/
desorption
for
D.
sulfone
and
D.
sulfoxide.

Additionally,
there
is
limited
environmental
fate
data
available
for
the
sulfone
and
sulfoxide
degradates.
Data
on
the
fate
of
these
degradates
in
soil
and
water
would
allow
additional
characterization
of
the
risks
they
present
to
nontarget
organisms.

The
following
ecological
effects
data
requirements
are
not
satisfied
for
disulfoton:
122­
1:
Tier
I
Terrestrial
Plant
Testing
122­
2:
Tier
I
Aquatic
Plant
Testing
(
123­
1
and
123­
2,
Tier
II
testing,
are
reserved
pending
the
results
of
Tier
I
testing)
.
71­
3
Wild
mammal
testing
subacute
dietary
(
LC50)
.

The
value
added
for
the
wild
mammal
test
is
high.
This
study
could
resolve
the
issue
between
the
calculated
1
day
LC50
(
ranging
from
2­
12
ppm)
derived
from
the
acute
rat
acute
oral
of
1.9
mg/
kg
and
the
demeton
LC50
study
(
320
ppm)
with
95%
C.
I.
(
0
to
infinity)
.
The
risk
assessment
for
mammals
would
be
refined
with
greater
certainty.

Manufacturing­
Use
Products
 
This
pesticide
is
extremely
toxic
to
birds,
mammals,
fish
and
aquatic
invertebrates.
Do
not
discharge
effluent
containing
this
product
into
lakes,
streams,
ponds,
estuaries,
oceans,
or
public
waters
unless
this
product
is
specifically
identified
and
addressed
in
an
NPDES
permit.
do
not
discharge
effluent
containing
this
product
to
sewer
systems
without
previously
notifying
the
sewage
treatment
plant
authority.
For
guidance,
contact
your
State
Water
Board
or
Regional
Office
of
the
EPA.
 
20
End­
use
Products
Non
granular
products:
 
This
pesticide
is
extremely
toxic
to
birds,
mammals,
fish
and
aquatic
invertebrates.
Do
not
apply
directly
to
water,
or
to
areas
where
surface
water
is
present
or
to
intertidal
areas
below
the
mean
high­
water
mark.
Drift
and
runoff
may
be
hazardous
to
aquatic
organisms
in
neighboring
areas.
Do
not
contaminate
water
when
disposing
of
equipment
washwater
or
rinsate.
 
Granular
products:
This
pesticide
is
extremely
toxic
to
birds,
mammals,
fish
and
aquatic
invertebrates.
Collect
granules
spilled
during
loading
or
application.
.
Do
not
apply
directly
to
water,
or
to
areas
where
surface
water
is
present
or
to
intertidal
areas
below
the
mean
high­
water
mark.
Runoff
may
be
hazardous
to
aquatic
organisms
in
neighboring
areas.
Do
not
contaminate
water
when
disposing
of
equipment
washwater
or
rinsate.
 
Disulfoton
Bee
Mitigation
­
Suggested
Precautionary
Label
Language
for
non
granular
products:
 
This
pesticide
is
toxic
to
bees.
Application
should
be
timed
to
coincide
with
periods
of
minimum
bee
activity,
usually
between
late
evening
and
early
morning.
 
Surface
Water
Advisory
 
This
product
may
contaminate
water
through
drift
of
spray
in
wind.
This
product
has
a
high
potential
for
runoff
for
several
months.
Poorly
draining
soils
and
soils
with
shallow
watertables
are
more
prone
to
produce
runoff
that
contains
this
product.
 
Labels
for
farmers
should
add
the
following
to
the
previous
statement:

 
A
level,
well
maintained
vegetative
buffer
strip
between
areas
to
which
this
product
is
applied
and
surface
water
features
such
as
ponds,
streams,
and
springs
will
reduce
the
potential
for
contamination
of
water
from
rainfall­
runoff.
Runoff
of
this
product
will
be
reduced
by
avoiding
applications
when
rainfall
is
forecasted
to
occur
within
48
hours.
 
Labels
for
home
owners
should
add
the
following
to
the
previous
statement:

 
Avoid
applying
this
product
to
ditches,
swales,
and
drainage
ways.
Runoff
of
this
product
will
be
reduced
by
avoiding
applications
when
rainfall
is
forecasted
to
occur
within
48
hours.

Ground
Water
Advisory
Note
to
CRM:
Disulfoton
residue
detections
in
ground
water
range
from
0.04
to
100
ppb;
detections
are
up
to
300
times
the
Health
Advisory
(
0.3
ppb)
.
There
is
a
high
potential
for
degradates
to
contaminate
ground
water.
Because
disulfoton
degradates
are
persistent,
apparently
mobile,
and
parent
disulfoton
has
been
found
in
ground
water,
a
ground
water
label
advisory
is
required.
The
following
label
language
is
appropriate:

21
"
Disulfoton
is
known
to
leach
through
soil
into
ground
water
under
certain
conditions
as
a
result
of
label
use.
Use
of
this
chemical
in
areas
where
soils
are
permeable,
particularly
where
the
water
table
is
shallow,
may
result
in
ground­
water
contamination.
"

Spray
Drift
Since
disulfoton
can
be
applied
aerially,
current
cautionary
labeling
for
the
spray
drift
of
aerially
applied
pesticides
must
be
used.

22
Table
of
Contents
Amended
8/
26/
00
from
01/
13/
00
from
10/
07/
99
from
8/
26/
99
1.
Use
Characterization
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
2.
Exposure
Characterization
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
A.
Chemical
profile
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
B.
Environmental
Fate
Assessment
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2
C.
Terrestrial
Exposure
Assessment
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
7
D.
Water
Resources
Assessment
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
8
I.
Summary
and
conclusions
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
8
ii.
Application
rates
used
in
modeling
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
10
iii.
Modeling
scenarios
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
10
iv.
Modeling
procedure
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
13
v.
Modeling
results
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
15
vi.
Monitoring
data
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
23
vii.
Limits
of
this
analysis
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
29
3.
Ecological
Effects
Hazard
Assessment
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
30
A.
Toxicity
to
Terrestrial
Animals
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
30
I.
Birds,
Acute
and
Subacute
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
30
ii.
Birds,
Chronic
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
34
iii.
Mammals,
Acute
and
Chronic
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
34
iv.
Insects.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
35
v.
Terrestrial
Field
Testing
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
36
B.
Toxicity
to
Freshwater
Aquatic
Animals
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
37
I.
Freshwater
Fish,
Acute
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
37
ii.
Freshwater
Fish,
Chronic
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
39
iii.
Freshwater
Invertebrates,
Acute
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
39
iv.
Freshwater
Invertebrates,
Chronic
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
40
v.
Freshwater
Field
Studies
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
41
C.
Toxicity
to
Estuarine
and
Marine
Animals
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
42
I.
Estuarine
and
Marine
Fish,
Acute
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
42
ii.
Estuarine
and
Marine
Fish,
Chronic
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
44
iii.
Estuarine
and
Marine
Invertebrates,
Acute
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
44
iv.
Estuarine
and
Marine
Invertebrates,
Chronic
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
45
v.
Estuarine
and
Marine
Field
Studies
.
.
.
.
.
.
.
.
.
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46
D.
Toxicity
to
Plants.
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46
I.
Terrestrial
Plants
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46
ii.
Aquatic
Plants
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46
4.
Ecological
Risk
Assessment
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46
A.
Risk
to
Nontarget
Terrestrial
Animals
.
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49
I.
Birds
and
Mammals
.
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49
ii.
Insects
.
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64
B.
Risk
to
Nontarget
Aquatic
Animals
.
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64
.

C.
Risk
to
Nontarget
Plants
.
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70
5.
Endangered
Species
Consideration
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70
6.
Ecological
Incident
Reports
.
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70
7.
Risk
Characterization
.
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71
A.
Characterization
of
Fate
and
Transport
.
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72
I.
Water
Exposure
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72
a.
Surface
Water
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72
b.
Ground
Water
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.
73
B.
Characterization
or
Risk
to
Nontarget
Species
.
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75
C.
Mitigation
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80
8.
References.
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84
9.
Appendices.
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87
I.
Use
of
Disulfoton
by
Crop
and
State
.
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.
87
II.
Chemical
Structure
of
Disulfoton
.
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89
III.
Assessment
of
STORET
Monitoring
Data
.
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90
IV.
Environmental
Fate
and
Chemistry
Study
Identification
.
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92
V.
Environmental
Fate
Data
Requirements
Table
.
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94
VI.
Ecological
Effects
Data
Requirements
Table
.
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95
VII.
Percent
Crop
Area
Table
.
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98
VIII.
PRZM
and
EXAMS
values
for
Index
Reservoir
.
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..
99
IX.
PRZM
and
EXAMS
Input
and
EXAMS
Output
files
Table
.
.
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.
100
1
1.
Use
Characterization
for
Disulfoton
Disulfoton
is
a
systemic
organophosphate
insecticide,
acaracide
(
miticide)
registered
for
use
to
control
aphids,
thrips,
mealybugs,
other
sucking
insects,
and
spider
mites
on
a
variety
of
terrestrial
food
crops
(
coffee,
peppers,
broccoli,
brussels
sprouts,
cabbage,
cauliflower,
lettuce,
spinach,
asparagus,
pecan,
radish,
and
raspberries)
,
terrestrial
food
and
feed
crops
(
tomato,
barley,
corn,
oats,
triticale,
wheat,
cotton,
peanut,
peas,
sorghum,
soybeans,
potatoes,
beans,
and
lentils)
,
terrestrial
feed
crops
(
bermudagrass,
and
alfalfa)
,
and
terrestrial
nonfood
crops
(
Christmas
tree
plantations,
ornamentals,
and
non­
bearing
fruit)
.
The
total
use
of
disulfoton
for
1997
was
approximately
1.7
million
lbs
ai.
Cotton
has
the
greatest
use
of
disulfoton
(
420,000­
840,000
lb
ai/
yr)
,
accounting
for
61%
of
the
disulfoton
market.
Wheat
has
the
next
largest
percentage
of
the
market,
at
16%
(
180,000­
354,000
lb
ai/
yr)
.
The
largest
use
state
is
California
(
16%
of
the
market,
272,000
lb
ai/
yr)
,
followed
by
Louisiana
(
11%
of
the
market,
187,000
lb
ai/
yr)
.
Rankings
of
disulfoton
usage
by
crop
and
by
state
are
provided
in
Appendix
I.

Disulfoton
is
formulated
as
15%
granules,
8%
emulsifiable
systemic,
95%
cotton
seed
treatment,
systemic
granules
(
1,
2,
5,
10%
)
,
and
68%
concentrate
for
formulating
garden
products.
Applications
are
generally
soil
applied:
in­
furrow,
broadcast,
or
row
treatment
followed
by
2­
3
inch
soil
incorporation.
It
can
also
be
applied
as
a
foliar
treatment
and
in
irrigation
water.
Cotton
seeds
can
also
be
directly
treated
and
planted.
Disulfoton
can
be
applied
in
multiple
applications
(
up
to
three)
at
intervals
from
7
to
21
days
depending
upon
the
crop.
Application
rates
typically
range
from
about
0.5
to
4.00
lb
ai/
A.
A
Section24(
c)
Registration
for
North
Carolina
Christmas
trees
allows
up
to
4.5
lb
ai/
A
and
for
the
same
use,
the
Federal
Section
3
Registration
allows
for
greater
than
57
lb
ai/
A.

2.
Exposure
Characterization
A.
Chemical
Profile
1.
Common
name:
disulfoton
2.
Chemical
name:
O,
O'
­
diethyl­
S­
[
2­
ethylthio)
ethyl
]
phosphorothioate
3.
Trade
Names:
Di­
Syston
4.
Physical/
Chemical
properties:
Molecular
formula:
C8H1802PS3
Molecular
weight:
274.39
Physical
state:
colorless
liquid
Specific
gravity.
1.144
a
20
E
C.
Henry'
s
Law
Constant:
2.60E­
6
Atm.
M3/
Mol
(
measured)
Boiling
point:
62
E
C
at
0.01
mmHg
Vapor
pressure:
(
20
E
C)
=
1.8
X
10
­
4
mmHg
Solubility:
in
water
at
20
E
C=
25
ppm;
miscible
in
n­
hexane,
dichloromethane,
2­
propanol,
toluene
2
B.
Environmental
Fate
Assessment
I.
Environmental
Fate
and
Chemistry
Data
The
environmental
fate
and
chemistry
data
base
for
disulfoton
is
incomplete
for
the
parent
compound.
Less
fate
data
are
available
for
the
degradation
products.
The
major
routes
of
dissipation
are
chemical
reaction
and
microbial
degradation
in
aerobic
soil
and
aqueous
photolysis
and
soil
photolysis.
Volatilization
from
soil
and
water
is
not
expected
to
be
significant.
Data
are
unavailable
for
aerobic
and
anaerobic
aquatic
environments.
The
anaerobic
soil
metabolism
studies
have
been
submitted
to
the
Agency,
and
will
be
reviewed
by
EFED.
Disulfoton
is
essentially
stable
to
hydrolysis
at
20
E
C
at
the
three
pH
values
tested
but
is
influenced
by
temperature
as
hydrolysis
is
fairly
rapid
at
40
E
C.
The
overall
results
of
these
mechanisms
of
dissipation
appear
to
indicate
that
disulfoton
has
low
persistence.
Limited
data
suggests
that
the
degradates
are
much
more
persistent.
Disulfoton
also
appears
to
be
more
persistent
under
anaerobic
soil
conditions
than
aerobic
soil
conditions.
The
adsorption/
desorption
studies
indicate
that
disulfoton
is
slightly
to
somewhat
mobile
depending
upon
the
soil.
Aged
leaching
studies
suggested
that
D.
sulfoxide
and
D.
sulfone
degradates
did
not
leach
which
is
inconsistent
with
the
field
data,
terrestrial
field
dissipation
studies
showed
that
both
degradates
leached.
Sulfoxide
and
sulfone
degradates
of
other
organophosphate
pesticides
tend
to
be
more
mobile
than
the
parent
compound.
The
individual
studies
are
summarized
below.

Hydrolysis
(
161­
1)

The
primary
hydrolysis
products
were
the
disulfoton
oxygen
analog
(
POS)
at
pH
4,
a
mixture
of
des­
ethyl
disulfoton
metabolites
of
which
the
major
one
is
des­
ethyl
POSO2
at
pH
7
and
a
product
obtained
at
pH
9
which
converted
to
2­
2­
(
ethylsulfonyl)
ethane
sulfonic
acid
upon
treatment
with
potassium
permanganate.
The
reported
hydrolysis
half­
lives
are
1174
days,
323
days,
and
231
days
in
sterile
aqueous
buffered
solutions
at
pH
 
s
4,
7,
and
9,
respectively,
for
a
30
day
study.
Consequently,
disulfoton
is
essentially
stable
to
abiotic
degradation
at
20
E
C.
At
40
E
C,
the
half­
lives
were
30,
23.2,
and
22.7
days
at
pH
4,
7,
and
9,
respectively.
The
hydrolysis
guideline
requirement
(
161­
1)
is
fulfilled
(
MRID
00143405)
.

Photodegradation
in
water
(
161­
2)

Disulfoton
had
a
T1/
2
of
93
hours.
The
half­
life
for
aqueous
photolysis
(
corrected
for
the
dark
control)
is
93
hours
in
a
pH
5
buffered
solution
exposed
to
natural
sunlight
(
Latitude
38.05
N;
Longitude
84.30
W.
;
October
5­
15.
1987;
average
temperature
19.4
+
2.08
C
)
.
For
the
purpose
of
modeling
(
in
the
water
body)
,
the
rate
of
disulfoton
photolysis
in
water
was
considered.
Disulfoton
sulfoxide
was
the
major
degradation
product.
Control
(
dark)
samples
degraded
with
a
half­
life
of
>
300
hours.
Both
reactions
followed
zero­
order
kinetics
(
independent
of
concentration)
.
The
guideline
requirement
for
photo­
degradation
in
water
(
161­
2)
is
fulfilled
(
MRID
40471102)
.

Photodegradation
on
soil
(
161­
3)
3
The
half­
life
of
disulfoton
was
2.4
days
on
sandy
loam
soil
plates
exposed
to
natural
sunlight.
The
primary
photoproduct
was
disulfoton
sulfoxide
in
irradiated
and
dark
samples.
Less
than
10%
disulfoton
oxygen
analog
sulfoxide
and
disulfoton
sulfone
were
detected
in
the
light
exposed
samples
after
two
days
of
irradiation.
MRID
40789701
was
rejected
on
8/
23/
89
since
the
proportion
of
metabolites
formed
was
not
presented
in
the
study
report.
The
registrant
provided
this
information
in
a
letter
dated
2/
11/
92.
The
photo­
degradation
on
soil
data
requirement
(
161­
3)
is
fulfilled
(
MRID
40471103)
.

Aerobic
soil
metabolism
(
162­
1)

Literature
suggests
that
disulfoton
is
transformed
in
soil
via
microbial
metabolism
and
chemical
oxidation
(
Howard
et
al.
,
1991)
.
Primary
transformation
products
are
D.
sulfoxide
and
D.
sulfone.
Five
oxidative
metabolites,
that
persisted
for
more
than
12
weeks
(
84
days)
,
have
been
identified
in
a
paddy
soil
(
Howard
et
al.
,
1991)
.
Data
generally
suggests
that
in
soil
disulfoton
will
initially
decline
rapidly
in
soil,
but
this
decline
slows
with
time.
Reported
"
half­
lives"
of
disulfoton
tend
to
be
generally
less
than
5
days.
In
soil,
the
metabolites,
D.
sulfoxide
and
D.
sulfone,
appear
to
be
more
persistent
>
17
days
and
>
150
days,
respectively
(
MRID#
4437391)
.

The
registrant
has
submitted
a
several
studies
to
assess
the
aerobic
metabolism
rate
in
soil
(
MRID
#
s
43800100,
40042201;
41585101)
.
The
aerobic
soil
half­
life
was
calculated
by
the
registrant
to
be
15.6
days,
however,
the
reaction
did
not
follow
first­
order
kinetics
(
MRID
43800101)
.
It
was
recalculated
(
see
next
paragraph)
.
Less
than
20%
of
the
amount
applied
remained
7
days
after
treatment;
<
3%
remained
60
days
after
treatment.
The
major
degradates
are
the
sulfoxide
(
58.7%
)
at
7
days,
and
sulfone
(
72%
)
at
90
days.
At
the
end
of
the
study
(
367
days)
,
the
sulfone
was
present
at
35%
of
the
applied
amount,
and
the
sulfoxide
at
2%
of
the
applied
amount.
Except
for
the
sulfone
and
sulfoxide
degradates,
residues
were
not
detectable
at
367
days.
The
aerobic
soil
metabolism
guideline
requirement
(
162­
1)
is
fulfilled
(
MRID
43800101)
.

As
noted
above
there
is
an
issue
as
to
whether
the
decline
of
disulfoton
in
soil
follows
first­
order
kinetics
in
this
study
(
MRID
43800101)
.
The
information
reported
in
MRID
43800101
suggests
non­
first
order
kinetics
and
a
half­
life
less
than
the
"
calculated"
15.6
days
as
indicated.
The
15.6
day
half­
life
was
calculated
by
the
registrant
and
only
represents
a
portion
of
the
data
(
days
0
through
90,
days
122,
241,
and
367
were
not
included)
.
The
slope
(
decay
rate
constant,
k)
of
the
transformed
(
natural
log
or
ln)
(
ln
C(
t)
=
ln
Co
­
kt,
where
Co
is
the
initial
concentration,
C
is
concentration,
and
t
is
time)
was
significant
with
p=
0.0001
and
a
r
2
of
0.888.
From
a
statistical
standpoint,
a
first­
order
model
using
transformed
data
provides
a
reasonable
estimate
of
the
decline
rate.
However,
the
time
that
the
initial
pesticide
concentration
reaches
half
the
initial
concentration
(
e.
g.
,
half­
life)
is
less
than
the
15.6
days
suggested
by
the
analysis
of
the
transformed
data.
The
decay
rate
of
disulfoton
appears
to
follow
the
pseudo
first­
order
type
kinetics
over
the
entire
study
duration
better
than
when
nonlinear
regression
is
applied
to
untransformed
data
(
C=
Coe
­
kt
)
where
Co
is
the
initial
concentration,
C
is
concentration,
t
is
time,
and
k
is
the
decay
rate
constant.
The
parameter
k
was
estimated
by
non­
linear
regression
of
C
versus
time.
The
half­
life
(
when
C/
Co
=
0.5)
was
estimated
to
be
2.57
days
(
r
2
=
0.93)
.
The
linear
regression
of
the
ln­
transformed
dated
tended
to
over
estimate
disulfoton
residues
with
time
whereas
the
non­
linear
regression
of
the
non­
transformed
data
under
estimated
the
disulfoton
residues
with
time.
Approximately,
10
percent
of
applied
radio­
labeled
disulfoton
(
Di­
4
Syston)
was
reported
to
be
in
the
sulfoxide
state
at
time
zero
(
day
0
<
then
6
hours)
which
suggests
rapid
oxidation
to
the
corresponding
sulfoxide
metabolite.

Two
additional
aerobic
soil
metabolism
studies
(
MRID#
s
40042201;
41585101)
submitted
by
the
registrant,
determined
to
be
supplemental
studies
by
EFED,
also
provided
additional
information
which
was
considered.
These
studies
had
estimated
aerobic
half­
lives
of
2.4
and
1.9
days,
respectively.
A
half­
life
of
1.9
days
(
MRID
41585101)
was
estimated
using
the
ln­
transformed
disulfoton
percentages
from
only
the
first
three
days
(
0,
0.25,
1,
and
3
days)
of
the
experiment,
the
remaining
days
7,
14,
30,
90,
189,
270
are
not
considered.
The
decline
of
parent
disulfoton
in
these
studies
also
appeared
not
to
follow
first­
order
kinetics,
but
pseudo
first­
order
kinetics.

The
registrant
indicated
in
a
response
(
3/
8/
99
To:
P.
Poli,
From:
J.
S.
Thornton)
that
the
half­
lives
for
the
studies
submitted
as
MRID
#
43800101
and
41585101
were
5.5
and
4.1
days,
respectively.
Because
these
half­
lives
are
longer
(
more
conservative)
than
those
estimated
by
EFED
(
see
above)
,
these
values
were
used
in
the
modeling
for
the
water
assessment.

The
metabolites
(
D.
sulfoxide
and
D.
sulfone)
tended
to
be
more
persistent
with
T1/
2
of
~
17
days
and
~
150
days,
respectively
(
MRID#
4437391)
.
The
registrant
indicates,
non­
guideline
study
(
modeling
exercise)
that
the
DT50
for
disulfoton,
sulfoxide,
and
sulfone
is
5.5,
17,
and
150
days,
respectively
(
MRID
4437391)
.
The
equations
used
to
estimate
these
values
were
not
specified,
thus,
the
DT50s
(
rate
constants)
could
not
be
confirmed.

Anaerobic
soil
metabolism
(
162­
2)

Several
anaerobic
soil
metabolism
studies
have
been
submitted
to
the
EPA
(
MRID#
s
43512201,
43042503.
The
studies
indicate
that
disulfoton
is
more
persistent
under
anaerobic
soil
conditions
compared
to
aerobic
soil
conditions.
EFED
will
conduct
a
detailed
review
of
these
studies.

Anaerobic
aquatic
metabolism
(
162­
3)

This
study
(
MRID
43042503)
cannot
be
used
to
fulfill
data
requirement
162­
3.
Material
balances
were
too
low,
declining
from
106%
immediately
post­
treatment
to
78.7%
at
202
days.
Only
65%
of
the
intended
application
was
available
at
the
start
of
the
study.
The
study
cannot
be
upgraded;
a
new
anaerobic
aquatic
study
or
an
anaerobic
soil
metabolism
study
must
be
submitted
for
disulfoton.

Aerobic
aquatic
metabolism
(
162­
4)

No
data
on
aerobic
aquatic
metabolism
of
disulfoton
or
its
metabolites
have
been
submitted.
This
information
must
be
submitted
by
the
registrant.

Mobility
­
Leaching
and
Adsorption/
Desorption.
(
163­
1)

Adsorption/
desorption
studies
of
disulfoton
indicated
that
it
is
slightly
mobile
to
somewhat
mobile
depending
on
the
soil.
Adsorption/
desorption
coefficients
of
various
soil
types
are
5
tabulated
below.

Table
1.
Kd
and
Koc
Adsorption/
Desorption
Values
for
Disulfoton
for
four
soils
Soil
Texture
Silt
Loam
Sand
Clay
Loam
Sandy
Loam
Kd
6.85
4.67
4.47
9.66
Koc
(
ads.
)
449
888
386
483
Koc
(
des.
)
629
1340
547
791
The
average
organic
carbon
normalized
Freundlich
Kads
was
estimated
to
be
551.5
mL/
g
soil
carbon
from
the
data
summarized
in
the
above
Table
1.
The
Koc
(
ads.
)
model
generally
appears
to
be
appropriate
as
Kads
increase
with
organic
carbon
content
and
the
1/
n
term
in
the
Freundlich
equation
were
close
to
1
(
so
Kads
~
Kd)
.

In
a
second
report,
#
66792,
parent
Freundlich
K
values
(
7.06
to
14.29)
indicate
that
disulfoton
is
adsorbed
to
a
moderate
degree
which
also
reflects
low
mobility
in
soils.
The
average
Di­
Syston
Rf
value
was
0.22
on
six
soils
which
also
indicates
low
mobility
of
the
parent
disulfoton.
The
correlation
coefficients
describing
the
degree
of
data
conformity
to
the
Freundlich
equation
ranged
from
90.3
to
99.9%
.
The
1/
n
values
for
the
three
soils
were
1.002,
0.980,
and
0.975.
Calculated
Kocs
were
641,
752,
and
839.
The
mobility­
leaching
and
adsorption/
desorption
guideline
requirement
(
163­
1)
is
fulfilled
(
MRID
#
443731­
03
and
00145469)
.
These
data
were
also
recorded
in
Bayer'
s
11/
30/
93
letter
to
SRRD,
MRID
­
430425­
00
pages
3
and
4.
)

Adsorption/
desorption
data
are
needed
for
D.
sulfoxide
and
D.
sulfone.

Mobility
­
Leaching
of
Aged
Di­
Syston
(
163­
1)

This
1986
study
(
Acc.
#
00145470)
was
not
conducted
in
accordance
with
acceptable
guidelines,
and
the
1986
results
were
not
consistent
with
current
data
using
guideline
studies.
Recent
data
indicate
that
the
degradates
will
leach
to
lower
depth,
but
the
1986
study
indicated
no
leaching
of
sulfoxide
and
sulfone
degradates.
A
new
column
leaching
study
is
not
required,
because
other
existing
data
fulfill
the
requirement.

Laboratory
Volatility
(
163­
2)

Disulfoton
volatilized
at
maximum
of
0.026
and
0.096
µ
g/
Cm
2/
hr
from
sand
soil
adjusted
to
25%
and
75%
of
field
capacity
at
0.33
bar
respectively,
incubated
in
dark
for
21
days
at
25
E
C
with
an
air
flow
of
approximately
300
mL/
minute.
Maximum
volatilization
occurred
within
24
hours
following
treatment.
The
vapor
pressure
of
disulfoton
was
reported
to
be
7.2
X
10
­
5
mBar
at
20
E
C
and
1.3
X
10
­
5
mBar
at
25
E
C.
Freundlich
Kads
for
the
sand
soil
was
determined
to
be
0.172.
The
guideline
requirement
for
laboratory
volatility
(
163­
2)
has
been
fulfilled
(
MRID
42585802)
6
Field
Volatility
(
163­
2)

Maximum
concentration
observed
in
air
at
1
foot
above
ground
was
22.2
ng/
L.
Disulfoton
concentrations,
after
6
hours,
at
the
5
foot
level
were
not
detectable.
Bayer,
Inc.
submitted
additional
data,
e.
g.
,
ads.
/
des.
Kds,
and
cloud
covering
on
the
days
of
the
experiment.
The
guideline
requirement
for
field
volatility
(
163­
2)
has
been
fulfilled
(
MRID
40471105)
.

Terrestrial
Field
Dissipation
(
164­
1)

Disulfoton
applied
at
8
lbs.
/
ac
dissipated
with
a
T1/
2
of
2
to
4
days
from
the
upper
6
inches
of
sand/
sandy
loam
and
loamy
sand/
sandy
loam
plots
in
California.
Parent
disulfoton
was
detected
only
in
the
upper
6
inches
of
soil,
the
sulfoxide
and
sulfone
degradates
were
detected
to
a
depth
of
18
inches.
The
guideline
requirement
for
terrestrial
field
dissipation
(
164­
1)
has
been
fulfilled
(
MRID
43042502)
.

Fish
Bioaccumulation
(
165­
4)

From
60.8
to
85.9
ppb
14
C
residues
in
edible
fish
and
38.1
to
39.9
ppb
in
the
inedible
fish
tissues
were
not
characterized.
After
14
days
depuration,
fillet
contained
21%
of
the
applied
residues,
viscera
18.1%
,
and
whole
fish
22%
.
Bioconcentration
factors
were
460X
for
whole
fish,
700X
for
viscera,
and
460X
for
fillet.
Bayer
submitted
data,
at
the
Agency
 
s
request,
which
indicated
that
there
was
no
mortality
and
no
growth
during
the
study.
The
bioaccumulation
guideline
(
165­
4)
has
been
partially
fulfilled
(
MRID
43042501,
43060101,
40471106,
and
40471107)
.
No
further
bioaccumulation
testing
is
required
for
parent
disulfoton,
however,
bioaccumulation
information,
or
at
least
Kow
determination,
for
the
sulfone
and
sulfoxide
degradates
would
be
helpful
for
risk
assessment
purposes.

Foliar
Dissipation
(
Non­
Guideline
Study
­
Supporting
Information)

The
foliar
dissipation
rate
of
3.3
days
is
based
on
field
monitoring
data
(
MRID
#
41201801)
.
Disulfoton
was
aerially
applied
to
potatoes
3
times
at
1
lb
ai/
acre
in
Michigan.
Potato
foliage
was
collected
from
five
different
treated
fields
with
six
sampling
stations
in
each
field.
Samples
were
collected
the
day
before
and
the
day
after
each
of
the
three
treatments,
and
then
on
day
7
and
14
after
the
third
(
final)
treatment.
The
foliar
dissipation
rate
estimates
are
based
on
the
samples
collected
after
the
third
treatment.
The
following
table
shows
the
average
residue
levels
on
potato
foliage
on
days
1,
7
and
14
from
the
five
fields,
across
all
6
sample
stations
and
the
average
for
all
fields.

EFED
determined
that
the
90
th
percentile
upper
bound
foliar
dissipation
half­
life
for
disulfoton
of
3.3
days
is
used
for
both
terrestrial
exposure
assessment,
and
in
PRZM­
EXAMS
when
foliar
dissipation
is
applicable
7
Table
2.
Residue
data
and
the
calculated
foliar
dissipation
half­
life
based
on
measured
residues
of
disulfoton
on
potato
foliage
after
the
third
application.
Residues
in
g/
g
(
ppm)
.

Time
field
1*
field
2*
field
3*
field
4*
field
5*
average
of
all
fields
day
1513634404040
day
7
4.8
4.7
8.5
5.3
5.9
5.8
day
14
1
0.9
1.9
1.6
4.2
1.9
half­
life
(
days)
2.3
2.4
3.1
2.8
4
2.98
upper
90%
CL
3.3
*
average
across
all
stations
C.
Terrestrial
Exposure
Assessment
For
pesticides
applied
as
a
nongranular
product
(
e.
g.
,
liquid,
dust)
,
the
estimated
environmental
concentrations
(
EECs)
on
food
items
following
product
application
are
compared
to
LC50
values
to
assess
risk.
The
predicted
0­
day
maximum
and
mean
residues
of
a
pesticide
that
may
be
expected
to
occur
on
selected
avian
or
mammalian
food
items
immediately
following
a
direct
single
application
at
1
lb
ai/
A
are
tabulated
below.

Table
3.
Estimated
Environmental
Concentrations
on
Avian
and
Mammalian
Food
Items
(
ppm)
Following
a
Single
Application
at
1
lb
ai/
A)

Food
Items
EEC
(
ppm)
Predicted
Maximum
Residue
1
EEC
(
ppm)
Predicted
Mean
Residue
1
Short
grass
240
85
Tall
grass
110
36
Broadleaf/
forage
plants,
and
small
insects
135
45
Fruits,
pods,
seeds,
and
large
insects
15
7
1
Predicted
maximum
and
mean
residues
are
for
a
1
lb
ai/
A
application
rate
and
are
based
on
Hoerger
and
Kenaga
(
1972)
as
modified
by
Fletcher
et
al.
(
1994)
.

Predicted
residues
(
EECs)
resulting
from
multiple
applications
are
calculated
in
various
ways.
For
this
assessment,
maximum
disulfoton
EECs
were
calculated
using
Hoerger
and
Kenaga
(
1972)
as
modified
by
Fletcher
et
al.
(
1994)
.
These
EECs
served
as
inputs
into
the
FATE
8
program.
The
FATE
program
is
a
first
order
dissipation
model,
i.
e.
,
the
pesticide
is
applied
repeatedly,
but
degrades
over
time
from
the
first
application
to
some
assigned
time
there
after.
In
the
case
of
disulfoton
the
time
period
was
30
days.
A
foliar
degradation
half
life
of
3.3
days
was
selected
based
on
a
field
monitoring
study
(
MRID
#
41201801)
.
EEC
values
for
a
variety
of
crops
and
application
rates/
methods
are
provided
in
the
risk
quotient
tables
in
Section
4,
 
Ecological
Risk
Assessment.
 
D.
Water
Resources
Assessment
i.
Summary
and
Conclusions
This
section
presents
the
assessment
of
the
potential
of
disulfoton
(
and
degradates)
to
contaminate
surface
water
and
ground
water
from
label
uses.
The
assessment
includes
a
Tier
II
estimates
of
environmental
concentrations
(
EECs)
of
disulfoton
and
total
disulfoton
residues
(
TDR
sum
of
disulfoton,
D.
sulfoxide,
and
D.
sulfone)
in
surface
water
and
SCI­
GROW
estimates
of
ground
water
concentrations,
and
the
available
monitoring
data
which
primarily
addresses
only
parent
disulfoton.
Tier
I
was
not
included
because
EECs
levels
of
concern
are
generally
exceeded
for
organophosphate
insecticides,
thus,
necessitating
a
more
refined
evaluation.
The
ecological
exposure
assessment
used
the
standard
farm
pond
scenarios
and
the
drinking
water
assessment
utilized
the
Index
Reservoir
and
Percent
Crop
Area
concepts.

The
Tier
II
modeling
of
disulfoton
residue
concentrations
in
surface
water
used
the
PRZM3
and
EXAMS
models
as
applied
to
barley,
cotton,
potatoes,
tobacco,
and
spring
wheat,
using
maximum
label
application
rates
and
several
application
methods.
Surface
water
monitoring
data
collected
by
the
USGS
as
part
of
the
National
Water
Quality
Assessment
(
NAWQA)
(
Gilliom,
1995;
USGS,
1997)
program,
USEPA'
s
STORET,
and
any
State
study
that
measured
disulfoton
in
surface
water
were
also
considered.
The
potential
for
disulfoton
residues
in
ground
water
is
assessed
using
the
EFED
ground­
water
concentration
screening
model
(
SCI­
GROW)
and
the
monitoring
data
available
in
EFED
 
s
Pesticides
in
Ground
Water
Data
Base
(
PGWDB)
(
USEPA,
1992)
,
USGS
NAWQA
study
(
USGS,
1997)
,
and
STORET
(
search
date
10/
16/
97)
.
The
purpose
of
this
analysis
is
to
provide
an
estimate
of
environmental
concentrations
of
disulfoton
(
and
degradates)
in
surface
water
bodies
and
ground
water
for
use
in
the
human
health
and
ecological
risk
assessment
as
part
of
the
registration
process.
The
environmental
fate
data
base
is
not
complete
for
disulfoton.
Limited
data
indicates
that
the
degradates
are
much
more
persistent
and
mobile
than
parent
disulfoton.
Organophosphate
degradates
are
often
as
toxic
as
the
parent
compound
and
are
considered
in
this
assessment
as
total
disulfoton
residues
(
TDR)
.
However,
as
noted,
since
data
are
lacking
there
is
considerable
uncertainty
in
these
estimates.

