HED
DOC.
NO.
014635
August
07,
2001
MEMORANDUM
SUBJECT:
DIURON
­
Report
of
the
FQPA
Safety
Factor
Committee
FROM:
Brenda
Tarplee,
Executive
Secretary
FQPA
Safety
Factor
Committee
Health
Effects
Division
(
7509C)

THROUGH:
Ed
Zager,
Chairman
FQPA
Safety
Factor
Committee
Health
Effects
Division
(
7509C)

TO:
Diana
Locke,
Risk
Assessor
Reregistration
Branch
2
Health
Effects
Division
(
7509C)

PC
Code:
035505
The
FQPA
Safety
Factor
Committee
evaluated
the
available
hazard
and
exposure
data
for
Diuron
on
June
18,
2001
and
recommended
the
FQPA
safety
factor
to
be
used
in
human
health
risk
assessments
(
as
required
by
Food
Quality
Protection
Act
of
August
3,
1996).
The
committee
concluded
that
the
FQPA
safety
factor
could
be
removed
(
1x)
in
assessing
the
risk
posed
by
this
chemical.
2
I.
HAZARD
ASSESSMENT
(
Correspondence:
Y.
Yang
to
B.
Tarplee
dated
06/
06/
01)

A.
Adequacy
of
the
Toxicology
Database
There
are
acceptable
studies
in
developmental
toxicity
study
in
rabbits
and
a
two­
generation
reproduction
study
in
rats.
A
developmental
toxicity
study
in
rats
was
classified
as
unacceptable
due
to
deficiencies
in
analytical
data
on
sample
analysis;
however,
the
HIARC
considered
the
developmental
toxicity
study
in
rats
is
adequate
for
FQPA
susceptibility
assessment
based
on
the
NOAEL
of
developmental
toxicity
was
higher
than
the
maternal
NOAEL.
The
HIARC
concluded
that
a
developmental
neurotoxicity
study
with
Diuron
is
not
required.

B.
Determination
of
Susceptibility
There
is
no
indication
of
increased
susceptibility
to
young
exposed
to
Diuron
in
the
available
studies.
In
the
developmental
toxicity
study
in
rabbits,
there
were
no
developmental
effects
at
the
highest
dose
tested.
In
the
developmental
toxicity
study
in
rabbits
and
in
the
2­
generation
rat
reproduction
study,
developmental
/
offspring
effects
were
observed
only
at
a
maternally
/
parentally
toxic
dose
levels.

II.
EXPOSURE
ASSESSMENTS
A.
Dietary
Food
Exposure
Considerations
(
Correspondence:
J.
Punzi
to
B.
Tarplee
dated
06/
12/
01)

Diuron
is
a
preplant,
pre­
or
post­
emergent
herbicide,
used
on
a
variety
of
fruits,
vegetables,
nuts,
and
field
crops.
Tolerances
are
established
for
residues
of
Diuron
in
or
on
food
commodities
at
level
ranging
from
0.1
ppm
to
7
ppm
(
40CFR
§
180.106).

The
HED
Metabolism
Assessment
Review
Committee
(
MARC)
concluded
that
for
tolerance
expression
and
risk
assessment
purposes,
the
residues
of
concern
in/
on
plants,
livestock,
and
poultry
are
diuron
and
its
metabolites
convertible
to
3,4­
dichloroaniline
(
Memorandum:
J.
Punzi
to
Y.
Donovan;
dated
July
17,
2001).

USDA
Pesticide
Data
Program
(
PDP)
monitoring
data
are
available
for
Diuron,
however,
these
data
do
not
measure
3,4
DCA.
Therefore
only
field
trial
data
will
be
used
for
dietary
risk
assessment.
Additionally,
percent
crop
treated
data
are
available
from
BEAD.

The
HED
Dietary
Exposure
Evaluation
Model
(
DEEM
 
)
will
be
used
to
assess
the
risk
from
chronic
dietary
exposure
to
residues
in
food
resulting
from
the
use
of
Diuron
(
no
acute
endpoint
3
was
identified).
This
analysis
could
be
refined
using
the
available
percent
crop
treated
data
and
anticipated
residues
calculated
from
field
trials.

The
Committee
recognizes
that
further
refinement
to
the
dietary
food
exposure
analyses
may
be
required
as
the
risk
assessment
is
developed.
Therefore,
provided
the
final
dietary
food
exposure
assessment
does
not
underestimate
the
potential
risk
for
infants
and
children,
the
safety
factor
recommendations
of
this
Committee
stand.

