
Page
1
of
6
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
February
16,
2006
MEMORANDUM
SUBJECT:
Aquatic
Exposure
Assessment
for
the
Use
of
the
Fungicide
of
2­(
Thiocyanomethylthio)
benzothiazole
(
TCMTB)
as
a
Seed
Treatment
on
Cotton,
Wheat,
Barley,
Oats,
Rice,
Sugar
Beets,
and
Safflower
PC
Code:
035603
DP
Barcode:
324012
FROM:
James
Lin,
Environmental
Engineer
Environmental
Risk
Branch
1
Environmental
Fate
and
Effects
Division
(
7507C)

TO:
Kathryn
Jakob,
Chemical
Review
Manager
Regulatory
Management
Branch
II
Antimicrobials
Division
(
7510C)

Kathryn
Montague,
Senior
Biologist
Risk
Assessment
and
Science
Support
Branch
Antimicrobials
Division
(
7510C)

THRU:
Nader
Elkassabany,
Acting
Branch
Chief
Environmental
Risk
Branch
1
Environmental
Fate
and
Effects
Division
(
7507C)

This
aquatic
exposure
assessment
provides
the
estimated
environmental
concentrations
(
EEC)
for
the
use
of
2­(
Thiocyanomethylthio)
benzothiazole
(
TCMTB)
as
a
seed
treatment
on
cotton,
wheat,
barley,
oats,
rice,
sugar
beets,
and
safflower.
For
this
action,
EFED
considered
risk
only
from
parent
compound
of
TCMTB
and
not
any
degradates
associated
with
TCMTB.
Page
2
of
6
Label
Information
The
following
labels
have
been
provided
to
EFED
as
the
basis
for
this
aquatic
exposure
assessment.

COTGARD
®
and
ORYZETMcontain
three
active
ingredients,
Carboxin
(
14.35%),
TCMTB
(
5.00%)
and
Metalaxyl
(
2.40%).
The
targeted
uses
are
for
cottonseed
and
rice
seed.

NU­
FLOW
ND
contains
Chloroneb
(
23.5%)
and
TCMTB
(
9.0%).
The
only
use
is
for
cottonseed
treatment.

NUSAN
®
30
E.
C.
contains
TCMTB
(
30%).
The
label
seed
treatment
uses
include:
cotton,
wheat,
barley,
oats,
rice,
sugar
beets,
and
safflower.

ARGENTTM
30
contains
TCMTB
(
30%).
The
only
use
is
for
cottonseed
treatment.

The
first
two
labels
were
not
addressed,
since
TCMTB
is
a
minor
active
ingredient.
For
this
aquatic
exposure
assessment,
the
last
two
labels
will
be
based,
since
TCMTB
is
the
sole
active
ingredient.
According
to
the
two
labels,
the
application
rates
for
various
seed
treatments
are
tabulated
below.

Crop
Application
Rate
(
fl
oz/
100
lbs)
Max.
Seeding
Rate
(
lbs/
ac)
Rate
(
lbs
ai/
ac)

Cotton
5
18
0.018
Safflower
2
100
0.041
Sugar
beets
2
8
0.003
Rice
1.25
150
0.039
Wheat
1.25
150
0.039
Oats
1.25
128
0.033
Barley
1.25
100
0.026
The
maximum
seeding
rate
information
is
based
on
EFED's
T­
REX
model,
except
for
rice
use
and
wheat
use,
which
are
according
to
HED
SOPs.
The
application
rate
ranges
from
0.003
lb
ai/
ac
to
0.041
lb
ai/
ac.

Modeling
Approach
For
this
aquatic
exposure
assessment,
the
highest
rate
of
0.041
lb
ai/
ac
is
used
for
the
screening
purpose.
We
used
the
tier
1
models:
GENEEC
(
version
2.0;
Aug.
1,
2001)
and
SCI­
GROW
Page
3
of
6
(
version
2.3;
Nov.
4,
2003)
screening
models
to
assess
estimated
concentrations
of
TCMTB
in
surface
water
and
ground
water,
respectively.
These
models
and
their
descriptions
are
available
at
the
EPA
internet
site:

http://
www.
epa.
gov/
oppefed1/
models/
water/
.

