Document ID: EPA-HQ-OPP-2004-0382-0027
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-04-06T04:00Z

U.
S.
ENVIRONMENTAL
PROTECTION
AGENCY
Washington,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
Date:
February
17,
2006
Chemical:
Thiadizuron
PC
Code:
120301
DP
Barcode:
DP
324751
MEMORANDUM
SUBJECT:
Environmental
Fate
and
Effects
Division
Risk
Assessment
for
the
Reregistration
of
Thiadizuron.

TO:
John
Pates,
Chemical
Review
Manager,
Reregistration
Branch
II
Special
Review
and
Reregistration
Division
(
SRRD)
(
7508C)

FROM:
William
Evans,
Biologist
James
Hetrick,
Ph.
D.,
Senior
Physical
Scientist
Edward
Odenkirchen,
Ph.
D.,
Senior
Scientist
Nader
Elkassabany,
Acting
Branch
Chief
Environmental
Risk
Branch
I
Environmental
Fate
and
Effects
Division
(
7507C)

We
have
attached
our
responses
to
Bayer
CropScience's
December
16,
2005,
"
Response
to
the
Reregistration
Eligibility
Decision
(
RED)
and
Supporting
Risk
Assessments
&
Other
Related
Documents".
Our
responses
follow
the
Bayer
format
and
include
the
EPA
statement
and
the
Bayer's
comment
followed
by
the
EPA
response.
The
same
RED­
page
sequential
order
that
Bayer
used
is
followed
in
this
response,
the
page
numbers
to
which
Bayer
refers
may
not
necessarily
correspond
to
those
in
the
last
RED
revision.

It
should
be
noted
that
many
of
these
responses
have
previously
been
addressed
in
our
September
16,
2005
response
to
Bayer's
60­
day
Response
on
the
EFED
Science
Chapter
for
the
Reregistration
Eligibility
Decision
Document.
When
these
responses
have
already
been
addressed,
it
is
stated
under
the
appropriate
section
of
this
response.

Please
inform
Bayer
that
EFED
appreciates
the
comments
expressed
and
has
corrected
and
revised
the
document
as
appropriate.
Although
some
risk
quotients
have
changed,
we
are
pleased
to
report
that
the
errors
Bayer
detected
essentially
do
not
affect
the
risk
characterization
and
conclusions
we
reached
previously.
2
Executive
Summary
Page:
v
Paragraph
2
Lines:
6­
7
EPA
statement:
For
mammals
acute
risks
did
not
exceed
the
levels
of
concern,
but
there
is
a
potential
for
chronic
risk
when
maximum
(
high
end)
EEC's
are
assumed.
EPA
concludes
that
there
may
a
chronic
risk
to
mammals,
and
that
the
chronic
risk
to
birds
cannot
be
estimated
due
to
the
lack
of
data.

Bayer
comment:
While
the
screening
level
risk
assessment
may
indicate
a
potential
chronic
risk
to
mammals,
a
refined
analysis
indicates
that
this
risk
is
low.

The
screening
level
analysis
was
performed
using
the
maximum
potential
acute
exposure
to
compare
with
a
long­
term
chronic
toxicity
end­
point.
While
this
conservative
approach
may
be
appropriate
for
a
screening
level
assessment,
if
a
potential
risk
is
identified
further
analysis
should
be
conducted.
The
following
factors
should
be
considered
for
refined
assessment:

1.
When
the
mean
residue
(
exposure)
values
are
used,
which
represent
a
better
estimate
of
chronic
exposure
ALL
RQ's
were
below
the
Level
of
Concern
(
LOC),
indicating
a
low
risk
for
mammals.
The
lack
of
exceedences
with
the
mean
residue
values
was
noted
in
the
EFED
chapter
but
the
potential
interpretation
of
indicating
a
lower
risk
was
not.

2.
When
the
assessment
is
conducted
with
the
dietary
exposure
estimates,
ALL
RQ's
are
below
the
LOC,
indicating
a
low
risk
for
mammals.

