OVERVIEW
OF
LINURON
RISK
ASSESSMENT
Introduction
This
document
summarizes
EPA's
human
health
findings
and
conclusions
for
the
herbicide
linuron,
as
presented
fully
in
the
documents:
HED
Chapter
for
the
Linuron
Tolerance
Reassessment
Eligibility
Decision,
dated
April
16,
2002,
and
Drinking
Water
Assessment
for
Linuron
on
Carrots
in
California,
dated
October
14,
2001,
Drinking
Water
Assessment
for
Linuron
Metabolites
on
Carrots
in
California,
dated
January
14,
2002,
and
Occupational
Exposure
and
Risk
Assessment/
Characterization
for
the
Proposed
Use
of
Linuron
on
Rhubarb
and
Celeriac,
dated
March
27,
2002.
The
purpose
of
this
summary
is
to
assist
the
reader
by
identifying
the
key
features
and
findings
of
this
risk
reassessment
in
order
to
better
understand
the
conclusions
reached
in
the
tolerance
reassessment.
This
summary
was
developed
in
response
to
comments
and
requests
from
the
public,
which
indicated
that
the
risk
assessments
were
difficult
to
understand,
that
they
were
too
lengthy,
and
that
it
was
not
easy
to
compare
the
assessments
for
different
chemicals
due
to
the
use
of
different
formats.

The
Federal
Food,
Drug,
and
Cosmetic
Act
(FFDCA),
as
amended
by
the
Food
Quality
Protection
Act
(FQPA)
of
1996,
requires
EPA
to
review
all
the
tolerances
for
registered
chemicals
in
effect
on
or
before
the
date
of
the
enactment
of
FQPA.
In
reviewing
these
tolerances,
the
Agency
must
consider,
among
other
things,
aggregate
risks
from
non­
occupational
sources
of
pesticide
exposure,
whether
there
is
increased
susceptibility
to
infants
and
children,
and
the
cumulative
effects
of
pesticides
with
a
common
mechanism
of
toxicity.
The
tolerances
are
considered
reassessed
once
the
safety
finding
has
been
made
or
a
revocation
occurs.
A
Reregistration
Eligibility
Decision
(RED)
for
linuron
was
completed
in
March
1995,
prior
to
FQPA
enactment;
therefore,
it
needed
to
be
updated
to
consider
the
provisions
of
the
Act.

FQPA
stipulates
that
when
determining
the
safety
of
a
pesticide
chemical,
EPA
shall
base
its
assessment
of
the
risk
posed
by
the
chemical
on,
among
other
things,
available
information
concerning
the
cumulative
effects
to
human
health
that
may
result
from
dietary,
residential,
or
other
nonoccupational
exposure
to
other
substances
that
have
a
common
mechanism
of
toxicity.
The
reason
for
consideration
of
other
substances
is
due
to
the
possibility
that
low­
level
exposures
to
multiple
chemical
substances
that
cause
a
common
toxic
effect
by
a
common
mechanism
could
lead
to
the
same
adverse
health
effect
as
would
a
higher
level
of
exposure
to
any
of
the
substances
individually.
A
person
exposed
to
a
pesticide
at
a
level
that
is
considered
safe
may
in
fact
experience
harm
if
that
person
is
also
exposed
to
other
substances
that
cause
a
common
toxic
effect
by
a
mechanism
common
with
that
of
the
subject
pesticide,
even
if
the
individual
exposure
levels
to
the
other
substances
are
also
considered
safe.

EPA
did
not
perform
a
cumulative
risk
assessment
as
part
of
the
Tolerance
Reassessment
Decision
(TRED)
for
linuron
because
the
Agency
has
not
yet
initiated
a
comprehensive
review
to
2
determine
if
there
are
any
other
chemical
substances
that
have
a
mechanism
of
toxicity
common
with
that
of
linuron.
For
purposes
of
this
risk
assessment,
EPA
has
assumed
that
linuron
does
not
have
a
common
mechanism
of
toxicity
with
other
substances.

Available
data
indicates
that
3,4­
DCA
is
a
metabolite
of
linuron,
diuron,
and
propanil.
EPA
is
not
aggregating
residues
of
3,4­
DCA
for
the
linuron,
diuron,
and
propanil
risk
assessments
because
neither
linuron
nor
diuron
metabolize
to
3,4–
DCA
in
appreciable
amounts
(less
than
1%
of
the
parent
compound)
in
animal,
plant
and
environmental
(soil)
metabolism
studies.
While
3,4­
DCA
is
a
significant
residue
of
concern
for
propanil,
it
is
not
a
residue
of
concern
for
linuron
or
diuron.

