Document ID: EPA-HQ-OPP-2005-0084-0038
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-07-12T04:00Z

UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,

PESTICIDES
AND
TOXIC
SUBSTANCES
MEMORANDUM
February
9,
2006
SUBJECT:
Fifth
re­
assessment
of
the
drinking
water
exposure
due
to
dimethoate
residues
in
drinking
water,
considering
new
aerobic
soil
metabolism,
and
foliar
dissipation
data
from
the
technical
registrant.
DB
Barcode:
D325417;
D323954;
D323951
PC
Code:
035001
TO:
Stephanie
Plummer,
Reregistration
Branch
1
Special
Review
and
Reregistration
Division
FROM:
R.
David
Jones,
Ph.
D.,
Senior
Agronomist
Environmental
Risk
Branch
4
THROUGH:
Betsy
Behl,
Chief
Environmental
Risk
Branch
4
Environmental
Fate
and
Effects
Division
This
document
is
the
fifth
re­
assessment
of
the
estimated
drinking
water
exposure
due
to
the
use
of
dimethoate
(
D287406,
D291603,
D305220,
D323594).
The
fourth
reassessment
considered
new
maximum
use
patterns
supported
by
the
registrant,
but
did
not
consider
new
aerobic
soil
metabolism
and
foliar
degradation
data
that
were
submitted
by
the
technical
registrant
following
the
public
phase
of
reregistration
in
November,
2005.
Since
the
Special
Review
and
Registration
Division
requires
that
these
additional
data
be
considered
in
the
drinking
water
assessment
in
order
to
negotiate
risk
management
options
with
the
registrant,
a
fifth
reassessment
is
now
necessary.

Based
on
the
results
of
the
fourth
reassessment,
about
half
the
food
crop
use
patterns
which
are
being
supported
by
the
registrant
do
not
result
in
exceedances
of
the
aggregate
dietary
risk
for
dimethoate.
The
purpose
of
this
reassessment
is
two­
fold:
to
clearly
identify
those
foodcrop
use
patterns
which
do
not
fill
the
risk
cup
as
a
result
of
occurrence
in
drinking
water,
and
to
incorporate
the
additional
aerobic
soil
metabolism
and
foliar
degradation
data
submitted
by
the
registrant
in
the
assessment.

As
a
consequence
of
this
additional
data,
the
aerobic
soil
metabolism
input
parameter
was
revised
from
6.909
to
3.304
d,
aerobic
aquatic
metabolism
from
13.82
to
6.608
d
and
foliar
degradation
rate
constant
from
0.24
d
­
1
to
0.164
d
­
1
.
Details
on
the
estimation
of
these
new
input
parameters
from
the
submitted
data
are
provided
in
the
body
of
the
document.
The
drinking
water
estimated
concentrations
(
DWECs)
for
the
broccoli
and
pecans
are
listed
in
Table
1
as
broccoli
is
now
the
use
pattern
with
the
largest
DWECs
and
pecans
has
the
smallest.
It
should
be
noted
that
broccoli
is
also
a
surrogate
for
cauliflower
and
celery,
which
are
vegetable
crops
with
the
same
maximum
use
pattern
and
grown
in
the
same
locations
in
California
as
broccoli.
Based
on
the
results
of
the
4
th
reassessment,
it
determined
that
the
EECs
for
pecans
fit
in
the
risk
cup
when
the
whole
thirty
year
times
series
was
used
in
the
dietary
risk
assessment,
and
those
for
broccoli
did
not.
Further
assessment
indicated
that
the
breakpoint
for
being
in
or
out
of
the
risk
cup
occurred
at
approximately
the
point
where
the
one
in
ten
year
peak
DWEC
was
at
100.
Note,
however,
that
determining
which
crops
are
in
or
out
of
the
risk
cup
with
certainty
requires
calculating
the
dietary
risk
with
the
whole
time
series.
Based
on
this,
DWEC
for
all
crops
in
the
fourth
reassessment
with
DWECs
larger
than
tomatoes,
that
is
a
peak
DWEC
of
102
µ
g
 
L
­

1,
were
recalculated
in
the
assessment,
as
it
is
expected
the
other
use
patterns
will
generate
EEC
that
are
in
the
risk
cup.
In
addition,
pecans
was
assessed
as
it
has
the
lowest
DWECs.
The
crops
that
were
not
assessed
and
are
expected
to
be
in
the
risk
cup
are
the
national
use
pattern
for
cherries,
western
citrus,
cotton,
kale,
melons,
mustard
greens,
pears,
peas,
peppers,
swiss
chard,
endive,
and
turnips.

Details
on
the
generation
of
these
DWECs
are
provided
in
the
body
of
the
document.
The
monitoring
data
analysis
and
drinking
water
treatment
sections
have
been
omitted
from
this
reassessment
as
they
are
unchanged
from
previous
assessment
(
D323594).

Table
1.
Recommended
DWECs
for
surface
water
based
on
the
maximum
use
rate
on
broccoli
and
pecans.
Broccoli
is
a
surrogate
for
cauliflower
and
celery.
Broccoli
DWECs
were
the
largest
estimated
and
pecans
were
the
lowest.
These
surface
water
EECs
include
toxicity
adjustment
factors
of
12
for
acute
DWECs
and
3
for
chronic
and
cancer
to
account
for
the
conversion
to
omethoate
during
drinking
water
treatment.

Crop
Acute
DWEC
Chronic
DWEC
Cancer
DWEC
­­­­­­­­­­­­­­­­­­­­­­­­
µ
g
L
­
1
dimethoate
equivalents
­­­­­­­­­­­­­­­­
­­­­­­­­

Broccoli,
Cauliflower
and
Celery
380
9.74
4.81
Pecans
14.1
0.13
0.08
The
point
DWECs
for
acute
and
chronic
exposure
in
Table
1
represent
that
values
the
would
be
expected
to
be
equaled
or
exceeded
once
every
10
years.
In
addition
to
these
point
estimates,
the
30
year
time
series
for
these
two
simulations
as
well
as
four
others,
MS
cotton,
FL
tomatoes,
ND
Safflower,
and
Maine
potatoes,
were
provided
to
Health
Effects
Division
for
use
in
refined
aggregate
risk
assessment
in
an
Excel
Spreadsheet,
 
Dimethoate
DW
time
series
01
17
2006.
EXC ,
dated
January
17,
2006.

Fate
and
Transport
Characterization
Dimethoate
is
a
highly
mobile,
yet
relatively
non­
persistent
organophosphate
insecticide.
The
primary
route
of
dissipation
is
microbially­
mediated
hydrolytic
and
oxidative
degradation
in
aerobic
soil,
particularly
under
moist
conditions,
with
a
mean
half­
life
of
2.5
days
estimated
from
rates
for
four
different
soils
(
Table
2).
Two
non­
volatile
degradates,
desmethyl
dimethoate
and
dimethylthiophosphoric
acid,
were
identified
but
were
present
at
levels
less
than
2%
during
the
aerobic
soil
metabolism
study.
Dimethoate
only
photodegrades
slowly
in
water
(
T
1/
2
=
353
days)
while
no
significant
degradation
occurred
in
the
soil
photolysis
study
.
It
hydrolyzes
very
slowly
in
sterile
buffered
solutions
at
pH s
5
and
7
(
156
and
68
days,
respectively),
but
under
alkaline
conditions,
it
degrades
rapidly
to
desmethyl
dimethoate
and
dimethylthiophosphoric
acid
with
a
half­
life
of
4.4
days
at
pH
9.
Under
anaerobic
soil
conditions,
dimethoate
does
degrade,
though
not
as
rapidly
as
under
aerobic
conditions.
The
anaerobic
half­
life
was
found
to
be
approximately
22
days,
with
the
major
non­
volatile
degradate
being
desmethyl
dimethoate.

