UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
PC
Codes:
029801,
029802,
029806,
128931,
128944,
129043
DP
Barcode:
none
April
12,
2006
MEMORANDUM
Subject:
EFED
Response
to
Public
Comments
on
RED
Chapter
For
Dicamba/
Dicamba
Salts
To:
Susan
Lewis,
Branch
Chief
Kendra
Tyler,
RM
Reviewer
Reregistration
Branch
1
Special
Review
and
Reregistration
Division
From:
Bill
Erickson,
Biologist
[
signed]
Ibrahim
Abdel­
Saheb,
Environmental
Scientist
[
signed]
Environmental
Risk
Branch
2
Environmental
Fate
and
Effects
Division
Through:
Thomas
Bailey,
Branch
Chief
[
signed]
Environmental
Risk
Branch
2
Environmental
Fate
and
Effects
Division
EFED
has
reviewed
the
public
comments
on
the
revised
RED
chapter
for
dicamba
and
its
salts.
Below
is
EFED's
response
to
those
comments
that
apply
to
the
environmental
risk
assessment.

BASF
Comment:
BASF
acknowledges
that
the
current
EPA
database
for
potential
nontarget
terrestrial
plant
toxicity
of
dicamba
is
limited
but
notes
that
other
data
requirements
have
been
fulfilled.

EFED
Response:
EFED
addressed
this
comment
in
our
November
15,
2005
response
to
the
errors­
only
comments
of
BASF.
Again,
we
refer
BASF
to
Appendix
E
of
the
risk
assessment,
which
lists
the
status
of
the
data
requirements.
The
following
data
gaps
exist:

°
seedling
emergence
and
vegetative
vigor
studies
(
123­
1a,
b);
dicamba
acid,
TEP
°
seedling
emergence
and
vegetative
vigor
studies
(
123­
1a,
b);
dimethylamine
salt,
TEP
°
seedling
emergence
and
vegetative
vigor
studies
(
123­
1a,
b);
diglycoamine
salt,
TEP
°
seedling
emergence
and
vegetative
vigor
studies
(
123­
1a,
b);
isopropylamine
salt,
TEP
°
seedling
emergence
and
vegetative
vigor
studies
(
123­
1a,
b);
sodium
salt,
TEP
°
seedling
emergence
and
vegetative
vigor
studies
(
123­
1a,
b);
potassium
salt,
TEP
BASF
Comment:
Current
guideline
requirements
for
terrestrial
non­
target
plant
studies
are
to
be
conducted
on
the
formulated
product.
BASF
references
MRID
42846301.

EFED
Response:
BASF
is
correct
in
noting
that
terrestrial
non­
target
plant
studies
are
to
be
conducted
using
formulated
product.
As
specified
above
in
EFED's
response
to
the
first
comment
of
BASF,
the
outstanding
plant
studies
are
to
be
conducted
using
a
typical
end
use
product
(
TEP)
for
each
active
ingredient.
Regarding
the
seedling
emergence
and
vegetative
vigor
tests
submitted
under
MRID
42846301,
both
tests
were
conducted
with
technical
dicamba
(
89.5%
ai),
not
a
TEP.

BASF
Comment:
BASF
questions
why
EFED
reported
mammalian
chronic
RQs
based
on
dietary
data
in
the
draft
risk
assessment
but
not
in
the
revised
risk
assessment
where
dose­
based
RQs
were
reported.
BASF
also
questions
EFED's
justification
for
the
differences
in
dietary
RQs
as
compared
to
dose­
based
RQs.

EFED
Response:
A
change
in
the
mammalian
chronic
RQs
was
made
in
the
revised
assessment.
As
BASF
correctly
reported
in
their
errors­
only
comments,
the
wrong
units
were
used
in
the
original
computations.
The
reported
45
mg/
kg
is
actually
a
dose­
based
value,
not
a
dietary
value.
Therefore,
EFED
recomputed
the
values,
and
the
dose­
based
RQs
reported
in
the
revised
assessment
are
appropriate.
Dose­
based
RQs
can
differ
markedly
from
dietary
RQs.
Dietary
RQs
are
simply
based
on
the
amount
of
active
ingredient
in
the
food.
The
dose­
based
values
are
determined
based
on
the
amount
of
active
ingredient
in
the
food
but
also
on
the
amount
of
food
eaten
and
are
also
scaled
to
three
body
sizes
(
15
g,
35
g,
and
1000
g).