B.
Dietary
Drinking
Water
Exposure
Considerations
(
Correspondence:
I.
Abdel­
Saheb
to
B.
Tarplee
dated
06/
06/
01)

The
environmental
fate
database
is
adequate
to
characterize
drinking
water
exposure
for
the
parent
compound.
These
data
indicate
that
parent
Diuron
is
persistent
and
mobile.
The
only
significant
degradate
in
the
aerobic
and
anaerobic
aquatic
metabolism
studies
was
mCPDMU.
Diuron
has
the
potential
to
leach
to
ground
and
to
contaminate
surface
waters.
The
HED
MARC
concluded
that
for
risk
assessment
purposes,
the
residue
of
concern
in
drinking
water
are
parent,
DCPMU,
and
MCPDMU.
Based
on
a
structural
analogy
to
monuron,
the
MARC
recommended
that
a
separate
cancer
assessment
be
conducted
for
MCPDMU
(
Memorandum:
J.
Punzi
to
Y.
Donovan;
dated
July
17,
2001).

EFED
has
limited
monitoring
data
on
the
concentrations
of
Diuron
in
surface
water.
A
study
on
the
occurrence
of
cotton
herbicides
and
insecticides
in
Playa
lakes
of
the
high
plains
of
western
Texas
concluded
that
Diuron
was
the
major
pesticide
detected
in
water
samples
collected
from
32
lakes
(
USGS,
1992).
According
to
EFED,
even
though
the
use
of
Diuron
on
cotton
in
this
part
of
the
state
is
an
example
of
actual
use
area,
the
frequency
of
sampling
and
the
length
of
sampling
period
were
not
enough
to
represent
a
good
monitoring
data
to
be
used
for
a
regulatory
purposes.

EFED
also
has
limited
monitoring
data
on
the
concentrations
of
Diuron
in
groundwater.
The
USEPA
Pesticides
In
Groundwater
Database
(
1992)
shows
validated
monitoring
data
for
Diuron
that
are
available
for
the
states
of
California,
Florida,
Georgia,
and
Texas.

Screening
models
were
used
to
determine
estimated
concentrations
of
Diuron
in
groundwater
and
surface
water:

The
FQPA
Index
Reservoir
Screening
Tool
(
FIRST)
model
was
used
to
estimate
surface
water
concentrations
of
Diuron
from
the
use
on
citrus.

The
SCI­
GROW
screening
model
was
used
to
estimate
groundwater
concentrations
of
Diuron.
The
groundwater
concentrations
estimated
from
the
modeling
agree
with
limited
existing
groundwater
monitoring
data
for
these
compounds.
4
The
Committee
recognizes
that
further
refinement
to
the
dietary
drinking
water
exposure
analyses
may
be
required
as
the
risk
assessment
is
developed.
Therefore,
provided
the
final
dietary
drinking
water
exposure
assessment
includes
all
environmental
degradates
of
toxicological
concern
and
does
not
underestimate
the
potential
risk
for
infants
and
children,
the
safety
factor
recommendations
of
this
Committee
stand.

C.
Residential
Exposure
Considerations
(
Correspondence:
R.
Sandvig
to
B.
Tarplee
dated
06/
07/
01)

Children
could
potentially
be
exposed
to
Diuron
since
it
is
used
for
weed
control
on
and
around
gravel
driveways,
patios,
and
wood
decks.
It
is
also
used
in
residential
ornamental
ponds.

There
are
no
chemical
specific
exposure
data
for
Diuron.
The
Pesticide
Handler's
Exposure
Database
(
PHED)
will
be
used
along
with
the
Outdoor
Residential
Exposure
Task
Force
(
ORETF)
database
and
the
Residential
SOPs
in
assessing
residential
risks
resulting
from
the
use
of
Diuron.

III.
SAFETY
FACTOR
RECOMMENDATION
AND
RATIONALE
A.
Recommendation
of
the
Factor
The
Committee
recommended
that
the
FQPA
safety
factor
be
removed
(
1x).

B.
Rationale
for
Removing
the
FQPA
Safety
Factor
The
Committee
concluded
that
the
safety
factor
could
be
removed
for
Diuron
because:

1.
There
is
no
indication
of
quantitative
or
qualitative
increased
susceptibility
of
rats
or
rabbits
to
in
utero
or
postnatal
exposure;
2.
A
developmental
neurotoxicity
study
(
DNT)
with
Diuron
is
not
required;
and
3.
The
dietary
(
food
and
drinking
water)
and
non­
dietary
(
residential)
exposure
assessments
will
not
underestimate
the
potential
exposures
for
infants
and
children.
