UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
MEMORANDUM
Date:
December
13,
2005
Subject:
Dimethenamid­
p.
Tolerance
Petition
for
Dimethenamid­
p
in/
on
Green
Onion.
Summary
of
Analytical
Chemistry
and
Residue
Data.
Petition
Number
4E6844.

DP
Number:
D318282
Decision
Number:
356801
PC
C
Filename:
D318282.
mem.
wpd
From:
Shaja
Brothers,
EPS
Risk
Integration
Minor
Use
and
Emergency
Response
Branch
Registration
Division
(
7505C)

Through:
William
Cutchin,
Chemist
Technical
Review
Branch
Registration
Division,
(
7505C)

To:
Christina
Swartz,
Branch
Chief
Registration
Action
Branch
2
Health
Effects
Division
(
7509C)

Executive
Summary
OUTLOOK
 
Herbicide
(
EPA
Reg.
No.
7969­
156)
is
an
emulsifiable
concentrate
(
EC)
formulation
containing
6.0
lb
ai/
gal
(
pounds
active
ingredient
per
gallon)
of
dimethenamid­
p.
This
product
contains
a
chloroacetamide
herbicide
and
is
active
against
annual
grasses,
broadleaf
weeds,
and
sedges.

In
2001,
a
total
of
six
green
onion
field
trials
were
conducted
established
in
the
North
American
Free
Trade
Agreement
(
NAFTA)
Growing
Regions
2,
3,
5,
5B,
6
and
12.
The
trials
were
conducted
in
Florida
(
FL),
Georgia
(
GA),
Texas
(
TX),
British
Columbia
(
BC),
Ontario
(
ON),
and
Quebec,
Canada
(
QC).
The
ON
trial
is
supplementary.
At
each
test
site,
one
treated
plot
and
one
untreated
control
plot
were
established.
The
treated
plot
at
each
site
received
one
broadcast
foliar
application
of
dimethenamid­
p
(
6
lb
ai/
gal
EC)
at
0.92­
1.06
lb
ai/
A/
season
(
active
ingredient
per
acre
per
season).
Timely
rainfall
and/
or
irrigation
received
within
3­
4
days
of
application
were
used
to
move
the
herbicide
into
the
upper
soil
surface.
All
applications
were
made
in
a
spray
volume
of
26­
38
gal/
A
using
broadcast
ground
equipment.
No
adjuvants
were
added
to
the
spray
mixture.
Residues
of
dimethenamid­
p
were
<
0.01
ppm
(
limit
of
quantitation);
LOQ
in/
on
and
at
least
24
green
onion
whole
plant
raw
agricultural
commodity
(
RAC)
samples
harvested
at
pre­
harvest
intervals
(
PHI)
of
28­
32
days.
Residues
were
<
0.01
ppm
in/
on
two
additional
green
onion
RAC
samples
harvested
20
days
after
treatment.
The
highest
average
field
trial
(
HAFT)
value
for
onion
plants
was
<
0.01
ppm.

The
nature
of
the
residue
in
plants
is
adequately
understood.
Soybean
and
corn
metabolism
Dimethenamid­
p
Summary
of
Analytical
Chemistry
and
Residue
Data
Barcode:
D318282
2
  
8
studies
are
available
and
have
been
reviewed
by
the
Agency.
The
metabolism
of
dimethenamid
in
plants
involves
conjugation
with
glutathione,
with
subsequent
transformation
of
the
glutathione
moiety
to
yield
a
variety
of
metabolites.
The
residue
of
concern
for
purposes
of
the
tolerance
expression
(
and
risk
assessment)
was
determined
to
be
dimethenamid
per
se.
There
are
no
livestock
feed
items
associated
with
green
onion.
Therefore,
the
nature
of
the
residue
in
livestock
is
not
relevant
to
this
action.
Adequate
enforcement
methodology
(
GC
nitrogen­
phosphorous
detector;
GC/
NPD)
is
available
to
enforce
the
tolerance
expression.
The
GC/
NPD
analytical
method
(
BASF
method
AM­
0884­
0193­
1)
used
for
determining
residues
of
dimethenamid­
p
in
green
onion
is
adequate
for
data
collection
purposes.

