Document ID: EPA-HQ-OPP-2006-0292-0006
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-08-30T04:00Z

1
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
Chemical:
S­
metolachlor
PC
Code:
108800
DP
Barcode:
DP324973,
DP327861
MEMORANDUM
DATE:
May
31,
2006
SUBJECT:
Transmittal
Memo
for
the
Ecological
Risk
Assessment
for
the
Use
of
Smetolachlor
on
Pumpkins
and
Winter
Squash
(
IR­
4,
DP
324973)
and
on
Pumpkins
in
New
York
State
(
S18,
DP
327861)

FROM:
Paige
Doelling
Brown,
Ph.
D.,
Fisheries
Biologist
James
Hetrick,
Ph.
D.,
Senior
Chemist
Nancy
Andrews,
Ph.
D,
Branch
Chief
Environmental
Risk
Branch
1
Environmental
Fate
and
Effects
Division
(
7507P)

TO:
Joanne
Miller,
Product
Manager,
Herbicide
Branch
(
23)
Barbara
Madden,
Risk
Integration,
Minor
Use,
Emergency
Response
Branch
Daniel
Rosenblatt,
Team
Leader,
Emergency
Response
Team
Registration
Division
(
7507P)

Attached
is
the
Environmental
Fate
and
Effects
Division's
(
EFED)
ecological
risk
assessment
for
the
proposed
use
of
S­
metolachlor
(
PC
108800)
on
the
minor
crops
of
pumpkins
and
winter
squash
(
IR­
4,
DP
324973).
This
risk
assessment
also
applies
to
the
specific
exemption
request
for
use
on
pumpkins
in
New
York
(
S18,
327861),
as
the
rates
proposed
are
similar,
and
do
not
exceed
the
maximum
rate
evaluated
in
the
IR­
4
assessment.
2
S­
metolachlor
is
proposed
as
a
post­
plant,
pre­
emergence
herbicide,
applied
via
groundspray.
The
application
rate
is
1.0­
1.33
pt
formulated
product
per
acre
(
equivalent
to
0.95­
1.27
lb
ai/
A).
Actual
rate
is
dependent
on
percent
organic
matter
in
the
soil,
and
the
product
is
applied
once.
A
400­
ft
buffer
for
"
sensitive
plants"
is
included
in
the
current
label,
and
was
presumed
to
apply
to
the
proposed
crops.

Sufficient
fate
and
toxicity
data
were
available
to
conduct
a
screening
level
assessment.
Smetolachlor
(
PC
108800)
is
chemically
similar
to
metolachlor
(
PC
108801,
also
known
as
racemic
metolachlor),
but
is
a
separate
registration.
The
Agency
has
determined
that
the
environmental
fate
(
D23688)
and
ecotoxicity
data
(
D233184)
for
S­
metolachlor
are
comparable.
For
the
purpose
of
this
assessment,
data
for
S­
metolachlor
are
used
when
available,
and
gaps
are
filled
with
data
for
racemic
metolachlor.
Two
degradates,
metolachlor
ethane
sulfonic
acid
(
ESA)
and
metolachlor
oxanilic
acid
(
OA)
have
been
identified
as
potentially
of
toxicological
concern,
and
were
considered
in
the
assessment.

S­
metolachlor
is
a
chloroactanilide
herbicide,
classified
as
a
seedling
shoot
growth
inhibitor.
It
inhibits
biosynthesis
in
plants,
although
the
specific
biochemical
target
has
not
been
identified.
It
is
slightly
toxic
to
practically
nontoxic
to
birds,
and
moderately
toxic
to
fish.
OA
is
slightly
toxic
to
both
fish
and
aquatic
invertebrates.
ESA
is
slightly
toxic
to
fish,
and
practically
nontoxic
to
aquatic
invertebrates.
Neither
is
as
active
against
aquatic
or
terrestrial
plants
as
the
parent.
S­
metolachlor
is
persistent
and
highly
mobile
in
soil.
S­
metolachlor
and
the
major
degradates
OA
and
ESA
have
been
detected
in
surface
and
groundwater,
especially
in
the
Midwest,
where
it
is
used
extensively
for
corn.

Key
findings
of
this
assessment
include
 
S­
metolachlor
and
its
degradation
products
are
persistent
and
mobile
in
terrestrial
and
aquatic
environments.

 
Non­
target
organisms
most
at
risk
from
S­
metolachlor
use
are
terrestrial
plants
near
the
use
site(
s).
Non­
endangered
plant
and
endangered
plant
LOCs
are
exceeded
by
at
least
an
order
of
magnitude
and
sometimes
up
to
three
orders
of
magnitude
in
any
areas
receiving
runoff
alone
or
runoff
and
spray
drift
from
treated
fields
(
TerrPlant
modeling).

 
Based
on
spray
drift
alone,
risk
quotients
(
RQs)
for
plants
fall
below
the
non­
endangered
species
level
of
concern
(
LOC)
at
a
downwind
distance
from
the
treated
field
of
250­
300
ft
(
based
on
the
more
sensitive
seedling
emergence
endpoint).
This
potential
zone
of
impact
is
within
the
required
400­
ft
buffer
established
on
the
label
for
application
distances
from
sensitive
plants.
However,
the
endangered
plant
risk
LOC
is
still
exceeded
as
far
as
600
ft
away
from
the
application
point
(
AgDrift
Tier
I
modeling).

