UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
MEMORANDUM
DATE:
April
9,
2002
SUBJECT:
Tebuthiuron
Residue
Chemistry
Chapter
for
the
Tolerance
Reassessment
Eligibility
Decision
(TRED);
PC
codes
105501;
DP
Barcode
D277103.

FROM:
Sheila
Piper,
Chemist
Chemistry
and
Exposure
Branch
Health
Effects
Division
(7509C)

THROUGH:
F.
B.
Suhre,
Branch
Senior
Scientist
Chemistry
and
Exposure
Branch
Health
Effects
Division
(7509C)

TO:
Paula
Deschamp,
Risk
Assessor
Reregistration
Branch
II
Health
Effects
Division
(7509C)

and
Wilhelmena
Livingston,
Chemical
Review
Manager
Special
Review
Branch
Special
Review
and
Reregistration
Division
(7508C)

The
Tolerance
Reassessment
Eligibility
Document
(TRED)
for
tebuthiuron
has
undergone
secondary
review
in
the
branch
and
has
been
revised
to
reflect
Agency
policies.

cc:
S.
Piper
(CEB),
RF
RDI:
ChemSAC:
3/
27/
02:
Secondary
Reviewers:
3/
27/
02:
F.
B.
Suhre
4/
8/
02
7509C:
CEB:
CM­
2:
RM
810F:
308­
2717:
Tebuthiuron
2
N
N
S
N
CH
3
CH
3
C
H
3
C
H
3
O
N
H
CH
3
TEBUTHIURON
INTRODUCTION
Tebuthiuron
[N­[
5­(
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]­
N,
N'­
dimethylurea]
is
a
relatively
nonselective,
soil
activated
herbicide
registered
for
use
to
control
broadleaf,
woody
weeds,
grasses,
and
brush
on
terrestrial
feed
crop
sites
(pastures
and
rangeland)
primarily
in
TX,
OK,
and
NM.
Tebuthiuron
is
also
used
on
terrestrial
non­
food
crop
such
as
airports/
landing
fields,
industrial
areas,
non­
agricultural
rights­
of­
way,
fencerows,
hedgerows,
and
non­
agricultural
uncultivated
areas/
soil;
there
is
no
agricultural
crop
use
of
tebuthiuron
except
for
range
and
pasture
land
uses.
Pelleted/
tablets
(P/
T)
is
the
only
tebuthiuron
formulation
class
registered
for
use
on
food/
feed
crops.
The
registered
mode
of
application
is
broadcast
using
ground
or
aerial
equipment
(Source:
LUIS
General
Chemical
Report
for
Tebuthiuron,
5/
20/
92).
There
are
no
registered
residential
uses.

GLN
860.1000:
REGULATORY
BACKGROUND
Tolerances
for
residues
of
tebuthiuron
have
been
established
for
grasses
and
animal
commodities
[40
CFR
§180.390].
These
tolerances
are
expressed
in
terms
of
the
combined
residues
of
N­[
5
(1,
1diemethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]­
N,
N'­
dimethylurea
and
its
metabolites
containing
the
dimethylethyl
thiadiazole
moiety.
Adequate
enforcement
methods
are
available
for
the
determination
of
residues
in/
on
grasses
and
in
animal
tissues
and
milk.

Tebuthiuron
was
first
registered
by
Elanco
Products
Company
in
1974.
The
registration
was
later
transferred
to
DowElanco
(currently
Dow
AgroSciences
LLC)
in
1989.
The
Tebuthiuron
Reregistration
Standard
Guidance
Document
was
issued
7/
87
for
all
pesticide
products
containing
the
active
ingredient,
tebuthiuron.
The
information
contained
in
this
document
outlines
the
Residue
Chemistry
Science
Assessments
with
respect
to
the
reregistration
of
tebuthiuron.

