UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
OFFICE
OF
PREVENTION,
PESTICIDES,
AND
TOXIC
SUBSTANCES
WASHINGTON,
D.
C.
20460
June
06,
2003
MEMORANDUM
Subject:
Response
to
Comments
From
The
Bayer
Environmental
Science
on
Oxadiazon
Risk
Assessment
[
PC
Code
109001,
DP
Barcode
D290006]

From:
Seyed
Tadayon,
Chemist
Reregistration
Branch
III
Health
Effects
Division
7509C
Thru:
Cathy
Eiden,
Branch
Senior
Scientist
Reregistration
Branch
III
Health
Effect
Division
7509C
To:
Mark
Seaton,
Chemical
Review
Manager
Special
Review
and
Reregistration
Division
Mail
Code
7509C
The
purpose
of
this
document
is
to
address
the
comments
in
a
April
17,
2003
(
received
by
HED
May
06,
2003)
letter
from
Bayer
Environmental
Science
(
BES)
in
response
to
the
most
recent
Agency
risk
assessment
document
for
oxadiazon.

The
comments
from
this
submission
have
been
summarized
below
followed
by
the
Agency
response
to
each
specific
comment.
The
Bayer
letter
focused
on
different
areas
of
the
risk
assessment
process
such
as
the
drinking
water
intake,
occupational
risks
and
residential
risks.
This
document
addresses
only
those
comments
related
to
the
occupational
and
residential
aspects
of
the
risk
assessment.
BES
comment:

Page
5
provides
a
use
figure
on
golf
courses
of
77%
and
other
document
77%
or
65%
(
EFED
risk
assessment).
The
use
figures
should
be
harmonized
within
and
between
the
different
documents.

EPA
response:

This
error
has
been
corrected
in
the
revised
chapter.

BES
comment:

Page
8
provides
a
use
figure
on
golf
courses
of
71%
and
other
document
77%
or
65%
(
EFED
risk
assessment).
The
use
figures
should
be
harmonized
within
and
between
the
different
documents.

EPA
Response:

This
error
has
been
corrected
in
the
revised
chapter.

BES
comment:

Page
27,
Bayer
finds
this
statement
and
the
conclusion
to
be
confusing.
The
two
TTR
studies
(
MRID#
449955­
01
and
449955­
02)
were
apparently
not
accepted
by
EPA
because
they
used
the
modified
California
Roller
sampling
device
and
not
the
ORETF
device.
Bayer
refers
the
Agency
to
the
ORETF
submission
"
Evaluation
of
Transferable
Turf
Residue
Techniques
(
MRID#
4497203)
which
recommends
the
California
roller
as
the
ORETF
technique
for
conducting
TTR
studies.
Therefore,
why
were
the
studies
not
accepted
when
the
modified
California
Roller
technique
and
the
ORETF
Technique
are
identical
?
Bayer
is
also
concerned
about
the
statement
that
HED
does
not
considered
TTR
values
less
than
1%
of
the
application
rate
to
be
acceptable.
Granular
formulation
have
consistently
been
demonstrate
to
have
TTR
values
less
than
1%
of
the
application
rate.
This
statement
appears
to
relate
to
the
relationship
between
the
generic
residential
SOP
transfer
coefficients
of
14,500
cm2/
hr
and
8200
cm2/
hr
for
children
and
TTRs
less
than
1%
of
the
application
rate
(
HED
policy
12,
revised
22
February
2001).
Policy
12
states
that
the
revised
transfer
coefficients
should
not
be
used
with
TTRs
of
less
than
1%
of
the
application
rate.
Based
on
policy
12,
transfer
coefficients
of
43000
cm2/
hr
for
adults
and
8700
cm2/
hr
for
children
are
to
be
used
when
the
TTR
values
are
less
than
1%.
Therefore,
the
oxadiazon
TTR
studies
not
considered
to
be
acceptable
should
be
reevaluated
and
used
with
higher
transfer
coefficients
if
the
TTRs
are
less
than
1%.