3.
Potential
risk
for
mammals
can
be
examined
for
both
on­
target
(
within
the
cotton
field)
and
off­
site
(
outside
the
boundaries
of
the
field).
For
the
in­
field
assessment
it
is
unlikely
that
the
mammals
would
be
consuming
100%
of
their
diet
in
fully
treated
food
items,
particularly
with
a
potential
chronic
exposure.

a.
Cotton
plants,
particularly
late
in
the
season
are
not
a
primary
food
source
for
wild
mammals.

b.
The
nature
of
the
product
(
thidiazuron)
is
to
desiccate
and
defoliate
cotton
plant
leaves
within
14
days
of
application.
Prior
to
cotton
harvest
the
cotton
leaves
die,
dry
up,
fall
to
the
ground
and
decay
very
rapidly.
It
is
therefore
very
unlikely
that
treated
vegetation
would
be
used
as
a
food
item
in
the
fall
after
cotton
harvest.
Potential
chronic
exposure
is
further
mitigated
through
the
agronomic
practices
associated
with
cotton.
3
Typical
agricultural
practices
used
for
cotton
are
important
considerations
when
assessing
chronic
risk.
Thidiazuron
applications
are
made
at
the
end
of
the
cotton
growing
season
which
would
be
in
August
through
November
across
the
United
States.
Harvest
occurs
10
to
21
days
after
the
thidiazuron
applications;
from
August
to
early
December.
Once
harvest
is
complete,
typical
agricultural
practice
is
to
shred
and
destroy
the
remaining
cotton
plant
branches
and
root
structure
as
soon
as
possible.

This
cotton
transition,
from
application
to
harvest
to
a
fallow
field
and
finally
to
another
crop
is
driven
by
pest
management,
economic
and
weather
factors.
In
most
areas
of
the
country
the
cotton
farmers
immediately
disk
in
the
remaining
cotton
branches,
dead
leaves,
and
root
structure
to
a
depth
of
at
least
6­
inches.
This
process
ensures
that
bollworms
or
boll
weevils
do
not
over
winter
in
the
cotton
fields.
In
most
regions
of
the
country
this
pest
management
practice
is
mandated
by
law
to
prevent
bollworm
or
boll
weevil
infestations.
This
cotton
field
transition
also
allows
the
farmer
to
efficiently
and
effectively
prepare
the
soil
for
over
wintering
or
for
the
next
crop.
The
destruction
of
the
plant
and
preparation
of
the
field
is
completed
before
the
winter
rainy
season.
Since
the
cotton
plant
is
hardy
and
its
branches
and
root
structure
are
left
in
the
field
after
harvest,
it
is
to
the
farmer's
advantage
to
speed
up
the
degradation
of
the
shredded
plant
material
by
exposing
it
to
the
soil,
winter
rains
and
natural
weathering.

Typically
the
field
transition
is
completed
and
new
crop
is
planted
in
December
through
March.
The
next
crop
planted
may
be
cotton,
corn,
fall
vegetables,
soybeans
or
peanuts,
depending
upon
the
region
pf
the
country.
This
replanting
further
decreases
the
likelihood
of
contaminated
food
items
being
available
in
the
spring.

For
the
reasons
stated
above,
any
cotton
plant
debris
that
may
remain,
typically
a
few
bits
of
decaying
branches,
would
have
been
disked
into
the
soil
at
a
depth
of
6
inches
or
greater
long
before
the
spring.
These
physical
and
mechanical
farm
activities
such
as
leaf
desiccation,
plant
shredding
and
destruction,
and
soil
disking,
would
redistribute
thidiazuron
residues
in
the
soil.
These
practices
taken
together
with
the
potential
for
degradation
would
result
in
low
concentrations
in
the
soil.
In
conclusion,
it
is
unlikely
that
mammals
will
be
chronically
exposed
to
any
significant
residues
associated
with
the
cotton.