In
the
future,
the
registrant
may
be
asked
to
submit,
upon
EPA's
request
and
according
to
a
schedule
determined
by
the
Agency,
such
information
as
the
Agency
directs
to
be
submitted
in
order
to
evaluate
issues
related
to
whether
linuron
shares
a
common
mechanism
of
toxicity
with
any
other
substance
and,
if
so,
whether
any
tolerances
for
linuron
need
to
be
modified
or
revoked.
The
Agency
has
developed
a
framework
for
conducting
cumulative
risk
assessments
on
substances
that
have
a
common
mechanism
of
toxicity.
This
guidance
was
issued
on
January
16,
2002
(67
FR
2210­
2214)
and
is
available
from
the
OPP
Website
at:
http://
www.
epa.
gov/
pesticides/
trac/
science/
cumulative_
guidance.
pdf.

The
risk
assessment,
and
documents
pertaining
to
the
Agency's
report
on
FQPA
tolerance
reassessment
progress
and
risk
management
decision
for
linuron
are
available
on
the
Internet
at
http://
www.
epa.
gov/
pesticides/
reregistration/
status.
htm
and
in
the
public
docket
for
viewing.
The
Agency's
report
on
FQPA
tolerance
reassessment
progress
and
risk
management
decision
for
linuron
will
be
announced
in
the
Federal
Register.

Use
Profile
Herbicide:
Linuron
is
a
substituted
urea,
selective
herbicide.
It
is
a
systemic,
photosynthesis
inhibitor
and
controls
a
variety
of
weed
species
including
annual
morning
glory,
rye
grass,
and
barnyard
grass.
Linuron
is
registered
for
use
on
asparagus,
carrots,
celery,
field
and
sweet
corn,
cotton,
parsnips,
parsley,
potatoes,
sorghum,
soybeans,
and
wheat.
In
addition,
three
new
tolerances
are
proposed
for
use
on
cotton
gin
by­
products
(9.0
ppm),
celeriac
(1.0
ppm),
and
rhubarb
(0.5
ppm).
There
are
no
registered
residential
uses
of
linuron
products.

Formulations:
Formulated
as
a
wettable
powder,
dry
flowable,
flowable
concentrate,
water
dispersible
granules,
(40­
50%
active
ingredient
for
all
formulations).

Rates,
Methods
and
Timing
of
Application:
Linuron
may
be
applied
pre­
plant,
pre­
emergence,
post­
emergence
or
post­
transplant
at
application
rates
from
0.5­
4.0
lbs/
ai/
acre/
year
and
1­
2
applications
are
allowed
per
year.
Linuron
is
mainly
used
in
the
early
season
and
has
fairly
long
preharvest
intervals
(PHIs)
(14­
30
days),
but
a
few
crops
have
short
PHIs,
notably
asparagus
(1
day)
and
carrots
(14
days).
Linuron
can
be
applied
using
ground
equipment
including
band
sprayer,
boom
sprayer,
sprinkler
irrigation,
and
tractor
mounted
sprayer.
3
Use
Summary:
On
average,
there
are
approximately
four
hundred
thousand
pounds
of
linuron
active
ingredient
used
in
the
U.
S.
annually.

Registrant:
Griffin,
LLC
Table
1.
Major
Use
Sites
For
Linuron
Crop
Site
Acres
Grown
(000)
Acres
Treated
(000)
%
of
Crop
Treated
LB
AI
Applied
(000)
States
of
Most
Usage
(%
of
total
lbs
ai
used
on
this
crop
in
these
states)
Avg
Max
Avg
Max
Avg
Max
Asparagus
90
18
30
20%
33%
18
36
CA
WA
(85%)

Carrots
104
79
104
75%
100%
145
210
CA
MI
FL
WA
TX
(83%)

Celery
34
8
11
23%
32%
4
8
MI
CA
TX
(84%)

Cotton
12,967
88
233
1%
2%
72
123
MS
AR
SC
NC
LA
TN
(83%)

Potatoes
1,433
100
158
7%
11%
85
180
ND
MI
RI
ME
NY
MN
(71%)

Total
For
All
Sites
383
577
421
788
COLUMN
HEADINGS
Avg
=
Weighted
average­
the
most
recent
years
and
more
reliable
data
are
weighted
more
heavily.
Max
=
Estimated
maximum,
which
is
estimated
from
available
data.