BASF
Comment:
BASF
agrees
that
if
representative
monitoring
data
were
not
available,
then
the
modeling
methods
used
by
EFED
must
be
employed.
BASF
strongly
asserts,
however,
that
is
not
the
case
for
dicamba.
The
data
below
is
presented
in
support
of
our
position.
First,
the
Agency
has
commented
that
they
are
unable
to
know
if
monitoring
results
are
from
regions
where
the
product
has
been
used.
Therefore,
in
order
to
address
this
concern,
BASF
has
obtained
use
data
from
DMR
and
presented
it
as
a
GIS
projection
with
the
monitoring
sites
(
Figure
A1).
The
NAWQA
surface
monitoring
basins,
surface
water
and
ground
water
monitoring
locations
are
presented
in
conjunction
with
Dicamba
sales
data
from
2000­
2004
from
DMR.
This
perspective
on
the
validity
of
monitoring
locations
demonstrates
that
the
product
has
been
used
in
all
of
the
monitoring
areas.
Since
dicamba
is
a
very
widely
used
product
and
the
NAWQA
data
cover
numerous
and
geographically
diverse
sites,
we
believe
that
the
NAWQA
data
are
descriptive
and
of
high
quantity
for
understanding
the
magnitude
and
frequency
of
residues
in
water.
The
data
set
is
also
adequate
in
our
view
because
data
collection
started
in
1993
and
has
continued
up
to
as
recently
as
December
2003.

EFED
Response:
Even
when
the
DMR
data
was
used
(
Figure
A1
in
BASF
response);
it
appears
that
areas
with
high
use
of
dicamba;
surface
and
groundwater
have
not
been
monitored
at
all
(
e.
g.
California;
areas
in
Red
on
Figure
A1);
or
with
single
monitoring
sites
in
areas
such
as
North
and
South
Dakota.
Thus;
these
data
do
not
appear
to
be
spatially
correlated
with
the
high
use
areas
of
dicamba.
In
addition,
NAWQA
data
is
not
targeted
specifically
to
dicamba,
and
therefore
it
is
likely
that
high
concentrations
of
dicamba
(
peaks)
were
missed
in
such
monitoring.
Therefore,
EFED
still
believes
that
at
the
absence
of
a
targeted
monitoring
data,
the
use
of
modeling
results
for
surface
and
water
would
be
more
appropriate."

BASF
Comment:
Next,
in
a
recent
publication
in
the
Journal
of
Agricultural
Food
and
Chemistry,
a
persuasive
presentation
of
data
is
given
that
illustrates
the
differences
between
monitoring
data
and
modeling.
The
authors
describe
how
modeling
methods,
such
as
those
used
by
EFED,
drastically
over
estimate
exposure
in
drinking
water
systems.
The
paper
specifically
compares
dicamba
model
predictions
to
the
monitoring
data.
These
comparisons
indicate
that
model
predictions
can
range
as
high
as
6
orders
of
magnitude
greater
than
monitoring
results!
Therefore,
BASF
believes
it
to
be
scientifically
accurate
to
use
the
monitoring
data
where
this
information
is
available.