Although
dimethoate
does
not
photodegrade
on
soil
(
the
degradation
rates
and
products
were
essentially
the
same
for
the
light­
exposed
and
dark
control),
the
study
did
provide
information
on
the
degradation
of
dimethoate
on
a
thin
layer
of
somewhat
dry
soil.
Under
these
conditions,
the
soil
degradates
(
dimethylphosphoric
acid
and
dimethylthiophosphoric
acid)
accumulated
and
persisted
to
a
much
greater
extent
than
in
the
aerobic
soil
metabolism
study.
Therefore,
in
the
field,
these
degradates
may
persist
under
dry
conditions
at
the
soil
surface.

Table
2.
Environmental
fate
data
for
dimethoate.

Study
Value
Source
Hydrolysis
(
161­
1)
Half­
life
pH
5:
156
d
pH
7:
68
d
pH
9:
4.4
d
MRID
00159761
Aqueous
Photolysis
Half­
life
353
d
MRID
00159762
Soil
Photolysis
Half
­
life
no
significant
degradation
MRID
43276401
Soil
Water
Partition
Coefficient
(
Kd)
sand
0.06
L
(
kg­
soil)­
1
sandy
loam:
0.30
L
(
kg­
soil)­
1
silt
loam:
0.57
L
(
kg­
soil)­
1
clay
loam:
0.66
L
(
kg­
soil)­
1
MRID
00164959
Aerobic
Soil
Metabolism
Half­
life
2.2
d
Riverside
:
2.0
d*
Middelfield:
2.0
d*
Somersham:
3.7
d*
MRID
42843201
MRID
46719202
MRID
46719202
MRID
46719202
Anaerobic
Soil
Metabolism
Half­
life
22
d
MRID
42884402
Foliar
Dissipation
Half­
life
mean
value:
2.8
d
see
Table
7
Field
Dissipation
DT50
CA
loamy
sand:
11
d
CA
sandy
loam
~
9
d
CA
sandy
loam:
~
16
d
TX
silt
loam
~
9
d
Chenango
gravelly
silt
loam:
<
5
d
MRID
42884403
MRID
42884403
MRID
42884403
MRID
43388001
MRID
43388002
*
Half­
lives
were
adjusted
to
a
standard
temperature
of
25
°
C
from
an
experimental
temperature
of
20
°
C
using
a
Q10
of
2.3.

Dimethoate
is
highly
mobile
in
soil.
In
a
soil
column
leaching
study,
72­
100%
of
the
applied
radioactivity
was
eluted
from
the
columns
(
loam,
silt
loam,
sandy
loam,
and
sand).
Calculated
Kd
values
based
on
these
column
studies
ranged
from
0.06
L
kg­
1
for
the
sand
to
0.66
L
kg
­
1
for
the
clay
loam.
Degradate
mobility
has
not
been
well
defined;
however,
based
on
the
aged
leaching
data
as
well
as
the
metabolism
data,
degradates
are
not
expected
to
be
sufficiently
persistent
to
move
through
the
soil
profile
to
move
through
leach
through
the
soil
profile.
Note
that
Kds
estimated
from
soil
column
leaching
studies
tend
to
be
much
less
precise
than
those
estimated
from
batch
equilibrium
studies.

A
study
measuring
the
volatility
of
dimethoate
from
the
soil
surface
showed
this
is
not
expected
to
be
a
significant
route
of
dissipation.
After
30
days,
only
2.7%
of
the
applied
radioactivity
had
volatilized,
0.7%
of
which
was
CO
2
.
The
majority
of
the
radioactivity
(
83%)
was
extracted
from
the
soil
and
most
of
this
(
93.2%)
was
dimethoate.
It
should
be
noted
that
the
rate
of
degradation
in
this
laboratory
volatility
study,
compared
with
the
aerobic
soil
metabolism
study,
was
particularly
slow.
The
slower
rate
in
the
volatility
study
may
be
explained
by
the
difference
in
the
soil
moisture
content
in
the
two
studies,
as
dimethoate
metabolism
appears
to
be
very
sensitive
to
soil
moisture.

Omethoate,
a
toxicologically
significant
oxygen
analogue
metabolite
of
dimethoate,
also
known
as
dimethoxon
and
dimethoate
oxygen
analog,
was
found
under
field
conditions,
though
it
had
not
been
detected
in
the
laboratory
studies
(
Table
3).
The
presence
of
omethoate
has
been
established
in
insects,
plants,
and
mammals
(
World
Health
Organization,
1989).
In
the
dimethoate
field
dissipation
studies
discussed
below,
the
only
degradate
analyzed
for
was
omethoate.
Two
degradates
identified
in
the
laboratory
studies,
O,
O­
dimethylphosphorothioate
and
O­
desmethyldimethoate
were
included
in
the
analysis
by
using
the
total
toxic
residues
method
of
estimating
half­
lives.
This
method
uses
the
sum
of
the
parent
plus
the
toxic
residues
as
the
concentration
estimate
in
the
estimation
of
the
degradation
rate.
It
assumes
that
degradates
are
of
equal
toxicity
to
the
parent.

Foliar
Dissipation.
Data
from
Willis
and
McDowell,
1987
and
from
magnitude
of
residue
studies
submitted
by
the
technical
registrant
were
used
to
assess
foliar
dissipation.
(
This
assessment
has
been
updated
from
the
previous
assessment
by
the
inclusion
of
degradation
information
from
the
Magnitude
of
Residue
studies.)
Willis
and
McDowell
is
a
summary
of
data
on
the
persistence
of
pesticides
on
foliage.
In
this
document,
thirty­
three
measurements
of
dimethoate
dissipation
on
foliage
were
identified
that
were
on
whole
plant
or
on
foliage.
Of
these,
4
were
done
in
Egypt,
and
it
could
not
be
determined
whether
they
were
appropriate
for
assessing
foliar
dissipation
in
the
United
States,
so
they
were
not
used.
For
the
remaining
29
(
Table
4),
the
mean
foliar
dissipation
half­
life
was
3.7
days,
and
the
upper
90%
confidence
bound
on
the
mean
was
4.2
days.
Note
that
these
were
all
field
studies,
and
that
these
are
dissipation
rather
than
degradation
half­
lives.
In
some
cases,
the
author
of
the
study
noted
when
rain
occurred
during
the
trial.
However,
absence
of
that
information
in
the
table
is
an
indication
that
the
author
did
not
note
what
precipitation
occurred
rather
than
the
absence
of
precipitation.

Table
3.
Maximum
degradate
amounts
as
a
percentage
of
the
parent
applied
in
laboratory
degradation
studies
for
dimethoate.