Dimethenamid
and
dimethenamid­
p
are
selective,
preemergence,
chloroacetamide
herbicides
with
existing
tolerances
for
bean,
dry,
seed;
beet,
garden,
roots;
beet,
garden,
tops;
beet,
sugar,
dried
pulp;
beet,
sugar,
molasses;
beet,
sugar,
roots;
beet,
sugar,
tops;
corn,
field,
forage;
corn,
field,
grain;
corn,
field,
stover;
corn,
pop,
forage;
corn,
pop,
grain;
corn,
pop,
stover;
corn,
sweet,
forage;
corn,
sweet,
kernal
plus
cob
with
husk
removed;
corn,
sweet,
stover;
garlic;
horseradish;
onion,
dry
bulb;
peanut,
hay;
peanut,
nutmeat;
shallot,
bulb;
sorghum,
grain;
sorghum,
grain,
forage;
sorghum,
grain,
stover;
soybean,
seed;
and
tuberous
and
corm
vegetables.
Tolerances
are
established
for
residues
of
dimethenamid,
(
RS)­
2­
chloro­
N­[(
1­
methyl­
2­
methoxy)
ethyl]­
N­(
2,4­
dimethylthien­
3­
yl)
acetamide
under
40
CFR
§
180.464(
a).
As
the
tolerance
expression
includes
both
the
R
and
S
isomers,
these
tolerances
also
cover
the
registered
uses
of
dimethenamid­
p.
The
current
tolerances
for
all
plant
commodities
are
set
at
0.01
ppm.

The
Interregional
Research
Project
Number
4
(
IR­
4)
has
proposed
tolerances
for
dimethenamid­
p
in/
on
onion,
green;
leek;
spring
onion;
scallions;
Japanese
bunching
onion;
green
shallots,
and
green
eschalots
at
0.01
ppm.
There
is
a
high
level
of
confidence
in
the
data
being
used
to
determine
tolerances.
The
residues
were
consistently
below
the
limit
of
detection
(
LOD)
in
all
crops.
There
are
no
metabolites
of
concern.
Processing
data
for
dimethenamid­
p
in/
on
green
bulb
onion
is
not
germane
to
this
action.
Rotational
crop
tolerances
or
restrictions
are
not
required.

Regulatory
Recommendations
and
Residue
Chemistry
Deficiencies
Provided
the
petitioner
submits
a
revised
Section
F,
ARIA
concludes
the
residue
chemistry
database
supports
the
establishment
of
permanent
tolerances
for
the
residues
of
dimethenamid­
p
in/
on
the
RACs
shown
below.
A
human
health
risk
assessment
is
forthcoming.

Leek.....................................................................................................................................
0.01
ppm
Onion,
green........................................................................................................................
0.01
ppm
Onion,
Welsh......................................................................................................................
0.01
ppm
Shallot,
fresh
leaves............................................................................................................
0.01
Dimethenamid­
p
Summary
of
Analytical
Chemistry
and
Residue
Data
Barcode:
D318282
3
  
8
ppm
Background
OUTLOOK
 
Herbicide
(
EPA
Reg.
No.
7969­
156)
is
an
EC
formulation
containing
6.0
lb
ai/
gal
of
dimethenamid­
p.
This
product
is
a
chloroacetamide
herbicide
and
is
active
against
annual
grasses,
broadleaf
weeds,
and
sedges.
It
is
currently
being
developed
by
BASF
Corporation
for
agricultural
use.
IR­
4
has
received
a
request
for
the
minor
use
of
dimethenamid­
p
on
green
onion
for
control
of
annual
grasses,
broadleaf
weeds,
and
yellow
nutsedge.
The
residue
data
generated
in
this
study
are
to
be
used
to
establish
tolerances
for
dimethenamid­
p
residues
in/
on
treated
green
onion
in
support
of
its
US
EPA
registration
for
use
on
green
onion.
See
Table
A.
1.
for
the
test
compound
nomenclature,
and
Table
A.
2.
for
the
physicochemical
properties
of
the
test
compound.

