Page
1
of
4
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
January
31,
2006
MEMORANDUM
SUBJECT:
Drinking
Water
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:
324010
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)

Deborah
Smegal,
Risk
Assessor
Reregistration
Branch
Health
Effects
Division
(
7509C)

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

The
estimated
drinking
water
concentrations
of
TCMTB
parent
compound
have
been
provided
in
an
earlier
memo
(
DP
324012).
To
abide
by
the
recommendations
of
Risk
Assessment
Review
Committee
(
RARC),
EFED
provides
the
drinking
water
concentration
estimates
of
sum
of
TCMTB
and
its
degradates
in
this
drinking
water
memo.
Page
2
of
4
Label
Information
The
following
labels
have
been
provided
to
EFED
as
the
basis
for
this
drinking
water
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
FIRST
(
version
1.0;
Aug.
1,
2001)
screening
model
to
assess
estimated
concentrations
of
the
sum
of
TCMTB
and
its
degradates
in
surface
water.
The
model
and
its
description
are
available
at
the
EPA
internet
site:
Page
3
of
4
http://
www.
epa.
gov/
oppefed1/
models/
water/
.

Conclusions:
For
surface
drinking
water,
results
from
FIRST
indicate
that
the
peak
(
acute)
concentration
of
TCMTB
and
its
degradates
is
not
likely
to
exceed
0.94
:
g/
L
(
ppb),
and
that
the
average
annual
(
chronic)
concentration
is
not
likely
to
exceed
0.67
:
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.

Input
Parameter
Selection
The
RARC
has
recommended
to
include
TCMTB
and
2­
MBT
for
drinking
water
estimations.
Since
the
available
environmental
fate
information
of
TCMTB
can
not
be
used
to
scientifically
establish
the
formation
and
degradation
of
2­
MBT.
EFED
has
made
the
most
conservative
assumptions
to
estimate
the
concentrations
of
TCMTB
and
all
potential
degradates.
EFED
has
assumed
that
there
are
no
potential
degradation
and
transformation
reactions
and
no
partitioning
between
the
liquid
phase
and
the
solid
phase.
Only
input
parameters
uses
are
the
application
rate
(
0.041
lb
ai/
ac)
and
the
water
solubility
(
45
ppm).
Page
4
of
4
APPENDIX
1
FIRST
Model
Input
and
Output
Tables
FIRST
VERSION
1.0;
Aug.
1,
2001
RUN
No.
1
FOR
TCMTB
ON
Safflower
*
INPUT
VALUES
*
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
RATE
(#/
AC)
No.
APPS
&
SOIL
SOLUBIL
APPL
TYPE
%
CROPPED
INCORP
ONE(
MULT)
INTERVAL
Koc
(
PPM
)
(%
DRIFT)
AREA
(
IN)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
.041(
.041)
1
1
.0
45.0
GRANUL(
.0)
87.0
4.0
FIELD
AND
RESERVOIR
HALFLIFE
VALUES
(
DAYS)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
METABOLIC
DAYS
UNTIL
HYDROLYSIS
PHOTOLYSIS
METABOLIC
COMBINED
(
FIELD)
RAIN/
RUNOFF
(
RESERVOIR)
(
RES.­
EFF)
(
RESER.)
(
RESER.)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
.00
2
N/
A
.00­
.00
.00
.00
UNTREATED
WATER
CONC
(
NANOGRAMS/
LITER
(
PPTr))
Ver
1.0
AUG
1,
2001
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
PEAK
DAY
(
ACUTE)
ANNUAL
AVERAGE
(
CHRONIC)
CONCENTRATION
CONCENTRATION
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
935.605
670.929
