UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
TXR.
No:
0052466
MEMORANDUM
DATE:
March
9,
2004
SUBJECT:
Trifluralin:
Health
Effects
Division
(
HED)
Metabolism
Assessment
Review
Committee
(
MARC)
Decision
Document.
Meeting
Date:
4
February
2004.
PC
Code:
036101
REVIEWER:
Sheila
Piper,
Chemist
Chemistry
&
Exposure
Branch/
Health
Effects
Division
(
7509C)

THROUGH:
Christine
Olinger,
HED
MARC
Chair
David
Miller,
Branch
Senior
Scientist
Health
Effects
Division
(
7509C)

TO:
Yan
Donovan,
HED
MARC
Executive
Secretary
(
7509C)

Introduction
The
MARC
met
on
February
4,
2004
to
discuss
the
trifluralin
residues
of
concern
in
plants
(
corn
and
mustard),
livestock,
rotational
crops
and
drinking
water.

Material
Reviewed
A
briefing
document
was
prepared
by
S.
Piper
(
6­
January­
2004)
also
included
environmental/
water
information
provided
by
Santhini
Ramasamy,
of
the
Environmental
Fate
and
Effects
Division
(
EFED).
Rotational
crop
information,
not
a
part
of
the
original
briefing
document,
was
also
provided
to
the
MARC
(
B.
Cropp­
Kohlligian,
DP
Barcode
D206342,
7/
25/
95).

Members
Attended
Alberto
Protzel,
Abdallah
Khasawinah,
Yan
Donovan,
Norman
Birchfield,
Leonard
Keifer,
Christine
Olinger,
Leung
Cheng,
Rick
Loranger,
Pauline
Wagner
and
Bill
Wassell
Members
in
Absentia
PV
Shah
and
John
Doherty
­
2­
Alternate
Members
Attended
None
Non
Members
Sheila
Piper,
Richard
Griffin,
Santhini
Ramasamy
and
Bob
Fricke
MARC
Decision
Table
The
recommendations
by
the
MARC
for
degradates
and
metabolites
to
be
included
in
the
risk
assessment,
and
the
metabolites
included
in
the
tolerance
expression
are
summarized
in
Table
1.

Table
1.
Summary
of
MARC
Decision
for
Trifluralin
Chemical:
Trifluralin.

Date:
04­
February­
2004
Residues
of
Concern
Matrix
Risk
Assessment
Tolerance
Expression
Plants
Parent
only
Parent
only
Livestock
Use
TRR
from
cow
metabolism
study
No
decision
Rotational
Crops
Parent
only1
Parent
only1
Water
Parent,
TR­
4,
TR­
6
and
TR­
15
N/
A
1
Only
if
the
registrant
was
to
change
the
plant
back
interval
to
equal
to
or
greater
than100
days.

Rationale
Plants:
The
MARC
concluded
that
for
the
risk
assessment
and
tolerance
expression,
parent
only
is
the
residue
of
concern.
Metabolism
studies
conducted
on
field
corn
at
a
1.5x
rate
and
mustard
at
a
2.6x
rate
indicated
that
parent
was
the
only
major
residue
(>
10%
TRR).
There
are
no
specific
toxicity
concerns
for
all
other
minor
metabolites.

Livestock:
No
decision
was
made
regarding
the
tolerance
expression
for
livestock.
The
MARC
concluded
that
a
new
animal
metabolism
study
with
higher
dosing
levels
and
better
characterization/
identification
of
metabolites
is
needed
for
continued
registration
of
the
midseason
alfalfa
use
which
produces
significantly
higher
exposure
to
livestock.
The
MARC
also
­
3­
recommended
that
for
the
time
being,
the
total
radioactive
residues
(%
TRR)
from
livestock
tissues
and
milk
should
be
used
in
the
risk
assessment.

The
available
ruminant
metabolism
studies
in
dairy
cow
(
2.8X
MTDB)
indicated
that
no
major
metabolite
were
found.
While
the
registrant
claimed
that
parent,
TR­
2,
TR­
4,
TR­
5,
TR­
6,
TR­
7,
TR­
14,
TR­
15,
TR­
42
and
TR­
44
are
minor
metabolites,
no
quantitative
information
was
provided,
such
as
the
%
TRR
for
each.
There
was
no
characterization/
identification
of
metabolites
in
the
hen
metabolism
study.
As
a
result,
the
MARC
was
unable
to
determine
which
metabolites
the
registrant
should
analyze
in
any
future
feeding
study.

