1
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
Washington,
D.
C.
20460
MEMORANDUM
July
27,
2004
Chemical:
chlorsulfuron
PC
code:
118601
DP
bar
code:
D292626
SUBJECT:
Revised
assessment
of
risk
to
non­
target
plants
associated
with
chlorsulfuron
spray
drift
From:
Norman
Birchfield,
Senior
Biologist
Peer
Review:
Kevin
Costello,
Risk
Assessment
Process
Leader
Thru:
Elizabeth
Behl,
Chief
Environmental
Risk
Branch
4
Environmental
Fate
and
Effects
Division
(
7507C)

To:
Christina
Scheltema,
Susan
Jennings
Special
Review
and
Reregistration
Division
(
7508C)

Summary
The
following
assessment
is
focused
primarily
on
chlorsulfuron
use
on
crops
and
is
intended
to
accurately
reflect
the
most
important
application
conditions
actually
used
in
applying
chlorsulfuron
to
assess
spray
drift
risks
to
non­
target
plants.
Application
parameters
used
by
aerial
applicators
in
Washington
and
Oregon
were
used
to
estimate
a
range
of
spray
drift
levels
in
this
assessment.
Reports
of
set
ups
for
ground
boom
applications
were
not
available
and
thus
ground
boom
configurations
were
assumed
to
include
the
range
of
values
available
in
the
2
AgDRIFT
model.

Risks
to
non­
target
plants
resulting
from
spray
drift
from
ground
and
aerial
applications
of
chlorsulfuron
are
dependent
upon
a
number
of
factors.
This
analysis
suggests
that
most
plant
species
are
likely
to
be
affected
at
low
levels
(
10%
reductions
in
shoot
weight)
more
than
1000
feet
downwind
of
applications
conducted
in
winds
speeds
of
10
mph.
Under
certain
conditions,
80%
effect
levels
may
occur
to
more
sensitive
species
at
1000
feet
or
more
downwind.
Higher
effect
levels
are
triggered
more
frequently
by
aerial
applications
than
with
ground
boom
applications
and
more
frequently
with
finer
sprays.

Laboratory
toxicity
data
used
in
this
analysis
were
limited
to
effects
occurring
in
a
relatively
short
amount
of
time
after
a
single
exposure.
A
number
of
published
reports
suggest
that
chlorsulfuron,
and
other
herbicides
with
the
same
mode
of
action,
may
result
in
delayed
effects
on
crop
yield
and
plant
reproduction
at
levels
lower
than
those
noted
to
cause
short­
term
visible
effects
(
for
a
review
see
Ferenc
2001).
If
reproductive
effects
occur
at
similar
or
lower
levels
than
laboratory
phytotoxicity
data
used
in
this
analysis,
delayed
effects
may
occur
at
distances
substantially
greater
than
1000
feet
from
applications.

Background
Mode
of
Action
Chlorsulfuron's
herbicidal
effect
results
from
its
inhibition
of
an
enzyme
involved
in
amino
acid
biosynthesis.
It
may
be
absorbed
either
through
the
roots
or
the
foliage
and
is
mobile
within
the
plant
and
binds
to
the
acetolactate
synthase
enzyme.
Soil
moisture
increases
the
phytotoxicity
of
chlorsulfuron
by
increasing
availability
and
absorption
by
the
roots.
Although
chlorsulfuron
is
herbicidal
when
absorbed
by
roots,
herbicide
which
contacts
foliage
is
also
phytotoxic.
Foliar
absorption
may
increase
when
chlorsulfuron
is
tank
mixed
with
an
oil
or
surfactant.
Chlorsulfuron
may
be
applied
either
pre­
or
post
emergence.
Phytotoxicity
data
show
that
chlorsulfuron
affects
plants
in
both
seedling
emergence
and
the
vegetative
vigor
tests
at
low
levels.
Chlorsulfuron
tolerant
plants,
such
as
grains,
resist
herbicidal
effects
by
metabolizing
the
herbicide
before
it
causes
toxicity
(
Weed
Science
Society
1989).

Plant
Symptoms
Chlorsulfuron
exposure
may
cause
visible
symptoms
in
days
or
weeks
or
delayed
effects
on
reproduction
(
fruit
and
seed
production)
may
occur
weeks
or
months
after
exposure.
3
Plants
that
have
absorbed
sufficient
chlorsulfuron
on
their
foliage,
in
the
short
term,
may
show
initial
symptoms
of
spotting,
and
leaf
puckering
or
twisting
(
Felsot
et
al
1996).
Exposed
plants
also
may
show
chlorosis
and
discolored
veins
(
http://
www.
psu.
missouri.
edu/
soydoc/
files/
weed/
aasynthesis.
htm).
4
Figure
1.
Signs
of
chlorsulfuron
induced
phytotoxicity.
Reddish
colored
veins
(
top)
and
chlorosis
(
bottom)
are
apparent.
5
Chlorsulfuron
symptoms
may
become
more
pronounced
and
lead
to
plant
death
or
the
plant
may
outgrow
the
symptoms
in
1
to
2
months
depending
on
the
sensitivity
of
the
plant
and
the
magnitude
of
the
exposure.
Developmental/
reproductive
effects
of
chlorsulfuron
exposure
may
not
be
apparent
for
three
or
more
months
after
exposure.
Reduced
seed
and
fruit
development
resulting
from
chlorsulfuron
exposure
has
been
documented
in
canola,
smartweed,
soybean,
and
sunflower
(
Fletcher
et
al
1996).
Because
reproductive
effects
may
occur
in
the
absence
of
other
more
immediate
symptoms
of
herbicide
exposure,
it
is
expected
to
be
difficult
to
recognize
delayed
chlorsulfuron
toxicity
in
the
field.

Use
Pattern
Chlorsulfuron
is
used
predominately
on
grain
crops
such
as
wheat.
According
to
the
USGS
and
USDA,
this
use
accounts
for
more
than
98%
of
agricultural
chlorsulfuron
usage
(
http://
ca.
water.
usgs.
gov/
pnsp/
use92/
chlrsulf.
html).
The
maximum
application
rate
for
wheat
on
the
Glean
product
label
0.023
lbs
active
ingredient/
acre.
Product
label
rates
for
wheat
are
0.0078
to
0.016
lbs
ai
/
acre
with
application
per
crop
(
Finesse
product
label).
Up
to
0.0625
lbs
ai/
acre
may
be
used
on
turf
and
higher
application
rates
are
allowed
for
industrial
areas.