Human
Health
Risk
Assessment
Acute
Dietary
(Food)
Risk
(For
a
complete
discussion,
see
section
4.2.2
of
the
Human
Health
Risk
Assessment)

Because
no
effects
attributed
to
a
single
exposure
were
identified
for
the
general
population,
the
4
acute
dietary
exposure
and
risk
assessment
includes
females
13­
50
only.
Acute
dietary
risk
from
food
is
calculated
considering
what
is
eaten
in
one
day
(in
this
instance,
the
full
range
of
consumption
values
as
well
as
the
range
of
residue
values
in
food).
A
risk
estimate
that
is
less
than
100%
of
the
acute
Population
Adjusted
Dose
(aPAD)
(the
dose
at
which
an
individual
could
be
exposed
on
any
given
day
and
no
adverse
health
effects
would
be
expected)
does
not
exceed
the
Agency's
level
of
concern.
The
aPAD
is
the
reference
dose
(RfD)
adjusted
for
the
FQPA
Safety
Factor.
Table
2
presents
the
results
of
the
acute
dietary
(food)
exposure
and
risk
analysis
for
females
(13­
50
years
of
age).

Table
2.
Acute
Dietary
(Food)
Exposure
and
Risk
(99.9th
Percentile
of
Exposure)

Population
Subgroup
Exposure
(mg/
kg/
day)
%
aPAD
Females
(13­
50
years)
0.003839
9.5
°
The
acute
dietary
risk
estimate
does
not
exceed
the
aPAD
at
the
99.9th
percentile
estimated
exposure
level.
The
acute
dietary
risk
estimate
for
females
13­
50
years
old
is
<10%
of
the
aPAD.

°
For
the
females
(13­
50
years)
population
subgroup,
the
acute
No
Observed
Adverse
Effects
Level
(NOAEL)
of
12
mg/
kg/
day
was
established,
based
on
increased
post­
implantation
loss
and
fetal/
litter
resorptions
in
a
prenatal
oral
developmental
study
in
the
rat.
The
LOAEL
was
50
mg/
kg/
day.

°
A
traditional
uncertainty
factor
(UF)
of
100
was
applied
to
the
doses
selected
for
the
risk
assessment
to
account
for
interspecies
extrapolation
(10x)
and
intraspecies
variability
(10x).

°
For
acute
dietary
exposure,
the
FQPA
safety
factor
was
reduced
to
3X
since:
there
was
no
susceptibility
identified
following
in
utero
exposure;
toxicology
database
is
complete
for
FQPA
assessment;
the
dietary
exposure
assessment
will
not
underestimate
the
potential
exposures
for
infants,
children,
and/
or
women
of
childbearing
age;
and
there
are
no
residential
exposures.
The
safety
factor
should
be
retained
since
the
developmental
neurotoxicity
study
in
rats
is
required
and
may
further
define
the
potential
neuro­
endocrine
effects
observed
in
the
3­
generation
reproduction
rat
study,
the
cross
mating
in
rats
study,
and
the
leydig
cell
tumorigenesis
in
rats
study.

°
The
acute
RfD
for
females
13­
50:
12
mg/
kg/
day
(NOAEL)
÷
100
(UF)
=
0.12
mg/
kg/
day.
The
acute
PAD
for
females
13­
50:
0.12
mg/
kg/
day
÷
3
(FQPA)
=
0.04
mg/
kg/
day.

°
The
acute
dietary
exposure
analysis
is
based
on
the
Dietary
Exposure
Evaluation
Model
(DEEM
™
).
The
DEEM
™
analysis
evaluated
the
individual
food
consumption
as
reported
by
respondents
in
the
USDA
1989­
92
Continuing
Surveys
for
Food
Intake
by
Individuals
(CSFII).
The
data
are
based
on
the
reported
consumption
of
more
than
10,000
individuals
over
three
5
days.
For
the
acute
exposure
assessment,
individual
one­
day
food
consumption
data
are
used
on
an
individual­
by­
individual
basis.

°
The
acute
dietary
(food)
exposure
assessment
for
linuron
is
a
tier
III
probabilistic
(Monte
Carlo)
analysis.
Anticipated
residues
(ARs)
were
computed
from
field
trial
data
and
subsequently
utilized
to
estimate
the
acute
dietary
exposure
to
linuron
in
the
diets
of
females
13­
50.
Percent
crop
treated
(%
CT)
data,
residue
reduction
data
from
washing,
cooking
and
various
processing
studies
were
used
to
refine
the
residue
data.