c.
The
potential
for
chronic
exposure
to
food
items
other
than
cotton
within
the
field
is
also
low.
According
to
Linders
et
al.
(
2002),
the
crop
interception
factor
for
cotton
during
stem
elongation/
crop
cover/
flowering
is
70%,
and
during
senescence
is
90%.
If
we
use
the
70%
as
a
conservative
estimate,
this
would
indicate
that
the
cotton
intercepts
at
least
70%
of
the
applied
4
thidiazuron.
Given
that
the
mammals
do
not
consume
the
cotton,
the
potential
exposure
on
other
food
items
within
the
field
will
be
significantly
lower
(
70%)
than
that
used
in
the
models
for
the
screening
level
risk
assessment.
The
small
mammals,
the
group
primarily
exceeding
the
risk
quotients
would
not
be
consuming
the
plant
material
receiving
the
high
deposition
of
thidiazuron
since
they
cannot
reach
this
part
of
the
plant.
The
plant
material
located
where
the
mammals
would
be
consuming
food
items
would
have
significantly
lower
residue
values
due
to
the
crop
interception.
If
we
reduce
the
exposure
estimates
by
70%,
none
of
the
scenarios
in
Table
1
would
exceed
the
chronic
LOC.
Additionally,
as
described
above,
the
cotton
plant
is
shredded
and
destroyed,
the
field
disked
to
a
soil
depth
of
6
inches,
which
would
significantly
decrease
the
potential
for
chronic
exposure
for
food
items
within
the
field.

For
the
off­
field
exposure,
the
off­
field
deposition
of
thidiazuron
would
be
significantly
lower
than
on­
field
thus
reducing
the
potential
risk
for
mammals.
The
AgDrift
(
ver
2.1)
spray
deposition
model
can
be
used
to
estimate
the
potential
deposition
to
wild
mammal
food
items.

Under
the
aerial
application
scenario,
assuming
medium
droplet
size
and
a
swath
displacement
(
industry
standard
practice
includes
a
swath
displacement)
of
0.37,
the
deposition
at
the
edge
of
the
field
would
be
less
than
one­
half
of
the
application
rate.
The
wild
mammal
risk
quotient
assuming
the
maximum
application
rate
being
directly
applied
to
potential
food
items
was
1.8.
Given
that
the
edge
of
field
deposition
is
less
than
half
the
maximum
application
rate,
the
risk
quotient
for
this
scenario
would
be
less
than
1,
indicating
a
low
risk
for
wild
mammals.

Under
the
ground
application
scenario
assuming
medium
to
course
droplet
size
and
a
high
boom
nozzle,
the
distance
from
the
edge
of
the
field
to
the
point
where
the
deposition
is
equal
to
one­
half
of
the
application
rate
is
3.5
feet.
This
area
is
small
and
demonstrates
that
it
is
unlikely
any
mammal
would
be
chronically
exposed
to
thidiazuron.
Additionally,
the
AgDrift
model
is
based
upon
deposition
rates
to
bare
ground.
Thidiazuron
application
to
fully
grown
cotton
would
significantly
decrease
the
deposition
off
the
field.
The
chronic
exposure
for
mammals
would
be
minimal
when
you
take
into
account
the
rapid
decrease
in
deposition
from
the
edge
of
the
field,
the
nearby
cotton
field
would
not
provide
chronic
exposure
(
see
above),
the
mammals
would
not
be
consuming
a
diet
with
100%
of
the
food
items
receiving
high
amounts
of
thidiazuron
exposure,
the
plant
(
crop)
interception
factors
for
plants
off­
field
also
lower
the
potential
exposure
to
food
items,
and
the
small
mammals
consume
plants
(
or
stems)
located
near
ground
(
they
cannot
reach
plants
(
or
plant
material)
that
receive
the
highest
deposition).
The
mean
residue
values
may
be
a
better
worst­
case
scenario
to
assess
potential
effects
off­
field,
and
these
RQ's
did
not
exceed
the
EPA
level
of
concern,
thus
indicating
a
low
risk
for
mammals.
5
EPA
response:
The
agency
believes
that
it
has
adequately
responded
to
the
registrant's
concern
in
the
September
16,
2005
response
to
Bayer's
60­
day
Response
on
the
EFED
Science
Chapter
for
the
Reregistration
Eligibility
Decision
Document.
Although
not
stated
in
the
Executive
Summary,
the
uncertainties
with
the
risk
as
well
as
the
conditions
that
under
which
the
risks
are
below
the
agency's
level
of
concern
(
LOC)
are
clearly
stated
and
characterized
in
the
EFED
science
chapter.