Degradate
(
percent
of
initial
dimethoate
concentration)

Study
A
B
C
D
E
F
G
H
Hydrolysis
at
pH
5
(
§
161­
1)
12.2
(
30
d)

Hydrolysis
at
pH
7
(
§
161­
1)
1.9
(
30
d)
22.1
(
30
d)
1.6
(
30
d)

Hydrolysis
at
pH
9
(
§
161­
1)
36.0
(
30
d)
62.2
(
21
d)
1.3
(
7
d)

Aqueous
Photolysis
(
§
161­
2)
4.2
(
4
d)

Soil
Photolysis
(
§
161­
3)
27.9
(
30
d)
30.4
(
20
d)
4.6
(
30
d)
1.9
(
30
d)
6.6
(
30
d)
12.2
(
30
d)

Aerobic
Soil
Metabolism
(
§
162­
1)
0.7
(
2
d)
2.0
(
2
d)
75
(
181
d)
21
(
30
d)

Anaerobic
Soil
Metabolism
(
§
162­
2)
5.1
(
16
d)
10.1
(
16
d)
41.0
(
62
d)
23
(
62
d)

Aged
Residue
Leaching
(
§
163­
1)
3.3
(
30
d)
29.7
(
30
d)
0.8
(
30
d)
27.9
(
30
d)

Volatility
(
§
163­
2)
2.0
(
30
d)
0.7
(
30
d)
5.7
(
30
d)
10
(
30
d)

Soil
Dissipation
in
NY
Field*
(
§
164­
1)
0.85
(
3
d)

Soil
Dissipation
in
TX
Field*
(
§
164­
1)
1.3
(
6
d)

Soil
Dissipation
in
CA
Field**
(
§
164­
1)
24
(
3
d)
3.7
(
18
d)
22
(
18
d)

A:
dimethylphosphoric
acid
B:
O,
O­
dimethylphosphorothioate
(
dimethylthiophosphoric
acid)
C:
O­
desmethyldimethoate
D:
omethoate
(
dimethoxon)
E:
volatile
organic
radiocarbon
F:
14CO2
G:
unidentified
degradate
H:
non­
extractable
radioactivity
*:
Percentage
is
calculated
from
maximum
reported
mean
concentration
in
0­
6"
soil
column.
**:
Percentages
are
calculated
from
maximum
reported
mean
concentrations
in
0­
6"
soil
columns
for
green
bean,
grape,
and
bare
ground
plots,
respectively.

In
addition
to
the
studies
discussed
above,
a
registrant­
submitted
study
(
MRID
464864­
01)
provided
information
on
the
degradation
of
dimethoate,
and
the
formation
and
decline
of
omethoate
on
ground­
level
vegetation
and
canopy
arthropods
in
a
mandarin
orchard
in
Spain.
The
half­
life
of
dimethoate
was
found
to
be
1.7
days
on
the
vegetation
and
0.86
days
on
the
canopy
arthropods.
Using
a
kinetics
model
that
assumed
that
100%
of
the
dimethoate
formed
omethoate,
the
degradation
half­
life
of
omethoate
was
determined
to
be
0.33
days
on
the
foliage
and
0.30
days
on
the
arthropods.
For
plant
materials,
these
data
are
within
the
range
of
half­
lives
seen
above
for
the
parent.
No
other
measurements
exist
for
omethoate
on
plant
material
or
either
omethoate
or
dimethoate
in
arthropods.

Table
4.
Foliar
dissipation
data
for
dimethoate.

Crop
Author
Comment
T
½
(
days)

apple
Pree
et
al.
1976
5.4
alfalfa
Shaw
and
Ziener,
1964
1.4
apple
Pree
et
al.
1976
7.2
apple
Pree
et
al.
1976
rained
80
mm
2.6
apple
Pree
et
al.
1976
rained
11
mm
4.1
birdsfoot
trefoil
Shaw
and
Ziener,
1966
2.1
sorghum
Dorough
et
al.
1966
4
ladino
clover
Shaw
and
Ziener,
1966
1.8
lemon
Bellows
et
al.,
1985
2.2
coastal
bermuda
grass
Beck
et
al.,
1966
22.6
mm
rain
3.1
corn
Beck
et
al.,
1966
90.2
mm
rain
2.7
soybeans
Beck
et
al.,
1966
0
mm
rain
0.9
beet
Vail
et
al.,
1967
0
mm
rain
2.5
broccoli
Nelson
et
al.,
1966
3
cabbage
Nelson
et
al.,
1966
1.7
chard
Vail
et
al.,
1967
5.1
mm
rain
2.6
collards
Nelson
et
al.,
1966
2.5
leaf
lettuce
Vail
et
al.,
1967
5.1
mm
rain
2.8
lima
beans
Nelson
et
al.,
1966
2.2
snap
beans
Nelson
et
al.,
1966
2.6
soybeans
Nelson
et
al.,
1966
1.2
turnip
Vail
et
al.,
1967
83.8
mm
rain
3.1
turnip
Nelson
et
al.,
1966
3.2
wheat
Lee
and
Westcott,
1981
2.5
wheat
MRID
466780­
01
8.0
wheat
MRID
466780­
01
16.3
wheat
MRID
466780­
05
3.6
wheat
MRID
466780­
05
6.6
wheat
MRID
466780­
10
15.6
Use
and
Usage
In
the
previous
assessment,
the
exposure
in
drinking
water
from
twenty­
five
food
use
crops
which
the
technical
registrant
intends
to
support
were
assessed
(
D323594).
The
registrant
has
proposed
that
the
use
patterns
that
were
used
for
the
Magnitude
of
Residue
Studies
be
the
maximum
label
rates
for
the
relevant
crops.
Based
on
that
assessment,
HED
determined
that
all
use
patterns
that
had
peak
1­
in­
10­
year
DWECs
less
than
that
for
tomatoes
would
have
acceptable
dietary
risk.
These
crops
are
cherries
(
national
use
pattern),
western
citrus,
cotton,
kale,
melons,
mustard
greens,
pears,
peas,
pecans,
peppers,
swiss
chard,
endive,
and
turnips.
The
remaining
use
patterns
are
being
re­
evaluated
in
this
assessment,
and
are
listed
in
Table
5.
In
addition,
pecans,
which
the
lowest
DWECs
for
any
crop
is
reassessed.
For
the
purposes
of
this
assessment,
these
uses
have
been
placed
into
groups.
Each
group
has
the
same
maximum
use
pattern
and
consists
of
crops
which
are
grown
in
roughly
the
same
areas
using
similar
use
patterns.
Only
one
crop
was
simulated
for
each
class
and
serves
as
a
surrogate
for
the
others
in
its
class.
Scenarios
selected
to
represent
each
crop
group
are
described
in
the
Scenario
section
below.

As
noted
in
the
previous
assessment,
there
are
a
number
of
non­
food
uses
which
have
poorly
specified
use
patterns
(
i.
e.
number
of
application,
application
interval)
that
have
not
been
assessed
and
are
not
expected
to
be
in
the
risk
cup.
These
use
patterns
can
be
assessed
when
more
defined
se
patterns
become
available.
Furthermore,
there
are
a
number
of
use
patterns
that
could
not
be
assessed
as
the
label
directions
could
not
be
resolved
to
a
use
pattern
with
a
lb/
acre
basis
which
is
necessary
for
model
input.
Details
on
these
use
patterns
are
in
the
previous
assessment
(
D323594).
Table
5.
New
maximum
use
patterns
supported
by
the
technical
registrant
for
dimethoate
were
not
shown
to
have
acceptable
dietary
risk
(
food
+
water)
from
the
previous
drinking
water
assessment.

