UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
DATE:
March
27,
2001
SUBJECT:
Oxadiazon.
List
B
Reregistration
Case
2485.
PC
Code
109001.
Product
Chemistry
and
Residue
Chemistry
Chapter
for
the
Reregistration
Eligibility
Decision
[
RED]
Document.
DP
Barcode
D273740.

FROM:
Sheila
Piper,
Chemist
Chemistry
Exposure
Branch
Health
Effects
Division
[
7509C]

THRU:
Francis
B.
Suhre,
Branch
Senior
Scientist
Chemistry
Exposure
Branch
Health
Effects
Division
[
7509C]

TO:
Nancy
McCarroll,
Risk
Assessor
Toxicology
Branch
Health
Effects
Division
[
7509C]

The
Product
Chemistry
and
Residue
Chemistry
databases
for
oxadiazon
are
complete.
The
registrant,
Aventis
Environmental
Science
USA
is
no
longer
supporting
oxadiazon
in
or
on
food,
feed,
or
residential
uses
(
Revocation
Letter
for
Oxadiazon
Tolerances,
1/
24/
01).
Currently,
the
registrant
is
only
supporting
the
use
of
oxadiazon
on
golf
courses
and
ornamentals.
The
request
for
revocation
of
oxadiazon
on
food,
feed
or
residential
uses
has
been
granted
and
tolerances
will
be
revoked.

Attachments
1
and
2:
Oxadiazon
Product
and
Residue
Chemistry
RED
Chapter
cc:
SF,
RF,
List
B
File,
S.
Piper
RDI:
F.
B.
Suhre:
3/
23/
01
7509C:
CEB1:
CM­
2:
Room
810F:
308­
2717:
Oxadiazon
REREGISTRATION
ELIGIBILITY
DECISION
PRODUCT
CHEMISTRY
CONSIDERATIONS
PC
Code
109001;
Case
2485
(
DP
Barcode
D273104)

Oxadiazon
[
2­
tert­
butyl­
4­(
2,4­
dichloro­
5­
iospropoxyphenyl)­

2­
1,3,4­
oxadiazolin­
5­
one]
is
a
preemergence,
early
postemergence
herbicide
registered
to
control
annual
grasses
and
broadleaf
weeds.

Empirical
formula:
C
15
H
18
Cl
2
N
2
O
3
Molecular
weight:
345.2
CAS
Registry
No.:
19666­
30­
9
PC
Code:
109001
Oxadiazon
A
search
of
REFS
conducted
2/
14/
01
identified
a
single
oxadiazon
MP
registered
under
PC
Code
109001,
the
Aventis
Environmental
Science
USA
LP
94
%
technical
[
T];
EPA
Reg.
No.
264­
450.
There
are
47
active
end
use
products.
Only
the
Aventis
94%
T
is
subject
to
a
RED.

The
product
chemistry
data
base
is
complete.
However,
the
current
Confidential
Statement
of
Formula
[
CSF],
dated
4/
7/
78,
is
inadequate.
Nominal
concentration
and
upper
limit
must
be
stated
for
all
components.
Additionally,
the
lower
limit
must
be
stated
for
the
a.
i.
The
CSF
must
be
executed
by
the
current
registrant.
The
Series
830
physical
and
chemical
properties
are
given
in
the
table
below:
GLN
MRID
Data
6302
Color
jacket
white
6303
Physical
state
"
crystalline
powder
6304
Odor
"
odorless
7200
MP
"
90
C
7300
Bulk
density
41565701
1.3
g/
mL
7840
Water
solubility
jacket
0.0007
g/
L
@
20
C
7950
vp
41230301
7.76x10­
7
mm
Hg
[
gas
satn.]

7550
P
ow
41230302
log
P
=
4.91
6313
Stability
to
normal
and
elevated
temperatures,
metals,
and
metal
ions
41877601
stable
for
30
days
@
55
C;
stable
in
presence
of
aluminum,
iron,
&
tin
pwds.
But
>
5%
loss
in
presence
of
ferric
chloride.
Bibliography
41565701
Chabassol,
Y.;
Hunt,
G.
[
1990]
Oxadiazon­
Specific
Gravity
and
Density
at
20
C:
Study
No.
89­
15.
Unpublished
study
prepared
by
Rhone­
Poulenc
Ag
Co.
16
p.

