UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON
D.
C.,
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
PC
Code:
128840,
128848,
129023
DP
Barcode:
D313182
Date:
Sep
27,
2005
MEMORANDUM
SUBJECT:
Amendment
to
Drinking
Water
Assessment
for
Imazaquin
and
its
Salts
TO:
Catherine
Eiden,
Branch
Chief
Susan
Stanton,
Risk
Assessor
Registration
Action
Branch
III
(
7509C)
Health
Effects
Division
Craig
Doty,
Chemical
Review
Manager
Special
Review
Branch
Special
Review
and
Registration
Division
(
7508C)

FROM:
Keara
Moore,
Environmental
Scientist
Environmental
Risk
Branch
III
Environmental
Fate
and
Effects
Division
(
7507C)

THRU:
Daniel
Rieder,
Branch
Chief
Environmental
Risk
Branch
III
Environmental
Fate
and
Effects
Division
(
7507C)

The
original
drinking
water
assessment
for
imazaquin
(
DP
Barcode
313182,
6/
21/
05)
estimated
EECs
for
the
parent
compound
alone.
Since
that
time,
HED
determined
that
the
degradates
of
imazaquin
have
the
potential
to
be
toxicologically
equivalent
to
the
parent
compound
and
so
must
be
taken
into
account.
Aqueous
photolysis
is
the
only
significant
degradation
pathway
for
imazaquin
and
leads
to
four
major
degradates
of
greater
than
10%
of
the
applied
amount
(
3­
quinolinecarboxylic
acid;
2,3
quinolinedicarboxylic
acid
imide;
2,3
dihydro­
3­
imino­
1H­
pyrrolo­[
3,4b]
quinolin­
1­
one;
and
2,3
quinolinedicarboxylic
acid).
Surface
water
modeling
for
the
most
vulnerable
scenario,
turf,
was
repeated
with
an
updated
photolysis
half­
life
that
incorporated
these
degradates.
The
updated,
total
residue
half­
life
was
calculated
by
performing
first
order
linear
regression
on
the
log
transformed
sum
total
of
imazaquin
plus
each
of
2
the
four
major
degradates
at
each
sampling
point.
There
is
no
change
to
the
groundwater
EEC
because
in
that
situation,
the
parent
compound
is
not
exposed
to
light
and
so
aqueous
photolysis
does
not
occur.
The
results
of
this
analysis
are
presented
in
Table
1.

Table
1
also
includes
updated
EECs
for
the
ornamental
scenario.
The
modeling
in
the
original
assessment
contained
a
mistake
which
led
to
overestimation
of
the
surface
water
EECs
resulting
from
application
of
imazaquin
to
ornamental
trees,
shrubs,
and
groundcover.
The
corrected
EECs
are
presented
in
Table
1.

Table
1.
Imazaquin
EECs
*

Surface
water
(
PRZM
/
EXAMS)
Groundwater
(
SCIGROW)

Acute
(
Peak)
Chronic
(
Annual
average)
Acute
&
Chronic
Soybeans
1.8
µ
g
ae/
L
0.4
µ
g
ae/
L
3.8
µ
g
ae/
L
Ornamental
1.9
µ
g
ae/
L
1.0
µ
g
ae/
L
15.6
µ
g
ae/
L
Turf
­
1
app.
15.2
µ
g
ae/
L
5.0
µ
g
ae/
L
15.6
µ
g
ae/
L
Turf
­
1
app
(
total
residue)
16.0
µ
g
ae/
L
6.7
µ
g
ae/
L
15.6
µ
g
ae/
L
Turf
­
2
app.
20.0
µ
g
ae/
L
7.6
µ
g
ae/
L
31.1
µ
g
ae/
L
Turf
­
2
app
(
total
residue)
21.8
µ
g
ae/
L
11.6
µ
g
ae/
L
31.1
µ
g
ae/
L
*
All
EECs
are
for
parent
compound
only
unless
otherwise
specified.
