UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON
D.
C.,
20460
MEMORANDUM
PC
Code:
038901,
038904,
038905
DP
Barcode:
320971
SUBJECT:
Environmental
Fate
and
Effects
Division
Response
to
Public
Comment
for
the
Endothall
RED
FROM:
Michelle
Rau
Embry,
Ph.
D.
Environmental
Risk
Branch
II
Environmental
Fate
and
Effects
Division
(
7507C)

TO:
Mika
Hunter,
Chemical
Review
Manager
Reregistration
Division
(
7508C)

THROUGH:
Dana
Spatz,
RAPL
Tom
Bailey,
Ph.
D.,
Branch
Chief
Environmental
Risk
Branch
II
Environmental
Fate
and
Effects
Division
(
7507C)

DATE:
August
24,
2005
The
EFED
responses
to
the
public
comment
period
on
the
endothall
RED
are
addressed
below.

Cerexagri,
Inc.
Comments
­
Page
xxiv
(
24),
2.
Ecosystems
Potentially
at
Risk.
Risk
assessments
have
been
conducted
for
aquatic
plants
and
algae.
It
should
be
noted
that
endothall
is
an
aquatic
herbicide
and
algaecide
and
as
such
is
expected
to
kill
aquatic
plants
and
algae.
It
would
not
be
a
viable
product
if
it
were
not
efficacious.
The
Agency
understands
that
endothall
is
targeted
for
aquatic
plants.
The
statement
that
is
referred
to
in
the
comments
is
a
discussion
of
the
required
aquatic
toxicity
studies
to
assess
risk
to
aquatic
plant
species.

­
Page
xlvii
(
47),
c.
Aquatic
Application
of
Endothall.
Cerexagri
agrees
that
the
assumption
of
application
100%
of
a
pond
is
an
overestimation
of
the
EEC.
The
Agency
recognizes
that
the
assumption
of
100%
treated
areas
is
conservative
and
is
an
assumption
made
for
the
current
screening
level
risk
assessment.
However,
it
must
be
assumed
that
treatment
of
any
area
within
the
water
body
has
the
potential
to
affect
all
aquatic
species
in
that
water
body.
There
are
currently
no
available
behavioral
studies
that
demonstrate
avoidance
behavior
by
fish
or
other
aquatic
organisms,
and
therefore
such
exposure
avoidance
cannot
be
assumed.
­
Page
lii
(
52),
Table
15,
Summary
of
Endothall
Acute
and
Chronic
Aquatic
Toxicity
Data.
Cerexagri
is
willing
to
conduct
[
microcosm]
studies
to
assist
the
Agency
in
better
characterizing
the
risks
to
aquatic
species
associated
with
endothall
use
in
accordance
with
product
labels.
Microcosm
studies
submitted
to
the
Agency
by
Cerexagri
would
be
considered
in
future
endothall
ecological
risk
assessments.

­
Page
lxxi
(
71),
Aquatic
Plants
See
comment
above
(
Page
xxiv
(
24)).

Sonja
F.
Pascatore
Comments
a.
The
possibility
of
an
increase
(
as
much
as
160%)
in
concentration
after
treatment
is
an
unacceptable
risk
to
small
children
who
swim
in
shallow
water
and
are
at
risk
of
ingesting
ppm
greater
than
that
which
is
initially
injected.
Our
own
independent
lab
work
showed
7
ppm
in
water
which
was
supposed
to
have
no
more
than
2
ppm
immediately
after
treatment.

The
Agency
would
welcome
the
submission
of
independent
laboratory
work
on
aquatic
endothall
concentrations
following
treatment.
Additionally,
the
acceptable
level
of
2
ppm
that
is
referred
to
is
the
maximum
contaminant
level
(
MCL)
set
for
drinking
water
intakes,
not
for
general
water
concentrations
in
a
treated
water
body.
The
study
that
is
referenced
by
the
commentor
(
Yeo,
1970.
Dissipation
of
Endothall
and
Effects
on
Aquatic
Weeds
and
Fish.
Weed
Science,
18(
2):
282­
284)
refers
to
a
160%
increase
in
endothall
dissipation,
rather
than
concentration.
The
study
indicates
an
overall
decrease
in
endothall
concentrations
over
time.
Initial
concentrations
of
3
ppm
decreased
to
1.15
ppm
over
12
days
(
Table
3).

e.
Blue
gill
and
juvenile
and
adult
bass
were
greatly
reduced
in
this
endothall
treated
ponds
study.
This
in
an
unacceptable
risk
in
any
lake
where
the
fishery
is
a
mainstay
and
an
economic
necessity.

The
Agency
is
aware
of
the
fact
that
application
of
endothall
to
water
bodies
may
lead
to
fish
kills,
and
this
risk
is
addressed
in
the
ecological
risk
assessment.