Chlorsulfuron
is
applied
as
a
liquid
spray
and,
for
most
uses,
may
be
applied
by
ground
or
air.
Directions
for
ground
applications
to
wheat
(
Glean
label)
suggest
that
spray
volume
should
be
at
least
3
gallons/
acre
for
flat
fan
nozzles
or
20
gallons/
acre
for
Raindrop
or
flood
jet
nozzles.
The
lower
volume
is
presumably
allowed
for
the
flat
fan
nozzle
because
this
commonly
used
nozzle
can
produce
a
fine
enough
spray
to
cover
the
field
with
the
low
volume
of
3
gallons/
acre.
With
a
volume
of
3
gallons/
acre,
a
relatively
coarse
spray
would
result
in
too
few
drops
per
unit
area
to
adequately
distribute
the
herbicide
and
control
weeds
in
that
area.
Raindrop
and
flood
jet
nozzles
are
two
models
of
nozzle
that
can
be
used
to
produce
coarser
sprays.
With
coarser
sprays,
higher
volumes
are
generally
necessary
to
result
in
adequate
coverage
of
treated
fields
and
weeds
for
control.
(
For
information
on
the
design
of
flat
fan
and
flood
jet
nozzles
and
their
relative
drift
levels
see
http://
www.
hardi­
international.
com/
Agronomy/
Education_
Material/
pdf/
04a.
pdf
or
http://
lancaster.
unl.
edu/
ag/
factsheets/
289.
htm).

DuPont
conducted
a
small
survey
of
aerial
applicators
as
an
indication
of
typical
aerial
application
parameters
(
see
Appendix
1).
The
DuPont
survey
included
15
aircraft
set
ups
for
chlorsulfuron
applications
in
Washington
and
Oregon.
Reported
in
the
survey
is
the
application
volume
(
gallons
per
acre),
boom
length
(
relative
to
wingspan),
nozzle
type,
nozzle
angle,
aircraft
speed,
spray
pressure,
and
variables
that
were
assumed
in
order
to
calculate
spray
droplet
size.
The
droplets
size
spectra
estimated
from
the
equipment
variables
ranged
from
ASAE
medium
to
ASAE
coarse.
6
Toxicity
The
standard
toxicity
level
EFED
uses
for
calculating
risk
quotients
for
non­
endangered
terrestrial
plants
is
the
EC
25.
For
endangered
plants,
the
EC
05
or
the
no
observable
adverse
effect
level
(
NOAEL)
is
used.
The
EC
x
effect
level
represents
an
X%
effect
to
a
group
of
plants.
The
dose
required
to
cause
a
25%
reduction
in
the
average
shoot
height
of
a
group
of
plants
is
an
example
of
an
EC
25
toxicity
level.
Reduction
in
the
dry
weight
of
the
plant
can
also
be
used
in
calculating
the
EC
x.
Visual
effects,
such
as
spotting
or
chlorosis,
are
not
generally
assessed
because
of
difficulty
in
quantifying
the
magnitude
of
the
effect.

Toxicity
tables
for
the
successive
plant
life
stages
(
seedling
emergence
and
vegetative
vigor)
from
EFED's
RED
chapter
(
Balluff
et
al
2003)
are
attached
in
Appendix
2.
The
most
sensitive
species
tested
were
sugarbeet
(
seedling
emergence,
EC
25
3.8
x
10­
5
lbs
ai/
acre)
and
onion
(
vegetative
vigor,
EC
25
4.4x10­
6
lbs/
ai
acre).
The
most
sensitive
effects
measured
in
these
tests
were
reductions
in
shoot
weight
and
plant
height.
The
phytotoxicity
data
was
limited
in
that
the
confidence
in
the
estimated
EC
05
and
NOAEL
was
low.

Non­
target
plants
exposed
to
herbicides
may
be
killed
outright
or
weakened,
reducing
their
fitness.
Non­
lethal
effects
could
cause
plants
to
become
more
susceptible
to
plant
pathogens,
become
less
effective
in
competing
with
sympatric
species,
or
reduce
reproductive
success.
In
instances
where
herbicide
exposure
effects
fertilization
or
seed
production,
reproduction
of
plants
in
the
wild
would
be
expected
to
be
reduced
and
population
level
changes
could
occur.

Selection
and
Representativeness
of
Plants
used
in
Phytotoxicity
Tests
The
plants
used
in
phytotoxicity
tests
are
chosen
primarily
for
due
to
the
availability
of
validated
protocols
and
seed
sources.
Registrants
routinely
screen
potential
products
using
a
wide
variety
of
economically
important
plants
to
determine
if
phytotoxicity
concerns
exist.
The
Pesticide
Assessment
Guideline
Subdivision
J
(
EPA­
540/
9­
82­
020)
states
that
flexibility
is
allowed
in
choosing
species
in
order
to
maximize
use
of
"...
tests
that
are
normally
performed
by
the
developer/
registrant
during
screening
and
initial
field
testing...."
The
registrant
must
test
corn
and
soybeans
primarily
because
of
their
economic
importance
in
US
agricultural.
A
dicot
root
crop
must
also
be
tested
along
with
an
approximately
even
ratio
of
dicots
and
monocots.

The
representativeness
of
plants
used
in
phytotoxicity
testing
of
non­
target
naturally
occurring
plants
is
uncertain.
The
range
of
plants
used
in
testing
is
limited
to
annuals
despite
the
fact
that
woody
plants
and
other
perennials
are
commonly
found
in
agricultural
areas.
Moreover,
7
homogenous
crop
test
plant
seed
lots
lack
the
variation
that
occurs
in
natural
populations,
so
the
test
plants
are
likely
to
have
less
variation
in
response
than
would
be
expected
from
wild
populations.

In
some
instances,
specific
test
species
may
be
indicative
of
an
effect
to
another
naturally
occurring
non­
target
species.
Native
plants
sharing
species,
genus
or
family
affinity
with
the
tested
crop
plant
may
show
similar
levels
of
sensitivity
to
a
pesticide.
For
instance
wild
onions
may
show
similar
sensitivity
to
commercially
grown
onions
to
a
particular
herbicide.
However,
given
the
intensive
breeding
and
selection
that
is
used
to
develop
commercial
strains
of
a
species,
it
is
possible
that
natural
and
commercial
plants
of
the
same
species
may
show
very
different
responses.

