United
States
Prevention,
Pesticides
EPA­
738­
F­
05­
002
Environmental
Protection
And
Toxic
Substances
September
2005
Agency
(
7508C)

R.
E.
D
FACTS
Dimethipin
Pesticide
Reregistration
All
pesticides
sold
or
distributed
in
the
United
States
must
be
registered
by
EPA,
based
on
scientific
studies
showing
that
they
can
be
used
without
posing
unreasonable
risks
to
people
or
the
environment.
Because
of
advances
in
scientific
knowledge,
the
law
requires
that
pesticides
which
were
first
registered
before
November
1,
1984,
be
reregistered
to
ensure
that
they
meet
today's
more
stringent
standards.

In
evaluating
pesticides
for
reregistration,
EPA
obtains
and
reviews
a
complete
set
of
studies
from
pesticide
producers,
describing
the
human
health
and
environmental
effects
of
each
pesticide.
To
implement
provisions
of
the
Food
Quality
Protection
Act
(
FQPA)
of
1996,
EPA
considers
the
special
sensitivity
of
infants
and
children
to
pesticides,
as
well
as
aggregate
exposure
of
the
public
to
pesticide
residues
from
all
sources,
and
the
cumulative
effects
of
pesticides
and
other
compounds
with
common
mechanisms
of
toxicity.
The
Agency
develops
any
mitigation
measures
or
regulatory
controls
needed
to
effectively
reduce
each
pesticide's
risks.
EPA
then
reregisters
pesticides
that
meet
current
human
health
and
safety
standards
and
can
be
used
without
posing
unreasonable
risks
to
human
health
and
the
environment.

When
a
pesticide
is
eligible
for
reregistration,
EPA
explains
the
basis
for
its
decision
in
a
Reregistration
Eligibility
Decision
(
RED)
document.
This
fact
sheet
summarizes
the
information
in
the
RED
document
for
dimethipin
(
Chemical
Code
Number:
118901).

Use
Profile
Dimethipin
is
registered
for
use
as
a
cotton
growth
regulator
and
desiccant.
In
addition,
it
is
an
herbicide
that
is
used
post­
emergence
for
selective
control
of
weeds.
Dimethipin
is
registered
for
use
on
cotton
and
nonbearing
apple
nursery
stock.

Annual
domestic
dimethipin
usage
is
approximately
100,000
pounds.
For
dimethipin,
rates
per
application
and
rates
per
year
are
generally
less
than
0.31
lbs
ai/
A
and
0.56
lbs
ai/
A
respectively.
Dimethipin
is
used
predominantly
in
Georgia,
Mississippi,
and
Alabama.
Dimethipin
is
used
alone
and
is
also
used
as
tank
mix
with
other
plant
growth
regulating
chemicals.

Regulatory
History
Dimethipin
has
been
registered
in
the
United
States
since
1982.
Several
data
call­
ins
(
DCIs)
have
been
issued
for
dimethipin.
The
Agency
conducted
a
review
of
the
scientific
data
base
underlying
pesticide
registrations
and
identified
missing
or
inadequate
studies.
Subsequent
Data
Call­
Ins
(
DCIs)
were
issued
in
1989,
1991,
and
1995.

Human
Health
Assessment
Toxicity
In
acute
studies,
dimethipin
has
moderate
acute
toxicity
(
Toxicity
Category
II)
via
the
oral
and
inhalation
routes,
and
low
(
Toxicity
Category
III)
acute
toxicity
via
the
dermal
route
of
exposure.
Dimethipin
is
not
an
eye
or
skin
irritant,
nor
a
skin
sensitizer.

In
longer­
term
studies,
dimethipin
is
toxic
to
the
liver,
kidneys,
and
lungs.
In
rats,
the
lowest
observed
adverse
effect
levels
(
LOAELs)
are
based
on
decreased
body
weight
gains
and
body
weight.
The
no
observed
adverse
effect
levels
(
NOAELs)
are
based
on
cardiovascular
toxicity
in
the
gastrointestinal
tract
for
female
rats
and
toxicity
in
the
gastrointestinal
tract
for
male
rats.