The
summaries
of
residue
chemistry
guidelines
and
topics
listed
below
are
based
on
the
present
regulatory
status
where
the
only
registered
food/
feed
use
of
tebuthiuron
is
on
grasses
grown
in
pasture
and
rangeland.
The
Agency
reserves
the
right
to
require
additional
studies
for
each
applicable
residue
chemistry
guideline
and
topic
if
additional
registrations
on
food/
feed
crops
other
than
pasture
and
rangeland
grasses
are
sought,
or
if
a
tolerance
change
is
proposed.
3
N
N
S
N
CH
3
CH
3
C
H
3
O
N
H
CH
3
OH
N
N
S
NH
2
CH
3
C
H
3
C
H
3
N
N
S
N
CH
3
CH
3
C
H
3
C
H
3
O
NH
2
N
N
S
N
CH
3
CH
3
C
H
3
C
H
3
O
N
H
OH
N
N
S
N
CH
3
CH
3
C
H
3
O
NH
2
OH
N
N
S
N
CH
3
CH
3
C
H
3
O
N
H
OH
OH
N
N
S
N
H
CH
3
C
H
3
C
H
3
O
NH
2
Figure
A.
The
chemical
structures
of
the
metabolites
of
concern
of
tebuthiuron
Structure
Metabolite:
Chemical
name
Structure
Metabolite:
Chemical
name
103
(OH):
N­[
5­(
2­
hydroxy­
1,1­
dimethylethyl)­
1,3,
4
thiadiazol­
2­
yl]­
N,
N'­
dimethylurea
108:
2­
dimethylethyl­
5­
amino­
1,
3,
4­
thiadiazole
104:
N­[
5­(
1,1­
dimethylethyl)­
1,3,
4­
thiadiazol­
2­
yl
N­
methylurea
109:
N­[
5­(
1,1­
dimethylethyl)­
1,3,
4­
thiadiazol­
2­
yl
N'­
hydroxymethyl­
N­
methylurea
104
(OH):
N­[
5­(
2­
hydroxy­
1,1­
dimethylethyl)­
1,
3,
4
thiadiazol­
2­
yl]­
N­
methylurea
A
[109
(OH)]:
N­[
5­(
2­
hydroxy­
1,1­
dimethylethyl
1,3,4­
thiadiazol­
2­
yl]­
N'­
hydroxymethyl­
N­
methylurea
106:
N­[
5­(
1,1­
dimethylethyl)­
1,3,
4­
thiadiazol­
2­
yl]
urea
4
SUMMARY
OF
SCIENCE
FINDINGS
GLN
860.1200:
Directions
for
Use
Based
on
a
search
of
OPP's
REFs
conducted
on
March
22,
2002,
there
are
eight
active
Section
3
registrations
for
end­
use
products
containing
tebuthiuron.
End­
use
formulations
include
granular,
pelleted/
tablets,
and
wettable
powder
products
which
are
applied
using
ground
and
aerial
equipment.
A
summary
of
the
currently
registered
end­
use
products
and
use
sites
is
given
in
the
Table
1
below:

Table
1:
Current
registered
end­
use
products
and
use
sites
Company
EPA
Reg.
No.
Formulation
Class
%
ai
Use
Sites
Rainbow
Technology
Corp
13283­
18
Granular
2
Industrial
areas
(outdoor)
Non­
agricultural
rights­
of
way/
fencerows/
hedgerows
13283­
21
Granular
1
Industrial
areas
(outdoor)
Non­
agricultural
rights­
of
way/
fencerows/
hedgerows
SSI
Maxim
Company,
Inc.
34913­
10
Granular
5
Drainage
systems
Non­
agricultural
uncultivated
areas/
soils
34913­
15
Granular
1
Non­
agricultural
uncultivated
areas/
soils
34913­
16
Granular
2
Non­
agricultural
uncultivated
areas/
soils
Dow
AgroSciences
LLC
62719­
107
Wettable
Powder
80
Drainage
systems
Non­
agricultural
uncultivated
areas/
soils
62719­
121
Pelleted/
Tableted
20
Pasture/
rangeland
Non­
agricultural
uncultivated
areas/
soils
62719­
122
Pelleted/
Tableted
40
Pasture/
rangeland
Non­
agricultural
uncultivated
areas/
soils
The
20%
and
40%
P/
T
formulations
(EPA
Reg.
Nos.
62719­
121
and
62719­
122,
dated
2/
96)
are
registered
for
a
single
broadcast
application
to
rangeland
and
forage
grasses
by
aerial
or
ground
equipment
at
0.
5­
4.
00
lb
ai/
A.
Tebuthiuron
may
be
applied
anytime
but
the
recommended
timing
of
application
is
prior
to
the
resumption
of
active
seasonal
growth
in
the
spring
or
before
expected
seasonal
rainfall.
The
maximum
recommended
rate
is
4.0
lb
ai/
A
for
areas
receiving
>20
inches
average
annual
rainfall,
or
2.0
lb
ai/
A
for
areas
receiving
<20
inches
average
annual
rainfall.
Application
to
ditches
used
to
transport
irrigation
or
potable
water
is
prohibited.
1
MARC
members
(C.
Olinger,
L.
Cheng,
R.
Loranger
and
D.
Nixon)
determined
the
residues
of
concern
in
the
tolerance
expression
should
also
be
included
in
the
risk
assessment.

5
GLN
860.1300:
Nature
of
the
Residue­
Plants
The
qualitative
nature
of
the
residue
in
grasses
is
adequately
understood.
The
registrant
(1976;
MRID
00020756)
submitted
a
"revised"
metabolism
study
in
which
a
[
14
C]
tebuthiuron
solution
(labeled
in
the
5­
position
of
the
thiadiazole
ring;
specific
activity
of
16.
9
uCi/
mg)
was
applied
to
the
surface
of
the
soil
in
which
10­
week
old
tall
fescue
(0.374
lb
ai/
A),
little
bluestem
and
indiangrass
(0.75
lb
ai/
A.)
were
grown.
The
residues
of
concern
are
the
parent
compound
and
its
metabolites
103
(OH),
104,
and
109
(N.
Dodd,
MRIDs
40985001­
02,
6/
22/
89).
MARC
1
revisited
N.
Dodd's
memo,
"Nature
of
the
Residue
in
Milk
and
Bovine
Tissues,"
dated
6/
22/
89
and
determined
the
parent
compound
and
its
metabolites
103
(OH),
104,
and
109
should
also
be
included
in
the
risk
assessment
(3/
28/
02).