Page:
v
Paragraph
2
Lines:
8­
9
EPA
statement:
Chronic
risk
to
birds
cannot
be
estimated
due
to
absence
of
data;
however
such
data
will
be
required
as
a
follow­
up
to
this
RED.

Bayer's
comment:
The
RED
and
EFED
chapter
identified
a
potential
data
gap
for
thidiazuron,
avian
reproductive
studies.
It
is
the
position
of
Bayer
CropScience
that
avian
species
are
not
exposed
to
significant
thidiazuron
residues
on
a
chronic
basis,
and
that
these
studies
are
not
needed
to
assess
the
potential
risk
for
birds.
As
described
above,
thidiazuron
desiccates
and
defoliates
cotton
plant
leaves
within
14
days
of
application.
These
leaves
die,
dry
up,
fall
to
the
ground
and
decay
very
rapidly.
It
is
therefore
very
unlikely
that
treated
vegetation
would
be
used
as
an
avian
food
item
in
the
fall
after
cotton
harvest,
and
it
is
impossible
for
this
to
occur
during
the
following
spring
when
avian
breeding
recurs.
Any
food
items
obtained
the
following
spring
from
field
treated
with
thidiazuron
the
previous
year,
would
have
trace
concentrations
of
thidiazuron
and
would
not
pose
a
chronic
pr
reproductive
risk
to
birds.

As
noted
in
the
discussion
on
mammals,
the
typical
agricultural
practices
used
(
shredding
and
destroying
of
the
cotton
plant
and
disking
of
the
field)
for
cotton
clearly
demonstrate
the
low
potential
for
chronic
exposure
to
thidiazuron.
These
physical
and
mechanical
farm
activities
would
redistribute
thidiazuron
residues
in
the
soil.
Even
in
the
absence
of
any
chemical
degradation,
the
concentration
in
the
soil
would
be
low
and
not
present
a
hazard
to
breeding
birds.
Typically
the
field
transition
is
completed
and
new
crop
is
planted
in
December
through
March.
The
next
crop
planted
may
be
cotton,
corn,
fall
vegetables,
soybeans
or
peanuts,
depending
upon
the
region
pf
the
country.
This
replanting
further
decreases
the
likelihood
of
contaminated
avian
food
items
being
available
in
the
spring.

In
conclusion
birds
would
not
be
chronically
exposed
to
thidiazuron
and
the
risk
to
birds
is
minimal.
Furthermore
birds
would
not
be
chronically
exposed
to
thidiazuron
during
the
breeding
season,
and
at
a
minimum
a
few
months
may
elapse
before
the
breeding
season
began,
which
demonstrated
a
low
potential
for
chronic
exposure.
Thidiazuron
does
not
have
potential
to
bioaccumulate.
Toxicity
data
from
other
vertebrate
groups
indicate
a
low
level
of
toxicity.
An
avian
reproduction
study
has
long­
term
continuous
exposure
to
the
test
material,
which
6
not
realistic
for
the
thidiazuron
use
pattern.
Therefore
an
avian
reproduction
study
would
provide
minimal
value
for
the
risk
assessment.

EPA
Response:
EPA
believes
that
it
has
adequately
responded
to
the
uncertainties
of
chronic
avian
risk
due
to
the
lack
of
chronic
data
in
the
September
16,
2005
response
to
Bayer's
60­
day
Response
on
the
EFED
Science
Chapter
for
the
Reregistration
Eligibility
Decision
Document.

Environmental
Risk
Assessment
Environmental
Effects
Page:
16
Paragraph:
2
Lines:
1­
3
EPA
statement:
Acute
marine
invertebrate
studies
show
that
the
mysid
shrimp
and
the
eastern
oyster
embryo/
larvae
LC50s
are
3,240
and
5,384
ug
/
L,
and
NOAECs
are
1400
and
1.06
ug/
L,
respectively.

Bayer's
comment:
The
units
for
the
oyster
NOEC
are
incorrect.
The
NOEC
are
1.06
mg/
L
or
1060
ug/
L.

EPA
response:
The
registrant's
comment
is
correct
and
has
been
corrected
in
the
EFED
science
chapter.