Phytotoxicity
Tests
and
Spray
Drift
Spray
drift
exposure
to
plants
away
from
field
edges
is
expected
to
result
in
relatively
few
concentrated
droplets
depositing
on
and
around
plants.
In
contrast,
laboratory
vegetative
vigor
and
seedling
emergence
phytotoxicity
tests,
use
relatively
high
volumes
of
spray
to
better
cover
the
test
plant
or
the
soil
surface.
In
instances
where
an
herbicide's
movement
in
plants
or
soil
is
limited,
the
test
conditions
of
the
phytotoxicity
studies
may
result
in
higher
measured
toxicity
than
would
result
from
spray
drift
away
from
the
field's
edge.
In
the
instance
of
herbicides
that
are
mobile
within
plants
and
soil,
such
as
chlorsulfuron
which
is
mobile
in
soil
and
can
be
transported
throughout
exposed
plants,
the
volume
of
spray
used
for
the
exposure
may
not
alter
the
magnitude
of
the
toxic
effect.

Exposure
Current
Label
Directions
This
assessment
focuses
on
the
effects
of
spray
drift
on
non­
target
terrestrial
plants.
Exposure
from
chlorsulfuron
runoff
can
also
cause
phytotoxicity
to
non­
target
plants.
Chlorsulfuron's
mobility
and
persistence
in
soil
suggests
that
runoff
may
be
an
important
route
of
exposure
to
non­
target
plants
down
slope
of
application
areas.
Plants
in
up­
slope
areas
are
not
affected
by
runoff
but
may
be
damaged
by
spray
drift.

Chlorsulfuron
product
labels
have
very
few
restrictions
on
how
and
under
what
conditions
the
product
may
be
applied.
For
instance
there
are
no
droplet
size,
wind
speed,
or
boom
height
restrictions.
The
absence
of
bounds
makes
it
more
difficult
to
determine
what
conditions
should
be
used
for
risk
assessment.
The
absence
of
basic
mandatory
label
language
also
allows
8
applicators
to
make
unnecessarily
high
drift
applications.
Applicator
common
sense
would
prevent
worst
case
applications
but
may
not
result
in
optimal
applications.
For
instance
it
is
unlikely
that
an
applicator
would
make
a
ground
boom
application
with
a
high
boom
and
a
fine
spray
because
drifting
spray
would
be
visible
and
it
would
be
apparent
that
the
efficiency
of
the
application
was
low.
However,
without
proper
guidance
an
applicator
may
use
a
low
boom
but
a
finer
spray
than
necessary
to
achieve
control.
Under
this
scenario
drifting
spray
would
be
less
visible
but
still
unnecessarily
high.
Specifying
basic
spray
drift
control
measures
provides
applicators
with
the
necessary
information
to
perform
an
effective
and
low­
drift
application
and
risk
assessors
with
the
necessary
information
to
model
drift.

AgDRIFT
Background
AgDRIFT
is
a
computer
model
that
can
be
used
to
estimate
downwind
deposition
of
spray
drift
from
aerial,
ground
boom,
and
orchard
and
vineyard
airblast
applications.
The
model
contains
three
tiers
of
increasing
complexity.
In
Tier
1,
the
user
can
assess
downwind
deposition
from
a
single
application
from
all
three
application
methods
under
default
conditions.
The
current
version
of
AgDRIFT
only
allows
Tier
1
level
analyses
for
ground
and
airblast
application
methods.
In
higher
tiers
more
options
are
available
for
aerial
applications.
The
aerial
portion
of
the
model
is
based
on
a
mechanistic
US
Forest
Service
model
(
AGDISP.
Bilanin
et
al
1989).
The
ground
boom
and
orchard
airblast
portions
are
empirical
models
based
on
data
collected
by
the
Spray
Drift
Task
Force
(
SDTF).
The
SDTF
field
data
were
used
to
validate
the
aerial
portion
of
AgDRIFT
(
Bird
et
al
1996a
and
1996b).
AgDRIFT
was
developed
under
a
cooperative
research
and
development
agreement
between
EPA,
USDA,
and
the
SDTF.

Aerial
AgDRIFT:
The
most
important
factors
affecting
drift
from
aerial
applications
are
spray
quality
(
droplet
size),
release
height,
and
wind
speed.
The
aerial
part
of
the
model
predicts
mean
values
based
on
the
inputs
provided.
The
Tier
1
aerial
results
are
generated
using
the
specified
droplet
size
spectra,
10
foot
release
height,
and
a
10
mph
wind
speed.
When
wind
speed
and/
or
release
height
is
lower
than
the
modeled
values
the
spray
drift
levels
would
be
expected
to
be
lower.
Conversely,
in
instances
where
applications
may
be
made
in
higher
wind
speeds
or
at
a
higher
release
height
these
inputs
may
not
be
adequately
conservative
and
higher
tier
modeling
may
be
necessary.

Ground
boom
sprayers
in
AgDRIFT:
The
most
important
factors
affecting
drift
from
ground
boom
applications
are
spray
quality,
release
height,
and
wind
speed.
The
ground
boom
part
of
AgDRIFT
is
based
on
field
trial
data
from
bare
ground
applications.
The
results
of
the
model
1
Toxicity
slopes
are
calculated
from
dose­
response
relationship
of
chlorsulfuron
on
of
the
test
plant
species.
Species
with
high
(
steep)
slopes
show
large
increases
in
toxicity
from
small
increases
in
exposure.
Species
with
low
(
shallow)
slopes
show
small
increases
in
toxicity
from
relatively
large
increases
in
exposure.

2
A
log
normal
toxicity
distribution
is
assumed.
The
following
equation
is
used
to
calculate
the
various
EC
x
levels:
[
EC
25
/
10­
0.67/
slope]
x
10­
a/
slope
=
EC
x
where
a
=
1.28,
0.84,
0.54,
0.25,
0,
­
0.25,
­
0.54,
­
0.84,
and
­
1.28
for
EC
10,
EC
20,
EC
30,
EC
40,
EC
50,
EC
60,
EC
70,
EC
80,
EC
90,
respectively.

9
reflect
the
quality
and
conditions
of
the
data
on
which
it
is
based.
The
data
from
the
field
trials
were
grouped
into
categories
by
spray
quality
(
droplet
size)
and
release
height.
Results
from
field
trials
conducted
with
different
wind
speeds
were
averaged.
The
average
wind
speed
over
all
the
trials
was
approximately
10
mph.
AgDRIFT
outputs
for
ground
boom
applications
estimate
the
50th
and
90th
percentile
of
data
collected
from
field
trials.
For
this
analysis
the
50th
percentile
data
was
used.
The
field
trial
data
were
not
corrected
for
incomplete
analytical
recoveries,
suggesting
the
true
mean
deposition
values
would
be
approximately
20%
higher
than
the
model's
deposition
results.

