Closure
Conference
Call
for
Endothall
September
26,
2005
Purpose:
To
provide
an
overview
to
stakeholders
of
the
Agency's
reregistration
eligibility
and
resultant
risk
management
decisions
for
endothall
through
a
"
closure
conference
call."

The
intent
of
this
closure
conference
call
is
to
discuss
the
Agency's
risk
management
decisions
with
interested
stakeholders
and
registrants
prior
to
release
to
the
general
public.

Contacts:
Mika
Hunter
(
703)
308­
0041
and
Anne
Overstreet
(
703)
308­
8068
List
of
Invitees:
Cerexagri,
Inc.,
Army
Corps
of
Engineers,
USDA
I.
Background

Endothall
is
in
the
dicarboxylic
acid
class
of
chemicals
and
is
applied
as
either
a
dipotassium
salt
or
an
N,
N­
dimethylalkylamine
salt.
Although
endothall
acid
is
a
registered
form,
it
is
not
directly
applied
to
use
sites;
it
is
formed
as
a
break­
down
product
resulting
from
application
of
the
salt
forms.
The
amine
salt
is
the
only
form
applied
terrestrially,
while
both
the
dipotassium
and
amine
salt
are
applied
to
aquatic
use
sites.
The
amine
salt
is
also
used
to
control
algae
and
invasive
mollusks
in
cooling
towers.


Endothall
is
a
selective
contact
herbicide
which
works
by
interfering
with
plant
respiration,
affecting
protein
lipid
biosynthesis,
and
by
disrupting
plant
cell
membranes.


Endothall
is
used
as
an
aquatic
herbicide
to
control
submerged
aquatic
vegetation
and
algae
in
lakes,
ponds
and
irrigation
canals.
Endothall
is
also
used
as
a
desiccant
on
potatoes,
hops,
cotton,
clover,
and
alfalfa.

II.
Risk
Management
A.
Acute
Dietary
(
food
and
Water)


No
acute
endpoint
was
identified
for
acute
dietary
exposures
because
the
acute
toxicity
database
is
complete
and
does
not
suggest
there
is
a
potential
risk
concern.
Essentially,
the
available
data
suggests
that
a
single
exposure
to
endothall
does
not
result
in
an
effect
of
concern
for
risk
assessment
purposes.
Therefore,
the
Agency
does
not
expect
acute
risk
resulting
from
dietary
exposure
and
no
mitigation
measures
are
necessary.
B.
Chronic
Dietary
(
food
and
water)


Chronic
food
risks
are
below
the
Agency's
level
of
concern
for
the
general
population
(
3.5%
of
the
cPAD),
and
the
most
sensitive
population
subgroup,
children
1­
2
years
old
(
8.9%
of
the
cPAD).
No
mitigation
measures
are
necessary.
C.
Residential
Risks

For
residential
post­
application
scenarios,
exposures
on
the
day
of
application
after
an
application
to
a
public
water
body
are
of
greatest
concern.
They
Agency
identified
incidental
oral
exposure
(
from
swallowing
water
while
swimming)
as
a
possible
post­
application
exposure
scenario.
Margins
of
Concerns
(
MOEs)
were
calculated
using
the
SWIM
modeling
program
and
were
not
of
concern
to
the
Agency
(
MOE's
were
above
the
Agency's
target
of
100;
they
were
280
for
children
6­
10,
and
900
for
adults).


Although
the
Agency
did
not
identify
any
residential
use
scenarios
that
resulted
in
risk
of
concern,
the
following
statement
will
be
put
on
labels
addressing
residential
uses:
"
Consult
local
and
state
fish
and
game
agency
and
water
control
authorities
before
applying
this
product.
Permits
may
be
required
to
treat
such
water."

D.
Aggregate
Risks

For
short­
term
aggregate
exposure
(
for
adults),
the
Agency
aggregated
inhalation
exposure
during
residential
application
and
oral
exposure
during
swimming.
For
children,
only
oral
exposure
during
swimming
was
considered.
Acute
dietary
exposure
was
not
included
in
the
short­
term
aggregate
assessment
because
an
endpoint
attributable
to
a
single
dose
was
not
available.
MOE's
calculated
are
above
the
target
MOE
of
100,
with
values
of
271
for
children
and
ranging
from
156­
851
for
adults.
Therefore,
short­
term
aggregate
risks
are
not
of
concern
to
the
Agency
and
no
additional
mitigation
measures
are
necessary.


Because
the
Agency
does
not
expect
chronic
residential
exposure,
chronic
aggregate
risk
is
equal
to
chronic
dietary
risks
(
food
plus
water).
As
described
above,
these
risks
are
not
of
concern
to
the
Agency
and
no
additional
mitigation
measures
are
necessary.

E.
Occupational
Risks

Most
occupational
exposure
scenarios
are
not
of
concern
to
the
Agency.
However,
some
mitigation
is
required
to
protect
workers
when
mixing,
loading
and
applying
endothall.


For
mixing
and
loading
liquid
formulations
for
aerial
applications
to
terrestrial
sites
and
for
mixing,
loading
and
applying
liquid
formulations
for
aquatic
applications,
workers
must
wear
an
80%
(
PF5).


