UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
OFFICE
OF
PREVENTION,
PESTICIDES,
AND
TOXIC
SUBSTANCES
WASHINGTON,
D.
C.
20460
MEMORANDUM
DATE:
July
20,
2004
SUBJECT:
Response
to
Error
Only
Comments
from
2,4­
DB
Task
Force
PC
Codes:
030801
(
2,4­
DB)
and
030819
(
2,4­
DB­
DMA)
DP
Barcode:
D291200
TO:
Mika
Hunter,
Chemical
Review
Manager
Special
Review
Branch
Special
Review
and
Reregistration
Division
(
7508C)

FROM:
Kit
Farwell,
D.
V.
M.
Reregistration
Branch
1
Health
Effects
Division
(
7509C)

THRU:
Whang
Phang,
Ph.
D.,
Senior
Scientist
Reregistration
Branch
1
Health
Effects
Division
(
7509C)

The
2,4­
DB
Task
Force
made
recommendations
in
their
error
only
response
to
the
HED
risk
assessment
which
resulted
in
revisions
to
the
risk
assessment
and
disciplinary
chapters.
However,
several
recommendations
were
not
incorporated
into
the
risk
assessment
or
toxicology
chapter.
This
memo
explains
why
these
changes
were
not
adopted.
2,4­
DB
and
2,4­
DB
DMA
Human
Health
Risk
Assessment
Task
Force:
Page
1,
paragraph
5,
line
1
An
acute
dietary
endpoint
was
selected
for
females
13­
50
years
of
age
.
.
.

Here
the
age
range
is
13­
50;
in
other
discussions
and
tables,
the
age
range
is
13­
49.

HED
Response:
HIARC
reports
ages
13­
50
years,
the
DEEM
analyses
report
ages
13­
49
years.

Task
Force:
Page
4,
Table
1
Log
K
OW
for
2,4­
DB.
As
2,4­
DB
is
a
weak
acid
(
pK
a
=
4.8),
the
value
for
K
OW
is
not
independent
of
pH.
The
value
range
quoted
is
corrected
for
the
acid
partitioning
into
distilled
water;
the
exact
value
is
concentration
dependent.
However,
for
risk
assessment
purposes
the
value
for
log
K
OW
at
defined
pH
is
often
more
relevant.
The
2,4­
DB
Task
Force
will
provide
appropriate
Kow
values
during
the
public
comment
period.

HED
Response:
This
value
can
be
changed
if
the
Task
Force
submits
relevant
new
data.
This
new
information,
if
it
becomes
available,
will
not
change
any
of
the
conclusions
of
the
risk
assessment.

Task
Force:
Page
5,
paragraph
2
2,4­
DB
acid
IS
irritant
to
the
rabbit
eye
in
an
acute
study.

HED
Response:
The
paragraph
in
the
risk
assessment
correctly
compares
the
mild,
transient
eye
irritation
from
2,4­
DB
exposure
to
the
severe,
persistent
effects
from
2,4­
DB­
DMA
exposure.

No
change
to
the
risk
assessment
is
needed.

Task
Force:
Page
11,
new
paragraph
4,
insert
before
4.2.1
Suggest
the
following
paragraph
from
page
2
be
added:
The
HED
Metabolism
Committee
concluded
that
the
residue
to
be
regulated
in
plants
and
in
meat,
milk,
poultry
and
eggs
is
2,4­
DB
per
se,
and
that
2,4­
D
need
not
be
included
in
the
tolerance
expression
because
the
2,4­
D
metabolite
was
present
at
only
low
levels.

HED
Response:
This
explanation
is
already
present
on
page
12.

Task
Force:
Page
17,
paragraph
2,
lines
5
 
6
2,4­
D
acid
was
the
only
identifiable
degradate
in
the
photodegradation
in
water
and
the
aerobic
soil
metabolism
studies.
Correction
to
the
text
should
be
made
since
2,4­
D
has
never
been
identified
as
a
photodegradate
of
2,4­
DB
in
aqueous
systems.
It
has
been
identified
as
a
metabolite
under
aerobic/
anaerobic
soil
metabolism
conditions.
Suggested
text
follows:
2,4­
D
acid
has
been
identified
as
a
degradate
of
2,4­
DB
in
an
aerobic/
anaerobic
soil
metabolism
study.

HED
Response:

Task
Force:
Page
32,
Table
21
 
Product
Deficiencies
A.
H.
Marks
Generic
(
Task
Force)
data
were
supplied
for:
Color
(
Pesselman
1989
MRID
41460401)
Odor
(
Pesselman
1989
MRID
41402211)
pH
Value
(
Pesselman
1989
MRID
41402215)
and
Storage
Stability
(
Pesselman
and
Woosencraft
1989
MRID
41402216)

If
these
studies
are
regarded
as
deficient,
then
the
appropriate
DERs
would
be
appreciated
and
similar
requirements
should
be
made
for
other
Task
Force
members
quoting
these
data.