Chronic
Dietary
(Food)
Risk
(For
a
complete
discussion,
see
section
4.2.3
of
the
Human
Health
Risk
Assessment)

Chronic
dietary
risk
from
food
is
calculated
by
using
the
average
consumption
values
for
food
and
average
residue
values
for
those
foods
over
a
70­
year
lifetime.
A
risk
estimate
that
is
less
than
100%
of
the
chronic
PAD
(cPAD)
(the
dose
at
which
an
individual
could
be
exposed
over
the
course
of
a
lifetime
and
no
adverse
health
effects
would
be
expected)
does
not
exceed
the
Agency's
level
of
concern.
Table
3
presents
the
results
of
the
chronic
dietary
(food)
exposure
and
risk
analysis.

Table
3.
Chronic
Dietary
(Food)
Exposure
and
Risk
Population
Subgroup
Exposure
(mg/
kg/
day)
%
cPAD
General
U.
S.
0.000114
14.8
Females
(13­
50
years)
0.000083
10.8
All
infants
(<
1
year)
0.000179
22.3
Children
(1­
6
years)
0.000268
34.7
Children
(7­
12
years)
0.000173
22.4
°
The
chronic
dietary
risk
estimate
for
all
population
subgroups
does
not
exceed
the
cPAD,
all
population
subgroups
are
<
35%
of
the
cPAD.

°
For
the
general
population,
the
NOAEL
of
0.77
mg/
kg/
day
was
established,
based
on
increased
met­
and
sulfhemoglobin
levels
in
a
chronic
feeding
study
in
dogs.
The
LOAEL
was
4.17
mg/
kg/
day
in
males
and
3.5
mg/
kg/
day
in
females.

°
An
uncertainty
factor
(UF)
of
100
was
applied
to
the
doses
selected
for
the
risk
assessment
to
account
for
interspecies
extrapolation
(10x)
and
intraspecies
variability
(10x).
6
°
For
chronic
dietary
exposure,
the
FQPA
safety
factor
was
retained
at
10X
since:
a
qualitative
increase
in
susceptibility
was
seen
in
the
F1
males
in
the
rat
reproductive
toxicity
study
(a
longterm
study);
there
is
evidence
for
testicular
lesions
and
decreased
fertility
in
this
study;
and,
a
developmental
neurotoxicity
study
in
rats
is
required
and
may
further
define
the
potential
neuroendocrine
effects
observed
in
the
3­
generation
reproduction
rat
study,
the
cross
mating
in
rats
study,
and
the
leydig
cell
tumorigenesis
in
rats
study.
(For
a
complete
discussion,
see
LINURON­
Report
of
the
Hazard
Identification
Assessment
Review
Committee).

°
The
chronic
RfD:
0.77
mg/
kg/
day
(NOAEL)
÷
100
(UF)
=
0.0077
mg/
kg/
day.
The
chronic
PAD:
0.007
mg/
kg/
day
÷
10
(FQPA)
=
0.00077
mg/
kg/
day.

°
The
chronic
dietary
exposure
analysis
is
based
on
the
Dietary
Exposure
Evaluation
Model
(DEEM
™
).
For
chronic
dietary
(food)
assessments,
a
three­
day
average
of
consumption
for
each
population
subgroup
is
combined
with
average
residues
in
commodities
to
determine
average
exposures
in
mg/
kg/
day.

°
The
chronic
dietary
(food)
exposure
assessment
for
linuron
is
a
refined
tier
III
analysis.
Anticipated
residues
(ARs)
were
computed
from
field
trial
data
and
subsequently
utilized
to
estimate
the
chronic
dietary
exposure
to
linuron
in
the
diets
of
the
general
U.
S.
population.
Percent
crop
treated
(%
CT)
data,
residue
reduction
data
from
washing,
cooking
and
various
processing
studies
were
used
as
refinements
to
the
residue
data.

Drinking
Water
Dietary
Risk
(For
a
complete
discussion,
see
section
4.3
of
the
Human
Health
Risk
Assessment)

Drinking
water
exposure
to
pesticides
can
occur
through
surface
and/
or
ground
water
contamination.
EPA
considers
acute
(one
day)
and
chronic
(lifetime)
drinking
water
risks
and
uses
either
modeling
or
actual
monitoring
data,
if
available,
to
estimate
those
risks.
Modeling
is
carried
out
in
tiers
of
increasing
refinement,
but
is
designed
to
provide
a
conservative
estimate
of
potential
exposure.
To
determine
the
maximum
allowable
contribution
from
water
allowed
in
the
diet,
EPA
first
looks
at
how
much
of
the
overall
allowable
risk
is
contributed
by
food
and
then
determines
a
Drinking
Water
Level
of
Comparison"
(DWLOC)
to
ascertain
whether
modeled
or
monitored
Estimated
Environmental
Concentrations
(EECs)
exceed
this
level.