Crop
Group*
Single
App.
Rate
(
lb
acre
­
1
)
Number
of
Applications
(
per
year)
Application
Interval
(
days)
Application
Method
Citrus
A
1.0
2
31
aerial
Wheat
B
0.67
2
5
aerial
Broccoli
C
0.5
6
7
aerial
Cauliflower
C
0.5
6
7
aerial
Celery
C
0.5
6
7
aerial
Alfalfa
for
hay
F
0.5
1
per
cutting
7
aerial
Beans,
edible
H
0.5
2
7
aerial
Lentils
J1
0.5
2
7
aerial
Potatoes
J3
0.5
2
7
aerial
Soybeans
J4
0.5
2
7
aerial
Tomatoes
J5
0.5
2
6
aerial
Corn,
field
K
0.5
3
7
aerial
Safflower
L
0.5
2
14
aerial
Sorghum
K
0.5
3
7
aerial
Pecans
M
0.33
1
NA
aerial
Leaf
lettuce
N
0.25
4
5
aerial
*
Crop
groups
have
the
same
codes
as
in
the
previous
assessment
and
are
no
longer
consecutive.

Models
For
Tier
2
surface­
water
drinking
water
assessments,
two
models
are
used
in
tandem.
The
Pesticide
Root
Zone
Model
(
PRZM)
simulates
fate
and
transport
on
the
agricultural
field.
The
version
of
PRZM
(
Carsel
et
al.,
1998)
used
was
PRZM
3.12
beta,
dated
May
24,
2001.
The
water
body
is
simulated
with
EXAMS
version
2.98,
dated
July
18,
2002
(
Burns,
1997).
Tier
2
simulations
are
run
for
multiple
(
usually
30)
years
and
the
reported
DWECs
are
the
concentrations
that
are
expected
once
every
ten
years
based
on
the
thirty
years
of
daily
values
generated
by
the
simulation.
PRZM
and
EXAMS
were
run
using
the
PE4
shell,
dated
May
14,
2003,
which
also
summarizes
the
output.
Scenarios
Scenarios
used
for
Tier
2
drinking
water
exposure
assessment
consist
of
two
parts
(
Table
3).
A
standard
part
describes
the
water
shed
geometry
and
is
the
same
for
all
scenarios.
This
consists
of
a
172.8
ha
watershed
which
drains
into
a
5.26
ha
pond,
2.74
meters
deep,
called
the
index
reservoir
scenario.
The
index
reservoir
has
a
constant
release
which
is
set
to
equal
the
mean
runoff
flow
into
the
reservoir
at
the
location
being
simulated.
The
second
part
varies
with
each
crop
and
consists
of
the
weather,
soil
and
crop
growth
information
for
growing
the
crop
in
a
particular
location.
These
are
chosen
to
represent
a
site
that
is
more
vulnerable
than
most
sites
used
to
grow
the
crops
in
that
group.
As
a
goal,
these
sites
are
intended
to
represent
a
site
that
is
more
vulnerable
to
pesticide
contamination
than
the
majority
(
e.
g.,
90%
of
the
sites
that
could
be
used
to
grow
the
crop).
Since
these
scenarios
are
currently
selected
by
best
professional
judgement,
there
is
a
lack
of
precision
in
achieving
this
90%
site
goal.
As
noted
in
the
use
characterization
(
Table
5),
each
crop
has
been
assigned
to
a
crop
group.
All
the
crops
in
a
crop
group
have
similar
agronomic
practices,
as
well
as
dimethoate
use.
One
crop
in
the
group
has
been
selected
as
a
surrogate
for
the
exposure
from
the
group
as
a
whole.
The
scenarios
selected
to
describe
each
crop
are
in
Table
6.
In
many
cases,
the
scenario
is
specifically
designed
for
that
particular
crop,
Maine
potatoes,
for
example.
In
other
cases,
the
scenario
serves
as
a
good
general
scenario
for
a
group
of
crops.
For
example,
CA
lettuce
is
a
good
general
scenario
for
vegetable
crops
grown
in
coastal
California.
In
other
cases,
for
which
no
good
specific
or
general
scenario
was
available
for
the
crop
group,
the
nearest
best
surrogate
was
chosen
to
represent
these
crops.
For
example,
no
lentil
scenario
was
available;
however,
lentils
are
grown
in
the
northern
great
plains
and
a
scenario
for
another
agronomic
crop
grown
in
this
region
was
available,
North
Dakota
wheat
and
this
was
chosen
as
the
best
available
surrogate
for
lentils.
A
more
detailed
discussion
of
the
considerations
for
the
selection
of
each
scenario
follows.
Additional
information
on
these
scenario
is
in
Pesticide
Root
Zone
Model
Field
and
Orchard
Crop
Scenario
Metadata,
(
EFED,
2003).

Alfalfa.
Dimethoate
has
two
different
use
patterns
when
being
applied
to
alfalfa,
one
for
seed
crops
and
the
other
for
hay.
The
technical
registrant
is
apparently
not
supporting
the
seed
use.
The
Minnesota
alfalfa
scenario
was
chosen
to
represent
a
site
used
for
alfalfa
agriculture
that
is
more
vulnerable
than
most
sites
used
for
this
crop
nationally.
The
PCA
is
the
national
default
PCA
of
0.87,
as
alfalfa
is
grown
on
a
widespread
basis
across
the
country.

Beans.
The
MI
Bean
scenario
is
being
used
to
represent
beans
on
a
national
basis,
including
those
that
will
be
harvested
and
eaten
fresh
(
succulent),
and
those
that
will
be
harvested
dry.
These
include
snap
beans
and
lima
beans.
It
does
not
include
 
southern
peas 
such
and
blackeyed
peas,
crowder
peas,
and
cowpeas.
The
Regional
PCA
for
the
Great
Lakes
Region
of
0.77
was
used
for
beans.

Table
6.
Scenarios
used
to
represent
crops
for
Tier
2
modeling
of
dimethoate.

Crop
PCA
Location
Soil
Weather
First
App.

Date
Alfalfa
0.87
Polk
County,
MN
Bearden
silty
clay
loam
Fargo,
ND
May
15
Cherries
(
24c)
0.56
Fresno,
CA
Exeter
loam
Fresno,
CA
March
14
Beans,
dry
0.77
Huron
Co,
MI
Toledo
silty
clay
loam
Flint,
MI
May
15
Broccoli
0.56
Monterey
Co,
CA
Placentia
sandy
loam
Santa
Maria,
CA
January
15
Crop
PCA
Location
Soil
Weather
First
App.