Page:
21
Paragraph:
3
Lines:
1­
5
EPA
statement:
Aquatic
plants
do
not
appear
to
be
at
risk;
however,
semi­
aquatic
dicots,
not
monocots,
are
at
potential
direct
and
indirect
risk.
The
Agency
does
not
conduct
chronic
risk
assessments
for
plants.
Preliminary
data
indicate
that
there
may
be
potential
aquatic
plant
risks
from
the
photoproducts
of
thidiazuron.
The
Agency
intends
to
call
in
additional
data
in
order
to
assess
the
risk.

Bayer's
comment:
Green
algae
toxicity
values
are
available
for
the
photodegradates
and
demonstrate
that
these
degradates
are
no
more
toxic
than
the
parent
compound.
The
green
algae
has
the
lowest
toxicity
value
for
the
aquatic
plants
for
the
parent
(
EC50
>
150
ug/
L).
The
thidiazuron
photometabolite
AE
F132347
EC50
value
is
980
ug/
L
and
the
EC50
value
for
thidiazuron
photometabolite
AE
C421200
is
70000
ug/
L
(
see
page
94
of
the
EFED
chapter).
Therefore
no
additional
studies
are
needed
to
assess
the
risk
of
the
photometabolites.
7
EPA
response:
EFED
agrees
with
Bayer's
comments
and
is
unaware
of
this
statement
in
the
EFED
science
chapter.
EFED
will
work
with
SRRD
and
make
sure
that
this
statement
is
modified
or
deleted
in
the
Reregistration
Eligibility
Decision.

Line­
by­
Line
Review
of
the
Environmental
Fate
and
Effects
Division
Revised
Risk
Assessment
for
the
Reregistration
Eligibility
Decision
of
Thidiazuron
for
Use
on
Cotton
(
September
15,
2005)

Cover
Memorandum
for
EFED
Risk
Assessment
Ecological
Risk
Summary
Page:
3
Paragraph:
2
Bullet
2
for
mammals
EPA
statement:
Mammals
are
at
potential
chronic
risk.

Bayer's
comment:
See
Bayer
comments
for
the
RED
Executive
summary.

EPA
response:
See
EPA
response
for
the
RED
Executive
summary.

Page:
3
Paragraph:
2
Bullet
2
for
birds
EPA
statement:
Potential
chronic
risk
to
birds
cannot
be
determined
because
of
the
absence
of
chronic
data
Bayer's
comment:
See
Bayer
comments
for
the
RED
Executive
summary.

EPA
response:
See
EPA
response
for
the
RED
Executive
summary.

Page:
4
Paragraph:
2
na
EPA
statement:
EPA
provides
a
summary
of
the
mammalian
screening
level
risk
assessment.

Bayer's
comment:
See
Bayer
comments
for
the
RED
Executive
summary.
8
EPA
response:
See
EPA
response
for
the
RED
Executive
summary.

Page:
4
Paragraph:
3
na
EPA
statement:
The
second
generation
reproduction
study
with
rats
indicates
a
possible
concern
for
endocrine
disruption,
based
on
delayed
sexual
maturation
and
disruption
of
the
estrous
cycle.

Bayer's
comment:
EFED
mentioned
their
concern
that
the
effects
of
delayed
sexual
maturation
and
disruption
of
the
estrous
cycle
seen
in
the
2­
generation
reproduction
study
could
indicate
a
potential
for
endocrine
disruption
in
mammals
or
other
organisms.
When
looking
at
the
data
from
the
2­
generation
reproduction
study,
their
statement
that
there
was
delayed
sexual
maturation
is
based
on
the
occurrence
of
a
delay
in
vaginal
opening
in
F1
pups
at
the
high
dose
(
1200
ppm).
While
the
results
do
indicate
there
was
a
delay
in
the
time
to
vaginal
opening,
the
mean
body
weight
at
which
the
opening
occurred
was
similar
in
control
and
1200
ppm
groups.
Since
there
was
a
statistical
decrease
in
pup
body
weight
at
1200
ppm
starting
at
day
14
in
females,
it
suggests
the
delay
was
due
to
the
slower
rate
of
physical
development
in
these
animals
and
not
a
direct
effect
on
the
time
to
sexual
maturation.