The
linuron
drinking
water
exposure
assessment
is
based
upon
review
of
environmental
fate
studies
for
linuron
and
includes
both
modeling
and
monitoring
results
for
parent
linuron,
and
modeling
results
for
the
degradates
of
linuron.
Parent
linuron
appears
to
be
moderately
persistent
and
relatively
immobile
in
the
environment.
The
environmental
fate
assessment
for
linuron
is
incomplete
because
information
on
the
persistence,
mobility
and
dissipation
pathways
of
several
degradates
of
linuron
is
not
available.
However,
none
of
the
linuron
water
degradates
are
present
at
levels
greater
than
10%
of
the
7
applied
parent,
and
therefore
are
not
considered
major
water
metabolites.

°
The
use
of
linuron
on
carrots
was
modeled
for
the
purpose
of
assessing
surface
drinking
water
exposure
to
the
chemical
and
its
degradates.
This
use
represents
the
greatest
potential
drinking
water
exposure
because
an
estimated
75%
of
carrots
are
treated
with
linuron.

°
Estimated
Environmental
Concentrations
(EECs)
for
surface
water
were
estimated
using
PRZM/
EXAMS
(Tier
II)
modeling
and
the
Index
Reservoir
and
Percent
Crop
Area
adjustment
(IR­
PCA).
The
surface
water
monitoring
data
were
insufficient
to
complete
a
drinking
water
exposure
analysis
so
modeling
was
used
to
complete
the
analysis.

°
EECs
for
ground
water
are
based
on
monitoring
data
from
the
1992
USEPA
Pesticide
in
Groundwater
Database
for
linuron
sampled
in
Georgia,
Missouri,
Virginia,
and
Wisconsin.
The
groundwater
EECs
were
then
compared
to
the
SCI­
GROW
(Tier
I)
computer
model
for
linuron
and
its
degradates.
Drinking
water
DWLOCs
and
EECs
are
compared
in
Table
4.

Table
4.
Drinking
Water
DWLOC
and
Acute
&
Chronic
EEC
Comparisons
Population
Subgroup
Acute
Scenario
Chronic
Scenario
Acute
DWLOC
Ground
Water
EEC
Surface
Water
EEC
Chronic
DWLOC
Ground
Water
EEC
Surface
Water
EEC
U.
S.
General
23
5
18
Females
(13­
50
years)
1085
5
38
23
5
18
All
infants
6
5
18
Children
(1­
6
years)
6
5
18
°
For
acute
drinking
water
risk,
potential
(peak)
EECs
of
linuron
in
either
ground
water
(5
ppb)
or
surface
water
(38
ppb)
are
below
the
acute
DWLOC
for
females
(13­
50
years)
(1085
ppb).

°
For
chronic
drinking
water
risk
from
ground
water,
the
potential
(average)
EEC
of
linuron
(5
ppb)
is
below
the
chronic
DWLOC
(6
ppb)
for
infants
and
children,
the
most
sensitive
population
subgroups.

°
For
chronic
drinking
water
risk
from
surface
water,
the
potential
(average)
EEC
of
linuron
(18
ppb)
slightly
exceeds
the
chronic
DWLOC
(6
ppb)
for
infants
and
children,
the
most
sensitive
population
subgroups.
The
chronic
EEC
was
estimated
using
modeling
and
exceeds
the
DWLOC.
The
EEC
estimate
is
based
on
upper­
end
input
parameters
such
as
an
assumption
8
that
87%
of
a
watershed
would
be
treated
with
linuron.
EECs
predicted
from
this
model
are
likely
higher
than
would
be
found
in
drinking
water
from
surface
reservoirs
because
it
is
unlikely
that
87%
of
a
watershed
would
be
treated
with
linuron.
Nonetheless,
additional
data
are
being
required
that
will
further
refine
the
chronic
drinking
water
risk
assessment.
A
leaching/
adsorption/
desorption
study
will
provide
data
on
the
mobility
of
linuron
and
a
terrestrial
field
dissipation
study
will
provide
information
on
what
happens
to
linuron
under
field
conditions.

Residential
Risk
Linuron
is
not
registered
for
home
use
nor
is
it
used
in
and
around
schools,
or
parks.
Thus,
there
is
no
residential
exposure
to
assess
nor
aggregate
with
the
dietary
exposure.

Aggregate
Risk
(For
a
complete
discussion,
see
section
5.0
of
the
Human
Health
Risk
Assessment)

Aggregate
risk
examines
the
combined
risk
from
exposure
through
food,
drinking
water,
and
residential
uses.
Using
the
DWLOC
approach,
all
risks
from
these
exposures
must
be
less
than
100%
of
the
aPAD
or
cPAD.
For
linuron,
the
aggregate
risks
are
limited
to
food
and
water
exposure,
because
there
are
no
residential
uses.