Date
Citrus
0.38
Collier
Co.,
FL
Wabasso
sand
Miami,
FL
July
1
Corn
0.44
Darke
Co,
OH
Cardington
silt
loam
Vandalia,
OH
July
1
Cotton
0.20
Yazoo
Co.,
MS
Loring
silt
loam
Jackson,
MS
May
15
Leaf
lettuce
0.56
Monterey
Co,
CA
Placentia
sandy
loam
Santa
Maria,
CA
January
15
Lentils
0.87
Cass
Co,
ND
Bearden
silty
clay
loam
Fargo,
ND
May
15
Pecans
0.38
Mitchell
&
Dougherty
Co,
GA
Greenville
fine
sandy
loam
Tallahassee,
FL
April
30
Potatoes
0.87
Aroostook
Co,
ME
Conant
silt
loam
Caribou,
ME
June
15
Safflower
0.87
Cass
Co.,
ND
Bearden
silty
clay
Fargo,
ND
May
15
Sorghum
0.87
Osage
Co,
KS
Dennis
silt
loam
Topeka,
KS
June
1
Soybeans
0.41
Yazoo
Co,
MS
Loring
silt
loam
Jackson,
MS
May
1
Tomatoes
0.38
Manatee
Co,
FL
Riviera
sand
West
Palm
Beach,
FL
January
25
Wheat
0.56
Cass
Co.,
ND
Bearden
silty
clay
Fargo,
ND
May
15
Broccoli.
Broccoli
is
being
simulated
in
coastal
California.
Broccoli
is
serving
as
a
surrogate
for
two
other
crops,
cauliflower
and
celery.
These
two
crops
have
identical
label
use
patterns,
and
are
also
grown
predominantly
in
coastal
California.
The
CA
lettuce
scenario
is
being
used
for
the
broccoli
simulations
as
this
scenario
is
a
good
general
vegetable
scenario
for
the
Coastal
Valley
of
California
and
a
substantial
portion
of
the
broccoli
grown
in
California
is
grown
in
the
Coastal
Valley.
The
description
of
the
California
lettuce
scenario
is
in
the
leaf
lettuce
description
below.
The
PCA
for
the
California
Basin
of
0.56
was
used
with
broccoli.

Cherries.
There
is
a
national
use
pattern
for
cherries
and
this
use
pattern
has
dietary
risk
which
are
below
the
regulatory
level
of
concern.
However,
there
are
also
24(
c)
labels
for
use
of
dimethoate
on
cherries
which
are
restricted
to
states
of
Idaho,
Montana,
Oregon,
Utah,
and
Washington
with
a
higher
application
rate.
This
use
pattern
did
not
fit
in
the
risk
cup
in
the
previous
assessment
due
to
drinking
water.
Since
there
is
currently
no
cherry
scenario
in
these
western
states,
the
California
fruit
scenario
is
being
used
as
a
surrogate.
The
California
fruit
scenario
is
a
general
orchard
scenario,
which
was
selected
to
represent
cherry
orchards
on
the
eastern
side
of
the
Central
Valley.
It
is
a
reasonable
surrogate
for
orchard
crops
which
are
grown
predominantly
in
states
along
the
Pacific
Coast.
The
Regional
PCA
for
the
Columbia
Basin
PCA
of
0.63
was
used
with
the
west
coast
cherries.

Citrus.
The
citrus
use
covers
all
citrus
crops.
There
is
a
general
citrus
use
pattern,
and
there
are
similar
or
identical
specific
use
patterns
for
most
citrus
crops,
including
lemons,
limes,
oranges,
grapefruit,
pummelo,
tangelo,
tangerine,
and
kumquat.
The
scenario
selected
to
represent
citrus,
is
in
Florida.
The
previous
assessment
showed
that
California
citrus
has
dietary
risk
below
the
level
of
concern
and
is
thus
not
assessed
here..
However,
the
risks
in
Florida
have
not
yet
been
dismissed,
so
it
is
again
assessed
here.
Note
that
based
on
information
from
SRRD,
the
majority
of
dimethoate
use
on
citrus
occurs
in
California,
so
the
estimated
risks
in
Florida
represent
the
potential
is
usage
increased
in
that
state
rather
than
the
risks
that
are
present
based
on
current
usage.
For
the
Florida
simulation,
the
PCA
for
the
southeastern
drainages
of
0.38
was
used.
Corn.
The
field
used
to
represent
corn
production
in
Ohio
is
located
in
Darke
and/
or
Pickaway
Counties,
although
the
crop
is
grown
extensively
throughout
the
state.
This
site
is
the
standard
scenario
used
to
estimate
exposure
on
a
national
basis
for
corn
production
as
it
is
more
vulnerable
to
high
exposure
from
pesticides
than
most
sites
used
to
grow
this
crop.
The
PCA
for
this
assessment
was
the
corn
specific
PCA
of
0.44
Leaf
lettuce.
A
major
leaf
lettuce
production
area
is
the
Coastal
Valley
of
California.
Since
lettuce
is
predominantly
grown
on
the
West
Coast,
this
scenario
is
used
to
represent
lettuce
production
nationally.
The
PCA
for
the
California
basin
of
0.56
was
used
for
this
crop.

Lentils.
There
is
currently
no
available
scenario
for
lentils.
The
North
Dakota
wheat
scenario
is
being
used
as
a
surrogate
scenario
for
this
crop.
Using
this
scenario
for
lentils
should
be
protective
of
watersheds
where
lentils
are
grown
on
a
national
basis.
The
Missouri
Basin
Regional
PCA
of
0.87,
which
is
the
same
as
the
default
PCA
was
used
to
calculate
the
DWEC
for
lentils.

Pecans.
The
field
used
to
represent
pecan
production
in
Georgia
is
located
in
Mitchell
or
Dougherty
County
in
Southwest
Georgia
(
MLRA133)
and
the
weather
station
representing
the
grove s
weather
is
located
in
Macon,
GA.
This
scenario
is
more
vulnerable
than
most
sites
used
to
grow
pecans
on
a
national
basis
and
exposure
estimates
based
on
this
scenario
are
expected
to
be
protective
of
watersheds
where
pecans
are
grown
on
a
national
basis.
The
Southeastern
Basins
PCA
of
0.38
was
used
for
these
DWECs.

Potatoes.
The
field
used
to
represent
potato
production
in
Maine
is
located
in
Aroostook
County
(#
1
producing
county
in
Maine)
in
northeastern
Maine
(
MLRA143/
146),
although
potato
production
areas
include
other
regions
of
Maine.
Aroostook
County
produces
approximately
90
percent
of
Maine s
potatoes.
This
scenario
is
more
vulnerable
than
most
sites
used
to
grow
potatoes
nationally
and
exposure
estimates
based
on
this
scenario
are
expected
to
be
protective
of
watersheds
where
potatoes
are
grown
on
a
national
basis.

Safflower.
There
is
currently
no
available
scenario
for
safflower.
The
North
Dakota
wheat
scenario
is
being
used
as
surrogate
scenario
for
this
crop.
North
Dakota
has
the
3
rd
largest
safflower
acreage
after
California
and
Montana
with
10,522,777
acres
out
of
270,105,054
acres
nationally
(
3.9%).
The
North
Dakota
wheat
scenario
was
also
used
for
simulating
dimethoate
application
to
wheat
and
lentils
is
described
in
the
wheat
section
below.
The
regional
PCA
for
the
Missouri
Basin
of
0.87
was
used
for
safflower,
which
is
the
same
value
as
the
national
default
PCA.

Sorghum.
The
field
used
to
represent
sorghum
production
in
Kansas
is
located
in
Osage
County
in
the
east
central
portion
of
the
state
although
the
crop
is
grown
throughout
Kansas.
This
scenario
is
more
vulnerable
than
most
sites
used
to
grow
sorghum
nationally
and
exposure
estimates
based
on
this
scenario
are
expected
to
be
protective
of
watersheds
where
sorghum
is
grown
on
a
national
basis.
The
Regional
PCA
for
the
Missouri
River
Basin
of
0.87
was
used
for
sorghum
as
it
is
widely
grown
in
that
basin.