Phytotoxicity
and
Downwind
Distance
Using
the
AgDRIFT
model
(
version
2.01)
and
registrant
submitted
phytotoxicity
data
(
MRID
42587201,
McKelvey
and
Kuratle
1992)
it
is
possible
to
estimate
distances
downwind
from
application
areas
at
which
a
particular
toxic
effect
level
would
be
experienced
by
a
particular
tested
plant
species.
To
make
Figures
2
through
7
below,
EC
25
values
(
for
vegetative
vigor
shoot
weight)
of
the
tested
species
were
used
with
the
toxicity
slope1
from
each
species
to
calculate
EC
10,
EC
20,
EC
30,
to
EC
90
effect
levels2.
These
EC
x
values
were
entered
into
an
Excel
spreadsheet
with
Tier
1
AgDRIFT
(
version
2.01)
deposition
distance
results
and
the
maximum
chlorsulfuron
application
rate
for
pasture/
rangeland
(
0.0625
lbs
ai/
acre).
Excel
then
calculated
estimated
downwind
deposition
levels
for
chlorsulfuron
use
on
pasture/
rangeland
and
compared
the
deposition
values
to
the
EC
x
values
to
identify
the
downwind
distance
at
which
the
EC
x
values
would
be
reached.
Excel
arranged
the
distances
into
three
dimensional
bar
charts
showing
the
downwind
distance
at
which
a
particular
toxicity
level
for
each
species
is
expected
to
occur
under
the
Tier
1
AgDRIFT
conditions
with
the
specified
application
rate.

The
barcharts
shown
in
Figures
2
through
7
are
specific
to
the
maximum
application
rate
for
pasture/
rangeland
(
0.0625
lbs
ai/
acre).
Appendix
3
contains
phytotoxicity
barcharts
for
a
middle
of
the
range
application
rate
from
the
Finesse
product
label
for
preemergent
spraying
to
wheat
(
0.012
lbs
ai/
acre).
10
11
10
30
50
70
90
wheat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Aerial:
Coarse
Spray
Figure
2.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
an
aerial
application
conducted
with
a
coarse
spray
in
a
10
mph
wind
with
a
10
foot
release
height
at
an
application
rate
of
0.0625
lbs
chlorsulfuron
per
acre.
The
plant
species
listed
on
the
bottom
right
axis
are
test
species
for
which
the
registrant
submitted
phytotoxicity
data
(
the
toxicity
slope
for
cucumber
was
unavailable
so
cucumber
results
are
not
shown).
12
10
30
50
70
90
wheat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Aerial:
Medium
Spray
Figure
3.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
an
aerial
application
conducted
with
a
medium
spray
in
a
10
mph
wind
with
a
10
foot
release
height
at
an
application
rate
of
0.0625
lbs
chlorsulfuron
per
acre.
The
toxicity
slope
for
cucumber
was
unavailable.
13
10
30
50
70
90
wheat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Ground:
Low
Boom,
Medium­
Coarse
Spray
Figure
4.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
a
ground
boom
application
conducted
with
a
medium/
coarse
spray
in
an
approximate
10
mph
wind
with
a
2
foot
release
height
at
an
application
rate
of
0.0625
lbs
chlorsulfuron
per
acre.
The
toxicity
slope
for
cucumber
was
unavailable.
14
10
30
50
70
90
w
heat
t
omato
so
rg
hum
co
rn
p
ea
sug
arb
eet
so
yb
ean
rap
e
o
nion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Ground:
HIgh
Boom,
M
e
d
ium­
Coarse
Spray
Figure
5.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
a
ground
boom
application
conducted
with
a
medium/
coarse
spray
in
an
approximate
10
mph
wind
with
a
4
foot
release
height
at
an
application
rate
of
0.0625
lbs
chlorsulfuron
per
acre.
The
toxicity
slope
for
cucumber
was
unavailable.
15
10
30
50
70
90
wheat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Ground:
Low
Boom,
Medium
Spray
Figure
6.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
a
ground
boom
application
conducted
with
a
medium
spray
in
an
approximate
10
mph
wind
with
a
2
foot
release
height
at
an
application
rate
of
0.0625
lbs
chlorsulfuron
per
acre.
The
toxicity
slope
for
cucumber
was
unavailable.
16
10
30
50
70
90
wheat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Ground:
HIgh
Boom,
Medium
Spray
Figure
7.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
a
ground
boom
application
conducted
with
a
medium
spray
in
an
approximate
10
mph
wind
with
a
4
foot
release
height
at
an
application
rate
of
0.0625
lbs
chlorsulfuron
per
acre.
The
toxicity
slope
for
cucumber
was
unavailable.
17
Discussion
Based
on
the
phytotoxicity
study
results
for
wheat
and
chlorsulfuron
use
sites
such
as
pasture/
range
land,
certain
grass
species
appear
to
be
tolerant
to
acute
chlorsulfuron
effects.
Some
tolerant
species
apparently
are
susceptible
to
reproductive
effects
from
single
exposures
based
on
product
claims
of
inhibiting
seed
head
formation
described
on
some
product
labels.
Because
of
lack
of
data,
reproductive
effects
cannot
be
evaluated
at
this
time.
Available
data
suggest
that
it
is
unlikely
that
field
edges
and
areas
downwind
comprised
of
grass
would
be
greatly
affect
by
acute
effects
of
chlorsulfuron.

Figures
2
through
7
above
show
the
phytotoxicity
downwind
of
chlorsulfuron
applications
is
expected
to
vary
based
on
a
number
of
parameter
including
application
method
(
ground
boom
versus
aerial),
the
droplet
size
spectrum,
and
the
release
height.

Figures
2
through
7
show
effects
(
EC
x
effect
levels)
by
distance,
but
do
not
show
at
what
distance
plants
are
likely
to
be
killed
outright.
When
plants
are
tested
by
pesticide
companies
for
efficacy
generally
a
70%
effect
level
is
considered
to
be
a
threshold
for
lethal
effects
to
a
healthy
weed
(
Pallett
2003).
Thus
the
EC
70
effect
level
can
serve
as
estimate
of
when
non­
target
plants
are
expected
to
have
a
high
likelihood
of
rapid
death
similar
to
the
desired
effect
for
weed
species.