°
Combining
both
the
acute
dietary
(food)
risk
estimates
with
the
surface
and
ground
water
EECs
(drinking
water)
for
linuron,
the
acute
aggregate
(food
+
drinking
water)
risk
is
less
than
100%
of
the
aPAD;
and
therefore,
is
not
of
concern
to
the
Agency.

°
Combining
both
the
chronic
dietary
(food)
risk
estimate
with
the
ground
water
EEC
(drinking
water)
for
linuron,
the
chronic
aggregate
(food
+
drinking
water)
risk
is
less
than
100%
of
the
cPAD,
and
therefore,
is
not
of
concern
to
the
Agency.
However,
combining
the
chronic
dietary
(food)
risk
estimate
with
the
surface
water
EEC
(drinking
water)
for
linuron,
the
chronic
aggregate
(food
+
drinking
water)
risk
is
slightly
more
than
100%
of
the
cPAD.
The
chronic
EEC
was
estimated
using
modeling
and
exceeds
the
DWLOC.
The
EEC
estimate
is
based
on
upper­
end
input
parameters
such
as
an
assumption
that
87%
of
a
watershed
would
be
treated
with
linuron.
EECs
predicted
from
this
model
are
likely
higher
than
would
be
found
in
drinking
water
from
surface
reservoirs
because
it
is
unlikely
that
87%
of
a
watershed
would
be
treated
with
linuron.
Nonetheless,
additional
data
are
being
required
that
will
further
refine
the
chronic
drinking
water
risk
assessment.
A
leaching/
adsorption/
desorption
study
will
provide
data
on
the
mobility
of
linuron
and
a
terrestrial
field
dissipation
study
will
provide
information
on
what
happens
to
linuron
under
field
conditions.
9
Occupational
and
Ecological
Risk
(For
a
complete
discussion,
see
section
4.2
of
the
Human
Health
Risk
Assessment)

Because
linuron
is
under
review
for
tolerance
reassessment
only,
no
occupational
or
ecological
risk
assessment
would
normally
be
conducted.
Occupational
and
ecological
risk
management
decisions
were
made
as
part
of
the
1995
Linuron
RED
and
have
been
implemented.
However,
two
new
minor
uses
were
established
for
linuron
as
part
of
the
tolerance
reassessment
process
for
use
on
celeraic
and
rhubarb.
An
occupational
risk
assessment
was
performed
for
these
two
new
uses
and
they
do
not
present
risks
of
concern
for
the
Agency.

Tolerance
Reassessment
Summary
(For
a
complete
discussion,
see
Linuron
Tolerance
Reassessment
Eligibility
Decision
Residue
Chemistry
Considerations,
dated
11/
26/
2001.)

The
Agency
has
reassessed
all
40
tolerances
for
linuron
and
can
make
a
FQPA
safety
determination.
In
addition,
three
new
tolerances
are
proposed
for
use
on
cotton
gin
by­
products
(9.0
ppm),
celeriac
(1.0
ppm),
and
rhubarb
(0.5
ppm).
The
Agency
has
sufficient
residue
data
for
reassessing
the
tolerances
for
linuron
and
is
requiring
additional
confirmatory
data
for
celery,
corn,
sorghum,
and
wheat.
For
commodities
that
require
additional
residue
data,
the
Current
Tolerance
value
was
used
in
the
acute
and
chronic
dietary
risk
assessments
and
this
is
the
value
that
will
continue
to
be
used
for
enforcement
purposes.
Anticipated
residues
for
all
commodities
were
calculated
from
field
trial
data
and
subsequently
utilized
to
estimate
the
dietary
exposure
to
linuron.
Acute
and
chronic
dietary
risks
from
exposure
do
not
exceed
the
Agency's
level
of
concern.
Final
tolerances
are
being
proposed
as
part
of
this
Tolerance
Reassessment
Decision
(TRED).
Additional
tolerances
may
be
revised
once
the
confirmatory
field
trial
data
has
been
submitted
to
and
reviewed
by
the
Agency.

Table
5.
Tolerance
Reassessment
Summary
for
Linuron.

