UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
DP
Barcodes:
D307095
PC
Code:
080801
Date:
2/
11/
2005
SUBJECT:
Response
to
Error
 
only
Comments
on
Draft
EFED
RED
Chapter
for
Ametryn
TO:
Mark
Howard,
Chemical
Review
Manager
Reregistration
Division
FROM:
John
Ravenscroft,
Biologist
Kevin
Costello,
Geologist,
RAPL
Environmental
Risk
Branch
IV
Environmental
Fate
and
Effects
Division
(
7507C)

THRU:
Elizabeth
Behl,
Branch
Chief
Environmental
Risk
Branch
IV
Environmental
Fate
and
Effects
Division
(
7507C)

The
following
are
responses
to
comments
by
Syngenta
concerning
actual
or
perceived
errors
identified
in
the
draft
EFED
RED
chapter
for
ametryn.

Terrestrial
Animals
Comment:
The
time­
weighted
"
mean
residues"
for
terrestrial
exposure
were
calculated
incorrectly.

Response:
"
Mean
terrestrial
residues"
used
in
the
RED
chapter
were
not
time
weighted
averages,
but
peak
exposure
concentrations
obtained
using
the
mean
values
from
the
Kenaga
nomogram
for
each
food
group.
The
mean
residues
per
pound
of
pesticide
from
this
nomogram
are
85
ppm
for
short
grass,
36
ppm
for
tall
grass,
45
ppm
for
broadleaf
plants,
and
7
ppm
for
seeds.

Comment:
The
estimated
exposure
concentrations
for
crops
which
receive
different
application
rates
among
multiple
applications
cannot
be
calculated
with
the
ELL­
FATE
model.
­
2
­
Response:
The
variable
application
regimes
were
not
simulated
with
ELL­
FATE,
but
through
multiple
runs
of
the
FATE5
model
on
which
ELL­
FATE
is
based.
See
page
115
of
the
EFED
RED
chapter
for
further
details.
In
summary,
each
initial
application
was
modeled
with
FATE5,
and
the
residues
from
each
subsequent
application
were
added
to
residues
remaining
after
the
end
of
the
interval
between
applications.
The
resulting
peak
residues
were
then
used
for
risk
quotient
calculations.

Comment:
EFED
used
an
incorrect
conversion
to
derive
the
chronic
dietary
dose.

Response:
EFED
concurs
that
the
chronic
mammalian
risk
quotients
were
overestimated
due
to
use
of
an
incorrect
chronic
NOAEL.
This
error
has
been
identified
and
the
correct
values
for
chronic
mammalian
risk
quotients
have
been
entered
into
Table
30
of
the
RED
chapter.
The
recalculated
risk
quotients
used
the
chronic
mammalian
NOAEL
of
13
mg/
kg­
bw,
adjusting
for
15,
35
and
1000
g
weight
classes.
Additionally,
the
Kenaga
values
were
adjusted
for
percent
body­
weight
consumed
for
each
weight
class,
resulting
in
an
equivalent
dose
expected
environmental
concentration
(
EEC).
The
risk
quotients
were
calculated
by
dividing
the
equivalent
dose
EEC
values
by
the
adjusted
NOAELs.
The
recalculated
risk
quotients
still
suggest
a
chronic
risk
to
mammals
from
exposure
to
ametryn.

Terrestrial
Plants
Comment:
The
exposure
to
terrestrial
plants
appears
to
be
overestimated
in
the
draft
RED,
and
the
registrant
could
not
reproduce
the
EECs
used
in
the
risk
assessment.

Response:
EFED
concurs
that
the
terrestrial
plant
exposure
values
were
overestimated.
The
exposure
model
was
run
using
the
total
seasonal,
and
not
the
initial,
application
rate.
This
error
was
limited
to
the
sugarcane
uses.
These
scenarios
have
been
rerun
and
the
recalculated
values
for
EECs
and
risk
quotients
can
be
found
in
tables
16,
31
and
32
of
the
document.
The
risk
quotients
calculated
for
the
initial
applications
only
still
indicate
a
risk
to
terrestrial
plants,
and
do
not
reflect
the
potential
additional
risk
from
subsequent
applications.

Environmental
Fate
Comment:
The
source
of
the
84­
day
aerobic
soil­
metabolism
half­
life
for
ametryn
is
not
clear.
The
half­
life
reported
by
the
registrant
was
41
days.

Response:
The
half­
lives
of
84
and
91
days
for
ametryn
and
total
ametryn
residues,
respectively,
are
correct.
The
84­
day
half
life
is
consistent
with
the
EFED
review
of
December
23,
1991,
and
the
91­
day
half­
life
reflects
inclusion
of
major
degradates.
­
3
­
Comment:
Anaerobic
aquatic
metabolism
and
fish
bioaccumulation
studies
were
submitted
to
the
Agency,
but
parts
of
the
RED
chapter
report
data
gaps
for
these
guidelines.

Response:
The
document
has
been
revised
to
reflect
submission
of
these
studies.