Aerial
For
aerial
applications,
medium
and
coarse
sprays
are
apparently
the
most
commonly
used
sprays
by
aerial
applicators
in
Washington
and
Oregon
­
see
Appendix
1.
Medium
spray
is
expected
to
produce
higher
drift
levels
than
coarse
sprays
resulting
in
greater
phytotoxicity
at
greater
downwind
distances.
Using
the
EC
70
as
an
estimate
for
an
exposure
that
would
lead
to
rapid
death,
Figure
3
shows
that
3
of
the
9
tested
species
downwind
of
an
application
with
a
medium
spray
would
be
expected
to
be
killed
soon
after
application
in
an
area
stretching
from
the
edge
of
the
treated
field
to
a
distance
exceeding
1000
feet
downwind
from
the
treatment
area.
Using
a
coarse
spray,
Figure
2
shows
that
2
of
the
9
tested
species
would
be
expected
to
be
killed
from
the
edge
of
the
field
to
a
distance
exceeding
1000
feet
downwind
from
the
treatment
area.
Aerial
applications
with
a
medium
spray
are
expected
to
affect
at
least
8
of
the
9
species
tested
at
the
EC
20
level
or
above
for
shoot
weight
greater
than
1000
feet
downwind
of
applications.
In
other
words,
a
20%
or
more
reduction
in
shoot
weight
would
be
expected
for
at
least
8
of
9
tested
species
for
over
1000
feet
downwind
of
applications
under
the
assumed
conditions.
With
a
coarse
spray,
under
the
same
conditions,
at
least
8
of
the
9
tested
species
are
expected
to
be
affected
at
the
EC
10
level
1000
feet
or
more
downwind
(
i.
e.
a
10%
reduction
in
shoot
weight
in
an
areas
stretching
for
more
than
1000
feet
downwind).
18
Ground
boom
In
all
instances
the
ground
boom
applications
modeled
resulted
in
lower
drift
deposition
levels
and
downwind
phytotoxicity
than
modeled
aerial
applications.
Ground
boom
deposition
values
were
affected
by
both
droplet
size
and
release
height.
Spray
drift
and
predicted
off­
target
effects
can
be
reduced
by
lowering
the
release
height
and/
or
increasing
spray
droplet
size.

Under
the
lowest
ground
boom
drift
conditions
allowed
by
AgDRIFT
2.01
(
2
foot
boom
height
and
medium/
coarse
spray),
5
of
9
tested
species
would
be
expected
to
be
rapidly
killed
from
10
to
85
feet
downwind
the
treated
area
(
Fig.
4).
Under
the
same
conditions,
5
of
the
9
tested
species
would
be
affected
at
the
EC
10
level
in
the
area
stretching
for
the
edge
of
the
field
to
beyond
1000
feet
downwind.

Under
the
highest
ground
boom
drift
conditions
(
4
foot
boom
and
medium
spray),
plant
species
would
be
expected
to
be
killed
in
the
area
that
stretches
from
0
to
10
feet
(
for
8
of
9
tested
plants)
and
0
to
500
feet
(
for
the
most
sensitive
tested
plant)
downwind
of
the
treated
field
(
Fig.
7).
Under
the
same
conditions,
6­
7
of
the
10
tested
species
are
expected
to
be
affected
at
the
EC
10
level
at
distances
from
0
to
beyond
1000
feet
downwind.
Tested
species
are
expected
to
be
affected
at
the
90%
effect
level
at
10
feet
(
5
of
9
species)
to
150
feet
(
1
of
9
species)
downwind.

Labeling
The
results
of
this
analysis
suggest
that
mandatory
product
labeling
placing
restrictions
on
droplet
size
for
aerial
applications
and
droplet
size
and
boom
height
for
ground
boom
application
may
reduce
risks
associated
with
chlorsulfuron
applications.

An
example
of
potential
mandatory
product
labeling
that
would
be
expected
to
result
in
average
non­
target
plant
risks
equal
to
or
less
than
those
presented
in
Figures
2
though
7
above
is:

For
ground
boom
applications,
apply
with
nozzle
height
no
more
than
2
feet
above
the
ground
or
crop
canopy
and
when
wind
speed
is
10
mph
or
less
at
the
application
site
as
measured
by
an
anemometer.
Use
"
very
coarse"
or
coarser
spray
according
to
ASAE
572
definition
for
standard
nozzles.

For
aerial
applications,
the
boom
width
must
not
exceed
75%
of
the
wingspan
or
90%
of
the
rotary
blade.
Use
upwind
swath
displacement
and
apply
only
when
wind
speed
is
between
3
and
10
mph.
Use
"
coarse"
or
coarser
spray
according
to
ASAE
572
definition
for
standard
nozzles.
19
Typical
values
for
both
wind
speed
and
release
height
are
likely
to
vary
geographically.
Aerial
applicators
balance
low
release
heights
with
flight
safety.
Aerial
applicators
will
generally
use
higher
release
heights
in
hilly
areas
or
fields
with
tall
windbreaks
at
their
boundaries.
For
ground
boom
applications,
high
release
heights
are
used
to
avoid
having
the
ends
of
the
spray
boom
hitting
the
ground
in
uneven
fields
or
when
relatively
high
sprayer
speed
is
desired.
Gorund
boom
relaease
height
can
vary
from
less
than
2
feet
to
more
than
6
feet
above
the
ground
or
crop
camopy.
Average
wind
speed
for
chlorsulfuron
use
areas
vary
with
location
with
higher
wind
speed
occurring
in
plains
states.
Table
1
shows
wind
speeds
ranges
for
some
representative
areas.

Table
1.
Wind
speeds
during
the
windiest
month
of
the
year
for
cities
in
high
agricultural
chlorsulfuron
use
areas.

City,
State
Approximate
location
in
state
Month
Wind
speed
(
mph)

75th
Percentile
50th
Percentile
25th
Percentile
Yakima,
WA
south
central
April
10
6
4.5
Pendleton,
OR
northwestern
April
10.5
6
4.5
North
Platte,
NE
central
southwestern
April
14
11
7
More
wind
speed
data
for
the
locations
in
Table
1
are
shown
in
Appendix
4.