TABLE
1.
Test
Compound
Nomenclature
Compound
Common
name
Dimethenamid­
P
(
or
S­
dimethenamid)

Company
experimental
name
BAS
656
H;
SAN
1289
IUPAC
name
S­
2­
chloro­
N­(
2,4­
dimethyl­
3­
thienyl)­
N­(
2­
methoxy­
1­
methylethyl)­
acetamide
CAS
name
S­
2­
chloro­
N­[(
1­
methyl­
2­
methoxy)
ethyl]­
N­(
2,4­
dimethyl­
thien­
3­
yl)
acetamide
CAS
#
163515­
14­
8
End­
use
product/(
EP)
OUTLOOK
 
Herbicide
TABLE
2.
Physicochemical
Properties
of
the
Technical
Grade
Test
Compound
Parameter
Value
Reference
a
Melting
point/
range
<­
50
°
C
1999/
10167
pH
3.3
(
in
1%
aqueous
emulsion)
1997/
5178
Density
1.195
g/
cm3
1999/
10167
Water
solubility
(
25
°
C)
1449
±
17
mg/
L
(
pH
6.16)
b
1996/
5411
Solvent
solubility
(
mg/
L
at
25
°
C)
20.8g/
100mL
in
hexane;
soluble
in
all
proportions
in
tetrahydrofuran,
isopropyl
alcohol,
acetone,
ACN,
DMSO,
DCM,
toluene,
and
n­
octanol
1997/
5196
Vapour
pressure
at
25
°
C
1.88
(
±
0.29)
x
10­
5
mm
Hg
1996/
5418
Dimethenamid­
p
Summary
of
Analytical
Chemistry
and
Residue
Data
Barcode:
D318282
4
  
8
TABLE
2.
Physicochemical
Properties
of
the
Technical
Grade
Test
Compound
Parameter
Value
Reference
a
Dissociation
constant
(
pKa)
No
dissociation
(
pH
1
to
11;
25
°
C)
88/
11352
Octanol/
water
partition
coefficient
Log(
KOW)
77.6
and
1.89
(
Pow
and
log
Pow)
1998/
5071
UV/
visible
absorption
spectrumc
 
=
7560;
33nm
1998/
5123
a
BASF
Registration
Document
Number.

b
There
is
no
dissociation
in
water;
therefore,
pH
dependence
on
solubility
is
not
applicable.

c
The
molar
absorption
coefficient
(
 )
and
bandwidth
for
dimethenamid­
p
for
the
236
nm
absorbance
maximum.

TABLE
3.
Summary
of
Directions
for
Use
of
Dimethenamid­
p
Applic.
Timing,
Type,
and
Equip.
Formulation
[
EPA
Reg.
No.]
Applic.
Rate
(
lb
ai/
A)
Max.
No.
Applic.
per
Season
Max.
Seasonal
Applic.
Rate
(
lb
ai/
A)
PHI
(
days)
Use
Directions
and
Limitations
Green
Onion
Broadcast,
Foliar
7969­
156
0.98
1
0.98
28­
32
12
hour
REI
Conclusion.
The
label
is
adequate
to
allow
evaluation
of
the
residue
data
relative
to
the
product
use.

