­
1­
MEMORANDUM
DATE:
13
DECEMBER
2005
SUBJECT:
TERBACIL
­
AMENDMENT
To:
"
Exposure/
Risk
Assessment
for
the
Proposed
Use
of
Terbacil
on
Watermelon";
DP
313912.

PC
Code:
012701
DP
Code:
313756
FROM:
Mark
I.
Dow,
Ph.
D.,
Biologist
Registration
Action
Branch
1
(
RAB1)
Health
Effects
Division
7509C
(
HED)

THROUGH:
P.
V.
Shah,
Ph.
D.,
Branch
Senior
Scientist
RAB1/
HED
7509C
TO:
Daniel
Rosenblatt,
Chief
Minor
Use
&
Emergency
Response
Branch
Registration
Division,
7505C
INTRODUCTION
Under
Section
3
of
the
Federal
Insecticide,
Fungicide
and
Rodenticide
Act,
as
amended,
the
InterRegional
Research
Project
No.
4
(
IR
4)
and
the
E.
I.
du
Pont
de
Nemours
and
Company,
Crop
Protection,
have
requested
registration
of
the
herbicide
Terbacil
(
3­
tert­
butyl­
5­
chloro­
6­
methyluracil)
for
use
on
watermelon
to
control
broadleaf
weeds
and
grasses.
This
memorandum
serves
as
an
amendment
to
the
assessment
of
11
March
2005,
DP
313912.
Subsequent
to
the
original
assessment,
the
RAB1
toxicological
team
has
re­
evaluated
the
toxicological
database
relative
to
terbacil.
An
inhalation
toxicological
endpoint
has
been
identified
by
the
team
and
this
amendment
includes
consideration
of
the
inhalation
endpoint.

USE
PATTERN
SUMMARY
The
proposed
product
is
DuPontTM
Sinbar
®
herbicide
which
is
an
80
%
by
weight
active
ingredient
wettable
powder
(
EPA
Reg.
No.
352
­
317).
According
to
the
IR
4
submission
it
is
­
2­
to
be
applied
to
control
weeds
and
grasses
in
watermelon
production.
IR
4
says
"
Make
up
to
one
broadcast
application
at
the
rate
of
0.15
lb
active
ingredient
(
ai)/
Acre
(
A)
at
the
latest
after
planting
but
pre­
emergence."
Applications
are
to
be
uniform
in
a
minimum
of
20
to
40
gallons
of
water
per
acre.
There
is
a
70
day
preharvest
interval.
The
duPont
supplemental
label
says
terbacil
can
be
applied
at
0.1
­
0.15
lb
a.
i.
per
acre
and
that
there
is
a
maximum
of
0.15
lb
a.
i./
A/
year.

Other
registered
uses
of
terbacil
may
be
applied
aerially.
The
supplemental
label
for
watermelon
states:
"
A
maximum
of
one
preemergence
ground
application
of
SINBAR
®
may
be
applied
at
a
rate
of
0.1
­
0.15
pound
active
ingredient
per
acre.

The
Sinbar
®
label
directs
applicators
and
other
handlers
to
wear
long­
sleeved
shirt,
long
pants,
chemical
resistant
gloves
(
such
as
butyl,
natural,
neoprene
or
nitrile
rubber)
$
14
mils
and
shoes
plus
socks.
See
Table
1
for
a
summary
of
the
proposed
use
pattern.

Table
1
Summary
of
Proposed
Use
of
Terbacil
on
Watermelon
Formulation
80
%
wettable
powder;
EPA
Reg.
No.
352
­
317;
Sinbar
®
Herbicide
Crop
site
watermelon
Pest
broad
leaf
weeds
Application
Rate
0.1
­
0.15
lb
a.
i./
A
Application
Maximum
0.15
lb
a.
i./
A/
year
Application
method
ground
boom
spray
Application
number
1/
yr
PreHarvest
Interval
70
days
Restricted
Entry
Interval
12
hours
Manufacturer
E.
I.
du
Pont
de
Nemours
and
Company,
Crop
Protection
OCCUPATIONAL
PESTICIDE
HANDLER
EXPOSURE
Based
upon
the
proposed
use
pattern,
HED
believes
occupational
pesticide
handlers
(
i.
e.,
mixers,
loaders
and
applicators)
will
be
exposed
to
short­
term
(
1
­
30
days)
duration
exposures.
Treatment
blocks
(
number
of
acres)
are
relatively
small
compared
to
typical
field
crops
such
as
cotton,
corn,
soybeans
or
wheat.
Due
to
the
methods
of
application,
it
is
likely
that
handlers
will
be
private,
grower
(
non­
commercial)
handlers.
The
most
highly
exposed
handlers
are
expected
to
be
a
mixer/
loader
using
open
pour
of
wettable
powders
and
an
applicator
using
ground­
boom
equipment.
­
3­
Chemical
specific
data
were
not
available
with
which
to
assess
pesticide
handler
exposure.
Therefore
surrogate
data
from
studies
in
the
Pesticide
Handler
Exposure
Database
Version
1.1
(
August
1998)
PHED
SURROGATE
EXPOSURE
GUIDE
were
used
to
estimate
mixer/
loader
and
applicator
exposure.