Soybeans.
The
field
used
to
represent
soybean
production
in
Mississippi
is
located
in
Yazoo
County.
According
to
the
1997
Census
of
Agriculture,
Mississippi
harvested
more
than
2
million
acres
of
soybeans
and
ranks
12
th
in
production
in
the
United
States.
This
scenario
is
more
vulnerable
than
most
sites
used
to
grow
soybeans
nationally
and
exposure
estimates
based
on
this
scenario
are
expected
to
be
protective
of
watersheds
where
soybeans
are
grown
on
a
national
basis.
The
soybeans
specific
PCA
of
0.41
was
used
to
calculate
these
DWECs.

Tomatoes.
The
Florida
tomato
scenario
was
used
for
these
simulations
as
it
is
protective
of
watersheds
where
tomatoes
are
grown
on
a
national
basis.
The
field
used
to
represent
tomato
production
in
Florida
is
located
in
Manatee
County
(#
1
producing
Florida
county)
in
southwest
Florida
(
MLRA
155),
although
tomato
production
areas
include
other
regions
of
Florida,
such
as
the
Everglades
Agricultural
Area
and
west­
central
and
southeastern
regions.
According
to
the
1997
USDA
Census
of
Agriculture,
Florida
is
the
major
producer
of
truck
crops
and
is
the
highest
producer
of
fresh
market
tomatoes
in
the
United
States.
Tomatoes
and
other
truck
crops
are
generally
grown
on
 
muck
soils, 
in
Florida,
but
tomatoes
are
grown
on
sandy
soils
as
well.
The
relative
vulnerability
of
muck
soils
agriculture
to
the
simulated
scenario
is
not
currently
well
characterized.
The
Southeastern
Basins
PCA
of
0.38
was
used
for
these
DWECs.

Wheat.
The
North
Dakota
wheat
scenario
was
chosen
to
represent
this
group
as
this
scenario
is
designed
to
be
protective
of
watersheds
where
wheat
is
grown
on
a
national
basis.
The
crop
specific
PCA
for
wheat
of
0.56
was
used
to
calculate
the
DWECs.

Management
Practices
The
application
method
used
in
these
simulations
was
aerial,
as
there
is
no
restriction
from
its
use
on
any
of
these
crops,
and
aerial
application
generates
the
greatest
drift,
and
thus
the
highest
exposure
estimates.
It
will
also
be
the
typical
practice
for
agronomic
crops
after
the
canopy
has
closed.
For
vegetable
crops,
ground
spray
would
be
the
typical
practice
and
spray
blast
for
orchard
crops.
For
aerial
applications,
16%
drift
was
assumed
for
each
application
with
a
95%
application
efficiency.

Particular
Considerations
for
Individual
Crops
Alfalfa.
For
application
of
dimethoate
to
alfalfa
for
hay,
only
one
application
per
cutting
is
allowed.
In
Minnesota,
there
will
be
a
maximum
of
four
cuttings
a
year,
so
these
were
spaced
30
days
apart
to
cover
the
growing
season.
The
date
of
first
application
was
May
15.

Beans.
Initial
application
was
made
shortly
after
emergence
on
May
15.

Leaf
lettuce.
A
first
application
date
of
January
15
was
chosen,
as
lettuce
is
grown
during
the
winter
along
the
California
coast,
and
this
is
the
period
of
high
rainfall
in
this
part
of
the
country.

Pecans.
Date
of
first
application
is
one
week
after
first
leaf
out,
as
indicated
in
the
scenario
meta­
data.

Tomatoes.
The
management
scenario
represents
a
winter
crop
of
tomatoes.
The
first
application
was
made
on
January
25,
which
is
14
days
after
emergence
on,
and
a
subsequent
application
6
days
later.

Wheat.
There
is
a
60­
day
harvest
interval
for
both
wheat
and
triticale.
For
spring
wheat,
which
emerges
around
the
middle
of
May
and
is
harvested
in
early
August,
this
restricts
the
application
period
to
May
and
early
June.
The
simulated
first
application
date
was
May
15
with
a
second
application
made
5
days
later.

Chemistry
Input
Parameters
The
chemistry
input
parameters
(
Table
7)
are
the
same
as
those
used
for
the
previous
drinking
water
assessment
(
D323594)
with
the
exceptions
described
below.
Most
significant
is
the
inclusion
of
additional
aerobic
soil
metabolism
data
in
the
calculation
of
the
PRZM
degradation
input
parameter.
In
the
previous
assessment,
only
a
single
value
was
available,
so
this
value
was
multiplied
by
three
to
account
for
the
uncertainty
due
to
small
sample
size
and
the
known
high
background
variability
in
aerobic
soil
metabolism
rate.
When
more
than
one
value
is
available
(
three
additional
estimates
were
submitted
by
the
technical
registrant),
the
upper
90%
confidence
bound
on
the
mean
is
used.
While
the
additional
data
did
not
change
the
best
estimate
of
aerobic
soil
metabolism
half­
life
for
total
toxic
residues
significantly,
the
upper
90%
confidence
bound
is
considerably
less
than
three
times
the
previous
estimate,
6.909
to
3.304.
The
estimate
of
foliar
dissipation
half­
life
increased
somewhat
from
2.9
to
4.3
d
based
on
additional
submitted
data,
but
this
change
is
not
as
significant
as
the
change
aerobic
soil
metabolism.

Data
quality
descriptions
for
each
parameter
in
Table
7
were
derived
as
follows.
 
Excellent 
was
used
to
describe
parameters
which
are
very
well
know
and
had
little
or
no
error
associated
with
them
(
e.
g.
molecular
weight)
or
when
there
is
an
abundance
of
high
quality
data
available.
 
Very
good 
is
used
to
describe
parameters
from
high
quality
studies
and
the
study
is
generally
reproducible
(
e.
g.
hydrolysis)
,
or
when
there
is
substantial
background
variability
(
e.
g.
aerobic
soil
metabolism)
there
are
multiple
high
quality
studies
used
to
develop
the
input
parameter.
 
Good 
is
used
where
the
data
is
expected
to
be
reproducible,
but
is
more
uncertain
than
normal,
or
if
metabolism
parameters
are
based
on
two
high
quality
studies,
or
where
there
are
multiple
studies
which
are
usable
but
not
high
quality.
 
Fair 
is
used
to
describe
metabolism
parameters
based
on
a
single
study,
or
where
the
data
set
is
significantly
flawed
but
still
provide
some
usable
information.
Poor
is
used
describe
input
parameters
based
on
surrogate
data.

Hydrolysis.
In
the
drinking
water
assessment,
hydrolysis
was
not
considered,
because
the
degradates
that
formed
by
hydrolysis
were
considered
toxic,
and
thus
there
was
no
reduction
in
the
toxic
residues
present.

Photolysis.
Photolysis
was
considered
negligible
in
the
original
drinking
water
assessment
and
was
excluded
in
that
assessment.
In
this
assessment,
it
has
been
included
(
T
1/
2
=
353
days)
but
it
is
still
negligible
and
will
have
no
significant
impact
on
the
estimated
environmental
concentrations
(
EECs).