Surface­
and
ground­
water
monitoring
data
available
in
STORET
were
evaluated
in
detail,
but
were
generally
not
considered
due
to
limitations
associated
with
high
detection
limits
and
difficulty
in
interpreting
the
data.
Detailed
discussion
of
the
STORET
findings
is
presented
in
the
Appendix
III
.

The
Tier
II
EEC
assessment
uses
a
single
site,
or
multiple
single
sites,
which
represents
a
high­
end
exposure
scenario
from
pesticide
use
on
a
particular
crop
or
non­
crop
use
site
for
ecological
exposure
assessments.
The
EECs
for
disulfoton
were
generated
for
multiple
crop
scenarios
using
PRZM3.12
(
Carsel,
1997;
5/
7/
98)
which
simulates
the
erosion
and
run­
off
from
an
9
agricultural
field
and
EXAMS
2.97.5
(
Burns,
1997;
6/
13/
97)
which
simulates
the
fate
in
a
surface
water
body.
PRZM3
and
EXAMS
estimates
for
a
single
site,
over
multiple
years,
EECs
for
a
1
ha
surface
area,
2
m
deep
farm
pond
draining
an
adjacent
10
ha
barley,
cotton,
potato,
tobacco,
or
spring
wheat
field.
Each
scenario,
or
site,
was
simulated
for
20
to
40
(
depending
on
data
availability)
years.
EFED
estimated
1
in
10
year
maximum
peak,
4­
day
average,
21­
day
average,
60­
day
average,
90­
day,
annual
average
concentrations,
and
the
mean
of
the
annual
averages.
Disulfoton
(
Di­
Syston)
formulations
were
based
upon
registered
uses
on
the
specific
crops.
The
application
rates
(
maximum
on
label
;
EPA
Reg.
No.
3125­
172,
3125­
307)
,
numbers,
and
intervals
are
listed
in
Tables
7a.
and
7b.
and
Tables
8a.
and
8b.
and
environmental
fate
inputs
are
listed
in
Table
6.
PRZM
simulations
were
run
using
maximum
application
rates,
maximum
number
of
yearly
applications,
and
the
shortest
recommended
application
interval.
Spray
drift
is
determined
by
method
of
pesticide
application
(
and
assumed
to
be
5%
for
aerial
spray;
1%
for
ground
spray,
0%
for
granular
or
soil
incorporated
applications)
per
EFED
guidance
for
the
pond
scenarios
(
USEPA,
1999)
.

The
PRZM/
EXAMS
EECs
are
generated
for
high
exposure
agricultural
scenarios
and
represent
one
in
ten
year
EECs
in
a
stagnant
pond
with
no
outlet
that
receives
pesticide
loading
from
an
adjacent
100%
cropped,
100%
treated
field
for
parent
disulfoton
and
total
disulfoton
residues.
As
such,
the
computer
generated
EECs
represents
conservative
screening
levels
for
ponds,
lakes,
and
flowing
water
and
should
only
be
used
for
screening
purposes.
The
EECs
have
been
calculated
so
that
in
any
given
year,
there
is
about
a
10%
probability
that
the
maximum
average
concentration
of
that
duration
in
that
year
will
equal
or
exceed
the
EEC
at
the
site.
Tier
II
upper
tenth
percentile
EECs
for
disulfoton
and
total
disulfoton
residues
are
presented
in
Tables
7a.
and
7b.
and
8a.
and
8b.
for
the
pond
and
the
index
reservoir
with
PCA
adjustment,
respectively.

The
sites
selected
are
currently
used
by
EFED
(
standard
scenarios)
to
represent
a
reasonable
 
at
risk
 
soil
for
the
region
or
regions
being
considered.
.
The
scenarios
selected
represent
high­
end
exposure
sites.
The
sites
are
selected
so
that
they
generate
exposures
larger
than
for
most
sites
(
about
90
percent)
used
for
growing
the
selected
crops.
An
 
at
risk
 
soil
is
one
that
has
a
high
potential
for
run­
off
and
soil
erosion.
Thus,
these
scenarios
are
intended
to
produce
conservative
estimates
of
potential
disulfoton
concentrations
in
surface
water.
The
crop,
MLRA,
state,
site,
and
soil
conditions
for
each
scenario
are
given
in
Tables
4
and
5.

The
SCI­
GROW
(
Screening
Concentration
in
Ground
Water)
screening
model
developed
in
EFED
(
Barrett,
1997)
was
used
to
estimate
potential
ground
water
concentrations
for
disulfoton
parent
and
total
disulfoton
residues
under
 
generic
 
hydrologically
vulnerable
conditions.
.
SCI­
GROW
provides
a
screening
concentration,
an
estimate
of
likely
ground
water
concentrations
if
the
pesticide
is
used
at
the
maximum
allowed
label
rate
in
areas
with
ground
water
exceptionally
vulnerable
to
contamination.
In
most
cases,
a
majority
of
the
use
area
will
have
ground
water
that
is
less
vulnerable
to
contamination
than
the
areas
used
to
derive
the
SCI­
GROW
estimate.

ii.
Application
Rates
Used
in
Modeling
The
application
rates
(
Tables
7a
and
b,
8a
and
8b)
selected
for
use
in
the
modeling
scenarios
10
were
based
upon
information
submitted
by
the
registrant,
analysis
conducted
by
BEAD,
and
the
disulfoton
(
Di­
Syston)
labels.
Four
factors
went
into
selecting
the
application
rate:
1)
the
range
of
ounces
or
pounds
a.
i.
;
2)
the
area
or
length
of
row
per
acre
(
which
is
influenced
by
row
spacing)
;
3)
the
number
of
applications;
and
4)
the
application
interval.
The
maximum
rate
(
ounces
or
pounds
a.
i.
per
crop
simulated)
and
the
shortest
application
intervals
were
selected.
The
shorter
the
distance
between
the
crop
rows
the
greater
the
application
rates
on
an
area
basis.

iii.
Modeling
Scenarios
Surface
Water:
The
disulfoton
scenarios
(
Tables
4
and
5)
are
representative
of
high
run­
off
sites
for
barley
in
the
Southern
Piedmont
of
Virginia
(
MLRA
136)
,
cotton
in
the
Southern
Mississippi
Valley
Silty
Uplands
of
Mississippi
(
MLRA
134)
,
potatoes
in
the
New
England
and
Eastern
New
York
Upland
of
Maine
(
MLRA
144A)
,
tobacco
in
Southern
Coastal
Plain
of
Georgia
(
MLRA
133A)
,
and
spring
wheat
in
the
Rolling
Till
Prairie
of
South
Dakota
(
MLRA
102A)
.
The
scenarios
chosen
are
professional
best
judgement
sites
expected
to
produce
run­
off
greater
than
would
be
expected
at
90%
of
the
sites
where
the
appropriate
crop
is
grown.
Soils
property
data
(
Table
5)
and
planting
date
information
were
obtained
from
the
PRZM
Input
Collator
(
PIC)
data
bases
(
Bird
et
al,
1992)
.
The
Percent
Crop
Area
(
PCA)
values
used
for
the
five
scenarios
for
estimated
drinking
water
concentrations
are
also
given
in
Table
4.
11
Table
4.
Crop,
location,
soil
and
hydrologic
group
for
each
modeling
scenario.

Crop
MLRA
1
State
Soil
Series
Soil
Texture
Hydrologic
Group
Period
(
Years)
PCA
2
Barley
136
VA
Gaston
sandy
clay
loam
C270.
87
Cotton
131
3
MS
Loring
silt
loam
C
20
0.
20
Potatoes
144A
ME
Paxton
sandy
loam
C
36
0.
87
Tobacco
133A
GA
Emporia
loamy
sand
C
36
0.
87
Spr.
Wheat
102A
SD
Peever
clay
loam
C
40
0.
56
1
MLRA
is
major
land
resource
area
(
USDA,
1981)
.
2
PCA
is
the
Percent
Crop
Area.
3
Meteorological
file
met131.
met
is
used
in
the
EFED
standard
cotton
scenario,
since
the
weather
station
is
closer
to
the
simulated
site.

Table
5.
Selected
soil
properties
used
modeling.

Soil
Series
(
MLRA)
Depth
(
in)
Bulk
Density
(
g/
cm
3
)
Organic
Carbon
(
%
)
Field
Capacity
(
cm
3
/
cm
3
)
Wilting
Point
(
cm
3
/
cm
3
)

Gaston
(
136)
16
1.6
1.740
0.246
0.126
84
1.6
0.174
0.321
0.201
50
1.6
0.116
0.222
0.122
Loring
(
131)
10
1.6
1.160
0.294
0.094
10
1.6
1.160
0.294
0.094
105
1.8
0.174
0.147
0.087
Paxton
(
144A)
20
1.6
2.90
0.166
0.66
46
1.8
0.174
0.118
0.38
34
1.8
0.116
0.085
0.035
Emporia
(
133A)
38
1.4
1.16
0.104
0.054
62
1.6
0.174
0.225
0.125
50
1.6
0.116
0.135
0.056
Peever
(
102A)
18
1.35
1.740
0.392
0.202
82
1.60
0.116
0.257
0.177
50
1.60
0.058
0.256
0.176
Ground
Water:
The
SCI­
GROW
(
Screening
Concentration
in
Ground
Water)
screening
model
developed
in
EFED
(
Barrett,
1997)
was
used
to
estimate
potential
ground
water
concentrations
for
disulfoton
parent
and
total
disulfoton
residues
under
 
generic
 
hydrologically
vulnerable
12
conditions,
but
necessarily
the
most
vulnerable
conditions.
The
SCI­
GROW
model
is
based
on
scaled
ground
water
concentrations
from
ground
water
monitoring
studies,
environmental
fate
properties
(
aerobic
soil
half­
lives
and
organic
carbon
partitioning
coefficients­
Koc'
s)
and
application
rates.

iv.
Modeling
Procedure
Environmental
fate
parameters
used
in
PRZM3
and
EXAMS
runs
are
summarized
in
Table
6.
The
standard
EFED
pond
(
mspond)
was
used.
The
PRZM3
simulations
were
run
for
a
period
of
36
years
on
potatoes,
and
tobacco,
beginning
on
January
1,
1948
and
ending
on
December
31,
1983.
Barley
was
run
for
27
years
(
1956­
1983)
and
spring
wheat
was
run
for
40
years
(
1944­
1983)
.
Cotton
was
run
for
20
years
of
data
(
January
1,
1964­
December
31,
1983)
.
Scenario
information
is
summarized
in
Tables
4
and
5.
The
EXAMS
loading
(
P2E­
C1)
files,
a
PRZM3
output,
were
pre­
processed
using
the
EXAMSBAT
post­
processor.
EXAMS
was
run
for
the
20­
40
years
using
Mode
3
(
defines
environmental
and
chemical
pulse
time
steps)
.
For
each
year
simulated,
the
annual
maximum
peak,
96­
hour,
21­
day,
60­
day,
90­
day
values,
and
annual
means
in
addition
to
the
mean
of
annual
means
were
extracted
from
the
EXAMS
output
file
REPORT.
XMS
with
the
TABLE20
post­
processor.
The
10
year
return
EECs
(
or
10%
yearly
Exceedence
EECs)
listed
in
Tables
7a.
,
7b.
,
8a.
and
8b.
were
calculated
by
linear
interpolation
between
the
third
and
fourth
largest
values
by
the
program
TABLE20.
Table
6.
Disulfoton
fate
properties
and
values
used
in
(
PRZM3/
EXAMS)
modeling.

Parameter
Value
Source
Molecular
Weight
274.39
MRID
150088
Water
Solubility
15
mg/
l
@
20
MRID
150088
Henry
 
s
Law
Coefficient
2.
60
atm­
m3/
mol
EFED
One­
liner
05/
21/
97
Partition
Coefficient
(
Koc)
551.5
(
mean
of
4
)
MRID
43042500
Vapor
Pressure
1.8E­
04
mmHg
EFED
One­
liner
05/
21/
97
Hydrolysis
Half­
lives
@
pH
4
pH
7
pH
9
1174
days
323
 
231
 
MRID
143405
Hydrolysis
Rate
Constants
(
needed
for
EXAMS
derived
from
Hydrolysis
halflives
Kah
=
(
negative)
Knh
=
8.88E­
05
Kbh
=
3.58
Aerobic
Soil
Half­
life
(
Disulfoton)
6.12
days
(
0.113/
d)
Upper
90%
confidence
bound
on
the
mean
of
"
half­
lives"
for
the
two
aerobic
soils
tested
in
the
laboratory.
MRIDs
40042201,
41585101,
43800101
Aerobic
Soil
Half­
life
1
(
Total
Disulfoton
Residues)
259.63
days
(
2.67E­
03/
d)
Upper
90%
confidence
bound
on
the
mean
of
half­
lives
for
the
two
aerobic
soils
tested
in
the
laboratory.
MRIDs
40042201,
41585101,
43800101
Water
Photolysis
3.87
days
(
pH
=
5)
(
0.179/
d)
MRID
40471102
Aerobic
Aquatic
Half­
life
(
Disulfoton)
(
Kbaws,
Kbacs)
12.2
days
(
0.05682/
day)
Estimated
per
EFED
guidance
Aerobic
Aquatic
Half­
life
(
Total
Disulfoton
Residues)
(
Kbaws,
Kbacs)
259.63
days
(
2.67E­
03/
d)
Did
not
multiple
half­
life
by
2
per
EFED
guidance
to
account
for
uncertainty.
Half­
lives
greater
than
a
year
would
show
residue
accumulation.

Foliar
Dissipation
Rate
3.3
days
(
0.21/
d)
MRID
41201801
1
Half­
lives
for
total
residues
were
determined
from
the
total
residues
at
each
sampling
interval.
Total
disulfoton
residues
did
follow
first­
order
kinetic
decay
(
The
slope
(
decay
rate
constant,
k)
of
the
transformed
(
natural
log
or
ln)
(
ln
C(
t)
=
ln
Co
­
kt,
where
Co
is
the
initial
concentration,
C
is
concentration,
and
t
is
time)
)
.

v.
Modeling
Results
13
a.
Surface
water
In
the
Tier
II
assessment,
the
mean
of
the
annual
mean
concentrations
of
disulfoton
(
Table
7a)
in
a
farm
pond
over
multiple
years
simulated
ranged
from
0.21
µ
g/
L
for
a
two
applications
(
@
0.83
lb
ai/
a)
to
barley
in
Virginia
to
1.14
µ
g/
L
for
potatoes
in
Maine
with
the
three
applications
at
the
maximum
application
rate
(
@
1.00
lb
ai/
ac)
.
The
one­
in­
ten
year
maximum,
or
peak,
estimated
concentrations
of
26.75
µ
g/
L
occurred
for
one
4.0
lb.
ai/
ac
applications
of
disulfoton
to
tobacco
in
Georgia.
For
the
other
scenarios
or
recommended
application
rates,
the
maximum
concentrations
ranged
from
7.14
to
18.46
µ
g/
L.
Because
of
limited
data,
the
modeling
results,
therefore,
cannot
be
confirmed
by
the
monitoring
data.

Because
the
degradates
of
disulfoton
(
including
oxygen
analogs)
:
sulfoxide
and
sulfone
are
also
toxic,
the
EECs
of
the
total
disulfoton
residue
(
TDR)
in
a
farm
pond
was
also
considered
(
Table
7b)
.
The
overall
estimated
of
the
multiple
year
mean
concentrations
of
TDR
in
a
farm
pond
over
multiple
years
simulated
ranged
from
3.89
µ
g/
L
for
two
applications
at
the
maximum
rate
(
1.00
lb
ai/
A)
to
barley
in
Virginia
to
9.32
µ
g/
L
for
tobacco
in
Georgia
with
one
application
at
the
maximum
application
rate
(
4.00
lb
ai/
A)
.
Maximum,
or
peak,
estimated
TDR
concentrations
of
58.47
µ
g/
L
occurred
for
one
4.00
lb.
ai/
ac
application
of
disulfoton
to
tobacco.
For
the
other
scenarios,
the
maximum
TDR
concentrations
ranged
from
15.32
to
52.93
µ
g/
L.
There
are
no
monitoring
data
to
evaluate
these
concentration
estimates
from
PRZM/
EXAMS
modeling.
Water
samples
collected,
following
a
fish
kill
incident
in
Colorado,
contained
disulfoton
sulfoxide
at
levels
of
29.5­
48.7
µ
g/
L,
and
disulfoton
sulfone
at
0.0199­
0.214
µ
g/
L.
The
source
of
the
disulfoton
was
Di­
Syston
E.
C.
applied
to
wheat
which
was
followed
by
heavy
rain
fall.
(
Incident
Report
No.
I001167­
001)
.

The
PRZM/
EXAMS
estimated
disulfoton
residue
concentrations
in
surface
water
appear
to
be
strongly
related
to
the
application
rate,
number
of
applications,
application
interval,
and
method
of
application
and
timing
to
application
to
rainfall
events.

14
Mean
of
Annual
Means
(
µ
g/
L)
0.
50
0.21
0.48
0.
33
1.14
0.66
0.42
0.
66
Table
7a.
Tier
II
Upper
Tenth
Percentile
EECs
for
Disulfoton
Parent
Used
on
barley,
cotton,

potatoes,
tobacco,
and
spring
wheat
for
several
application
(
Label
maximum)
rates
and
management
scenarios
estimated
using
PRZM3/
EXAMS
in
standard
farm
pond.

Concentration
(
µ
g/
L)

(
1­
in­
10
annual
yearly
maximum
value)
Annual
Avg.
0.
79
0.49
0.92
0.
44
1.23
1.72
1.15
0.
73
90­
Day
Avg.
2.
.
82
1.73
3.44
1.
80
4.89
6.87
4.64
2.
76
60­
Day
Avg.
3.
79
2.37
4.91
2.
59
6.89
9.94
6.74
3.
81
21­
Day
Avg.
5.
96
4.36
8.05
4.
51
10.40
17.89
12.54
5.
47
96­
Hour
Avg.
7.
93
6.
32
12.96
6.
40
13.24
24.33
16.79
7.
95
Peak
9.
20
7.
14
14.79
7.
14
15.02
26.75
18.46
8.
90
Disulfoton
Application
Rate
/
Number
of
Apps
/
Interval
/
Incorp.

Depth
/
method
1
lb.
ai/
A
/
#
/
days
/
inches
1.0
/
2/
21/
0/
f
0.83/
2/
21/
0/
s
(
granular)

1.
0
/
3/
21/
0/
s
4.0
/
2/
14/
2.5/
s
1.0/
3/
14/
0/
f
4.0/
1/
0/
2.5/
s
(
granular)

4.0/
1/
0/
2.5/
s
0.75/
2/
30/
0/
f
Crop
Barley
Barley
Cotton
Potatoes
Potatoes
Tobacco
Tobacco
Spr.
Wheat
1
Method
of
application:
f
=
foliar
and
s
=
soil
15
Mean
of
Annual
Means
(
µ
g/
L)
4.94
3.89
9.13
4.48
8.37
9.32
7.16
4.73
Table
7b.
Tier
II
Upper
Tenth
Percentile
EECs
for
Total
Disulfoton
Residues
Used
on
barley,

cotton,
potatoes,
tobacco,
and
spring
wheat
for
several
application
(
Label
maximum)
rates
and
management
scenarios
estimated
using
PRZM3/
EXAMS
in
standard
farm
pond.

Concentration
(
µ
g/
L)

(
1­
in­
10
annual
yearly
maximum
value)
Annual
Avg.
7.51
6.60
15.61
6.02
9.75
15.23
13.36
5.65
90­
Day
Avg.
16.48
14.46
32.41
10.97
19.33
35.30
31.94
11.29
60­
Day
Avg.
17.35
15.02
34.37
12.20
20.88
39.57
35.68
12.56
21­
Day
Avg.
19.27
17.44
39.27
13.51
23.92
49.54
44.76
14.91
96­
Hour
Avg.
20.99
19.34
43.50
14.94
26.59
56.35
51.03
16.36
Peak
21.77
19.95
44.78
15.43
27.36
58.47
52.93
16.92
Disulfoton
Application
Rate
/
Numberof
Apps
/
Interval
/
Incorp.

Depth
/
method
1
lb.
ai/
A
/
#
/
days
/
inches
1.0
/
2/
21/
0/
f
0.83/
2/
21/
0/
s
(
granular)

1.
0
/
3/
21/
0/
s
4.0
/
2/
14/
2.5/
s
1.0/
3/
14/
0/
f
4.0/
1/
0/
2.5/
s
(
granular)

4.0/
1/
0/
2.5/
s
0.75/
2/
30/
0/
f
Crop
Barley
Barley
Cotton
Potatoes
Potatoes
Tobacco
Tobacco
Spr.
Wheat
1
Method
of
application:
f
=
foliar
and
s
=
soil
16
Surface
Water
Drinking
Water
Assessment
with
Index
Reservoir
and
Percent
Crop
Area
The
estimated
drinking
water
concentrations
(
EDWCs)
were
evaluated
using
the
methodology
outlined
in
EPA­
OPP
draft
Guidance
for
Use
of
the
Index
Reservoir
and
Percent
Crop
Area
Factor
in
Drinking
Water
Exposure
Assessments
(
USEPA,
2000)
.
This
generally
results
in
the
modification
of
the
scenarios
developed
for
farm
ponds
to
scenarios
for
the
index
reservoirs.

The
purpose
the
Index
Reservoir
(
IR)
scenario
and
the
Percent
Crop
Area
(
PCA)
for
use
in
estimating
the
exposure
in
drinking
water
derived
from
vulnerable
surface
water
supplies.
Since
the
passage
of
the
Food
Quality
Protection
Act
(
FQPA)
in
1997,
the
Agency
has
been
using
the
standard
farm
pond
as
an
interim
scenario
for
drinking
water
exposure
and
has
been
assuming
that
100%
of
this
small
watershed
is
planted
in
a
single
crop.
The
Agency
is
now
implementing
the
index
reservoir
to
represent
a
watershed
prone
to
generating
high
pesticide
concentrations
that
is
capable
of
supporting
a
drinking
water
facility
in
conjunction
with
the
percent
cropped
area
(
PCA)
which
accounts
for
the
fact
that
a
watershed
large
enough
to
support
a
drinking
water
facility
will
not
usually
be
planted
completely
to
a
single
crop.
These
two
steps
are
intended
to
improve
the
quality
and
accuracy
of
the
drinking
water
exposure
for
pesticides
obtained
by
models.

Percent
Crop
Area
(
PCA)
:
PCA
is
a
generic
watershed­
based
adjustment
factor
that
will
be
applied
to
pesticide
concentrations
estimated
for
the
surface
water
component
of
the
drinking
water
exposure
assessment
using
PRZM/
EXAMS
with
the
index
reservoir
scenario.
The
output
generated
by
the
linked
PRZM/
EXAMS
models
is
multiplied
by
the
maximum
percent
of
crop
area
(
PCA)
in
any
watershed
(
expressed
as
a
decimal)
generated
for
the
crop
or
crops
of
interest.
Currently,
OPP
has
PCA
adjustments
for
four
major
crops
 
corn,
,
cotton,
soybeans,
and
wheat.
Two
are
appropriate
for
disulfoton,
cotton
and
wheat.

The
concept
of
a
factor
to
adjust
the
concentrations
reported
from
modeling
to
account
for
land
use
was
first
proposed
in
a
presentation
to
the
SAP
in
December
1997
(
Jones
and
Abel,
1997)
.
This
guidance
results
from
a
May
1999
presentation
to
the
FIFRA
Scientific
Advisory
Panel
(
SAP)
,
Proposed
Methods
For
Determining
Watershed­
derived
Percent
Crop
Areas
And
Considerations
For
Applying
Crop
Area
Adjustments
to
Surface
Water
Screening
Models
,
and
the
response
and
recommendations
from
the
panel.
A
more
thorough
discussion
of
this
method
and
comparisons
of
monitoring
and
modeling
results
for
selected
pesticide/
crop/
site
combinations
is
located
at:
http:
/
/
www.
epa.
gov/
scipoly/
sap/
1999/
may/
pca_
sap.
pdf.

The
Agency
will
continue
to
develop
PCAs
for
other
major
crops
in
the
same
manner
as
was
described
in
the
May
1999
SAP
presentation.
However,
the
Agency
expects
that
it
will
use
smaller
watersheds
for
these
calculations
in
the
near
future.
For
minor­
use
crops,
the
SAP
found
that
the
use
of
PCAs
produced
less
than
satisfactory
results
and
advised
OPP
to
further
investigate
possible
sources
of
error.
Thus,
for
the
near
term,
OPP
is
not
be
using
PCAs
in
a
crop­
specific
manner
for
both
major
crops
that
do
not
yet
have
PCAs
and
minor­
use
crops.
Instead
it
will
use
a
default
PCA
that
reflects
the
total
agricultural
land
in
an
8­
digit
Hydrologic
Unit
Code
(
HUC)
.
The
PCA
values
used
in
this
assessment
are
listed
in
Appendix
VII.

17
The
OPP
guidance
document
provides
information
on
when
and
how
to
apply
the
PCA
to
model
estimates,
describes
the
methods
used
to
derive
the
PCA,
discusses
some
of
the
assumptions
and
limitations
with
the
process,
and
spells
out
the
next
steps
in
expanding
the
PCA
implementation
beyond
the
initial
crops.
Instructions
for
using
the
index
reservoir
and
PCA
are
provided
below.
Discussion
on
some
of
the
assumptions
and
limitations
for
both
the
PCA
and
Index
Reservoir
are
included
in
the
Reporting
section.
One
should
note
that
there
is
an
entry
for
 
All
Agricultural
Land
 
in
Appendix
VII.
.
This
is
a
default
value
to
use
for
crops
for
which
no
specific
PCA
is
available.
It
represents
the
largest
amount
of
land
in
agricultural
production
in
any
8­
digit
hydrologic
unit
code
(
HUC)
watershed
in
the
continental
United
States.

The
unadjusted
EDWC
(
PRZM/
EXAMS
output)
is
multiplied
by
the
appropriate
PCA
for
that
crop
to
obtain
the
final
estimated
drinking
water
concentration
(
EDWC)
.
Note
that
if
Tier
2
modeling
is
done
for
an
area
other
than
the
standard
scenario,
the
PCA
would
still
be
applied,
since
it
represents
the
maximum
percent
crop
area
for
that
particular
crop.
(
As
regional
modeling
efforts
are
expanded,
regional
PCAs
could
be
developed
in
the
future.
)
As
an
example,
for
a
pesticide
used
only
on
cotton,
the
PRZM/
EXAMS
estimated
environmental
concentrations
would
be
multiplied
by
0.20.
This
factor
would
be
applied
to
the
standard
PRZM/
EXAMS
scenario
for
cotton
or
any
non­
standard
cotton
scenario
until
such
time
as
regional
PCAs
are
developed.

When
multiple
crops
occur
in
the
watershed,
the
co­
occurrence
of
these
crops
needs
to
be
considered.
The
PCA
approach
assumes
that
the
adjustment
factor
represents
the
maximum
potential
percentage
of
a
watershed
that
could
be
planted
to
a
crop.
If,
for
example,
a
pesticide
is
only
used
on
cotton,
then
the
assumption
that
no
more
than
20%
of
the
watershed
(
at
the
current
HUC
scale
used)
would
be
planted
to
the
crop
is
likely
to
hold
true.

The
Index
Reservoir
(
IR)
:
IR
is
intended
as
a
drop­
in
replacement
for
the
standard
pond
for
use
in
drinking
water
exposure
assessment.
It
is
used
in
a
manner
similar
to
the
standard
pond,
except
that
flow
rates
have
been
modified
to
reflect
local
weather
conditions.
The
PRZM
and
EXAMS
input
files
for
the
standard
pond
and
index
reservoir
are
in
Appendix
IX.
This
guidance
results
from
a
July,
1998
presentation
to
the
FIFRA
Science
Advisory
Panel.
The
materials
for
that
presentation
are
at:
http:
/
/
www.
epa.
gov/
scipoly/
sap/
1998/
index.
htm
Barley,
cotton,
potatoes,
tobacco,
and
spring
were
considered
because
they
represent
significant
uses,
maximum
application
rates,
and
are
grown
in
vulnerable
regions
of
the
United
States.
For
the
PRZM,
the
input
files
for
each
IR
scenario
are
essentially
the
same
as
its
farm
pond
scenario.
Three
parameters
in
the
PRZM
input
file
require
modification,
AFIELD,
HL,
and
DRFT.
These
changes
are
shown
in
Appendix
VIII.

The
estimated
drinking
water
concentrations
using
the
Index
Reservoir
(
IR)
and
PCA
(
PCA)
concepts
for
the
same
scenarios
used
for
ecological
exposure
assessments
were
evaluated
(
Tables
8a
and
8b)
.
The
long
term
mean
of
the
parent
disulfoton
concentration
in
the
Index
Reservoir
and
by
PCA
ranged
from
0.23
to
1.31
µ
g/
L
for
cotton
and
tobacco,
respectively.
The
1­
in­
10
year
estimated
annual
mean
concentration
ranged
from
0.43
to
2.77
µ
g/
L
for
cotton
and
tobacco,
respectively.
The
peak
1­
in­
10
year
estimated
drinking
water
concentration
for
parent
18
disulfoton
ranged
from
7.13
to
44.20
µ
g/
L.

The
Tier
II
modeling
results
from
PRZM/
EXAMS
fall
within
the
range
of
concentrations
for
surface
water
reported
in
the
STORET
database
(
0.0
to
100
µ
g/
L,
96
percent
of
8137
samples
were
reported
as
less
than
16
µ
g/
L)
,
a
Virginia
monitoring
study
(
0.37
to
6.11
µ
g/
L)
and
NAWQA
(
0.010
to
0.060
µ
g/
L)
.
But
because
some
of
the
data
in
STORET
have
a
high
degree
of
uncertainty
because
many
samples
were
only
listed
as
 
actual
value
is
known
to
less
than
given
value
 
,
the
maximum
concentration
of
samples
was
not
always
known
(
see
Appendix
III)
.
The
modeled
concentration
estimates
are
generally
greater
than
those
seen
in
the
monitoring
data.
The
modeling
results
therefore
cannot
be
confirmed
by
the
monitoring
data.

Because
the
degradates
of
disulfoton
(
including
oxygen
analogs)
:
sulfoxide
and
sulfone
are
also
toxic,
the
EECs
of
the
total
disulfoton
residue
(
TDR)
in
the
index
reservoirs
was
also
considered.
The
long
term
mean
of
the
total
disulfoton
residues
(
TDR)
in
the
Index
Reservoir
and
by
PCA
ranged
from
2.55
to
10.42
µ
g/
L
for
cotton
and
potatoes,
respectively.
The
1­
in­
10
year
estimated
annual
mean
TDR
concentrations
in
the
IR
ranged
from
5.10
to
16.72
µ
g/
L
for
cotton
and
potatoes,
respectively.
The
peak
1­
in­
10
year
estimated
TDR
concentrations
in
the
IR
ranged
from
20.83
to
104.92
µ
g/
L.
There
are
no
monitoring
data
to
evaluate
these
concentration
estimates
from
PRZM/
EXAMS
modeling.

Uncertainty
surrounds
these
estimates
because
the
sites
selected
for
modeling
represent
sites
thought
to
be
representative
of
vulnerable
sites.
Additionally,
the
IR
was
generic
(
to
each
scenario)
and
data
to
fully
understand
of
the
fate
of
disulfoton
and
disulfoton
residues
is
not
available.
Evidence
suggests
that
the
concentrations
will
not
be
as
high
as
suggest
by
the
modeled
estimates.
The
PCA
values
have
been
estimated
by
OPP
for
spring
wheat
(
0.56)
and
cotton
(
0.20)
.
The
default
for
value
for
all
agricultural
land
of
0.87
was
used
for
the
barley,
potatoes,
and
tobacco
scenarios.
Better
estimates
of
the
PCA
for
these
crops
would
reduce
the
uncertainty
associated
with
the
estimated
drinking
water
concentrations.

19
Table
8a.
Tier
II
Upper
Tenth
Percentile
EECs
for
Disulfoton
Parent
Used
on
barley,
cotton,
potatoes,

tobacco,
and
spring
wheat
for
several
application
(
Label
maximum)
rates
and
management
scenarios
estimated
using
PRZM3/
EXAMS
in
Index
Reservoir
with
Percent
Crop
Area.
Mean
of
Annual
Means
(
µ
g/
L)
0.95
0.51
0.23
1.05
0.94
1.31
0.86
0.
38
Concentration
(
µ
g/
L)

(
1­
in­
10
annual
yearly
maximum
value)
Annual
Avg.
1.61
1.22
0.43
1.30
1.09
2.77
2.38
0.
48
90­
Day
Avg.
6.09
4.16
1.61
5.22
4.38
11.14
9.62
1.
79
60­
Day
Avg.
7.69
5.59
2.32
7.53
6.19
16.23
14.09
2.
41
21­
Day
Avg.
11.67
9.82
3.86
12.73
9.59
30.14
26.56
3.
88
96­
Hour
Avg.
14.18
13.57
6.24
17.17
11.77
40.39
35.24
5.
76
Peak
15.51
14.88
7.13
18.83
13.09
44.20
38.57
6.
32
Disulfoton
Application
Rate
/
Number
of
Apps
/
Interval
/
Incorp.

Depth
/
method
1
lb.
ai/
A
/
#
/
days
/
inches
1.0
/
2/
21/
0/
f
0.83/
2/
21/
0/
s
(
granular)

1.
0
/
3/
21/
0/
s
4.0
/
2/
14/
2.5/
s
1.0/
3/
14/
0/
f
4.0/
1/
0/
2.5/
s
(
granular)

4.0/
1/
0/
2.5/
s
0.75/
2/
30/
0/
f
Crop
2
Barley
Barley
Cotton
Potatoes
Potatoes
Tobacco
Tobacco
Spr.
Wheat
1
Method
of
application:
f
=
foliar
and
s
=
soil
2
PCA
Barley,
Potatoes,
Tobacco
=
0.87
(
default
value
for
all
ag.
land)
;
cotton
=
0.20,
Spring
wheat
=
0.56
20
Table
8b.
Tier
II
Upper
Tenth
Percentile
EECs
for
Total
Disulfoton
Residues
Used
on
barley,
cotton,

potatoes,
tobacco,
and
spring
wheat
for
several
application
(
Label
maximum)
rates
and
management
scenarios
estimated
using
PRZM3/
EXAMS
with
Index
Reservoir
and
Percent
Crop
Area.
Mean
of
Annual
Means
(
µ
g/
L)
4.21
5.42
2.55
10.42
9.49
8.70
8.01
3.68
Concentration
(
µ
g/
L)

(
1­
in­
10
annual
yearly
maximum
value)
Annual
Avg.
7.62
10.01
5.10
13.44
16.72
16.25
15.99
4.88
90­
Day
Avg.
18.04
26.30
12.82
26.91
25.85
53.36
5347.00
11.03
60­
Day
Avg.
22.33
27.99
14.10
30.06
27.87
66.65
63.97
12.24
21­
Day
Avg.
29.47
32.50
17.91
32.41
30.21
85.43
85.04
13.84
96­
Hour
Avg.
33.30
37.64
20.22
35.64
33.56
100.31
99.44
15.09
Peak
34.53
39.05
20.83
36.57
34.37
104.92
103.79
15.48
Disulfoton
Application
Rate
/
Numberof
Apps
/
Interval
/
Incorp.