Tebuthiuron
was
the
most
abundant
14
C­
residue
recovered
in
the
organosoluble
fraction
of
the
grass
extract.
Other
metabolites
identified
in
the
organosoluble
fraction
from
all
three
grass
species
were
103(
OH),
104,
and
109.
Approximately
39­
86%
of
the
total
14
C­
activity
of
all
grasses
was
identified
from
the
organosoluble
fraction.
The
metabolites
which
were
recovered
and
identified
following
acid
hydrolysis
of
the
aqueous
fraction
were
103(
OH),
104,
and
l04(
OH).
The
predominant
conjugate
in
little
bluestem
was
103(
OH)
while
104
was
the
major
conjugate
in
indiangrass.
One
additional
metabolite,
isopropyl
103,
was
found
in
the
hydrolysates
of
the
aqueous
fraction
of
little
bluestem.
Based
on
the
14
C­
residues
identified
in
the
organosoluble
and
aqueous
fractions,
approximately
81­
89,
58­
70,
and
78­
80%
of
the
total
14
C­
activity
found
in
tall
fescue,
little
bluestem,
and
indiangrass,
respectively,
was
identified.
In
summary,
two
major
metabolic
pathways
are
involved:
N­
demethylation
of
tebuthiuron
to
form
104
and
alkyl
hydroxylation
of
the
dimethylethyl
side
chain
to
form
103(
OH).
The
molecular
structures
of
the
metabolites
of
concern
are
presented
in
Figure
A.

GLN
860.1300:
Nature
of
the
Residue­
Livestock
The
qualitative
nature
of
the
residue
in
milk
and
ruminant
tissues
is
adequately
understood.
The
terminal
residues
of
concern
in
fat,
meat,
kidney,
and
liver
are
tebuthiuron
and
its
metabolites
104,
106,
108,
and
109;
the
terminal
residues
of
concern
in
milk
are
tebuthiuron
and
metabolites
104,
104
(OH),
106,
109,
and
A
[109
(OH)]
for
the
tolerance
expression
and
risk
assessment
(N.
Dodd,
MRIDs
409850­
02,
6/
22/
89).
A
poultry
metabolism
study
is
not
required
since
grasses
are
not
considered
to
be
poultry
feed
items.

A
metabolism
study
was
conducted
on
one
cow
in
the
study
titled
"Nature
of
[
14
C]
Tebuthiuron
Residues
in
Bovine
Tissue"
(J.
D.
Magnussen
and
D.
P.
Rainey,
Ph.
D.,
Experiment
ABC0413,
Lilly
Research
Laboratories,
January
24,
1989,
MRID
No.
409850­
02).
Capsules
containing
[
14
C]
tebuthiuron
labeled
in
the
5­
position
of
the
thiadiazole
ring
were
placed
directly
into
the
rumen
via
a
surgically
fitted
fistula.
The
280
kg
(approximately)
cow
was
given
one
capsule
every
6
12
hours
(morning
and
evening)
for
3
consecutive
days.
Each
capsule
contained
140
mg
[
14
C]
tebuthiuron,
which
the
petitioner
has
calculated
to
be
a
feeding
rate
of
50
ppm.
The
cow
was
sacrificed
12
hours
after
the
final
dose.
The
percentage
of
the
total
radioactivity
which
was
identified
was
82.7
percent
in
fat,
87.2
percent
in
lean,
83.2
percent
in
liver,
and
91.0
percent
in
kidney.
Of
the
total
radioactivity
in
milk,
64.
2
to
68.
1
percent
was
not
conjugated
(i.
e.,
extractable
in
acetonitrile
or
ethyl
acetate).
Between
25.4
and
29.6
percent
were
conjugated
(i.
e.,
polar).
Most
of
the
conjugated
residues
were
released
by
enzyme
or
acid
hydrolysis.
Residues
in
milk
(days
1,
2,
and
3)
as
a
percentage
of
total
radioactivity
were
reported
as
follows:
1.
1
to
1.
2
percent,
parent
(103);
20.7
to
21.6
percent,
104;
21.0
to
26.3
percent,
106;
10.0
to
11.8
percent,
109;
2.2
to
3.
2
percent,
108;
1.0
to
1.
7
percent,
103(
OH);
9.
6
to
16.3
percent,
104(
OH);
7.
6
to
11.8
percent,
Metabolite
A
or
109(
OH);
1.
5
to
7.2
percent,
Metabolite
B;
1.
7
to
2.5
percent,
Metabolite
C;
and
3.
3
to
5.
5
percent,
other.
The
molecular
structures
of
the
metabolites
of
concern
are
presented
in
Figure
A.