Aerobic
soil
metabolism.
As
noted
above,
the
previous
aerobic
soil
metabolism
half­
life
input
parameter
was
6.909
days.
As
noted
above,
three
additional
measurements
were
submitted
by
registrant,
so
the
soil
metabolism
input
parameter
has
been
recalculated.
The
three
measured
half
­
lives
were
2.35
d,
2.34
d,
and
4.26
d
for
the
Riverside,
Middlefield,
and
Somersham
soils
respectively.
Before
these
values
could
be
used
to
calculate
the
input
parameter,
two
adjustments
had
to
be
made.
First,
no
degradates
were
measured
in
these
studies,
and
the
previous
estimate
included
the
environmental
degradates
included
in
the
tolerance
using
the
total
toxic
residues
method
to
estimate
the
half­
life.
In
order
to
account
for
these
degradates,
at
least
to
some
extant,
the
ratio
between
the
half­
life
for
the
degradation
of
the
parent
to
the
half­
life
including
toxic
degradates
was
used
to
adjust
the
three
measurements.
This
adjustment
factor
was
1.045.
Secondly,

these
studies
were
conducted
at
20
°
C
rather
than
the
standard
25
°
C.
The
Q
10
rule
was
used
to
adjust
the
rate
to
the
standard
temperature
using
a
factor
of
2.3
decrease
in
half­
life
for
every
10
degree
increase
in
temperature.
For
a
five
degree
increase
in
temperature,
the
half­
life
decreases
by
a
factor
of
0.86.
The
new
half­
lives,
adjusted
for
these
two
factors,
are
2.14
d,
2.13
d,
and
3.88d
.
The
upper
90%
confidence
bound
on
the
mean
of
these
three
values
plus
the
previous
measurement
of
2.303
is
3.304
d.

Aerobic
aquatic
metabolism.
As
there
is
no
measured
aerobic
aquatic
metabolism
data
,
the
aerobic
aquatic
metabolism
value
was
derived
by
doubling
the
aerobic
soil
metabolism
input
parameter
for
a
value
of
6.608
d.

Anaerobic
aquatic
metabolism.
The
input
parameter
for
degradation
in
the
sediment
was
based
on
the
anaerobic
aquatic
metabolism
value
which
calculated
based
on
total
toxic
measured
residues,
and
multiplied
by
three
to
account
for
uncertainty
associated
with
a
single
measurement
and
the
high
background
variability
associated
with
metabolism.

Foliar
Degradation.
In
the
previous
assessment,
the
foliar
degradation
rate
was
based
on
25
studies
from
the
open
literature.
The
technical
registrant
has
submitted
additional
magnitude
of
residue
studies
for
consideration
in
estimating
foliar
degradation
rates
and
those
measurements
that
were
considered
appropriate
for
estimating
foliar
degradation
(
D291565)
are
now
included
in
the
estimate.
The
resulting
rate
constant
changed
from
0.24
d
­
1
to
0.16
d
­
1
.
All
the
acceptable
values
were
on
wheat.
Other
submitted
studies
were
on
fruit
crops
and
were
not
measurements
on
foliage
or
whole
aboveground
plant
and
were
deemed
unsuitable
for
estimating
foliar
degradation
rates.

It
is
important
to
note
that
using
dissipation
data
for
degradation
has
the
potential
to
double
count
some
dissipation
processes,
in
particular
washoff
during
rainfall.
The
potential
for
this
error
increases
for
pesticides
which
are
more
persistent
on
foliage,
and
those
that
washoff
foliage
easily.
The
relatively
short
foliar
dissipation
half­
life
for
dimethoate
decreases
the
likelihood
that
rainfall
occurred
during
the
residue
trials
and
makes
it
more
likely
that
most
of
the
trials
reflect
degradation
rather
than
a
combination
of
degradation
and
washoff.
The
foliar
washoff
coefficient
used
was
the
default
value
of
0.5,
which
is
used
when
no
direct
washoff
data
are
available.

Table
7.
Chemical
input
parameters
for
total
dimethoate
residues.
Methods
for
estimating
each
parameter
and
the
quality
identifiers
are
described
in
the
text.

Parameter
Value
Justification
Quality
Molecular
weight
229.25
g
mol­
1
excellent
Solubility
32,000
mg
L­
1
measured
value
good
Henry s
Law
Constant
8.0
x
10
­
11
atm­
m­
3
mol­
1
estimated
from
solubility
and
vapor
fair
pressure
Kd
0.3
L
kg­
1
lowest
non­
sand
Kd
good
Aerobic
soil
metabolism
halflife
3.304
d
upper
90%
confidence
bound
on
four
measurement
good
Aerobic
aquatic
metabolism
half­
life
6.608
d
2
time
the
aerobic
soil
metabolism
value
poor
Anaerobic
aquatic
metabolism
half­
life
25.76
d
3
times
a
single
measured
value
fair
Hydrolysis
0
sum
of
parent
plus
toxic
degradate
does
not
show
degradation
by
this
route
good
Aqueous
photolysis
353
d
measured
value
from
study
much
shorter
than
half­
life
fair
Foliar
Degradation
Rate
0.16
d­
1
(
2.82
d)
upper
90%
CB
on
29
values
good
Foliar
Washoff
Coefficient
0.5
default
value
poor
Results
The
DWECs
for
dimethoate,
calculated
as
described
above,
are
in
Table
8.
The
raw
acute
exposure
estimates
were
multiplied
by
a
toxicity
adjustment
factor
of
12
to
account
for
conversion
to
omethoate
during
drinking
water
treatment
while
the
chronic
estimates
were
multiplied
by
a
factor
of
3.
This
is
based
on
the
assumption
that
the
conversion
to
omethoate
during
drinking
water
treatment
is
100%.
The
list
of
input
files
used
for
these
DWECs
are
listed
in
the
Appendix.

The
recommended
DWECs
for
drinking
water
exposure
assessment
are
from
broccoli.
In
the
previous
assessment,
Florida
citrus
had
the
largest
DWECs.
The
Florida
citrus
DWECs
have
been
reduced
from
1654
µ
g
 
L
­
1
to
187
µ
g
 
L
­
1
due
to
a
decrease
in
the
single
application
rate
from
2
to
1
lb
acre
­
1
,
and
a
specified
number
of
applications
of
2
and
a
specified
interval
of
30
d.
In
the
previous
assessment,
the
use
pattern
was
8
applications
of
2
lb
acre
­
1
applied
at
3
d
intervals;
the
8
applications
and
3­
d
intervals
were
values
used
in
the
absence
of
specific
directions
on
the
label.
The
new
broccoli
label
still
has
a
larger
number
of
applications,
6,
and
a
short
application
interval,
which
results
in
higher
DWECs.
It
should
be
noted
that
only
one
of
these
simulated
application
practices,
for
northwest
cherries,
simulated
in
California,
had
unrestricted
numbers
of
applications
and
an
unspecified
interval.
This
use
pattern
had
the
second
highest
DWECs.
In
general
the
DWECs
for
all
the
previously
assessed
use
patterns
have
decreased
for
this
assessment
due
to
the
more
clearly.

As
noted
above,
time
series
for
the
crops
with
the
largest
DWECS
(
broccoli)
and
the
smallest
(
pecans)
were
provided
to
HED
for
incorporation
into
more
refined
dietary
exposure
assessments.
Time
series
for
all
these
assessments
are
available
and
can
be
used
to
assess
the
aggregate
dietary
risks
associated
with
different
crops.