Depth
/
method
1
lb.
ai/
A
/
#
/
days
/
inches
1.0
/
2/
21/
0/
f
0.83/
2/
21/
0/
s
(
granular)

1.
0
/
3/
21/
0/
s
4.0
/
2/
14/
2.5/
s
1.0/
3/
14/
0/
f
4.0/
1/
0/
2.5/
s
(
granular)

4.0/
1/
0/
2.5/
s
0.75/
2/
30/
0/
f
Crop
2
Barley
Barley
Cotton
Potatoes
Potatoes
Tobacco
Tobacco
Spr.
Wheat
1
Method
of
application:
f
=
foliar
and
s
=
soil
2
PCA
values
for
Barley,
Potatoes,
Tobacco
=
0.87
(
default
value)
;
cotton
=
0.20,
Spring
wheat
=
0.56
21
b.
Ground
water
For
this
assessment,
the
maximum
rate
and
number
of
disulfoton
applications
were
used,
while
assuming
conservative
environmental
properties
(
90
percent
upper
confidence
bound
on
the
mean
aerobic
soil
half­
life
of
6.12
days
and
an
average
Koc
value
of
551
mL/
g)
.
The
maximum
disulfoton
concentration
predicted
in
ground
water
by
the
SCI­
GROW
model
(
using
the
maximum
rate
4
lb.
a.
i.
/
ac
and
2
applications
­
potatoes)
was
0.05
µ
g/
L.
The
maximum
total
disulfoton
residue
concentration
predicted
in
ground
water
by
the
SCI­
GROW
model
for
the
same
scenario
is
3.19
µ
g/
L
(
except
90
percent
upper
bound
on
mean
half­
life
of
total
residues
is
259.6
days)
.

It
should
be
noted
that
all
the
detections
of
disulfoton
residues
in
ground
water
in
Wisconsin
(
range
4.0
to
100.0
µ
g/
L)
and
some
detections
in
Virginia
(
range
0.04
­
2.87
µ
g/
L)
exceeded
the
concentrations
predicted
by
SCI­
GROW
(
0.05
µ
g/
L)
.
Although
SCI­
GROW,
which
is
thought
to
be
conservative
(
e.
g.
,
a
vulnerable
site)
,
is
based
on
a
regression
relationship
between
monitoring
data
(
detected
concentrations)
and
pesticide
fate
chemistry
at
vulnerable
sites,
SCI
­
GROW
does
not
account
for
preferential
flow,
point­
source
contamination,
pesticide
spills,
misuses,
or
pesticide
storage
sites.
Many
unknowns,
data
limitations,
such
as
on­
site
variability,
are
also
present
in
the
prospective
ground­
water
monitoring
studies
which
were
not
included
when
developing
SCI­
GROW.
The
difference
between
monitoring
and
modeling
is
discussed
further
in
the
next
section.

vi.
Disulfoton
Monitoring
Data
Ground
Water:
Monitoring
Studies
With
No
Disulfoton
Residues
Detections
in
Ground
Water:
The
Pesticides
in
Ground
Water
Data
Base
(
USEPA,
1992)
summarizes
the
results
of
a
number
of
ground­
water
monitoring
studies
conducted
which
included
disulfoton
(
and
rarely
the
disulfoton
degradates
D.
sulfone
and
D.
sulfoxide)
.
Monitoring,
with
no
detections
(
limits
of
detections
ranged
from
0.01
to
6.0
µ
g/
L)
,
has
occurred
in
the
following
states
(
number
of
wells)
:
AL
(
10)
,
CA
(
974)
,
GA
(
76)
,
HI
(
5)
,
IN
(
161)
,
ME
(
71)
,
MS
(
120)
,
MN
(
754)
,
OK
(
1)
,
OR
(
70)
,
and
TX
(
188)
.
The
range
of
detection
limits,
especially
the
high
ones
(
e.
g.
,
6
µ
g/
L)
reduce
the
certainty
of
these
data.

One
hundred
twenty
wells
were
analyzed
in
MS
for
disulfoton
degradates
sulfone
and
sulfoxide
and
188
wells
were
analyzed
in
TX
for
sulfone.
Limits
of
detection
were
3.80
and
1.90
µ
g/
L
for
the
sulfone
and
sulfoxide
degrade,
respectively,
in
MS.
There
were
no
degradates
reported
in
these
samples.

North
Carolina:
The
North
Carolina
Departments
of
Agriculture
(
NCDA)
and
Environment,
Health,
and
Natural
Resources
(
DEHNR)
conducted
a
cooperative
study
under
the
direction
of
the
North
Carolina
Pesticide
Board
(
NCIWP,
1997)
.
The
purpose
of
the
statewide
study
was
to
determine
if
the
labeled
uses
of
pesticide
products
were
impacting
the
ground
water
resources
in
North
Carolina.
The
study
was
conducted
in
two
phases.
In
phase
one,
55
wells
in
the
DEHNR
Ground
Water
22
Section'
s
ambient
monitoring
network
representing
the
major
drinking
water
aquifers
of
the
state
were
sampled
at
least
twice
and
analyzed
for
selected
pesticides.
In
phase
two,
97
cooperator
monitoring
wells
were
installed
and
subsequently
sampled
at
least
twice
in
36
counties
across
the
North
Carolina.
Sites
for
the
cooperator
monitoring
wells
were
chosen
based
on
an
evaluation
of
the
vulnerability
of
ground
water
to
risk
of
contamination
from
the
use
of
pesticides.

Monitoring
wells
were
located
adjacent
to
and
down­
gradient
from
areas
where
pesticides
were
reported
to
have
been
applied
(
within
300
feet)
during
the
previous
five
years.
Wells
were
constructed
so
that
the
shallowest
ground
water
could
be
collected
for
analysis.
The
objective
of
these
criteria
was
to
use
a
scientific
method
for
determining
monitoring
well
locations
so
that
the
results
could
be
used
as
an
early
indication
of
the
potential
for
problems
associated
with
pesticides
leaching
to
ground
water.
Disulfoton
residues
were
monitored
for
in
five
North
Carolina
counties,
Alleghany,
Ash,
Beaufort,
Madison,
and
Robeson.
Seven
wells
were
located
in
Christmas
Tree
growing
areas,
one
in
wheat
growing
county,
and
two
in
tobacco
areas.
The
study
authors
make
the
following
statement,
"
Results
cannot
be
interpreted
as
representing
the
quality
of
ground
water
near
pesticide
use
areas
statewide
because
the
study
methods
targeted
areas
of
highly
vulnerable
ground
water"
.

There
were
no
detections
of
disulfoton,
disulfoton
sulfoxide,
and
disulfoton
in
the
ground­
water
monitoring
study
conducted
in
North
Carolina.
Efforts
were
made
to
place
the
wells
in
vulnerable
areas
where
the
pesticide
use
was
known,
so
that
the
pesticide
analyzed
for
would
reflect
the
use
history
around
the
well.
Limitations
of
the
study
include
that
sites
were
sampled
only
twice
and
the
limits
of
detections
were
high
(
e.
g.
,
>
1.0
µ
g/
L)
for
some
of
disulfoton
analytes.
Uncertainties
associated
with
the
study
include
whether
two
samples
from
eight
wells
are
adequate
to
represent
the
ground­
water
concentrations
of
disulfoton
residues,
did
DRASTIC
correctly
identify
a
site'
s
vulnerability,
and
were
the
wells
placed
down­
gradient
of
the
use
areas.

The
study
used
tools
and
information
available
at
the
time
of
the
study
to
identify
vulnerable
locations
for
well
placement.
This
included
statewide
agricultural
data
from
the
N.
C.
Agricultural
Statistics
which
were
used
to
identify
crop
growing
areas,
the
USEPA
DRASTIC
method
(
Aller
et
al.
,
1987)
was
used
to
locate
the
most
vulnerable
locations
in
the
target
crop
growing
areas,
and
local
county
agents
of
the
USDA
Natural
Resources
Conservation
Service
(
NRCS)
helped
identify
cooperators­
farmers
for
placement
of
wells.
The
Pesticide
Study
staff
and
county
agents
also
met
with
the
cooperators
to
obtain
pesticide
use
information.
Other
studies
have
shown
that
DRASTIC
is
not
as
good
a
method
to
identify
vulnerable
areas
as
hoped.
The
study
appeared
to
QA/
QC
practices.

Monitoring
Studies
With
Disulfoton
Detections
in
Ground
Water:
Two
of
the
studies
cited
in
the
PGWDB
(
USEPA,
1992)
report
the
detection
of
disulfoton
residues
in
ground
water.
The
disulfoton
detections
in
ground
water
in
occurred
studies
conducted
by
Virginia
Polytechnic
Institute
and
State
University
(
VPI&
SU,
Mosaghimi,
1989)
in
Virginia
where
disulfoton
concentrations
ranged
from
0.04
to
2.87
µ
g/
L
and
in
a
Wisconsin
Department
of
Natural
Resources
study
in
Wisconsin
(
WDNR,
after
Barton,
1982)
where
concentrations
ranged
from
4.00
to
100.00
µ
g/
L.
Of
specific
are
the
disulfoton
concentrations
of
parent
disulfoton
reported
in
these
studies
(
VA
and
WI)
that
exceeded
the
estimate
of
0.05
µ
g/
L
obtained
from
EFED'
s
23
SCI­
GROW
(
ground­
water
screening
model)
model.

Virginia:
A
monitoring
study
was
conducted
to
evaluate
the
effectiveness
of
Best
Management
Practices
(
BMP)
in
a
3616­
acre
watershed
in
the
Nomini
Creek
Watershed,
Westmoreland
County,
Virginia.
Approximately
half
of
the
watershed
is
in
agriculture
and
the
other
half
is
forested.
The
major
focus
of
this
study
was
surface­
water
quality
rather
than
ground­
water
quality.
However,
in
addition
to
the
surface­
water
monitoring,
twelve
wells
were
analyzed
for
pesticides,
including
disulfoton.

Samples
were
taken
in
1985
and
1986
from
four
household
wells
in
the
Nomini
Creek
Watershed
(
NCW)
.
Water
samples
from
these
wells
were
analyzed
for
24
pesticides.
Detectable
levels
of
(
not
specified)
pesticides
were
found
in
all
four
wells
at
concentrations
below
the
respective
MCL.
One
of
these
four
household
wells
consistently
had
higher
pesticide
levels
than
the
other
wells.
The
study
authors
suggested
that
this
household
well
was
not
"
sufficiently
protected
and
was
contaminated
by
surface
runoff
from
adjacent
land"
.

Based
upon
these
results
of
the
four
household
wells
sampled,
eight
pairs
of
ground­
water
monitoring
wells
(
39
to
54
feet
deep)
were
installed
at
eight
sites
in
the
NCW
and
sampled
approximately
monthly
from
June
1986
through
December
1990.
Information
concerning
farming
practices
in
the
watershed
was
obtained
from
farmer
interviews
and
questionnaires.
Disulfoton
residues
(
0.04,
0.10,
0.10,
0.13,
0.16,
and
2.87
µ
g/
L)
were
detected
in
wells
at
five
of
the
eight
monitoring
sites
during
the
period
11/
86
to
12/
90.
The
average
detection
was
0.57
µ
g/
L
(
standard
deviation
=
1.13
µ
g/
L)
.
Since
the
study
authors
present
no
information
or
discussion
questioning
the
pesticide
detections
which
occurred
in
the
monitoring
wells
(
notably
site
GN3,
the
well
with
2.87
µ
g/
L)
,
the
disulfoton
detections
found
in
the
monitoring
wells
should
be
included
in
this
assessment.

Table
9.
Summary
of
Disulfoton
Detections
in
ground
water
from
the
eight
ground­
water
monitoring
wells
in
Nomini
Creek
Watershed
(
Virginia)
,
during
1986
and
1987.

Sampling
Date
Well­
Site
Number
Concentration
(
g/
L)

11/
5/
86
GN3
2.87
11/
5/
86
GN6
0.04
3/
13/
87
GN4
0.10
8/
20/
87
GN1
0.13
8/
20/
87
GN2
0.16
8/
20/
87
GN3
0.10
24
The
study
was
conducted
under
a
Quality
Assurance/
Quality
Control
Plan.
Pesticides
were
determined
using
GLC
methods
with
an
EC
Ni63
detector.
The
study
reportedly
ran
until
1995
(
data
available
only
goes
through
1990)
.

Wisconsin:
Barton,
1982.
In
May
and
June
1982,
the
Wisconsin
Department
of
Natural
Resources
(
WDNR)
sent
twenty­
nine
water
samples
from
wells
in
the
Central
Sands
area
of
Wisconsin
to
the
EPA'
s
Office
of
Pesticide
Programs
for
pesticide
residue
analysis.
Samples
were
taken
from
one
municipal
well,
two
or
three
community
wells,
and
twenty­
five
home
wells;
all
of
which
were
sources
of
drinking
water.
Of
the
29
samples,
15
samples
were
reported
as
no
detects
whereas
14
samples
were
reported
disulfoton
detections.
Disulfoton
detections
ranged
from
4.00
to
100.00
µ
g/
L,
with
a
mean
(
samples
with
detections)
of
38.43
µ
g/
L
and
standard
deviation
of
31.56
µ
g/
L.
No
detection
limit
was
specified
for
disulfoton,
although
detections
as
low
as
1
µ
g/
L
are
reported
for
other
pesticide
residues
(
aldicarb,
and
aldicarb
sulfone,
dinoseb,
sencor,
linuron,
carbofuran,
and
Lasso/
Bravo)
.

Holden
(
1986)
wrote
that
the
WDNR
sampling
program
was
criticized
for
a
number
of
reasons
including
that
the
quality
assurance
and
quality
control
procedures
(
QA/
QC)
were
not
always
followed
during
some
stages
of
sampling
and
analysis
(
Holden,
1986)
.
Holden
(
1986)
further
indicates
that
"
Harkin
et
al.
(
1984)
noted
in
their
WIS
WRC
report
Pesticides
in
Groundwater
beneath
the
Central
Sand
Plain
of
Wisconsin
that
some
detections
of
pesticides
in
initial
screening
were
false
positives
and
were
not
supported
by
resampling
and
reanalysis
by
more
sensitive
analytical
methods.
"

Aldicarb
and
aldicarb
sulfone
were
also
found
in
this
study
and
in
follow
up
studies,
while
disulfoton
was
apparently
not
found
in
follow­
up
sampling.
Aldicarb
is
no
longer
registered
for
use
in
Wisconsin.

The
criticisms
of
the
WDNR
study
must,
however,
be
put
in
some
sort
of
perspective.
First,
a
study
that
did
not
follow
QA/
QC
criteria
does
not
and
should
not
automatically
mean
that
the
data
is
bad
or
wrong,
the
detections
may
be
correct
(
presence
and
magnitude)
.
Frequently
"
older"
monitoring
studies
often
had
problems
associated
with
them,
such
as
QA/
QC
problems,
limited
pesticide
usage
information,
and
no
knowledge
about
the
study
area'
s
hydrology.
Frequently,
studies
with
QA/
QC
programs
are
poorly
designed,
so
that
the
results
may
be
meaningless.

Pesticide
residues
not
being
found
in
follow­
up
sampling
may
be
the
result
of
dissipation
processes
and
should
not
be
used
to
discount
detections
in
earlier
samples.
The
environmental
fate
properties
and
site
hydrology
must
also
be
considered.
Because
ground
water
is
a
dynamic
system,
pesticides
may
be
present
at
one
sampling
event
and
not
at
another.
So
when
the
sample
is
collected,
in
relationship
to
pesticide
use
and
rainfall,
is
important.
All
that
can
be
said
is
that
residues
were
not
found
in
follow­
up
samples.
It
is
unknown
which
samples
were
re­
analyzed
with
more
sensitive
methods.

The
disulfoton
detections
in
the
Central
Sand
Plain
may
have
been
the
result
of
preferential
flow
and
transport
processes.
Literature
documents
preferential
flow
in
the
Central
Sand
Plain.
Thus,

25
disulfoton
residues
may
have
by­
passed
the
soil
matrix
and
gone
directly
to
ground
water
which
is
possibly
reflected
in
the
"
high"
level
of
the
detections.
Although
preferential
flow
is
currently
an
ongoing
area
of
research
and
much
remains
unknown,
it
is
known
that
preferential
flow
is
influenced
by
a
number
of
factors,
including
rainfall
amounts,
intensity,
and
frequency.
Disulfoton
generally
appears
to
be
not
very
persistent
under
aerobic
soil
conditions
and
therefore
may
also
not
be
very
persistent
in
aquifers
that
are
aerobic.
Therefore
it
may
have
also
been
missed
by
utilizing
a
predetermined
sampling
schedule
(
e.
g.
,
monthly)
.
Whereas
a
persistent
chemical,
such
as
aldicarb
and
aldicarb
sulfone,
will
be
found
at
greater
frequencies
and
be
less
dependent
upon
timing
of
sampling.
Disulfoton
usage
history
before
the
detections
and
prior
to
the
follow­
up
sampling
is
not
specified.

Surface
Water:
A
monitoring
study
was
conducted
to
evaluate
the
effectiveness
of
Best
Management
Practices
(
BMP)
in
a
3616­
acre
watershed
in
the
Nomini
Creek
Watershed,
Westmoreland
County,
Virginia.
Approximately
half
of
the
watershed
is
in
agriculture
and
the
other
half
is
forested.
The
major
focus
of
this
study
was
surface­
water
quality
rather
than
ground­
water
quality.
The
detections
of
parent
disulfoton
in
surface­
water
samples
(
0.037
to
6.11
µ
g/
L)
collected
(
Table
10)
in
the
Nomini
Creek
Watershed
study
fell
within
an
order
of
magnitude
with
the
estimated
environmental
concentrations
(
EECs)
obtained
from
the
PRZM/
EXAMS
models
for
parent
disulfoton
which
range
from
0.21
to
1.14
µ
g/
L
for
annual
mean
daily
concentrations
and
7.14
to
26.75
µ
g/
L
for
peak
daily
values.

Table
10.
Disulfoton
detections
in
Surface
Water
samples
collected
in
the
Nomini
Creek
Watershed
(
Virginia)
,
during
1986.

Sample
date
Site
Number:
Sample
#
Concentration
(
g/
L)

8/
18/
86
QN1:
1
(
9:
13
am)
6.11
8/
18/
86
QN1:
2
(
12:
25
pm)
0.37
9/
28/
86
QN2:
(
only
1
sample)
1.62
NAWQA
:
Disulfoton
residues
have
been
detected
in
surface
water
at
a
low
frequency
in
the
USGS
NAWQA
study.
The
percentage
of
detections
with
disulfoton
concentrations
>
0.01
µ
g/
L
for
all
samples,
agricultural
streams,
urban
streams
were
0.27%
,
0.20,
and
0.61%
,
respectively.
The
corresponding
maximum
concentrations
were
0.060,
0.035,
and
0.037
µ
g/
L.
Disulfoton
has
not
been
detected
in
ground
water
in
the
NAWQA
study.
Although
pesticide
usage
data
is
collected
for
the
different
NAWQA
study
units,
the
studies
are
not
targeted,
specifically
for
disulfoton.

26
STORET
:
About
50
percent
of
the
well
samples
reported
in
STORET
had
low
levels
(
<
1
µ
g/
L)
of
disulfoton
residues.
However,
there
were
indications
of
some
high
concentrations
(
the
other
50%
were
reported
as
<
250
µ
g/
L)
,
which
may
be
a
reflection
of
how
the
data
were
reported
as
the
disulfoton
concentrations
in
the
monitoring
were
not
always
known.
This
is
because
the
detection
limit
was
extremely
high
or
not
specified,
and/
or
the
limit
of
quantification
was
not
stated
or
extremely
high.
Disulfoton
concentrations
were
simply
given
as
less
than
a
value.
Therefore,
considerable
uncertainty
exists
with
respect
to
the
STORET
monitoring
data.

Limitations
of
Monitoring
Data
The
interpretation
of
the
monitoring
data
is
limited
by
the
lack
of
correlation
between
sampling
dates
and
the
use
patterns
of
the
pesticide
within
the
study
 
s
drainage
basin.
Additionally,
the
sample
locations
were
not
associated
with
actual
drinking
water
intakes
for
surface
water
nor
were
the
monitored
wells
associated
with
known
ground
water
drinking
water
sources.
Also,
due
to
many
different
analytical
detection
limits,
no
specified
detection
limits,
or
extremely
high
detection
limits,
a
detailed
interpretation
of
the
monitoring
data
is
not
always
possible.
Limitations
for
the
monitoring
studies
include
the
use
of
different
limits
of
detection
between
studies,
lack
of
information
concerning
disulfoton
use
around
sampling
sites,
and
lack
of
data
concerning
the
hydro
geology
of
the
study
sites.
The
spatial
and
temporal
relationship
between
disulfoton
use,
rainfall/
runoff
events
and
the
location
and
time
of
sampling
cannot
often
be
adequately
determined.
Thus,
it
is
not
always
possible
to
judge
the
significance
of
the
level
or
the
lack
of
detections.

Although
no
assessment
can
be
made
for
degradates
due
to
lack
of
data,
limited
data
suggests
that
the
degradates
are
more
persistent
(
>
200
days)
than
disulfoton,
suggesting
their
presence
in
water
for
a
longer
period
of
time
than
the
parent.
The
degradates
also
appear
to
be
more
mobile
than
the
parent
compound.

vii.
Limitations
of
this
Modeling
Analysis
There
are
number
of
factors
which
limit
the
accuracy
and
precision
of
this
modeling
analysis
including
the
selection
of
the
high­
end
exposure
scenarios
and
maximum
number
of
applications
and
rates,
the
quality
of
the
data,
the
ability
of
the
model
to
represent
the
real
world,
and
the
number
of
years
that
were
modeled.
There
are
additional
limitations
on
the
use
of
these
numbers
as
an
estimate
of
drinking
water
exposure.
Individual
degradation/
metabolism
products
were
also
not
considered
due
to
lack
of
data.
Another
major
uncertainty
in
the
current
EXAMS
simulations
is
that
the
aquatic
degradation
rate
used
an
estimated
rate
due
to
lack
of
data.
Direct
aquatic
photolysis
was
also
included.
The
total
disulfoton
residue
decline
rate
was
estimated
from
data,
but
Kocs
and
hydrolysis
rates
for
D.
sulfoxide
and
sulfone
were
not
known
and
assumed
to
be
equal
to
those
of
parent
disulfoton.
These
limitations
influence
the
estimates
of
pesticides
transported
off
the
field
(
loading
files)
to
the
pond,
plus
the
degradation
once
in
the
pond.

Spray
is
determined
by
method
of
pesticide
application,
and
is
assumed
to
be
0%
percent
when
applied
as
broadcast
(
granular)
or
in­
furrow,
5%
for
ground
spray,
and
15%
for
aerial
spray
for
27
the
farm
pond,
and
6.4%
ground
and
16.4%
aerial
spray
for
the
Index
Reservoir
scenario
(
Jones
et
al.
,
2000)
.

Tier
II
scenarios
are
also
ones
that
are
likely
to
produce
high
concentrations
in
aquatic
environments.
The
scenarios
were
intended
to
represent
sites
that
actually
exist
and
are
likely
to
be
treated
with
a
pesticide.
These
sites
should
be
extreme
enough
to
provide
a
conservative
estimates
of
the
EEC,
but
not
so
extreme
that
the
model
cannot
properly
simulate
the
fate
and
transport
processes
at
the
site.
The
EECs
in
this
analysis
are
accurate
only
to
the
extent
that
the
sites
represent
the
hypothetical
high
exposure
sites.
The
most
limiting
aspect
of
the
site
selection
is
the
use
of
the
 
standard
pond
 
which
has
no
outlet.
.
It
also
should
be
noted
that
the
standard
pond
scenario
used
here
would
be
expected
to
generate
higher
EECs
than
most
water
bodies,
although,
some
water
bodies
would
likely
have
higher
concentrations
(
e.
g.
,
a
shallow
water
bodies
near
agriculture
fields
that
receive
direct
run­
off
from
the
treated
field)
.

The
quality
of
the
analysis
is
also
directly
related
to
the
quality
of
the
chemical
and
fate
parameters
available
for
disulfoton.
Acceptable
data
are
available,
but
rather
limited.
Data
were
not
available
for
degradates
and
the
aquatic
aerobic
metabolism
rate
was
not
known,
but
estimated.
Degradates
with
greater
persistence
and
greater
mobility
would
be
expected
to
have
a
higher
likelihood
of
leaching
to
ground
water,
with
greater
concentrations
in
surface
water.
The
measured
aerobic
soil
metabolism
data
is
limited,
but
has
sufficient
sample
size
to
establish
an
upper
90%
confidence
bound
on
the
mean
of
half­
lives
for
the
three
aerobic
soils
tested
in
the
laboratory
(
and
submitted
to
EFED)
and
reported
in
the
EFED
One­
liner
Database
(
MRIDs
40042201,
41585101,
43800101)
.
The
use
of
the
90%
­
upper
bound
value
may
be
sufficient
to
capture
the
probable
estimated
environmental
concentration
when
limited
data
are
available.
PRZM
assumes
pesticide
decline
follows
first­
order
kinetics.
As
discussed
in
the
aerobic
soil
metabolism
section,
disulfoton
doesn'
t
entirely
follow
first­
order
kinetics.

The
models
themselves
represent
a
limitation
on
the
analysis
quality.
These
models
were
not
specifically
developed
to
estimate
environmental
exposure
in
drinking
water
so
they
may
have
limitations
in
their
ability
to
estimate
drinking
water
concentrations.
Aerial
spray
drift
reaching
the
pond
is
estimated
from
Spray
Drift
Task
Force
(
SDTF)
preliminary
data
to
be
15
percent
of
the
application
rate
and
for
ground
spray
it
is
1
percent
of
the
application
rate.
No
drift
was
assumed
for
broadcast
or
in­
furrow
applications.
Another
limitation
is
the
lack
of
field
data
to
validate
the
predicted
pesticide
run­
off.
Although,
several
of
the
algorithms
(
volume
of
run­
off
water,
eroded
sediment
mass)
are
somewhat
validated
and
understood,
the
estimates
of
pesticide
transport
by
PRZM3
has
not
yet
been
fully
validated
Other
limitations
of
PRZM
are
the
inability
to
handle
within
site
variation
(
spatial
variability)
,
crop
growth,
and
the
overly
simple
water
balance.
Another
limitation
is
that
20
to
40
years
of
weather
data
were
available
for
the
analysis.
Consequently
there
is
a
1
in
20,
27,
36,
or
40
chance
that
the
true
10%
exceedence
EECs
are
larger
than
the
maximum
EEC
in
the
analysis.
If
the
number
of
years
of
weather
data
were
increased,
it
would
increase
the
level
of
confidence
that
the
estimated
value
for
the
10%
exceedence
EEC
was
close
to
the
true
value.

EXAMS
is
primarily
limited
because
it
is
a
steady­
state
model
and
cannot
accurately
characterize
the
dynamic
nature
of
water
flow.
A
model
with
dynamic
hydrology
would
more
28
accurately
reflect
concentration
changes
due
pond
overflow
and
evaporation.
Thus,
the
estimates
derived
from
the
current
model
simulates
a
pond
having
no­
outlets,
flowing
water,
or
turnover.
Another
major
limitation
in
the
current
EXAMS
simulations
is
that
the
aquatic
(
microbial)
and
abiotic
degradation
pathways
were
adequately
considered.
The
binding
potential
of
the
degradates
is
not
known
and
was
not
considered.

Another
important
limitation
of
the
Tier
II
EECs
for
drinking
water
exposure
estimates
is
the
use
of
a
single
10­
hectare
drainage
basin
with
a
1­
hectare
pond.
It
is
unlikely
that
this
small
system
accurately
represents
the
dynamics
in
a
watershed
large
enough
to
support
a
drinking
water
utility.
It
is
unlikely
that
an
entire
basin,
with
an
adequate
size
to
support
a
drinking
water
utility
would
be
planted
completely
in
a
single
crop
or
be
represented
by
scenario
being
modeled.
The
pesticides
would
more
likely
be
applied
over
several
days
to
weeks
rather
than
on
a
single
day.
This
would
reduce
the
magnitude
of
the
conservative
concentration
peaks,
but
also
make
them
broader,
reducing
the
acute
exposure,
but
perhaps
increasing
the
chronic
exposure.

3.
Ecological
Effects
Hazard
Assessment
A.
Toxicity
to
Terrestrial
Animals
i.
Birds,
Acute
and
Subacute
An
acute
oral
toxicity
study
using
the
technical
grade
of
the
active
ingredient
is
required
to
establish
the
toxicity
of
a
pesticide
to
birds.
The
preferred
test
species
is
either
mallard
duck
or
bobwhite
quail.
Results
of
this
test
are
tabulated
below.
Acute
oral
testing
was
also
performed
with
the
15G
formulation
of
disulfoton.
Additionally,
acute
oral
testing
was
required
for
the
two
major
degradation
products
of
disulfoton,
disulfoton
sulfone
and
disulfoton
sulfoxide,
due
to
their
relative
persistence.
These
test
results
are
as
follows:

29
Table
11.
Avian
Acute
Oral
Toxicity
Species
%
ai
LD50
(
mg/
kg)
Toxicity
Category
MRID
No.
Author/
Year
Study
Classification
Mallard
(
Anas
platyrhynchos)
97
6.54
very
highly
toxic
00160000
1984/
Hudson
supplemental
Northern
bobwhite
quail
(
Colinus
virginianus)
technical
12.0
highly
toxic
EDODIS00
Hill
core
Northern
bobwhite
quail
(
Colinus
virginianus
technical
28
highly
toxic
0095655
1977
core
Northern
bobwhite
quail
(
Colinus
virginianus)
technical
31
highly
toxic
0095655
1977
core
Northern
bobwhite
quail
(
Colinus
virginianus)
98.7
39
highly
toxic
42585803
/
1992
core
Ring­
necked
pheasant
(
Phasianus
colchicus)
technical
11.9
highly
toxic
00160000
1987/
Hudson
core
Red­
winged
blackbird
(
Agelaius
phoeniceus
)
technical
3.2
very
highly
toxic
1987
supplemental
Northern
bobwhite
quail
(
Colinus
virginianus)
15G
220
moderately
toxic
25525
1969
core
Northern
bobwhite
quail
(
Colinus
virginianus)
15G
97
moderately
toxic
25525
1969
core
Northern
bobwhite
quail
(
Colinus
virginianus)
15G
14.5
highly
toxic
0095655
1984
supplemental
Northern
bobwhite
quail
(
Colinus
virginianus)
15G
29
highly
toxic
EDODIS00
1984
supplemental
Northern
bobwhite
quail
(
Colinus
virginianus)
sulfone
metabolite
87.4
18
highly
toxic
42585103
1992
core
Northern
bobwhite
quail
(
Colinus
virginianus)
sulfoxide
metabolite
85.3
9.2
very
highly
toxic
42585102
1992
core
30
These
results
indicate
that
disulfoton
is
highly
toxic
to
very
highly
toxic
to
avian
species
on
an
acute
oral
basis.
The
guideline
requirement
(
71­
1)
is
fulfilled
(
MRID
#
42585803)
.
Additionally,
the
two
major
metabolites
of
disulfoton,
disulfoton
sulfone
and
disulfoton
sulfoxide,
are
highly
toxic
and
very
highly
toxic,
respectively.
Guideline
71­
1
is
fulfilled
for
the
two
major
degradates
of
disulfoton
(
42585103
and
42585102)
.

Two
subacute
dietary
studies
using
the
technical
grade
of
the
active
ingredient
are
required
to
establish
the
toxicity
of
a
pesticide
to
birds.
The
preferred
test
species
are
mallard
duck
(
a
waterfowl)
and
bobwhite
quail
(
an
upland
gamebird)
.
Subacute
dietary
testing
on
the
two
major
metabolites
of
disulfoton,
disulfoton
sulfone
and
disulfoton
sulfoxide,
were
also
required,
due
to
the
relative
persistence
of
these
degradates.
Results
of
all
avian
subacute
dietary
tests
are
as
follows:

Table
12.
Avian
Subacute
Dietary
Toxicity
Species
%
ai
LC50
(
ppm)
Toxicity
Category
MRID
No.
Author/
Year
Study
Classification
Northern
bobwhite
quail
(
Colinus
virginianus)
technical
544
moderately
toxic
0094233
Lamb/
1973
core
Mallard
duck
(
Anas
platyrhynchos)
technical
510
moderately
toxic
0034769
Hill/
1975
core
Japanese
quail
(
Coturnix
japonica)
technical
333
highly
toxic
0034769
Hill/
1975
supplemental
Mallard
duck
(
Anas
platyrhynchos)
sulfone
metabolite
87.4
622
moderately
toxic
42585101
1992
core
Northern
bobwhite
quail
(
Colinus
virginianus)
sulfone
metabolite
87.4
558
moderately
toxic
42585106
1992
core
Mallard
duck
(
Anas
platyrhynchos)
sulfoxide
metabolite
85.3
823
moderately
toxic
42585104
1992
core
Northern
bobwhite
quail
(
Colinus
virginianus)
sulfoxide
metabolite
85.3
456
highly
toxic
42585105
1992
core
These
results
indicate
that
disulfoton
is
highly
toxic
to
avian
species
on
a
subacute
dietary
basis.
The
guideline
requirement
(
71­
2)
is
fulfilled
(
ACC
#
0094233
and
0034769)
.
Additionally,
the
major
metabolites
of
disulfoton,
disulfoton
sulfone
and
disulfoton
sulfoxide,
are
moderately
to
highly
toxic
to
avian
species
on
a
dietary
basis.
Guideline
71­
2
is
fulfilled
for
both
metabolites
(
MRID
#
42585101,
42585106,
42585104,
and
42585105)
.

31
ii.
Birds,
Chronic
Avian
reproduction
studies
using
the
technical
grade
of
the
active
ingredient
are
required
for
disulfoton
because
the
following
conditions
are
met:
(
1)
birds
may
be
subject
to
repeated
or
continuous
exposure
to
the
pesticide,
especially
preceding
or
during
the
breeding
season,
(
2)
the
pesticide
is
stored
or
accumulated
in
plant
or
animal
tissues,
and/
or,
(
4)
information
derived
from
mammalian
reproduction
studies
indicates
reproduction
in
terrestrial
vertebrates
may
be
adversely
affected
by
the
anticipated
use
of
the
product.
Disulfoton
meets
all
of
these
conditions.
The
preferred
test
species
are
mallard
duck
and
bobwhite
quail.
Results
of
these
tests
are
tabulated
below.

Table
13.
Avian
Reproductive
Toxicity
Species
%
ai
NOAEC/
LOAEC
(
ppm)
Endpoints
Affected
MRID
No.
Author/
Year
Study
Classification
Northern
bobwhite
quail
(
Colinus
virginianus)
98.7
37/
74
hatchling
body
weight
43032501
/
1993
core
Mallard
duck
(
Anas
platyrhynchos)
98.3
37/
80
adult
and
hatchling
body
weight
43032502
/
1993
core
There
was
a
statistically
significant
reduction
in
hatchling
body
weight
at
74
ppm
in
the
bobwhite
quail
study;
however,
there
were
no
significant
differences
in
hatchling
body
weights
by
day
14
post­
hatch.
No
other
effects
were
observed
in
this
study.

Adult
and
hatchling
body
weights
were
significantly
reduced
at
80
and
164
ppm
in
the
mallard
study,
and
body
weight
gain
in
adults
was
significantly
reduced
throughout
the
study
at
these
two
treatment
levels
as
well.
Other
effects
observed
at
the
164
ppm
level
were:
significantly
fewer
eggs
laid
per
hen,
reduced
eggshell
strength
and
thickness,
reduced
number
of
hatchlings
as
a
percent
of
viable
embryos,
reduced
number
of
14­
day
survivors
as
a
percent
of
normal
hatchlings,
reduced
viable
embryos
as
a
percent
of
eggs
set,
and
reduced
14­
day
survivors
as
a
percentage
of
eggs
set.
The
guideline
requirement
for
avian
reproduction
testing
(
71­
4)
is
fulfilled
(
MRID
#
43032501,
and
43032502)
.

iii.
Mammals,
Acute
and
Chronic
Wild
mammal
testing
is
required
on
a
case­
by­
case
basis,
depending
on
the
results
of
lower
tier
laboratory
mammalian
studies,
intended
use
pattern
and
pertinent
environmental
fate
characteristics.
In
most
cases,
rat
or
mouse
toxicity
values
obtained
from
the
Agency'
s
Health
Effects
Division
(
HED)
substitute
for
wild
mammal
testing.
These
toxicity
values
are
reported
in
the
Table
below.