41230301
Hoffman,
M.
[
1989]
Vapor
Pressure
Determination
of
Oxadiazon:
Project
No.
HLA
6001­
372.
Unpublished
study
prepared
by
Hazelton
Labs.
America,
Inc.
71
p.

41230302
Seymour,
R.;
Hall,
L.
[
1988]
Octanol/
Water
Partition
Coefficient
Determination
for
Oxadiazon;
Report
No.
40434.
Unpublished
study
prepared
by
Rhone­
Poulenc
Ag
Co.
12
p.

41877601
Sanders,
J.
[
1991]
Oxadiazon,
Technical
­
Determination
of
Stability;
Lab.
ID
4053­
91­
0061­
AS.
Unpublished
study
prepared
by
Ricerca,
Inc.
102
p.

OXADIAZON
REREGISTRATION
ELIGIBILITY
DECISION
RESIDUE
CHEMISTRY
CONSIDERATIONS
PC
Code
109001;
Case
2485
(
DP
Barcode
D273740)

TABLE
OF
CONTENTS
page
INTRODUCTION
.
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2
REGULATORY
BACKGROUND
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2
SUMMARY
OF
SCIENCE
FINDINGS
.
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3
GLN
860.1200:
Directions
for
Use
.
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.
3
GLN
860.1300:
Nature
of
the
Residue
­
Plants
.
.
.
.
.
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.
3
GLN
860.1300:
Nature
of
the
Residue
­
Animals
.
.
.
.
.
.
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.
3
GLN
860.1340:
Residue
Analytical
Methods
.
.
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.
4
GLN
860.1360:
Multiresidue
Methods
.
.
.
.
.
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.
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.
4
GLN
860.1380:
Storage
Stability
Data
.
.
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4
GLN
860.1500:
Crop
Field
Trials
.
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4
GLN
860.1520:
Processed
Food/
Feed
.
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4
GLN
860.1480:
Meat,
Milk,
Poultry,
Eggs
.
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.
.
5
GLN
860.1400:
Water,
Fish,
and
Irrigated
Crops
.
.
.
.
.
.
.
.
.
.
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.
5
GLN
860.1460:
Food
Handling
.
.
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.
5
GLNs
860.1850
and
860.1900:
Confined/
Field
Accumulation
in
Rotational
Crops
.
.
.
5
TOLERANCE
REASSESSMENT
SUMMARY
.
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5
Tolerances
Listed
Under
40
CFR
§
180.346
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6
CODEX
HARMONIZATION
.
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7
DIETARY
EXPOSURE
ASSESSMENT
.
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7
AGENCY
MEMORANDA
CITED
IN
THIS
DOCUMENT
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7
INTRODUCTION
2
Oxadiazon,
(
2­
tert­
butyl­
4­(
2,4­
dichloro­
5­
isopropoxyphenyl)­

21,3,4­
oxadiazolin­
5­
one)
is
a
selective
pre­
emergent
and
early
post
emergence
herbicide
that
is
effective
primarily
for
the
control
of
annual
grasses
and
broadleaf
weeds
in
turf.
Oxadiazon
is
manufactured
by
Aventis
CropScience
USA,
under
the
trade
name
Ronstar
®
and
formulations
are
available
as
emulsifiable
concentrates,
granules,
flowable
and
wetable
powders.
The
registrant
are
no
longer
supporting
oxadiazon
in
or
on
food,
feed
or
residential
uses.
Currently,
the
registrant
is
only
supporting
the
use
of
oxadiazon
on
golf
courses
and
ornamentals
(
Revocation
Letter
for
Oxadiazon
Tolerances,
1/
24/
01).

REGULATORY
BACKGROUND
Oxadiazon
is
a
list
B
reregistration
chemical
and
was
subject
of
a
Phase
III
Review
dated
1/
3/
90
(
C.
Olinger).
This
document
summarized
regulatory
conclusions
on
the
available
residue
chemistry
data
and
specified
that
additional
data
were
not
required
for
reregistration
purposes.
The
information
contained
in
this
document
outlines
the
current
Residue
Chemistry
Science
Assessments
with
respect
to
the
reregistration
of
oxadiazon.