Table
8.
DWECs
for
new
maximum
use
patterns
recommended
by
the
technical
registrant
for
dimethoate
selected
crops.
Acute
EEC
were
adjusted
by
a
TAF
of
12
to
account
for
expected
conversion
to
omethoate
during
drinking
water
treatment.
Chronic
and
cancer
EECs
were
adjusted
by
a
TAF
of
3.
Recommended
Tier
2
EEC s
for
human
health
risk
assessment
are
for
broccoli
(
shaded
line
in
table)

Crop
PCA
Acute
EEC
Chronic
EEC
Cancer
EEC
­­­­­­­­­­­­­­­­­­­­
µ
g
L
­
1
dimethoate
equivalents
­­­­­­­­­­­­­­­­
­­­­

Alfalfa
(
MN)
0.87
141
2.95
1.81
Beans
(
MI)
0.77
68.9
0.80
0.44
Broccoli
(
CA)
0.56
380
9.74
4.81
Cherries
(
CA)
0.63
357
14.2
12.9
Citrus
(
FL)
0.38
182
1.32
0.68
Corn
(
OH)
0.44
131
1.34
0.64
Lentils
(
ND)
0.87
172
2.63
1.13
Lettuce
(
CA)
0.56
276
5.8
3.00
Pecan
(
GA)
0.38
14.1
0.13
0.08
Potatoes
(
ME)
0.87
90
1.26
0.88
Safflower
(
ND)
0.87
94
1.38
0.97
Sorghum
(
KS)
0.87
265
2.65
1.19
Soybeans
(
MS)
0.41
108
0.95
0.44
Tomatoes
(
FL)
0.38
75.1
0.75
0.36
Wheat
0.56
110
1.51
0.84
Literature
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D305220.
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D323594.
Jones,
R.
David.
2005.
A
re­
assessment
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the
drinking
water
exposure
due
to
dimethoate
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in
drinking
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new
recommended
maximum
label
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memorandum
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2005.

Jones,
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David.
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SectionNumber:
4.1
APPENDIX
INPUT
FILES
ARCHIVED
FOR
DIMETHOATE
DRINKING
WATER
EXPOSURE
ASSESSMENT
IN
SUPPORT
OF
REREGISTRATION
File
Name
Date
Description
w03822.
dvf
July
3,
2002
weather
data
for
GA
kale
scenario
(
Savannah,
GA)

w03940.
dvf
July
3,
2002
weather
data
for
MS
cotton
and
MS
soybean
scenarios
(
Jackson,
MS)

w12842.
dvf
July
3,
2002
weather
data
for
FL
cucumber
and
citrus
scenarios
(
Tampa,
FL)

w12844.
dvf
July
3,
2002
weather
data
for
Florida
tomato
&
pepper
scenarios
(
W.
Palm
Beach,
FL)

w13722.
dvf
July
3,
2002
weather
data
for
North
Carolina
sweet
potatoes
(
Raleigh,
NC)

w13996.
dvf
July
3,
2002
weather
data
for
Kansas
sorghum
scenario
(
Topeka,
KS)

w146067.
dvf
July
3,
2002
weather
data
for
Maine
potato
scenario
(
Caribou,
ME)

w14826.
dvf
July
3,
2002
weather
data
for
MI
beans
scenario
(
Flint,
MI)

w14850.
dvf
July
3,
2002
weather
data
for
MI
cherries
scenario
((
Traverse
City,
MI))

w14914.
dvf
July
3,
2002
weather
data
for
MN
alfalfa
and
ND
wheat
scenarios
(
Fargo,
ND)

w23155.
dvf
July
3,
2002
weather
data
for
CA
citrus
&
CA
fruit
scenario
(
Bakersfield,
CA)

w23273.
dvf
July
3,
2002
weather
data
for
CA
lettuce
scenario
(
Santa
Maria,
CA)

w24229.
dvf
July
3,
2002
weather
data
for
OR
apple
scenario
(
Portland,
OR)

w93805.
dvf
July
3,
2002
weather
data
for
Georgia
pecan
scenario
(
Macon,
GA)

w93815.
dvf
July
3,
2002
weather
data
for
Ohio
corn
scenario
(
Vandalia,
OH)

CAfruit0C.
txt
June
17,
2004
California
orchard
scenario
parameters,
unirrigated
(
PE4)

CAlettuceC.
txt
October
11,
2004
California
lettuce
scenario
parameters
(
PE4)

GApecanC.
txt
April
22,
2003
Georgia
pecan
scenario
parameters
(
PE4)

FlcitrusC.
txt
August
29,
2002
Florida
citrus
scenario
parameters
(
PE4)

FLtomatoC.
txt
October
12,
2002
Florida
tomato
scenario
parameters
(
PE4)

KSsorghumC.
txt
October
12,
2002
Kansas
sorghum
scenario(
PE4)

MEpotatoC.
txt
October
12,
2002
Maine
potato
scenario
parameters
(
PE4)

MIbeansC.
txt
May
10,
2004
Michigan
beans
scenario
parameters
(
PE4)

OP
MNalfalfaC.
txt
October
12,
2002
Minnesota
alfalfa
scenario
parameters
(
PE4)

MSsoybean.
txt
October
12,
2002
Mississippi
soybean
scenario
parameters
(
PE4)

NDwheatC.
txt
October
12,
2005
North
Dakota
wheat
scenario
parameters
(
PE4)

OHcornC.
txt
October
12,
2002
Ohio
corn
scenario
parameters
(
PE4)

IR298.
exv
August
29,
2002
standard
pond
environment
file
for
EXAMS
Input
Data
Files
for
specific
simulations
(.
PZR
extension)
035001
CA
broccoli
06
January
12,
2006
new
maximum
label
practice
for
broccoli
(
IR)
with
new
aerobic
soil
035001
CA
cherry
04
January
12,
2006
new
maximum
label
practice
for
CA
cherries
(
IR)
with
new
aerobic
soil
035001
CA
lettuce
06
January
12,
2006
new
maximum
label
practice
for
leaf
lettuce
(
IR)
with
new
aerobic
soil
035001
FL
citrus
06
January
12,
2006
new
maximum
label
practice
on
Florida
citrus
(
IR)
with
new
aerobic
soil
035001
FL
tomato
04
January
12,
2006
new
maximum
label
practice
for
Florida
tomatoes
(
IR)
with
new
aerobic
soil
035001
GA
pecans
04
January
17,
2006
new
maximum
label
practice
for
pecans
(
IR)
with
new
aerobic
soil
035001
KS
sorghum
04
January
12,
2006
new
maximum
label
practice
for
sorghum
(
IR)
with
new
aerobic
soil
035001
ME
potato
04
January
12,
2006
new
maximum
label
practice
for
potatoes
(
IR)
with
new
aerobic
soil
035001
MI
beans
02
January
12,
2006
new
maximum
label
practice
for
beans
(
IR)
with
new
aerobic
soil
035001
MN
alfalfa
03
January
25,
2005
maximum
label
practice
for
alfalfa
grown
for
hay
with
new
aerobic
soil
035001
MS
soybean
04
January
12,
2006
new
maximum
label
practice
for
soybeans
(
IR)
with
new
aerobic
soil
035001
ND
lentil
04
January
12,
2006
new
maximum
label
practice
for
lentils
(
IR)
with
new
aerobic
soil
035001
ND
safflower
04
January
12,
2006
new
maximum
label
practice
for
safflower
(
IR)
with
new
aerobic
soil
035001
ND
wheat
06
January
12,
2006
new
maximum
application
practice
for
wheat
(
IR)
with
new
aerobic
soil
035001
OH
corn
05
January
12,
2006
new
maximum
label
practice
for
Ohio
corn
(
IR)
with
new
aerobic
soil