32
Table
14.
Mammalian
Acute
Toxicity
Species
%
ai
Test
Type
Toxicity
Values/
category
MRID
No.

Mule
deer
(
Odocoileus
hemionus
)

Domestic
goat
(
Capra
hircus
)

Laboratory
rat
(
Rattus
norvegicus)
97
97
94.4
acute
oral
acute
oral
acute
oral
2.5
mg/
kg
very
highly
toxic
<
15
mg/
kg
very
highly
toxic
1.9
mg/
kg
females
I
6.2
mg/
kg
males
I
00160000
00160000
072293
Laboratory
mouse
(
Mus
musculus)
94.4
acute
oral
8.2
mg/
kg
(
female)
I
7.0
mg/
kg
(
male)
I
072293
Laboratory
rat
(
Rattus
norvegicus)
sulfone
metabolite
acute
oral
11.24
mg/
kg
(
female)
I
0071873
Test
results
indicate
that
disulfoton
is
very
highly
toxic
(
Category
I)
to
small
mammals
on
an
acute
oral
basis.
Testing
on
the
sulfone
metabolite
also
indicates
very
high
acute
oral
toxicity.

Table
15.
Mammalian
Chronic
Toxicity
Species
%
ai
Test
Type
Toxicity
Values/
category
MRID
No.

Laboratory
rat
(
Rattus
norvegicus)
97.8
2­
generation
reproduction
maternal
NOAEC=
2.4
ppm/
LOAEC=
7.2
ppm
repro
NOAEC=
0.8
ppm/
LOAEC=
2.4
ppm
261990
The
two­
generation
rat
reproduction
study
provided
a
reproductive
NOEC
level
of
0.8
ppm.
Parameters
affected
in
the
study
included
decreased
litter
size,
lowered
pup
survival,
and
decreased
pup
weight.

iv.
Insects
A
honey
bee
acute
contact
study
using
the
technical
grade
of
the
active
ingredient
is
required
for
disulfoton
because
its
use
may
result
in
honey
bee
exposure.
Results
of
this
test
are
as
follows:

33
Table
16.
Nontarget
Insect
Acute
Contact
Toxicity
Species
%
ai
LD50
(
F
g/
bee)
Toxicity
Category
MRID
No.
Author/
Year
Study
Classification
Honey
bee
(
Apis
mellifera
)
technical
4.1
moderately
toxic
05004151
1968
core
Honey
bee
(
Apis
mellifera)
sulfone
metabolite
91.6
0.96
highly
toxic
42582902
1992
core
Honey
bee
(
Apis
mellifera)
sulfoxide
metabolite
85.3
1.11
moderately
toxic
42582901
1992
core
The
results
indicate
that
disulfoton
is
moderately
toxic
to
bees
and
disulfoton
sulfone,
and
disulfoton
sulfoxide
are
very
highly
toxic
to
bees
on
an
acute
contact
basis.
The
guideline
requirement
(
141­
1)
is
fulfilled
for
parent
disulfoton
(
MRID
#
05004151)
,
as
well
as
for
the
two
major
metabolites
(
MRID
#
42582902,
42582901)
.

A
honey
bee
toxicity
of
residues
on
foliage
study
using
the
typical
end­
use
product
was
submitted
for
disulfoton.
The
results
of
this
study
are
tabulated
below.

Table
17.
Nontarget
Insect
Toxicity
of
Residues
on
Foliage
Species
Formulatio
n
LD50
(
lb.
/
A)
Toxicity
Category
MRID
or
ACC
#
Author/
year
Guideline
Classification
Honey
bee
(
Apis
mellifera
8
E.
C.
>
1.0
0163423
core
The
results
indicate
that
disulfoton
residues
on
foliage
are
not
toxic
to
honey
bees
at
application
rates
up
to
1.0
lb
/
A.
Guideline
141­
2
is
fulfilled
for
disulfoton
(
ACC
#
0163423)
.

v.
Terrestrial
Field
Testing
Terrestrial
field
testing
was
conducted
for
disulfoton
because
of
the
high
toxicity
of
the
chemical
in
relation
to
expected
environmental
concentrations.
Three
field
studies
were
originally
required
in
the
1985
Registration
Standard,
but
only
one
screening
level
field
study
and
one
residue
monitoring
study
were
submitted.
The
Level
I
(
screening)
field
study
was
conducted
on
potatoes
in
Benton
county,
Washington,
using
the
15G
formulation
(
MRID
#
410560­
01)
.
The
study
did
show
mortality
to
wildlife
from
the
use
of
the
15G
formulation
on
potatoes;
since
it
was
a
screening
study,
there
were
no
further
conclusions.
If
no
mortality
had
been
observed,
the
study
would
not
have
been
classified
as
core
as
the
study
design
and
carcass
searching
techniques
were
insufficient
to
negate
the
presumption
of
risk.
The
study
fulfilled
Guideline
71­

34
5
only
because
adverse
effects
were
seen.
The
fact
that
bird
and
mammal
carcasses
were
found
even
with
such
an
insensitive
study
design
emphasizes
the
high
acute
risk
this
chemical
poses
to
terrestrial
vertebrates.

The
residue
monitoring
study
(
MRID
#
412018­
01)
was
conducted
with
Di­
Syston
8
(
foliar)
on
potatoes
in
Michigan.
Disulfoton
was
aerially
applied
to
potatoes
3
times
at
1
lb
ai/
acre
in
Michigan.
The
results
of
this
study
indicated
that
there
was
hazard
to
terrestrial
wildlife
from
the
foliar
application
of
disulfoton,
and
also
suggested
that
a
full
Level
1
field
study
was
needed
with
the
foliar
application.
An
second
residue
monitoring
study
(
MRID
#
411189­
01)
was
performed,
in
which
disulfoton
was
soil
incorporated
by
ground
equipment,
(
initially
in
furrow
at
planting
at
3
lb
ai/
acre
and
6
­
7
weeks
later
as
a
side
dressing
at
3
lbs
ai/
acre)
.
Although
the
residues
on
vegetation
were
much
lower
in
this
second
study
as
compared
to
the
first,
nevertheless
they
posed
potential
acute
and
chronic
risk
especially
to
small
mammals.

B.
Toxicity
to
Freshwater
Aquatic
Animals
i.
Freshwater
Fish,
Acute
Two
freshwater
fish
toxicity
studies
using
the
technical
grade
of
the
active
ingredient
are
required
to
establish
the
toxicity
of
a
pesticide
to
fish.
The
preferred
test
species
are
rainbow
trout
(
a
Coldwater
fish)
and
bluegill
sunfish
(
a
warmwater
fish)
.
Results
of
these
tests
are
as
follows:

35
Table
18.
Freshwater
Fish
Acute
Toxicity
Species
%
ai
LC50
(
ppb
ai)
Toxicity
Category
MRID
No.
Author/
Year
Study
Classification
Rainbow
trout
(
Oncorhynchus
mykiss)
98
tech
15G
65EC
sulfone
metabolite
sulfoxide
metabolite
1,850
3,000
13,900
3,500
>
9,200
60,300
moderately
toxic
moderately
toxic
slightly
toxic
moderately
toxic
moderately
toxic
slightly
toxic
40098001
F.
L.
Mayer/
1986
0068268
Lamb/
1972
0068268
Lamb/
1972
0068268
Lamb/
1972
42585111
Gagliano/
1992
42585110
Gagliano/
1992
core
core
core
core
core
core
Bluegill
sunfish
(
Lepomis
macrochirus
98.0
Tech
15G
65EC
20E
sulfone
metabolite
sulfoxide
metabolite
300
39
250
59
8.2
112
188
highly
toxic
very
highly
toxic
highly
toxic
very
highly
toxic
very
highly
toxic
highly
toxic
highly
toxic
40098001
F.
L.
Mayer/
1986
0068268
Lamb/
1972
0068268
Lamb/
1972
0068268
Lamb/
1972
229299
1962
42585108
Gagliano/
1992
42585107
Gagliano/
1992
core
core
core
core
supplemental
core
core
Channel
catfish
(
Ictalurus
punctatus
)
98.0
4,
700
moderately
toxic
40098001
Mayer/
1986
core
Goldfish
(
Carassius
auratus
)
90
7,200
moderately
toxic
229299
1962
supplemental
Largemouth
bass
(
Micropterus
salmoides
)
98.0
60
very
highly
toxic
40098001
Mayer/
1986
core
Fathead
minnow
(
Pimphales
promelas
)
98.0
4,
300
moderately
toxic
40098001
Mayer/
1986
core
Guppy
90
280
highly
toxic
229299
supplemental
36
These
results
indicate
that
parent
disulfoton
is
very
highly
toxic
to
slightly
toxic
to
freshwater
fish
on
an
acute
basis.
The
two
major
metabolites,
disulfoton
sulfone
and
disulfoton
sulfoxide,
are
highly
toxic
to
slightly
toxic
to
freshwater
fish
on
an
acute
basis.
The
rainbow
trout,
a
Coldwater
species,
appears
to
be
somewhat
less
sensitive
than
the
warmwater
species
to
disulfoton
and
its
metabolites.
The
guideline
requirement
(
72­
1)
is
fulfilled
for
parent
disulfoton,
disulfoton
sulfone,
and
disulfoton
sulfoxide.

ii.
Freshwater
Fish,
Chronic
A
freshwater
fish
early
life­
stage
test
using
the
technical
grade
of
the
active
ingredient
is
required
for
a
pesticide
when
it
may
be
applied
directly
to
water
or
if
the
end­
use
product
is
expected
to
be
transported
to
water
from
the
intended
use
site,
and
the
following
conditions
are
met:
(
1)
the
pesticide
is
intended
for
use
such
that
its
presence
in
water
is
likely
to
be
continuous
or
recurrent
regardless
of
toxicity,
(
2)
any
aquatic
acute
LC50
or
EC50
is
less
than
1
mg/
l,
(
3)
the
EEC
in
water
is
equal
to
or
greater
than
0.01
of
any
acute
LC50
or
EC50
value,
or,
(
4)
the
actual
or
estimated
environmental
concentration
in
water
resulting
from
use
is
less
than
0.01
of
any
acute
LC50
or
EC50
value
and
any
one
of
the
following
conditions
exist:
studies
of
other
organisms
indicate
the
reproductive
physiology
of
fish
may
be
affected,
physicochemical
properties
indicate
cumulative
effects,
or
the
pesticide
is
persistent
in
water
(
e.
g.
,
half­
life
greater
than
4
days)
.
The
preferred
test
species
is
rainbow
trout,
but
other
species
may
be
used.
.
Freshwater
fish
early
life­
stage
testing
was
required
for
disulfoton
due
to
the
likelihood
of
drift
and
runoff
from
the
application
sites,
the
likelihood
of
repeated
or
continuous
exposure
from
multiple
applications,
and
the
high
acute
toxicity
to
several
species
of
freshwater
fish.
Results
of
this
test
are
tabulated
below.

Table
19.
Freshwater
Fish
Early
Life­
Stage
Toxicity
Species
%
ai
NOAEC/
LOAEC
(
ppb
ai)
MATC
(
ppb)
Endpoints
Affected
MRID
No.
Author/
Year
Study
Classification
Rainbow
trout
(
Oncorhynchus
mykiss)
98
220/
420
300
growth
41935801
1991
core
The
guideline
requirement
(
72­
4a)
is
fulfilled
(
MRID
41935801)
.

A
freshwater
fish
life­
cycle
test
using
the
technical
grade
of
the
active
ingredient
is
not
required
for
disulfoton.
A
marine/
estuarine
fish
life­
cycle
test
was
conducted
with
disulfoton,
since
the
marine/
estuarine
species
is
more
sensitive
than
the
freshwater
species.
This
is
discussed
in
section
c
ii
,
below.

iii.
Freshwater
Invertebrates,
Acute
A
freshwater
aquatic
invertebrate
toxicity
test
using
the
technical
grade
of
the
active
ingredient
37
is
required
to
establish
the
toxicity
of
a
pesticide
to
invertebrates.
The
preferred
test
species
is
Daphnia
magna
.
Results
of
this
test
are
tabulated
below.

Table
20.
Freshwater
Invertebrate
Toxicity
Species
%
ai
LC50/
EC50
(
ppb
ai)
Toxicity
Category
MRID
No.
Author/
Year
Study
Classification
Waterflea
(
Daphnia
magna)
Waterflea
(
Daphnia
magna)

Waterflea
(
Daphnia
magna
98.6
Sulfone
metabolite
87.4
sulfoxide
metabolite
85.3
13.0
35.2
64
very
highly
toxic
very
highly
toxic
very
highly
toxic
00143401
Heimbach/
1985
42585112
Gaglaino/
1992
42585109
Gagliano/
1992
core
core
core
Scud
(
Gammarus
fasciatus
)
98
technical
52
27
very
highly
toxic
very
highly
toxic
40098001
Mayer/
1986
05017538
1972
supplemental
supplemental
Glass
shrimp
(
Palaemonetes
kadiakensis
)
98
3.9
very
highly
toxic
40094602
1980
supplemental
Stonefly
(
Acroneuria
pacifica
)
89
<
8.2
very
highly
toxic
229299
1962
supplemental
Stonefly
(
Pteronarcys
californica
)
98
5.0
very
highly
toxic
40098001
Mayer/
1986
core
The
results
indicate
that
disulfoton
and
its
metabolites,
disulfoton
sulfone
and
disulfoton
sulfoxide,
are
very
highly
toxic
to
aquatic
invertebrates
on
an
acute
basis.
The
guideline
requirement
(
72­
2)
is
fulfilled.

iv.
Freshwater
Invertebrate,
Chronic
A
freshwater
aquatic
invertebrate
life­
cycle
test
using
the
technical
grade
of
the
active
ingredient
is
required
for
a
pesticide
if
the
end­
use
product
may
be
applied
directly
to
water
or
expected
to
be
transported
to
water
from
the
intended
use
site,
and
the
following
conditions
are
met:
(
1)
the
pesticide
is
intended
for
use
such
that
its
presence
in
water
is
likely
to
be
continuous
or
recurrent
regardless
of
toxicity,
(
2)
any
aquatic
acute
LC50
or
EC50
is
less
than
1
mg/
l,
or,
(
3)
the
EEC
in
water
is
equal
to
or
greater
than
0.01
of
any
acute
EC50
or
LC50
value,
or,
(
4)
the
actual
or
estimated
environmental
concentration
in
water
resulting
from
use
is
less
than
0.01
of
any
aquatic
acute
EC50
or
LC50
value
and
any
of
the
following
conditions
exist:
studies
of
other
38
organisms
indicate
the
reproductive
physiology
of
invertebrates
may
be
affected,
physicochemical
properties
indicate
cumulative
effects,
or
the
pesticide
is
persistent
in
water
(
e.
g.
,
half­
life
greater
than
4
days)
.
The
preferred
test
species
is
Daphnia
magna
.
Freshwater
aquatic
invertebrate
life­
cycle
testing
was
required
for
disulfoton.
Results
of
this
test
are
tabulated
below.

Table
21.
Freshwater
Aquatic
Invertebrate
Life­
Cycle
Toxicity
Species
%
ai
NOAEC/
LOAE
C
(
ppb)
MATC
(
ppb)
Endpoints
Affected
MRID
No.
Author/
Year
Study
Classifica
tion
Waterflea
(
Daphnia
magna)
98
0.037/
0.070
0.051
survival,
length,
and
#
young/
adult
41935802
Blakemore/
1991
core
Waterflea
(
Daphnia
magna)
99.3
Sulfone
0.14/
0.27
0.19
length
43738001
Bowers/
1995
core
Waterflea
(
Daphnia
magna)
98.9
Sulfoxide
1.53/
2.97
2.13
Weight
&
length
43738002
Bowers/
1995
core
The
guideline
requirement
(
72­
4)
is
fulfilled
(
MRID
#
41935802)
.

v.
Freshwater
Field
Studies
A
microcosm
study
was
conducted
to
evaluate
the
effects
of
runoff
of
disulfoton
on
a
simulated
aquatic
field
system
(
MRID
#
435685­
01/
Cook
and
Kennedy,
1994)
.
Three
dose
levels
­
­
3,
10,
30
ppb
­
­
were
established
in
two
replicate
tanks
per
dose.
Each
tank
was
dosed
4
times
at
7
day
intervals.
The
study
demonstrated
that
3
ppb
is
the
maximum
acceptable
toxicant
concentration
(
MATC)
for
this
chemical
in
aquatic
systems.
At
treatment
levels
of
3
ppb
and
higher,
adverse
effects
were
seen
on
zooplankton
numbers,
zooplankton
community
similarity,
adult
macro
invertebrate
population
numbers,
and
adult
macroinvertebrate
community
composition;
however,
some
recovery
trend
was
observed
on
all
of
these
parameters
at
10
ppb
and
many
at
30
ppb
by
the
end
of
the
77
day
study.
A
bluegill
LC50
of
25
ppb
and
LC10
of
4.7
ppb
was
established
for
the
first
27
days
during
which
the
four
applications
occurred.

The
North
Carolina
Cooperative
Extension
Service
submitted
two
stream
surveys
conducted
in
five
of
the
major
Christmas
tree
farming
in
North
Carolina.
Although
neither
survey
was
targeted
for
disulfoton,
nor
analyzed
for
chemical
residues
they
attempted
to
reflect
the
impact
to
aquatic
macro
invertebrates
from
the
overall
cultural
practices
associated
with
Christmas
tree
farming
in
Western
North
Carolina.
The
first
survey,
conducted
by
Department
of
Environmental
Health
and
Natural
Resources
(
DEHNR)
,
examined
one
station
on
each
of
11
streams
(
Lenant,
D.
1999
unpublished)
.
Eight
of
the11
streams
were
sampled
once
(
in
May
39
presumably
after
the
April/
May
application
of
disulfoton)
.
The
3
other
streams
were
sampled
a
second
time
in
August
as
a
means
to
correct
for
likely
seasonal
changes
in
the
species
composition
of
Ephemeroptera,
Plecoptera
and
Trichoptera
(
EPT)
.
The
second
survey
was
conducted
from
12/
98
thru
early
to
late
summer
1999
(
Sidebottom,
J.
2000
unpublished)
The
survey
examined
5
sites
 
each
consisting
of
an
area
adjacent
to
or
downstream
from
a
Christmas
tree
farm
paired
with
its
own
reference
site
(
either
a
station
on
the
same
stream,
but
above
the
tree
farm
or
a
second
stream)
.
The
data
collected
included
the
total
number
of
insects
and
the
break
out
(
expressed
as
a
%
of
insects)
for
mayflies,
stoneflies,
caddisflies,
riffle
beetles
and
 
other
 
insects.
.
A
species
list
for
mayflies,
stoneflies
and
caddisflies
along
with
an
index
of
their
sensitivity
and
the
dates
collected
was
provided
for
3
of
the
5
sites.
See
the
risk
to
aquatic
organisms
section
on
page
64
for
further
discussion
of
results
and
the
significance
to
the
disulfoton
risk
assessment.

C.
Toxicity
to
Estuarine
and
Marine
Animals
i.
Estuarine
and
Marine
Fish,
Acute
Acute
toxicity
testing
with
estuarine/
marine
fish
using
the
technical
grade
of
the
active
ingredient
is
required
for
a
chemical
when
the
end­
use
product
is
intended
for
direct
application
to
the
marine/
estuarine
environment
or
the
active
ingredient
is
expected
to
reach
this
environment
because
of
its
use
in
coastal
counties.
The
preferred
test
species
is
sheepshead
minnow.
Marine/
estuarine
acute
testing
was
conducted
with
disulfoton.
Results
of
these
tests
are
tabulated
below.

Table
22.
Acute
Toxicity
of
Disulfoton
to
Estuarine/
Marine
Fish
Species
%
ai
LC50
(
ppb)
Toxicity
Category
MRID
No.
Author/
Year
Study
Classification
Sheepshead
minnow
(
Cyprinodon
variegatus)

Sheepshead
minnow
(
Cyprinodon
variegatus
)
95.5
97.8
520
1000
highly
toxic
highly
toxic
4022840
Mayer/
1986
40071602
Surprenant/
1986
supplemental
core
Sheepshead
minnow
(
Cyprinodon
variegatus
)
Sulfone
metabolite
100%
1060
moderately
toxic
44369901
Lam/
1997
core
Sheepshead
minnow
(
Cyprinodon
variegatus
)
Sulfoxide
metabolite
98.2%
11300
slightly
toxic
44369902
Lam/
1997
core
The
results
indicate
that
disulfoton
is
highly
toxic
to
estuarine/
marine
fish
on
an
acute
basis.
The
guideline
requirement
(
72­
3a)
is
fulfilled
for
parent
disulfoton
(
MRID
#
40071602)
and
the
sulfone
and
sulfoxide
metabolites
(
MRID
#
44369901
and
44369902,
respectively)
.

40
ii.
Estuarine
and
Marine
Fish,
Chronic
Estuarine/
marine
fish
early
life­
stage
and
life­
cycle
tests
using
the
technical
grade
of
the
active
ingredient
were
required
for
disulfoton
due
to
the
high
acute
toxicity
to
estuarine/
marine
fish.
The
results
of
these
studies
are
as
follows:

Table
23.
Chronic
Toxicity
of
Disulfoton
to
Marine/
Estuarine
Fish
Species
%
a.
i.
Test
Type
NOEC/
LOEC
(
ppb)
MAT
C
(
ppb)
Parameters
Affected
MRID
#
Author/
year
Classification
Sheepshead
minnow
(
Cyprinodon
variegatus
)
97.4
early
life­
stage
16.2/
32.9
23.1
survival,
length,
wet
weight
42629001
Lintott/
1993
core
Sheepshead
minnow
(
Cyprinodon
variegatus
)
98
life­
cycle
0.96
1
/
2.
9
1.7
fecundity,
morphological
abnormalities,
growth,
hatching
success
43960501
Dionne/
1996
supplemental
1
An
actual
NOEC
was
not
achieved
in
this
study.
The
value
reported
here
is
an
EC05,
extrapolated
using
linear
regression.

The
results
indicate
that
disulfoton
impacts
the
reproductive
ability,
as
well
as
the
growth
and
larval
survival,
of
sheepshead
minnows
at
levels
as
low
as
2.9
ppb.
The
guideline
requirements
(
72­
4
and
72­
5)
are
fulfilled
(
MRID
#
42629001
and
43960501,
respectively)
.

iii.
Estuarine
and
Marine
Invertebrates,
Acute
Acute
toxicity
testing
with
estuarine/
marine
invertebrates
using
the
technical
grade
of
the
active
ingredient
is
required
for
a
pesticide
when
the
end­
use
product
is
intended
for
direct
application
to
the
marine/
estuarine
environment
or
the
active
ingredient
is
expected
to
reach
this
environment
because
of
its
use
in
coastal
counties.
The
preferred
test
species
are
mysid
shrimp
and
eastern
oyster.
Estuarine/
marine
invertebrate
testing
was
required
for
disulfoton.
Results
of
these
tests
are
as
follows:

41
Table
24.
Acute
Toxicity
of
Disulfoton
to
Estuarine/
Marine
Invertebrates
Species
%
ai.
LC50/
EC50
(
ppb)
Toxicity
Category
MRID
No.
Author/
Year
Study
Classification
Eastern
oyster
(
Crassostrea
virginica)

Eastern
oyster
(
Crassostrea
virginica)

Eastern
oyster
(
Crassostrea
virginica)
97.8
tech
95.5
720
900
720
highly
toxic
highly
toxic
highly
toxic
40071603
Surprenant/
1986
120480
/
1965
40228401
Mayer/
1986
core
supplemental
core
Mysid
(
Mysidopsis
bahia
)
97.8
100
very
highly
toxic
40071601
Surprenant/
1986
core
Brown
shrimp
(
Penaeus
aztecus
)
95.5
15
very
highly
toxic
40228401
Mayer/
1986
supplemental
The
results
indicate
that
disulfoton
is
very
highly
to
highly
toxic
to
estuarine/
marine
invertebrates
on
an
acute
basis.
The
guideline
requirements
(
72­
3b
and
72­
3c)
are
fulfilled
(
MRID
#
40071603
and
40071601,
respectively)
.

iv.
Estuarine
and
Marine
Invertebrate,
Chronic
An
estuarine/
marine
invertebrate
life­
cycle
toxicity
test
is
required
for
a
pesticide
if
the
end­
use
product
may
be
applied
directly
to
water
or
expected
to
be
transported
to
water
from
the
intended
use
site,
and
the
following
conditions
are
met:
(
1)
the
pesticide
is
intended
for
use
such
that
its
presence
in
water
is
likely
to
be
continuous
or
recurrent
regardless
of
toxicity,
(
2)
any
aquatic
acute
LC50
or
EC50
is
less
than
1
mg/
l,
or,
(
3)
the
EEC
in
water
is
equal
to
or
greater
than
0.01
of
any
acute
EC50
or
LC50
value,
or,
(
4)
the
actual
or
estimated
environmental
concentration
in
water
resulting
from
use
is
less
than
0.01
of
any
aquatic
acute
EC50
or
LC50
value
and
any
of
the
following
conditions
exist:
studies
of
other
organisms
indicate
the
reproductive
physiology
of
invertebrates
may
be
affected,
physicochemical
properties
indicate
cumulative
effects,
or
the
pesticide
is
persistent
in
water
(
e.
g.
,
half­
life
greater
than
4
days)
.
Estuarine/
marine
invertebrate
testing
was
required
for
disulfoton
due
to
its
high
acute
toxicity
to
estuarine/
marine
organisms,
and
the
greater
acute
sensitivity
of
marine/
estuarine
organisms
compared
to
freshwater
organisms.
The
results
of
this
test
are
as
follows:

42
Table
25.
Life­
Cycle
Toxicity
of
Disulfoton
to
Estuarine/
Marine
Invertebrates
Species
%
ai
NOEC/
LOE
C
(
ppb)
MATC
(
ppb)
Parameters
Affected
MRID
#
Author/
Year
Classificatio
n
Mysid
(
Mysidopsis
bahia
)
98.5
2.
35
1
/
8.
26
5.
30
growth
43610901
Davis/
1995
core
1
A
NOEC
was
not
achieved
in
the
study,
so
an
extrapolated
EC05
for
growth
was
calculated
using
linear
regression.
The
MATC
reported
is
the
mean
between
the
EC05
and
LOEC
values.

The
growth
of
mysids
was
adversely
affected
at
levels
of
8.26
ppb
and
higher.
Production
and
survival
of
young
was
adversely
affected
at
levels
of
120
ppb
and
higher.

v.
Estuarine
and
Marine
Field
Studies
No
estuarine
or
marine
field
study
data
is
available
for
disulfoton.

D.
Toxicity
to
Plants
i.
Terrestrial
Currently,
terrestrial
plant
testing
is
not
required
for
pesticides
other
than
herbicides
except
on
a
case­
by­
case
basis
(
e.
g.
,
labeling
bears
phytotoxicity
warnings,
incidents
of
plant
damage
have
been
reported,
or
literature
indicating
phytotoxicity
is
available)
.
The
insecticide
disulfoton
does
have
phytotoxicity
warnings
on
product
labels;
therefore,
Tier
I
terrestrial
plant
testing
(
Guideline
122­
1)
is
required
for
disulfoton.
No
such
data
have
been
submitted
to
date.

ii.
Aquatic
Plants
Aquatic
plant
testing
is
not
required
for
pesticides
other
than
herbicides
except
on
a
case­
by­
case
basis
(
e.
g.
,
labeling
bears
phytotoxicity
warnings,
incidents
have
been
reported
involving
plants,
or
literature
is
available
that
indicates
phytotoxicity)
.
The
insecticide
disulfoton
does
have
phytotoxicity
warnings
on
product
labels;
therefore,
Tier
I
aquatic
plant
testing
(
Guideline
122­
2)
is
required
for
disulfoton.
No
such
data
have
been
submitted
to
date.

4.
Ecological
Risk
Assessment
Risk
assessment
integrates
the
results
of
the
exposure
and
ecotoxicity
data
to
evaluate
the
likelihood
of
adverse
ecological
effects.
One
method
of
integrating
the
results
of
exposure
and
ecotoxicity
data
is
called
the
quotient
method.
For
this
method,
risk
quotients
(
RQs)
are
calculated
by
dividing
exposure
estimates
by
ecotoxicity
values,
both
acute
and
chronic.

RQ
=
EXPOSURE/
TOXICITY
43
RQs
are
then
compared
to
OPP'
s
levels
of
concern
(
LOCs)
.
These
LOCs
are
criteria
used
by
OPP
to
indicate
potential
risk
to
nontarget
organisms
and
the
need
to
consider
regulatory
action.
The
criteria
indicate
that
a
pesticide
used
as
directed
has
the
potential
to
cause
adverse
effects
on
nontarget
organisms.
LOCs
currently
address
the
following
risk
presumption
categories:
(
1)
acute
­
potential
for
acute
risk
is
high
regulatory
action
may
be
warranted
in
addition
to
restricted
use
classification
(
2)
acute
restricted
use
­
the
potential
for
acute
risk
is
high,
but
this
may
be
mitigated
through
restricted
use
classification
(
3)
acute
endangered
species
­
the
potential
for
acute
risk
to
endangered
species
is
high
regulatory
action
may
be
warranted,
and
(
4)
chronic
risk
­
the
potential
for
chronic
risk
is
high
regulatory
action
may
be
warranted.
Currently,
EFED
does
not
perform
assessments
for
chronic
risk
to
plants,
acute
or
chronic
risks
to
nontarget
insects,
or
chronic
risk
from
granular/
bait
formulations
to
mammalian
or
avian
species.

The
ecotoxicity
test
values
(
i.
e.
,
measurement
endpoints)
used
in
the
acute
and
chronic
risk
quotients
are
derived
from
the
results
of
required
studies.
Examples
of
ecotoxicity
values
derived
from
the
results
of
short­
term
laboratory
studies
that
assess
acute
effects
are:
(
1)
LC50
(
fish
and
birds)
(
2)
LD50
(
birds
and
mammals
(
3)
EC50
(
aquatic
plants
and
aquatic
invertebrates)
and
(
4)
EC25
(
terrestrial
plants)
.
Examples
of
toxicity
test
effect
levels
derived
from
the
results
of
long­
term
laboratory
studies
that
assess
chronic
effects
are:
(
1)
LOEC
(
birds,
fish,
and
aquatic
invertebrates)
(
2)
NOEC
(
birds,
fish
and
aquatic
invertebrates)
and
(
3)
MATC
(
fish
and
aquatic
invertebrates)
.
For
birds
and
mammals,
the
NOEC
value
is
used
as
the
ecotoxicity
test
value
in
assessing
chronic
effects.
Other
values
may
be
used
when
justified.
Generally,
the
MATC
(
defined
as
the
geometric
mean
of
the
NOEC
and
LOEC)
is
used
as
the
ecotoxicity
test
value
in
assessing
chronic
effects
to
fish
and
aquatic
invertebrates.
However,
the
NOEC
is
used
if
the
measurement
end
point
is
production
of
offspring
or
survival.

44
Risk
presumptions,
along
with
the
corresponding
RQs
and
LOCs
are
tabulated
below.

Table
26.
Risk
Presumptions
for
Terrestrial
Animals
Risk
Presumption
RQ
LOC
Birds
and
Wild
Mammals
Acute
Risk*
EEC
1
/
LC50
or
LD50/
sqft
2
or
LD50/
day
3
0.5
Acute
Restricted
Use
EEC/
LC50
or
LD50/
sqft
or
LD50/
day
(
or
LD50
0.2
<
50
mg/
kg)

Acute
Endangered
Species
EEC/
LC50
or
LD50/
sqft
or
LD50/
day
0.1
Chronic
Risk
EEC/
NOAEC
1
1
abbreviation
for
Estimated
Environmental
Concentration
(
ppm)
on
avian/
mammalian
food
items
2
mg/
ft
2
3
mg
of
toxicant
consumed/
day
LD50
*
wt.
of
bird
LD50
*
wt.
of
bird
*
In
the
past,
this
category
read
 
Acute
High
Risk.
 
The
EFED
is
changing
the
wording
of
the
conclusions
to
 
Acute
Risk
 
when
the
acute
LOC
exceedences
are
based
solely
on
a
screening
level
assessment.
.

45
Table
27.
Risk
Presumptions
for
Aquatic
Animals
Risk
Presumption
RQ
LOC
Acute
Risk*
EEC
1
/
LC50
or
EC50
0.5
Acute
Restricted
Use
EEC/
LC50
or
EC50
0.1
Acute
Endangered
Species
EEC/
LC50
or
EC50
0.05
Chronic
Risk
EEC/
MATC
or
NOAEC
1
1
EEC
=
(
ppm
or
ppb)
in
water
*
In
the
past,
this
category
read
 
Acute
High
Risk.
 
The
EFED
is
changing
the
wording
of
the
conclusions
to
 
Acute
Risk
 
when
the
acute
LOC
exceedences
are
based
solely
on
a
screening
level
assessment.
.

Table
28.
Risk
Presumptions
for
Plants
Risk
Presumption
RQ
LOC
Terrestrial
and
Semi­
Aquatic
Plants
Acute
Risk*
EEC
1
/
EC25
1
Acute
Endangered
Species
EEC/
EC05
or
NOEC
1
Aquatic
Plants
Acute
Risk*
EEC
2
/
EC50
1
Acute
Endangered
Species
EEC/
EC05
or
NOAEC
1
1
EEC
=
lbs
ai/
A
2
EEC
=
(
ppb/
ppm)
in
water
*
In
the
past,
this
category
read
 
Acute
High
Risk.
 
The
EFED
is
changing
the
wording
of
the
conclusions
to
 
Acute
Risk
 
when
the
acute
LOC
exceedences
are
based
solely
on
a
screening
level
assessment.
.

A.
Risk
to
Nontarget
Terrestrial
Animals
i.
Acute
and
Chronic
Risk
to
Birds
and
Mammals
from
Nongranular
products.

Nongranular
formulations
of
disulfoton
are
applied
either
as
a
foliar
spray
(
often
by
air)
,
or
as
a
spray
directly
to
soil
either
preplant,
or
to
soil
beside
the
crop
(
potato
side
dressing)
.
Foliar
sprays
are
assumed
to
settle
directly
onto
vegetation
and
other
avian
and
mammalian
food
items.
The
residues
on
these
food
items
are
estimated
by
using
a
nomograph
reported
Hoerger
and
Kenega,
1972,
and
as
modified
by
Fletcher,
et
al,
1994.

The
acute
risk
quotients
for
broadcast
applications
of
nongranular
products
are
presented
below.