GLN
860.1340:
Residue
Analytical
Methods
­
Plants
and
Livestock
An
adequate
method
is
available
for
the
enforcement
of
plant
commodity
tolerances.
A
GLC
method
with
flame
photometric
detection
is
designated
as
Method
II
in
PAM
Vol.
II.
Tebuthiuron
and
metabolites
104
and
109
are
thermally
degraded
on
the
GLC
column
and
are
determined
as
5­(
1,
1­
dimethylethyl)­
N­
methyl­
1,
3,
4­
thiadiazol­
2­
amine;
metabolite
103
(OH)
is
determined
as
5­(
2­
hydroxy­
1,
1­
dimethylethyl)­
N­
methyl­
1,
3,
4­
thiadiazol­
2­
amine.
The
stated
detection
limits
are
0.
1
ppm
for
tebuthiuron
and
metabolites
104
and
109,
and
0.
2
ppm
for
metabolite
103
(OH).
A
revised
enforcement
method
for
milk,
to
include
hydrolysis
steps
and
the
determination
of
metabolites
104
(OH)
and
A
[109
(OH)],
and
a
revised
enforcement
method
for
animal
tissues,
to
include
hydrolysis
steps
and
the
determination
of
metabolite
108,
were
submitted.

GLN
860.1380:
Storage
Stability
The
available
storage
stability
data
indicate
that
residues
of
tebuthiuron
and
its
metabolites
containing
the
thiadiazole
moiety
[103
(OH),
104,
and
109]
are
stable
for
up
to
ca.
29
months
of
frozen
storage
at
­20
C
in/
on
grass
forage
and
hay.
Tebuthiuron
and
its
metabolites
104,
104(
OH),
109,
109(
OH),
and
106
are
stable
in
milk
stored
frozen
for
up
to
6
months.
These
data
are
translated
to
meat
and
stability
data
for
metabolite
108
(not
found
in
milk)
will
not
be
required.
The
stability
data
fully
support
the
ruminant
feeding
study
and
no
additional
data
are
required
(S.
Funk,
D223089,
11/
22/
95).
7
GLN
860.1400:
Water,
Fish
and
Irrigated
Crops
Tebuthiuron
is
presently
not
registered
for
direct
use
on
potable
water
and
aquatic
food
and
feed
crops;
therefore,
no
residue
chemistry
data
are
required
under
these
guideline
topics.

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

GLN
860.1480:
Magnitude
of
the
Residue
in
Meat,
Milk,
Poultry
and
Eggs
The
reregistration
requirements
for
data
depicting
magnitude
of
the
residue
in
milk,
eggs,
and
livestock
tissues
are
fulfilled.
The
registrant
submitted
animal
feeding
study
to
reassess
the
adequacy
of
established
tebuthiuron
tolerances
on
animal
commodities.
A
summary
of
the
animal
feeding
data
relative
to
the
maximum
theoretical
dietary
burden
of
tebuthiuron
to
beef
cattle
and
dairy
cattle
are
included
in
this
document.

Maximum
Theoretical
Dietary
Burden
An
acceptable
ruminant
feeding
study
(S.
Funk,
D217379,
12/
05/
95)
has
been
submitted.
The
results
of
the
ruminant
feeding
study
conducted
at
a
nominal
45
ppm
tebuthiuron
feeding
level
(1.
5x)
for
28
days
show
that
the
existing
tolerances
for
milk
and
meat
are
inadequate
and
that
they
should
be
revised.
The
tolerances
for
meat
and
fat
may
be
lowered,
but
the
tolerances
for
milk
and
meat
byproducts
must
be
increased
as
follows:

Commodity
Existing
Tolerance
1
(40
CFR
§
180.390)
Revised
Tolerance
1
Milk
0.
3
0.
8
Ruminant
2
,fat
2
1.
0
Ruminant
2
,
mbyp
2
5.0
Ruminant
2
,
meat
2
1.0
1
The
tolerance
is
expressed
in
terms
of
tebuthiuron
and
its
metabolites
containing
the
dimethyethyl
thiadiazole
moiety.
2
Separate
tolerances
are
established
for
cattle,
goats,
horses,
and
sheep.

The
feeding
study
have
demonstrated
a
transfer
of
tebuthiuron
to
livestock
tissue
(meat,
meat
byproducts
etc.).
A
dietary
burden
reflecting
theoretical
maximum
exposures
to
tebuthiuron
for
8
beef
cattle
(extrapolating
to
goats,
sheep
and
horse)
was
based
on
reevaluated
tolerances
for
grass
forage
and
grass
hay,
10
ppm
each.

Table
2:
Maximum
Ruminant
Dietary
Burden
for
Tebuthiuron
Commodity
Tolerance
(ppm)
%DM
a
Beef
Cattle
Dairy
Cattle
%Diet
a
Concentration
b
(ppm)
%Diet
a
Concentration
b
(ppm)

Grass
Forage
10
25
60
24
60
24
Grass
Hay
10
88
60
40
4.5
60
40
4.5
TOTAL
­
­
100
28.5
100
28.5
a
As
per
Table
1
(OPPTS
Guideline
860.1000)
b
Ruminant
contribution=
[tolerance/
%DM]
x
%diet
No
poultry
or
swine
feed
items
are
associated
with
the
registered
uses
on
grass;
therefore,
there
is
no
reasonable
expectation
of
detectable
residues
of
tebuthiuron
and
its
metabolites
in
poultry,
swine,
and
eggs
resulting
from
the
use
patterns
being
considered
for
reregistration.
These
uses
for
poultry,
swine,
and
eggs
can
be
classified
under
Category
3
of
40
CFR§
180.6(
a).