Conclusions:
For
surface
water
exposures,
results
from
GENEEC
indicate
that
the
TCMTB
concentrations
of
0.28
ppb
(
ug/
L),
0.26
ppb,
0.20
ppb,
0.12
ppb,
and
0.08
ppb,
respectively,
for
peak,
4­
day
average,
21­
day
average,
60­
day
average,
and
90­
day
average
exposure.
For
ground
water,
SCI­
GROW
indicates
that
TCMTB
concentrations
are
not
likely
to
exceed
0.00014
:
g/
L.
Full
model
inputs
and
outputs
are
in
Appendix
1.

Since
our
models
are
not
specifically
designed
to
estimate
concentrations
for
pesticides
used
for
seed
treatment,
there
are
uncertainties
in
their
predictive
potential.
However,
these
uncertainties
are
not
expected
to
substantially
decrease
the
conservativeness
of
the
Tier
1
modeling
results.

Uncertainties
in
the
Modeling
Several
factors
suggests
low
environmental
exposure
from
seed
treatment,
including
(
1)
seed
treatment
pesticides
are
applied
at
low
rates;
(
2)
adjuvants
are
used
to
encourage
pesticide
binding
to
the
seed
coat;
(
3)
physicochemical
properties
of
seed
treatment
pesticides
generally
exhibit
low
mobility
to
retain
the
pesticide
near
the
seed
coat
and
root
zone;
(
4)
seeds
are
normally
incorporated,
which
is
expected
to
limit
environmental
exposure;
and
(
5)
seed
treatments
may
have
indoor
use
patterns
(
e.
g.,
seed
storage).
In
addition
to
these
factors,
the
main
uncertainty
in
our
assessment
for
the
use
of
TCMTB
as
a
seed
treatment
is
that
we
have
not
accounted
for
the
potential
for
sorption
to,
or
reaction
on,
the
seed
coat.
Because
of
model
limitations
and
because
we
have
no
data
to
the
contrary,
we
assumed
that
TCMTB
does
not
sorb
to
the
seed
coat,
but
only
to
the
soil.
In
effect,
this
assumption
provides
conservative
runoff
and
leaching
scenarios.

SCI­
GROW
was
developed
using
Koc
values
ranging
from
32
 
180
ml/
g
and
half­
lives
from
13
 
1000
days.
The
input
values
for
TCMTB
are
outside
these
ranges;
therefore,
the
extrapolation
increases
the
uncertainty
of
the
ground
water
estimated
concentrations.

Input
Parameter
Selection
Based
on
environmental
fate
data,
TCMTB
is
expected
to
be
relatively
immobile
and
persistent
in
terrestrial
environments.
Freundlich
sorption
coefficients
(
Kf),
exponent
values
(
1/
n)
for
concentration
in
water,
and
Freundlich
coefficients
normalized
for
organic
carbon
(
Koc)
are
in
Table
1
below
(
MRID
426314­
01).
The
aerobic
soil
metabolism
half­
life
for
TCMTB
was
1.4
days
(
MRID
435322­
01).
TCMTB
had
a
photodegradation
half­
life
of
1.5
hours
under
ideal
the
laboratory
exposure
conditions
(
MRID
426309­
01).
Page
4
of
6
Table
1:
Freundlich
Soil
Sorption
Coefficients
for
TCMTB*

Soil
Kf
1/
n
Koc
Sand
0.99
0.93
765
Sandy
loam
9.9
0.86
2120
Silt
loam
62.7
0.76
7896
Clay
22.1
0.85
2554
Clay
loam
3.5
0.96
282
*
Concentration
units
in
soil
are
g/
g
soil;
in
water,
g/
mL
water
For
purposes
of
this
aquatic
exposure
assessment,
the
GENEEC
and
SCI­
GROW
model
input
parameters
selected
for
TCMTB
are
shown
in
Tables
2
and
3
below
(
see
Appendix
1
for
full
model
inputs
and
outputs).