46
Table
29.
Avian
and
Mammal
Acute
Risk
Quotients
for
peak
exposure
levels
based
on
maximum
residue
values.
Assuming
an
avian
dietary
LC50
of
333
ppm
(
Japanese
quail)
,
and
mammal
LD50
of
1.9
mg/
kg
and
a
3.3­
day
half­
life
The
mammalian
LD50
of
1.9
mg/
kg
was
used
to
estimate
1­
day
LC50s
for
three
different
sized
mammals:
15
gram
mammal
that
eats
0.95
of
its
body
weight
per
day:
LC50
=
2
ppm
35
gram
mammal
that
eats
0.66
of
its
body
weight
per
day:
LC50
=
2.9
ppm
1000
gram
mammal
that
eats
0.15
of
its
body
weight
per
day:
LC50
=
12.7
ppm
Formula:
1­
day
LC50
=
LD50
(
mg/
kg)
/
proportion
of
body
weight
consumed
Use
Scenarios
Maximum
Exposure
(
EEC
in
ppm)
1
and
RQ
EEC/
LC50
BIRDS
MAMMALS
short
grass
broad
leaf
long
grass
seeds
fruit
short
grass
broad
leaf
long
grass
seeds
fruit
Tobacco
;
soil
(
ground)
;
4
lbs
ai/
acre;
1
appl
per
season
EEC
RQ
960
540
440
60
2.8
1.
6
1.3
0.2
960
540
440
60
15
g
35
g
1000
g
480
331
75
270
186
42
220
151
34
30
20
4
Beans;
soil
;
2
lbs
ai/
acre;
1
appl
per
season
EEC
RQ
480
270
220
30
1.4
0.
8
0.7
0.1
480
270
220
30
15
g
35
g
1000
g
240
186
42
135
93
21
110
75
17
15
10
2
Broccoli
and
wheat;
soil;
1
lbs
ai/
acre;
1
appl
per
season.
EEC
RQ
240
135
110
15
0.7
0.4
0.
3
<
0.1
240
135
110
15
15
g
35
g
1000
g
120
82
18
67
46
10
55
37
8
7
5
1
Potato;
soil
(
ground)
;
4
lbs
ai/
acre;
2
appl
per
season;
14
day
interval
EEC
RQ
1010
568
463
63
3.0
1.
7
1.4
0.2
1010
568
463
63
15
g
35
g
1000
g
505
348
79
284
195
44
231
159
36
31
21
4
Pecans
&
potatoes;
(
aerial/
ground)
;
1
lb
ai/
acre;
3
appl
per
season;
14­
day
interval
(
Cotton;
soil
(
ground)
;
1
lb
ai/
acre;
3
appl
per
season;
21­
day
interval:
:
should
have
slightly
less
risk
due
to
less
distribution
of
spray
and
peak
&
average
residues
are
lower
)
EEC
RQ
253
142
116
15
0.7
0.
4
0.3
<
0.1
253
142
116
15
15
g
35
g
1000
g
126
87
19
71
48
11
58
40
9
7
5
1
Sorghum;
soil
(
aerial/
ground)
;
1
lb
ai/
acre;
2
appl
per
season;
14­
day
interval
(
Barley;
foliar
(
aerial/
ground)
;
1.0
lb
ai/
acre;
2
appl
per
season;
21­
day
interval:
should
have
slightly
lower
risk
off
site,
since
peak
and
average
residues
are
lower;
however,
on
site
the
risk
may
be
higher
due
to
crop
foliage
being
sprayed
directly)

(
Spring
wheat;
foliar
(
aerial/
ground)
;
0.75
lb
ai/
acre;
2
appl
per
season;
30­
day
interval:
should
have
slightly
lower
risk
off
site,
since
peak
and
average
residues
are
lower.
EEC
RQ
252
142
115
15
0.7
0.
4
03
<
0.1
252
142
115
15
15
g
35
g
1000
g
126
87
19
71
48
11
57
40
9
7
5
1
Sorghum;
foliar
(
aerial/
ground)
;
0.5
lb
ai/
acre;
3
appl
per
season;
14­
day
interval
(
Cotton;
foliar
(
aerial/
ground)
;
0.5
lb
ai/
acre;
3
appl
per
season;
21­
day
interval:
should
have
slightly
lower
risk
since
peak
and
average
residues
are
lower
)
EEC
RQ
126
71
58
7
0.4
0.
2
0.2
<
0.1
126
71
58
7
15
g
35
g
1000
g
63
43
9
35
24
5
29
20
4
3
2
0.5
47
1
The
maximum
exposure
level
is
the
highest
level
estimated
based
on
the
Hoerger
and
Kenega
nomograph
as
modified
by
Fletcher,
1994.
For
scenarios
with
single
applications,
the
maximum
level
is
the
concentration
immediately
after
the
treatment.
For
scenarios
with
multiple
applications,
the
maximum
concentration
is
that
which
occurs
immediately
after
the
final
application.
Bolded
RQs
meet
or
exceed
the
acute
risk
LOC
(
0.5)
as
well
as
the
restricted
use
and
endangered
species
LOCs.
;
<
0.1
indicates
no
LOCs
are
exceeded;
0.1
or
higher
suggest
effects
to
endangered
or
threatened
species;
0.2
or
higher
indicates
use
pattern
should
be
considered
for
restricted
use
The
results
of
the
risk
screen
indicate
acute
LOCs
for
risk,
restricted
use
and
endangered
species
are
exceeded
for
birds
at
application
rates
above
1
lb
ai
/
acre,
and
for
mammals
at
all
application
rates.

Although
soil
applications
are
intended
to
be
applied
to
bare
soil,
the
risk
quotients
do
include
residues
on
grass
and
broad
leaf
plant
material.
Not
only
does
this
represent
risk
that
might
occur
from
contaminated
vegetation
inadvertently
left
in
the
fields
at
the
time
of
treatment,
but
also
compensates
for
not
being
able
to
address
such
additional
routes
of
exposure
as
dermal,
inhalation
or
drinking
contaminated
water.
Within
fields
at
the
time
of
planting,
vegetation
is
expected
to
be
sparse,
thereby
reducing
exposure
and
risk;
however,
the
vegetation
on
the
field
margins
will
receive
drift
from
both
ground
and
aerial
applications.
Furthermore,
many
of
disulfoton
 
s
soil
applied,
soil
incorporated
ground
applications
are
side
dressings
to
emergent
crops
such
as
potatoes
and
cotton.
In
those
instances,
residues
do
appear
on
the
under
story
of
the
crop
and
any
weeds
that
are
not
incorporated
(
especially
those
at
the
field
edge)
.
The
primary
food
items
remaining
in
tilled
fields
are
seeds
and
invertebrates.
Insect
residue
were
not
estimated
using
the
nomograph,
however,
for
screening
purposes,
residues
on
insects
may
be
similar
to
seeds
and
broad
leafs,
depending
on
the
size
of
the
insects.

Another
source
of
uncertainty
in
the
acute
risk
assessment
for
mammals
is
the
credibility
of
the
1
day
LC50
values
derived
from
the
rat
LD50
of
1.9
mg/
kg
when
comparing
the
range
of
the
1
day
LC50s
(
2­
12.7
ppm)
to
the
rat
LC50
(
320
ppm
95%
CI
[
0
­
infinity
]
)
for
demeton.
Demeton
is
an
active
ingredient
that
consists
of
a
mixture
of
two
isomers
­
­
demeton
­
S
and
demeton­
O
in
a
ratio
of
65:
35.
Demeton­
O
is
structurally
identical
to
the
oxygen
analog
of
disulfoton.
The
following
tables
illustrate
the
toxicological
similarity
between
demeton
and
disulfoton.

48
Table
30.
Toxicity
of
Demeton
to
Birds
and
mammals
Species
LC50
95%
CI
Source
(
ppm)

Mallard
598
488­
733
Hill
1975
Bobwhite
quail
596
472­
768
Hill
1975
Japanese
quail
275
218­
345
Hill
1986
Ring­
necked
665
572­
773
Hill
1975
Pheasant
Rat
319
0­
infinity
McCaan
1981
LD50
(
mg/
kg)

Rat
­
male
6.2
Gaines
1969
Rat­
female
2.5
Gaines
1969
Red­
wing
Blackbird
2.37­
22.0
a
Schafer
1983
Table
31.
Toxicity
of
Disulfoton
to
Birds
and
mammals
Species
LC50
95%
CI
Source
(
ppm)

Mallard
510
415­
625
Hill
1975
Bobwhite
quail
715
617­
827
Hill
1975
Japanese
quail
334
275­
405
Hill
1986
Ring­
necked
634
547­
737
Hill
1975
Pheasant
LD50
95%
CI
(
mg/
kg)

Rat
­
male
6.82
5.9­
7.8
Gaines
1969
Rat­
female
2.3
1.7­
3.1
Gaines
1969
Red­
wing
Blackbird
3.2
1.8­
5.6
Schafer
1983
a
Range
of
LD50
values
obtained
in
multiple
studies
49
The
above
data
suggests
a
very
similar
toxicity
profile
for
demeton
and
disulfoton.
Therefore,
one
might
consider
disulfoton
 
s
rat
dietary
LC50
to
be
approximately
320
ppm.
Unfortunately,
there
is
uncertainty
for
this
assumption
due
to
the
extremely
wide
95%
CI
for
demeton
 
s
rat
dietary
LC50
study­
­
zero
to
infinity.
Even
when
allowing
for
the
possibility
the
LC50
is
320
ppm
would
mean
foliar
applications
of
1.0
lb
ai/
A
applied
more
than
once
would
exceed
the
acute
risk
LOC­
­
especially
for
herbivores.
However,
higher
rates
of
soil
directed
sprays
applied
by
ground
equipment
would
not
exceed
the
acute
risk
for
herbivores.

The
following
table
presents
a
screening
level
chronic
risk
assessment
for
both
birds
and
mammals.
The
toxicity
values
used
in
the
table
are
the
NOAEL
from
the
avian
reproduction
study
(
37
ppm)
and
the
mammal
2­
generation
rat
reproduction
study
(
0.8
ppm)
.
Both
peak
EECs
and
time
weighted
averages
of
EECs
based
on
Fletcher
maximum
residues
are
used
to
calculate
risk
quotients.
The
peak
EEC
is
shown
only
for
short
grass,
since
that
would
represent
the
highest
level.
The
time
weighted
averages
of
maximum
EECs
are
calculated
by
dissipating
maximum
residues
over
30­
days
and
averaging
the
daily
residues.

50
Table
32.
Avian
and
Mammal
Chronic
Risk
Quotients
based
on
peak
(
for
short
grass)
and
maximum
30
day
average
levels.
Assuming
an
avian
NOAEL
of
37
ppm
(
Bobwhite)
,
a
mammal
NOAEL
of
0.8
ppm
and
a
3.3­
day
halflife
Nongranular
Use
Scenarios
30­
day
Maximum
Average
EEC
in
ppm
1
and
RQs
AVIAN
and
MAMMALS
CHRONIC
RQs
(
EEC
/
NOAEL)

short
grass
(
peak
residue)
broad
leaf
long
grass
seeds/
fruit
Tobacco
;
soil
(
ground)
;
4
lbs
ai/
acre;
1
appl
per
season
EEC
AVIAN
RQ
MAMMAL
RQ
168
(
960)
94
77
10
4.5
(
25)
210
(
1200)
2.5
117
2
96
0.2
12
Beans;
soil
;
2
lbs
ai/
acre;
1
appl
per
season
EEC
AVIAN
RQ
MAMMAL
RQ
84
(
480)
47
38
5
2.2
(
13)
105
(
600)
1.2
58
1
47
0.1
6
Broccoli
and
wheat;
soil;
1
lbs
ai/
acre;
1
appl
EEC
AVIAN
RQ
MAMMAL
RQ
42
(
240)
23
19
2.6
1
(
6)
52
(
300)
0.6
28
0.1
23
<
0.1
3
Potato;
soil
(
ground)
;
4
lbs
ai/
acre;
2
appl
per
season;
14
day
interval
EEC
AVIAN
RQ
MAMMAL
RQ
331(
1010)
186
152
20
8.9
(
27)
413
(
1262)
5
232
4
190
0.5
25
Pecans
&
potatoes;
(
aerial/
ground)
;
1
lb
ai/
acre;
3
appl
per
season;
14­
day
interval
(
Cotton;
soil
(
ground)
;
1
lb
ai/
acre;
3
appl
per
season;
21­
day
interval:
:
should
have
slightly
lower
risk
due
to
less
off
site
distribution
of
spray
and
peak
&
average
residues
are
lower)
EEC
AVIAN
RQ
MAMMAL
RQ
88
(
253)
49
40
5
2.4
(
6.8)
110
(
316)
1.3
61
1
50
0.1
6
Sorghum;
soil
(
aerial/
ground)
;
1
lb
ai/
acre;
2
appl
per
season;
14­
day
interval
(
Barley;
foliar
(
aerial/
ground)
;
1.0
lb
ai/
acre;
2
appl
per
season;
21­
day
interval:
should
have
slightly
lower
risk
off
site,
since
peak
and
average
residues
are
lower;
however,
on
site
the
risk
may
be
higher
due
to
crop
foliage
being
sprayed
directly)

(
Spring
wheat;
foliar
(
aerial/
ground)
;
0.75
lb
ai/
acre;
2
appl
per
season;
30­
day
interval:
should
have
slightly
lower
risk
off
site,
since
peak
and
average
residues
are
lower;
however,
on
site
the
risk
may
be
slightly
higher
due
to
crop
ed
directly)
EEC
AVIAN
RQ
MAMMAL
RQ
82
(
252)
46
38
5
2
(
6.8)
102
(
315)
1.2
57
1
47
0.1
6
per
season.

foliage
being
spray
51
Table
32.
Avian
and
Mammal
Chronic
Risk
Quotients
based
on
peak
(
for
short
grass)
and
maximum
30
day
average
levels.
Assuming
an
avian
NOAEL
of
37
ppm
(
Bobwhite)
,
a
mammal
NOAEL
of
0.8
ppm
and
a
3.3­
day
halflife
Nongranular
Use
Scenarios
30­
day
Maximum
Average
EEC
in
ppm
1
and
RQs
AVIAN
and
MAMMALS
CHRONIC
RQs
(
EEC
/
NOAEL)

Sorghum;
foliar
(
aerial/
ground)
;
0.5
lb
ai/
acre;
3
appl
per
season;
14­
day
interval
EEC
44
(
126)
24.9
20
2.
7
1.2
(
3.4)
55
(
157)
0.6
31
0.5
25
<
0.1
3
(
Cotton;
foliar
(
aerial/
ground)
;
0.5
lb
ai/
acre;
3
appl
per
season;
21­
day
interval:
should
have
slightly
lower
risk
since
peak
and
average
residues
are
lower
)
AVIAN
RQ
MAMMAL
RQ
1
The
exposure
level
is
based
on
the
maximum
level
for
each
vegetation
category
in
the
Hoerger
and
Kenega
nomograph
as
modified
by
Fletcher,
1994.
The
30­
day
average
is
the
average
of
each
daily
residue
value
on
the
food
item
dissipated
using
a
3.3
day
halflife.
For
uses
with
multiple
applications,
each
subsequent
application
deposits
(
adds)
another
maximum
residue
to
the
residue
remaining
from
the
previous
application(
s)
and
that
maximum
residue
is
dissipated
over
time,
a
total
of
30
days.
Bolded
RQs
meet
or
exceed
the
chronic
risk
LOC
(
1)

The
above
two
risk
assessment
tables
were
derived
from
exposure
estimates
based
on
maximum
Fletcher
residue
values.
The
risk
screen
did
not
differentiate
between
foliar
treatments
and
soil
applications.
It
is
recognized
that
applications
to
bare
soil,
while
not
precluding
residues
on
vegetation
in
and
around
the
field,
probably
reduce
the
opportunity
and
extent
of
exposure.
This
would
be
significant
to
both
the
acute
risk
and
chronic
risk.
The
following
discussion
reports
the
results
of
two
field
residue
monitoring
studies
(
MRID
411169­
01
and
41201801)
reflecting
the
difference
in
exposure
for
liquid
formulations
of
disulfoton
associated
with
foliar
and
soil
applications.

Exposure
from
aerial
applications
to
foliage
Disulfoton
as
liquid
Di­
syston
8E
was
aerially
applied
to
potatoes
3
times
at
1
lb
ai/
acre
in
Michigan
(
MRID
41201801)
.
Potato
foliage
was
collected
from
five
treated
fields;
6
sample
stations
in
each
field.
Samples
were
collected
the
day
before
and
the
day
after
each
of
the
three
treatments,
and
then
on
day
7
and
14
after
the
third
(
final)
treatment.
Residues
on
noncrop
vegetation
adjacent
to,
and
invertebrates
in,
treated
fields
were
also
measured.
Samples
were
collected
the
day
after
each
of
three
aerial
applications
of
1
lb
ai/
acre
and
7
days
after
the
third
(
last)
application.
The
following
table
shows
the
peak,
mean
and
upper
bound
of
the
95
%
confidence
interval
residue
values
of
all
fields
after
each
treatment.

52
Table
33.
The
highest
mean,
95
%
confidence
interval
(
CI)
and
peak
residues
reported
during
the
residue
monitoring
of
terrestrial
compartments
following
3
aerial
applications
of
Di­
syston
8E
at
1.0
lbs
ai/
A
to
potato
fields.

Use
Rate
Applic.
potato
foliage
off­
site
non­
target
invertebrates
in
or
Number
(
mean
residues
ppm)
vegetation
(
mean
near
treatment
site
residues
ppm)
(
mean
residues
ppm)

1
9­
59
(
95%
CI)
7.1
1.6
2
18­
78
(
95%
CI)
25
2.7
3
20­
60
(
95%
CI)
9.3
4.5
for
all
upper
95%
CI=
71
upper
95%
CI=
11
1
lb
ai/
acre
(
at
6­
10
day
intervals)
upper
95%
CI=
78
mean=
41
peak=
105
treatments
mean
=
14
peak
=
152
mean
=
3
peak
=
16
As
will
be
discussed
these
results
appear
to
clearly
support
Fletcher
mean
values
for
broad
leaves.
The
potato
foliage
was
sprayed
directly
and
the
mean
of
41
ppm
for
all
treatments
was
only
slightly
less
than
Fletcher
 
s
mean
for
broad
leaves
(
45
ppm
for
a
single
application
and
47
for
3
applications)
.
Though
the
lower
bound
95%
CI
for
application
#
1
was
9
ppm
(
well
below
a
single
application
mean
of
45
ppm)
,
the
upper
bound
95%
CI
of
78
ppm
for
application
#
2
was
1.7
times
higher
than
Fletcher
 
s
mean
of
47
ppm
for
3
applications.
.
The
peak
on
the
targeted
potato
leaves
(
105
ppm)
was
less
than
Fletcher
 
s
maximum
for
broadleaves
(
135
ppm
for
a
single
application
and
142
ppm
for
3
applications)
.
Nevertheless
the
peak
residue
(
152
ppm
in
application
#
2)
for
vegetation
in
the
adjacent
areas
was
greater
than
Fletcher
 
s
maximum
for
both
a
single
and
for
3
applications.
Wind
direction
at
the
time
of
application
may
account
for
the
seeming
contradicting
location
of
the
peak
values.
Approximately
50%
of
the
time
the
wind
was
moving
away
from
the
direction
of
the
within
field
sampling
station
and
approximately
40%
of
the
time
the
wind
direction
was
away
from
the
sample
station
just
outside
the
field
perimeter.
These
monitoring
results,
coupled
with
those
for
azinphos
methyl
applied
to
apple
orchards
(
MRID
411397­
01
&
411959­
01)
,
support
EFED
 
s
assumption
that
foliar
residues
resulting
from
both
single
and
multiple
applications
to
foliage
are
estimated
reasonably
well
using
Fletcher
values
in
a
dissipation
model.

Concerning
the
residues
on
invertebrates
(
peak
of
16
ppm
and
an
upper
bound
mean
95%
CI
of
11
ppm)
,
it
is
acknowledged
that
an
assumed
direct
application
did
not
produce
residues
equal
to
those
on
broadleaves
(
theoretically
reflective
of
small
insects)
,
but
did
compare
favorably
with
Fletcher
 
s
estimates
for
large
insects
(
maximum
of
16
ppm
and
a
mean
of
7
ppm
for
3
applications)
.
The
question
arises
as
to
whether
the
sample
pool
consisted
of
 
small
 
or
 
large
 
53
invertebrates.
Furthermore,
some
of
the
individuals
comprising
the
sample
may
have
been
on
the
underside
of
a
leaf
at
the
time
of
application
and
only
acquired
residues
from
contacting
contaminated
soil
or
leaves.
Whereas
those
individuals
(
especially
the
potato
beetle)
sprayed
directly
had
died.
These
individuals
contained
higher
residues,
but
were
not
part
of
the
pool.
Exposure
from
ground
applications
sprayed
to
soil
A
residue
monitoring
study
was
conducted
in
potato
fields
in
Michigan
(
MRID
411189­
01)
.
Disulfoton
was
applied
at
3
lb
ai/
A
as
an
in­
furrow
spray
application
and
again
as
a
side
dressing
after
6­
7
weeks.
Invertebrates,
crop
and
other
vegetation,
and
soil
were
sampled
within
24
hours
after
both
applications.
Invertebrates
were
collected
in
grids
of
pitfall
traps
in
five
fields,
and
potato
beetles
were
collected
on
foliage
by
sampling
stations.
Soil
samples
were
collected
from
the
soil
surface
to
a
depth
of
2­
3
cm.
Vegetation
was
available
for
sampling
only
after
the
second
application.
Mean
and
maximum
residue
values
are
found
in
the
following
table.
The
limit
of
detection
was
0.09
ppm.

Table
34.
Highest
mean
and
(
maximum)
residues
reported
during
the
residue
monitoring
of
terrestrial
compartments
following
2
soil
applications
by
ground
equipment
of
Di
syston
8E
at
3.0
lbs
ai/
A
Application
Invertebrates
Soil
Edge
of
field
Potato
Foliage
(
ppm)
(
ppm)
vegetation
(
ppm)
(
ppm)

1
(
in
furrow)
0.3
(
0.9)
0.19
(
1.8)
0.2
(
0.9)
4.0
(
26)
*

2
(
side
dressing)
0.4
(
upper
95%
2.9
(
upper
95%
3.5
(
upper
95%
8.0
upper
95%
CI=
0.6)
1.8
14)
22
CI=
11)
54
CI=
16)
44
*
Just
prior
to
2
nd
application
In
contrast
to
foliar
applications,
ground
applications
to
soil
result
in
residues
far
below
those
predicted
in
EFED'
S
initial
screen
using
Fletcher
values.
However
it
is
noted
(
especially
for
systemic
pesticides)
,
residues
are
found
in
food
items
of
non
target
organisms.
In
addition,
as
was
previously
stated,
compensation
must
be
made
for
the
condition
of
a
field
(
the
vegetation
and
invertebrates
in
the
field
at
the
time
of
application)
and
other
routes
of
exposure
besides
ingestion
of
food.
Mammals
appear
to
be
at
risk
both
acutely
and
chronically
from
soil
applications
(
particularly
side
dressing)
.
The
peak
and
mean
residues
in
all
media,
except
for
invertebrates,
exceed
the
the
extrapolated
1
day
LC50'
s
(
ranging
for
2
to
12.7
ppm)
and
the
chronic
NOAEC
(
0.8
ppm)
.
The
Agency
acknowledges
that
the
extrapolated
mammalian
1
day
LC50s
for
disulfoton
may
exaggerate
the
actual
acute
risk.

Risks
from
foliar
treatments
Tests
were
conducted
by
the
Denver
Wildlife
Research
Center
(
Evans
et
al.
1970;
MRID
54
413591­
01)
to
examine
the
feasibility
of
using
foliar
applications
of
disulfoton
to
control
jackrabbits.
Although
few
details
of
the
tests
were
provided,
some
information
was
gathered
on
risks
to
wildlife
from
foliar
applications
of
disulfoton.

Unspecified
numbers
of
jackrabbits
and
cottontail
rabbits
were
introduced
into
enclosed
plots
six
hours
after
foliar
application
to
barley
plants
(
12
days
post
emergence)
at
rates
of
1,
2,
5,
or
25
lb
ai/
A.
None
of
the
cottontails
died.
No
jackrabbit
mortality
was
reported
for
the
1
lb
ai/
A
application,
but
mortality
was
100%
at
rates
of
2,
5,
and
25
lb
ai/
A.
Additional
tests
were
then
conducted
in
enclosures
planted
with
barley,
alfalfa,
wheat,
or
range
grasses
treated
with
a
foliar
application
of
2
lb
ai/
A.
Unspecified
numbers
of
jackrabbits,
cottontails,
pigmy
rabbits,
domestic
rabbits,
wild
and
game
farm
pheasants,
and
mallards
were
introduced
post­
spray
and
exposed
for
anywhere
from
0.5
to
13
days.
Most
or
all
jackrabbits
died;
but
no
mortality
of
other
species
was
reported.
Cholinesterase
levels
were
reported
as
normal
for
cottontails,
partridge,
sage
grouse,
and
pheasants.

Jackrabbits
killed
on
spray
plots
in
the
pen
tests
also
were
fed
to
unspecified
numbers
of
coyotes,
dogs,
golden
eagles,
a
great­
horned
owl,
and
a
red­
tailed
hawk.
The
number
of
jackrabbits
consumed
and
their
residue
levels
were
not
reported.
Commercial
mink
also
were
fed
digestive
tracts,
eviscerated
carcasses,
and
uneviscerated
carcasses
of
jackrabbits
killed
on
2
lb
ai/
A
spray
plots.
All
secondary
consumers
fed
continuously
for
anywhere
from
3
to
30
days
with
no
mortality,
although
some
ChE
depression
was
noted.
In
conclusion,
it
appears
that
foliar
applications
up
to
1.0
lb
ai/
A
(
unless
applied
3
or
more
times
at
intervals
of
less
than
10
days)
will
not
result
in
mortality
to
non
rodents.

Because
dietary
LC50
values
for
birds
are
in
the
range
of
333
to
827
ppm,
EFED
initially
concluded
that
residues
at
these
levels
are
not
likely
to
be
a
significant
acute
risk
to
birds.
More
will
be
said
abut
the
uncertainty
of
this
conclusion
in
the
risk
characterization
section.
However
there
is
a
potential
for
chronic
effects
to
birds
since
the
NOAEC
of
37
is
exceeded
by
the
peak
residues
found
in
crop
foliage
(
44
ppm)
and
non
crop
vegetation
(
54
ppm)
along
the
field
borders.
Given
the
fact
that
the
LOAEC
(
78
ppm
for
bobwhite
quail)
is
only
slightly
above
the
field
residues
there
is
uncertainty
as
to
what
duration
of
exposure
will
produce
an
adverse
reproductive
effect
in
birds.
Furthermore
some
endpoints
not
examined
under
laboratory
conditions
could
be
negatively
impacted
under
field
conditions.
These
end
points
could
include
successful
mating,
nesting
behavior
or
care
of
young.
Adverse
impact
may
occur
either
after
a
brief
exposure
to
concentrations
at
the
NOAEC
level
or
a
longer
period
at
even
lower
levels.

ii.
Risk
from
Granular
Formulations
of
Disulfoton
Birds
and
mammals
may
be
exposed
to
granular
pesticides
ingesting
granules
when
foraging
for
food
or
grit.
They
also
may
be
exposed
by
other
routes,
such
as
by
walking
on
exposed
granules
or
drinking
water
contaminated
by
granules.
The
number
of
lethal
doses
(
LD50s)
that
are
available
within
one
square
foot
immediately
after
application
(
LD50s/
ft
2)
is
used
as
the
risk
quotient
for
granular/
bait
products.
Risk
quotients
are
calculated
for
three
separate
weight
class
of
animals:
1000
g
(
e.
g.
,
waterfowl
or
medium
sized
mammal)
,
180
g
(
e.
g.
,
upland
gamebird
or
55
small
mammal)
,
and
20
g
(
e.
g.
,
songbird
or
very
small
mammal)
.

The
acute
risk
quotients
for
broadcast
applications
of
granular
products
are
tabulated
below.

Table
35.
Avian
and
Mammal
Acute
Risk
Quotients
for
Granular
Products
(
Broadcast)
Based
on
a
Mallard
LD50
of
6.54
mg/
kg
and
a
rat
LD50
of
1.9
mg/
kg.

LD50s
per
animal
are
calculated
by
multiplying
the
weight
of
the
animal
(
kg)
by
the
LD50
in
mg/
kg.

0.
020
Kg
(
20
g)
bird
LD50=
0.
13mg
per
bird
Mammal
LD50=
0.
038mg
per
mammal
0.
180
Kg
(
180
g)
bird
LD50=
1.
17
mg
per
bird
Mammal
LD50=
0.
34mg
per
mammal
1.
00
Kg
(
1000
g)
bird
LD50=
6.
54
mg
per
bird
Mammal
LD50=
1.
9mg
per
mammal
Site/
Application
Method/
Rate
in
lbs
ai/
A
Mammal
or
Bird
Body
Weight
(
g)
Mammal
Acute
RQ
1
(
LD50/
ft
2
)
Avian
Acute
RQ
1
(
LD50/
ft
2
)

Sorghum
or
Barley
unincorporated
1
(
10.41
mg/
sq
ft)
20
273
a
79
a
1
(
10.41
mg/
sq
ft)
180
30
a
8
a
1
(
10.41
mg/
sq
ft)
1000
5
a
1.
5
a
1
RQ=
mg
per
sq
ft
/
LD50
per
animal
mg/
sq
ft
=
(
app
rate
[
lb
ai
per
acre
]
*
453,590
[
mg
per
lb
]
)
/
43,560
[
sq
ft
per
acre
]
LD50
per
animal
=
LD50
(
mg/
kg)
*
wt
(
kg)
a=
acute
risk,
restricted
use
and
endangered
species
LOCs
have
been
exceeded
The
results
of
this
risk
screen
indicate
that
for
broadcast
applications
of
granular
products,
avian
acute
risk,
restricted
use,
and
endangered
species
levels
of
concern
are
exceeded
at
application
rates
equal
to
or
above
1.0
lb
ai/
A.

56
57
The
acute
risk
quotients
for
banded
or
in­
furrow
applications
of
granular
products
are
as
follows:

Table
36.
Avian
and
Mammal
Acute
Risk
Quotients
for
Granular
Products
(
Banded
or
In­
furrow)
Based
on
a
Mallard
LD50
of
6.54
mg/
kg
and
a
rat
LD50
of
1.9
mg/
kg.

LD50s
per
animal
are
calculated
by
multiplying
the
weight
of
the
animal
(
kg)
by
the
LD50
in
mg/
kg.

0.
020
Kg
(
20
g)
bird
LD50=
0.
13mg
per
bird
Mammal
LD50=
0.
038mg
per
mammal
0.
180
Kg
(
180
g)
bird
LD50=
1.
17mg
per
bird
Mammal
LD50=
0.
34mg
per
mammal
1.
00
Kg
(
1000
g)
bird
LD50=
6.
54mg
per
bird
Mammal
LD50=
1.
9mg
per
mammal
Site/
method
oz
ai
per
1000
ft
of
row
Band
Width
%
granules
left
on
surface
after
soil
incorp.
Exposure
Concentration
mg
ai/
sq
ft
RQ
(
LD50
/
sq
ft)
AVIAN
MAMMAL
20
gram
animal
180
gram
animal
1000
gram
animal
Tobacco/
Banded
/
Incorporated
6
0.5
15
51
avian
392a
43a
7a
(
4.0
lb
ai/
A)
mammal
1342a
150a
26a
Potatoes/
In
furrow
/
Incorporated
3.45
(
3.0
lb
ai/
A)
0.5
1
1.9
avian
15a
1.6a
0.3b
mammal
51a
5.7a
1.0a
Potatoes/
banded
/
Incorporated
3.45
(
3.0
lb
ai/
A)
0.5
15
29
avian
225a
25a
4.5a
mammal
763a
85a
15.2a
Vegetable
(
cole
crops,
etc.
)
/
banded,
incorporated
1.1
0.
5
15
9.36
avian
72a
8a
1.4a
(
0.97
lb
ai/
A)
mammal
246a
27a
4a
1
RQ=
mg
per
sq
ft
/
LD50
per
animal
mg/
sq
ft
=
[
(
oz
ai
per
1000
ft
*
28349
mg/
oz)
]
[
%
%
unincorporated
(
decimal)
/
bandwidth
(
ft)
*
1000
ft
]
LD50
per
animal
=
LD50
(
mg/
kg)
*
wt
(
kg)
a=
acute
risk,
restricted
use
and
endangered
species
LOCs
have
been
exceeded
b=
restricted
use
and
endangered
species
LOCs
have
been
exceeded
58
Table
37.
Avian
and
Mammal
Acute
Risk
Quotients
for
Granular
Products
Based
on
a
Mallard
LD50
of
6.54
mg/
kg
and
a
rat
LD50
of
1.9
mg/
kg.

LD50s
per
animal
are
calculated
by
multiplying
the
weight
of
the
animal
(
kg)
by
the
LD50
in
mg/
kg.

0.
020
Kg
(
20
g)
bird
LD50=
0.
13mg
per
bird
Mammal
LD50=
0.
038mg
per
mammal
0.
180
Kg
(
180
g)
bird
LD50=
1.
17mg
per
bird
Mammal
LD50=
0.
34mg
per
mammal
1.
00
Kg
(
1000
g)
bird
LD50=
6.
54mg
per
bird
Mammal
LD50=
1.
9mg
per
mammal
Site/
method
lbs
ai/
acre
Band
Width
%
granules
left
on
surface
after
soil
incorp.
Exposure
Concentration
mg
ai/
sq
ft
RQ
(
LD50
/
sq
ft)
AVIAN
MAMMAL
20
gram
animal
180
gram
animal
1000
gram
animal
Rasberries/
Banded
/
Incorporated
11.75
oz
ai/
1000
ft
(
8
lb
ai/
A)
2
15
25
avian
192a
21a
3.8
mammal
657a
73a
13a
Christmas
trees
/
spot
treatment
broadcast
(
Sec
3)
3.75
oz
prod/
tree
with
1.5
inch
diam
at
4
ft.

0.562
oz
ai
/
tree(
~
2
sq
ft)
1700
trees/
A
(
59.7
lbs
ai/
A)
100
7966b
avian
61276a
6808a
1218a
mammal
209631a
23429a
4193a
Christmas
trees
/
spot
treatment
broadcast
(
North
Carolina
24
C)
5
gr
product
per
tree
0.026
oz
ai
/
tree(
~
2
sq
ft)
1700
trees/
A
(
2.
76
lbs
ai/
A)
100
368b
avian
2830a
314a
56a
mammal
9684a
1082a
193a
1
RQ=
mg
per
sq
ft
/
LD50
per
animal
mg/
sq
ft
=
[
(
oz
ai
per
1000
ft
*
28349
mg/
oz)
]
[
%
%
unincorporated
(
decimal)
/
bandwidth
(
ft)
*
1000
ft
]
LD50
per
animal
=
LD50
(
mg/
kg)
*
wt
(
kg)
a=
acute
risk,
restricted
use
and
endangered
species
LOCs
have
been
exceeded
b=
estimated
by
:
(
oz
ai/
tree)
(
28349
mg/
oz)
/
2
sq
ft/
tree
The
disulfoton
15G
(
15%
ai)
granule
is
applied
in
cotton,
grains,
sorghum,
peanuts,
soybeans,
tobacco,
coffee,
nonbearing
fruit
trees,
pecans,
vegetables,
flowers,
shrubs,
trees,
and
ground
cover.
The
results
of
this
screening
level
risk
assessment
indicate
that
for
both
birds
and
mammals
acute
risk,
restricted
use,
and
endangered
species
levels
of
concern
are
exceeded
for
banded
and
in­
furrow
applications
of
granular
products
at
registered
maximum
application
rates
equal
to
or
above
the
lowest
rate
of
1.1
oz
ai/
1000
ft.
Granules
may
be
intentionally
consumed
as
grit,
mistaken
for
seeds,
or
may
be
ingested
if
attached
to
food
items
(
e.
g.
,
earthworms)
.
Even
when
granules
are
incorporated
that
does
not
preclude
exposure
to
birds
and
mammals.
Fisher
and
Best
(
1995)
examined
granule
availability
in
Iowa
cornfields
and
found
that
6%
of
granules
applied
in
banded
treatment
were
available
on
the
soil
surface,
and
granules
were
found
in
gizzards
of
39%
of
256
birds
collected.