Ecological
Implications
Chlorsulfuron
is
a
selective
herbicide.
Some
species,
such
as
certain
grasses,
are
relatively
tolerant
to
chlorsulfuron
while
other
species
are
sensitive
to
acute
effects
and
reproductive
effects.
If
certain
plants
in
a
plant
community
consisting
of
many
species
are
consistently
selected
against
through
inhibiting
growth,
reducing
reproductive
success,
or
being
killed,
the
sensitive
plant
species
are
likely
to
be
removed
from
the
community.
Plants
under
selective
pressure
are
not
able
to
compete
as
successfully
with
other
plants
for
resources
such
as
light
and
water.
Thus
with
pressure
on
a
particular
group
of
species
other
species
would
be
likely
displace
the
sensitive
species
and
become
more
common.
Changes
in
the
species
composition
in
the
boundaries
of
herbicide­
treated
fields
have
been
noted
in
the
literature
(
Kleijn
and
Snoeijing
1997,
Jobin
et
al
1997).
Given
the
selectivity
of
chlorsulfuron
and
the
drift
potential
associated
with
spray
application
methods,
it
is
expected
that
chlorsulfuron
is
applying
selective
pressure
against
certain
species
downwind
of
application
areas.
The
magnitude
of
the
selective
pressure
is
expected
to
20
depend
on
the
level
of
drift
as
well
as
the
sensitivity
of
exposed
species.

Uncertainty
and
Potential
Refinement
of
Risk
Estimates
A
number
of
uncertainties
exist
in
this
assessment
of
potential
effects
of
chlorsulfuron
spray
drift
to
plants.
With
additional
information
addressing
uncertainties
it
may
be
possible
to
further
refine
this
assessment.
Some
uncertainties
underlying
this
assessment
exist
in:

1)
The
representativeness
of
tested
species
for
non­
target
plant
species
in
chlorsulfuron
use
areas.
In
chlorsulfuron
use
areas
woody
and
other
perennial
species
are
exposed
to
spray
drift
but
their
sensitivity
to
chlorsulfuron
is
uncertain.
Toxicity
data
on
a
wider
range
of
plants
could
be
used
to
reduce
uncertainty
as
to
the
potential
effects
of
chlorsulfuron
on
perennial
and
woody
species
at
field
edges
and
farther
downwind.
2)
The
duration
of
exposure.
Laboratory
data
is
based
on
single
exposures
to
plants
with
observation
continuing
for
two
weeks
after
dosing.
Non­
target
plants
in
chlorsulfuron
use
areas
may
be
exposed
to
multiple
pulses
of
chlorsulfuron.
Data
on
the
effect
of
repeat
exposures
at
environmentally
relevant
levels
could
be
used
to
determine
the
potential
impacts
to
plants
that
are
exposed
to
drift
from
multiple
applications.
3)
The
toxic
endpoint
measured.
Some
chlorsulfuron
product
labels
and
research
on
nontarget
plants
show
chlorsulfuron
negatively
affects
plant
reproduction.
Data
defining
what
exposure
levels
at
various
developmental
stages
result
in
impaired
plant
reproduction
could
be
used
for
assessing
potential
impacts
of
spray
drift
on
plant
reproduction.
4)
The
adequacy
of
laboratory
spraying
treatments
in
representing
spray
drift
far
from
field
boundaries.
Plants
in
laboratory
studies
are
exposed
to
herbicide
in
volumes
of
carrier
that
are
adequate
to
cover
the
test
plants.
Plants
exposed
to
spray
drift
away
from
field
boundaries
would
contact
the
same
amounts
of
herbicides
tested
in
the
laboratory
but
in
much
lower
volumes
of
carrier.
Plants
are
exposed
to
spray
drift
away
far
away
from
the
field
edge
in
discrete
spots
where
droplets
impact
the
plant
foliage
opposed
to
the
diffuse
coating
used
in
lab
studies.
The
effect
of
small
concentrated
exposures
relative
to
diffuse
exposure
is
uncertain.
Data
on
the
effect
of
exposure
volume
on
phytotoxicity
could
be
used
to
refine
effect
level
estimates.

Data
addressing
the
uncertainties
above
could
be
used
to
improve
estimates
of
effects
to
nontarget
plants
in
chlorsulfuron
use
areas.
21
References
Balluff,
D,
and
D.
Young.
2003.
EFED
Risk
Assessment
for
the
Reregistration
Eligibility
Decision
on
Chlorsulfuron.
Environmental
Fate
and
Effects
Division,
Office
of
Pesticide
Programs,
US
Environmental
Protection
Agency.

Felsot,
AS,
MA
Bhatti,
GI
Mink,
and
G
Reisenauer.
1996.
Biomonitoring
with
Sentinel
Plants
to
Assess
Exposure
of
Nontarget
Crops
to
Atmospheric
Deposition
of
Herbicides.
Environmental
Toxicology
and
Chemisty..
15(
4):
452­
459.

Ferenc,
SA.
(
Editor).
Impacts
of
Low­
Dose
High­
Potency
Herbicides
on
Nontarget
and
Unintended
Plant
Species.
Society
of
Environmental
Toxicology
and
Chemistry.
2001.

Fletcher,
JS,
TG
Pfleeger,
HC
Ratsch,
and
R
Hayes.
1996.
Potential
impact
of
low
levels
of
chlorsulfuron
and
other
herbicides
on
growth
and
yield
of
nontarget
plants.
Environmental
Toxicology
and
Chemistry.
15(
7):
1189­
11­
96.

Jobin,
B.,
C
Boutin,
and
JL
DesGranges.
1997.
Effects
of
agricultural
practices
on
the
flora
of
hedgerows
and
woodland
edges
in
southern
Quebec.
Can
J
Plant
Sci
77:
293­
299.

Kleijn,
D.,
and
GI
Snoeijing.
1997.
Field
boundary
vegetation
and
the
effects
of
agrochemical
drift:
botanical
change
caused
by
low
levels
of
herbicide
and
fertilizer.
Journal
of
Applied
Ecology
34:
1413­
1425.

Pallett,
K.
Efficacy
testing
processes
in
Industry:
releveance
for
NTTP
assessment.
Efficacy
Data
Workshop.
August
20,
2003.
Office
of
Pesticide
Programs,
Crystal
City,
Arlington,
VA.

Weed
Science
Society
of
America.
1989.
Herbicide
Handbook.
Published
by
the
Weed
Science
Society
of
America.
Champaign,
IL.
22
Appendix
1
Attachment
from
5/
12/
2003
email
from
Jake
Vukich
(
DuPont)
to
Tyler
Lane
(
Chemical
Review
Manager,
Special
Review
and
Reregistration
Division,
OPP,
EPA):

Non­
Confidential
Version
of
Attachment
A
to
DuPont
Letter
to
USEPA
Dated
May
2,
2003
In
previous
correspondence
with
EPA
regarding
the
droplet
size
spectrum
expected
for
typical
aerial
applications
of
chlorsulfuron
products,
we
proposed
a
small,
informal
survey
of
aerial
applicators
to
determine
typical
aircraft
setups.
To
that
end,
we
have
obtained
descriptions
of
the
spray
setups
used
on
fifteen
aircraft
from
fourteen
applicators
in
Washington
and
Oregon.