Dimethipin
has
been
classified
as
a
Category
C
chemical,
or
possible
human
carcinogen.
However,
a
quantification
of
carcinogenic
risk
was
not
recommended,
based
on
the
weight­
of­
evidence
evaluation
of
available
data.

There
are
no
signs
of
neurotoxicity
or
developmental
toxicity
following
exposure
to
dimethipin.

Dietary
Exposure
and
Risk
The
dimethipin
dietary
risk
assessment
considered
only
chronic
risks
from
residues
in
food
based
on
field
trials
because
no
acute
endpoint
was
identified.
The
chronic
dietary
(
food)
risk
is
estimated
at
less
than
1%
of
the
Chronic
Population
Adjusted
Dose
(
cPAD)
for
all
population
subgroups,
and
is
not
of
concern.

The
Agency
estimates
potential
surface
water
and
ground
water
pesticide
contamination
using
models
and
monitoring
data.
The
maximum
surface
water
modeling
concentration
of
7.3
parts
per
billion
(
ppb),
or
micrograms
per
liter
(
ug/
l),
was
used
to
estimate
the
surface
water
EDWC.
The
ground
water
EDWC
and
chronic
drinking
water
exposure
value
is
based
on
a
ground
water
monitoring
value
of
99
ppb.
Both
the
surface
water
and
ground
water
EDWC
values
are
below
the
drinking
water
level
of
concern
(
DWLOCs)
of
762
ppb
for
chronic
exposure,
and
are
not
of
concern.

Aggregate
Risk
An
aggregate
risk
assessment
looks
at
the
combined
risk
from
dietary
exposure
(
food
and
drinking
water
pathways),
as
well
as
exposures
from
non­
occupational
sources
(
e.
g.,
residential
uses).
Dimethipin
has
no
residential
uses,
thus
the
aggregate
risk
included
food
and
water
only.
Additionally,
there
were
no
acute
endpoints
identified
therefore
only
chronic
aggregate
risk
was
calculated.
The
chronic
aggregate
risk
does
not
exceed
the
Agency's
level
of
concern.

The
DWLOC
method
was
used
to
assess
the
aggregate
risk
of
dimethipin.
A
DWLOC
is
the
portion
of
the
chronic
PAD
(
cPAD)
remaining
after
estimated
dietary
(
food
only)
exposures
have
been
subtracted
and
the
remaining
exposure
has
been
converted
to
a
concentration
(
ug/
liter
or
ppb).
This
concentration
value
(
DWLOC)
represents
the
available
or
allowable
exposure
through
drinking
water.

Chronic
(
non­
cancer)
aggregate
risk.
The
chronic
DWLOCs
range
from
218
ppb
to
762
ppb
with
the
most
sensitive
population
being
infants.
The
EDWCs,
which
range
from
7.3
to
99
ppb,
are
less
than
the
DWLOCs
which
means
that
the
risks
are
not
of
concern.
In
addition,
the
chronic
aggregate
risks
are
not
of
concern
because
they
are
estimated
at
less
than
1
percent
of
the
cPAD.

Occupational
Exposure
and
Risk
Based
on
current
use
patterns,
occupational
handlers
(
mixers,
loaders,
and
applicators)
may
be
exposed
to
dimethipin
during
normal
use.
The
Agency
identified
7
handler
scenarios
resulting
from
mixing/
loading
and
applying
dimethipin
to
crops.
For
the
occupational
use
of
dimethipin,
EPA
is
concerned
with
any
MOE
less
than
100,
which
incorporates
uncertainty
factors
of
10x
for
interspecies
variation
and
10x
for
intraspecies
variation.

The
majority
of
short
and
intermediate
term
scenarios
had
inhalation
MOEs
that
exceeded
the
target
of
100
with
baseline
PPE:
no
respirator,
long
sleeve
shirt,
pants,
shoes
and
socks.
Aerial
application
requires
a
closed
cockpit
to
achieve
the
target
MOE
of
100.
Long
term
worker
exposure
is
not
expected
for
dimethipin
and
thus
was
not
assessed.
There
are
no
post­
application
risks
to
workers
because
there
were
no
dermal
endpoints
identified.