It
is
HED
policy
to
assess
handler
exposure
and
risk
using
"
baseline"
Personal
Protective
Equipment
(
PPE)
which
is
comprised
of
long
sleeved
shirt,
long
pants,
and
shoes
plus
socks
and
if
necessary
to
assess
"
baseline"
plus
the
use
of
protective
gloves
or
other
PPE
as
might
be
necessary
or
appropriate.

In
some
cases,
HED
recognizes
that
the
same
individual
may
perform
all
three
tasks
i.
e.,
mix,
load
and
apply
a
pesticide
material.
The
available
exposure
data
for
combined
mixer/
loader/
applicator
scenarios
are
limited
in
comparison
to
the
monitoring
of
these
two
activities
separately.
These
exposure
scenarios
are
outlined
in
the
PHED
Surrogate
Exposure
Guide
(
August
1998).
HED
has
adopted
a
methodology
to
present
the
exposure
and
risk
estimates
separately
for
the
job
functions
in
some
scenarios
and
to
present
them
as
combined
in
other
cases.
Most
exposure
scenarios
for
hand­
held
equipment
(
such
as
hand
wands,
backpack
sprayers,
and
push­
type
granular
spreaders)
are
assessed
as
a
combined
job
function.
With
these
types
of
hand
held
operations,
all
handling
activities
are
assumed
to
be
effected
by
the
same
individual.
The
available
monitoring
data
support
this
and
HED
presents
them
in
this
way.
Conversely,
for
equipment
types
such
as
fixed­
wing
aircraft,
groundboom
tractors,
or
air­
blast
sprayers,
the
applicator
exposures
are
assessed
and
presented
separately
from
those
of
the
mixers
and
loaders.
By
separating
the
two
job
functions,
HED
determines
the
most
appropriate
levels
of
personal
protective
equipment
(
PPE)
for
each
aspect
of
the
job
without
requiring
the
applicator
to
wear
unnecessary
PPE
that
may
be
required
for
a
mixer/
loader
(
e.
g.,
chemical
resistant
gloves
may
only
be
necessary
during
the
pouring
of
a
liquid
formulation).

The
RAB1
toxicological
team
has
re­
evaluated
the
toxicological
database
relative
to
terbacil
and
has
identified
inhalation
toxicological
endpoints.
The
short­
term
duration
(
1
­
30
days)
and
intermediate­
term
duration
(
1
­
6
months)
inhalation
exposures
have
a
No
Observable
Adverse
Effect
Level
(
NOAEL)
of
2.0
mg
a.
i./
kg
bw/
day.
The
effects
seen
were
decreased
maternal
body
weights
and
were
identified
from
a
3­
generation
reproduction
study
in
the
rat.
See
the
attachment
for
a
summary
of
toxicological
endpoints
used
for
risk
assessment
purposes.
Table
2.0
contains
a
summary
of
exposures
and
risks
to
occupational
pesticide
handlers.
­
4­
Table
2
Estimated
Handler
Exposure
and
Risk
from
the
Use
of
Terbacil
on
Watermelon
Unit
Exposure1
mg
a.
i./
lb
handled
Applic.
Rate2
Units
Treated3
Per
Day
Average
Daily
Dose4
mg
a.
i./
kg
bw/
day
MOE5
Mixer/
Loader
­
Wettable
Powder
­
Open
Pour
Inhal
0.0434
HC
0.15
lb
a.
i./
A
200
A
Inhal
0.019
108
Applicator
­
Ground­
boom
­
Open
Cab
Inhal
0.00074
HC
0.15
lb
a.
i./
A
200
A
Inhal
0.00032
6,300
1.
Unit
Exposures
are
taken
from
"
PHED
SURROGATE
EXPOSURE
GUIDE",
Estimates
of
Worker
Exposure
from
The
Pesticide
Handler
Exposure
Database
Version
1.1,
August
1998.
Inhal.
=
Inhalation.
Units
=
mg
a.
i./
pound
of
active
ingredient
handled.
Data
Confidence:
LC
=
Low
Confidence,
MC
=
Medium
Confidence,
HC
=
High
Confidence.
2.
Applic.
Rate.
=
Taken
from
supplemental
label
and
IR­
4
submission..
3.
Units
Treated
are
taken
from
"
Standard
Values
for
Daily
Acres
Treated
in
Agriculture";
SOP
No.
9.1.
Science
Advisory
Council
for
Exposure;
Revised
5
July
2000;
4.
Average
Daily
Dose
=
Unit
Exposure
*
Applic.
Rate
*
Units
Treated
÷
Body
Weight
(
70
kg).
5.
MOE
=
Margin
of
Exposure
=
No
Observable
Adverse
Effect
Level
(
NOAEL)
÷
ADD.
Short­
term
inhalation
NOAEL
=
2.0
mg
a.
i./
kg
bw/
day
and
is
identified
from
a
3­
generation
rat
reproduction
study.
The
effects
seen
were
reduced
maternal
body
weights.