GLN
860.1500:
Magnitude
of
the
Residue
in
Plants
The
20%
and
40%
P/
T
formulations
(EPA
Reg.
Nos.
62719­
121
and
62719­
122,
dated
8/
12/
91)
are
registered
for
a
single
broadcast
application
to
rangeland
and
forage
grasses
by
ground
or
air
equipment
at
0.
5­
4.
00
lb
ai/
A.
Tebuthiuron
may
be
applied
anytime
but
the
recommended
timing
of
application
is
prior
to
the
resumption
of
active
seasonal
growth
in
the
spring
or
before
expected
seasonal
rainfall.
The
maximum
recommended
rate
is
4.0
lb
ai/
A
for
areas
receiving

20
inches
average
annual
rainfall,
or
2.0
lb
ai/
A
for
areas
receiving

20
inches
average
annual
rainfall.
Fresh
grass
samples
were
collected
every
two
weeks
for
the
first
three
months
following
application,
and
monthly
for
the
following
twenty­
one
months
in
order
to
determine
the
maximum
residue
level
that
may
occur
at
anytime
following
application.
Hay
samples
were
collected
up
to
two
years
following
the
application.
The
maximum
combined
residues
found
in/
on
grass
forage
were

9.5
ppm
and
<
8.0
ppm
for
hay
samples
(collected
after
the
first
cutting
in
the
following
season
and
then
after
the
next
two
cuttings).
Application
to
ditches
used
to
transport
irrigation
or
potable
water
is
prohibited.
Treated
grasses
may
not
be
cut
for
hay
for
livestock
feed
for
one
year
after
treatment.
The
Agency
considers
restrictions
against
the
grazing
of
treated
rangeland
to
be
impractical,
and
label
revision
is
required.
9
Currently,
HED's
OPP
Guidelines
860.1000
supports
a
0­
day
crop
field
residue
data
for
grasses
cut
for
grass
forage
and
a
reasonable
interval
before
cutting
for
hay.
Tebuthiuron
was
not
sampled
at
a
0­
day
time­
point
in
the
forage
grass
residue
study
because
sample
timing
was
driven
by
formulation
and
use­
pattern
considerations.
Spike
is
an
extruded
pellet
containing
either
20%
or
40%
active
ingredient.
The
pellets
settle
into
the
grass
and
plant
litter
and
are
difficult
to
find
and
essentially
unavailable
from
a
residue
point
of
view.
On
bare
ground
there
would
be
approximately
1
pellet
per
square
foot
per
pound
of
a.
i.
applied.
Residues
do
not
appear
in
plants
until
the
pellets
have
been
activated
by
rainfall
and
the
active
ingredient
washed
into
surface
soil
where
it
is
taken
up
by
plants
(preferable
until
0.5­
inches
of
rainfall
had
occurred).
The
registrant
adjusted
the
sampling
schedule
within
the
test
area
reflecting
the
maximum
residue
levels
occurring
at
any
time
after
application
were
tested
(N.
Dodd,
DEB
No.
4587,
2/
9/
89).

HED
supports
the
registrant
hay
residue
study
protocol
and
specifically
allowed
hay
sampling
to
begin
1
year
after
application.
Spike
20P
and
40P
are
used
only
for
woody
plant
infestation
(trees
and
brush).
This
will
allow
re­
vegetation
with
desirable
grasses,
but
also
because
the
sparse
grass
in
such
areas
do
not
provide
adequate
nutritional
levels
for
grazing
or
hay
in
that
first
year
(N.
Dodd,
Tebuthiuron
on
Grass
and
Hay,
Memorandum
of
Conference­
4/
6/
89).

All
data
requirements
for
the
magnitude
of
the
residue
in
plants
have
been
evaluated
and
deemed
acceptable.
The
conclusions
regarding
the
reregistration
eligibility
of
tebuthiuron
on
the
crops
listed
in
Table
A
are
based
on
the
use
patterns
registered
by
the
basic
producer,
Dow
AgroSciences
LLC.
When
end­
use
product
DCIs
are
developed
(e.
g.,
at
issuance
of
the
RED),
RD
should
require
that
all
end­
use
product
labels
(e.
g.
MAI
labels,
SLNs
and
products
subject
to
the
generic
data
exemption)
be
amended
such
that
they
are
consistent
with
the
basic
producer
labels.

GLN
860.1520:
Processed
Food/
Feed
No
processed
food/
feed
studies
were
submitted
by
the
registrant.