FQPA
Considerations
The
Agency
has
concluded
that
the
FQPA
Safety
Factor
for
dimethipin
should
be
reduced
(
equivalent
to
1X)
based
on
a
complete
database
for
FQPA
consideration.
The
toxicity
database
for
dimethipin
includes
acceptable
developmental
and
reproductive
toxicity
studies.
Developmental
toxicity
studies
were
conducted
in
rats
and
rabbits
with
no
evidence
of
susceptibility.
There
is
evidence
of
decreased
body
weight
and
decreased
body
weight
gains
for
females
in
the
2­
generation
reproduction
study
in
rats.
There
were
no
body
weight
changes
for
males.

After
establishing
developmental
toxicity
endpoints
to
be
used
in
the
risk
assessment
with
traditional
uncertainty
factors
(
10x
for
interspecies
variability
and
10x
for
intraspecies
variability),
the
Agency
has
no
residual
concerns
for
the
effects
seen
in
the
developmental
toxicity
studies.
Therefore,
the
10X
FQPA
special
safety
factor
was
reduced
to
1X.

Based
on
no
evidence
of
developmental
neurotoxicity,
the
Agency
has
determined
that
a
developmental
neurotoxicity
(
DNT)
study
is
not
required
for
dimethipin.
The
developmental
and
two
generation
reproduction
studies
were
complete.
Therefore,
the
Agency
determined
that
a
database
uncertainty
factor
(
UF
DB)
is
not
needed.

Tolerance
Reassessment
The
tolerances
for
dimethipin
meet
the
FQPA
safety
standards
for
the
U.
S.
population
and
sensitive
populations,
including
infants
and
children.
There
are
seventeen
tolerances
that
were
reassessed
in
the
dimethipin
RED,
and
of
these
seventeen
11
are
proposed
for
revocation.
The
tolerances
are
for
cotton
seeds
and
hulls,
cattle,
horse,
goat,
and
sheep
meat
and
byproducts,
as
well
as
the
fat
of
horses,
goats,
sheep,
and
cattle.
EPA
found
that
there
is
a
reasonable
certainty
of
no
harm
to
the
general
population
and
any
subgroup
from
the
use
of
dimethipin.

Environmental
Assessment
Environmental
Fate
Dimethipin
is
persistent
in
most
environmental
conditions
with
biodegradation,
hydrolysis,
and
photolysis
all
occurring
slowly.
Half­
lives
for
dimethipin
range
from
a
few
weeks
to
several
months.
Dimethipin
is
not
expected
to
absorb
in
solids
and
sediments,
and
thus
has
potential
for
leaching
to
groundwater
or
run­
off
to
surface
water.
Dimethipin
does
not
bioaccumulate
in
aquatic
organisms,
and
no
major
degradates
were
identified
in
the
environmental
fate
studies.

A
complete
database
has
been
assembled
for
dimethipin.
The
dissipation
of
dimethipin
is
dependent
on
the
site­
specific
properties
of
the
soil
to
which
it
is
applied.
Data
indicate
that
dimethipin
is
practically
insoluble
in
water
and
stable
to
hydrolysis
and
photolysis
in
soil.
The
aqueous
photolysis
half­
lives
are
60,
224,
and
72
days
at
pH
levels
of
5,7,
and
9
respectively.

According
to
laboratory
mobility
studies,
dimethipin
is
highly
mobile
in
all
soils.
Dimethipin
has
been
detected
in
soil
at
depths
of
90
cm
below
the
soil
surface.

Ecological
Toxicity
Dimethipin
is
considered
to
be
practically
non­
toxic
to
birds
on
an
acute
basis
with
mortality
as
the
endpoint.
There
is
no
chronic
avian
data
thus
chronic
avian
risk
cannot
be
precluded.
Dimethipin
is
classified
as
moderately
toxic
to
small
mammals
on
an
acute
oral
basis
with
decreased
body
weight
as
the
affected
endpoint.

A
honey
bee
acute
toxicity
study
indicated
that
dimethipin
is
practically
non­
toxic
to
the
honey
bee.
There
were
no
data
available
on
terrestrial
plants;
however,
dimethipin
is
expected
to
be
toxic
to
terrestrial
plants
as
it
is
an
herbicide.