A
Margin
of
Exposure
(
MOE)
of
100
is
adequate
to
protect
occupational
pesticide
handlers.
Since
the
MOE's
are
>
100,
the
proposed
use
does
not
exceed
HED's
level
of
concern.

POST­
APPLICATION
EXPOSURE
TO
AGRICULTURAL
WORKERS
Typically,
it
is
possible
for
agricultural
workers
to
experience
post­
application
exposures
to
dislodgeable
pesticide
residues.
In
this
case,
there
are
no
dermal
toxicological
endpoints
identified.
HED
believes
that
post­
application
inhalation
exposures
are
negligible.
There
is
a
12
hour
restricted
entry
interval
(
REI)
for
this
product.
It
is
expected
that
there
is
no
volatility
as
the
spray
is
essentially
dry
after
12
hours.
The
product
is
a
wettable
powder
versus
and
liquid
formulation
thereby
further
reducing
the
possibility
of
significant
inhalation
exposure.
The
proposed
use
does
not
exceed
HED's
level
of
concern.
­
5­
ATTACHMENT
Exposure
Scenario
Dose
Used
in
Risk
Assessment,
UF
Special
FQPA
SF*
and
Level
of
Concern
for
Risk
Assessment
Study
and
Toxicological
Effects
Acute
Dietary
(
general
population
and
Females
13+)
An
endpoint
of
concern
attributable
to
a
single
dose
for
the
general
population
and
females
13+
was
not
identified
Chronic
Dietary
(
All
populations)
NOAEL
=
1.4
mg/
kg/
day
UF
=
100X
Chronic
RfD
=
0.014
mg/
kg/
day
FQPA
SF
=
1X
cPAD
=
0.014
mg/
kg/
day
©
RfD)/
1X
(
FQPA
SF)

=
0.014
mg/
kg/
day
Combined
Chronic
Toxicity/
Carcinogenicity­
rat;
LOAEL
=
83
mg/
kg/
day,
based
on
decreased
body
weight
and
body
weight
gain
in
females.

Short­
Term
Incidental
Oral
(
1­
30
days)
NOAEL
=
2.0
mg/
kg/
day
Residential
LOC
for
MOE
=
100
Occupational
LOC
for
MOE
=
100
3­
Gen
Repro
­
rat;
LOAEL
=
10
mg/
kg/
day,
based
on
decreased
body
weight
Intermediate­
Term
Incidental
Oral
(
1­
6
months)

Dermal
(
Any
Time
Period)
Quantification
of
dermal
risk
is
not
required.
Exposure
Scenario
Dose
Used
in
Risk
Assessment,
UF
Special
FQPA
SF*
and
Level
of
Concern
for
Risk
Assessment
Study
and
Toxicological
Effects
­
6­
Short­
Term
Inhalation
(
1
to
30
days)
NOAEL
=
2.0
mg/
kg/
day
(
inhalation
absorption
rate
=
100%
oral
equivalent)
Residential
LOC
for
MOE
=
100
Occupational
LOC
for
MOE
=
100
3­
Gen
Repro
­
rat;
LOAEL
=
10
mg/
kg/
day,
based
on
decreased
body
weight
Intermediate­
Term
Inhalation
(
1
to
6
months)

Long­
Term
Inhalation
(>
6
months)
NOAEL
=
1.4
mg/
kg/
day
(
inhalation
absorption
rate
=
100%
oral
equivalent)
Residential
LOC
for
MOE
=
100;
Occupational
LOC
for
MOE
=
100
Combined
Chronic
Toxicity/
Carcinogenicity­
rat;
LOAEL
=
83
mg/
kg/
day,
based
on
decreased
body
weight
and
body
weight
gain
in
females.

Cancer
Classification:
Not
likely
to
be
carcinogenic
to
humans;
cancer
risk
assessment
is
not
required.

cc:
M.
Dow(
RAB1)
RDI:
P.
Shah,
M.
I.
Dow:
806U:
CM2:(
703)
305­
5533:
RAB1:
7509C