 
No
significant
effects
on
terrestrial
plants
are
expected
from
the
degradates
ESA
and
OA,
based
on
the
available
toxicity
data
and
estimated
environmental
concentrations
(
EECs).
3
 
Degradation
of
plant
communities
(
hedgerows,
wetlands,
riparian
corridors)
surrounding
the
treated
fields
could
have
effects
on
the
wildlife
residing
in
or
dependent
on
them.

 
Both
non­
endangered
plant
and
endangered
plant
risk
LOCs
were
exceeded
for
freshwater
vascular
plants,
freshwater
non­
vascular
plants,
and
saltwater
plants.
Currently,
there
are
no
listed
non­
vascular
aquatic
plant
species.
Listed
aquatic
vascular
plants
are
reported
with
terrestrial
plants
in
the
endangered
species
appendix.

 
Use
of
S­
metolachlor
could
reduce
primary
productivity
in
aquatic
systems
located
near
the
use
site.
The
importance
of
primary
productivity
occurring
within
a
given
ecosystem
varies
widely.
However,
differential
selection
pressure
for
algal
species
could
have
cascading
effects
up
the
food
chain
and/
or
may
affect
community
composition.

 
There
were
no
acute
risk
or
chronic
risk
concerns
for
direct
effects
to
non­
endangered
birds.
However,
acute
endangered
species
LOCs
for
small
insectivorous
and
herbivorous
birds
were
exceeded
at
the
higher
application
rate
(
1.27
lb
ai/
A).
Acute
endangered
species
LOCs
for
small
herbivorous
birds
were
exceeded
at
the
lower
application
rate
(
0.95
lb
ai/
A).

 
There
were
no
non­
endangered
or
endangered
species
acute
risk
concerns
for
small
mammals
based
on
the
conditions
modeled.
Chronic
risk
LOCs
for
mammals
were
exceeded
in
some
situations
evaluated.
Chronic
effects
noted
in
guideline
studies
include
reduced
survivability
of
offspring.

 
There
were
no
risk
concerns
for
acute
or
chronic
direct
effects
to
endangered
or
nonendangered
aquatic
animals
in
freshwater
or
saltwater
environments.
4
Endangered
Species
 
Endangered
species
taxa
potentially
affected
by
the
proposed
use
of
S­
metolachlor
on
pumpkins
and
winter
squash
include
plants,
amphibians,
birds,
reptiles,
and
mammals.
Table
1
shows
the
possible
direct
and
indirect
effects
for
various
taxa,
as
well
as
the
number
of
species
identified
as
occurring
in
the
same
counties
as
the
proposed
crops.

Table
1
Endangered
Species
Summary
Evaluation
Organism
LOCATES
Category
(#
of
species)
Direct
Effects
Indirect
Effects
Monocots
(
61)
Monocots
Other
1
(
22)

Dicots
Dicots
(
576)
Yes
Effects
at
both
proposed
application
rates
of
1.33
and
1.0
pt/
A
2
Possible
Effects
on
birds
or
mammals
could
affect
pollinator
or
dispersal
species
Birds
(
26)
Reptiles
(
8)

Birds
Terrestrial
Phase
Amphibians
(
18)
Yes
Acute
effects,
herbivores
and
insectivores,
small
size
class,
at
1.33
and
1.0
pt/
A
2
Mammals
Mammals
(
12)
Yes
Chronic
effects,
herbivores
and
invertivores,
all
size
classes,
at
1.33
and
1.0
pt/
A
2
Possible
Modification
of
plant
community
could
affect
food
and
shelter
FW
Aquatic
Plants
FW
Aquatic
Plants
3
Yes
LOC
exceedences
for
both
algae
and
vascular
plants
SW
Aquatic
Plants
SW
Aquatic
Plants
3
Yes
LOC
exceedences
Possible
Modification
of
primary
productivity
in
the
system
could
affect
survival
or
fecundity
of
individuals.
Modification
of
riparian
vegetation
could
affect
water
temperature,
allochthonous
input,
sedimentation,
or
bank
stability
1
Cycads,
Conifers,
Fern
Allies.
These
genera
have
no
direct
corollary
test
organism,
and
have
been
evaluated
based
on
the
most
sensitive
plant
endpoint.
2
formulated
product
3
Number
of
species
affected
included
in
count
of
monocots
and
dicots
5
Data
Requirements
No
specific
toxicity
studies
are
required,
although
providing
the
following
toxicity
studies
to
the
Agency
may
reduce
uncertainty
in
the
risk
assessment.

 
No
valid
S­
metolachlor
guideline
studies
on
saltwater
animals
(
fish
(
72­
3a)
or
invertebrates
(
72­
3b,
72­
3c)
were
available.
Gaps
were
filled
with
data
on
racemic
metolachlor.
New
data
are
not
expected
to
change
risk
conclusions.

 
The
avian
oral
studies
(
71­
4)
and
avian
dietary
studies
(
71­
2)
only
establish
a
greater
than
value
for
the
LC50.
While
RQs
generated
using
this
value
do
not
approach
the
non­
endangered
species
acute
risk
LOCs,
the
dose­
based
RQs
generated
from
the
oral
study
may
exceed
the
endangered
species
acute
risk
LOC
for
small
birds.
Additional
data
may
or
may
not
reduce
uncertainty
in
this
portion
of
the
assessment.
The
oral
study
would
have
to
establish
an
LC50
of
approximately
3500
mg/
kg
bw
to
clear
all
LOCs.