For
mixing,
loading
and
applying
granular
formulations
for
aquatic
uses,
workers
must
wear
a
90%
(
PF10
eslastomeric
half
face)
respirator
with
an
appropriate
cartridge.
Specific
label
language
will
include:


During
granular
applications,
the
respirator
need
not
be
worn,
provided
that
the
pesticide
is
applied
in
a
manner
(
such
as
aerial
application
or
subsurface
release
or
from
the
rear
of
a
vessel
that
is
moving
into
the
wind)
that
the
applicator
will
have
no
contact
with
the
pesticide.


During
liquid
applications,
the
respirator
need
not
be
worn,
provided
that
the
pesticide
is
applied
in
a
manner
(
such
as
direct
metering
or
subsurface
release
from
the
rear
of
a
vessel
that
is
moving
into
the
wind)
that
the
applicator
will
have
no
contact
with
the
pesticide.


The
Agency
has
determined
that
endothall
is
a
severe
dermal
irritant.
Label
requirements
addressing
dermal
effects
will
be
addressed
when
toxicity
data
is
submitted
for
end­
use
products.
The
Agency
require
personal
protective
equipment
based
on
end­
use
product
toxicity
during
product
reregistration.


To
protect
workers
from
exposures
during
post­
application
activities,
the
re­
entry
interval
of
48
hours
will
remain
for
agricultural
workers
(
terrestrial
applications).

F.
Environmental
Risks

The
Agency
has
consulted
both
the
registrants
and
stakeholders
to
identify
additional
label
language,
directions
for
use
and
usage
which
will
be
added
to
product
labels
to
reduce
potential
risks.


Dipotassium
salt:
The
Agency
is
requiring
that
labels
for
the
dipotassium
salt
form
of
endothall
specify
different
rates
for
different
size
applications.
The
following
statements
must
be
added
to
the
labels:
"
Only
use
higher
rates
when
making
treatments
to
small
areas
with
an
increased
potential
for
rapid
dilution
or
when
making
long
and
narrow
applications
such
as
for
boat
lanes
or
shoreline
treatments
where
dilution
may
reduce
the
exposure
of
plants
and
the
herbicide."
"
Use
lower
rates
for
large
contiguous
treatment
blocks
or
in
protected
areas
such
as
coves
where
reduced
water
movement
will
not
result
in
rapid
dilution
of
the
herbicide
from
the
target
treatment
area
or
when
treating
entire
lakes
or
ponds."


N,
N­
dimethylaklyamine
salt:
The
Agency
is
requiring
that
products
used
in
lakes,
ponds,
streams,
and
other
bodies
of
water
are
limited
to
applications
to
control
algae,
Hygrophila,
Vallisneria,
Hydrilla,
Cabomba,
bur
weed,
Elodea
Canadensis,
and
Brazilian
elodea.

III.
Tolerance
Reassessment
There
are
currently
seven
tolerances
established
for
endothall.
The
Agency
has
concluded
that
these
tolerances
meet
the
FQPA
safety
standards
and
that
the
aggregate
risks
from
combined
exposures
(
as
discussed
above)
are
not
of
concern
to
the
Agency.
A
summary
of
the
specific
tolerances
are
listed
below:


There
are
currently
five
tolerances
for
endothall
and
its
salts
listed
in
CFR
§
180.293(
a)(
1)
on
cotton
seed
(
0.1
ppm),
hops
(
0.1
ppm),
potato
(
0.1
ppm),
rice
grain
(
0.05
ppm),
and
rice
straw
(
0.05
ppm).
One
tolerance
is
listed
in
CFR
§
180.319
for
sugar
beets
(
0.2
ppm).


A
tolerance
is
currently
listed
for
potable
water
(
0.2
ppm,
CFR
§
180.293(
a)(
2).
The
Agency
is
proposing
that
this
tolerance
be
revoked.
Currently,
EPA's
Office
of
Water
has
an
MCL
established
for
endothall.

The
Agency
is
proposing
tolerances
for
cotton
gin
byproducts,
animal
commodities,
processed
commodities,
and
irrigated
crops.
When
acceptable
data
are
received
these
tolerances
will
be
established.


The
registrant
has
proposed
tolerances
for
fish
and
shellfish.
This
action
is
not
incorporated
into
this
document
and
will
be
addressed
in
a
separate
action.
However,
a
fresh
water
finfish
residue
level
of
0.1
ppm
was
included
in
the
dietary
exposure
assessment.
Current
food
consumption
models
cannot
include
residues
in
freshwater
shellfish
adequately;
so
freshwater
shellfish
were
not
incorporated
into
the
current
assessment,
and
were
considered
as
a
negligible
source
of
residues.

IV.
Outstanding
studies
Outstanding
studies
will
be
listed
in
the
RED.

V.
Conclusions
The
Agency
has
determined
that
endothall
is
eligible
for
rergistration
provided
that:


Additional
data
that
the
Agency
intends
to
require
to
confirm
this
decision;


The
risk
mitigation
measures
outlined
in
this
document
are
adopted;
and

Label
amendments
are
made
to
reflect
these
measures.
Closure
Call
Follow
Up
Wednesday
September
28,
2005
On
Wednesday
September
28,
2005
another
conference
call
was
held
with
Cerexagri
and
the
Army
Corp
of
Engineers.
The
reason
for
the
call
was
to
propose
setbacks
for
drinking
water
intakes.
The
registrant
agreed
that
600
foot
drinking
water
setbacks
are
appropriate
and
language
would
be
added
to
aquatic­
use
labels
specifying
these
setbacks.