860.1300
Nature
of
the
Residue
­
Plants
PP#
4E6844,
46287301.
DER.
wpd,
S.
Brothers
PP#
0E6196,
D304790,
R.
Griffin,
8/
12/
04
The
nature
of
the
residue
in
plants
is
adequately
understood.
Soybean
and
corn
metabolism
studies
are
available
and
have
been
reviewed
by
the
Health
Effects
Division
(
HED)
Metabolism
Assessment
Review
Committee
(
MARC).
The
metabolism
of
dimethenamid
in
plants
involves
conjugation
with
glutathione,
with
subsequent
transformation
of
the
glutathione
moiety
to
yield
a
variety
of
metabolites.
The
residue
of
concern
for
purposes
of
the
tolerance
expression
(
and
risk
assessment)
was
determined
to
be
dimethenamid
per
se.

860.1300
Nature
of
the
Residue
­
Livestock
There
are
no
livestock
feed
items
associated
with
green
onion.
Therefore,
the
nature
of
the
residue
in
livestock
is
not
relevant
to
this
action.

860.1340
Residue
Analytical
Methods
PP#
0E6196,
D304790,
R.
Griffin,
8/
12/
04
Dimethenamid­
p
Summary
of
Analytical
Chemistry
and
Residue
Data
Barcode:
D318282
5
  
8
An
adequate
enforcement
method
is
available
for
determining
dimethenamid
residues
in
plants
and
soil.
The
GC/
NPD
method
(
AM­
0884­
0193­
1)
has
been
validated
by
the
Agency
and
submitted
for
publication
in
FDA's
Pesticide
Analytical
Manual,
Volume
II.
As
tolerances
are
not
required
for
animal
commodities,
no
analytical
methods
for
animal
commodities
are
required.

860.1360
Multiresidue
Methods
Multiresidue
method
testing
data
were
submitted
to
the
FDA
for
evaluation
M.
Flood,
2/
92.

860.1380
Storage
Stability
PP#
4E6844,
46287301.
DER.
wpd,
S.
Brothers
in
process
A
storage
stability
study
was
conducted
in
conjunction
with
the
residue
study
on
onion.
Control
green
onion
(
ground)
samples
were
fortified
with
a
dimethenamid­
p
(
purity,

96.2%)
in
acetone
solution
at
0.1
ppm
and
stored
at
 ­
16
º
C
until
analysis.
The
stability
of
the
test
substance
in
acetone
was
confirmed
by
an
acceptable
procedural
recovery
of
dimethenamid­
p
fortified
at
0.1
ppm
in
green
onion.
The
sample
set
consisted
of
one
control,
one
freshly­
fortified
sample,
and
three
stored­
fortified
samples.
The
green
onion
samples
were
analyzed
after
391
days
of
frozen
storage.
The
results
indicate
that
residues
of
dimethenamid­
p
are
stable
in
green
onion
(
whole
plant
without
roots
RAC)
samples
for
up
to
391
days
of
frozen
storage.

Data
are
also
available
from
a
previously
conducted
storage
stability
study
using
racemic
(
r,
s)
dimethenamid­
p.
The
results
indicated
that
dimethenamid­
p
is
stable
stored
frozen
(­
20
º
C)
in
corn
forage,
grain,
straw
and
hay
for
at
least
21
months.
The
available
data,
together
with
the
stability
data
generated
in
the
residue
study,
support
the
onion
residue
samples
for
which
the
maximum
frozen
storage
interval,
from
harvest
to
analysis,
was
13
months.

860.1460
Water,
Fish,
and
Irrigated
Crops
As
none
of
the
currently
proposed
uses
include
aquatic
uses,
this
guideline
requirement
is
not
relevant
to
the
current
petition.

860.1460
Food
Handling
There
are
no
food
handling
establishments
(
FHE)
associated
with
this
petition.

860.1480
Meat,
Milk,
Poultry,
and
Eggs
Onion
is
not
a
significant
livestock
feed
item.
Therefore,
a
discussion
of
secondary
residues
from
onion
is
not
germane
to
this
action.
Dimethenamid­
p
Summary
of
Analytical
Chemistry
and
Residue
Data
Barcode:
D318282
6
  
8
860.1500
Crop
Field
Trials
PP#
4E6844,
46287301.
DER.
wpd,
S.
Brothers
in
process
TABLE
4.
Summary
of
Residue
Data
from
Crop
Field
Trials
with
Dimethenamid­
p
Residue
Levels
(
ppm)
Commodity
Total
Applic.
Rate,
(
lb
a.
i./
A)
(
kg
a.
i./
ha)
PHI
(
days)
Analyte
n
Min.
Max.
HAFT*
Mean
Std.
Dev.