The
LD50
per
square
foot
screening
approach
for
granulars
can
be
refined
by
estimating
how
many
disulfoton
granules
might
be
eaten
by
a
bird
in
a
day.
Based
on
field
counts
and
granule
voiding
experiments,
95%
of
the
birds
collected
in
Iowa
cornfields
were
estimated
to
consume
<
18
granules
per
day.
For
the
savannah
sparrow
(
Passerculus
sandwichensis
)
,
median
consumption
was
11
granules
per
day,
with
5%
of
the
individuals
estimated
to
consume
>
23
granules/
day
(
Fisher
and
Best
1995)
.
A
Di­
Syston
15G
granule
weighs
0.083
mg
(
Balcomb
et
al.
1984,
cited
in
MRID
413591­
01)
and
thus
contains
0.01245
mg
ai.
Eleven
granules
would
contain
0.13695
mg
ai.
If
an
adult
savannah
sparrow
weighs
20
g
(
Dunning
1984)
;
then
an
individual
consuming
11
granules
in
a
day
ingests
0.13695
mg
ai
which
equates
to
6.8475
mg
ai/
kg
of
its
body
weight.
Assuming
the
LD50
for
the
sparrow
is
comparable
to
that
for
the
red­
winged
blackbird
(
3.2
mg/
kg)
,
a
sparrow
ingesting
11
granules
would
be
exposed
to
2.14
times
the
theoretical
dose
lethal
to
50%
of
the
population.
In
a
laboratory
study,
10­
20
granules
of
Di­
Syston
15G
were
required
to
kill
one
out
of
five
house
sparrows
(
weighs
28
gr)
and
red­
winged
blackbirds
(
weighs
60
gr)
respectively
(
Balcomb
et
al.
1984)
.
Since
the
test
level
in
the
study
were
1,5,10
and
20
granules;
it
is
possible
the
actual
number
of
granules
required
to
kill
a
house
sparrow
was
from
6
to
9
and
11
to
19
for
the
red­
wing
blackbird.
Disulfoton
granules
may
pose
an
even
greater
risk
to
mammals
than
to
birds.
Mammals
may
not
intentionally
eat
granules,
but
granules
can
be
consumed
if
attached
to
food
items
(
e.
g.
,
soil
invertebrates,
seeds
on
the
ground)
or
mistaken
as
food
items
(
e.
g.
,
seeds)
.
Assuming
an
LD50
of
1.9
mg/
kg
as
for
the
female
rat,
a
20­
g
rodent
would
need
to
ingest
only
0.038
mg
ai
(
1.9
mg
ai
x
0.02
kg
bw)
to
receive
a
dose
lethal
to
50%
of
the
population.
That
dose
could
theoretically
be
obtained
by
eating
3
granules
(
0.038
mg
ai/
0.01245
mg
ai/
granule)
.
The
point
to
emphasize
is
that
for
any
application
described
in
the
above
table,
at
the
time
of
application
and
until
the
granules
disintegrate,
there
are
sufficient
numbers
of
unincorporated
granules
within
a
square
foot
to
cause
mortality
­
­
especially
to
small
birds
and
mammals.
.

Besides
the
intentional
or
inadvertent
consumption
of
granules
by
birds
and
mammals,
additional
oral
exposure
to
disulfoton
is
possible
from
consumption
of
soil
during
the
disintegration
of
the
granules.
Estimates
of
soil
ingestion
by
wildlife
indicate
that
soil
can
comprise
as
much
as
17­
30%
of
the
diet
of
species
of
some
sandpipers
and
woodcock,
presumably
from
consumption
of
soil
organisms
such
as
earthworms,
which
typically
contain
20­
30%
soil
(
Beyer
et
al.
1994)
.
Other
species
reported
with
soil
in
their
diet
include
Canada
geese
(
8%
soil)
,
raccoon
(
9%
soil)
,
armadillo
(
17%
soil)
,
wood
ducks
(
11%
soil)
,
wild
turkeys
(
9%
soil)
,
and
white­
footed
mice
(
Peromyscus
leucopus
)
fed
foods
containing
either
0,
2%
,
5%
,
and
15%
soil
ate
equivalent
amounts
of
food
regardless
of
soil
content
(
Beyer
et
al.
1994)
.
Dermal
contact
of
granules
and
contaminated
soil
also
could
increase
an
individual'
s
exposure.
Disulfoton
is
a
Toxicity
Category
I
pesticide
for
dermal
toxicity
(
LD50
of
3.6
mg/
kg
for
mammals)
,
although
the
importance
of
dermal
exposure
of
birds
and
mammals
is
uncertain
in
the
field.
Lastly,
since
disulfoton
is
systemic,
non
target
organisms
are
exposed
when
ingesting
invertebrates
and
plant
foliage
where
granules
have
been
applied.

A
field
study
conducted
in
potato
fields
in
Washington
indicated
that
application
of
15G
granules
can
cause
mortality
of
birds
and
mammals
(
MRID
410560­
00)
.
The
fields
were
treated
with
two
applications,
each
at
a
rate
of
3
lbs
ai/
A
­
­
one
in
furrow
at
planting
and
one
side
dressing
4
to
6
weeks
later.
Forty­
one
bird
species
and
8
mammal
species
were
observed
in
the
potato
fields
during
the
study.
During
transect
searches,
32
casualties
were
reported.
However,

59
based
on
the
Agency'
s
guidance
for
terrestrial
field
studies
(
EPA
1986)
,
EFED
concluded
that
the
amount
of
area
searched
(
5.5
acres)
was
not
sufficient
and
that
transects
were
too
far
apart
for
adequately
locating
carcasses.
Moreover,
only
2
of
the
32
casualties
were
analyzed
for
disulfoton
residues.
Despite
methodological
problems
with
the
study,
EFED
accepted
it
as
a
core
study
because
it
demonstrated
mortality
to
wildlife
inhabiting
potato
fields
treated
with
15G
granules.
Both
in­
furrow
and
banded
applications
indicate
mortality
may
be
expected
to
occur.
The
table
below
summarizes
the
residue
levels
resulting
from
the
two
soil
incorporated
applications
of
Di­
Syston
15G.

Table
38.
Mean
and
(
maximum)
total
disulfoton
residues
resulting
from
two
applications
of
Di­
Syston
15
G
Application
Invertebrates
Potato
Foliage
(
ppm)
(
ppm)

1
(
in
furrow)
0.14
(
0.41)
n/
a
2
(
side
dressing)
0.9
(
5.2)
7.5
(
25)

Although
these
residues
are
considerably
below
concentrations
anticipated
to
cause
mortality,
when
coupled
with
1)
other
routes
of
exposure­
­
ingestion
of
granules
and
drinking
from
contaminated
puddles
­
­
and
2)
hypersentivity
of
some
non
targets
organisms
(
i.
e.
,
jackrabbits
and
Swainson
 
s
hawks)
some
mortality
is
possible.

The
application
of
granular
formulations
of
disulfoton
to
raspberry
and
Christmas
tree
may
include
hand
operation
­
­
either
dispensing
or
incorporation
of
granules;
consequently
there
is
a
greater
potential
for
granules
to
remain
above
ground.
Although
the
labels
for
Christmas
trees
refers
to
incorporation
or
watering
(
within
48
hours)
usually
incorporation
can
not
be
conducted
and
April
rainfall
rather
than
irrigation
is
generally
relied
upon
to
activate
the
granules.
Therefore
the
granules
may
remain
intact
and
above
ground
for
at
least
several
days.
There
are
several
additional
factors
that
confound
the
amount
and
type
of
exposure
wild
life
may
encounter
from
disulfoton
on
the
granules.
Number
one,
the
distribution
of
the
granules
under
the
drip
line
will
range
from
a
teaspoon
being
fanned
out
in
several
square
feet
or
else
a
side
dressing
along
two
sides
of
each
row
of
trees.
Number
two,
present
cultural
practices
include
leaving
vegetation
between
the
rows
and
under
the
drip
line.
This
vegetation
may
obscure
an
animal
 
s
view
of
granules
that
have
sifted
through
the
cover
or
if
moist,
allow
the
granule
to
adhere
to
the
leaf
surface
and
be
consumed
by
herbivores.
Number
three,
after
a
rainfall
the
granules
will
dissolve
and
residues
of
disulfoton
will
appear
in
puddles
and
be
taken
up
in
vegetation.
In
light
of
these
factors
there
is
a
high
degree
of
uncertainty
as
to
the
degree
of
risk
to
wild
life.

Christmas
tree
farms
and
the
adjacent
areas
­
­
forests
and
or
pasture
 
provide
excellent
habitat
for
a
great
variety
of
wild
life.
The
North
Carolina
Christmas
Tree
community
has
submitted
numerous
testimonials
emphasizing
the
ever
increasing
numbers
and
diversity
of
wild
life
.
This
includes
game
animals
such
as
turkey
rearing
young
amidst
the
trees,
song
birds,
rodents
and
foxes.
Although
this
information
is
intended
to
suggest
there
is
little
or
no
negative
impact
from
not
only
disulfoton,
but
other
pesticides
or
cultural
practices
as
well,
the
Agency
would
prefer
to
receive
documented
surveys
or
research
before
making
a
final
determination.

60
Chronic
Risk
from
Granular
Formulations
Estimating
long
term
exposure
from
granular
applications
is
difficult,
since
the
granules
are
not
expected
to
remain
in
tact
over
extended
periods.
The
chemical
is
expected
to
become
distributed
in
the
soil,
as
the
granules
dissipate.
.
However,
given
that
disulfoton
is
chronically
toxic
to
birds
and
mammals
at
low
dietary
concentrations,
granular
applications
may
contribute
to
chronic
risk.

iii.
Insects
Currently,
EFED
does
not
assess
risk
to
nontarget
insects.
Results
of
acceptable
studies
are
used
for
recommending
appropriate
label
precautions.
Disulfoton
and
its
sulfoxide
and
sulfone
metabolites
are
classified
as
highly
toxic
to
the
honeybee
on
an
acute
contact
and
oral
basis,
therefore,
toxicity
label
language
is
required.
Current
labeling
includes
the
appropriate
bee
toxicity
warning
statement.

B.
Risk
to
Nontarget
Freshwater
and
Estuarine
Animals
The
following
table
shows
the
specific
toxicity
values
that
were
used
in
assessing
acute
and
chronic
risk
to
aquatic
and
marine
organisms.
Species
that
demonstrated
ranges
of
sensitivity
were
used,
not
just
the
most
sensitive
species.

61
Table
39.
Toxicity
endpoints
used
in
assessing
risk
of
aquatic
organisms
for
disulfoton
Species
*
Test
Type
Results
(
ppb)
Source
of
Data
Freshwater
Species
Rainbow
trout
Acute
LC50=
1850
40098001
Bluegill
Acute
LC50=
39
00068268
Channel
catfish
Acute
LC50=
4700
40098001
Rainbow
trout
Early
Life
Stage
NOAEC=
220
41935801
Bluegill
Early
Life
Stage*
*
estimated
NOAEC=
4.6
No
study
conducted
Water
flea
Acute
EC50=
13
00143401
Glass
shrimp
Acute
EC50=
3.9
40094602
Stonefly
Acute
EC50=
5
40098001
Water
flea
Reproduction
NOAEC=
0.037
41935802
Marine
Species
Sheepshead
minnow
Acute
LC50=
520
40228401
Sheepshead
minnow
Early
Life
Stage
NOAEC=
16.2
42629001
Sheepshead
minnow
Full
Life
Cycle
EC05=
0.96*
*
*
43960501
Eastern
Oyster
Acute
EC50=
720
40228401
Mysid
Acute
EC50=
100
40071601
Brown
shrimp
Acute
EC50=
15
40228401
Mysid
Life
Cycle
EC05=
2.35*
*
*
43610901
*
The
species
listed
and
used
in
risk
assessment
were
selected
from
the
toxicity
data
because
they
seemed
to
represent
a
distribution
of
sensitivity.
*
*
An
early
life
stage
study
was
not
conducted
with
bluegill.
The
only
freshwater
fish
chronic
study
was
with
rainbow
trout.
In
the
case
of
disulfoton,
rainbow
trout
are
significantly
less
sensitive
than
bluegill.
So
in
an
effort
to
translate
this
difference
in
sensitivity
to
the
chronic
risk
assessment,
a
NOAEC
for
bluegill
was
calculated
based
on
the
ratio
of
acute
toxicity.
The
lowest
rainbow
trout
LC50=
1850
ppb.
The
bluegill
LC50=
39.
The
ratio
of
trout
to
bluegill
is
39/
1850=
0.021.
0.021
X
the
trout
NOAEC
of
220
ppb
=
4.6
ppb.
There
is
uncertainty
in
this
value,
since
it
is
estimated,
and
not
derived
from
an
actual
toxicity
test.
*
*
*
The
study
did
not
produce
a
NOAEC,
however,
the
responses
at
the
different
concentrations
were
plotted
used
to
estimate
the
concentration
at
which
5%
effects
would
be
expected,
or
an
EC05.

Tier
II
estimated
environmental
concentrations
(
EECs)
for
a
variety
of
disulfoton
applications
were
calculated
to
generate
aquatic
exposure
estimates
for
use
in
the
ecological
risk
assessment.
In
the
risk
quotient
tables
below,
both
freshwater
and
marine
species
are
included
in
the
same
table.
The
first
table
presents
the
acute
risk
quotients
based
on
modeling,
the
second
table
presents
the
chronic
risk
quotients.
The
modeling
represents
exposure
in
a
1­
hectare
2­
meter
deep
enclosed
pond
receiving
runoff
and
drift
from
a
10
hectare
treated
field.
This
scenario
is
considered
relatively
conservative,
but
may
not
represent
the
highest
exposure
in
all
cases,
since
water
bodies
can
be
shallower,
and
thus
may
have
higher
exposure
potential.
On
the
other
hand,
many
water
bodies
are
larger,
and
have
flow
that
may
dilute
concentrations.
Long­
term
exposures
are
especially
uncertain
when
applied
to
flowing
streams
and
rivers
and
estuaries
and
62
may
over­
estimate
the
risk.
However,
not
all
estuaries
involve
rapid
exchange
of
water,
so
these
estimates
are
not
automatically
considered
overly
conservative
for
all
estuaries.
.

Table
40.
Acute
risk
quotients
for
freshwater
and
marine
fish
and
invertebrates
.

Acute
risk
quotients;
peak
EEC/
LC50
Use
Pattern
EEC
ppb
Freshwater
surrogate
species
Marine
surrogate
species
fish
invertebrates
fish
invertebrates
LC50
(
ppb)
>
bluegill
39
rainbow
trout
1850
channel
catfish
4700
glass
shrimp
3.9
stonefly
5
water
flea
13
sheepshead
m.
520
brown
shrimp
15
mysid
100
oyster
720
Tobacco
soil
4.0
lb
ai/
a
1
app
per
yr
incorp
2.5
inches
peak
26.7
0.6
<
0.01
<
0.01
6.8
5.
3
2.0
0.05
1.7
0.2
0.
03
Tobacco
soil
(
granular)
4.0
lb
ai/
a
1
app
per
yr
incorp
2.5
inches
peak
18.4
0.
4
<
0.01
<
0.01
4.7
3.
6
1.4
0.03
1.2
0.18
0.02
Potato
foliar
1.0
lb
ai/
a
3
app
at
14
day
int.
not
incorporated
peak
15.0
0.
3
<
0.01
<
0.01
3.8
3.
0
1.1
0.02
1.0
0.1
0.
02
Cotton
soil
1.0
lb
ai/
a
3
app
at
21
day
int.
not
incorporated
peak
14.8
0.
3
<
0.01
<
0.01
3.7
2.
9
1.1
0.02
0.9
0.14
0.02
Barley
foliar
1.0
lb
ai/
a
2
app
at
21
day
int.
not
incorporated
peak
9.2
0.
2
<
0.01
<
0.01
2.3
1.
8
0.7
0.01
0.6
0.09
0.01
Spring
Wheat
foliar
0.75
lb
ai/
a
2
app
at
30
day
int.
not
incorporated
peak
8.9
0.2
<
0.01
<
0.01
2.2
1.
7
0.6
0.07
0.59
0.08
0.01
Potato
soil
4.0
lb
ai/
a
2
app
at14
day
int.
incorp
to
2.5
inches
peak
7.1
0.
18
<
0.01
<
0.01
1.8
1.
4
0.5
0.01
0.47
0.07
<
0.01
Barley
soil
(
granular)
0.83
lb
ai/
a
2
app
at
21day
int.
not
incorporated
peak
7.1
0.
18
<
0.01
<
0.01
1.8
1.
4
0.5
0.01
0.47
0.07
<
0.01
Risk
quotients
exceeding
the
acute
risk
LOC
of
0.5
are
bolded
The
LOC
for
restricted
use
is
0.1
The
LOC
for
endangered
species
is
0.05
The
screening
assessment
results
indicate
that
except
for
the
highest
application
to
tobacco,
the
acute
risk
LOC
has
not
been
exceeded
for
fish.
Estuarine
fish
appear
to
be
a
far
less
risk
than
freshwater
fish.
On
the
other
hand,
the
RQs
for
all
modeled
uses
exceed
the
acute
risk
LOC
for
63
64
fresh
water
invertebrates.
Although
two
of
the
three
test
species
of
estuarine
invertebrates
did
not
suggest
risk,
based
on
the
brown
shrimp,
estuarine
invertebrates
are
at
acute
risk
from
all
modeled
crops.
Especially
for
estuarine
invertebrates
there
is
uncertainty
as
to
the
degree
of
the
acute
risk.

Table
41.
Chronic
risk
quotients
for
freshwater
and
marine
fish
and
invertebrates
.

Chronic
risk
quotients;
ave.
EEC/
NOAEC
or
EC05
Use
Pattern
EEC
ppb
Freshwater
surrogate
species
Marine
surrogate
species
fish
inverteb
rates
fish
inverte
brates
NOAEC
(
ppb)
 
>
bluegill
4.
6
rainbow
trout
220
water
flea
0.
037
sheepshea
d
life
cycle
0.
96
Sheepshead
early
life
st.
16.
2
Mysid
life
cycle
EC05=
2.
35
Tobacco
soil
4.0
lb
ai/
a
1
app
per
yr
incorp
2.5
inches
21­
d
17.9
60­
d
9.9
2
<
0.
1
483
10.3
0.6
7.6
Tobacco
soil
(
granular)
4.0
lb
ai/
a
1
app
per
yr
incorp
2.5
inches
21­
d
12.5
60­
d
6.7
1.4
<
0.
1
337
6.9
0.4
5
Potato
foliar
1.0
lb
ai/
a
3
app
at
14
day
int.
not
incorporated
21­
d
10.4
60­
d
6.9
1.5
<
0.
1
281
7.1
0.4
4.4
Cotton
soil
1.0
lb
ai/
a
3
app
at
21
day
int.
not
incorporated
21­
d
8.0
60­
d
4.9
1
<
0.
1
216
5.1
0.4
3.4
Barley
foliar
1.0
lb
ai/
a
2
app
at
21
day
int.
not
incorporated
21­
d
5.9
60­
d
3.7
0.
8
<
0.1
159
3.8
0.2
2.5
Spring
Wheat
foliar
0.75
lb
ai/
a
2
app
at
30
day
int.
not
incorporated
21­
d
4.5
60­
d
2.6
0.
5
<
0.1
121
2.7
0.1
1.9
Potato
soil
4.0
lb
ai/
a
2
app
at14
day
int.
incorp
to
2.5
inches
21­
d
4.3
60­
d
2.3
0.
5
<
0.1
116
2.4
0.1
1.8
Barley
soil
(
granular)
0.83
lb
ai/
a
2
app
at
21day
int.
not
incorporated
21­
d
5.4
60­
d
3.8
0.
8
<
0.1
145
3.9
0.2
2.2
Risk
quotients
exceeding
the
chronic
risk
LOC
are
bolded
Risk
quotients
for
invertebrates
and
fish
are
based
on
21
and
60
day
EECs
respectively
Both
fish
and
invertebrates
are
likely
to
experience
chronic
effects
based
on
modeled
EECs.
Freshwater
invertebrates
are
at
much
greater
risk
than
fish
or
estuarine
invertebrates.

Risk
to
Freshwater
Organisms
from
the
use
of
Disulfoton
15
on
Christmas
Trees
in
North
Carolina
The
use
of
Disulfoton
15
G
in
Christmas
tree
farms
at
this
time
can
not
be
modeled
for
potential
surface
water
contamination.
EFED
assumes
the
estimated
concentration
for
the
North
Carolina
24
(
c)
use
pattern
­
­
2.75
lbs
ai/
A
unincorporated
­
­
may
be
similar
to
the
values
for
the
single
4.0
lb
ai/
A
incorporated
application
of
granular
disulfoton
to
tobacco.
Based
on
this
assumption
there
is
acute
risk
to
aquatic
invertebrates
and
chronic
risk
to
freshwater
fish
and
aquatic
invertebrates.
Since
this
preliminary
screen
of
the
24(
c)
exceeds
levels
of
concern,
the
Sec
3
use
at
59.7
lbs
ai/
A
would
exceed
(
perhaps
by
20
fold)
the
same
levels
of
concern
for
aquatic
life
and
the
acute
risk
for
fish
as
well.
However,
even
if
the
receiving
body
of
water
was
a
pond
(
as
was
modeled
for
tobacco)
this
assumption
has
uncertainty
because
although
the
Christmas
tree
use
pattern
has
a
lower
rate
and
current
cultural
practices
recommend
maintaining
vegetation
under
the
trees
and
between
the
rows;
nevertheless
the
material
is
not
incorporated.
Therefore
while
the
first
two
conditions
may
reduce
the
estimated
concentrations
below
those
for
tobacco,
the
third
condition
may
increase
the
concentrations.

The
North
Carolina
Christmas
tree
industry
has
provided
information
that
has
contributed
to
a
refinement
of
EFED
 
s
risk
assessment
for
aquatic
organisms
from
Christmas
tree
farming.
Firstly,
the
primary
and
nearly
exclusive
use
site
for
Disulfoton
15
G
on
Christmas
trees
throughout
the
United
States
is
on
Fraser
fir
grown
in
6
counties
in
Western
North
Carolina,
thereby
localizing
the
exposure
and
precluding
any
estuarine
exposure.
Secondly,
the
primary
aquatic
sites
adjacent
to
tree
farms
are
streams,
not
ponds.
Residues
in
these
streams
will
be
lower
and
of
shorter
duration
than
would
be
expected
for
a
pond.
Thirdly,
two
rapid
assessment
macro
invertebrate
surveys
of
streams
in
the
Western
region
of
North
Carolina
have
been
submitted.
The
following
is
a
brief
discussion
of
those
results.

In
the
1998
study
conducted
by
the
North
Carolina
Department
of
Environmental
Health
and
Natural
Resources
(
DEHNR)
,
8
of
11
streams
were
sampled
once
in
May
(
presumably
after
the
April/
May
application
of
disulfoton)
at
one
location.
The
3
other
streams
were
sampled
a
second
time
in
August
as
a
means
to
correct
for
likely
seasonal
changes
in
the
species
composition
of
Ephemeroptera,
Plecoptera
and
Trichoptera
(
EPT)
.
These
three
Orders
of
invertebrates
are
considered
to
be
sentinel
species
indicative
of
overall
water
quality.

In
spite
of
some
concerns
such
as
the
mixed
influence
of
cattle
or
development
along
with
Christmas
tree
farms
and
the
preference
for
a
more
rigorous
study
design
(
i.
e.
residue
analysis
and
more
frequent
sampling)
the
Agency
considered
the
survey
 
s
utility
in
light
of
several
factors:
an
on­
site
visit
in
June
2000;
the
support
for
the
protocol
as
described
in
the
EPA
publication:
EPA
841­
B­
99­
002;
the
nation
wide
use
of
disulfoton
on
Christmas
trees
is
primarily
in
this
region
where
it
has
been
used
for
20
years
and
the
submission
of
a
second
survey
conducted
from
December
1998
through
mid
to
late
summer
1999.

65
The
second
survey
examined
5
sites
 
each
consisting
of
an
area
adjacent
or
downstream
from
a
Christmas
tree
farm
paired
with
its
own
reference
site
(
either
a
station
on
the
same
stream,
but
above
the
tree
farm
or
a
second
stream.
Quantification
­
included
the
total
number
of
insects
and
the
break
out
(
expressed
as
a
%
of
insects)
for
mayflies,
stoneflies,
caddisflies,
riffle
beetles
and
 
other
 
insects.
A
species
list
for
mayflies,
stoneflies
and
caddisflies
along
with
and
index
of
their
sensitivity
and
the
dates
collected
was
provided
for
3
of
the
5
sites.
Data
for
each
of
the
reported
3
pairs
of
sites
were
analyzed
using
ANOVA.

Unlike
the
DEHNR
survey
where
various
communities
(
leaf
packs,
riffles,
banks
and
large
rocks
and
logs)
were
sampled,
only
the
riffle
community
was
sampled.
Like
the
DEHNR
survey,
no
residue
analysis
was
performed
for
any
pesticide
including
disulfoton.
Again
the
researcher
made
the
point
that
the
protocol
seeks
to
detect
whether
an
impact
is
occurring
due
to
the
combination
of
numerous
influences
without
quantifying
the
degree
of
exposure
to
a
specific
chemical(
s)
.

The
Agency
concurs
with
the
investigators
that
when
implementing
(
but
not
limited
to)
conservation
measures
such
as
establishing
ground
cover
throughout
the
farm,
constructing
and
maintaining
the
fewest
number
of
roads
and
bridges,
creating
a
riparian
zone
to
include
vegetation
and
trees
and
employing
Integrated
Pest
Management
practices,
there
appears
to
be
 
.
.
.
.
little
negative
effect
on
the
fauna
of
adjacent
streams.
.
.
.
 
The
slight
negative
effect
that
was
observed
seemed
to
impact
stoneflies
(
Plecoptera)
more
than
the
two
other
orders
 
caddisflies
(
(
Trichoptera)
and
mayflies
(
Ephemeroptera)
­
that
were
the
focus
of
the
survey.

In
summary,
the
two
surveys
suggests
that
when
conservation
measures
associated
with
Christmas
tree
farming
in
the
Western
counties
of
North
Carolina
are
implemented,
there
may
be
only
slight,
short
term
impact
to
aquatic
macro
invertebrates
from
disulfoton
use.
Aquatic
macro
invertebrates
appear
to
have
the
capacity
to
recover
from
any
impact
that
could
be
caused
by
disulfoton
use
on
Christmas
trees
in
Western
North
Carolina.

66
C.
Exposure
and
Risk
to
Nontarget
Plants
Although
Tier
I
terrestrial
and
aquatic
plant
testing
is
required
for
disulfoton
due
to
label
phytotoxicity
warnings,
no
data
on
plant
toxicity
has
been
submitted
at
this
time.
Therefore,
the
risk
to
nontarget
plants
cannot
be
assessed.

5.
Endangered
Species
The
following
endangered
species
LOCs
have
been
exceeded
for
disulfoton:
avian
acute,
avian
chronic,
mammalian
acute,
mammalian
chronic,
freshwater
fish
acute,
freshwater
invertebrate
acute,
freshwater
invertebrate
chronic,
marine/
estuarine
fish
acute,
marine/
estuarine
fish
chronic,
marine/
estuarine
invertebrate
acute,
and
marine/
estuarine
invertebrate
chronic.
Endangered
terrestrial,
semi­
aquatic
and
aquatic
plants
also
may
be
affected,
based
on
label
statements
indicating
phytotoxicity.

The
OPP
Endangered
Species
Protection
Program
(
ESOP)
is
developing
ways
to
protect
endangered
species
from
hazardous
pesticides.
Limitations
on
the
use
of
disulfoton
will
be
required
to
protect
endangered
and
threatened
species,
but
these
limitations
have
not
been
defined
and
may
be
formulation
specific.
EPA
anticipates
that
a
consultation
with
the
Fish
and
Wildlife
Service
may
be
conducted
in
accordance
with
the
species­
based
priority
approach
described
in
the
ESOP.
After
completion
of
consultation,
registrants
will
be
informed
if
any
required
label
modifications
are
necessary.
Such
modifications
would
most
likely
consist
of
the
generic
label
statement
referring
pesticide
users
to
use
limitations
contained
in
county
Bulletins.

6.
Disulfoton
Incident
Reports
There
are
both
bird
and
fish
kills
reported
for
disulfoton.
The
following
are
summaries
of
incidents
reports
available
to
the
Agency.

BIRD
INCIDENTS:
1.
Young
County,
TX,
6/
18/
93.
Eighteen
Swainson
 
s
hawks
were
found
dead
and
one
found
severely
disabled
in
a
cotton
field.
The
cotton
seed
had
been
treated
with
disulfoton
seed
treatment
prior
to
planting,
about
10
days
before
the
birds
were
discovered.
According
to
field
personnel,
no
additional
applications
of
organophosphorus
or
carbamate
pesticides
had
been
made
in
the
vicinity
of
the
field.
Autopsies
revealed
no
signs
of
trauma
or
disease.
Laboratory
analysis
of
the
birds
revealed
insect
material
in
the
gastrointestinal
tracts.
Residue
chemistry
analysis
of
this
material
indicated
the
presence
of
disulfoton
(
approximately
7
ppm)
;
no
other
organophosphorus
or
carbamate
insecticides
were
present.
Apparently,
the
hawks
had
fed
on
insects,
which
had
been
feeding
on
the
young
cotton
plants.
The
systemic
nature
of
the
pesticide
appears
to
have
resulted
in
plant
residues,
which
were
then
taken
up
by
the
insects,
at
levels
high
enough
to
cause
mortality
in
the
hawks.
This
may
be
the
first
documented
incident
of
this
type
of
exposure
in
a
captor
species.
(
L.
Lyon,
Div.
of
Environmental
Contaminants,
U.
S.
Fish
and
Wildlife
Service,
Arlington,
VA.
Presented
at
the
SETAC
18th
annual
meeting,
San
Francisco,
CA,
1997)
.
The
Agency
has
been
able
to
confirm
the
incident
through
personal
communication
with
Stephen
Hamilton,
the
Special
Agent
of
the
U.
S.
Fish
and
Wildlife
in
charge
of
the
investigation,
who
stated
there
was
no
evidence
of
misuse.

2.
Sussex
County,
DE,
4/
26/
91.
Nine
American
robins
found
dead
following
application
of
granular
disulfoton
at
a
tree
nursery.
Corn
and
soybeans
were
also
in
the
vicinity.
No
67
laboratory
results
were
obtained.
Certainty
index
is
probable
for
disulfoton.
(
Incident
Report
No.
I000116­
003)
.

3.
Puerto
Rico,
1/
24/
96.
Six
grackles
fell
dead
from
a
tree
in
the
yard
of
a
private
residence.
A
dead
heron
and
a
dead
owl
were
also
found
in
the
vicinity.
The
use
site
and
method
were
not
reported.
Birds
had
depressed
acetyl
cholinesterase.
Residue
analysis
on
gut
contents
of
one
of
the
grackles
found
disulfoton
residues
of
12.37
ppm
wet
weight.
Certainty
index
of
this
incident
is
highly
probable
for
disulfoton.
(
Incident
Report
No.
I003966­
004)
.

FISH
INCIDENTS
1.
Onslow
County,
NC,
6/
22/
91.
A
fish
kill
occurred
in
a
pond
at
a
private
residence.
The
pond
received
runoff
from
a
neighboring
tobacco
field.
Analysis
of
the
water
in
the
pond
revealed
the
presence
of
disulfoton
and
several
other
pesticides,
including
endosulfan.
Disulfoton
sulfoxide
was
found
in
the
water
at
a
concentration
of
0.32
ppb.
Endosulfan
had
the
highest
concentration
(
1.2
F
g/
L)
,
and
is
toxic
to
fish,
but
disulfoton
cannot
be
ruled
out
as
a
possible
cause
of
death.
No
tissue
analysis
was
conducted.
The
certainty
index
of
this
incident
for
disulfoton
is
 
possible.
 
(
(
Incident
Report
No.
B0000216­
025)
.

2.
Onslow
County,
NC,
4/
29/
91.
A
fish
kill
occurred
in
a
pond,
which
was
adjacent
to
a
tobacco
field
and
a
corn
field.
Rain
followed
the
application
of
pesticide,
and
more
than
200
dead
fish
were
found
floating
in
the
pond.
Water
and
soil
samples
were
collected
within
a
week
after
the
incident.
Several
organophosphorus
pesticides,
as
well
as
atrazine
and
napromide,
were
found
in
all
soil
samples
taken
from
around
the
pipe
that
ran
from
the
field
to
the
pond,
but
none
of
the
samples
contained
detectable
disulfoton.
The
pesticide
applicator
failed
to
follow
packaging
guidance
on
safe
handling
of
the
pesticides.
Additionally,
the
corn
and
tobacco
fields
were
62­
82
feet
uphill
from
the
pond,
which
violates
the
requirement
that
these
pesticides
not
be
applied
within
140
feet
of
a
waterway.
The
certainty
index
for
this
incident
is
 
unlikely
 
for
disulfoton
(
(
Incident
Report
No.
I000799­
004)
.

3.
Johnston
County,
NC,
6/
12/
95.
A
fish
kill
occurred
in
a
commercial
fish
pond.
Crop
fields
nearby
had
been
treated
with
pesticides.
Water,
soil
and
vegetation
samples
were
taken
and
analyzed
for
a
variety
of
pesticides.
Disulfoton,
as
well
as
several
other
pesticides
was
found
in
the
samples.
The
level
of
disulfoton
in
the
vegetation
samples
was
0.2­
2.5
ppm.
The
certainty
index
for
this
incident
is
 
possible
 
for
disulfoton.
.
(
Incident
Report
No.
I003826­
002)
.

4.
Arapahoe
County,
CO,
6/
14/
94.
A
fish
kill
occurred
following
application
of
Di­
Syston
EC.
to
wheat,
which
was
followed
by
a
heavy
rain.
Water
samples
collected
contained
disulfoton
sulfoxide
at
levels
of
29.5­
48.7
ppb,
and
disulfoton
sulfone
at
0.0199­
0.214
ppb.
The
wheat
field
was
located
several
miles
from
the
pond.
The
volume
of
run
off
water
raised
the
level
of
the
pond
fifteen
feet.
In
addition
to
the
rapid
rise
of
the
water
level
there
was
a
large
mass
of
sediment
and
vegetation
that
may
have
resulted
in
a
severe
drop
in
the
Biological
Oxygen
Demand
levels.
The
certainty
index
for
this
incident
is
 
possible
 
for
disulfoton.
.
(
Incident
Report
No.
I001167­
001)
.

Some
of
these
incident
reports
tend
to
support
the
conclusions
of
the
risk
screens
indicating
LOCs
for
acute
risk
are
exceeded.

