Linuron
Summary
Uses
°
Linuron
is
a
substituted
urea,
selective
herbicide
registered
for
use
on
asparagus,
carrots,
celery,
field
and
sweet
corn,
cotton,
parsley,
parsnips,
potatoes,
sorghum,
soybeans,
and
wheat
for
control
of
a
variety
of
weed
species
including
annual
morning
glory,
rye
grass,
and
barnyard
grass.
In
addition,
three
new
uses
are
proposed
for
use
on
cotton
gin
by­
products,
celeriac,
and
rhubarb.
There
are
no
registered
residential
uses
of
linuron
products.

°
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
can
be
applied
using
ground
equipment
including
band
sprayer,
boom
sprayer,
sprinkler
irrigation,
and
tractor
mounted
sprayer.

°
There
are
approximately
four
hundred
thousand
pounds
of
linuron
active
ingredient
used
in
the
U.
S.
annually.

Health
Effects
C
Linuron
has
low
acute
toxicity
but
developmental
and
potential
neuroendocrine
effects
were
observed
in
the
3­
generation
reproduction
rat
study,
the
cross
mating
in
rats
study,
and
the
leydig
cell
tumorigenesis
in
rats
study.
In
a
prenatal
oral
developmental
rat
study,
linuron
caused
increased
post­
implantation
loss
and
fetal/
litter
resorptions.
In
a
chronic
dog
feeding
study,
blood
effects
were
found
which
include
reduced
hemoglobin,
hematocrit,
and
erythrocyte
counts.
In
reproductive
studies,
there
is
evidence
for
testicular
lesions
and
decreased
fertility.

Dietary
Risks
°
Based
on
highly
refined
Tier
III
analyses,
both
acute
and
chronic
dietary
risk
from
exposure
to
linuron
is
low
(<
10%
and
<35%
of
the
Population
Adjusted
Dose
respectively)
for
all
populations
and
is
below
the
Agency's
level
of
concern.
The
Agency
has
reassessed
all
40
tolerances
for
linuron
and
can
make
a
FQPA
safety
determination.

Drinking
Water
Risks
°
Based
on
PRZM/
EXAMS
IR­
PCA
(Tier
II)
modeling,
acute
drinking
water
Estimated
Environmental
Concentrations
(EECs)
of
linuron
in
either
ground
water
or
surface
water
are
less
than
the
acute
Drinking
Water
Level
of
Comparison
(DWLOCs)
and
below
the
Agency's
level
of
concern.
°
Based
on
monitoring
data
from
the
1992
USEPA
Pesticide
in
Groundwater
Database,
the
chronic
drinking
water
EEC
of
linuron
in
ground
water
is
less
than
the
chronic
DWLOC
and
below
the
Agency's
level
of
concern.

°
Based
on
PRZM/
EXAMS
IR­
PCA
(Tier
II)
modeling,
the
chronic
drinking
water
EEC
(18
ppb)
for
linuron
in
surface
water
slightly
exceeds
the
chronic
DWLOC
(6
ppb).
The
EEC
is
based
on
upper­
end
input
parameters
such
as
87%
cropped
area.
The
EEC
is
most
likely
higher
than
concentrations
that
would
actually
be
found
in
drinking
water.
Nonetheless,
additional
data
are
being
required
that
will
further
refine
the
chronic
drinking
water
risk
assessment.
A
leaching/
adsorption/
desorption
study
will
provide
important
data
on
the
mobility
of
linuron
and
a
terrestrial
field
dissipation
study
will
provide
information
on
what
happens
to
linuron
under
field
conditions.

Aggregate
Risks
°
Aggregate
(food
+
drinking
water)
acute
risk
from
both
surface
and
ground
water
is
low
and
below
the
Agency's
level
of
concern.

°
Aggregate
(food
+
drinking
water)
chronic
risk
from
ground
water
is
low
and
below
the
Agency's
level
of
concern.

°
Aggregate
(food
+
drinking
water)
chronic
risk
from
surface
water
is
above
the
Agency's
level
of
concern
because
the
EEC
(18
ppb)
slightly
exceeds
the
chronic
DWLOC
(6
ppb)
for
infants
and
children,
the
most
sensitive
population
subgroups.
The
EEC
is
based
on
upper­
end
input
parameters
such
as
87%
cropped
area.
The
EEC
is
most
likely
higher
than
concentrations
that
would
actually
be
found
in
drinking
water.
Nonetheless,
additional
data
are
being
required
that
will
further
refine
the
chronic
drinking
water
risk
assessment.
A
leaching/
adsorption/
desorption
study
will
provide
important
data
on
the
mobility
of
linuron
and
a
terrestrial
field
dissipation
study
will
provide
information
on
what
happens
to
linuron
under
field
conditions.

Occupational
and
Ecological
Risks
°
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.
A
occupational
risk
assessment
was
performed
for
these
two
new
uses
and
they
do
not
present
risks
of
concern
for
the
Agency.