GLNs
860.1850/
1900:
Confined/
Field
Rotational
Crops
Grasses
in
rangeland
are
not
rotated.
Pastures
on
the
other
hand
can
vary
from
permanent
(>
8
years),
short
term
(2­
4
years),
long
term
(5­
8
years),
as
well
as
temporary
(<
1
year).
A
rotational
pasture
is
one
used
for
a
few
seasons
and
then
plowed
and
planted
to
another
crop.
10
The
Quantitative
Usage
Analysis
for
Tebuthiuron
indicates
that
the
states
with
the
most
acres
treated
are
in
the
Southwest
U.
S.
(TX,
OK,
NM,
and
AZ).
The
grassland
areas
covered
by
these
states
include
the
Southern
Plains
and
the
Southwest
Grasslands.
These
grassland
areas
are
predominately
rangeland
that
contains
perennial
native
or
introduced
grasses,
that
have
been
invaded
by
woody
perennial
weedy
shrubs
which
are
very
difficult
to
control.
Pastures
are
mostly
perennial
grasses
or
legumes;
however,
we
do
not
know
if
there
are
any
significant
pasture
acreage
planted
to
annual
forages
in
this
region.

Therefore,
confined
field
rotational
crop
studies
will
be
conditionally
required
unless
the
registrant
can
provide
information
that
pastureland
in
this
area
is
either
insignificant
in
acreage
or
is
predominantly
perennial
grasses
that
are
not
rotated
annually.
11
Table
A.
Range
and
Pasture
Typical
and
Maximum
Use
Rates
Use
Site
and
Product
Name
Application
Method
and
Equipment
Registrant
Maximum
Application
For
Use
Rate
Parameters
Label
Maximum
Application
Per
Use
Registrant
Typical
Use
Rate
Reflecting
Label
Typical
Use
Rate
Range
and
Pasture
Spike
20P
(20%
pellet)
Broadcast
and
spot
treatment
Applied
by
hand
using
canister
delivery,
ground
and
aerial
application
For
vulnerable
sites,
maximum
application
rate
is
dependent
upon
annual
precipitation:

<20"
in
annual
precipitation:
no
more
than
1
lb
a.
i./
acre
once
every
3
years
>20"
in
annual
precipitation:
no
more
than
2
lbs
a.
i./
acre
once
every
3
years
For
non­
vulnerable
sites,
maximum
application
rate
is
dependent
upon
annual
precipitation:

<20"
in
annual
precipitation
no
more
than
2
lbs
once
every
3
years
and
no
more
than
two
treatments
totaling
6
lbs
a.
i./
acre
in
any
6year
period.

>20"
in
annual
precipitation:
no
more
than
4
lbs
a.
i./
acre
once
every
3
years
and
no
more
than
two
treatments
totaling
6
lbs
a.
i./
acre
in
any
6­
year
period
For
broadcast
treatment,
4
lbs
a.
i./
acre
For
spot
treatment
when
needed,
6
lbs
a.
i./
acre
Typical
application
is
once
every
10­
20
years
1.0­
1.4
lbs
for
oak
use
1.
5
lbs
for
desert
species
0.3­
0.5
lbs
for
sage
NS
(continued;
footnotes
follow)
12
TABLE
B.
RESIDUE
CHEMISTRY
SCIENCE
ASSESSMENTS
FOR
REREGISTRATION
OF
TEBUTHIURON.

GLN
Data
Requirements
Current
Tolerances,
ppm
[40
CFR]
Must
Additional
Data
Be
Submitted?
References
1
860.1300:
Plant
Metabolism
No
2
00020645,
00020756,
00020766
860.1300:
Animal
Metabolism
No
00020648,
00020650,
00020651,
00020652,
00020721,
00020767,
00027805,
00027810,
00041675,
00106080,
40985001­
40985002
3
860.1340:
Residue
Analytical
Methods
See
footnote
4
00020656,
00020740,
00041673,
00094745,
00106080,
PP#
7F1925,
41196901
5
,
43983701
4
,
43983702
4
860.1380:
Storage
Stability
No
6
42630501
7
,
43439301
6
860.1500:
Magnitude
of
the
Residue
in
Plants
Grass
Forage,
Fodder,
and
Hay
Group
Grass,
forage
10
No
00020757,
00020764,
00041671,
00094745,
42630502
7
Grass,
hay
10
No
00020705,
00094745,
42630502
7
860.1520:
Magnitude
of
the
Residue
in
Processed
Food/
Feed
N/
A
860.1480:
Magnitude
of
the
Residue
in
Meat,
Milk,
Poultry,
and
Eggs
No
8
00041673,
00106080
860.1400:
Magnitude
of
the
Residue
in
Fish
N/
A
860.1400:
Nature
and
Magnitude
of
the
Residue
in
Drinking
and
Irrigation
Water
N/
A
860.1460:
Magnitude
of
the
Residue
in
Food
Handling
Establishments
N/
A
860.1550:
Reduction
of
Residues
N/
A
860.1850:
Rotational
Crops
(Confined)
See
footnote
9
TABLE
B.
(continued).

GLN
Data
Requirements
Current
Tolerances,
ppm
[40
CFR]
Must
Additional
Data
Be
Submitted?
References
1
13
1.
Unless
otherwise
noted,
references
were
reviewed
in
the
Residue
Chemistry
Science
Chapter
of
the
Reregistration
Standard
dated
2/
27/
87.

2.
CBRS
No.
2959,
12/
10/
87,
N.
Dodd.

3.
CBRS
No.
4939,
6/
22/
89,
N.
Dodd.

4.
Enforcement
methods
for
milk
and
animal
tissues
have
been
proposed;
independent
laboratory
validation
is
required.
The
registrant
submitted
submission
MRIDs
43983701­
02
which
is
under
reviewed.