Tolerances
have
been
established
for
combined
residues
of
oxadiazon
and
its
metabolites
[
2­
tertbutyl
4­(
2,4­
dichloro­
5­
hydroxyphenyl)­

21,3,4­
oxadiazolin­
5­
one
and
2­
carboxyiso­
propyl­
4­(
4­
dichloro)
5­
isopropo­
xyphenyl)­

21,3,4­
oxadiazolin­
5­
one]
in
or
on:
rice
straw
(
0.2
ppm);
milk
fat
(
0.1
ppm;
reflecting
negligible
residues
in
milk);
Brazil
nuts,
bush
nuts,
butternuts,
cashews,
chestnuts,
crabapples,
filbert,
hazelnuts,
hickory
nuts,
macadamia
nuts,
pears,
pecans,
pistachio
nuts,
quinces,
rice
grain,
stone
fruit
and
walnuts
(
0.05
ppm);
and
in
the
meat,
fat,
and
meat
byproducts
of
cattle,
goats,
hogs,
horses,
and
sheep
(
0.01
ppm)
[
40
CFR
§
180.346].

The
HED
Metabolism
Assessment
Review
Committee
(
S.
Piper,
D272425,
2/
13/
01)
has
concluded
that
the
parent
compound,
oxadiazon
is
the
only
residue
to
be
included
in
a
drinking
water
risk
assessment.
The
chemical
structure
of
oxadiazon
is
shown
below:

SUMMARY
OF
SCIENCE
FINDINGS
GLN
860.1200:
Directions
for
Use
A
REFS
search,
conducted
on
2/
14/
01,
identified
a
single
oxadiazon
MP
registered
under
PC
Code
109001,
the
Aventis
3
Environmental
Science
USA
LP
94%
technical
[
T];
EPA
Reg.
No.
264­
450.
There
are
47
active
end
use
products,
registered
pesticide
products
under
FIFRA
with
labeling
claiming
oxadiazon
as
the
active
ingredient.
The
use
sites
claimed
on
the
labels
of
these
products
are
non­
residential
lawns
(
turf)
and
ornamental
plants.
Three
of
the
products
are
registered
under
24(
c)
and
the
other
44
products
are
registered
under
Section
3
of
FIFRA.
Only
the
Aventis
94%
is
subject
to
a
reregistration
eligibility
decision.

For
the
purpose
of
generating
this
Residue
Chemistry
Science
Chapter,
the
Aventis
will
not
support
aerial
application
(
will
put
restriction
on
the
Ronstar
®
labels)
or
greenhouse
useage
(
already
restricted
on
the
Ronstar
®
labels).
Aventis
will
add
these
label
restrictions
to
the
products
(
Ronstar
®
50%
intermediate
and
Ronstar
®
Technical)
used
by
other
registrants
to
formulate
their
own
products.
Details
of
the
rates
and
application
intervals
are
presented
below:

$
Maximum
of
4
lbs
ai/
A
per
application
per
six
month
period.

$
If
the
4
lbs
is
split,
applications
within
the
six
month
period
must
be
6
to
8
weeks
apart.

$
Maximum
of
8
lbs
ai/
A
per
year
or
4
lbs
every
six
months.

GLN
860.1300:
Nature
of
the
Residue
­
Plants
The
qualitative
nature
of
the
residue
in
plants
is
not
adequately
understood.
The
registrant
submitted
an
inadequate
rice
metabolism
study.
Furthermore,
no
data
were
available
concerning
the
metabolism
of
oxadiazon
in/
on
crops
representing
orchard
crops.
The
registrant
has
requested
revocation
of
oxadiazon
on
food/
feed
uses
and
tolerances
will
be
revoked.

GLN
860.1300:
Nature
of
the
Residue
­
Animals
The
qualitative
nature
of
the
residue
in
animals
is
not
adequately
understood.
The
registrant
submitted
an
inadequate
ruminant
metabolism
study.
Furthermore,
no
data
on
poultry
were
submitted.
The
registrant
has
requested
revocation
of
oxadiazon
on
food/
feed
uses
and
tolerances
will
be
revoked.