Commodity
Current
Tolerance
(ppm)
1
Reassessed
Tolerance
Level
(ppm)
Comment/
Correct
Commodity
Definition
Tolerances
listed
under
40
CFR
§180.184(
a):

Asparagus
7.0
7.0
Carrots
1.0
1.0
[Carrot]

Cattle,
fat
1.0
0.2
Cattle,
mbyp
1.0
0.1
[Cattle,
meat
byproducts,
except
kidney
and
liver]
Commodity
Current
Tolerance
(ppm)
1
Reassessed
Tolerance
Level
(ppm)
Comment/
Correct
Commodity
Definition
10
Cattle,
meat
1.0
0.1
Celery
0.5
0.5
/
(TBD
4)
The
available
data
support
use
east
of
the
Rocky
Mountains;
additional
data
are
required
to
support
use
on
celery
west
of
the
Rocky
Mountains.

Corn,
field,
fodder
1.0
6.0
[Corn,
field,
stover]

Corn,
field,
forage
1.0
1.0
Corn,
fresh
(inc.
sweet
K+
CWHR)
0.25
0.25
/
(TBD
4)
Additional
crop
field
trial
data
are
required.
[Corn,
sweet
(K+
CWHR)]

Corn,
grain
(inc.
popcorn)
0.25
0.1
Popcorn
grain
tolerance
should
be
deleted
since
there
are
no
registered
uses.
[Corn,
field,
grain]

Corn,
sweet,
fodder
1.0
1.0
/
(TBD
4)
Additional
crop
field
trial
data
are
required.
[Corn,
sweet,
stover]

Corn,
sweet,
forage
1.0
1.0
/
(TBD
4
)
Additional
crop
field
trial
data
are
required.

Cottonseed
0.25
Reassign
This
tolerance
should
be
reclassified
under
180.184(
c)
because
use
of
linuron
on
cotton
is
restricted
to
east
of
the
Rocky
Mountains.

Goats,
fat
1.0
0.2
[Goat,
fat]

Goats,
mbyp
1.0
0.1
[Goat,
meat
byproducts,
except
kidney
and
liver]

Goats,
meat
1.0
0.1
[Goat,
meat]

Hogs,
fat
1.0
0.05
[Hog,
fat]

Hogs,
mbyp
1.0
0.1
[Hog,
meat
byproducts]

Hogs,
meat
1.0
0.05
[Hog,
meat]

Horses,
fat
1.0
0.2
[Horse,
fat]
Commodity
Current
Tolerance
(ppm)
1
Reassessed
Tolerance
Level
(ppm)
Comment/
Correct
Commodity
Definition
11
Horses,
mbyp
1.0
0.1
[Horse,
meat
byproducts,
except
kidney
and
liver]

Horses,
meat
1.0
0.1
[Horse,
meat]

Parsnips
(with
tops)
0.5
0.05
[Parsnip,
root]

Parsnips
(without
tops)
0.5
0.05
[Parsnip,
root]

Potatoes
1.0
Reassign
This
tolerance
should
be
reclassified
under
180.184(
c)
as
use
of
linuron
on
potatoes
is
restricted
to
east
of
the
Rocky
Mountains.

Sheep,
fat
1.0
0.2
Sheep,
mbyp
1.0
0.1
[Sheep,
meat
byproducts,
except
kidney
and
liver]

Sheep,
meat
1.0
0.1
Sorghum,
fodder
1.0
1.0
/
(TBD
4)
Additional
crop
field
trial
data
are
required.
[Sorghum,
stover]

Sorghum,
forage
1.0
1.0
/
(TBD
4)
Additional
crop
field
trial
data
are
required.

Sorghum,
grain
(milo)
0.25
0.25
[Sorghum,
grain]

Soybeans
(dry)
1.0
1.0
[Soybeans,
seed]

Soybeans
(succulent)
1.0
1.0
[Soybean,
seed]

Soybean,
forage
1.0
Revoke
These
tolerances
should
be
revoked,
provided
all
pertinent
labels
are
amended
to
include
the
following
feeding
restriction
on
the
product
labels:
"The
feeding
of
treated
forage
or
hay
to
livestock
is
prohibited.
Commodity
Current
Tolerance
(ppm)
1
Reassessed
Tolerance
Level
(ppm)
Comment/
Correct
Commodity
Definition
12
Soybean,
hay
1.0
Revoke
Wheat,
forage
0.5
Reassign
These
tolerances
should
be
reclassified
under
180.184(
c),
as
use
of
linuron
on
wheat
is
restricted
to
ID,
OR,
and
WA.
Wheat,
grain
0.25
Reassign
Wheat,
hay
0.5
Reassign
Wheat,
straw
0.5
Reassign
Tolerances
listed
under
40
CFR
§180.184(
c):

Parsley
0.25
0.25
Tolerances
established
under
40
CFR
§180.184(
a):