EFED
Response:
The
basis
of
the
comparison
made
in
this
article
is
fundamentally
flawed.
The
endpoints
derived
from
EFED
modeling
and
the
reported
monitoring
results
are
wholly
different.
For
the
conclusions
presented
in
this
article
to
be
valid,
the
authors
would
have
needed
to
demonstrate
that
the
monitoring
data
used
for
the
comparisons
represented
the
full
range
of
use
conditions
for
each
of
the
pesticides
used
in
the
comparison.
The
paper
did
not
provide
adequate
detail
about
(
1)
the
differences
in
the
endpoints
for
modeling
and
monitoring,
(
2)
the
assumptions
and
inputs
used
in
modeling,
or
(
3)
the
design
of
the
monitoring
study.
It
did
not
describe
the
nature
of
the
EPA
models,
or
how
these
models
are
used.
These
details
are
important
in
interpretation
of
results,
in
supporting
both
the
author's
recommendations
to
develop
adjustment
factors,
and
the
author's
judgment
on
the
validity
of
the
conceptual
model.
Additionally,
the
author's
description
of
how
EPA's
endpoints
are
derived
was
inadequate.
Application
rates,
application
frequencies,
and
percentage
cropped
area
adjustment
factors
used
in
modeling
should
have
closely
represented
actual
pesticide
use
and
usage
in
each
of
the
12
watersheds
monitored.
This
could
not
be
determined
because
the
authors
had
not
provided
the
information
necessary
to
interpret
monitoring
study
results.
The
study
authors
failed
to
compare
a
representative
monitoring
dataset
to
the
screening
model
estimates,
did
not
design
the
monitoring
to
capture
a
maximum
concentration
from
a
large
rainfall
event,
and
did
not
provide
details
of
pesticide
usage
in
the
watershed.
As
a
result,
statistical
analysis
of
the
data
cannot
provide
meaningful
results.
Given
the
flaws
in
the
overall
methodology
used
for
comparison,
the
adjustment
factor
development
has
no
basis,
and
conclusions
about
the
adequacy
of
EPA's
conceptual
model
for
water
modeling
is
not
supported
by
the
published
analysis.

BASF
Comment:
We
believe
that
the
BASF
guideline
data
are
sufficient
to
A)
Know
the
mechanistic
environmental
fate
behavior
of
dicamba
in
terrestrial
environments.
We
also
believe
that
the
NAWQA
data
are
sufficient
to
B)
know
the
magnitude
and
frequency
of
residues
in
ground
water
and
surface
water.
The
USGS
NAWQA
program
has
been
collecting
data
on
dicamba
residues
in
ground
water
and
now
has
measured
over
4,700
ground
water
samples
for
the
active
ingredient.
The
magnitude
and
frequency
of
dicamba
detects
found
in
ground
water
from
the
NAWQA
program
can
be
seen.
Refer
to
Figure
A3.
Therefore,
BASF
believes
that
NO
ADDITIONAL
DATA
IS
NEEDED
regarding
Series
166­
1
and
166­
2.

EFED
Response:
EFED
agrees.

SF
Environment
Comment:
No
assessments
were
done
for
granular
formulations,
which
are
the
leading
formulation
for
consumer
use.
Although
consumer
formulations
may
have
relatively
low
dicamba
application
rates
due
to
the
presence
of
other
active
ingredients
in
the
products,
the
risk
may
be
increased
by
birds
ingesting
pellets
directly.
The
risk
may
also
be
increased
by
the
presence
of
other
active
ingredients
with
common
modes
of
toxicity.
We
request
that
EPA
assess
avian
risks
from
granular
products.

EFED
Response:
EFED
agrees
that
granular
products
may
pose
a
risk
to
birds,
and
more
than
120
granular
"
weed
and
feed"
products
are
registered
for
use
on
lawns
and
other
turf,
including
golf
courses.
As
SF
Environment
states,
most
products
also
contain
one
or
more
other
active
ingredients
(
e.
g.,
2,4­
D,
propionic
acid,
benflualin,
sulfentrazon,
MCPA,
chlorflurenol).
Most
products
are
applied
in
spring
or
early
fall
when
weeds
are
actively
growing,
and
repeat
applications
may
be
made
for
some
products.
Birds
might
ingest
granules
either
intentionally
(
e.
g.,
source
of
grit)
or
inadvertently
(
e.
g.,
granules
adhering
to
earthworms
or
other
foods).
EFED
has
examined
the
labels
for
several
representative
products
and
calculated
the
risk
quotients
(
RQs)
tabulated
below.
These
RQs
are
for
a
single
application
and
only
for
the
dicamba
component
of
the
product.
As
SF
Environment
notes,
and
EFED
concurs
with,
other
active
ingredients
in
the
product
may
augment
risk,
because
each
granule
ingested
contains
all
active
ingredients
in
the
product.
This
is
a
major
uncertainty
in
assessing
the
risk
of
these
granular
weed
and
feed
products.