Table
2:
GENEEC
Input
Parameters
for
TCMTB
SOURCE
VALUE*

Application
rates
Label
(
Reg.
2935­
389)
0.041
lb/
acre
Aerobic
soil
metabolism
half­
life
MRID
433522­
01
4.2
days
(
3
x
1.4
days)

Koc
(
lowest
non­
sand
soil
Freundlich
sorption
coefficient
)
MRID
426314­
01
282
(
soil
mass
in
grams,
volume
of
water
in
mL)

Solubility
Product
Chemistry
45
ppm
Photodegradation
in
water
half­
life
MRID
426309­
01
0.188
days
(
3
x
1.5
hr)

Number
of
Applications
Label
(
Reg.
2935­
389)
1
Application
Type
Model
Option
Granular
(
4
inch)

Aerobic
Aquatic
Metabolism
Half­
life
MRID
425086­
01
20.7
days
(
3
x
6.9
days)

*
Values
based
on
EFED
input
parameter
selection
policy
and
processes.
Page
5
of
6
Table
3:
SCI­
GROW
Input
Parameters
for
TCMTB
SOURCE
VALUE*

Application
rate
Label
(
Reg.
2935­
389)
0.041
lb/
acre
Aerobic
soil
met.
half­
life
MRID
433522­
01
4.2
days
(
3
x
1.4
days)

Koc
(
Freundlich
organic
matter
sorption
coefficient,
lowest
value)
MRID
426314­
01
282
(
soil
mass
in
grams,
volume
of
water
in
mL)

Number
of
applications
Label
(
Reg.
2935­
389)
1
*
Values
based
on
EFED
input
parameter
selection
policy
and
processes.
Page
6
of
6
APPENDIX
1
SCI­
GROW
and
GENEEC
Model
Input
and
Output
Tables
SCI­
GROW
version
2.3,
November
4,
2003
SCIGROW
VERSION
2.3
ENVIRONMENTAL
FATE
AND
EFFECTS
DIVISION
OFFICE
OF
PESTICIDE
PROGRAMS
U.
S.
ENVIRONMENTAL
PROTECTION
AGENCY
SCREENING
MODEL
FOR
AQUATIC
PESTICIDE
EXPOSURE
SciGrow
version
2.3
chemical:
TCMTB
time
is
1/
31/
2006
13:
40:
47
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
Application
Number
of
Total
Use
Koc
Soil
Aerobic
rate
(
lb/
acre)
applications
(
lb/
acre/
yr)
(
ml/
g)
metabolism
(
days)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
0.041
1.0
0.041
2.82E+
02
4.2
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
groundwater
screening
cond
(
ppb)
=
1.38E­
04
************************************************************************

GENEEC
version
2.0,
August
1,
2001
RUN
No.
1
FOR
TCMTB
ON
Safflower
*
INPUT
VALUES
*
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
RATE
(#/
AC)
No.
APPS
&
SOIL
SOLUBIL
APPL
TYPE
NO­
SPRAY
INCORP
ONE(
MULT)
INTERVAL
Koc
(
PPM
)
(%
DRIFT)
(
FT)
(
IN)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
.041(
.041)
1
1
282.0
45.0
GRANUL(
.0)
.0
4.0
FIELD
AND
STANDARD
POND
HALFLIFE
VALUES
(
DAYS)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
METABOLIC
DAYS
UNTIL
HYDROLYSIS
PHOTOLYSIS
METABOLIC
COMBINED
(
FIELD)
RAIN/
RUNOFF
(
POND)
(
POND­
EFF)
(
POND)
(
POND)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
4.20
2
N/
A
.19­
23.31
20.70
10.96
GENERIC
EECs
(
IN
NANOGRAMS/
LITER
(
PPTr))
Version
2.0
Aug
1,
2001
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
PEAK
MAX
4
DAY
MAX
21
DAY
MAX
60
DAY
MAX
90
DAY
GEEC
AVG
GEEC
AVG
GEEC
AVG
GEEC
AVG
GEEC
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
277.81
263.46
198.64
116.11
84.13