HED
Response:
These
data
and
reviews
will
be
evaluated
and
there
will
be
further
discussions
with
the
Task
Force
during
Phase
3.

Task
Force:
Page
33,
Tables
22
and
23
Acute
dermal
toxicity
of
>
2000
mg/
kg
should
be
assigned
Toxicity
Category
IV
not
III.

HED
Response:
The
limit
dose
for
an
acute
dermal
toxicity
study
is
2000
mg/
kg/
day
and
the
test
material
need
not
be
tested
at
higher
doses.
However,
toxicity
category
III
is
applied
to
test
material
with
an
LD50
value
ranging
from

2000
mg/
kg/
day
to
5000
mg/
kg/
day.
Toxicity
category
IV
is
applied
to
test
material
with
an
LD50
>
5000
mg/
kg/
day.

The
toxicity
category
is
correct
and
no
change
to
the
risk
assessment
is
needed.
SPECIFIC
COMMENTS
2,4­
DB
and
2,4­
DB­
DMA
Toxicology
Chapter
for
RED
Task
Force:
Table
of
Contents
The
following
additions
should
be
made
to
the
Table
of
Contents:
4.2.1
Carcinogenicity
Studies
in
Rats
and
Mice               
27
4.2.2
Classification
of
Carcinogenic
Potential               ..
28
HED
Response:
The
table
of
contents
in
the
chapter
is
correct.
No
changes
are
needed.

Task
Force:
Page
5,
Tables
2a
and
2b
The
Toxicity
Category
for
acute
dermal
exposures
is
given
as
Category
III.
As
in
each
case,
the
LD
50
exceeds
the
"
limit
test"
value
of
2000
mg/
kg,
this
should
be
Category
IV.

HED
Response:
The
limit
dose
for
an
acute
dermal
toxicity
study
is
2000
mg/
kg/
day
and
the
test
material
need
not
be
tested
at
higher
doses.
However,
toxicity
category
III
is
applied
to
test
material
with
an
LD50
value
ranging
from

2000
mg/
kg/
day
to
5000
mg/
kg/
day.
Toxicity
category
IV
is
applied
to
test
material
with
an
LD50
>
5000
mg/
kg/
day.

The
toxicity
category
is
correct
and
no
change
to
the
risk
assessment
is
needed.
SPECIFIC
COMMENTS
2,4­
DB
and
2,4­
DB
DMA
 
Report
of
the
Hazard
Identification
Assessment
Review
Committee
Task
Force:
Page
8,
paragraph
2
The
conversion
from
ppm
to
mg/
kg/
day
for
offspring
is
conservative.
In
studies
of
this
type
where
administration
is
via
incorporation
into
the
diet
at
a
fixed
rate,
dose
rate
inevitably
decreases
as
the
animals
mature.
Thus,
inspection
of
Tables
5.1a
and
5.1b
shows
that
for
the
first
week
post
weaning
intake
was
at
the
rate
of
approximately
55
mg/
kg/
day
and
43
mg/
kg/
day,
respectively.
This
is
in
excess
of
the
maximum
dose
rate
achieved
in
the
F
0
generation.
Nevertheless,
the
dose
rate
achieved
during
the
last
days
of
the
lactation
period,
when
the
pups
consume
a
significant
quantity
of
the
maternal
diet,
would
have
been
even
higher.
As
renal
excretion
of
the
phenoxy
acids
occurs
via
a
saturable
mechanism,
this
difference
can
be
significant
and
was
probably
the
major
contributing
factor
in
the
failure
to
continue
to
the
second
generation
at
the
high
dose.
This
should
be
acknowledged
by
the
insertion
of
"
at
least"
before
the
mean
dose
rates
quoted
in
the
paragraph.

HED
Response:
Doses
were
calculated
on
mean
test
substance
intake
and
were
not
calculated
by
converting
ppm
to
mg/
kg/
day.
No
changes
to
the
risk
assessment
are
needed.

Task
Force:
Page
4,
paragraphs
1
and
2,
line
1
Incorrect
MRID
numbers
for
developmental
rat
studies.

HED
Response:
The
numbers
were
corrected
in
the
toxicology
chapter.

Task
Force:
The
header
for
this
document
indicates
there
are
27
pages.
We
only
have
through
page
26
of
27.

HED
Response:
Page
27
only
has
a
records
number
used
by
the
archival
records
office.