68
Risk
Characterization
A.
Characterization
of
the
Fate
and
Transport
of
Disulfoton
i.
Water
Exposure
(
a)
Surface
Water
Disulfoton
is
likely
to
be
found
in
runoff
water
and
sediment
from
treated
and
cultivated
fields.
However,
the
fate
of
disulfoton
and
its
degradates
once
in
surface
water
and
sediments,
and
the
likely
concentrations
therein,
cannot
be
modeled
with
a
high
degree
of
certainty
since
data
are
not
available
for
the
aerobic
and
anaerobic
aquatic
degradation
rates.
Surface
water
concentrations
of
disulfoton
and
total
disulfoton
residues
were
estimated
by
using
PRZM3
and
EXAMS
models
using
several
different
scenarios
(
barley,
cotton,
potato,
tobacco,
and
spring
wheat)
.
The
large
degree
of
latitude
available
in
the
disulfoton
labels
also
allows
for
a
wide
range
of
possible
application
rates,
total
amounts,
application
methods,
and
intervals
between
applications.
Considering
the
relatively
rapid
rate
of
microbial
degradation
in
the
soil
(
<
20
day
aerobic
soil
metabolism
half­
life)
and
direct
aquatic
photolysis,
disulfoton
parent
may
degrade
fairly
rapidly
in
surface
water.
However,
peak
concentrations
of
disulfoton
in
the
farm
pond
appear
capable
of
being
quite
high,
with
1­
year­
in
10
peak
surface
water
concentrations
of
7.14
to
26.75
F
g/
L
and
90­
day
concentrations
of
1.73
to
6.87
µ
g/
L
for
the
parent
compound.
The
mean
EECs
of
the
annual
means
of
disulfoton
ranged
from
0.21
to
1.14
µ
g/
L.
Although
there
is
a
lack
of
some
environmental
fate
data
for
the
degradates,
the
assessment
suggests
that
the
degradates
will
reach
higher
concentrations
than
the
parent
because
they
are
more
persistent
and
probably
more
mobile.
The
estimated
peak
concentrations
for
the
total
disulfoton
residues
in
the
farm
pond
ranged
from
15.43
to
58.48
µ
g/
L,
90
day
average
ranged
from
12.20
to
35.30
µ
g/
L,
and
the
mean
of
the
annual
means
ranged
from
3.89
to
9.32
µ
g/
L.
Water
samples
collected
at
the
site
of
a
fish
kill
in
Colorado
contained
D.
sulfoxide
at
levels
of
29.5­
48.7
µ
g/
L,
and
D.
sulfone
at
0.0199­
0.214
µ
g/
L.
The
aerobic
soil
metabolism
studies
show
that
the
maximum
sulfoxide
residues
are
about
58
percent
of
total
radioactive
material,
thus,
the
sulfoxide
concentrations
suggest
that
parent
disulfoton
concentrations
could
range
from
50.8
to
83.9
µ
g/
L.
The
ratio
of
the
disulfoton
sulfoxide
concentration
to
the
average
maximum
disulfoton
concentration
was
higher
(
74%
)
in
the
microcosm
study
(
MRID
#
4356501)
than
in
the
soil
residues
(
58%
)
.

The
estimated
drinking
water
concentrations
(
EDWC)
for
parent
disulfoton
and
total
disulfoton
residues
were
also
determined
using
the
IR
and
PCA
concepts.
The
peak
concentrations
of
disulfoton
in
IR
appear
capable
of
being
quite
high,
with
1­
year­
in
10
peak
surface
water
concentrations
of
7.13
to
44.20
F
g/
L
and
annual
mean
concentrations
of
0.43
to
2.77
µ
g/
L
for
the
parent
compound.
The
mean
EECs
of
the
annual
means
of
disulfoton
ranged
from
0.23
to
1.31
µ
g/
L.
Although
there
is
a
lack
of
some
environmental
fate
data
for
the
degradates,
the
assessment
suggests
that
the
degradates
will
reach
higher
concentrations
than
the
parent
because
they
are
more
persistent
and
probably
more
mobile.
The
estimated
1­
in­
10
year
peak
concentrations
for
the
total
disulfoton
residues
in
the
IR
ranged
from
20.83
to
104.92
µ
g/
L
and
annual
mean
ranged
from
5.10
to
16.25
µ
g/
L,
and
the
mean
of
the
annual
means
ranged
from
2.55
to
10.42
µ
g/
L.
These
values
will
also
be
highly
affected
by
the
value
selected
for
PCA.

Surface­
water
samples
were
collected
in
a
study
to
evaluate
the
effectiveness
of
Best
Management
Practices
(
BMP)
in
a
Virginia
watershed.
Approximately
half
of
the
watershed
is
69
in
agriculture
and
the
other
half
is
forested.
The
detections
of
parent
disulfoton
in
surface­
water
samples
ranged
from
0.037
to
6.11
µ
g/
L
and
fell
within
an
order
of
magnitude
with
the
estimated
environmental
concentrations
(
EECs)
obtained
from
the
PRZM/
EXAMS
models.

Surface­
water
monitoring
by
the
USGS
in
the
NAWQA
(
USGS,
1998)
project
found
relatively
few
detections
of
disulfoton
in
surface
water
with
a
maximum
concentration
of
0.060
µ
g/
L.
As
noted
above
disulfoton
degradates
were
reported
in
surface
water,
when
a
rainfall
event
occurred
following
application
to
wheat,
where
fish
kills
occurred;
pesticide
residue
concentrations
ranged
from
29.5
to
48.7
µ
g/
L
for
D.
sulfoxide
and
0.02
to
0.214
µ
g/
L
(
Incident
Report
No.
I001167­
001)
.

A
search
of
the
EPA
 
s
STORET
(
10/
16/
97)
data
base
resulted
in
the
identification
of
disulfoton
residues
at
a
number
of
locations.
Often
the
values
ranged
from
0.01
to
100.0
F
g/
L
with
most
of
the
values
reported
as
 
actual
value
is
less
than
this
value.
 
Thus,
,
when
a
value
of
100.00
µ
g/
L
is
reported,
it
is
not
known
how
much
less
than
100.0
F
g/
A
the
actual
value
is
known
to
be
less.
Thus
there
is
considerable
uncertainty
surrounding
some
of
the
data
in
STORET.

(
b)
Ground
Water
The
SCI­
GROW
(
Screening
Concentration
in
Ground
Water)
screening
model
developed
in
EFED
was
used
to
estimate
disulfoton
concentrations
in
ground
water
(
Barrett,
1999)
.
SCI
­
GROW
represents
a
"
vulnerable
site"
,
but
not
necessarily
the
most
vulnerable
conditions,
treated
(
here)
with
the
maximum
rate
and
number
of
disulfoton
applications,
while
assuming
conservative
environmental
properties
(
90
percent
upper
confidence
bound
on
the
mean
aerobic
soil
half­
life
of
6.12
days
and
an
average
Koc
value
of
551
mL/
g)
.
The
maximum
disulfoton
concentration
predicted
in
ground
water
by
the
SCI­
GROW
model
(
using
the
maximum
rate
4
lb.
a.
i.
/
ac
and
2
applications
­
potatoes)
was
0.05
µ
g/
L.
The
maximum
total
disulfoton
residue
concentration
predicted
in
ground
water
by
the
SCI­
GROW
model
for
the
same
scenario
is
3.19
µ
g/
L
(
except
90
percent
upper
bound
on
mean
half­
life
of
total
residues
is
259.6
days)
.

Ground
water
monitoring
data
generally
confirms
fairly
rapid
degradation
and
low
mobility
in
soil,
because
of
the
relatively
low
levels
and
frequency
of
detections
of
parent
disulfoton
in
ground
water.
There
were
no
ground­
water
detections
of
parent
disulfoton
in
the
USGS
NAWQA
(
USGS,
1998)
with
a
limit
of
detections
of
0.01
or
0.05
µ
g/
L,
depending
upon
method.

Most
of
the
studies
recorded
in
the
PGWDB
(
USEPA,
1992)
also
reported
no
disulfoton
detections.
Disulfoton
residues
ranging
from
0.04
to
100.00
µ
g/
L
were
reported
for
studies
conducted
in
Virginia
(
0.04
to
2.87
µ
g/
L)
and
Wisconsin
(
4.00
to
100.00
µ
g/
L)
.
Of
specific
interest
are
areas
where
the
concentrations
of
parent
disulfoton
reported
in
the
studies
(
VA
and
WI)
exceeded
the
estimate
of
0.05
µ
g/
L
obtained
from
EFED'
s
SCI­
GROW
(
ground­
water
screening
model)
model.
It
should
be
noted
that
the
Wisconsin
data
received
some
criticism
which
influences
the
certainty
of
these
detections,
no
such
criticisms
or
limitations
exist
for
the
Virginia
study.

The
major
issues,
concerning
the
Wisconsin
study
(
Central
Sands)
were
that
the
study
may
not
have
followed
QA/
QC
on
sampling
and
the
failure
of
follow­
up
sampling
to
detect
disulfoton
residues
in
ground
water
as
suggested
by
Holden
(
1986)
,
have
been
considered
by
EFED
in
the
70
ground­
water
quality
assessment.
The
Central
Sands
of
Wisconsin
are
known
to
be
highly
vulnerable
to
ground­
water
contamination.
There
are
regions
within
the
United
States
that
have
conditions
that
are
highly
vulnerable
to
ground
water
contamination
and
regularly
have
pesticides
detected
in
ground
water
which
far
exceeds
values
seen
elsewhere.
Several
of
these
areas
are
well
documented,
e.
g.
,
Long
Island,
Suffolk
County,
NY
and
Central
Sands
in
WI.
Although,
some
questions
have
been
levied
against
the
disulfoton
detections
in
Wisconsin,
the
occurrence
of
disulfoton
at
the
levels
reported
cannot
be
ruled
out.

There
were
no
detections
of
disulfoton,
disulfoton
sulfoxide,
and
disulfoton
in
the
ground­
water
monitoring
study
conducted
in
North
Carolina.
Efforts
were
made
to
place
the
wells
in
vulnerable
areas
where
the
pesticide
use
was
known,
so
that
the
pesticide
analyzed
for
would
reflect
the
use
history
around
the
well.
Seven
Christmas
tree,
one
wheat,
and
two
tobacco
growing
areas
were
sampled
for
disulfoton.
Limitations
of
the
study
include
that
sites
were
sampled
only
twice
and
the
limits
of
detections
were
high
(
e.
g.
,
>
1.0
µ
g/
L)
for
some
of
disulfoton
analytes.
Uncertainties
associated
with
the
study
include
whether
two
samples
from
eight
wells
are
adequate
to
represent
the
ground­
water
concentrations
of
disulfoton
residues,
did
DRASTIC
correctly
identify
a
site'
s
vulnerability,
and
were
the
wells
placed
down­
gradient
of
the
use
areas.

The
SCI­
GROW
model
represents
a
"
vulnerable
site"
,
but
not
necessarily
the
most
vulnerable.
Several
things
should
be
considered.
First,
the
Virginia
and
Wisconsin
monitoring
studies
were
probably
conducted
in
areas
vulnerable
to
ground­
water
contamination.
The
level
of
certainty
with
respect
to
vulnerability
is
probably
greater
for
Wisconsin
(
relatively
less
uncertainty)
than
for
Virginia
(
relatively
more
uncertainty
)
.
The
occurrence
of
preferential
flow
and
transport
processes
has
been
also
noted
in
Wisconsin
(
and
is
also
possible
in
Virginia)
and
may
(
speculation)
have
contributed
to
the
"
high"
concentrations
(
especially
in
WI)
when
the
initial
sampling
occurred,
but
not
necessarily
in
the
follow­
up
sampling)
.
The
knowledge
concerning
the
disulfoton
use
in
areas
in
association
with
the
wells
is
not
well
known
(
high
uncertainty)
.
Some
notable
limitations
of
modeling
and
monitoring
are
presented
elsewhere
in
this
document
(
c)
Drinking
Water
The
estimates
of
disulfoton
residues
in
drinking
water
in
an
index
reservoir
adjusted
by
percent
crop
area
in
the
watershed
is
using
the
coupled
PRZM/
EXAMS
models.
The
Agency
recommends
that
the
1­
out­
of­
10­
year
peak
values
be
used
the
acute
surface
drinking
water
level
for
parent
disulfoton,
and
for
chronic
levels
use
either
the
90­
day
and
annual
average.
The
maximum
values
are:
44.20,
2.77,
and
1.31
µ
g/
L
or
the
peak,
90­
day
mean,
and
long
term
mean,
respectively.
For
the
total
disulfoton
residues
the
peak,
90­
day
mean,
and
long
term
mean
are
104.92,
53.47,
and
10.42
µ
g/
L.
The
EDWCs
for
both
parent
disulfoton
and
TDR
exceed
the
DWLOC
values
estimated
by
the
Agency.
The
EDWCs
values
for
the
parent
disulfoton
have
less
uncertainty
than
the
total
residue,
because
there
is
more
certainty
surrounding
the
"
estimated"
aerobic
aquatic
metabolism
half­
life
for
the
estimated
aerobic
aquatic
half­
life
for
the
total
disulfoton
residues.
It
is
recommended
that
the
Virginia
data
be
considered
in
the
"
quantitative"
drinking
water
assessment
for
ground
water
exposure.
The
Wisconsin
data
should
be
noted
and
addressed
more
qualitatively.
Highly
vulnerable
areas,
such
as
the
Central
Sand
Plain,
do
not
represent
the
entire
use
area
and
can
probably
be
better
mitigated
or
managed
a
local
or
state
level.
Specifically,
it
is
recommended
that
the
2.87
µ
g/
L
be
used
for
acute
and
chronic
exposure
from
ground
water.
Based
upon
the
fate
properties
of
71
disulfoton,
the
sulfoxide
and
sulfone
degradates
(
more
persistent
and
probably
more
mobile)
have
a
greater
probability
of
being
found
in
ground
water.
It
is
likely
that
ground
water
and
surface
water
monitoring
study
(
ies)
may
be
required
to
better
assess
the
potential
exposure
from
the
degradates
(
and
also
parent)
in
addition
to
the
additional
fate
data
requirements.

The
registrant
disagreed
with
aquatic
dissipation
half
life
of
259
days
for
total
disulfoton
residues
and
cites
a
microcosm
study
(
MRID
43568501)
and
an
open
literature
study
(
La
Corte
et
al.
,
1994;
1995)
which
they
believe
provide
data
relevant
to
aquatic
dissipation.
However,
aerobic
and
anaerobic
aquatic
metabolism
studies
which
could
provide
valid
model
inputs
for
the
degradates
disulfoton
sulfone
and
disulfoton
sulfoxide
have
not
been
submitted.
Although
the
registrant
provided
the
Agency
with
additional
information
concerning
the
fate
of
disulfoton
residues
in
water
under
controlled
artificial
conditions
(
MRID
43568501
and
LaCorte
et
al.
,
1995)
,
this
information
is
limited
and
cannot
be
used
for
model
inputs.
Specifically,
these
studies
provide
information
concerning
the
combined
effects
of
hydrolysis,
photolysis,
and
metabolism,
with
photodegradation
contributing
significantly
to
the
dissipation.
(
An
input
value
for
photodegradation
was
included
in
the
modeling,
so
this
process
was
incorporated
into
the
dissipation
of
disulfoton
as
simulated
in
the
modeling.
)
Model
input
values
should
be
derived
from
studies
which
isolate
a
given
process,
i.
e.
,
aquatic
metabolism,
from
other
routes
of
dissipation
which
are
considered
separately
by
the
model.
EFED
believes
it
is
not
appropriate
to
use
dissipation
values,
such
as
those
provided
in
the
studies
cited
by
the
registrant,
as
inputs
for
models
which
are
intended
to
simulate
dissipation
from
a
variety
of
individual
processes.

The
259
day
half­
life
was
the
upper
90%
confidence
bound
on
the
mean
of
total
residue
half­
lives
in
aerobic
soil
metabolism
studies
(
MRIDs
40042201,
41585101,
43800101)
.
Because
there
are
no
studies
for
individual
degradates
from
which
model
inputs
can
be
derived,
and
because
these
degradates
are
of
toxicological
concern,
it
is
appropriate
to
use
total
residue
data
from
the
existing
studies.
The
assessment
could
be
refined
if
studies
for
the
individual
degradates
were
conducted
and
model
inputs
could
be
derived
from
these
studies.
The
aerobic
soil
metabolism
half­
life
is
used
to
estimate
the
aerobic
aquatic
half­
life
when
aerobic
aquatic
data
are
not
available.
OPP
has
noted
that
this
contributed
to
the
uncertainty
of
the
water
assessment.

EFED
thinks
that
it
is
appropriate
to
use
total
residues
to
estimate
exposure
when
there
are
toxic
degradates
and
when
data
are
not
available
for
the
individual
degradates.
This
will
contributed
to
the
uncertainty
of
the
water
assessment.

B.
Characterization
of
risk
to
nontarget
species
from
Disulfoton
Birds:
Birds:
Acute
risk
to
birds
is
predicted
especially
for
use
patterns
involving
the
15
G
formulation.
All
modeled
application
rates
and
methods
for
the
15
G
formulation
exceed
the
acute
risk
level
of
concern
for
birds,
regardless
of
size.
Robins
were
reported
to
have
been
killed
following
the
application
of
a
disulfoton
granular
product
to
a
tree
nursery.
Carcasses
were
found
during
terrestrial
field
testing
of
disulfoton
on
potatoes,
confirming
the
presumption
of
acute
risk
to
birds.
Since
disulfoton
is
a
systemic
pesticide,
the
granular
formulations
can
result
in
exposure
through
food
items
due
to
uptake
by
the
plant
tissues
in
addition
to
direct
exposure
to
any
unincorporated
granules.

72
Foliar
applications
of
liquid
formulations
present
the
greatest
risk
to
herbivorous
birds.
Based
on
the
results
of
field
studies,
the
residue
levels
on
sampled
invertebrates
are
well
below
those
predicted
by
EFED'
s
models,
consequently
insectivores
did
not
appear
to
be
at
risk.
However,
there
is
field
evidence
suggesting
that
some
species
are
extremely
sensitive
to
disulfoton
such
that
even
low
concentrations
caused
mortality.
The
Swainson
 
s
hawk
kill
appears
to
be
the
result
of
consuming
grasshoppers.
The
hawks
crop
contents
were
analyzed
and
contained
residues
around
8
ppm.
Finally,
live
blue
jays
collected
6
to
7
hrs
after
a
pecan
orchard
was
sprayed
at
0.72
lbs
ai/
A
had
brain
cholinesterase
inhibition
from
32
to
72%
(
White
et
al.
1990)
.
Although
it
is
unknown
whether
these
birds
would
eventually
die,
Ludke
et
al.
1975
suggest
that
inhibition
>
50%
in
carcasses
is
evidence
that
death
was
caused
by
some
chemical
agent.
Furthermore,
it
should
be
recognized
that
these
birds
were
not
only
feeding
on
contaminated
food,
but
also
were
impacted
by
dermal
and
inhalation
exposure.

Ground
applications
of
liquid
formulations
to
soil,
even
at
4.0
lb
ai/
A
would
not
be
expected
to
cause
mortality
to
birds.
Field
studies
have
demonstrated
that
residue
concentration
within
food
items
­
­
vegetation,
invertebrates
and
seeds
­
­
in
or
on
the
edge
of
fields
are
well
below
those
used
in
screening
level
assessments
and
empirically
derived
from
aerial
applications.
However,
in
light
of
the
points
made
in
the
previous
paragraph,
some
mortality
is
possible
given
the
possible
multiple
routes
of
exposure
and
hypersensitivity
of
some
species.

Chronic
risk
to
herbivorous
birds
are
predicted
from
exposure
to
disulfoton
when
assuming
birds
are
exposed
to
peak
residues
for
a
short
period
of
time
or
average
Fletcher
maximum
residues
for
longer
periods.
Based
on
reduced
hatchling
weight,
the
NOAEC
is
37;
both
for
bobwhite
quail
and
mallard
duck.
Foliar
applications
and
aerially
applied
soil
sprays
are
estimated
to
result
in
30
day
average
residues
(
based
on
maximum
Fletcher
values)
on
vegetation
exceeding
the
avian
chronic
level
of
concern
for
application
rates
equal
or
greater
than
a
single
application
of
1
lb
ai/
A.
A
residue
monitoring
study
for
Di­
Syston
8E
in
potatoes
showed
the
peak
residues
on
vegetation
was
105
ppm
after
the
initial
application
and
152
ppm
following
a
second
application
6
to
10
days
later.
In
the
same
study,
the
means
of
the
3
applications
for
vegetation
in
and
adjacent
to
fields
were
41
and
14
ppm
respectively.
The
upper
bound
95%
mean
for
the
vegetation
adjacent
to
the
fields
was
71
ppm.
Therefore
even
empirically
derived
residues
suggest
that
the
chronic
LOC
is
exceeded
on
foliage,
but
not
invertebrates
for
a
short
time
following
aerial
applications.
It
is
anticipated
that
since
the
sulfone
and
sulfoxide
degradates
of
disulfoton
were
similar
in
acute
toxicity
to
parent
disulfoton
they
would
have
similar
chronic
NOAECs.
These
degradates
extend
the
time
that
total
disulfoton
residues
are
available
for
consumption.
Since
many
of
the
applications
of
disulfoton
occur
in
the
spring,
overlapping
the
breeding
season
for
most
bird
species,
there
is
the
potential
for
significant
reproductive
impacts.

Mammals:
Acute
risk
to
mammals
is
expected
for
use
patterns
involving
the
15
G
formulation.
All
modeled
application
rates
and
methods
exceed
the
acute
risk
level
of
concern
for
mammals,
regardless
of
the
mammals
 
size.
.
Small
mammal
carcasses
were
found
during
terrestrial
field
testing
of
disulfoton
on
potatoes,
confirming
the
presumption
of
acute
risk
to
mammals.
Since
disulfoton
is
a
systemic
pesticide,
the
granular
formulations
can
result
in
exposure
through
food
items
due
to
uptake
by
the
plant
tissues
in
addition
to
direct
exposure
to
any
unincorporated
granules.

Applications
of
the
liquid
formulations
especially
by
air
can
result
in
mammals
being
exposed
to
multiple
routes
of
exposure
­
­
dermal,
inhalation,
drinking
contaminated
water
as
well
as
73
ingestion
of
contaminated
food
items.
The
persistent
sulfone
and
sulfoxide
degradates
are
also
toxic
to
mammals,
thereby
increasing
the
potential
risk
from
the
application
of
disulfoton.
The
registrant
has
suggested
that
mammals
as
well
as
birds
can
consume
an
equivalent
of
2
to
3
LD50'
s
as
part
of
their
diet
and
not
be
adversely
effected.
Although
this
may
be
true
for
a
population
of
laboratory
test
animals,
individuals
will
vary
in
their
sensitivity
and
can
die
as
a
result
of
inability
to
avoid
predation,
secure
prey
or
thermoregulate.
Numerous
pen
studies
were
conducted
with
cottontail
and
jack
rabbits
exposed
to
single
applications
ranging
from
1
to
25
lbs
ai/
A.
While
no
mortality
occurred
to
cottontails,
at
the
2
lb
ai/
A
rate
and
above
jackrabbits
suffered
100%
mortality.
Secondary
poisoning
did
not
occur
when
the
jackrabbit
carcasses
were
fed
to
a
number
of
avian
and
mammalian
carnivores.
The
apparent
difference
between
the
pen
study
results
and
the
acute
mortality
predicted
in
the
risk
assessment
screen
is
largely
due
to
the
possibility
that
the
calculated
1
day
LC50s
(
ranging
from
2
to
12.7
ppm)
discounts
the
rapid
metabolism
of
disulfoton.
However,
using
the
demeton
LC50
of
320
ppm
with
its
wide
ranging
confidence
interval
(
0
to
infinity)
also
adds
uncertainty
to
the
question
of
disulfoton
 
s
acute
risk
to
mammals.

Chronic
risk
to
mammals
is
predicted.
As
was
previously
discussed
in
the
above
acute
and
chronic
sections
for
birds,
there
are
several
reasons
why
small
mammals
are
likely
to
be
at
even
greater
risk,
not
the
least
of
which
is
the
extremely
low
NOAEC
of
0.8
ppm.
All
modeled
and
empirically
derived
residues
for
all
sites
exceed
the
chronic
risk
level
of
concern
for
mammals.
Finally,
the
persistence
of
the
sulfone
and
sulfoxide
degradates,
which
are
also
toxic
to
mammals,
increases
the
likelihood
of
chronic
risk
to
mammals.

Non­
target
Insects:
Disulfoton
and
its
sulfoxide
and
sulfone
degradates
are
moderately
to
highly
toxic
to
bees,
however
a
residual
study
with
honey
bees
indicated
no
toxicity
for
applications
up
to
1
lb
ai/
A.

Freshwater
Fish:
Most
of
the
modeled
use
patterns
did
not
exceed
acute
risk
levels
of
concern
for
freshwater
fish.
Only
the
two
soil
applications
at
4.0
lb
ai
\
A
of
the
liquid
formulation
exceeded
acute
risk.
All
other
scenarios
exceeded
the
restricted
use
and
endangered
species
levels
of
concern.
There
is,
however,
a
large
amount
of
variation
in
freshwater
fish
species
 
sensitivity
to
disulfoton,
as
evidenced
in
the
toxicity
data
table.
The
microcosm
study
included
bluegill
sunfish.
Following
the
last
application
of
30
ppb,
10%
of
the
fish
died.
Several
kills
of
freshwater
fish
have
occurred
from
applications
of
disulfoton
to
different
crops­
­
both
as
registered
uses
as
well
as
from
misuse.

Chronic
risk
to
freshwater
fish
may
occur
from
uses
where
single
application
rates
are
equal
to
4
lb
ai/
a
and
from
3
applications
of
1
lb
ai/
A.
.
The
single
freshwater
fish
species
(
rainbow
trout)
,
for
which
chronic
toxicity
data
was
available,
demonstrates
significantly
less
sensitivity
to
disulfoton
than
several
other
species
(
bluegill
sunfish,
bass,
guppy)
.
Therefore,
an
estimated
chronic
NOEC
value
was
calculated
using
the
chronic
to
acute
ratio
for
the
rainbow
trout,
as
described
earlier.
Based
on
the
estimated
chronic
NOAEC
for
bluegill,
chronic
effects
would
occur
from
the
present
uses
on
tobacco,
foliar
treatments
of
potatoes
and
repeated
soil
treatments
of
cotton.
Christmas
tree
plantations
were
not
modeled,
however
the
high
application
rate
(
possibly
47
lbs
ai/
A)
and
sloped
land
may
be
a
potentially
risky
site.

Freshwater
Invertebrates:
All
modeled
crop
scenarios
exceeded
the
acute
risk
level
of
concern,
but
the
highest
risk
quotients
were
less
than
10.
Again,
the
risk
is
further
increased
due
to
the
toxicity
and
persistence
of
the
degradates
of
disulfoton.
Microcosm
study
results
74
indicated
that
there
was
recovery
of
most
phyla
examined
at
3
ppb
and
long
term
impacts
for
most
phyla
at
30
ppb.
Therefore
10
ppb
is
probably
a
concentration
where
short
term
effects
will
occur,
but
recovery
can
be
anticipated.

Chronic
risk
to
freshwater
invertebrates
is
predicted
to
from
the
use
of
disulfoton.
All
of
the
modeled
crop
scenarios
greatly
exceeded
the
level
of
concern,
sometimes
by
a
factor
of
several
hundred.
Invertebrate
life­
cycle
testing
with
disulfoton
shows
that
it
impacts
reproductive
parameters
(
number
of
young
produced
by
adults)
in
addition
to
survival
and
growth.
The
21
day
average
EECs
for
the
modeled
sites
ranged
from
4.3
to
17.9
ppb.
For
the
most
part
these
EECs
are
within
the
range
where
recovery
was
occurring
in
the
microcosm.
However
there
is
uncertainty
as
to
how
much
more
reliable
the
microcosm
may
be
as
a
predictor
of
safety.

Estuarine
and
Marine
Fish:
Although
acute
and
restricted
risk
levels
of
concern
were
not
exceeded
for
estuarine
and
marine
fish,
the
endangered
species
level
of
concern
was
exceeded
for
several
of
the
modeled
crop
scenarios
(
cotton,
potatoes
and
wheat)
.
As
was
note
among
the
freshwater
fish,
there
can
be
substantial
species
differences
in
sensitivity
to
disulfoton.
Therefore,
it
is
possible
that
the
single
marine/
estuarine
fish
species
tested
(
Sheepshead
minnow)
does
not
fully
represent
the
true
range
of
sensitivity
found
in
a
marine
or
estuarine
ecosystem,
and
this
assessment
may
therefore
underestimate
the
true
risk
to
marine/
estuarine
fish.
There
is
also
some
uncertainty
in
using
the
PRZM/
EXAMS
EECs
derived
for
ponds
to
predict
exposure
to
marine/
estuarine
organisms.
The
scenarios
modeled
are
based
on
hydrologic
data
for
freshwater
habitats.
The
exposure
in
a
marine
or
estuarine
habitat
may
be
higher
or
lower
than
that
predicted
for
a
freshwater
habitat,
resulting
in
higher
or
lower
risk
to
marine/
estuarine
organisms.

Chronic
risk
to
estuarine
and
marine
fish
is
predicted
from
the
use
of
disulfoton.
Both
early
life­
stage
and
full
life­
cycle
testing
demonstrated
a
variety
of
effects
at
low
levels
of
disulfoton.
Risk
quotients
based
on
the
early
life­
stage
toxicity
endpoint
exceeded
the
level
of
concern
for
cotton,
potatoes
and
tobacco.
The
highest
risk
quotients
were
based
on
numerous
life­
cycle
toxicity
endpoints
­
­
fecundity,
hatching
success
and
growth;
consequently
the
chronic
level
of
concern
was
exceeded
for
all
modeled
scenarios.
Estuarine
fish
spawning
in
the
upper
reaches
of
tributaries
of
bays
would
be
a
greatest
risk.
However
the
likelihood
of
this
risk
is
uncertain
for
several
reasons:
1)
the
required
time
the
adults
must
be
exposed
to
disulfoton
in
order
for
their
reproductive
systems
to
be
effected
and
2)
the
residency
time
of
disulfoton
residues
in
tidal
or
flowing
water.
Even
if
adults
are
effected
after
an
exposure
of
only
a
week,
disulfoton
may
be
moved
out
of
an
area
within
several
days.

Estuarine
and
Marine
Invertebrates:
Three
of
the
five
modeled
scenarios
(
cotton,
potatoes,
and
tobacco)
resulted
in
exceedences
of
the
estuarine/
marine
invertebrate
acute
risk
level
of
concern.
All
the
remaining
uses
exceeded
the
restricted
use
level
of
concern.
Similar
uncertainty
exists
as
to
the
validity
of
the
exposure
scenario
for
invertebrates
as
was
just
described
for
estuarine
fish.

Chronic
risk
to
marine/
estuarine
invertebrates
is
predicted.
All
of
the
modeled
crop
scenarios
exceeded
the
chronic
level
of
concern.
The
much
shorter
life
cycle
of
invertebrates
as
compared
to
fish,
increases
the
likelihood
that
only
a
brief
exposure
(
a
few
day
or
even
hours)
of
adults
to
disulfoton
concentrations
around
the
NOAEC
is
sufficient
to
negatively
impact
reproduction.
The
degree
to
which
the
freshwater
microcosm
is
a
predictor
of
safety
for
the
estuarine
invertebrates
in
highly
uncertain.
Only
the
mysid
shrimp
has
been
tested
and
it
was
acutely
and
75
chronically
less
sensitive
than
freshwater
Daphnia.
Therefore,
on
the
basis
of
this
limited
data,
the
chronic
impact
to
estuarine
invertebrates
not
only
appears
to
be
lower
than
for
freshwater
invertebrates,
but
is
likely
to
be
low.

Nontarget
Plants:
Currently,
terrestrial
and
aquatic
plant
testing
is
not
required
for
pesticides
other
than
herbicides
except
on
a
case­
by­
case
basis.
Nontarget
plant
testing
was
not
required
for
disulfoton,
so
the
risk
to
plants
could
not
be
assessed
at
this
time.
There
are
phytotoxicity
statements
on
the
label,
however,
as
well
as
some
incident
reports
of
possible
plant
damage
from
the
use
of
disulfoton,
so
there
is
the
potential
for
risk
to
nontarget
plants.

Summary
of
Risk
Assessment
of
North
Carolina
24c
for
use
in
Christmas
Tree
Farms
Christmas
tree
farms
and
the
adjacent
areas
­
­
forests
and/
or
pasture
 
provide
excellent
habitat
for
a
great
variety
of
wild
life.
The
use
of
granular
disulfoton
suggests
that
there
is
acute
risk
to
small
birds
and
mammals.
The
North
Carolina
Christmas
Tree
community
has
submitted
numerous
testimonials
emphasizing
the
ever
increasing
numbers
and
diversity
of
wild
life
.
This
includes
game
animals
such
as
turkey
rearing
young
amidst
the
Christmas
trees,
song
birds,
rodents
and
foxes.
Although
this
information
is
intended
to
suggest
there
is
little
or
no
negative
impact
from
not
only
disulfoton,
but
other
pesticides
or
cultural
practices
as
well,
the
Agency
would
prefer
to
receive
documented
surveys
or
research
before
making
a
final
determination.

There
were
no
detections
of
disulfoton,
disulfoton
sulfoxide,
and
disulfoton
sulfone
in
the
ground­
water
monitoring
study
conducted
in
North
Carolina
by
the
North
Carolina
Departments
of
Agriculture
and
Environment,
Health,
and
Natural
Resources.
Seven
Christmas
tree,
one
wheat,
and
two
tobacco
growing
areas
were
sampled
for
disulfoton.
disulfoton
residues.
Limitations
of
the
study
include
that
sites
were
sampled
only
twice
and
the
limits
of
detections
were
high
(
e.
g.
,
>
1.0
µ
g/
L)
for
some
of
disulfoton
analytes.
Uncertainties
associated
with
the
study
include
whether
two
samples
from
eight
wells
are
adequate
to
represent
the
ground­
water
concentrations
of
disulfoton
residues,
did
DRASTIC
correctly
identify
a
site'
s
vulnerability,
and
were
the
wells
placed
down­
gradient
of
the
use
areas.

The
use
of
Disulfoton
15
G
in
Christmas
tree
farms
at
this
time
cannot
be
modeled
for
potential
surface
water
contamination.
EFED
assumes
the
estimated
concentration
for
the
North
Carolina
24
(
c)
use
pattern
­
­
2.75
lbs
ai/
A
unincorporated
­
­
may
be
similar
to
the
values
for
the
single
4.0
lb
ai/
A
incorporated
application
of
granular
disulfoton
to
tobacco.
Based
on
this
assumption
there
is
acute
risk
to
aquatic
invertebrates
and
chronic
risk
to
freshwater
fish
and
aquatic
invertebrates.

The
North
Carolina
Christmas
tree
industry
submitted
two
surveys
of
streams
in
the
Westerns
region.
The
surveys
followed
a
protocol
for
looking
at
macro
invertebrates
to
assess
the
impact
of
agricultural
practices
associated
with
Christmas
tree
farming.
In
summary,
the
two
surveys
suggests
that
when
conservation
measures
associated
with
Christmas
tree
farming
in
the
Western
counties
of
North
Carolina
are
implemented,
there
may
be
only
slight,
short
term
impact
to
aquatic
macro
invertebrates
from
disulfoton
use.
Aquatic
macro
invertebrates
appear
to
have
the
capacity
to
recover
from
any
impact
that
could
be
caused
by
disulfoton
use
on
Christmas
trees
in
Western
North
Carolina.

76
C.
Mitigation
The
use
of
disulfoton
at
single
application
rates
of
1.0
lb
ai/
A
and
greater,
and
multiple
application
rates
of
0.5
lb
ai/
A
and
greater,
poses
a
high
acute
risk
to
birds,
mammals,
fish,
and
aquatic
invertebrates,
as
well
as
to
nontarget
insects.
EFED
believes
that
amending
label
rates
to
the
lowest
efficacious
rate
as
a
maximum,
as
well
as
restricting
the
number
of
applications
per
year
and
lengthening
the
application
interval,
would
reduce
acute
risk
to
terrestrial
and
aquatic
organisms.
Requiring
in­
furrow
applications
wherever
feasible,
and
eliminating
banded
applications
of
granular
disulfoton
with
narrow
row
spacing,
would
also
reduce
the
risk
to
nontarget
organisms,
especially
birds
and
mammals.
Care
must
be
taken,
however,
so
that
the
likelihood
of
disulfoton
or
its
degradates
leaching
to
ground
water
is
not
increased
by
these
application
methods.
Eliminating
aerial
applications
of
disulfoton
and
imposing
buffer
strips
around
aquatic
habitats
would
reduce
the
risk
to
aquatic
organisms.
Risk
to
bees
and
other
nontarget
insects
could
be
lowered
by
not
applying
disulfoton
when
the
insects
are
likely
to
be
visiting
the
area.

Qualitative
comparative
ecological
risk
assessment
between
present
and
proposed
disulfoton
uses.

Bayer
has
proposed
the
following
changes
to
some
use
patterns
assessed
by
the
Agency
that
would
reduce
the
ecological
risk
from
Di­
Syston
8E:

*
cancel
aerial
applications
to
cotton
and
wheat.
*
cancel
foliar
applications
to
cotton.