EFED's
TREX
model
(
version
1.2.3)
was
used
to
calculate
the
avian
and
mammalian
acute
RQs,
based
on
the
number
of
dicamba
LD50'
s
per
square
foot
in
a
single
application.
Those
RQs
that
exceed
the
Level
of
Concern
(
LOC
=
0.1
for
listed
(
i.
e.,
federally
endangered
and
threatened)
species,
0.5
for
nonlisted
species)
are
highlighted
in
bold.
Acute
LOCs
are
exceeded
for
listed
and
nonlisted
birds,
especially
for
application
rates
used
on
golf
courses.
Repeat
applications
are
likely
to
add
to
this
risk.
A
single
application
on
golf­
course
turf
also
exceeds
the
acute
LOC
for
listed
mammals.
EFED
has
no
scenario
for
assessing
chronic
risk
for
granular
products.
RQs
for
a
single
application
(
dicamba
component
only)

dicamba
(%
ai)
appl.
rate
(
lb
ai/
A)
mg
ai
dicamba/
ft2
RQ
by
taxa/
weight
class
other
active
ingredients
in
product
Andersons
Golf
Products
KOG
Weed
Control
(
EPA
Reg.
no.
9198­
184)

0.70
1.96
(
high
rate)
20.41
avian:
none
20
g
100
g
1000
g
7.53
1.18
0.08
mammal:

15
g
100
g
1000
g
0.23
0.12
0.01
0.98
(
medium
rate)
10.20
avian:

20
g
100
g
1000
g
3.77
0.59
0.04
mammal:

15
g
100
g
1000
g
0.11
0.06
<
0.01
note:
may
repeat
at
6­
mo.
intervals
for
2­
3
applications
Riverdale
Millenium
(
EPA
Reg.
no.
228­
344)

0.171
(
salt)
0.29
3.02
avian:
2,4­
D,
dimethylamine
salt
(
1.381%)
monoethanolamine
salt
of
3,6­
dichloro­
2­
pyridinecarbolic
acid
(
0.187%)
20
g
100
g
1000
g
1.11
0.18
0.01
mammal:

15
g
100
g
1000
g
0.03
0.02
<
0.01
dicamba
(%
ai)
appl.
rate
(
lb
ai/
A)
mg
ai
dicamba/
ft2
RQ
by
taxa/
weight
class
other
active
ingredients
in
product
EH­
1355
Weed
and
Feed
(
EPA
Reg.
no.
2217­
822)
Riverdale
Sweet
Sixteen
(
EPA
Reg.
no.
228­
344)

0.08
0.1115
1.16
avian:
EH­
1355:
acetic
acid
(
0.82%)
propionic
acid
(
0.16%)

Riverdale
Sweet
Sixteen:
acetic
acid
(
0.82%)
mecoprop
(
0.165%)
20
g
100
g
1000
g
0.43
0.07
<
0.01
mammal:

15
g
100
g
1000
g
0.01
0.01
<
0.01
EH­
1415
Weed
and
Feed
(
EPA
Reg.
no.
2217­
883)

0.073
0.1
1.04
avian:
2,4­
D,
2­
ethylhexyl
ester
(
1.153%)
mecoprop­
p
acid
(
0.174%)
sulfentrazone
(
0.034%)
20
g
100
g
1000
g
0.38
0.06
<
0.01
mammal:

15
g
100
g
1000
g
0.01
0.01
<
0.01
note:
a
second
application
can
be
made
after
30
days
RD
1646
(
EPA
Reg.
no.
71995­
43)

0.09
0.125
avian:
2,4­
D,
isooctyl
ester
(
1.346%)
2,4­
D
(
0.182%)
mecoprop­
p
(
0.359%)
20
g
100
g
1000
g
0.48
0.08
0.01
mammal:

15
g
100
g
1000
g
0.01
0.01
<
0.01