GLN
860.1340:
Residue
Analytical
Methods
Adequate
methodology
is
available
for
the
enforcement
of
tolerances
for
residues
of
oxadiazon
in
or
on
plant
and
animal
commodities.
A
GLC/
electron
capture
(
EC)
method
is
included
in
Pesticide
Analytical
Manual
(
PAM)
Vol.
II
as
Method
1
for
analysis
of
oxadiazon
residues
in
rice,
soybeans,
peanuts,
onions,
and
potatoes
(
Pesticide
Reg.
Sec,
180.346).
A
modified
version
of
4
Method
III
has
also
been
used
for
analysis
of
residues
in
turf,
nuts,
and
orchard
fruit.
Method
III
includes
similar
procedures
for
analysis
of
oxadiazon
residues
in
milk
and
dairy
cattle
tissue.

GLN
860.1360:
Multiresidue
Methods
The
Pestrak
data
base
dated
12/
13/
89
indicates
that
oxadiazon
recovery
is
complete
(>
80%)
using
Multiresidue
Protocol
D
and
either
partial
(
50­
80%;
fatty
foods)
or
complete
(
non­
fatty
foods)
using
Protocol
E,
and
that
the
two
metabolites
of
concern
were
included
in
the
tolerance
expression.
The
requirements
to
conduct
multiresidue
method
trials
with
oxadiazon
and
its
metabolites
are
waived.

GLN
860.1380:
Storage
Stability
Data
The
registrant
has
requested
revocation
of
oxadiazon
on
food/
feed
uses
and
tolerances
will
be
revoked.
Therefore,
reregistration
requirements
for
storage
stability
data
are
waived
for
plant
and
animal
commodities.

GLN
860.1500:
Crop
Field
Trials
The
reregistration
requirements
for
magnitude
of
the
residue
in/
on
the
following
raw
agricultural
commodities
(
RACs)
have
been
waived:
rice
(
grain
and
straw),
Brazil
nuts,
bush
nuts,
butternuts,
cashews,
chestnuts,
crabapples,
filberts,
hazelnuts,
hickory
nuts,
macadamia
nuts,
pears,
pecans,
pistachio
nuts,
quinces,
stone
fruits
and
walnuts.
The
registrant
has
requested
revocation
of
oxadiazon
on
food/
feed
uses
and
tolerances
will
be
revoked.

GLN
860.1520:
Processed
Food/
Feed
The
registrant
has
requested
revocation
of
oxadiazon
on
food/
feed
uses
and
tolerances
will
be
revoked.
Therefore,
reregistration
requirements
for
magnitude
of
the
residue
in
the
processed
commodities
of
plum
(
dried
prune)
has
been
waived.

GLN
860.1480:
Meat,
Milk,
Poultry,
Eggs
The
reregistration
requirements
for
magnitude
of
the
residue
in
meat,
milk,
poultry,
and
eggs
are
waived.
The
registrant
has
requested
revocation
of
oxadiazon
on
food/
feed
uses
and
tolerances
will
be
revoked.

GLN
860.1400:
Water,
Fish,
and
Irrigated
Crops
5
Oxadiazon
is
presently
not
registered
for
direct
use
on
water
and
aquatic
food
and
feed
crops;
therefore,
no
residue
chemistry
data
are
required
under
this
guideline
topic.

GLN
860.1460:
Food
Handling
Oxadiazon
is
presently
not
registered
for
use
in
food­
handling
establishments;
therefore,
no
residue
chemistry
data
are
required
under
this
guideline
topic.

GLNs
860.1850
and
860.1900:
Confined/
Field
Accumulation
in
Rotational
Crops
The
registrant
has
requested
revocation
of
oxadiazon
on
food/
feed
uses
and
tolerances
will
be
revoked.
Therefore,
reregistration
requirements
for
accumulation
in
rotational
crops
are
waived.

Tolerance
Reassessment
Summary
Tolerances
for
residues
of
oxadiazon
in/
on
plant
and
animal
RACs
are
currently
expressed
in
terms
of
oxadiazon
and
its
metabolites
[
2­
tert­
butyl­
4­(
2,4­
dichloro­
5­
hydroxyphenyl)­

21,3,4­
oxadiazolin­
5­
one
and
2­
carboxyiso­
propyl­
4­(
4­
dichloro)
5­
isopropo­
xyphenyl)­

21,3,4­
oxadiazolin­
5­
one]
[
40
CFR
§
180.346].