5.
Data
pertaining
to
multiresidue
methodology
testing
of
tebuthiuron
and
metabolites
has
been
submitted
and
forwarded
to
FDA
for
review
(M.
Nelson
to
L.
Sawyer,
9/
1/
89).

6.
The
stability
data
fully
supports
the
ruminant
feeding
study,
and
no
additional
data
are
required
(S.
Funk,
CBRS
16937,
11/
22/
95).

7.
CBRS
No.
11314,
D187699,
5/
20/
93,
S.
Funk.

8.
An
adequate
feeding
study
has
been
submitted
(S.
Funk,
D217379,
12/
95).

9.
The
confined
field
rotational
crop
studies
will
be
conditionally
required
unless
the
registrant
can
provide
information
that
pastureland
in
TX,
OK,
and
NM
is
either
insignificant
in
acreage
or
is
predominantly
perennial
grasses
that
are
not
rotated
annually.
860.1900:
Rotational
Crops
(Field)
See
footnote
9
14
TOLERANCE
REASSESSMENT
SUMMARY
HED
has
concluded
that
the
tolerance
expression
for
plants
should
include
tebuthiuron
and
its
metabolites
N­[
5­(
2­
hydroxy­
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]­
N,
N'­
dimethylurea
[103
(OH)],
N­[
5­(
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]­
N­
methylurea
(104),
and
N­[
5­(
1,
1dimethylethyl
1,
3,
4­
thiadiazol­
2­
yl]­
N'­
hydroxymethyl­
N­
methylurea
(109).

The
tolerance
expression
for
livestock
commodities
should
include
tebuthiuron
and
its
metabolites
104,
N­[
5­(
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]
urea
(106),
2­
dimethylethyl­
5­
amino­
1,3,4­
thiadiazole
(108),
and
109.
The
terminal
residues
of
concern
in
milk
are
tebuthiuron
and
metabolites
104,
N­[
5­(
2­
hydroxy­
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]­
N­
methylurea
[104(
OH)],
106,
109,
and
N­[
5­(
2­
hydroxy­
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]­
N'hydroxymethyl
N­
methylurea
[109(
OH)].

The
adequacy
of
the
established
tolerances
for
milk,
and
the
fat,
meat,
and
meat
byproducts
of
cattle,
goats,
hogs,
horses,
and
sheep
were
from
the
results
of
the
ruminant
feeding
study
conducted
at
a
nominal
45
ppm
tebuthiuron
feeding
level
(1.
5x)
for
28
days
(S.
Funk,
D217379,
12/
05/
95).
The
existing
tolerances
for
milk
(0.
3
ppm)
and
meat
byproducts
(2
ppm)
should
be
increased
to
0.
8
ppm
for
milk
and
5
ppm
for
meat
byproducts.
The
tolerance
for
meat
(2
ppm)
and
fat
(2
ppm)
should
be
lowered
to
1
ppm.

Table
C.
Tolerance
Reassessment
Summary
Commodity
Current
Tolerance
(ppm)
Tolerance
Reassessment
(ppm)
Correct
Commodity
Definition
Cattle,
fat
2
1
Cattle,
mbyp
2
5
Cattle,
meat
2
1
Goats,
fat
2
1
Goats,
mbyp
2
5
Goats,
meat
2
1
Horses,
fat
2
1
Horses,
mbyp
2
5
Horses,
meat
2
1
Milk
0.
3
0.
8
Sheep,
fat
2
1
Sheep,
mbyp
2
5
Sheep,
meat
2
1
HED
recommends
that
the
40
CFR
tolerance
expression
under
§180.390
be
modified
as
follows:
15
§
180.390
Tebuthiuron;
tolerances
for
residues
(a)
Tolerances
are
established
for
the
combined
residues
of
the
herbicide
tebuthiuron
N
5­(
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl­
N,
N'­
dimethylurea)
and
its
metabolites
N­[
5
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]­
N­
methylurea,
N­[
5­(
1,
1­
dimethylethyl)­
1,
3,
4thiadiazol
2­
yl]
urea,
2­
dimethylethyl­
5­
amino­
1,3,4­
thiadiazole,
and
N­[
5­(
1,
1dimethylethyl
1,
3,
4­
thiadiazol­
2­
yl]­
N'­
hydroxymethyl­
N­
methylurea
in
or
on
the
following
raw
agricultural
commodities:

Commodity
Parts
per
million
Cattle,
fat
1
Cattle,
mbyp
5
Cattle,
meat
1
Goats,
fat
1
Goats,
mbyp
5
Goats,
meat
1
Horses,
fat
1
Horses,
mbyp
5
Horses,
meat
1
Sheep,
fat
1
Sheep,
mbyp
5
Sheep,
meat
1
(b)
A
tolerance
is
established
for
the
combined
residues
of
the
herbicide
tebuthiuron
N
5­(
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl­
N,
N'­
dimethylurea)
and
its
metabolites
N­[
5
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]­
N­
methylurea,
N­[
5­(
2­
hydroxy­
1,
1dimethylethyl
1,
3,
4­
thiadiazol­
2­
yl]­
N­
methylurea,
N­[
5­(
1,
1­
dimethylethyl)­
1,
3,
4thiadiazol
2­
yl]
urea,
N­[
5­(
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]­
N'­
hydroxymethyl­
Ndimethylurea
and
N­[
5­(
2­
hydroxy­
1,
1­
dimethylethyl)­
1,
3,
4­
thiadiazol­
2­
yl]­
N'hydroxymethyl
N­
methylurea
in
or
on
the
following
raw
agricultural
commodity:

Commodity
Parts
per
million
Milk
0.
8
16
DIETARY
EXPOSURE
ASSESSMENT
A
refined
acute
and
chronic
dietary
exposure
assessment
was
conducted
for
tebuthiuron
registered
for
foliar
application
to
pastures
and
rangeland
(secondary
transfer
to
livestock
commodities).
Anticipated
residues
from
field
trial
data
and
percent
crop
treated
were
utilized
to
estimate
the
dietary
exposure
to
tebuthiuron
in
the
diets
of
the
U.
S.
Population
(chronic)
and
females
13­
50
years
(acute
only)
[S.
Piper,
D281821,
04/
2/
02].

CODEX
HARMONIZATION
No
Codex
MRLs
have
been
established
or
proposed
for
residues
of
tebuthiuron.
Therefore,
issues
of
compatibility
with
respect
to
U.
S.
tolerances
and
Codex
MRLs
do
not
exist.
17
AGENCY
MEMORANDA
CITED
IN
THIS
DOCUMENT
CBRS
No.:
2959
Subject:
EPA
Registration
No.
1471­
101
(RCB
No.
2959)
­
Data
Waiver
or
Amendment
Requested
and
Protocol
Re:
Tebuthiuron
Reregistration
(No
Accession
Number)
From:
N.
Dodd
To:
R.
Taylor
and
Toxicology
Branch
Dated:
12/
10/
87
MRID(
s):
None
CBRS
No.:
None
Subject:
Tebuthiuron
on
Rangelands
and
Pastures­
Protocol
for
Magnitude
of
Residues
Studies
for
Tebuthiuron
Reregistration
(No
Accession
Number)
From:
N.
Dodd
To:
R.
Taylor,
Toxicology
Branch
II
Dated:
2/
9/
89
MRID(
s):
None
CBRS
No.:
None
Subject:[
Multiresidue
methodology
testing
of
tebuthiuron
and
six
of
its
metabolites.]
From:
M.
Nelson
To:
L.
Sawyer,
FDA
Dated:
9/
1/
89
MRID(
s):
41196901
CBRS
No.
:
4939
Subject:
EPA
Registration
No.
1471­
101
(DEB
No.
4939)
­
Tebuthiuron
Reregistration
­
Nature
of
the
Residue
in
Milk
and
Bovine
Tissues.
From:
N.
Dodd
To:
R.
Taylor
and
Toxicology
Branch
II
Dated:
6/
22/
89
MRID(
s):
409850­
01
and
409850­
02.

CBRS
No.:
11235
DP
Barcode:
D187084
Subject:
Tebuthiuron:
Waiver
Request
for
Grazing
Study
and
Grazing
Study
Protocol;
Draft
of
Enforcement
Analytical
Method
for
Milk;
Schedule
for
Meat
and
Milk
Analytical
Methods;
Schedule
for
Feeding
Study.
From:
S.
Funk
To:
P.
Perreault
Dated:
2/
9/
93
MRID(
s):
None
18
CBRS
No.:
11314
DP
Barcode:
D187699
Subject:
Tebuthiuron:
List
A;
Chemical
105501;
Case
0054.
DowElanco
Response
to
the
Registration
Standard
Data
Requirements
for
Grass
Field
Trials
(171­
4(
k))
and
Storage
Stability
for
Forage
and
Hay
(171­
4(
e)).
MRID
Nos.
42630501
and
42630502.
From:
S.
Funk
To:
L.
Rossi/
L.
Propst
Dated:
5/
20/
93
MRID(
s):
42630501
and
42630502
CBRS
No.:
15883
DP
Barcode:
D217379
Subject:
Tebuthiuron:
Ruminant
Feeding
Study
(171­
4
(j)).
From:
S.
Funk
To:
L.
Propst/
K.
Rothwell
Dated:
12/
5/
95
MRID(
s):
43703201
CBRS
No.:
16937
DP
Barcode:
D223089
Subject:
Tebuthiuron
Storage
Stability
in
Support
of
the
Ruminant
Feeding
Study
(171­
4(
e;
j)).
From:
S.
Funk
To:
P.
Deschamp
Dated:
8/
1/
96
MRID(
s):
43439301
CBRS
No.:
None
DP
Barcode:
D281821
Subject:
Tebuthiuron
Acute
and
Chronic
Dietary
Exposure
Assessments
for
the
Tolerance
Reassessment
Eligibility
Decision
(TRED).
From:
S.
Piper
To:
P.
Deschamp/
W.
Livingston
Dated:
4/
2/
02
MRID(
s):
None