This
occurrence
of
delayed
vaginal
opening
in
the
first
generation
(
F1)
pups
triggered
the
measurement
of
the
ano­
genital
distance
in
the
second
generation
(
F2)
pups
as
a
confirmatory
measure
because
vaginal
opening
and
ano­
genital
distance
are
both
hormonally
regulated.
The
results
show
there
was
no
effect
of
treatment
on
ano­
genital
distance
in
F2
pups.

The
data
also
shows
the
delay
in
vaginal
opening
had
no
effect
on
reproductive
viability
as
there
were
no
adverse
effects
on
any
of
the
mating
or
fertility
indices
in
the
second
generation.

In
summary,
an
assessment
of
the
2­
generation
reproduction
data
shows
that
while
there
was
a
clear
effect
on
vaginal
opening,
it
is
considered
to
be
related
to
the
reduced
rate
of
physical
development
of
the
animals
and
not
a
direct
effect
of
treatment
with
thidiazuron.
In
the
absence
of
confirmatory
data
to
indicate
any
adverse
effect
on
reproduction
or
reproductive
viability,
the
delayed
vaginal
opening
and
altered
estrous
cycle
in
F1
animals
are
not
considered
a
consequence
of
endocrine
disruption
by
thidiazuron
and
are
considered
to
be
of
no
long
term
biological
importance.
9
In
conclusion,
Bayer
CropScience
and
as
noted
in
the
RED
document
(
page
28)
the
weight
of
evidence
does
not
support
a
real
concern
for
endocrine
disruption
in
mammals.

EPA
response:
EPA
considers
the
occurrence
of
a
delay
in
vaginal
opening
in
F1
pups
a
direct
treatment
effect
from
the
use
of
thidiazuron
that
could
result
in
adverse
reproductive
effects.
Further
the
HED
science
chapter
notes
that
sub­
chronic
dietary
feeding
studies
in
rats
producted
epididymides
and
prostate
gland
weights,
small
prostate,
and
seminal
vesicles.(
NOAEL
=
34.5
mg/
kg­
bw).
In
addition,
microscopic
finding
observed
were
slight
to
mild
dimished
secretion
of
the
prostate
gland
and
slight
to
marked
diminished
secretion
of
the
seminal
vesicle.
Further,
a
carcinogenicity
study
in
mice
observed
epididymis
toxicity
including
increased
incidence
of
grossly
enlarged
epididymis
at
the
highest
dose
treated
in
mice
(
NOAEL
=
86
mg/
kg­
bw).
Therefore,
EFED
believes
that
ED
screening
is
warranted.

Data
Gaps
 
Ecological
Effects
­­
Non­
target
Terrestrial
Plant
Page:
5
Paragraph:
2
1
 
4
EPA
statement:
Definitive
tier
II
EC25'
s
and
NOAECs
are
lacking
for
the
vegetative
vigor
of
all
monocot
tested
and
for
the
seedling
emergence
of
two
monocots
tested;
this
is
because
the
test
concentrations
were
not
low
enough
to
establish
these
endpoints.

Bayer
comment:
As
noted
in
the
previous
comments
on
the
EFED
chapter,
this
statement
is
inaccurate
for
the
vegetative
vigor
test.
EPA
concurred
with
the
statement
in
regards
to
the
vegetative
vigor
test;
however
the
statement
was
not
changed.

EPA
response:
The
registrants
comment
is
correct.
The
paragraph
should
refer
only
to
the
seedling
emergence
test.
EFED
will
correct
this
statement
in
the
science
chapter.

Data
Gaps
 
Ecological
Effects
­­
Birds
Page:
6
Paragraph:
2
1
 
4
EPA
statement:
Chronic
risks
to
birds
can
not
be
quantitatively
evaluated
at
this
time
because
chronic
data
were
not
submitted.
In
order
to
assess
this
potential
risk,
we
recommend
chronic
testing
with
an
upland
game­
bird
species
(
bobwhite
quail)
and
a
waterfowl
(
mallard
duck).