To
minimize
drift,
the
Glean
FC
and
Finesse
labels
specify
the
use
of
solid
stream
nozzles
oriented
straight
back
when
the
product
is
applied
by
air
in
the
vicinity
of
sensitive
crops.
As
shown
in
the
attached
table,
most
of
the
aircraft
were
fitted
with
solid
stream
nozzles
with
a
nozzle
angle
of
0,
as
recommended
on
the
label.

The
drop
size
distribution
was
determined
by
the
USDA
 
ARS
model
implemented
in
AgDRIFT

version
2.04.
The
model
provides
a
drop
size
spectrum
for
a
spray
solution
of
water
containing
0.25%
Triton
X­
100.
In
general,
we
expect
the
drop
size
distribution
from
the
model
to
be
shifted
toward
the
fine
size
distribution
as
compared
to
the
size
distribution
for
typical
agricultural
products.
The
inputs
to
the
model
­
nozzle
type,
orientation
angle,
air
speed,
and
pressure
­
were
supplied
by
the
applicators
or
representative
values
were
selected
as
indicated
in
the
attached
table.

The
drop
size
distributions
were
evenly
split
between
ASAE
medium,
medium
to
coarse,
and
coarse.
The
intent
of
the
label
recommendations
is
to
produce
a
drop
size
spectrum
that
will
minimize
drift,
and
we
anticipated
that
most
of
the
solid
stream
nozzles
and
spray
settings
would
produce
a
coarse
size
distribution.
We
attribute
the
difference
between
our
expectations
and
the
model
results
primarily
to
the
higher
than
expected
air
speed
used
for
applications.
We
expected
that
air
speeds
would
be
in
the
range
of
100­
110
mph,
as
it
was
for
aircraft
14
and
15
in
the
attached
table.
In
contrast,
10
of
the
15
applicators
fly
at
a
speed
of
120
mph
or
higher.
The
droplet
size
distribution
shifts
toward
the
fine
distribution
at
higher
speeds.
For
example,
aircraft
4
flown
at
135
mph
produces
a
medium
to
coarse
size
distribution,
while
at
100
mph
would
produce
a
very
coarse
to
extremely
coarse
size
distribution,
according
to
the
USDA
model.
23
Since
the
USDA
model
simulates
drop
size
distributions
for
a
spray
solution
with
low
surface
tension,
those
distributions
are
likely
to
show
a
greater
volume
of
fine
droplets
than
would
be
expected
for
typical
products.
Our
experience
in
the
Pacific
Northwest
suggests
that
the
label
recommendations
have
been
successful
in
reducing
drift,
as
compared
to
the
potential
indicated
by
the
drop
size
distributions
predicted
by
the
USDA
model.
24
Aircraft
Setups
for
Application
of
Chlorsulfuron
Products
in
Washington
and
Oregon
Aircraft
Setup
GPA
Boomlength
Nozzle
type
Angle
Speed
Aircraft
Pressure
Assumed
Variables
Droplet
spectrum
(
ASAE)

1
7
65%
CP
30
deg
plate
0
90­
110
188
Cessna
15
psi
all
orifices,
20­
40psi,
90­

110
mph
Medium
2
5
75%
CP
30
deg
plate
0
110­
120
Airtractor
AT
400
&
502
all
orifices,
20­
40psi,
110­

120
mph
Medium
3
5
75%
D­
8
0
115
Thrush
S2R­
6
DC46
core,
40
psi
Coarse
4
3
68%
Lund
multi­
tip
8
0
135
Turbine
Thrush
40
psi
Medium
to
coarse
5
3
70%
CP
0
deg
0
125­
130
Super
Doer
Thrush
all
orifices,
40
psi
Medium
to
coarse
6
3
68%
Lund
multi­
tip
­
8
0
130
502
&
802
Air
Tractor
40
psi
Medium
to
coarse
7
5
68%
D­
8
0,10
100­
110
Agcat
G164
Super
B
40
psi
Coarse
8
3
68%
CP
Straight
Stream
0
135
Super
Doer
1200
Wright
1820
40
psi
Medium
to
coarse
9
3
68%
Spray
Systems
D­

7
no
core
0
120­
125
Cessna
Husky
20
psi
Medium
10
3
to
5
68%
D8,
10,
or
12
35
120
Airtractor
AT502
­

turbine
DC46
core,
40
psi
Medium
25
11
5
67%
CP
.171
15deg
plate
15
120
Agcat
25
psi
used
5
°
plate,
15
not
in
model
Medium
12
5
67%
D10/
46
0
120
Airtractor
AT502
­

turbine
30
psi
Medium
to
coarse
13
5
67%
D10
0
120
Airtractor
AT502
­

turbine
DC46
core,
40
psi
Coarse
14
3
68%
CP
solid
stream,

no
plate
0
115
Air
tractor
40
psi
Coarse
15
7.5
60%
CP
solid
stream,

no
plate
0
105­
115
Turbo
Agcat
22
psi
Coarse
26
Appendix
2
Non­
target
Terrestrial
Plant
Seedling
Emergence
Toxicity
(
Tier
II)
for
98.2%
Chlorsulfuron
with
buffer
and
Valent
X­
77
surfactant
in
some
solutions.

Species
%
ai
Endpoints
NOAEL
/
EC25
(
lbs
ai/
A)
MRID
No.

Author/
Year
Study
Classification
Cucumber
98.2
Plant
height
Emergence
0.000035
/
0.00025
>
0.00439
/
ND
42587201
McKelvey,
R.
A.,

and
Kuratle,
H.

1992
Supplemental
Pea
Plant
height
Emergence
0.000035
/
0.000113
0.000176
/
0.000281
Rape
Plant
height
Emergence
0.000035
/
0.000113
>
0.00439
/
ND
Soybean
Plant
height
Emergence
0.000875
/
0.0015
>
0.00439
/
ND
Sugarbeet
*
Plant
height
Emergence
0.0000068
/
0.000038
0.000176
/
0.000281
Tomato
Plant
height
Emergence
0.0000351
/
0.000169
>
0.02194
/
ND
Corn
Plant
height
Emergence
<
0.00035
/
0.0003
0.00439
/
0.05
Onion
Plant
height
Emergence
0.000035
/
0.000163
0.000035
/
0.000413
Sorgum
Plant
height
Emergence
0.000163
/
0.00138
>
0.0219
/
ND
*
Used
in
RQ
calculations
27
Non­
target
Terrestrial
Plant
Vegetative
Vigor
Toxicity
(
Tier
II)
for
98.2%
Chlorsulfuron
with
buffer
and
Valent
X­
77
surfactant
in
some
solutions.