Rotational
Crop:
Provided
the
registrant
changes
the
plant­
back
interval
(
PBI)
to
100
days
or
greater,
the
MARC
concluded
that
the
parent
is
the
only
residue
of
concern
for
the
risk
assessment
and
the
tolerance
expression.
However,
insufficient
characterization
of
the
total
radioactive
residues
was
conducted
in
the
existing
study
for
the
MARC
to
make
a
decision
of
residues
of
concern
for
plant­
back
intervals,
of
less
than
100
days.
Should
the
registrant
want
a
PBI
of
less
than
100
days,
a
new
study,
conducted
at
a
1x
rate,
must
be
conducted
with
sufficient
characterization
of
the
samples
at
the
desired
PBI.

The
confined
rotational
crop
study
conducted
at
0.4X
rate
indicated
that
TRRs
are
very
low
(<
0.010
ppm)
after
100
days
plant
back
interval
(
B.
Cropp­
Kohlligian,
D206342,
7/
25/
95).
However,
with
the
30­
day
PBI
study,
the
TRRs
are
as
high
as
0.09
ppm.
Further
identification
of
the
30­
day
TRR
indicated
that
parent
was
found
as
a
minor
component
in
turnip
root,
while
other
unknown
peaks
with
>
10%
TRR
were
not
identified.

Drinking
Water:
The
environmental
fate
data
suggest
that
trifluralin
and
degradates
(
TR­
4,
TR­
6
and
TR­
15)
could
be
present
in
drinking
water,
however,
if
the
risk
assessment
team
finds
that
the
photodegradates
and
anaerobic
soil
degradates
are
insignificant
contributors
to
overall
exposure
after
water
modeling;
they
may
choose
to
remove
them
from
the
risk
assessment.

Environmental
fate
studies
indicate
that
parent
is
moderately
persistent
in
soil.
The
half
life
in
laboratory
aerobic
soil
metabolism
studies
was
116
to
201
days
and
the
half
life
in
terrestrial
field
dissipation
studies
ranged
from
15
to
149
days.
Trifluralin
is
not
mobile
(
binds
to
soil
with
high
affinity).
Therefore
it
is
not
likely
to
leach
into
groundwater
at
high
levels
and
more
likely
to
reach
surface
water
bound
to
eroding
soil
than
in
the
dissolved
phase.
Under
anaerobic
conditions,
trifluralin
degrades
more
rapidly
in
the
laboratory
with
a
half­
life
of
25
to
59
days.
Laboratory
studies
indicate
that
trifluralin
undergoes
a
rapid
degradation
by
photolysis
in
aqueous
conditions
(
half­
life
8.9
hours).
Trifluralin
photolyzes
more
slowly
in
soil
with
the
half­
life
of
41
days.
Trifluralin
is
moderately
volatile
and
soil
incorporation
is
recommended,
but
not
mandatory,
to
reduce
losses
to
volatilization.
Soil
incorporation
would
greatly
reduce
the
potential
for
soil
photolysis
to
occur.
Based
on
the
use
pattern
(
pre­
plant
soil
and
direct
spray),
the
major
route
of
degradation
is
expected
to
be
aerobic
soil
metabolism
but
under
some
­
4­
conditions
aqueous
photolysis,
soil
photolysis,
and
anaerobic
soil
metabolism
may
also
be
major
contributors.

In
the
aerobic
soil
metabolism
study,
no
major
degradates
were
formed.
Unextractable
residues
and
volatilization
accounted
for
~
50%
and
~
20%
of
applied
material,
respectively.
In
aqueous
photolysis,
the
major
degradates
were
TR­
6
and
TR­
15.
In
anaerobic
soil
metabolism
study,
the
major
degradate
is
TR­
4.
These
degradates
range
from
13%
to
47%
of
the
applied
dose.
Based
on
a
visual
evaluation
of
the
polarity
of
the
degradates
and
a
previously
conducted
EPIWIN
physical
property
analysis,
these
degradates
are
expected
to
have
lower
soil
binding
potential
(
higher
mobility)
than
trifluralin.
The
degradates
share
similar
structure
as
trifluralin
and
therefore
are
considered
to
share
similar
toxicity
as
the
parent.

Although
TR­
20
was
included
as
a
degradate
of
concern
for
benfluralin,
the
data
available
for
trifluralin
suggest
that
this
material
forms
only
very
low
levels
after
long
periods
of
time.
As
a
result
MARC
concluded
that
it
is
unlikely
to
result
in
significant
exposure.

cc:
S.
Piper
(
CEB),
S.
Ramasamy
(
EFED)
HED
Metabolism
Committee
file
(
Y.
Donovan),
RRB3RF
S.
Piper,
HED,
CEB:
CM­
2:
810F:
308­
2717:
2/
24/
04