Bayer's
comment:
See
Bayer
comments
for
the
RED
Executive
summary
10
EPA
response:
See
EPA
response
for
the
RED
Executive
summary.

Environmental
Fate
and
Effects
Division's
Risk
Assessment
for
the
Reregistration
Eligibility
Document
for
the
Use
of
Thidiazuron
on
Cotton
II.
Introduction
Uses
and
Use
Characterization
Page
7
Table
EPA
statement:
EPA
provides
a
list
of
current
products
containing
thidiazuron
and
their
corresponding
EPA
registration
numbers.

Bayer's
comment:
One
product
currently
registered
is
not
included
on
the
list:
Thidiazuron
Technical
Cotton
Defoliant,
EPA
Reg.
No.
264­
822
(
registration
granted
on
October
18,
2005).

EPA
response:
This
product
will
be
added
to
the
table
in
the
use
characterization
section,
however,
it
should
be
noted
that
this
registration
was
granted
after
the
RED
chapter
was
completed.

III.
Integrated
Environmental
Risk
Characterization
Risk
to
Birds
Chronic
Risk
to
Birds
Page
18
Paragraph:
4
Line:
1­
4
EPA
statement:
Chronic
risk
to
birds
cannot
be
quantitatively
evaluated
at
this
time
because
chronic
data
were
not
submitted.
However,
available
data
showing
that
chronic
levels
of
concern
for
mammals
are
exceeded
and
that
thidiazuron
is
persistent
in
the
field.
Suggest
that
there
is
also
potential
for
chronic
risk
to
birds
should
they
be
of
equal
or
greater
sensitivity
than
mammals.
11
Bayer's
comment:
See
Bayer
comments
for
the
RED
Executive
summary.

EPA
response:
See
EPA
response
for
the
RED
Executive
summary.

Endocrine
Disruption
Assessment
Page:
41
Paragraph:
4
Line
1­
6
EPA
statement:
The
2­
generation
reproduction
study
with
rats
indicates
the
potential
for
endocrine
disruption,
based
on
delayed
sexual
maturation
and
disruption
of
the
estrous
cycle.
The
reproductive
NOAEC
and
LOAEC
values
based
on
reduction
of
litter
size
are
400
and
1200
mg/
kg­
diet,
respectively.
The
measured
NOAEL
and
LOAEL
were
35.4
and
108.5
mg/
kg­
bw/
da,
respectively.
This
reproductive
effect
could
be
an
indicator
of
potential
endocrine
disruption
in
mammals
or
other
organisms.

Bayer's
comment:
See
Bayer
comments
for
page
4
of
the
EFED
chapter.

EPA
response:
See
EPA
response
for
Page
4,
Paragraph
3.

IV.
Environmental
Fate
Assessment
Physical/
Chemical
Properties
Page:
46
Table:
Physical
and
Chemical
Bayer's
comment:
The
study
assigned
MRID
45934001
which
is
listed
as
reference
for
most
of
the
physical
and
chemical
properties,
is
not
a
Bayer
CropScience
study.
For
guideline
830.7550,
the
MRID
number
listed
as
reference
should
be
corrected
to
413649­
06
EPA
response:
EFED
acknowledges
that
MRID
45934001
is
no
a
Bayer
CropScience
study.
The
MRID
number
for
guideline
830.7550
has
been
corrected
in
the
EFED
science
chapter.

V.
Aquatic
Hazard,
Exposure
and
Risk
Quotient
Calculation
Page:
54
Paragraph:
6
Line:
3­
4
12
EPA
statement:
The
LC50s
for
the
AC
F132345
metabolite
(
MRID
462035­
16)
and
the
AE
C421200
photodegradate
(
MRID
462035­
12)
were
>
98,000
g/
L.

Bayer's
comment:
The
unit
at
the
end
of
the
sentence
should
read
µ
g/
L,
as
opposed
to
g/
L
EPA
response:
EFED
agrees
with
Bayer's
comment,
however,
in
the
EFED
science
chapter
the
units
appear
as
ug/
L.
It
was
discovered
that
there
is
an
Object
Linkage
Error
(
OLE)
in
the
document,
and
the
document
may
not
recognize
the
correct
Greek
character
on
certain
PCs.