Cattle,
kidney
Not
applicable
2.0
Cattle,
liver
Not
applicable
2.0
Celeraic
Not
applicable
1.0
Goat,
kidney
Not
applicable
2.0
Goat,
liver
Not
applicable
2.0
Horse,
kidney
Not
applicable
2.0
Horse,
liver
Not
applicable
2.0
Milk
Not
applicable
0.05
Rhubarb
Not
applicable
0.5
Sheep,
kidney
Not
applicable
2.0
Sheep,
liver
Not
applicable
2.0
Tolerances
established
under
40
CFR
§180.184(
c):

Cotton,
gin
byproducts
Not
applicable
9.0
Additional
field
trial
data
and/
or
information
is
required.

Cottonseed
0.25
0.05
This
tolerance
should
be
reclassified
under
180.184(
c)
because
use
of
linuron
on
cotton
is
restricted
to
east
of
the
Rocky
Mountains.
[Cotton,
undelinted
seed]
Commodity
Current
Tolerance
(ppm)
1
Reassessed
Tolerance
Level
(ppm)
Comment/
Correct
Commodity
Definition
13
Potatoes
1.0
0.2
This
tolerance
should
be
reclassified
under
180.184(
c)
because
use
of
linuron
on
potatoes
is
restricted
to
east
of
the
Rocky
Mountains.
[Potato]

Wheat,
forage
0.5
0.5
/
(TBD
4)
Crop
field
trial
data
are
required.
This
tolerance
should
be
reclassified
under
180.184(
c),
because
use
of
linuron
on
wheat
is
restricted
to
ID,
OR,
and
WA.

Wheat,
grain
0.25
0.05
This
tolerance
should
be
reclassified
under
180.184(
c),
because
use
of
linuron
on
wheat
is
restricted
to
ID,
OR,
and
WA.

Wheat,
hay
0.5
0.5
/
(TBD
4)
Crop
field
trial
data
are
required.
This
tolerance
should
be
reclassified
under
180.184(
c),
because
use
of
linuron
on
wheat
is
restricted
to
ID,
OR,
and
WA.

Wheat,
straw
0.5
2.0
The
registrants
may
wish
to
generate
additional
crop
field
trial
data
at
1x
instead
of
proposing
an
increased
tolerance.
This
tolerance
should
be
reclassified
under
180.184(
c),
because
use
of
linuron
on
wheat
is
restricted
to
ID,
OR,
and
WA.

1
Expressed
in
terms
of
linuron
per
se.
2
Refer
to
sections
on
Magnitude
of
the
Residue
in
Crop
Plants,
Magnitude
of
the
Residue
in
Processed
Food/
Feed,
and
Magnitude
of
the
Residue
in
Meat,
Milk,
Poultry,
and
Eggs
for
detailed
discussion
of
residues
in
plant
and
animal
commodities.
3
Expected
residues
at
a
1x
feeding
level.
4
These
commodities
were
included
in
the
dietary
risk
assessment
using
the
Current
Tolerance
level.
Additional
confirmatory
field
trial
residue
data
are
required;
therefore,
the
final
tolerance
may
be
revised.

Codex/
International
Harmonization
No
maximum
residue
limits
(MRLs)
for
linuron
have
been
established
by
Codex
for
any
agricultural
commodity.
In
addition,
no
Canadian
nor
Mexican
MRLs
have
been
established
for
linuron.
Therefore,
no
compatibility
questions
exist
with
respect
to
U.
S.
tolerances.
14
Summary
of
Pending
Data
A
developmental
neurotoxicity
study
is
required
and
may
further
define
the
potential
neuroendocrine
effects
observed
in
the
3­
generation
reproduction
rat
study,
the
cross
mating
in
rats
study,
and
the
leydig
cell
tumorigenesis
in
rats
study.
A
28­
day
inhalation
study
is
also
required.
Two
environmental
fate
studies
are
required,
a
leaching/
adsorption/
desorption
study
will
provide
data
on
the
mobility
of
linuron
and
a
terrestrial
field
dissipation
study
will
provide
information
on
what
happens
to
linuron
under
field
conditions.
The
requirements
for
storage
stability
are
not
fulfilled
including
the
final
reports
for
ongoing
storage
stability
studies
on
cotton
processed
commodities
and
sweet
corn
commodities.
In
addition,
information
pertaining
to
sample
storage
intervals
and
conditions
for
samples
of
parsnips
and
for
the
animal
feeding
studies
are
necessary.
The
requirements
for
magnitude
of
the
residue
in
plants
are
not
fulfilled
for:
celery,
corn,
sorghum,
and
wheat.