The
HED
Metabolism
Assessment
Review
Committee
(
S.
Piper,
D272425,
2/
13/
01)
has
concluded
that
the
parent
compound,
oxadiazon
is
the
only
residue
to
be
included
in
a
drinking
water
risk
assessment.
The
tolerance
definition
listed
under
40
CFR
§
180.346
should
be
changed
to
the
following:

Tolerances
have
been
revoked
for
oxadiazon
and
its
metabolites
[
2­
tert­
butyl­
4­(
2,4­
dichloro­
5­
hydroxyphenyl)­

21,3,4­
oxadiazolin­
5­
one
and
2­
carboxyiso­
propyl­
4­(
4­
dichloro)
5­
isopropo­
xyphenyl)­

21,3,4­
oxadiazolin­
5­
one]
in
or
on
the
following
raw
agricultural
commodities
presented
in
Table
A:

Table
A.
Tolerance
Reassessment
Summary
for
Oxadiazon.

Commodity
Current
Tolerance
(
ppm)
Tolerance
a
Reassessment
(
ppm)
Comme
Tolerances
listed
under
40
CFR
§
180.346:

Brazil
nuts,
bush
nuts,
butternuts,
cashews,
chestnuts,
filbert,
hazelnuts,
hickory
nuts,
macadamia
nuts,
pecans,
pistachio
nuts,
and
walnuts.
0.05
Revoke
The
registran
Cattle,
meat,
fat,
mbyp
0.01
Revoke
The
registran
Crabapples
0.05
Revoke
The
registran
Commodity
Current
Tolerance
(
ppm)
Tolerance
a
Reassessment
(
ppm)
Comment/
Correct
Commodity
Definition
6
Goats,
meat,
fat,
mbyp
0.01
Revoke
The
registrant
will
not
support
this
use.

Hogs,
meat,
fat,
mbyp
0.01
Revoke
The
registrant
will
not
support
this
use.

Horses,
meat,
fat,
mbyp
0.01
Revoke
The
registrant
will
not
support
this
use.

Milk,
fat
0.1
Revoke
The
registrant
will
not
support
this
use.

Pears
2.0
Revoke
The
registrant
will
not
support
this
use.

Quinces
0.05
Revoke
The
registrant
will
not
support
this
use.

Rice,
grain
0.05
Revoke
The
registrant
will
not
support
this
use.

Rice,
straw
0.2
Revoke
The
registrant
will
not
support
this
use.

Sheep,
meat,
fat,
mbyp
0.01
Revoke
The
registrant
will
not
support
this
use.

Stone
fruits
0.05
Revoke
The
registrant
will
not
support
this
use.

a
The
registrant,
Aventis
submitted
a
revocation
letter
(
1/
24/
01)
for
oxadiazon
in
which
they
are
not
supporting
any
tolerances
for
oxadiazon
in
or
on
food.

DIETARY
EXPOSURE
ASSESSMENT
SUMMARY
A
dietary
risk
assessment
for
the
uses
of
oxadiazon
is
not
needed
at
this
time
because
there
are
no
food/
feed
uses
for
oxadiazon.

CODEX
HARMONIZATION
7
There
are
no
CODEX,
Canadian,
or
Mexican
tolerances
for
oxadiazon
residues
on
the
16
commodities
listed
in
40
CFR
§
180.346.

AGENCY
MEMORANDA
CITED
IN
THIS
DOCUMENT
HED
No:
None
DP
Barcode:
D271728
Subject:
Oxadiazon.
Issues
to
be
Presented
to
the
HED
Metabolism
Assessment
Review
Committee
(
MARC).
From:
S.
Piper,
HED
To:
HED
Metabolism
Committee
Dated:
1/
10/
01
MRID(
s):
None
HED
No:
None
DP
Barcode:
D272425
Subject:
Oxadiazon.
The
Outcome
of
the
HED
Metabolism
Assessment
Review
Committee
Meeting
Held
on
1/
30/
01.
From:
S.
Piper,
HED
To:
HED
Metabolism
Committee
Dated:
2/
13/
01
MRID(
s):
None
8