The
table
reflects
additional
changes
proposed
by
Bayer.

Table
42.
Comparison
of
present
and
proposed
changes
in
4
use
patterns
of
Di­
Syston
8E
Present
Use
Proposed
Use
Rate
/
Number
of
Applications
/
Interval
/
Incorp.
Depth/
method
1
Rate/
Number
of
Applications
/
Interval/
Incorp.
Depth/
method
1
lb.
ai/
A
/
#
/
days
/
inches
lb.
ai/
A
/
#
/
days
/
inches
cotton
1.0/
3/
21/
0/
gs
cotton
1.0/
1/
­
/
0/
gs
potatoes
4.0/
2/
14/
2.5/
gs
potatoes
3.0/
1/
­
/
2.5/
gs
potatoes
1.0/
3/
14/
0/
af
potatoes
0.5/
3/
14­
/
0/
af
wheat
0.75/
2/
30/
0/
gs
wheat
0.75/
1/
­
/
0/
gs
1
Method
of
application:
f
=
foliar
and
s
=
soil;
gs
=
ground
spray,
af
=
aerial
spray­
foliar
Risk
to
Birds
and
Mammals
Canceling
aerial
application
to
wheat
and
cotton
reduces
significantly
the
potential
for
exposing
77
edge
of
field
food
items
and
vegetation.
Canceling
foliar
applications
to
cotton
reduces
the
opportunity
for
exposure,
by
reducing
the
food
items
that
are
directly
sprayed.
As
the
discussion
below
explains,
field
monitoring
indicates
that
ground
spray
to
soil
reduces
substantially
the
residues
on
food
items
from
those
residues
predicted
from
the
nomograph.

Potato
aerial
foliar
at
0.5
lb
ai/
acre
Biological
field
testing
(
MRID
41359101)
suggests
that
significant
acute
risk
to
mammals
from
foliar
sprays
is
unlikely
at
a
single
application
of
1
lb
ai/
acre
or
lower.
Reducing
the
potato
rate
from
1
lb
ai/
acre
3
times,
to
0.5
lb
ai/
acre
3
times,
substantially
lowers
the
acute
risk
to
mammals.

Wheat,
potato
and
cotton
ground
spray
to
soil
Field
residue
monitoring
(
MRID
41118901)
indicates
that
residues
on
food
items
following
ground
applications
to
soil
are
significantly
lower
than
would
be
expected
from
direct
application
to
vegetation.
Peak
residues
following
the
first
of
two
treatments
at
3
lb
ai/
acre
(
in
furrow)
ranged
from
0.9
ppm
(
invertebrates
and
edge
of
field
vegetation)
,
to
26
ppm
(
potato
foliage)
.
The
second
treatment
at
3
lb
ai/
acre
side
dressing
(
6­
7
weeks
later)
resulted
in
peak
residues
of
1.8
(
invertebrates)
,
44
ppm
potato
foliage,
and
54
ppm
(
edge
of
field
vegetation)
.
The
residues
from
these
applications
are
not
only
lower
than
those
estimated
using
the
nomograph,
but
also
lower
than
the
field
residues
resulting
from
foliar
applications.
In
the
foliar
residue
monitoring
study
(
3
aerial
applications
at
1.0
lb
ai/
acre)
the
peaks
were:
invertebrates
(
16
ppm)
and
vegetation
(
154
ppm)
.
The
proposed
changes
would
greatly
reduce
exposure
terrestrial
species.

Table
43.
Comparison
of
potential
acute
and
chronic
risk
resulting
from
proposed
changes
in
4
use
patterns
of
Di­
Syston
8E
for
birds
and
mammals
Present
Use
Birds
Mammals
Proposed
Use
Birds
Mammals
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
lb.
ai/
A
/
#
/
days
/
inches
lb.
ai/
A
/
#
/
days
/
inches
cotton
1.0/
3/
14/
0/
gs
E
Y
R
Y
cotton
1.0/
1/
­
/
0/
gs
no
Y
E
Y
potatoes
4.0
/
2/
14/
2.5/
gs
R
Y
A
Y
potatoes
3.0/
1/
­
/
2.5/
gs
E
Y
R
Y
potatoes
1.0/
3/
14/
0/
af
R
Y
A
Y
potatoes
0.5/
3/
14­
/
0/
af
R
Y
R
Y
wheat
0.75/
2/
30/
0/
gs
E
Y
R
Y
wheat
0.75/
1/
­
/
0/
gs
no
Y
E
Y
1
Method
of
application:
f
=
foliar
and
s
=
soil;
g
=
ground
and
a
=
aerial
Acute
=
ac;
Chronic
=
ch
Acute
risk
LOC
is
exceeded=
A;
Restricted
use
LOC
is
exceeded=
R;
Endangered
Species
LOC
is
exceeded=
E;
No
acute
LOC
is
exceeded=
no;
LOC
for
chronic
risk
is
exceeded=
Y;
LOC
for
chronic
risk
is
not
exceeded=
N.

Risk
to
fish
and
aquatic
invertebrates
The
following
table
summarizes
the
results
of
modeling
the
proposed
new
uses.
The
EECs
were
reduced
from
the
present
registered
use
patterns:

78
Mean
of
Annual
Means
(
µ
g/
L)
0.23
0.12
0.57
0.05
Table
44
Tier
II
Upper
Tenth
Percentile
EECs
for
Disulfoton
Parent
based
on
proposed
new
maximum
label
rates
and
management
scenarios
for
cotton,
potatoes,
and
spring
wheat
in
farm
pond.
Estimated
using
PRZM3/
EXAMS.
Concentration
(
µ
g/
L)

(
1­
in­
10
annual
yearly
maximum
value)
Annual
Avg.
0.62
0.15
0.62
0.08
90­
Day
Avg.
2.42
0.57
2.42
0.28
60­
Day
Avg.
3.54
0.84
3.45
0.41
21­
Day
Avg.
6.83
1.67
5.20
0.67
96­
Hour
Avg.
9.38
2.18
6.62
0.91
Peak
10.31
2.42
7.51
1.02
Disulfoton
Application
Rate
/
Number
of
Apps
/
Interval
/
Incorp.

Depth/
method
1
lb.
ai/
A
/
#
/
days
/
inches
1.
00/
1/
­
/
0/
gs
3.00/
1/
­
/
2.5/
gs
0.5/
1/
­
/
0/
af
0.75/
1/
­
/
0/
gs
Crop
Cotton
Potatoes
Potatoes
Spr.
Wheat
1
Method
of
application:
f
=
foliar
and
s
=
soil;
g
=
ground
and
a
=
aerial
79
The
following
tables
reflect
a
qualitative
comparative
risk
assessment
for
aquatic
and
estuarine
organisms.

Table
45.
Comparison
of
potential
acute
and
chronic
risk
resulting
from
proposed
changes
in
4
use
patterns
of
Di­
Syston
8E
for
freshwater
fish
and
invertebrates
Present
Use
Fish
Invertebrates
Proposed
Use
Fish
Invertebrates
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
a
c
ch
ac
ch
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
lb.
ai/
A
/
#
/
days
/
inches
lb.
ai/
A
/
#
/
days
/
inches
cotton
1.0/
3/
14/
0/
gs
R
Y
A
Y
cotton
1.0/
1/
­
/
0/
gs
R
N
A
Y
potatoes
4.0/
2/
14/
2.5/
gs
R
Y
A
Y
potatoes
3.0/
1/
­
/
2.5/
gs
E
N
A
Y
potatoes
1.0/
3/
14/
0/
af
R
Y
A
Y
potatoes
0.5/
3/
14­
/
0/
af
R
N
A
Y
wheat
0.75/
2/
30/
0/
gs
R
N
A
Y
wheat
0.75/
1/
­
/
0/
gs
no
N
R
Y
1
Method
of
application:
f
=
foliar
and
s
=
soil;
g
=
ground
and
a
=
aerial
Acute
=
ac;
Chronic
=
ch
Acute
risk
LOC
is
exceeded=
A;
Restricted
use
LOC
is
exceeded=
R;
Endangered
Species
LOC
is
exceeded=
E;
No
acute
LOC
is
exceeded=
no;
LOC
for
chronic
risk
is
exceeded=
Y;
LOC
for
chronic
risk
is
not
exceeded=
N.

Table
46.
Comparison
of
potential
acute
and
chronic
risk
resulting
from
proposed
changes
in
4
use
patterns
of
Di­
Syston
8E
for
estuarine
fish
and
invertebrates
Present
Use
Fish
Invertebrates
Proposed
Use
Fish
Invertebrates
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
Rate
/
Number
of
Apps
/
Interval
/
Incorp.
Depth/
method
1
ac
ch
ac
ch
lb.
ai/
A
/
#
/
days
/
inches
lb.
ai/
A
/
#
/
days
/
inches
cotton
1.0/
3/
14/
0/
gs
no
Y
A
Y
cotton
1.0/
1/
­
/
0/
gs
no
Y
A
Y
potatoes
4.0/
2/
14/
2.5/
gs
no
Y
R
Y
potatoes
3.0/
1/
­
/
2.5/
gs
no
N
R
N
potatoes
1.0/
3/
14/
0/
af
no
Y
A
Y
potatoes
0.5/
3/
14­
/
0/
af
no
Y
A
Y
wheat
0.75/
2/
30/
0/
gs
no
Y
A
Y
wheat
0.75/
1/
­
/
0/
gs
no
N
E
N
1
Method
of
application:
f
=
foliar
and
s
=
soil;
g
=
ground
and
a
=
aerial
Acute
=
ac;
Chronic
=
ch
Acute
risk
LOC
is
exceeded=
A;
Restricted
use
LOC
is
exceeded=
R;
Endangered
Species
LOC
is
exceeded=
E;
No
acute
LOC
is
exceeded=
no;
LOC
for
chronic
risk
is
exceeded=
Y;
LOC
for
chronic
risk
is
not
exceeded=
N.

80
Summary
EFED
supports
the
proposed
use
modifications,
and
concurs
that
generally
they
reduce
risk
to
nontarget
organisms
to
varying
degrees.
Although
there
remains
the
concern
for
hypersensitive
birds
and
mammals,
the
acute
risk
to
most
birds
and
mammals
is
reduced
substantially.
The
greatest
risk
reduction
to
fish
and
aquatic
invertebrate
are
soil
applications
to
potatoes
and
wheat.
There
appears
to
be
little
changes
in
acute
risk
to
aquatic
organisms
from
the
proposed
modifications
to
cotton
and
potatoes
(
aerial
application)
.
Chronic
risk
to
terrestrial
and
aquatic
organisms
are
likely
to
be
reduced;
but
with
less
certainty,
because
the
duration
of
exposure
required
to
produce
adverse
chronic
effects
in
the
field
are
not
available.

7.
References
Balcomb,
R.
,
C.
A.
Bowen
II,
D.
Wright,
and
M.
Law.
1984.
Effects
on
wildlife
of
at­
planting
corn
applications
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granular
carbofuran.
J.
Wildl.
Manage.
48:
1353­
1359.

Barrett,
M.
R.
1999.
Updated
Documentation
on
the
SCI­
GROW
Method
to
Determine
Screening
Concentration
Estimates
for
Drinking
Water
Derived
from
Ground
Water
Sources.
Memorandum
From:
M.
R.
Barrett
To:
J.
Merenda.
Environmental
Fate
and
Effects
Division,
Office
of
Pesticide
Programs,
U.
S.
Environmental
Protection
Agency,
Arlington,
VA.

Barton,
A.
1982.
Note
to
Ed
Johnson
dated
12/
10/
82
describing
joint
effort
between
EPA/
OPP
and
Wisconsin
Department
of
Natural
Resources
to
monitor
pesticides
in
ground
water
per
communication
with
the
Wisconsin
Department
of
Natural
Resources.
1982.
Pesticide
Monitoring
in
Wisconsin
Ground
Water
in
the
Central
Sands
Area.
Madison,
WI
Dunning,
J.
B.
,
Jr.
1984.
Body
weights
of
686
species
of
North
American
birds.
Western
Bird
Banding
Association
Monograph
No.
1.
38
pp.

EPA.
1986.
Guidance
for
conducting
terrestrial
field
studies.

Evans,
J.
,
P.
L.
Hegdal,
and
R.
E.
Griffith,
Jr.
1970.
Evaluations
of
Di­
Syston
for
jackrabbit
control.
Denver
Wildlife
Research
Center.
(
MRID
413591­
01)
.

Fisher,
D.
L.
and
L.
B.
Best.
1995.
Avian
consumption
of
blank
pesticide
granules
applied
at
planting
to
Iowa
cornfields.
Environ.
Tox.
Chem.
14:
1543­
1549.

Harken,
J.
M.
,
F.
A.
Jones,
R.
Fathulla,
E.
K.
Dzanton,
E.
J.
O'
Neill,
D.
G.
Kroll,
and
G.
Chesters.
1984.
Pesticides
in
Groundwater
beneath
the
Central
Sand
Plain
of
Wisconsin.
Univ.
of
Wisc.
Resources
Center
Technical
Report
WIS
WRC
84­
01.

Holden,
P.
W.
1986.
Pesticide
and
Groundwater
Quality
Issues
and
Problems
in
Four
States.
National
Academy
Press.
Washington,
D.
C.

Howard,
P.
H.
1991.
1991.
Disulfoton.
p.
309­
318.
Vol.
III.
Pesticides
Handbook
of
Environmental
Fate
and
Exposure
Data
for
Organic
Chemicals.
P.
H.
Howard
et
al.
,
(
ed)
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Lewis
Publishers,
Inc.
,
Chelsea,
MI
81
Johnson
et
al.
1989.
Guthion
35%
WP:
An
Evaluation
of
Its
Effects
Upon
Wildlife
on
and
Around
Apple
Orchards
in
Washington
State.
MRID
411397­
01.

Jones,
R.
D.
,
J.
Breithaupt,
J.
Carleton,
L.
Labelo,
J.
Lin,
R.
Matzner,
R.
Parker,
W.
Effland,
N.
Thurman,
and
I.
Kennedy.
2000.
Guidance
for
Use
of
the
Index
Reservoir
and
Percent
Crop
Area
Factor
in
Drinking
Water
Assessments.
Draft
3/
21/
2000.
Environmental
Fate
and
Effects
Division,
Office
of
Pesticide
Programs,
U.
S.
Environmental
Protection
Agency,
Arlington,
VA.

La
Corte,
S.
and
D.
Darcelo.
1994.
Rapid
Degradation
of
Fenitrothion
in
Estuarine
Waters.
Environmental
Sci.
and
Technol.
28:
1159­
1163.

La
Corte,
S.
,
S.
B.
Lartiges,
P.
Garrigues,
and
D.
Barcelo.
1995.
Degradation
of
Organophosphorus
Pesticides
and
Their
Transformation
Products
in
Estuarine
Waters.
Environmental
Sci.
and
Technol.
29:
431­
438.

Lenant,
David
et.
al.
1999.
 
Evaluation
of
Christmas
Tree
Farming
and
Cattle
Grazing
on
Water
Quality
in
the
New
River
Basin,
Ashe
and
Alleghany
Counties
 
.
Submitted
in
Comments
from
Jill
Sidebottom
NC
State
Extension
Service,
in
Response
to
the
Draft
Disulfoton
RED
(
Unpublished)
.

Ludke,
J.
L.
,
E.
F.
,
Hill,
and
M.
P.
Dieter.
1975.
Cholinesterase
(
ChE)
response
and
related
mortality
among
birds
fed
ChE
inhibitors.
Archives
of
Environmental
Contamination
and
Toxicology
3:
1­
21.

Lyon,
L.
1997.
Apparent
systemic
exposure
of
Swainson'
s
hawks
to
the
insecticide
disulfoton.
Abstract
of
the
Proc.
18
th
Annual
SETAC
Meeting.

Mostaghimi,
S.
et
al.
1989.
Watershed/
Water
quality
monitoring
for
evaluating
BMP
effectiveness
­
Nomini
Creek
Watershed.
Report
N­
P1­
8811.
Agricul.
Engineer.
Dept.
Virginia
Tech.

NCIWP,
1997.
The
Interagency
Study
of
the
Impact
of
Pesticide
Use
on
Ground
Water
in
North
Carolina.
Prepared
for
North
Carolina
Pesticide
Board
by
The
Interagency
Work
Group.
March
4,
1997.
North
Carolina
Department
of
Agriculture,
Raleigh,
NC.

Patuxent
Wildlife
Research
Center.
1993.
Swainson
Hawk
Deaths,
Young
County,
Texas.
ECDMS
Working
Catalog
#
2040019.
In
response
to
submission
of
Regional
Study
ID
93R2HFO.
(
Unpublished)
.

Sheeley
et
al.
1989.
Guthion
35%
WP:
An
Evaluation
of
Its
Effects
Upon
Wildlife
on
and
Around
Apple
Orchards
in
Michigan
MRID
411959­
01.

Sidebottom,
J.
et
al.
2000.
 
Evaluation
of
the
effect
of
Christmas
tree
production
in
western
North
Carolina
on
surface
water
quality
 
.
Submitted
in
Comments
from
Jill
Sidebottom,
NC
State
Extension
Service,
in
Response
to
the
Draft
Disulfoton
RED
(
Unpublished)
.

82
USEPA.
1999.
Memorandum.
Draft:
Standardization
of
Spray
Drift
Input
Values
for
PRZM/
EXAMS
Modeling,
dated
4/
13/
99)
from
Water
Quality
Technology
Team,
Environmental
Fate
and
Effects
Division,
Office
of
Pesticide
Programs,
USEPA.
Arlington,
VA.

USEPA.
,
2000.
DP
Barcode
267486
EPA
Review
of
NCIWP,
1997.
The
Interagency
Study
of
the
Impact
of
Pesticide
Use
on
Ground
Water
in
North
Carolina.
Prepared
for
North
Carolina
Pesticide
Board
by
The
Interagency
Work
Group.
March
4,
1997.
North
Carolina
Department
of
Agriculture,
Raleigh,
NC
and
its
relevance
to
the
disulfoton.

White,
D.
H.
and
J.
T.
Seginak.
1990.
Brain
Cholinesterase
inhibition
in
Songbirds
from
Pecan
Groves
Sprayed
with
Phosalone
and
Disulfoton.
Journal
of
Wildlife
Diseases
26(
1)
:
103­
106.

83
APPENDIX
I:
USE
OF
DISULFOTON
(
LB.
AI/
YR)
BY
CROP
AND
BY
STATE
Crop
Percent
of
market
lb
ai/
yr
(
Doane
 
s
Agriculture
Service
data)
lb
ai/
yr
(
estimate
provided
by
BEAD,
based
on
market
information)

Cotton
61
428,000
420,000­
840,000
Wheat
16
123,000
180,000­
354,000
Barley
7
49,000
29,000­
77,000
Potatoes
7
50,000
120,000­
195,000
Peanuts
5
27,000
47,000­
106,000
Cole
crops
2
14,000
no
information
Corn
1
4,000
36,000­
73,000
Tobacco
1
4,000
64,000­
128,000
State
Percent
of
market
lb
ai/
yr
(
based
on
total
ai/
yr
of
1,700,000
lb)

California
16
272,000
Louisiana
11
187,000
Kentucky
10
170,000
Missouri
8
136,000
Arkansas
8
136,000
Texas
7
119,000
Alabama
7
119,000
Virginia
6
102,000
North
Carolina
5
85,000
Maine
4
68,000
Mississippi
4
68,000
Utah
4
68,000
Georgia
3
51,000
Michigan
2
34,000
Ohio
2
34,000
84
Arizona
1
17,000
New
Mexico
1
17,000
85
APPENDIX
II:
Chemical
Structure
of
Disulfoton
86
APPENDIX
III
The
monitoring
data
obtained
from
STORET
on
October
16,
1997
are
summarized
in
Table
1.
The
majority
of
samples
had
low
levels
(
<
16
µ
g/
L)
of
disulfoton
residues.
However,
there
were
indications
of
some
high
concentrations
(
may
be
a
reflection
of
how
the
data
were
reported)
as
the
disulfoton
concentrations
in
the
monitoring
were
not
always
known.
This
is
because
the
detection
limit
was
not
adequate
(
extremely
high)
or
specified,
and/
or
the
limit
of
quantification
was
not
stated
or
extremely
high.
Disulfoton
concentrations
were
simply
given
as
less
than
a
value.
Therefore,
considerable
uncertainty
exists
with
respect
to
the
monitoring
data
(
especially
the
STORET
data)
.

Limitations
in
Monitoring
Monitoring
data
is
limited
by
the
lack
of
correlation
between
sampling
date
and
the
use
patterns
of
the
pesticide
within
the
study
 
s
drainage
basin.
Additionally,
the
sample
locations
were
not
associated
with
actual
drinking
water
intakes
for
surface
water
nor
were
the
monitored
wells
associated
with
known
ground
water
drinking
water
sources.
Also,
due
to
many
different
analytical
detection
limits,
no
specified
detection
limits,
or
extremely
high
detection
limits,
a
detailed
interpretation
of
the
monitoring
data
is
not
always
possible.

87
Table
1.
Summary
of
disulfoton
detections
in
STORET
.

Type
of
Water
Body
#
of
Samples
Analytical
Method
Disulfoton
Concentration
1
(
range
µ
g/
L)

Stream
1940
39010/
39011
2
0.00­
16.00
 
253
81888
3
0.00­
100.00
 
39
82617
4
0.05­
1.00
 
5164
82677
5
0.00­
0.21
Lakes
270
39011
0.01­
0.10
 
2
81888
0.05­
0.14
 
20
82617
1.00­
1.00
 
52
82677
0.00­
0.10
Springs
24
39011
0.01­
0.10
 
15
81888
0.05­
100.00
 
134
82677
0.008­
0.060
Reservoirs
2
81888
0.10­
0.20
Estuary
4
39011
0.01
 
1
82677
0.02
Canals
2
39011
0.5
 
215
81888
0.03­
0.3
Wells
383
39010
1.00­
100.00
 
951
39011
0.01­
1.00
 
3108
81888
0.00­
250.00
 
44
82617
0.03­
1.00
 
2559
82677
0.00­
0.14
1
Value
reported
as
 
known
to
be
less
than
reported
 
.

2
39010/
39011
Flame
Photometer
Whole
Water:
disulfoton/
Di
syston
3
81888
Disulfoton
Whole
Water
4
82617
Disulfoton
Total
Recoverable
whole
water
5
82677
Disulfoton
 
filtered
0.07
um
 
Total
Recoverable
whole
water
88
Appendix
IV
Environmental
Fate
and
Chemistry
Study
Identification
Blumhorst,
R.
B.
,
and
P.
Y.
Yen.
Aerobic
Soil
Metabolism
of
[
Ethylene­
1­
14
C
Disulfoton.
]
Bayer
Report
106944,
Study
No.
D1042103.
Unpublished
study
performed
by
EPL
Bio­
Analytical
Services.
,
Kansas
City,
Missouri.

Forbes,
A.
D.
1988.
Uptake,
depuration,
and
bioaccumulation
of
14
C
Di­
Syston
to
bluegill
sunfish
(
Lepomis
macrochirus)
.
Performed
by
Analytical
Biochemistry
Laboratories;
Submitted
by
Mobay
Corp.
Received
by
HED
on
2/
10/
88.
MRID#
40471106.

Grace,
T.
J.
,
K.
S.
Cain,
and
J.
L.
Delk.
1990.
Dissipation
of
disulfoton
in
California
soils.
Performing
Laboratory
Project
IDs:
ML022101,
89.023
Plot
24,
89.032
Plot
10,
892010.1­
6K,
M,
169W.
Submitting
Laboratory
Project
ID:
D1830089R01.
Mobay
Report
No.
100158.
Unpublished
study
performed
by
Plant
Sciences,
Inc.
,
Watsonville,
CA;
Siemer
and
Associates,
Inc.
,
Fresno,
CA
and
Pharmacology
and
Toxicology
Research
Laboratory
­
West,
Richmond,
Ca.
Submitted
by
Mobay
Corp.
,
Kansas
City,
Mo.

Graney,
R.
L.
,
1989.
MRID­
43042501.
Supplemental
submission
containing
raw
data
for:
uptake,
depuration
and
bioconcentration
of
14
C
Di­
Syston
to
bluegill
sunfish
(
Lepomis
macrochirus)
.
Mobay
Project
ID:
95078­
1.
Unpublished
study
performed
by
Analytical
Biochemistry
Lab.
,
Columbia,
MO
and
submitted
by
Miles,
Inc.
,
Kansas
City,
MO.

Hamman,
S.
D.
,
G.
Olson,
J.
Howard,
and
L.
J.
Lawrence.
Volatility
of
Di­
Syston
under
field
conditions.
Pharmacology
and
Toxicology
Research
Lab.
,
Submitted
by
Mobay
Corp.
,
Received
by
HED
on
2/
10/
88.
Accession
No.
40471105.

Hanlon,
C.
M.
,
and
K.
S.
Cain.
1987.
MRID­
43060101.
Identification
of
residues
from
bluegill
sunfish
exposed
to
14
C
Di­
Syston.
Laboratory
Project
ID:
DI­
03­
A;
Mobay
Project
ID:
95076.
Unpublished
study
performed
by
Analytical
Biochemistry
Laboratories
,
Columbia,
MO,
and
Mobay
Corporation,
Stilwell,
KS.
Submitted
by
Mobay
Corp.
Stilwell,
KS.

Howard,
P.
H.
(
Ed)
.
1991.
Handbook
of
Environmental
Fate
and
Exposure
Data
For
Organic
Chemicals.
Vol.
3.
Pesticides.
Lewis
Publishers.
,
Chelsea,
MI.

Jackson,
A.
B.
,
L.
O.
Ruzo,
and
L.
J.
Lawrence.
Soil
surface
photolysis
of
Di­
Syston
in
natural
sunlight.
Performed
by
Pharmacology
and
Toxicology
Research
Laboratory;
Submitted
by
Mobay
Corp.
,
Received
by
HED
on
2/
10/
88.
EPA
Accession
No.
40471103.

Kasper,
A.
M.
,
B.
A.
Shadrick,
K.
S.
Cain,
and
D.
L.
Green.
1992.
Anaerobic
aquatic
metabolism
of
14
C
disulfoton.
Miles
Study
No.
D1042401;
Miles
Report
No.
103945.
Unpublished
study
performed
and
submitted
by
Miles,
Inc.
,
Kansas
City,
MO.

Kesterson,
A.
B.
,
Ruzo,
L.
O.
,
and
Lawrence,
L.
J.
Photochemical
degradation
of
Di­
Syston
in
aqueous
solutions
under
natural
sunlight.
Performed
by
Pharmacology
and
Toxicology
Research
Submitted
by
Mobay
Corporation.
Received
by
HED
on
2/
10/
88.
EPA
Accession
89
No.
40471102.

Leimkuehler,
W.
M.
,
and
J.
S.
Thornton.
1986.
Hydrolysis
of
Di­
Syston
in
Aqueous
Sterile
Buffer
Solutions.
Mobay
Report
68943.

Leimkuehler,
W.
M.
&
S.
K.
Valdez.
1989.
Soil
Adsorption
and
Desorption
of
14
C
Di­
Syston.
Unpublished
Bayer
Report
No.
99721,
39
pages.
Laboratory
Report
No.
DI182101.
MRID
#
443731­
03.

Olson,
G.
L.
,
and
L.
J.
Lawrence.
1990.
Aerobic
metabolism
of
14C
Di­
Syston
in
sandy
loam
soil.
PTRL
Report
No.
1229;
Project
No.
320.
Unpublished
study
performed
by
Pharmacology
and
Toxicology
Research
Lab.
,
Lexington,
Ky.
,
and
submitted
by
Mobay
Corp.
,
Stillwell,
KS.
,
MRID­
41585101.

Obrist,
J.
J.
,
1979.
Leaching
Characteristics
of
Aged
Di­
Syston
Soil
Residues.
Mobay
Report
No.
67485
­
MRID
­
00145470.
Supplemental­
No
DER,
only
a
memorandum
with
very
little
information.

Puhl,
R.
J.
and
Hurley.
1978.
Soil
Adsorption
and
Desorption
of
Di­
Syston­
Mobay
Report
#
66792.
No
DER
was
written,
but
previous
a
reviewer
approved
the
Freundlich
K
values.
MRID
#
00145469.

Schmidt,
J.
,
T.
J.
Anderson,
and
D.
G.
Dyer.
1992.
Laboratory
volatility
of
disulfoton
from
soil.
ABC
Final
Report
No.
40259.
Miles
Study
No.
D1152101.
Miles
Report
No.
103907.
Unpublished
study
performed
by
ABC
Laboratories
Inc.
,
Columbia,
MO,
and
submitted
by
Miles
Inc.
,
Kansas
City,
MO.

90
91
APPENDIX
V:

ENVIRONMENTAL
FATE
DATA
REQUIREMENTS
FOR
Chemical
No:
032501
Disulfoton
Guideline
Use
Pattern
Does
EPA
Have
MRID
No.
More
Data
Data
to
Satisfy
the
Required?
Guideline
Req.
?

158.290
ENVIRONMENTAL
FATE
Degradation
Studies­
Lab:

161­
1
Hydrolysis
1,2,3
Yes
00143405
No
161­
2
Photodegradation
In
Water
1,
2,3
Yes
40471102
No
161­
3
Photodegradation
On
Soil
1,2,3
Yes
40471103
No
Metabolism
Studies­
Lab:

162­
1
Aerobic
Soil
1,2,3
Yes
43800101,40042201,41585101
No
162­
2
Anaerobic
Soil
1,2,3
No
No
162­
3
Anaerobic
Aquatic
1,2,3
No
(
43042503
2
)
Yes
162­
4
Aerobic
Aquatic
1,2,3
No
No
Mobilit
Studies:
:

163­
1
Leaching­
Adsorption/
Desorp.
1,
2,3
Yes
44373103,00145469,43042500,00145470
No
163­
2
Volatility
(
Lab)
1,
2,3
Yes
42585802
No
Dissipation
Studies­
Field:

164­
1
Soil
1,2,3
Yes
43042502
No
Accumulation
Studies:

165­
4
In
Fish
1,2,3
Partially
43042501,43060101,40471106,40471107
No
Ground
Water
Monitoring
Studies:

166­
1
Small­
Scale
Prospective
158.440
Spra
Drift:
:

201­
1
Droplet
Size
Spectrum
202­
1
Drift
Field
Evaluation
FOOTNOTES:
1
Submitted
study
was
classified
as
supplemental
and
must
be
repeated
in
order
to
fulfill
Guidelines
requirements
92
Appendix
VI:
Ecological
Effects
Data
Table
Generic
Data
Requirements
for
Disulfoton
(
parent
compound)
as
of
02/
02/
98
Data
Requirement
Composition
Does
EPA
MRID
Citation
Were
Data
Have
Data
Submitted
to
Satisfy
Under
FIFRA
Data
Req?
3(
c)
(
2)
(
B)
?
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_

158.490
Wildlife
and
Aquatic
Organisms
AVIAN
AND
MAMMALIAN
TESTING
71­
1
Avian
oral
LD50
TGAI
Yes
25525,00095655,
No
GS0102700,05008363,425858­
03
71­
2
Avian
dietary
LC50
TGAI
Yes
0094233,00058746,120480
No
71­
3
Wild
Mammal
Toxicity
TGAI
No
Yes
71­
4
Avian
Reproduction
TGAI
Yes
43032501,
43032502
No
71­
5
Simulated
and
actual
field
testing­
mammals
and
birds
TEP
Partially
00095658,00095657
No
AQUATIC
ORGANISM
TESTING
72­
1
Freshwater
fish
LC50
a.
Warmwater
TGAI
Yes
40098001,00068268,00003503
No
b.
Warmwater
TEP
Yes
229299,
00068268
1
No
c.
Coldwater
TGAI
Yes
40098001,00068268,00003503
No
d.
Coldwater
TEP
Yes
00068268
2
No
72­
2
Freshwater
Invertebrate
EC50
a.
TGAI
Yes
00003503,00143401
No
b.
TEP
No
No
c.
Degradate
Yes
425851­
09,42585­
12
No
72­
3
Marine/
Estuarine
Acute
LC50
a.
fish
TGAI
Yes
400716­
01
No
b.
mollusk
TGAI
Yes
400716­
02
No
c.
shrimp
TGAI
Yes
400716­
03
No
d.
fish
TEP
No
No
e.
mollusk
TEP
No
No
f.
shrimp
TEP
No
No
93
72­
4a
Fish
early
life
stage
TGAI
Yes
(
freshwater)
419358­
01
No
(
marine­
estuarine)
Yes
426290­
01
No
b
Aquatic
invert.
life­
cycle
TGAI
(
freshwater)
Yes
419358­
02
No
419358­
01
419358­
02
marine­
estaurine)
Yes
436109­
01
No
72­
5
Fish
Life
Cycle
TGAI
(
marine­
estuarine)
Yes
43960501
No
72­
6
Aquatic
organism
TGAI
Yes
(
See
Environmental
fate
guideline
165­
1)
No
accumulation
72­
7
Simulated
or
TEP
Yes
actual
field
testing
­
aquatic
organisms
158.150
PLANT
PROTECTION
­
Nontarget
Area
Phytotoxicity
TIER
I
122­
1
Seed
seedling
emergence
TGAI
No
Yes
122­
1
Vegetative
vigor
TGAI
No
Yes
122­
2
Aquatic
plant
growth
TGAI
No
No
TIER
II
123­
1
Seed
germ.
/
seedling
emergence
TGAI
No
No
123­
1
Vegetative
vigor
TGAI
No
No
123­
2
Aquatic
plant
growth
TGAI
No
No
TIER
III
124­
1:
Terrestrial
plant
field
testing
TEP
No
No
124­
2:
Aquatic
plant
field
testing
TEP
No
No
158.590
NONTARGET
INSECT
TESTING
­
POLLINATORS
141­
1
Honeybee
acute
contact
toxicity
TGA
Yes
00066220,05001991,05004151
No
141­
2
Honeybee
toxicity
TEP
Yes
0163423
No
of
residues
141­
5
Field
testing
for
pollinators
TEP
No
No
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
94
Appendix
VII.
Summary
of
Maximum
Percent
Crop
Areas
(
without
Land
Use
coverage)

CROP
MAXIMUM
PERCENT
CROP
AREA
(
as
a
decimal)
HYDROLOGIC
UNIT
CODE
(
8­
DIGIT
HUC)
STATE
Wheat
0.56
09010001
N.
Dakota
Cotton
0.20
08030207
Mississippi
Soybeans­
Cotton
0.49
(
0.31
soybeans,
0.18
cotton)
08020204
Missouri
All
Agricultural
Land
0.87
10230002
Iowa
Note
that
there
is
an
entry
for
 
All
Agricultural
Land
 
in
Appendix
2,
,
Table
1.
This
is
a
default
value
to
use
for
crops
for
which
no
specific
PCA
is
available.
It
represents
the
largest
amount
of
land
in
agricultural
production
in
any
8­
digit
hydrologic
unit
code
(
HUC)
watershed
in
the
continental
United
States.
95
Appendix
VIII.
PRZM
input
parameters
where
modifications
were
necessary
for
the
Index
Reservoir
(
IR)
Scenario
PRZM
variable
Farm
Pond
Value
IR
Scenario
Definition
AFIELD
10
ha
172.8
ha
area
of
plot
or
field
HL
374
m
scenario
specific
464
1
m
or
600m
Hydraulic
length
DRFT
0.01
ground
0.05
aerial
0.064
ground
0.16
aerial
Spray
drift
1
This
value
changed
between
versions
Guidance
document
and
modeling
of
data
during
the
development
of
the
Guidance
document.
The
PRZM
Input
file
and
the
EXAMS
environment
(
index
reservoir)
were
matched.

As
noted
above
in
above
table,
the
value
for
the
variable
HL
changed
between
Guidance
document
versions
and
modeling.
The
HL
(
hydraulic
length)
value
changed
from
464
m
to
600.
The
PRZM
input
files
were
in
agreement
with
whichever
environment
or
index
reservoir
that
was
used.