20
2
<
0.01
<
0.01
<
0.01
<
0.01
N/
A
Whole
plant
0.92­
1.06
(
1.03­
1.19)
28­
32
Parent
12*
<
0.01
<
0.01
<
0.01
<
0.01
N/
A
*
Including
Supplemental
Data
IR­
4
has
submitted
field
trial
data
for
dimethenamide­
p
on
green
onion.
In
six
supervised
crop
field
trials
conducted
in
FL,
GA,
TX,
BC,
ON,
and
QC,
dimethenamid­
p
6
lb/
gal
EC
was
applied
once
foliarly
to
green
onions
at
0.92­
1.06
lb
ai/
A/
season
(
1.03­
1.19
kg
ai/
ha/
season).
The
number
and
location
of
the
field
trials
for
green
onion
are
adequate
based
on
the
NAFTA
representative
growing
regions
(
ON
trial
is
supplementary).

At
each
test
site,
one
treated
plot
and
one
untreated
control
plot
were
established.
The
treated
plot
at
each
site
received
one
broadcast
foliar
application
of
dimethenamid­
p
(
6
lb
ai/
gal
EC)
at
0.92­
1.06
lb
ai/
A/
season.
However,
at
ON04
site,
the
test
substance
was
 
6.03%
under
applied
(
supplementary
data).
Timely
rainfall
and/
or
irrigation
received
within
3­
4
days
of
application
were
used
to
move
the
herbicide
into
the
upper
soil
surface.
All
applications
were
made
in
a
spray
volume
of
26­
38
gal/
A
using
broadcast
ground
equipment.
No
adjuvants
were
added
to
the
spray
mixture.

Duplicate
untreated
control
and
treated
green
onion
RAC
samples
(
whole
plant
without
roots)
were
harvested
at
commercial
maturity,
28­
32
days
after
treatment
(
the
minimum
PHI).
At
the
site
in
British
Columbia
(
BC04),
duplicate
control
and
treated
RAC
samples
were
harvested
20
days
after
treatment,
and
additionally,
duplicate
treated
RAC
samples
were
harvested
at
the
targeted
30­
day
PHI.

The
onion
samples
were
harvested
by
hand,
first
from
the
control
plot,
followed
by
the
treated
plot,
avoiding
plot
boundaries
and
row
ends.
The
onion
roots
were
trimmed,
and
the
dead
leaves
removed
and
discarded
before
sampling.
Each
green
onion
RAC
sample
weighed
a
minimum
of
4­
5
lb
and
consisted
of
a
minimum
of
24
onion
plants,
with
two
exceptions
(
the
samples
from
the
trial
conducted
in
Quebec
(
QC04)
weighed
approximately
2­
3
lb,
and
the
samples
harvested
20
days
after
treatment
at
the
trial
in
BC04
weighed
1.3­
1.5
lb).
Sufficient
material
was
available
for
residue
analysis
in
both
cases.

All
RAC
samples
were
put
into
labeled,
plastic­
lined
cloth
bags,
and
were
transported
Dimethenamid­
p
Summary
of
Analytical
Chemistry
and
Residue
Data
Barcode:
D318282
7
  
8
immediately
from
the
field
to
a
freezer
or
were
placed
in
coolers
in
the
field
until
they
were
transported
to
a
freezer.
All
green
onion
RAC
samples
were
stored
frozen
( ­
11
º
C)
within
4
hours
of
harvest
and
were
later
shipped
via
ACDS
freezer
truck,
or
overnight
courier
(
on
dry
ice)
to
the
analytical
laboratory.