Acute
toxicity
studies
on
dimethipin
show
that
it
is
slightly
toxic
to
aquatic
invertebrates,
freshwater
fish,
and
estuarine
fish.
In
addition,
dimethipin
is
acutely
toxic
to
freshwater
plants.

Risks
to
Terrestrial
and
Aquatic
Organisms
The
Agency
conducted
a
screening­
level
ecological
risk
assessment
to
determine
the
potential
impact
of
dimethipin
use
on
non­
target
terrestrial
and
aquatic
organisms.
The
Agency
used
modeling
to
evaluate
ecological
risks
for
dimethipin.

The
majority
of
ecological
risk
quotient
(
RQ)
values
do
not
exceed
the
Agency's
level
of
concern
(
LOC),
with
the
following
exceptions:
for
acute
restricted
use,
the
RQ
exceeds
the
LOC
(
0.2)
for
a
15g
mammal
feeding
on
short
grass,
and
for
endangered
species,
the
RQs
for
15g
mammals
feeding
on
short
grass,
tall
grass,
broadleaf
plants,
and
small
insects
exceed
the
acute
endangered
risk
LOC
of
0.1.

Risk
Mitigation
There
was
no
mitigation
needed
for
dimethipin
as
there
are
no
human
health
risks
of
concern,
and
there
were
very
few
ecological
risks
of
concern.

Additional
Data
EPA
is
requiring
confirmatory
data
requirements
for
dimethipin.
For
a
complete
Required
listing
of
required
studies
with
corresponding
guideline
number,
see
Section
V
of
the
dimethipin
RED
document.

Ecological
Data
Requirements
EPA
is
requiring
data
on
seedling
germination
and
seedling
emergence
(
Tier
II)
and
a
vegetative
vigor
(
Tier
II)
study.
In
addition,
avian
reproduction
tests,
early­
life
stage
freshwater
fish,
and
fish
life
cycle
studies
must
be
submitted
to
fulfill
guideline
requirements.

Toxicity
Data
Requirements
The
EPA
is
not
requiring
registrants
to
submit
additional
toxicity
studies.
However,
there
is
clarification
needed
on
three
existing
toxicity
studies:
the
test
material
stability,
homogeneity,
and
concentration
in
the
dosing
medium.

Chemistry
Data
Requirements
The
Agency
has
identified
several
product
and
residue
chemistry
requirements.
Crop
field
trial
data,
confined
accumulation
in
rotational
crops,
and
storage
stability
data
is
required.

Product
Labeling
Changes
Required
All
dimethipin
products
must
comply
with
EPA's
current
pesticide
product
labeling
requirements
and
with
the
labeling
changes
set
forth
in
Section
V
of
the
dimethipin
RED
document.

Regulatory
Conclusion
EPA
has
determined
that
all
products
containing
dimethipin
as
the
active
ingredient
are
eligible
for
reregistration,
provided
changes
specified
in
the
dimethipin
RED
are
incorporated
into
the
label
and
additional
data
identified
in
Section
V
of
the
RED
confirm
this
conclusion.

For
More
Information
Electronic
copies
of
the
RED
and
this
fact
sheet
are
available
on
the
Internet.
See
http://
www.
epa.
gov/
pesticides/
reregistration/
status.
htm
or
http://
www.
epa.
gov/
edockets.

For
more
information
about
EPA's
pesticide
reregistration
program,
the
dimethipin
RED,
or
reregistration
of
individual
products
containing
dimethipin,
contact
the
Special
Review
and
Reregistration
Division
(
7508C),
OPP,
US
EPA,
Washington,
DC
20460,
telephone
703­
308­
8000.

For
information
about
the
health
effects
of
pesticides,
or
for
assistance
in
recognizing
and
managing
pesticide
poisoning
symptoms,
please
contact
the
National
Pesticide
Information
Center
(
NPIC).
Call
toll­
free
1­
800­
858­
7378,
from
6:
30
am
to
4:
30
pm
Pacific
Time,
or
9:
30
am
to
7:
30
pm
Eastern
Standard
Time,
seven
days
a
week.
The
NPIC
internet
address
is
http://
npic.
orst.
edu.