EPA
response:

HED
agrees
that
the
California
roller
technique
is
the
most
efficient
of
all
the
measuring
techniques
to
collect
TTR
data.
However,
a
transfer
coefficient
(
TC)
measurement
should
be
taken
concurrently
with
the
TTR
measurement.
In
the
absence
of
a
concurrent
TC
measurement,
HED's
Expo
SAC
Policy
12
indicates
that
the
default
TC
values
and
5%
of
application
rate
for
TTR
should
be
used
to
estimate
short­
term
exposure.
In
the
submitted
Bayer
study,
the
TTR
values
measured
were
0.07%
of
application
rate
for
granular
and
0.15%
of
application
rate
for
liquid.
HED
Exposure
SAC
and
the
oxadiazon
ORE
RED
chapter
clearly
address
this
policy
issue.
That
is,
if
either
condition
applies:

1)
TTR
collected
via
California
roller
technique
in
absence
of
concurrent
TC
values,
and/
or
2)
TTR
values<
0.5%
of
application
rate
for
granular
and
<
1%
for
liquid
applications,

then
HED
uses
default
values
as
per
residential
SOP
(
Policy
12,
revised
22
February
2001)
for
conducting
exposure
assessment.

The
use
of
low
TTRs
with
the
current
transfer
coefficients
may
underestimate
dermal
exposure.
HED
further
reviewed
Science
Advisory
Council
Exposure
Policy
12
(
February
22,
2001)
and
concluded
that
transfer
coefficients
of
43000
cm2/
hr
for
adults
or
8700
cm2/
hr
for
children
have
been
changed
to
14,500
cm2/
hr
for
adults
and
5,200
cm2/
hr
for
children
(
1­
6
yrs)
in
the
current
revised
SOP
(
February
22,
2001).

BES
comment:

Page
33,
the
golf
course
transfer
coefficients
developed
concurrent
TTR
monitoring
using
the
modified
California
method.
Therefore
the
TTRs
obtained
from
the
submitted
Ronstar
WP
study
should
be
used
in
lieu
of
the
default
5%
value.

EPA
response:

The
submitted
study
(
MRID#
435178­
01)
measured
the
exposure
associated
with
Jazzercise
on
turf.
Jazzercise
actions
are
significantly
different
from
golfing
actions,
therefore,
it
is
not
appropriate
to
use
the
TTR
values
obtained
from
this
study
as
surrogate
data.
HED
used
the
standard
default
value
from
the
SOP.

BES
comment:

Page
35,
TTR
values
should
be
based
on
the
result
of
the
Ronstar
WP
study
and
not
the
default
values
of
5%.
Defaults
stated
in
the
residential
sops
are
to
be
used
only
in
the
absence
of
chemical­
specific
data.

EPA
response:

The
tables
on
pages
36
(
table
8),
37
(
table
9)
and
38
(
table
10)
of
the
risk
assessment
use
the
TTR
values
from
study
(
MRID#
435178­
01).
The
tables
also
show
the
risk
if
the
standard
default
value
is
used.
HED
typically
provides
a
range
of
risk
estimates
based
on
defaults
and
chemical
specific
data
to
SRRD,
if
required.
However,
risk
managers
base
their
final
decision
on
all
of
the
data
shown
for
these
scenarios.
BES
comment:

Page
38,
the
Information
in
this
table
should
be
verified.
Bayer
does
not
understand
how
the
percent
values
for
the
hand­
to­
mouth
activities
were
derived,
and
why
the
TTR
values
are
higher
for
the
exposure
from
irrigated
grass
than
the
one
for
the
non­
irrigated
grass,
while
the
TTR
based
on
study
MRID
43517801
indicates
the
reverse
situation.
Values
presented
in
Table
10
MRID
43517801
are
different
from
the
values
presented
in
the
revised
Occupational
and
Residential
Exposure
Assessment
document
page
28
provides
the
following
TTR
values
for
nonirrigated
and
the
irrigated
plots:
"
on
day
0,
the
highest
average
turf­
transferable
residues
(
TTR)
for
non­
irrigated
plots
was
1.22

g
per
cm2
and
0.694

g
per
cm2
on
irrigated
plot.".

EPA
Response:

The
turf­
transferable
residues
(
TTR)
values
indicated
in
page
28
of
Occupational
and
Residential
Exposure
Assessment
document
were
obtained
from
the
study
MRID
43517801.
This
study
was
conducted
with
3.0
lb
ai/
A.
In
Tables
8,
9
and
10
the
TTR
values
have
been
adjusted
to
reflect
the
label
rate
of
4.0
lb
ai/
A.
A
correction
has
been
made
to
Table
10
to
present
the
correct
TTR
values
for
irrigated
grass
versus
non­
irrigated
grass.