Residues
of
dimethenamid­
p
were
<
0.01
ppm
LOQ
in/
on
and
at
least
24
green
onion
whole
plant
RAC
samples
harvested
at
a
PHI
of
28­
32
days.
Residues
were
<
0.01
ppm
in/
on
two
additional
green
onion
RAC
samples
harvested
20
days
after
treatment.
The
HAFT
value
for
onion
plants
was
<
0.01
ppm.

The
proposed
use
patterns
are
reflected
in
the
studies.
The
residue
data
are
supported
by
the
storage
stability
studies.
The
analytical
methods
are
adequate
for
the
analysis
of
the
residues
of
concern.
The
residue
data
address
the
appropriate
residues
of
concern.
Dimethenamid­
p
in/
on
leek;
onion,
green;
onion,
Welsh;
and
shallot,
fresh
leaves
at
0.01
ppm
is
supported
by
the
available
residue
data.
Provided
the
petitioner
submits
a
revised
Section
F
with
the
corrected
commodity
terms
listed
above,
ARIA
supports
the
registration
of
permanent
tolerances
for
the
residues
of
dimethenamid­
p
in/
on
the
commodities
previously
mentioned.

860.1520
Processed
Food
and
Feed
Processing
data
for
dry
bulb
onion
are
not
required.

860.1650
Submittal
of
Analytical
Reference
Standards
The
analytical
reference
standards
for
dimethenamid­
p
have
been
submitted
to
the
EPA
National
Pesticide
Standards
Repository.

860.1850
Confined
Accumulation
in
Rotational
Crops
PP#
0E6196,
D304790,
R.
Griffin,
8/
12/
04
The
requirements
for
confined
accumulation
in
rotational
crops
are
satisfied.
An
adequate
confined
rotational
crop
study
was
reviewed
by
the
Agency.
The
study
includes
data
on
winter
wheat
planted
141
days
after
treatment
(
DAT),
lettuce
planted
322
DAT,
and
carrots
planted
332
DAT.
The
maximum
concentration
of
any
metabolite/
degradate
in
harvested
wheat
was
0.01
ppm
for
the
sulfoxide
of
thiolactic
acid
conjugate.
Based
on
these
data,
HED
concluded
that
a
4­
month
rotational
interval
is
adequate
for
fall­
seeded
cereal
grains
and
other
crops
may
be
planted
the
following
spring.
The
current
use
directions
specify
that
treated
areas
may
be
replanted
at
any
time
with
crops
which
have
dimethenamid
tolerances.

860.1900
Field
Accumulation
in
Rotational
Crops
Based
on
the
results
from
the
confined
accumulation
study,
limited
rotational
crop
field
trials
are
not
required.
Dimethenamid­
p
Summary
of
Analytical
Chemistry
and
Residue
Data
Barcode:
D318282
8
  
8
860.1550
Proposed
Tolerances
Dimethenamid­
p,
(
RS)­
2­
chloro­
N­[(
1­
methyl­
2­
methoxy)
ethyl]­
N­(
2,4­
dimethylthien­
3­
yl)
acetamide
is
the
residue
to
be
regulated
in/
on
leek;
onion,
green;
onion;
Welsh;
and
shallot,
fresh
leaves
under
40
CFR
§
180.464(
a).
There
are
no
established
Codex,
Mexican,
or
Canadian
maximum
residue
limits
for
dimethenamid
in/
on
onion.

TABLE
5.
Tolerance
Summary
for
Dimethenamid­
p
Commodity
Established/
Proposed
Tolerance
(
ppm)
Recommended
Tolerance
(
ppm)
Comments
(
correct
commodity
definition)

Onion,
green
0.01
0.01
Leek
0.01
0.01
Onion,
Welsh
0.01
0.01
Spring
onion,
Scallions,
Japanese
bunching
onion
Shallot,
fresh
leaves
0.01
0.01
Green
shallots
Template
Version
November
2003