Species
%
ai
Endpoints
NOAEL
/
EC25
(
lbs
ai/
A)
MRID
No.

Author/
Year
Study
Classification
Cucumber
98.2
Plant
height
Shoot
weight
0.000225
/
0.001875
0.001125
/
0.006125
42587201
McKelvey,
R.
A.,

and
Kuratle,
H.

1992
Supplemental
Pea
Plant
height
Shoot
weight
00.00045
/
0.00025
0.000045
/
0.000181
Rape
Plant
height
Shoot
weight
0.000045
/
0.0001
0.0000087
/
0.0002
Soybean
Plant
height
Shoot
weight
0.000045
/
0.0000443
0.0000087
/
0.0000193
Sugarbeet
Plant
height
Shoot
weight
0.0000087
/
0.0002062
0.0000087
/
0.0000268
Tomato
Plant
height
Shoot
weight
0.000045
/
0.002
0.000045
/
0.0005562
Corn
Plant
height
Shoot
weight
0.000225
/
0.000625
0.000225
/
0.0001937
Onion
Plant
height
Shoot
weight
*
0.0000087
/
0.0000368
0.0000087
/
0.0000044
Sorgum
Plant
height
Shoot
weight
0.000225
/
0.002625
<
0.000720
/
0.0001562
Wheat
Plant
height
Shoot
weight
0.001125
/
0.05563
0.02813
/
0.005813
Non­
target
Terrestrial
Plant
Vegetative
Vigor
Toxicity
(
Tier
II)
for
98.2%
Chlorsulfuron
with
buffer
and
Valent
X­
77
surfactant
in
some
solutions.

Species
%
ai
Endpoints
NOAEL
/
EC25
(
lbs
ai/
A)
MRID
No.

Author/
Year
Study
Classification
28
*
The
most
sensitive
parameter
in
the
vegetative
vigor
toxicity
study
was
the
sugarbeet
root
weight
(
EC05
=

0.000000019375
lbs
ai/
acre
).
However,
the
EC05
for
onion
shoot
weight
(
0.000000045625
lbs
ai/
acre)
was
used
in
the
risk
assessment
for
endangered
species
because
this
endpoint
provided
stronger
results.
29
10
20
30
40
50
60
70
80
90
wheat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Aerial:
Coarse
Spray
Appendix
3.

Phytotoxicity
resulting
from
spray
drift
during
a
medium
application
rate
Finesse
product
applications
to
preemergent
wheat.
The
application
ranges
from
0.0078
to
0.016
lbs
ai/
acre.
The
mean
of
the
high
and
low
values
was
used
for
these
graphs.

Figure
8.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
an
aerial
application
conducted
with
a
coarse
spray
in
a
10
mph
wind
with
a
10
foot
release
height
at
an
application
rate
of
0.012
lbs
chlorsulfuron
per
acre.
The
plant
species
listed
on
the
bottom
right
axis
are
test
species
for
which
the
registrant
submitted
phytotoxicity
data
(
the
toxicity
slope
for
cucumber
was
unavailable
so
cucumber
results
are
not
shown).
30
10
20
30
40
50
60
70
80
90
wheat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
200
400
600
800
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Aerial:
Medium
Spray
Figure
9.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
an
aerial
application
conducted
with
a
medium
spray
in
a
10
mph
wind
with
a
10
foot
release
height
at
an
application
rate
of
0.012
lbs
chlorsulfuron
per
acre.
The
toxicity
slope
for
cucumber
was
unavailable.
31
10
30
50
70
90
wheat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Ground:
Low
Boom,
Medium­
Coarse
Spray
Figure
10.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
a
ground
boom
application
conducted
with
a
medium/
coarse
spray
in
an
approximate
10
mph
wind
with
a
2
foot
release
height
at
an
application
rate
of
0.012
lbs
chlorsulfuron
per
acre.
The
toxicity
slope
for
cucumber
was
unavailable.
32
10
30
50
70
90
w
heat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Ground:
HIgh
Boom,
Medium­
Coarse
Spray
Figure
11.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
a
ground
boom
application
conducted
with
a
medium/
coarse
spray
in
an
approximate
10
mph
wind
with
a
4
foot
release
height
at
an
application
rate
of
0.012
lbs
chlorsulfuron
per
acre.
The
toxicity
slope
for
cucumber
was
unavailable.
33
10
30
50
70
90
wheat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Ground:
Low
Boom,
Medium
Spray
Figure
12.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
a
ground
boom
application
conducted
with
a
medium
spray
in
an
approximate
10
mph
wind
with
a
2
foot
release
height
at
an
application
rate
of
0.012
lbs
chlorsulfuron
per
acre.
The
toxicity
slope
for
cucumber
was
unavailable.
34
10
30
50
70
90
wheat
tomato
sorghum
corn
pea
sugarbeet
soybean
rape
onion
0
100
200
300
400
500
600
700
800
900
1000
Percent
Effect
No­
Spray
Zone
(
ft)
Ground:
HIgh
Boom,
Medium
Spray
Figure
13.
Predicted
phytotoxicity
levels
and
associated
downwind
distances
from
a
ground
boom
application
conducted
with
a
medium
spray
in
an
approximate
10
mph
wind
with
a
4
foot
release
height
at
an
application
rate
of
0.012
lbs
chlorsulfuron
per
acre.
The
toxicity
slope
for
cucumber
was
unavailable.
35
Appendix
4.

Estimated
agricultural
usage
of
chlorsulfuron
from
the
US
Geological
Survey
(
http://
ca.
water.
usgs.
gov/
pnsp/
use92/
chlrsulf.
html):

Wind
speed
data
for
three
representative
cities
in
areas
where
chlorsulfuron
is
used
agriculturally.
Graphs
show
75th,
50th,
and
25th
percentile
wind
speeds
for
each
month.
Wind
speed
data
is
from
SAMSON
weather
monitoring
stations.

Yakima,
south
central
Washington:
36
Pendleton,
northwestern
Oregon:

North
Platte,
central
southwestern
Nebraska:
