Document ID: EPA-HQ-OPP-2009-0009-0007
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-12-18T05:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF           

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

MEMORANDUM

Date:	  	8/18/09

Subject:		Chlorimuron Ethyl.  Petition for Tolerances on Field Corn and
Soybean with Metabolism Studies on Ruminant and Poultry.  Summary of
Analytical Chemistry and Residue Data.  

PC Code:  128901	DP Barcode:  360845

Decision No.:  400389	Registration No.:  352-436

Petition Nos.:  8F7430 & 8F7439	Regulatory Action:  Section 3

Risk Assessment Type:  NA	Case No.:  NA

TXR No.:  NA	CAS No.:  90982-32-4

MRID Nos.:  43483706, 43517501, & 47548203-04	40 CFR:  180.429

FROM:		W. Cutchin, Acting Senior Branch Scientist 

		Alternative Risk Integration and Assessment (ARIA)

		Risk Integration, Minor Use, and Emergency Response Branch (RIMUERB)

		Registration Division (RD; 7505P)

	Through:	D. McNeilly, Chemist

		C. Swartz, Branch Chief

	Registration Action Branch 2 (RAB2)

	Health Effects Division (HED; 7509P)

	To:	W. Cutchin, Acting Senior Branch Scientist

		ARIA/RIMUERB

		RD (7505P)

Executive Summary

Chlorimuron ethyl [ethyl
2-(4-chloro-6-methoxypyrimidin-2-ylcarbamoylsulfamoyl)

benzoate] is a sulfonylurea herbicide registered for use on peanuts and
soybeans in the U.S. for  the postemergence control of broadleaf weeds
and yellow nutsedge.  Chlorimuron ethyl is formulated as a
water-dispersible granular formulation (WDG) at concentrations ranging
from 8.3-31.8% active ingredient (ai), with end-use products registered
to FMC Corporation, E.I. du Pont de Nemours and Co. (DuPont), and Valent
U.S.A. Corporation.  Tolerances have been established for residues of
chlorimuron ethyl in/on peanuts and soybeans at 0.02 ppm and 0.05 ppm,
respectively [40 CFR §180.429].  

In the current petition, Dupont is proposing use of a 25% WDG
formulation of chlorimuron ethyl (DuPont Classic® Herbicide; EPA Reg.
No. 352-436) on herbicide resistant field corn and soybean for control
of annual grass and broadleaf weeds.  The proposed use is for a single
application at up to 0.0625 lb ai/A either preemergence or
postemergence.  The use directions require the use of an adjuvant:
either a crop oil concentrate at up to 1.0% of the spray volume or
non-ionic surfactant (NIS) at up to 0.25% of the spray volume.  The
proposed preharvest interval (PHI) is 7days for corn.  Applications may
be made no later than flowering (R2 growth stage) to soybeans.  In
conjunction with this use, Dupont is proposing permanent tolerances for
chlorimuron ethyl on the following:

Corn, field, forage	0.5 ppm

Corn, field, grain	0.01 ppm

Corn, field, stover	2.0 ppm

Corn, field, meal	0.014 ppm

Corn, field, flour	0.015 ppm

Corn, aspirated grain fractions	1.28 ppm

Soybean, hay	1.8 ppm

Soybean, forage	0.45 ppm

Soybean, seed	0.01 ppm

Soybean, hulls	0.04 ppm

Soybean, aspirated grain fraction	2.79 ppm

Peanut*	0.02 ppm 

* Listed in Section F, but not as a newly proposed tolerance

Nature of the residue studies are available for chlorimuron ethyl on
peanuts, soybeans, and corn.  For peanuts, the data indicated a lack of
significant translocation of the active ingredient in nutmeats or hulls.
 For soybeans, only parent chlorimuron ethyl was observed.  For corn,
the data indicated a lack of significant translocation of the active
ingredient in grain.  The deficiencies in the corn metabolism study
cited in the last risk assessment remain outstanding.  However, since
the metabolism data for soybean, peanut, and corn are similar, for the
purposes of these petitions, ARIA will consider the residue of concern
to be chlorimuron ethyl per se.  Resolution of the deficiencies of the
corn metabolism study is a condition of registration for these
petitions.

Ruminant and poultry metabolism studies were submitted with this
petition.  For ruminants, the data from urine and feces and the milk and
tissue data indicate that chlorimuron ethyl is absorbed and rapidly
excreted by goats primarily as parent via the urine.  In addition,
chlorimuron ethyl is also metabolized by oxidative dechlorination of
parent or metabolites, cleavage of the ethyl ester, and hydrolytic
cleavage of the amide linkage.  The presence of chlorimuron ethyl thiol
in urine also suggests that parent may undergo conjugation with
glutathione, with subsequent degradation of the glutathione moiety.  For
poultry, parent was identified as a major residue in eggs and all
tissues, and the pyrimidine amine and sulphonamide metabolites were
detected in eggs.  Sulphonamide was also detected in skin and muscle.
The available data suggest that the primary route of metabolism for
chlorimuron ethyl in poultry involves cleavage of the sulfonylurea
bridge to yield the pyrimidine amine and sulphonamide metabolites. 
Since very low residues are expected in livestock, exaggerated doses
were used in the metabolism studies, and considering the low toxicity of
the parent and by analogy the metabolites, ARIA and HED will consider
chlorimuron ethyl as the residue of concern (ROC) in livestock. 
Resolution of the deficiencies of the ruminant and poultry metabolism
studies is a condition of registration for these petitions. 

Adequate methods are available for tolerance enforcement. The
enforcement method for soybeans (AMR-459-85) is found in Pesticide
Analytical Manual (PAM) Volume II.  Residues are determined by high
performance liquid chromatography (HPLC) using a photoconductivity
detector with a method limit of quantitation (LOQ) of 0.01 ppm.  An HPLC
with ultraviolet detector (HPLC/UV) method is also available for peanuts
(AMR-990-87).  Corn and soybean samples in the submitted residue field
trials and processing studies were analyzed for chlorimuron ethyl using
a liquid chromatography method with tandem mass spectroscopy/ mass
spectroscopy (LC/MS/MS) method, DuPont-13412, Revision No. 1.  This
method has been proposed as a new tolerance enforcement method for
residues of sulfonylureas, and has an independent laboratory validation
(ILV) trial.  For each corn and soybean commodity the LOQ and the limit
of detection (LOD) are 0.01 ppm and 0.003 ppm, respectively.  The method
is adequate for data collection.

At this time, detectable residues are not expected in livestock
commodities; therefore, an enforcement method for residues of
chlorimuron ethyl in livestock is not required.

The registrant submitted interim data from a 10-month storage stability
study on field corn commodities.  The data show that residues of
chlorimuron ethyl are stable on soybean and corn commodities for the
duration of the residue and processing studies.

The registrant submitted field trial data supporting the use of
chlorimuron ethyl on field corn that is tolerant to sulfonylurea
herbicides.  In a total of 23 field trials, chlorimuron ethyl was
applied to field corn as a single broadcast foliar application at 0.06
lb ai/A at either 7 days prior to normal forage harvest , 7 days prior
to grain harvest, or at growth stage R1-R2.  All applications were made
using ground equipment and included the use of a non-ionic surfactant. 
In residue decline trials, chlorimuron ethyl residues in/on forage from
showed a rapid decline in residues within the first 7 days after
treatment.  Thereafter, residues in forage declined more slowly and were
generally <0.02 ppm within 21 days of treatment.  ARIA recommends for
the requested tolerances of 0.01 ppm in/on field corn grain, 0.5 ppm
in/on field corn forage, and 2.0 ppm in/on field corn stover.

The registrant submitted field trial data supporting the use of
chlorimuron ethyl on soybeans that are tolerant to sulfonylurea
herbicides.  In a total of 23 field trials, chlorimuron ethyl was
applied to soybeans as a single broadcast foliar application at 0.06 lb
ai/A at growth stage R1-R2 (the proposed use) or approximately 7 days
prior to normal seed harvest.  All applications were made using ground
equipment, and included the use of a non-ionic surfactant.  In the
majority of trials, samples of forage and hay were harvested on the day
of application followed by seed harvest at normal maturity.  In the
remainder of the field trials, seeds were harvested 5-8 PHI.  For both
forage and hay, chlorimuron ethyl residues declined rapidly within the
first week after application and then declined more slowly thereafter. 
Although the residue data support a 0.01 ppm tolerance for soybean
seeds, there is an existing 0.05 ppm tolerance for chlorimuron ethyl on
soybeans that harmonizes with the current Canadian MRL for soybeans. 
The existing soybean tolerance will cover the proposed use.  A revised
Section F should be submitted removing the requested change in the
soybean seed tolerance.

Rather than a 0-day PHI as supported by the submitted data, the
registrant is requesting a 14-day PHI for forage and hay. Based on the
data from the residue decline studies, the rate constant from the
decline curve with the longest rate of decline was used to extrapolate
possible residue values for soybean forage and hay at the proposed
14-day PHI.  The extrapolated 14-day residue values for forage and hay
support the requested tolerances.  ARIA recommends for the requested
tolerances of 0.45 ppm in/on soybean forage and 1.8 ppm in/on soybean
hay.  

There are livestock feed items of regulable interest associated with
these petitions.  For cattle, using the reasonably balance dietary
burdens (RBD) and the highest total radioactive residues (TRR) from the
ruminant metabolism study, the highest residues expected in cattle would
be 0.002 ppm in liver and 0.004 ppm in milk. For poultry, using the RBD
and the highest TRR, the highest residues expected in poultry would be
0.002 ppm in eggs.  At the levels calculated for cattle and poultry
above, there would be no detectable residues of chlorimuron ethyl
expected in livestock commodities.  Detectable residues of chlorimuron
ethyl are also not expected in hogs. Therefore, tolerances and feeding
studies are not required for livestock at this time.  

The available corn and soybean processing data for chlorimuron ethyl are
adequate.  As residues did not concentrate in corn grits, starch or
refined oil, separate tolerances are not required for these corn
commodities.  Based on the highest average field trial (HAFT) residues
for corn grain and the processing factors for meal and flour from the
exaggerated rate processing study, the maximum expected residues in corn
meal and flour would be less than 0.02 ppm.  Since the tolerance on the
RAC, field corn grain, is set at the method LOQ (0.01 ppm) and the
suggested tolerances on corn meal and flour are less than 2x the LOQ,
tolerances on those processed commodities are not required.  A revised
Section F should be submitted removing the requested tolerances on field
corn meal and flour.  

For soybeans, residues did not concentrate in meal or refined oil;
therefore separate tolerances are not required for these processed
fractions.  Based on the HAFT residues for soybeans (0.01 ppm) and the
processing factor for hulls, the maximum expected residues in hulls are
0.035 ppm.  As this level of residues is below the current 0.05 ppm
tolerance for soybean seeds, a separate tolerance is also not required
for soybean hulls.  A revised Section F should be submitted removing the
requested tolerance on soybean hulls.

 

Chlorimuron ethyl residues were shown in concentrate in aspirated grain
fractions (AGF) from both corn grain (120x) and soybean seeds (279x). 
Based on the HAFT residues of field corn grain (0.01 ppm) and soybean
seeds (0.01 ppm), the maximum expected residues in AGF would be 1.2 ppm
for corn grain and 2.79 ppm for soybean seeds.  As residues in soybean
AGF are higher than for corn grain, the tolerance for AGF should be set
at 3.0 ppm based on the soybean residue data.  A revised Section F for
the residues of chlorimuron ethyl in aspirated grain fractions at 3.0
ppm is required.  The requests for separate soybean and corn AGF should
be removed from the revised Section F.

An analytical standard for chlorimuron ethyl is currently available in
the National Pesticide Standards Repository.

Due to the insignificant residues (<0.01 ppm) detected in the confined
rotational crop study, trials for field accumulation in rotational crops
are not required.   The rotational crop restrictions on the product
label are adequate.

  SEQ CHAPTER \h \r 1 Regulatory Recommendations and Residue Chemistry
Deficiencies

Resolution of the deficiencies of the corn metabolism study as described
in the last residue chemistry review is a condition of registration for
these petitions (PP# 6E7153, DP# 361368, K. Middleton, 2/5/09).

The goat metabolism study is not adequate and additional information is
required on the duration of sample storage prior to extraction and
analysis, along with any data supporting the stability of 14C-resdiues
in milk and tissues during frozen storage. 

The poultry metabolism study is not adequate and the following specific
deficiencies were noted in the study: 

Due to the small size of the fat and skin subsamples (~0.1 g) used for
radioassay, the LODs for fat and skin samples were too high (0.02-0.03
ppm).

The dates of sample extraction and analysis were not reported.

No supporting storage stability data were provided although samples may
have been stored frozen for up to 8 months prior to analysis. 

Details were not provided on the recovery of radioactivity through the
various extraction procedures.

Only the identities of parent and sulphonamide were confirmed by LC-MS.

A major unknown in egg yolks (34-48% TRR; 0.011-0.023 ppm) and liver
(40-69% TRR; 0.040-0.204 ppm) was not adequately identified.  The
unknown was organosoluble and contained an intact sulfonylurea bridge.

A revised Section F should be submitted removing the requested change in
the soybean seed tolerance.

A revised Section F should be submitted removing the requested
tolerances on field corn meal and flour.  

A revised Section F should be submitted removing the requested tolerance
on soybean hulls.

 

A revised Section F for the residues of chlorimuron ethyl in aspirated
grain fractions at 3.0 ppm should be submitted.  The requests for
separate soybean and corn AGF should be removed from the revised Section
F.

Provided the above deficiencies are resolved, ARIA recommends for
establishing a permanent tolerance for residues of chlorimuron ethyl as
described in Table 19.  A human health risk assessment for chlorimuron
ethyl is forthcoming.

Background

Chlorimuron ethyl is a sulfonylurea herbicide registered for use on
peanuts and soybeans in the U.S. for the postemergence control of
broadleaf weeds and yellow nutsedge.  It is formulated as a WDG at
8.3-31.8% ai.  For peanuts, chlorimuron ethyl may be applied as a
postemergence broadcast, banded or low volume application at up to
0.0117 lb ai/A/season.  For soybeans, chlorimuron ethyl may be applied
early-preplant, preplant, postplant, preemergence, postemergence, or
postharvest as either a broadcast, banded or low volume application at
up to 0.01172-0.0803 lb ai/A/season.  The PHIs are 45 days for peanuts
and 60 days for soybean.

Dupont has submitted petitions (PP#8F7430 & 8F7439) supporting the use
of chlorimuron ethyl on herbicide tolerant field corn and soybeans for
the control of annual grasses and broadleaf weeds.  The nomenclature and
physicochemical properties of chlorimuron ethyl are presented below in
Tables 1 and 2.

Table 1.	Chlorimuron ethyl Nomenclature.

Compound	

Common name	Chlorimuron ethyl

Company experimental name	DPX-F6025

IUPAC name	ethyl 2-(4-chloro-6-methoxypyrimidin-2- ylcarbamoylsulfamoyl)
benzoate

CAS name	ethyl
2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]
benzoate

CAS registry number	90982-32-4

End-use product (EP)	25% WDG; DuPont CLASSIC® Herbicide (EPA Reg. No.
352-436)

Table 2.	Physicochemical Properties of Chlorimuron ethyl.

Parameter	Value	Reference

Melting point/range	181°C	PP#3G2959; 1/10/84; S. Creeger

pH	4.4

	Density	1.51 g/ml

	Water solubility (mg/L)	pH 1.3 = 1.5

pH 1.9 = 1.5

pH 2.5 = 1.5

pH 4.2 = 4.1

pH 5.0 = 9.0

pH 5.8 = 99

pH 6.5 = 450

pH 7.0 = 1200

	Solvent solubility (mg/100 mL at 25°C)	Acetone = 7.05

Acetonitrile = 3.10

Benzene = 0.815

Ethyl Acetate = 2.36

Ethyl Alcohol = 0.392

n-Hexane = 0.006

Methyl Alcohol = 0.740

Methylene Chloride = 15.3

Xylene = 0.283

	Vapor pressure (25°C)	1.5 x 10-5 mm Hg 

	Dissociation constant, pKa (25°C)	4.2

	Octanol/water partition coefficient, Log(KOW)	1.3

	UV/visible absorption spectrum	Not available

	

860.1200  Directions for Use

There are currently 16 end-use products containing chlorimuron ethyl
registered in the U.S.  These products are all WDG formulations
containing 8.3-31.8% of chlorimuron ethyl.  Two products are registered
to FMC Corporation, 12 products are registered to DuPont, and 2 products
are registered to Valent U.S.A. Corporation.

Dupont is proposing use of a 25% WDG formulation of chlorimuron ethyl
(Classic® Herbicide; EPA Reg. No. 352-436) on field corn and soybeans
for control of annual grasses and broadleaf weeds.  This formulation is
currently registered to DuPont for use on soybeans, peanuts and noncrop
areas.  An example supplemental label for this formulation was provided,
and the proposed use directions are summarized below in Table 3.

Table 3.	Summary of Proposed Directions for Use of Chlorimuron ethyl.

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

Field Corn (OPTIMUM® GAT® herbicide tolerant)

Broadcast foliar application pre- or post-emergence or burndown	25% WDG

[352-436]	0.0045-0.06	1	0.06	7	Include a crop oil concentrate or NIS.

Apply in a minimum of 10 gal/A by ground, 3 gal/A by air

Soybean (OPTIMUM® GAT® herbicide tolerant)

Broadcast foliar application pre- or post-emergence or burndown	25% WDG

[352-436]	0.0045-0.06	1	0.06	NA	Include a crop oil concentrate or NIS.

Apply no later than R2 growth stage.  Allow 14 days after application
before grazing or feeding forage or hay. Apply in a minimum of 10 gal/A
by ground, 3 gal/A by air

Conclusions:  The proposed use directions are adequate and are supported
by available field trial data.

860.1300 Nature of the Residue - Plants

Plant metabolism studies on soybeans and peanuts were summarized in a
previous risk assessment (DP# 301317, R. Griffin, 8/31/04).  Soybean
plants in the first to third trifoliate leaf stage were sprayed with
[14C-phenyl] or [14C-pyrimidine-2]chlorimuron ethyl at a rate of 0.031
lbs ai/A.  Plants were sampled on 0, 19, and 35 days after treatment
(DAT) and mature beans were harvested at 103 DAT. Only parent compound
chlorimuron ethyl was observed in the plant wash (94-100%).  Growth
chamber studies were also submitted in which cut soybean plants were
immersed in solutions of [14C]chlorimuron ethyl for several hours to 2
days. These studies resulted in the identification of the following
metabolites: chlorimuron ethyl homoglutathione conjugate, chlorimuron
ethyl acid, pyrimidine amine, desmethyl pyrimidine amine, and saccharin.
Considering the low level of residues in/on mature soybeans expected
from the use on soybeans (6-7 metabolites equivalent to a total of <0.02
ppm chlorimuron ethyl), HED did not require further work to identify the
metabolites comprising the terminal radioactive residues.

In a greenhouse metabolism study, peanuts were treated with [14C-phenyl]
and [2-14C-pyrimidine]chlorimuron ethyl at 0.031 lb ai/A, 60 days prior
to harvest. The data indicated a lack of significant translocation of
the active ingredient.  Less than 1% of the total radioactive residues
(extractable and unextractable) were found in either nutmeats or hulls,
and over 99% of the radioactivity was present in vines at harvest.  The
total radioactive residues were found to be about 0.02 and 0.05 ppm in
nutmeat and hulls, respectively.  The extractable residues in nut meats
are between 51-63% of the TRR, whereas those in the corresponding hulls
are 54-75%. The identified metabolites constitute <15-28% and 29-33% of
the total radioactive residues in peanut nutmeats and hulls,
respectively.  

A previously submitted corn metabolism study was reviewed in conjunction
with a petition for uses on cranberry and low-growing berry (PP# 6E7153,
DP# 361368, K. Middleton, 2/5/09).  The variety used in the corn
metabolism study, Pioneer 3377IR (43483707, A. Parmar, 1/6/08), is
identified as being resistant to acetolactate synthase (ALS) inhibitors
which includes sulfonylureas (Weed Technology, 1995, 9:696-702).  Based
on the corn metabolism study, the overall metabolic pathway involves
cleavage of the sulfonylurea linkage to yield the corresponding
sulfonamide and pyrimidine amine, and hydroxylation of the parent to
yield 4-hydroxy-chlorimuron ethyl.  The fate of chlorimuron ethyl was
consistent in both pre- and postemergence treatments.  The results were
similar to those of the peanut and soybean metabolism studies which were
previously reviewed (PP#8F3694, DEB# 4691, H. Fonouni, 2/7/89 and
PP#5F3186, C. Deyrup, 12/16/85).

There were deficiencies cited in the last risk assessment which remain
outstanding: (1) for the corn metabolism study the petitioner should
provide the dates of sample extraction and analysis to confirm that the
majority of the immature samples were initially analyzed within ~6
months of harvest; and (2) confirmatory data should be submitted to
validate that these samples were analyzed within ~6 months of harvest. 
This information has not as yet been submitted.

Conclusions:  Based on the similar metabolism in corn (tolerant) and
soybeans and peanuts (likely not done with tolerant varieties), for the
purposes of these petitions, ARIA and HED will consider chlorimuron
ethyl as the residue of concern (ROC) in plants (email, R. Loranger,
7/15/09).  Resolution of the deficiencies of the corn metabolism study
is a condition of registration for these petitions.

860.1300 Nature of the Residue - Livestock

Ruminants

43483706, W. Cutchin, in process

In a ruminant metabolism study, two British Saanen goats were dosed
orally via capsule twice a day for three consecutive days with either
[14C-2-pyrimidinyl] (PYR) or [14C-U-phenyl] (PH) chlorimuron ethyl at a
dose of 20 mg ai/goat/day.  This dose level was equivalent to 0.30 and
0.36 mg ai/kg body weight/day for the 14C-PYR and 14C-PH labels,
respectively, or 9.99 and 10.02 ppm of chlorimuron ethyl in the diet. 
Samples of milk were collected twice a day and urine, feces and cage
washes were collected daily.  Goats were sacrificed within 23 hours of
the final dose, and samples of kidney, liver, fat (omental and renal)
and muscle (hind and fore quarter) were collected from each goat.  All
samples were stored at -20°C until analysis.

The recovery of the administered dose was 95-102% for both14C-labels,
with the majority of the dose being recovered in the urine (73.5-80.6%)
and feces (20.2-21.0%).  Only minor amounts of the dose were recovered
in milk (0.11-0.49%) and edible tissues (0.02-0.11%).  Levels of TRRs in
milk were somewhat erratic over time for both 14C-labels, but did not
appear to increase over time.  TRR levels in milk were 0.011-0.069 ppm
for the 14C-PYR-label and 0.002-0.063 ppm for the 14C-PH-label, and
maximum TRR levels in milk were observed in the 54-hr and 30-hr samples
for 14C-PYR and 14C-PH labels, respectively.  The TRR levels in tissues
were similar for the two 14C-labels with the exception of liver.  For
the 14C-PYR goat, TRR levels were 0.005 ppm in muscle, 0.011 ppm in fat,
0.036 ppm in kidney and 0.056 ppm in liver.  For the 14C-PH goat, TRR
levels were 0.004 ppm in muscle and liver, 0.014 ppm in fat, and 0.055
ppm in kidney.

Table 4. 	Total Radioactive Residues in Milk, Excreta and Tissues from
Goats Dosed Orally with [14C-PYR] or [14C-PH] Chlorimuron Ethyl at
Levels Equivalent to 10 ppm in the Diet.

Matrix	Sampling

interval	[14C-PYR]	[14C-PH]

% AD	ppm	% AD	ppm

Milk	Day 1 (6h)	0.03	0.038	0.008	0.011

	Day 1 (24h)	0.120	0.048	0.011	0.005

	Day 2 (30h)	0.012	0.011	0.051	0.063

	Day 2 (48h)	0.113	0.048	0.011	0.005

	Day 3 (54h)	0.058	0.069	0.010	0.012

	Day 3 (72h)	0.138	0.050	0.013	0.005

	Day 4 (78h)	0.023	0.022	0.002	0.002

	Total	0.49	--	0.11	--

Fat	Day 4	<0.001	0.011	<0.001	0.014

Muscle 	Day 4	<0.001	0.005	<0.001	0.004

Liver	Day 4	0.097	0.056	0.006	0.004

Kidney	Day 4	0.010	0.036	0.013	0.055

All tissues (% AD)	Day 4	0.11	--	0.02	--

Urine	Day 1	24.2	3.809	28.0	4.889

	Day 2	24.3	2.797	25.8	3.704

	Day 3	25.1	3.936	26.8	6.635

	Total	73.5	--	80.6	--

Feces	Day 1	3.7	2.113	6.6	4.149

	Day 2	7.2	3.776	5.4	3.220

	Day 3	9.3	5.105	9.0	4.225

	Total	20.2	--	21.0	--

Total Excreta	Day 1	27.9	--	34.6	--

	Day 2	31.5	--	31.2	--

	Day 3	34.4	--	35.8	--

	Total	93.7	--	101.6	--

Cage wash	Day 1	0.391	0.274	0.249	0.166

	Day 2	0.196	0.163	0.026	0.143

	Day 3	0.149	0.093	0.296	0.179

	Total	0.74	--	0.57	--

Recovered Dose (%AD)

95.1	--	102.3	--

Due to low levels of 14C-residues in milk and tissues, only the
following samples were extracted for analysis: milk (72-hr), kidney and
liver from the 14C-PYR goat, and kidney from the 14C-PH goat. 
Composited samples (Days 1-3) of urine and feces from both goats were
also extracted and analyzed to profile residues.

Solvent extraction of the above milk and tissue samples released 75-100%
of the TRR, and radioactivity remaining in the residual solids accounted
for <0.02 ppm in each matrix.  Extracted 14C-residues were cleanup up
and profile by thin layer chromatography (TLC) and HPLC, and the
identities of selected compounds were confirmed by liquid chromatography
with mass spectroscopic detector (LC-MS).  

HPLC and LC-MS analyses of the milk extract tentatively identified the
metabolites dechloro-pyrimidine amine and/or demethoxy-pyrimidine amine
as accounting for 89% of the TRR in milk.  However, these polar
metabolites could not be separated by either the HPLC or LC-MS analyses.
 In addition, trace amounts of parent (0.3% TRR) were identified in milk
by LC-MS.  HPLC analysis of the 14C-PYR liver extract, identified parent
(62% TRR) as the major 14C-residue and also detected an Unknown present
at low concentrations (14% TRR; <0.01 ppm).  In kidneys from the
[14C-PYR] goat, radioactivity was comprised primarily of parent (47%
TRR) and an Unknown with a retention time (Rt) of 75 min (38% TRR; 0.015
ppm).  However, in kidneys from the [14C-PH] goat, only trace amounts of
parent (1% TRR) were detected, and the extracted radioactivity was
comprised primarily of dechloro-chlorimuron ethyl (14% TRR),
sulphonamide (31% TRR) and chlorimuron acid (30% TRR).  Two minor
unknowns were also detected at 12 and 6% of the TRR (≤0.007 ppm).

For both 14C-labels, HPLC and LC-MS analyses of urine identified parent
as the major residue (32-45% TRR) along with minor amounts of
chlorimuron ethyl thiol (8-10% TRR).  The other major 14C-component in
urine was a single peak of polar residues eluting at the solvent front
(47-53% TRR).  

Analyses of fecal extracts identified dechloro chlorimuron ethyl
(8.5-9.2% TRR) from both 14C-labels, along with the hydrolytic cleavage
products pyrimidine amine (15% TRR) and sulphonamide (16% TRR) from the
14C-PYR and 14C-PH labels, respectively.  Parent compound was not
detected in feces.  The major 14C-residues in feces from both 14C-labels
were comprised of several unknown polar components that together
accounted for 26-33% of the TRR.  There were also two unknowns with Rts
of 23 and 32 min that were present in feces from both 14C-labels, and
which respectively accounted for 11-12% and 6-8% of the TRR.  Enzymatic
and acid treatment of the urine and fecal extracts did not yield any
additional information on the nature of the unknown components.

The data from the two 14C-labels were similar and indicate that the
primarily route of excretion and metabolism of chlorimuron ethyl in
goats appears to involve the direct excretion of parent compound via the
urine.  The identification of chlorimuron acid and dechloro chlorimuron
ethyl in kidneys and urine also indicates that parent can undergo
cleavage of the ethyl ester and oxidative dechlorination.  Chlorimuron
ethyl also may undergo hydrolytic cleavage of the amide linkage to form
the sulphonamide and pyrimidine amine metabolites, which can be either
excreted directly or further degraded to more polar metabolites, such as
dechloro-pyrimidine amine and demethoxy pyrimidine amine.  The
identification of chlorimuron ethyl thiol in urine also suggests that
parent may undergo conjugation with glutathione, with subsequent
degradation of the glutathione moiety. 

Table 5. 	Distribution of 14C-Residues in Milk, Liver and Kidney from a
Goat Dosed Orally with [14C-PYR]Chlorimuron Ethyl at Levels Equivalent
to 10 ppm in the Diet. 1

Metabolite Fraction	Kidney	Liver	Milk (72-hr)

	TRR= 0.036 ppm	TRR= 0.056 ppm	TRR = 0.050 ppm

	%TRR	ppm	%TRR	ppm	%TRR	ppm

Hexane/ acidic methanol extracts  (HPLC analysis)	97	0.035	75	0.042

Chlorimuron ethyl	47	0.017	62	0.035

Unknown Rt 72 min	--	--	13	0.007

Polar Unknown Rt 2 min	8	0.003	--	--

Unknown Rt 75 min	38	0.015	--	--

Silica gel cleanup of milk sample 

(HPLC and LC-MS analyses)

	100	0.05

Chlorimuron ethyl

	0.3	0.002

Dechloropyrimidine amine/ demethoxy pyrimidine amine

	89.2	0.045

Unextractable residues	3	0.001	25	0.014	--	--

1	Shading indicates that the extraction step and/or characterization
analysis was not conducted for the matrix in question.

Table 6. 	Distribution of 14C-Residues in Kidney from a Goat Dosed
Orally with [14C-PH]Chlorimuron Ethyl at Levels Equivalent to 10 ppm in
the Diet.

Metabolite Fraction	Kidney

	TRR= 0.055

	%TRR	ppm

Hexane/ acidic methanol	95	0.052

Chlorimuron ethyl	1	<0.001

Dechloro DPX F6025	14	0.008

Sulphonamide	31	0.017

DPX F6025 Acid	30	0.016

Unidentified (Rt 18)	12	0.007

Unidentified (Rt 40)	6	0.003

Unextractable residues	1	0.001

The proposed metabolic pathway for chlorimuron ethyl in the dairy goat
is shown below in Figure 1.  The high level of parent compound detected
in the urine indicates that chlorimuron ethyl is readily absorbed and
excreted without additional modification.  The identification of
chlorimuron acid and dechloro chlorimuron ethyl in kidneys and urine
indicates that parent can also undergo cleavage of the ethyl ester and
oxidative dechlorination.  The data from kidneys and feces also indicate
that parent may undergo hydrolytic cleavage of the amide linkage to form
the sulphonamide and pyrimidine amine metabolites, which can be either
excreted directly or further degraded to more polar metabolites, such as
dechloro-pyrimidine amine and demethoxy pyrimidine amine, which were
tentatively identified in milk.  The presence of chlorimuron ethyl thiol
in urine also suggests that parent may undergo conjugation with
glutathione with subsequent degradation of the glutathione moiety.

Figure   SEQ Figure \* ARABIC  1 .  Proposed Metabolic Profile of
Chlorimuron Ethyl in Lactating Goats

Ruminant Conclusions:   Although identification of 14C-residues in milk
and tissues was limited due to the low levels of TRR (<0.07 ppm), the
additional analyses of urine and feces provided sufficient information
to adequately characterize the metabolism of [14C] chlorimuron ethyl in
goats.  However, before the goat metabolism study can be deemed
adequate, additional information is required on the duration of sample
storage prior to extraction and analysis, along with any data supporting
the stability of 14C-residues in milk and tissues during frozen storage.

Of the samples that were extracted and analyzed, 62-76% of the TRR was
identified in kidneys, 62% of the TRR was identified in liver, and 89%
of the TRR was tentatively identified in milk.  Parent was identified as
a major residue in kidney and liver, and the chlorimuron acid,
dechloro-chlorimuron ethyl, and sulphonamide were also identified in
kidney.  Dechloro-pyrimidine amine and/or demethoxy-pyrimidine amine
were also tentatively identified as the major component(s) in milk.  

In conjunction with the data from urine and feces, the milk and tissue
data from both 14C-labels indicate that chlorimuron ethyl is absorbed
and rapidly excreted by goats primarily as parent via the urine.  In
addition, chlorimuron ethyl is also metabolized by oxidative
dechlorination of parent or metabolites, cleavage of the ethyl ester,
and hydrolytic cleavage of the amide linkage.  The presence of
chlorimuron ethyl thiol in urine also suggests that the parent may
undergo conjugation with glutathione, with subsequent degradation of the
glutathione moiety.

Poultry

43517501, W. Cutchin, in process

In a poultry metabolism study, two groups of Hisex laying hens (5
hens/group) were dosed orally for seven consecutive days with either
[14C-2-pyrimidinyl] (PYR) or [14C-U-phenyl] (PH) chlorimuron ethyl at a
dose of 1.46 and 1.32 mg ai/hen/day, respectively.  This dose level was
equivalent to 0.30 and 0.36 mg ai/kg body weight/day for the 14C-PYR and
14C-PH labels, respectively, or 9.75 and 9.13 ppm of chlorimuron ethyl
in the diet.  Samples of eggs were collected twice a day and excreta
were collected daily.  The hens were sacrificed 23 hours after the final
dose, and samples of cage wash, skin with attached fat, peritoneal fat,
muscle (breast and thigh) and liver were collected from each hen.  All
samples were stored at -20°C until analysis.

The recovery of the administered 14C-dose averaged 79.2% from the
14C-PYR hens and 84.1% from the 14C-PH hens, with the majority of the
dose being recovered in the excreta (77.0-82.3% dose).  Only minor
amounts of the dose were recovered in tissues (0.08-0.24% dose) and eggs
(0.85-0.97% dose).   The TRR in egg whites and yolks were generally
similar for the two 14C-labels, but TRR levels in tissues were 2-3x
higher for the 14C-PH hens than for the 14C-PYR hens.  TRR levels in egg
whites were 0.186-0.581 ppm for the 14C-PYR hens and 0.187-0.361 ppm for
the 14C-PH hens.  TRR levels in egg whites were somewhat erratic over
time, but peaked on Days 4-5 for both 14C-labels.  TRR levels in egg
yolks were considerably lower than in egg whites for both the 14C-PYR
hens (0.016-0.085 ppm) and the 14C-PH hens (0.012-0.036 ppm), and
increased slowly during dosing, reaching maximum levels on Days 6 and 7.
 For the 14C-PYR hens, TRR levels in tissues averaged 0.021 ppm in skin
w/fat, <0.02 ppm in fat, <0.01 ppm in muscle, and 0.099 ppm in liver. 
For the 14C-PH hens, TRR levels in tissues averaged 0.052 ppm in skin
w/fat, <0.03 ppm in fat, 0.025 ppm in muscle, and 0.296 ppm in liver.

Table 7. 	Recovery of Total Administered 14C-Dose in Excreta, Eggs and
Tissues from Hens Dosed Orally for 7 Days with [14C-PYR] or [14C-PH]
Chlorimuron Ethyl at Levels Equivalent to 9.75 and 9.13 ppm in the Diet,
respectively.

Matrix	Sampling

≤0.01	0.01	<0.01	<0.01

	Day 3	≤0.01	0.01	≤ 0.01	<0.01

	Day 4	0.01	0.01	<0.01	<0.01

	Day 5	0.01 - 0.02	0.01	<0.01	<0.01

	Day 6	0.01 - 0.02	0.01	≤0.01	<0.01

	Day 7	0.01	0.01	≤0.01	0.01

	Total	0.05 - 0.08	0.06	0.02 - 0.03	0.02

Skin w/fat	Day 8	0.01	0.01	0.01 - 0.04	0.02

Muscle 	Day 8	0.01	0.01	0.01 - 0.02	0.01

Liver	Day 8	0.03 - 0.04	0.03	0.04 - 0.15	0.07

Kidney	Day 8	0.03 - 0.04	0.03	0.03 - 0.31	0.14

All tissues	Total	0.07 - 0.09	0.08	0.09 - 0.52	0.24

Recovered Dose (%)	77.65 - 81.06	79.16	80.96 - 90.46	84.10

Composited samples of excreta (Days 1-7) from both groups were extracted
and analyzed to profile residues.  Analyses of extracts from excreta of
both 14C-labels detected the following compounds:   dechloro-chlorimuron
ethyl (3.2-5.8% TRR), chlorimuron acid (3.5-4.5% TRR), pyrimidine amine
(11.9% TRR), demethoxy- and/or dechloro-pyrimidine amine (8.6% TRR),
sulphonamide (13.1% TRR) and saccharin (12.2% TRR).  No parent compound
was detected in excreta.  The remaining radioactivity in excreta was
comprised 7 major unknowns, each accounting for 7.1-18.4% of the TRR,
and several minor unknowns (each <5 % TRR).  Enzymatic and acid
treatment of the excreta extracts did not yield any additional
information on the nature of the unknown components.

Table 8. 	Total Radioactive Residues (ppm) in Eggs and Tissues from Hens
Dosed Orally for 7 Days with [14C-PYR] or [14C-PH] Chlorimuron Ethyl at
Levels Equivalent to 9.75 and 9.13 ppm in the Diet, respectively.

Matrix	Sampling

interval	[14C-PYR] Label 1

101F	102F	103F	104F	105F	Average 2

Egg Whites	Day 1	0.276	0.263	0.094	0.038	0.257	0.186

	Day 2	0.157	0.286	0.402	1.312	0.279	0.487

	Day 3	0.095	0.310	0.270	1.097	0.088	0.372

	Day 4	0.157	0.255	0.230	0.110	0.352	0.221

	Day 5	0.617	0.264	0.255	1.254	0.509	0.580

	Day 6	0.071	0.241	0.322	1.034	0.285	0.391

	Day 7	0.459	0.297	0.351	 NS	0.274	0.345

Egg Yolks	Day 1	0.016	0.023	0.013	0.007	0.019	0.016

	Day 2	0.024	0.034	0.043	0.098	0.031	0.046

	Day 3	0.034	0.067	0.042	0.085	0.033	0.052

	Day 4	0.055	0.051	0.057	0.061	0.062	0.057

	Day 5	0.084	0.067	0.067	0.139	0.069	0.085

	Day 6	0.065	0.074	0.076	0.140	0.072	0.085

	Day 7	0.080	0.077	0.079	NS 	0.079	0.079

Skin w/fat	Day 7	<0.02	<0.02	<0.02	0.023	<0.02 	0.021

Fat	Day 7	<0.02	<0.02	<0.02	<0.02	<0.02 	<0.02

Muscle	Day 7	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01

Liver	Day 7	0.095	0.108	0.099	0.083	0.109	0.099

Matrix	Sampling

interval	[14C-PH] Label 1

201F	202F	203F	204F	205F	Average 2

Egg Whites	Day 1	0.029	0.035	0.219	0.252	0.398	0.187

	Day 2	0.528	0.338	0.141	0.245	0.425	0.335

	Day 3	0.158	0.348	0.606	0.247	0.419	0.356

	Day 4	0.292	0.405	0.501	0.229	0.380	0.361

	Day 5	0.364	0.213	0.085	0.256	0.122	0.208

	Day 6	0.030	0.188	0.588	0.288	0.343	0.287

	Day 7	0.094	0.371	0.432	0.033	0.513	0.289

Egg Yolks	Day 1	0.008	0.008	0.016	0.012	0.016	0.012

	Day 2	0.015	0.012	0.011	0.013	0.010	0.012

	Day 3	0.012	0.018	0.032	0.014	0.019	0.019

	Day 4	0.023	0.020	0.025	0.022	0.023	0.023

	Day 5	0.025	0.024	0.021	0.023	0.021	0.023

	Day 6	0.022	0.031	0.036	0.030	0.031	0.030

	Day 7	0.046	0.026	0.038	0.043	0.026	0.036

Skin w/fat	Day 7	0.092	0.072	<0.03	0.038	<0.03 	0.052

Fat	Day 7	<0.03	<0.03	<0.03	<0.03	<0.03	<0.03

Muscle	Day 7	0.053	0.027	 <0.015	 <0.015	 <0.015	0.025

Liver	Day 7	0.660	0.403	0.085	0.270	0.064	0.296

1	Actual LODs for the 14C-PYR and 14C-PH labels were respectively 0.003
and 0.003 ppm for egg whites, 0.007 and 0.008 ppm for egg yolks, 0.02
and 0.03 ppm for skin, 0.02 and 0.03 ppm fat, 0.01 and 0.015 ppm for
muscle, and 0.010 and 0.015 ppm for liver.

2	For calculating average 14C-resdiues, the LOD was used for samples
with 14C-resdiues <LOD.  NS = No sample.

Based on the TRR levels, the following samples were extracted for
analysis: composited samples of egg whites (Days 5 and 6), yolks (Days 4
and 7) and liver (all hens) from the 14C-PYR hens; composited samples of
egg whites (Days 4 and 5), yolks (Days 4 and 5), skin (3 hens), muscle
(2 hens), and liver (all hens) from the 14C-PH hens.  

Solvent extractions released 83-99% of the TRR from egg and tissue
samples, and radioactivity remaining in the residual solids accounted
for <0.04 ppm in each matrix.  Extracted 14C-residues were cleaned up
and profiled by TLC and HPLC, and the identities of selected compounds
were confirmed by LC-MS.  

Three major components were detected in egg yolks from both 14C-labels. 
In yolks from the 14C-PYR hens, parent accounted for 29% of the TRR
(0.020 ppm) and pyrimidine amine accounted for 29% of the TRR (0.020
ppm).  In yolks from the 14C-PH hens, parent accounted for 13% of the
TRR (0.003 ppm) and sulphonamide accounted for 26% of the TRR (0.006
ppm).  A major Unknown (Rt 30 min) was also detected at 34-48% of the
TRR (0.011-0.023 ppm) in yolk from both 14C-labels, indicating that the
unknown contained an intact sulfonylurea bridge.  In egg whites, parent
was the only major component for both 14C-labels, accounting for 84-93%
of the TRR (0.240-0.454 ppm).  Minor amounts of pyrimidine amine (3.3%
TRR) and sulphonamide (2.5% TRR) were also detected in egg whites, along
with one minor unknown (2.7% TRR).

The 14C-residue profile was similar in liver for both 14C-labels, with
parent accounting for 20.9-42.4% of the TRR (0.042-0.062 ppm) and an
Unknown (Rt 33 min) accounting for 40-69% of the TRR (0.040-0.204 ppm). 
This unknown has an intact sulfonylurea bridge as it was present in
liver from both 14C-labels.  The unknown was labile to acid hydrolysis,
but it did not degrade into any known metabolites, and it was not
identified by LC-MS.  Based on its HPLC retention time, it was
tentatively identified as 5-hydroxy chlorimuron acid.

In skin from the 14C-PH hens, parent accounted for 39% of the TRR (0.026
ppm) and sulphonamide accounted for 16% of the TRR (0.011 ppm), and the
remaining 14C-residues consisted of 3 to 4 unknowns each accounting for
<10% of the TRR.  In muscle from the 14C-PH hens, parent was also
identified as the major component, accounting for 78% of the TRR (0.031
ppm), along with traces amounts (≤0.002 ppm) of sulphonamide,
4-hydroxy chlorimuron ethyl, and several minor unknowns.

Table 9. 	Distribution of 14C-Residues in Egg Yolks and Whites from Hens
Dosed Orally with [14C-PYR] and [14C-PH]Chlorimuron Ethyl at Levels
Equivalent to 9.75 and 9.13 ppm in the Diet, respectively.

Fraction/Metabolite	[14C-PYR] Egg Yolk (Days 4 and 7)	[14C-PH]  Egg Yolk
(Days 4 and 5)

	TRR = 0.068 ppm	TRR =  0.023 ppm

	%TRR	ppm	%TRR	ppm

MeOH/acidic MeOH  (HPLC analysis)	94.1	0.064	82.6	0.019

Chlorimuron ethyl	29.4	0.020	13.0	0.003

Pyrimidine amine	29.4	0.020	ND	--

Sulphonamide	ND	--	26.1	0.006

Unknown Rt 29-30 min	33.5	0.023	47.8	0.011

Unextractable residues	5.9	0.004	17.4	0.004

Fraction/Metabolite	[14C-PYR] Egg whites (Days 5 and 6)	[14C-PH] Egg
whites (Days 4 and 5)

	TRR = 0.486 ppm	TRR = 0.285 ppm

	%TRR	ppm	%TRR	ppm

EtOAc/acidic EtOAc/EtOAC:ethanol (HPLC analysis)	99.0	0.483	87.0	0.248

Chlorimuron ethyl	93.4	0.454	84.2	0.240

Pyrimidine amine	3.3	0.016	ND	--

Sulphonamide	ND	--	2.5	0.007

Unknown Rt 32 min	2.7	0.013	ND	--

Unextractable residues	0.6	0.003	13.0	0.037

Table 10.	Distribution of 14C-Residues in Tissues from Hens Dosed Orally
with [14C-PYR] and [14C-PH]Chlorimuron Ethyl at Levels Equivalent to
9.75 and 9.13 ppm in the Diet, respectively.

Fraction/Metabolite	[14C-PYR] Liver	[14C-PH] Liver

	TRR = 0.099 ppm	TRR =  0.296 ppm

	%TRR	ppm	%TRR	ppm

MeOH/acidic MeOH  (TLC and HPLC analysis)	82.8	0.082	90.2	0.267

Chlorimuron ethyl	42.4	0.042	20.9	0.062

5-Hydroxy chlorimuron (Rt 33-34 min) 1	40.4	0.040	68.9	0.204

Unextractable residues	17.2	0.017	9.8	0.029

Fraction/Metabolite	[14C-PH] Skin w/fat

	TRR = 0.067 ppm

	%TRR	ppm

MeOH/acidic MeOH

(TLC and HPLC analyses)	91.0	0.061

Chlorimuron ethyl	38.8	0.026

Sulphonamide	16.4	0.011

Several Minor Unknowns 

(each <10% TRR and <0.01 ppm)	31.3	0.021

Unextractable residues	9.0	0.006

Fraction/Metabolite	[14C-PH] Muscle

	TRR = 0.040 ppm

	%TRR	ppm

ammonium acetate buffer/EtOAc 

(TLC and HPLC analyses)	98.0	0.039

Chlorimuron ethyl	77.5	0.031

Sulphonamide	5.0	0.002

4-OH DPX F6025	<2.5	<0.001

Two Minor Unknowns 	5.0	0.002

Unextracted	2.5	0.001

Table 11.	Distribution of 14C-Residues in Excreta from Hens Dosed Orally
with [14C-PYR] or [14C-PH] Chlorimuron Ethyl for 7 Days at Levels
Equivalent to 9.8 and 9.1 ppm in the Diet.

Fraction/ Metabolite	[14C-PYR] Excreta

(77.1% AD)	[14C-PH] Excreta

 (82.3% AD)

	%AD	%TRR 1	%AD	% TRR 1

MeOH/acidic MeOH (HPLC analysis)	77.1	~100	82.3	~100

Dechloro DPX F6025	4.4	5.8	2.6	3.2

Chlorimuron acid	3.5	4.5	2.9	3.5

Pyrimidine amine	9.2	11.9	ND	--

Demethoxy pyrimidine amine/

dechloro pyrimidine amine	6.6	8.6	ND	--

Sulphonamide	ND	--	10.8	13.1

Saccharin	ND	--	10.0	12.2

HPLC Unknowns: 2

Polar unknown(s) Rt <1 min	5.7	7.3	3.2	3.9

Unknown Rt 10 min	3.8	4.9	ND	--

Unknown Rt 19.3 min	7.3	9.5	ND	--

Unknown Rt 24 min	11.4	14.8	6.8	8.3

Unknown Rt 29 min	14.2	18.4	ND	--

Unknown Rt 31 min	ND	--	10.1	12.3

Unknown Rt 34.5 min	ND	--	10.9	13.2

Unknown Rt 44 min	ND	--	5.8	7.1

Unknown Rt 47 min	ND	--	7.2	8.8

Minor unknowns (each <5%TRR)	11.0	14.3	11.9	14.4

Unextractable residues	<0.1	<0.1	<0.1	<0.1

1	TRR data were calculated by the reviewer based on chromatographic
data.

2	The 14C-residues were reported to be stable under enzymatic
hydrolysis, but degraded to unknown polar compounds following acid
hydrolyses.

The data from the two 14C-labels were similar and indicate that the
primarily route of metabolism for chlorimuron ethyl in hens appears to
involve cleavage of the sulfonylurea bridge to yield the pyrimidine
amine and sulphonamide metabolites, which are then further degraded to
more polar metabolites.  The parent can also undergo cleavage of the
ethyl ester to form chlorimuron acid and oxidative dechlorination to
form dechloro-chlorimuron ethyl.  There was also some evidence for
direct hydroxylation of the parent compound. The proposed metabolic
pathway for chlorimuron ethyl in the poultry is shown below in Figure 2.
 Based on the major metabolites identified in eggs, tissues and excreta,
the metabolism of chlorimuron ethyl in poultry primarily involves
cleavage of the sulfonylurea bridge to yield the pyrimidine amine and
sulphonamide metabolites, which are further degraded to more polar
metabolites.  Parent also can undergo cleavage of the ethyl ester to
form chlorimuron acid and oxidative dechlorination to form
dechloro-chlorimuron ethyl. 

 

Figure 2.  Proposed Metabolic Profile of Chlorimuron Ethyl in Laying
Hens.

Poultry Conclusions:   The poultry metabolism study is not adequate. 
There was a general lack of supporting raw data related to the
extraction and analysis of samples, and the following specific
deficiencies were noted in the study: 

Due to the small size of the fat and skin subsamples (~0.1 g) used for
radioassay, the LODs for fat and skin samples were too high (0.02-0.03
ppm).

The dates of sample extraction and analysis were not reported.

No supporting storage stability data were provided although samples may
have been stored frozen for up to 8 months prior to analysis. 

Details were not provided on the recovery of radioactivity through the
various extraction procedures.

Only the identities of parent and sulphonamide were confirmed by LC-MS.

A major unknown in egg yolks (34-48% TRR; 0.011-0.023 ppm) and liver
(40-69% TRR; 0.040-0.204 ppm) was not adequately identified.  The
unknown was organosoluble and contained an intact sulfonylurea bridge.

Of the samples that were extracted and analyzed, 39-59% of the TRR was
identified in egg yolks, 87-97% of the TRR was identified in egg whites,
20-42% of the TRR was identified in liver, 55% of the TRR was identified
in skin, and 83% of the TRR was identified in muscle.  Parent was
identified as a major residue in eggs and all tissues, and the
pyrimidine amine and sulphonamide metabolites were detected in eggs. 
Sulphonamide was also detected in skin and muscle. 

 

Although the study is inadequate, the available data suggest that the
primary route of metabolism for chlorimuron ethyl in poultry involves
cleavage of the sulfonylurea bridge to yield the pyrimidine amine and
sulphonamide metabolites.

Nature of the Residue - Livestock Conclusions:  Since very low residues
are expected in livestock, exaggerated doses were used in the metabolism
studies, and considering the low toxicity of the parent and by analogy
the metabolites, ARIA and HED will consider chlorimuron ethyl as the ROC
in livestock (email, R. Loranger, 7/15/09).  Resolution of the
deficiencies of the ruminant and poultry metabolism studies is a
condition of registration for these petitions. 

860.1340 Residue Analytical Methods

Plant Enforcement Methods

Two HPLC methods are available for enforcing tolerances of chlorimuron
ethyl. The original enforcement method for soybeans (AMR-459-85) is
found in PAM Volume II.  For this method, residues are extracted with
dichloromethane, filtered, diluted with water, and concentrated to an
aqueous remainder.  The aqueous fraction is partitioned against hexane,
discarding the hexane phase, and residues are then partitioned into
dichloromethane and cleaned up using a silica gel cartridge.  Residues
are concentrated to dryness and redissolved in HPLC mobile phase
(hexane/isopropanol/methanol /glacial acetic acid/water;
750:125:125:2:1).  Residues are then determined by HPLC using a
photoconductivity detector.  The method LOQ is 0.01 ppm.

An HPLC/UV method is also available for peanuts (AMR-990-87).  This
method differs slightly from the above method primarily in the use of
different solvents for the sample preparation step.  The method LOQ is
0.02 ppm for peanut nutmeat and 0.05 ppm for peanut hulls.

Data Collection Methods

47548201, W. Cutchin, in process

47548202, W. Cutchin, in process

Plants

Corn and soybean samples were analyzed for chlorimuron ethyl using an
LC/MS/MS method, DuPont-13412, Revision No. 1, “Analytical Method for
the Determination of Nicosulfuron, Thifensulfuron Methyl,
Ethametsulfuron Methyl, Rimsulfuron, Tribenuron Methyl, and Chlorimuron
ethyl in Oil Crop Matrices Using SPE Purification and LC/MS/MS
Detection.”  This method has been proposed as a new tolerance
enforcement method for residues of sulfonylureas, and an independent
laboratory validation trial for this method has been previously reviewed
(DP# 330813, S. Hummel, 8/8/06).

 

→186.  The LOQ for each corn and soybean commodity is 0.01 ppm and the
LOD is 0.003 ppm.

The method was validated in conjunction with the analysis of the field
corn trial samples using control samples fortified with chlorimuron
ethyl at 0.01-2.0 ppm for forage and fodder (whole plants), 0.01-3.0 ppm
for stover, and 0.01-0.10 ppm for grain. The method was validated in
conjunction with the analysis of the soybean field trial samples using
control samples fortified with chlorimuron ethyl at 0.01-15 ppm for
forage, 0.01-30 ppm for hay, 0.01-0.4 ppm for seeds.

Conclusions:  There are adequate methods available for tolerance
enforcement for corn and soybean.  The method used for data collection
for corn and soybean commodities is adequate.   

Livestock

At this time, no detectable residues (<0.01 ppm) are expected in
livestock commodities; therefore, an enforcement method for residues of
chlorimuron ethyl in livestock commodities is not required.

860.1360 Multiresidue Methods

Multiresidue method testing data are available for chlorimuron ethyl
(PAM, Vol. I, Appendix I).  Chlorimuron ethyl is poorly recovered (<50%)
through Method 302 and not recovered through Method 303.

860.1380 Storage Stability

43483708, W. Cutchin, in process

DuPont submitted interim data (10-month) from a 24-month storage
stability study on field corn commodities.  For the study, duplicate
control samples of field corn forage, grain and stover were fortified
with chlorimuron ethyl at 0.25 ppm and placed in glass bottles in
storage at -20 ± 5°C.  Samples of each corn matrix were analyzed
immediately after fortification (0-day) and after 2, 8 and 10 months of
frozen storage.  Duplicated stored samples were analyzed at each
interval, along with a freshly fortified control sample and an untreated
control sample.

 

Samples were analyzed for chlorimuron ethyl residues using a HPLC/UV
method (Method No. AMR 2713-93, Revision No. 1).  The method was
adequately validated in conjunction with analysis of the stored samples.
 For this method, residues were extracted from each corn matrix with
0.03 M K2HPO4:acetonitrile (90:10, v:v) and cleaned up by elution
through a C8 extraction disc.  Residues were then analyzed by HPLC/UV
using column switching.  The reported LOQ is 0.025 ppm for each corn
commodity.

Table 12.	Stability of  Chlorimuron ethyl in Field Corn Forage, Grain
and Stover at -20(C.

Commodity	Spike Level

(ppm)	Storage Interval (months)	Recovered Residues (ppm)	Mean Recovered
Residues (ppm)	Mean Recovery

(%)	Corrected 1 Recovery  (%)

Field Corn Grain	0.25	0	0.18, 0.13	0.16	64	100

2	0.20, 0.17	0.18	74	84

8	0.17, 0.17	0.17	68	106

10	0.18, 0.18	0.18	72	90

Field Corn Forage	0.25	0	0.18, 0.18	0.18	72	100

2	0.18, 0.23	0.20	82	102

8	0.17, 0.16	0.16	66	82

10	0.21, 0.18	0.20	78	103

Field Corn Stover	0.25	0	0.19, 0.20	0.20	76	100

2	0.16, 0.16	0.16	76	84

8	0.17, 0.17	0.17	72	94

10	0.17, 0.17	0.17	60	113

1	Corrected for mean concurrent recovery (see Table C.1.).

The corrected recoveries from each matrix showed no decline over the 10
months of frozen storage (Figure C.1).  From 0 to 10 months, the
corrected recoveries from stored frozen samples were 84-106% from grain,
82-103% from forage and 84-113% from stover (Table 12).   

Table 13.	Summary of Storage Conditions and Durations of Samples from
Crop Field Trials.  

Matrix 	Storage Temperature   (°C)	Actual Storage Duration (months)
Interval of Demonstrated Storage Stability  (months)

Corn Fodder	-20	12.2	10

Corn Forage

10.9

	Corn Stover

10.5

	Corn Grain

11.3

	Corn AGF	-20	<1	N/A

Corn Starch

<1

	Corn Grits

<1

	Corn Flour

<1

	Corn Refined oil (wet)

<1

	Corn Refined oil (Dry)

<1

	Corn Meal

<1

	Soybean Meal	-20	<1	N/A

Soybean Hulls

<1

	Soybean Refined oil

<1

	Soybean AGF

<1

	

Conclusions:  These interim data indicate that chlorimuron ethyl is
stable in corn forage, grain and stover stored at -20°C for up to 10
months.  Average corrected recoveries were 103% from forage, 90% from
grain, and 113% from stover after 10 months of storage at -20°C.  The
data show that residues of chlorimuron ethyl are stable on soybean and
corn for the duration of the magnitude of the residue studies.

860.1400 Water, Fish, and Irrigated Crops

There are no proposed uses that are relevant to this guideline topic.

860.1460 Food Handling

There are no proposed uses that are relevant to this guideline topic.

860.1480 Meat, Milk, Poultry, and Eggs

There are livestock feed items of regulable interest associated with
these petitions: field corn grain, forage, stover, and
milled-by-products; soybean seed, meal, hulls, forage, hay, and silage;
and aspirated grain fractions.

For cattle, the RBD are determined to be 0.44 ppm for beef cattle and
0.75 ppm for dairy cattle (See Table 14).  The highest TRR found in the
submitted metabolism study were in liver at 0.056 ppm and milk at 0.5
ppm from goats fed at a dietary burden of 10 ppm.  Using the RBD and the
highest TRR, the highest residues expected in cattle would be 0.002 ppm
in liver (0.056 ppm TRR from 10 ppm dose with 0.44 ppm RBD) and 0.004
ppm in milk (0.05 ppm TRR from 10 ppm dose with 0.75 ppm RBD).   

For poultry, the RBD is determined to be 0.02 ppm (See Table 14).  The
highest TRR found in the submitted metabolism study was in eggs from
hens fed at a dietary burden of 9.75 ppm.  Using the RBD and the highest
TRR, the highest residues expected in poultry would be 0.002 ppm in eggs
(0.068 ppm TRR from 9.75 ppm dose with 0.2 ppm dietary burden).  

Table 14.  Reasonably Balanced Dietary Burdens (RBDs) of Chlorimuron
Ethyl Residues 

                 for Livestock.

Feedstuff	Type 1	% Dry Matter 2	% Diet 3	Tolerance (ppm)	Dietary
Contribution (ppm) 4

Beef Cattle R 15%, CC 80%, PC 5%

Corn, field, stover	R	83	10	2.0	0.24

Aspirated grain fractions	R	85	5	3.0	0.18

Corn, field, grain	CC	88	80	0.01	0.009

Soybean, meal	PC  	92	5	0.05	0.0027

Total Burden

	100

0.44

Dairy Cattle R 45%, CC 45%, PC 10%

Corn, field, stover	R	83	15	2.0	0.36

Corn, field, forage	R	40	30	0.5	0.38

Corn, field, grain	CC	88	45	0.01	0.0051

Soybean, meal	PC  	92	10	0.05	0.0055

Total Burden

	100

0.75

Poultry CC 75%, PC 25%

Corn, field, grain	CC	88	75	0.01	0.0075

Soybean, meal	PC  	92	25	0.05	0.0125

Total Burden

	100

0.02

Swine CC 85%, PC 15%

Corn, field, grain	CC	88	85	0.01	0.0085

Soybean, meal	PC  	92	15	0.05	0.0075

Total Burden

	100

0.016

1  R: roughage; CC:  carbohydrate concentrate;  PC:  protein concentrate

2  DM:  dry matter

3  Percentages are based on data in Table 1 Feedstuffs (June 2008).

4  Residue levels for beef and dairy are corrected for moisture content
and are determined by formula: tolerance /%DM  x  % in diet.  Residue
levels for poultry and swine are considered “as-is” and are
determined by formula: tolerance  x  % in diet.

Conclusions:  At the levels calculated for cattle and poultry above,
there would be no detectable residues of chlorimuron ethyl expected in
livestock commodities.  Therefore, tolerances and a feeding study are
not required for ruminants and poultry at this time.  As a result of
these conclusions, detectable residues of chlorimuron ethyl are also not
expected in hogs.

860.1500 Crop Field Trials

Field Corn

47548201, W. Cutchin, in process

DuPont has submitted field trial data supporting the use of chlorimuron
ethyl on field corn that is tolerant to sulfonylurea herbicides.  A
total of 23 field trials, each including three different treatment
regimes, were conducted in Zones 1, 2, 5 and 6 during 2006.  In each
trial, a 25% water-dispersible granule (WDG) formulation of chlorimuron
ethyl was applied to field corn as a single broadcast foliar application
at 0.06 lb ai/A at approximately 7 days prior to normal forage harvest
(Trt #1), 7 days prior to grain harvest (Trt #3), or at growth stage
R1-R2 (Trt #6).  All applications were made using ground equipment at
volumes of 5-30 gal/A, and included the use of a non-ionic surfactant at
0.25% v/v.

Single control and duplicate treated samples of the appropriate
commodities were harvested from each test at the appropriate stage of
maturity.  For Trt #1, forage was harvested at 6-8 days after treatment
(DAT), stover was harvested at 23-63 DAT and grain was harvested at
26-63 DAT.  For Trt #6, forage was harvested at 23-71 DAT, stover was
harvested at 50-106 DAT and grain was harvested at 55-106 DAT.  For Trt
#3, only samples of stover and grain were harvested at 5-22 and 5-12
DAT, respectively.  Duplicate repeated samples of forage and/or stover
were also collected from Trts #1, #3 and #6 from five field trials.  For
Trt #1, forage samples were collected repeatedly from 0-22 DAT and
stover samples were collected repeatedly from 23-84 DAT.  For Trt #3,
stover samples were collected repeatedly from 6-28 DAT.  For Trt #6,
forage samples were collected repeatedly from 0-68 DAT.

Samples were stored frozen for up to 12.2 months prior to analysis, and
adequate storage stability data are available indicating that
chlorimuron ethyl is stable at -20°C for up to 10 months in corn grain
and forage and 12 months in corn stover.  These data support the
durations and conditions of sample storage from the corn field trials.

The liquid chromatography with tandem mass spectroscopy/mass
spectroscopy detector (LC/MS/MS) method used for determining residues of
chlorimuron ethyl was adequately validated in conjunction with the
analysis of the field trial samples.  For this method, samples are
hydrated (grain and stover) with potassium phosphate buffer and then
extracted twice with acetonitrile (ACN)/K2HPO4 (75:25 v:v, pH 7)
followed by centrifugation.  Residues were then cleaned up by solvent
partitioning and elution through a solid-phase extraction (SPE)
cartridge.  Residues were determined by LC/MS/MS using external
standards for quantitation.  The method LOQ is 0.01 ppm and the LOD is
0.003 ppm for each corn matrix.

Following a single broadcast foliar application at 0.06 lb ai/A applied
~7 days prior to normal forage harvest (Trt #1), chlorimuron ethyl
residues were <0.01-0.64 ppm in/on 46 samples of forage harvested at 6-8
DAT, <0.01-0.25 ppm in/on 46 samples of stover harvested at 23-63 DAT
and <LOD (<0.003 ppm) in/on all 46 samples of grain harvested at 26-63
DAT.  Average residues were 0.11 ppm for forage, 0.05 ppm for stover,
and <0.01 ppm for grain.  The HAFT residues were 0.47 ppm for forage,
0.22 ppm for stover, and <0.01 ppm for grain.

≤0.01 ppm for forage, stover, and grain, and the HAFT residues were
0.07 ppm for forage, 0.04 ppm for stover, and <0.01 ppm for grain. 

When the foliar application was applied ~7 days prior to normal grain
maturity (Trt #3), residues were <0.01-2.30 ppm in/on 46 samples of
stover harvested at 5-22 DAT and <0.01 ppm in/on all samples of grain
harvested at 5-12 DAT, with only 8 grain samples having residues ≥LOD
(0.003-0.007 ppm).  Average residues were <0.01 ppm for grain and 0.49
ppm for stover, and the HAFT residues were <0.01 ppm for grain and 1.62
ppm for stover. 

In the five residue decline trials, chlorimuron ethyl residues in/on
forage from both Trts #1 and #6 showed a rapid decline in residues
within the first 7 days after treatment.  Thereafter, residues in forage
declined more slowly and were generally <0.02 ppm within 21 days of
treatment.  Changes in residues levels in/on stover from Trts #1 and #3
were more sporadic than for forage, but residues in/on stover generally
declined or remained steady at longer post-treatment intervals.

Table 15. 	Summary of Residue Data from Field Corn Crop Field Trials
with Chlorimuron ethyl.

Commodity	Trt #	Total Applic. Rate

(lb ai/A)	PHI (days)	Residue Levels (ppm) 1

n	Min.	Max.	HAFT 2	Median	Mean	Std. Dev.

Forage	1	0.06	6-8	46	<0.01	0.64	0.47	0.06	0.11	0.12

Stover

	23-63	46	<0.01	0.25	0.22	0.03	0.05	0.06

Grain

	26-63	46	<0.01	<0.01	<0.01	<0.01	<0.01	N/A

Stover	3	0.06	5-22	46	<0.01	2.30	1.62	0.29	0.49	0.49

Grain

	5-12	46	<0.01	<0.01	<0.01	<0.01	<0.01	N/A

Forage	6	0.06	23-71	44	<0.01	0.10	0.07	0.01	0.01	0.03

Stover

	50-106	46	<0.01	0.04	0.04	0.01	0.01	0.01

Grain

	55-106	44	<0.01	<0.01	<0.01	<0.01	<0.01	N/A

1	The LOQ is 0.01 ppm for each commodity.  For all calculations, the
method LOQ (0.01 ppm) was used for residue values <LOQ.

2	HAFT = Highest Average Field Trial.

NA = not applicable

Soybean

47548202, W. Cutchin, in process

DuPont has submitted field trial data supporting the use of chlorimuron
ethyl on soybeans that are tolerant to sulfonylurea herbicides.  A total
of 23 field trials, each including two different treatment regimes, were
conducted in Zones 2, 4 and 5 during 2006.  In each trial, a 25%
water-dispersible granular (WDG) formulation of chlorimuron ethyl was
applied to soybeans as a single broadcast foliar application at 0.06 lb
ai/A at growth stage R1-R2 (Trt #3) or approximately 7 days prior to
normal seed harvest (Trt #4).  All applications were made using ground
equipment at volumes of 5-27 gal/A, and included the use of a non-ionic
surfactant at 0.25% v/v.

For Trt #3, single control and duplicate treated samples of forage and
hay were harvested on the day of application (0 DAT), and seeds were
harvested at normal maturity (68-107 DAT).  Repeated samples of forage
and hay were also collected from three trials at 0, 1, 3, 7, 14 and 21
DAT to evaluate residue decline.  For Trt #4, single control and
duplicate treated samples of seeds were harvested at 5-8 DAT.

Samples were stored frozen for up to 9.2 months prior to analysis, and
adequate storage stability data are available indicating that
chlorimuron ethyl is stable at -20°C for up to 10 months in corn
forage, grain and stover.  These data support the durations and
conditions of sample storage from the soybean field trials.

The liquid chromatography with tandem mass spectroscopy/mass
spectroscopy detector (LC/MS/MS) method used for determining residues of
chlorimuron ethyl was adequately validated in conjunction with the
analysis of the field trial samples.  For this method, samples are
hydrated (hay and seed only) with potassium phosphate buffer and then
extracted twice with acetonitrile (ACN)/K2HPO4 (75:25 v:v, pH 7)
followed by centrifugation.  Residues were then cleaned up by solvent
partitioning and elution through a solid-phase extraction (SPE)
cartridge.  Residues were determined by LC/MS/MS using external
standards for quantitation.  The method LOQ is 0.01 ppm and the LOD is
0.003 ppm for each soybean commodity.

Following a single broadcast foliar application at 0.06 lb ai/A at
growth stage R1-R2 (Trt #3), chlorimuron ethyl residues were 1.6-9.0 ppm
in/on 38 samples of forage and 1.0-29.0 ppm in/on 38 samples of hay
harvested at 0 DAT, and residues were <0.01 ppm in/on all 44 samples of
seed harvested at 68-107 DAT.  Average residues were 4.22 ppm for
forage, 13.7 ppm for hay, and 0.01 ppm for seeds.  The HAFT residues
were 8.65 ppm for forage, 25.0 ppm for hay, and <0.01 ppm for seeds.

When the single foliar application was applied at 0.06 lb ai/A
approximately 7 days before normal crop maturity (Trt #4), residues were
<0.01-0.29 ppm in/on 44 samples of seeds harvested at 5-8 DAT.  Average
residues in/on seeds were 0.03 ppm, and the HAFT residues were 0.26 ppm.

 

For both forage and hay, chlorimuron ethyl residues declined rapidly
within the first week after application and then declined more slowly
thereafter.  For all three decline tests, average residues in/on forage
were 3.9 ppm at 0 DAT, 0.10 ppm by 7 DAT, and 0.01 ppm by 21 DAT. 
Average residues in/on hay were 16.6 ppm at 0 DAT, 0.30 ppm by 7 DAT,
and 0.03 ppm by 21 DAT. 

Table 16. 	Summary of Residue Data from Soybean Field Trials with
Chlorimuron Ethyl.

Commodity	Trt #	Total Applic. Rate

(lb ai/A)	PHI (days)	Residue Levels (ppm) 1

n	Min.	Max.	HAFT 2	Median	Mean	Std. Dev.

Forage	3	0.06	0	38	1.6	9.0	8.65	3.90	4.22	1.90

	1	6	0.23	2.7	2.3	1.75	1.43	0.99

	3	6	0.09	0.94	0.89	0.15	0.38	0.40

	7	6	0.02	0.24	0.22	0.06	0.10	0.09

	14	6	0.01	0.07	0.07	0.01	0.03	0.03

	21	6	0.01	0.024	0.024	0.01	0.02	0.01

	14 3	38	0.07	0.38	0.37	0.16	0.18	0.08

Hay

	0	38	1.0	29.0	25.0	13.5	13.67	7.83

	1	6	1.10	10.00	8.80	4.50	4.82	3.53

	3	6	0.63	5.10	3.95	2.45	2.43	1.71

	7	6	0.05	0.90	0.69	0.16	0.30	0.33

	14	6	0.02	0.20	0.19	0.03	0.08	0.09

	21	6	0.01	0.07	0.07	0.01	0.03	0.03

	14 3	38	0.05	1.39	1.20	0.65	0.66	0.38

Seed

	68-107	44	<0.01	<0.01	<0.01	0.01	0.01	NA

Seed	4	0.06	5-8	44	<0.01	0.29	0.26	0.01	0.03	0.05

1	The LOQ is 0.01 ppm for each commodity.  For all calculations, the
method LOQ (0.01 ppm) was used for residue values <LOQ.

2	HAFT = Highest Average Field Trial.

3   Residue data calculated from 0-day PHI data using rate of decline

NA = not applicable

Conclusions:  The available corn and soybean field trial data are
acceptable and support the proposed use patterns for chlorimuron ethyl
on genetically modified field corn and soybeans.  An adequate number of
tests were conducted on each crop in the appropriate geographical
regions.  All samples were analyzed for the residue of concern using an
adequate method, and sample storage conditions and intervals were
supported by the available storage stability data.

The datasets for chlorimuron ethyl residues in/on corn RACs were entered
into the tolerance spreadsheet.  The results indicate that the residue
field trial data support the requested tolerances on corn RACs.  ARIA
recommends for the proposed tolerances for residues of chlorimuron ethyl
on corn, field, forage at 0.5 ppm; corn, field, grain at 0.01 ppm; and
corn, field, stover at 2.0 ppm.

 

The dataset for chlorimuron ethyl on soybean seed indicate that residues
above the LOQ would not be expected from the proposed use.  Although the
residue data support a 0.01 ppm tolerance for soybean seeds, there is an
existing 0.05 ppm tolerance for chlorimuron ethyl on soybeans that
harmonizes with the current Canadian MRL for soybeans (0.05 ppm).  The
existing soybean tolerance will cover the proposed use.  A revised
Section F should be submitted removing the requested change in the
soybean seed tolerance.

The use pattern being supported on soybeans by DuPont is Trt#3; however,
the petitioner is requesting a 14-day PHI for forage and hay rather than
a 0-day PHI, which is supported by the available residue data.  Based on
the data from the residue decline studies, DuPont used the rate constant
from the decline curve with the longest rate of decline to extrapolate
possible residue values for soybean forage and hay at the proposed
14-day PHI.  The following formula was used to calculate 14-day residue
values for forage and hay:

	ln(residues at 14 days) = m(14) + ln(residues at 0 DAT) 

Based on the residue decline data, the rate of decline (m) was
calculated to be -0.226 for soybean forage and -0.217 for soybean hay. 
The extrapolated 14-day residue values for forage and hay are presented
in Appendix III and summarized in Table 16.  ChemSAC met on 6/24/09 to
discuss the use of decline data for tolerance setting purposes.   The
ChemSAC determined that in this case the use of decline data is
acceptable since this is for an animal feed item and not a human food
item, and the data extrapolation made use of the decline study which
gave the most conservative residue number.  Placing the residue data as
calculated using the above formula into the MRL spreadsheet indicates
the requested tolerances are appropriate.  Therefore, ARIA recommends
for the proposed chlorimuron ethyl tolerances of 0.45 ppm in/on soybean
forage and 1.8 ppm in/on soybean hay.  

860.1520 Processed Food and Feed

Corn

47548203, W. Cutchin, in process

Three field trials were conducted in IA and NE during 2006 to generate
field corn grain for use in processing (2 tests) or for generating AGF
(1 test).  In the test used to generate AGF samples, chlorimuron ethyl
(25% WDG) was applied as a single broadcast foliar application 7 days
prior to normal grain maturity at a rate of 0.063 lb ai/A (1x rate).  In
the two tests used to generate grain for processing, chlorimuron ethyl
(25% WDG) was applied as a single broadcast foliar application 7 days
prior to normal harvest at a rate of 0.31 lb ai/A (5x rate).  All
applications were made using ground equipment at volumes of 16-20 gal/A,
and included the use of a non-ionic surfactant at 0.25% v/v.  

Single bulk control and treated sample of corn grain (RAC) were
harvested from each test at 7 DAT.  AGF samples were generated from corn
grain from the 1x rate test using procedures designed to simulate the
movement of grain through terminal elevators.  Corn grain samples from
the 5x rate tests were processed using simulated commercial milling
procedures into starch, grits, meal, flour, and refined oil (wet- and
dry-milled).  Samples of corn grain were stored frozen for up to 6.5
months prior to analysis, and corn AGF and each processed commodity was
stored frozen for ≤30 days prior to analysis.  These sample storage
conditions and durations are supported by the available storage
stability data.

 

Residues of chlorimuron ethyl in/on corn grain, AGF and processed
fractions were determined using an adequate LC/MS/MS method (Method
13412, Revision No. 1).  The method LOQ is 0.01 ppm and LOD is 0.003 ppm
for each corn commodity.

In the test used to generate AGF, chlorimuron ethyl residues averaged
0.01 ppm in/on the grain harvested at 7 DAT following an application at
a 1x rate.  Residues in/on AGF averaged 1.2 ppm, indicating that
chlorimuron ethyl residues can concentrate by up to 120x in AGF (Table
17).  In the two processing studies conducted at a 5x rate, residues
in/on corn grain averaged 0.007 ppm in one test and 0.036 ppm in the
other test.  In both tests, chlorimuron ethyl residues concentrated
slightly in flour and meal, and were reduced in grits, starch and oil. 
Average processing factors for chlorimuron ethyl were 1.5x for flour,
1.4x for meal, 0.5x for grits, and <0.3x for starch and refined oil.

  SEQ CHAPTER \h \r 1 Table 17.  Summary of Corn Processing Factors for
Chlorimuron Ethyl.

RAC	Processed Commodity	Processing Factor

Corn Grain 	AGF	120x

	Grits	0.5x

	Meal	1.4x

	Flour	1.5x

	Refined oil	<0.3x

	Starch	<0.3x

Soybean  

47548204, W. Cutchin, in process

Three soybean field trials were conducted in IL, MN and NE during 2006
to generate soybean seed samples for processing (2 tests) and for
generating AGF (1 test).  In the test used to generate AGF samples,
chlorimuron ethyl (25% WDG) was applied as a single broadcast foliar
application 5 days prior to normal seed maturity at 0.06 lb ai/A (1x
rate).  In the two tests used to generate seeds for processing,
chlorimuron ethyl (25% WDG) was applied as a single broadcast foliar
application 7 days prior to normal harvest at 0.31 lb ai/A (5x rate). 
All applications were made using ground equipment at volumes of 15-25
gal/A, and included the use of a non-ionic surfactant at 0.25% v/v.

at ≤-12°C for up to 2 months prior to analysis, and samples of each
processed fraction and the AGF were stored frozen for ≤30 days prior
to analysis.  These sample storage conditions and durations are
supported by the available storage stability data.

 

Residues of chlorimuron ethyl in/on soybean seeds, AGF and processed
fractions were determined using an adequate LC/MS/MS method (Method
13412, Revision No. 1).  The method LOQ is 0.01 ppm and LOD is 0.003 ppm
for each soybean commodity.

In the test used to generate AGF, chlorimuron ethyl residues averaged
0.0135 ppm in/on the seeds harvested 5 days following a 1x rate
application.  Residues in/on AGF averaged 3.9 ppm, indicating that
indicating that chlorimuron ethyl residues can concentrate by up to 289x
in soybean AGF.

For the 5x tests, chlorimuron ethyl residues in/on whole seeds were <LOD
in one test and 0.33 ppm in the other test.  For the test with
quantifiable residues in/on seeds, residues averaged 0.098 ppm in meal,
1.15 ppm in hulls, and <0.003 ppm in refined oil.  Chlorimuron ethyl
residues concentrated by 3.5x in hulls and were reduced by 0.3x in meal
and <0.01x in oil.

  SEQ CHAPTER \h \r 1 Table 18.  Summary of Processing Factors for
Chlorimuron Ethyl.

RAC	Processed Commodity	Processing Factor

Soybean Seed	AGF	289x

	Hulls	3.5x

	Meal	0.3x

	Refined oil	<0.01x

Conclusions:  The available corn and soybean processing data for
chlorimuron ethyl are adequate.  As residues did not concentrate in corn
grits, starch or refined oil, separate tolerances are not required for
these corn commodities.  Based on the HAFT residues for corn grain (0.01
ppm) and the processing factors for meal and flour from the exaggerated
rate processing study, the maximum expected residues in corn meal and
flour would be 0.014 and 0.015 ppm, respectively.  Since the tolerance
on the RAC, field corn grain, is set at the method LOQ (0.01 ppm) and
the suggested tolerances on corn meal and flour are less than 2x the
LOQ, tolerances on those processed commodities are not required (OPPTS
Guideline 860.520 f(3)(iv)).  A revised Section F should be submitted
removing the requested tolerances on field corn meal and flour.  

For soybeans, residues did not concentrate in meal or refined oil;
therefore separate tolerances are not required for these processed
fractions.  Based on the HAFT residues for soybeans (0.01 ppm) and the
processing factor for hulls (3.5x), the maximum expected residues in
hulls are 0.035 ppm.  As this level of residues is below the current
0.05 ppm tolerance for soybean seeds, a separate tolerance is also not
required for soybean hulls.  A revised Section F should be submitted
removing the requested tolerance on soybean hulls.

 

Chlorimuron ethyl residues were shown in concentrate in AGF from both
corn grain (120x) and soybean seeds (279x).  Based on the HAFT residues
of field corn grain (0.01 ppm) and soybean seeds (0.01 ppm), the maximum
expected residues in AGF would be 1.2 ppm for corn grain and 2.79 ppm
for soybean seeds.  Since the residues in soybean AGF are higher than
for corn grain, the tolerance for AGF should be set at 3.0 ppm (rounded)
based on the soybean residue data.  

A revised Section F for the residues of chlorimuron ethyl in aspirated
grain fractions at 3.0 ppm should be submitted.  The requests for
separate soybean and corn AGF should be removed from the revised Section
F.

  SEQ CHAPTER \h \r 1 860.1650 Submittal of Analytical Reference
Standards

An analytical standard for chlorimuron ethyl is currently available in
the National Pesticide Standards Repository.

860.1850-1900 Confined and Field Accumulation in Rotational Crops

DP Num: 301317, R. Griffin, 8/31/04

A sandy loam soil was treated with [14C-phenyl(U)]chlorimuron ethyl at
the rate of 0.0375 lbs ai/A and aged for 120 days in a greenhouse. 
Barley, beets, cotton and peanuts were planted after the 120-day aging
period and grown to maturity.  Crop samples were harvested and analyzed
at various stages of growth and at maturity. At final harvest barley
straw, peanuts, and cotton foliage contained total 14C residues of
0.025, 0.016, and 0.016 ppm, respectively, but contained very low
concentrations (<0.005 ppm) of chlorimuron ethyl and its major
metabolites.  Total 14C-residue concentrations in each of the other
mature crop fractions were insignificant (<0.01 ppm).  14C-Residues in
the soil samples declined from 0.019 ppm at treatment to 0.0022 ppm at
the final harvest.  Field accumulation in rotational crops studies have
not been submitted; however, due to the insignificant residues (<0.01
ppm) detected in the confined rotational crop study, trials for field
accumulation in rotational crops are not required.

860.1550 Proposed Tolerances

Tolerances for residues of chlorimuron ethyl are currently expressed in
terms of chlorimuron ethyl per se.  However, the tolerance expression
for established and proposed tolerances should be corrected in 40 CFR
§180.429(a) to adhere to HED policy (S. Knizner, 5/27/09):
“Tolerances are established for residues of chlorimuron ethyl,
including its metabolites and degradates, in or on the commodities in
the table below.   Compliance with the tolerance levels specified below
is to be determined by measuring only chlorimuron ethyl [ethyl
2-(4-chloro-6-methoxypyrimidin-2-ylcarbamoylsulfamoyl) benzoate], in or
on the commodity.”   The proposed and recommended tolerances are
presented in Table 19.

 

As residues were <LOQ in/on all samples of corn grain collected at the
appropriate PHI, the recommended tolerance for corn grain was set at the
method LOQ (0.01 ppm).  For field corn forage and stover and soybean
forage and hay, tolerances were calculated using the tolerance
harmonization spreadsheet (Appendix I).  The residue data supporting the
7-day PHI were used to calculate tolerances for field corn forage and
stover.  For soybean forage and hay, the 0-day residue data were
extrapolated to a 14 day PHI based on the observed residue decline data.
 The calculated 14-day residues were then used to determine the
appropriate soybean tolerances.  For soybean seeds, the existing 0.05
ppm tolerance, which harmonizes with the Canadian MRL, will cover any
residues in/on soybean seeds resulting from the proposed use.

As residues did not concentrate in corn grits, starch or refined oil and
soybean meal and refined oil separate tolerances are not required for
these commodities.  Based on the HAFT residues for corn grain (0.01 ppm)
and the processing factors for meal and flour, the maximum expected
residues in corn meal and flour would be 0.014 and 0.015 ppm,
respectively.  Since the tolerance on the RAC, field corn grain, is set
at the method LOQ (0.01 ppm) and the suggested tolerances on corn meal
and flour are less than 2x the LOQ, tolerances on those processed
commodities are not required.  Based on the HAFT residues for soybeans
(0.01 ppm) and the processing factor for hulls (3.5x), the maximum
expected residues in hulls are 0.035 ppm.  As this level of residues is
below the current 0.05 ppm tolerance for soybean seeds, a separate
tolerance is also not required for soybean hulls.

 

Chlorimuron ethyl residues concentrated in AGF from both corn grain
(120x) and soybean seeds (279x).  Based on the HAFT residues of field
corn grain (0.01 ppm) and soybean seeds (0.01 ppm), the maximum expected
residues in AGF would be 1.2 ppm for corn grain and 2.79 ppm for soybean
seeds.  As residues in soybean AGF are higher than for corn grain, the
tolerance for AGF should be set at 3.0 ppm based on the soybean residue
data.

Based on the calculated dietary burdens of livestock and the available
metabolism studies, infinite residues of chlorimuron ethyl are not
expected to occur in ruminant, poultry or hog commodities [40 CFR
180.6(a)(3)].  

There are no established or proposed Codex or Mexican maximum residue
limits (MRLs) for residues of chlorimuron ethyl (Appendix II); however,
there is a Canadian MRL for soybeans (0.05 mg/kg), which harmonizes with
the current U.S. tolerance on soybeans.

Table 19. 	Tolerance Summary for Chlorimuron Ethyl.

Commodity	Proposed Tolerance (ppm)	Recommended Tolerance (ppm)	Comments;
Correct Commodity Definition

Corn, field, grain	0.01	0.01	Adequate residue data are available. 
Residues were <0.01 ppm in/on all corn grain samples.

Corn, field, forage	0.5	0.5	Adequate residue data on forage and stover
are available supporting the 7-day PHI.   Tolerances were calculated
using the tolerance spreadsheet.

Corn, field, stover	2.0	2.0

	Corn, field, meal	0.014	None	Since the tolerance on the RAC, field corn
grain, is set at the method LOQ (0.01 ppm) and the suggested tolerances
on corn meal and flour are less than 2x the LOQ, tolerances on those
processed commodities are not required.

Corn, field, flour	0.015	None

	Corn, aspirated grain fractions	1.28	None	Adequate residue data are
available indicating that residues concentrate in corn grain AGF by
120x.  Based on a HAFT of 0.01 ppm for corn grain, the maximum expected
residues in corn grain AGF would be 1.2 ppm.

Soybean, hay	1.8	1.8	Adequate residue data are available on soybean
forage and hay harvested at 0 DAT.  These data were extrapolated to
calculate residues at 14 DAT, which is the proposed PHI for forage and
hay.  Tolerances were calculated using the tolerance spreadsheet.

Soybean, forage	0.45	0.45

	Soybean, seed	0.01	0.05 1	Although adequate residue data are available
indicating that residues were <0.01 ppm in/on all seed samples following
an application at the R1-R2 stage, the existing 0.05 ppm tolerance will
cover this use. Note: tolerance is recommended for harmonization
purposes.

Soybean, hulls	0.04	None	Residues in/on hulls will be covered by the
existing 0.05 ppm tolerance on soybean seeds.

Soybean, aspirated grain fractions	2.79	None	Adequate data are available
indicating that residues concentrate in soybean AGF by 279x.  Based on a
HAFT of 0.01 ppm for soybean seeds, the maximum expected residues in
soybean AGF would be 2.79 ppm

Grain, aspirated fractions	None	3.0	A single tolerance should be
established for Grain, aspirated fractions based on the soybean AGF
data.

1	There is an existing tolerance of 0.05 ppm for chlorimuron ethyl
residues in/on soybeans, which is identical to the Canadian MRL on
soybeans (0.05 mg/kg).

References

DP Number:	None

Subject:	PP#3G2959 

From:	S. Creeger

To:	not available

Dated:	1/10/1984

DP Number:	301317

Subject:	Chlorimuron Ethyl.  Human Health Risk Assessment

From:	R. Griffin

To:	S. Sherman

Dated:	8/31/2004

DP Number:	335807

Subject:	Chlorimuron Ethyl.  Residue Chemistry

From:	A. Parmar

To:	D. Rosenblatt

Dated:	1/6/09

MRID(s):	47004901 & 43483707

  SEQ CHAPTER \h \r 1 Attachments:  

Appendix I - International Tolerances

Appendix II - Metabolite Tables

Appendix III – MRL Spreadsheet Results 

Appendix I - International Tolerances

INTERNATIONAL RESIDUE LIMIT STATUS

Chemical Name: ethyl
2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]
benzoate	Common Name:  Chlorimuron ethyl	(  Proposed tolerance

 Reevaluated tolerance

 Other	Date: 7/28/09

Codex Status (Maximum Residue Limits)	U. S. Tolerances

√No Codex proposal step 6 or above

 No Codex proposal step 6 or above for the crops requested	Petition
Number: 8F7430 & 8F7439

DP Number:  360845

Other Identifier:  PC Code 128901

Residue definition (step 8/CXL): N/A	Reviewer/Branch:  W. Cutchin/ ARIA

	Residue definition:  Chlorimuron ethyl

Crop (s)	MRL (mg/kg)	Crop(s) 	Tolerance (ppm) 

Corn, field, grain	0.01

Corn, field, forage	0.5

Corn, field, stover	2.0

Soybean, hay	1.8

Soybean, forage	0.45

Soybean, seed	0.05

Grain, aspirated fractions	3.0

	Limits for Canada	Limits for Mexico

 No Limits

 No Limits for the crops requested	√  No Limits

 No Limits for the crops requested

Residue definition: ethyl 2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]
carbonyl]amino]sulfonyl]benzoate	Residue definition: N/A

Crop(s)	MRL (mg/kg)	Crop(s)	MRL (mg/kg)

Soybeans	0.05

Notes/Special Instructions:  S.Funk, 07/30/2009.

Appendix II – Metabolite Tables

A. 2. a  Identification of Compounds from Ruminant Metabolism Study

Common name/code

.	Chemical name	Chemical structure	Matrix

Chlorimuron ethyl 

(DPX-F6025)

I	ethyl
2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]
benzoate		Milk

Liver

Kidney

Urine

Chlorimuron acid

(IN-90161)

II
2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]
benzoic acid		Kidney

Dechloro-chlorimuron ethyl

(IN-N9598)

III	ethyl
2-[[[[(4-hydroxyl-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]
benzoate		Kidney

Feces

DPX-F6025 thiol

V

	ethyl 2-[[[[(4-thio-6-methoxy-2-pyrimidinyl)amino]carbonyl]
amino]sulfonyl] benzoate		Urine

Sulphonamide

(IN-B4450)

IV	Ethyl 2-(aminosulfonyl)benzoate		Kidney

Urine

Pyrimidine amine 

(IN-N6186)

VI	4-Chloro-6-methxoy-2-pyrimidinamine

		Feces

Dechloro pyrimidine amine 

(IN-H9235)

	4-Hydroxy-6-methoxy-2-pyrimidinamine		Milk (tentative)

Table A.2.b.	Identification of Compounds from Poultry Metabolism Study.

Common name/code

   Figure C.3.1  ID No.	Chemical name	Chemical structure	Matrix

Chlorimuron ethyl 

(DPX-F6025)

I	ethyl
2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]
benzoate		Egg yolks

Egg whites

Skin w/fat

Muscle

Liver

Chlorimuron acid

(IN-90161)

II
2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]
benzoic acid		Excreta

4-Hydroxy chlorimuron ethyl

(IN-L9130)	ethyl 2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino]
carbonyl]amino]sulfonyl] 4-hydxoxy benzoate		Muscle (tentative)

5-Hydroxy chlorimuron acid
2-[[[[(4-chloro-5-hydroxy-6-methoxy-2-pyrimidinyl)
amino]carbonyl]amino]sulfonyl] benzoic acid		Liver (putative) 1

Dechloro-chlorimuron ethyl

(IN-N9598)

III	ethyl
2-[[[[(4-hydroxyl-6-methoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]
benzoate		Excreta

Sulphonamide

(IN-B4450)

IV	Ethyl 2-(aminosulfonyl)benzoate		Egg yolks

Egg whites

Skin w/fat

Muscle

Saccharin

(IN-00581)	1,1-Dioxo-1,2-benzothiazol-3-one		Excreta

Pyrimidine amine 

(IN-N6186)

V	4-Chloro-6-methxoy-2-pyrimidinamine

		Egg yolks

Egg whites

Excreta

1	The major unknown in liver was proposed to be 5-hydroxy chlorimuron
acid; however, no reference standard was available for comparison and
LC-MS analyses were inconclusive.

Appendix III - MRL Spreadsheet Results

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Values <LOQ (0.01 ppm) are listed in bold.

Figure III-1.	Lognormal Probability Plot for Residues of Chlorimuron
Ethyl in/on Corn Forage Harvested 6-8 DAT.

Figure III-2.	Data Summary Table for Residues of Chlorimuron Ethyl in/on
Corn Forage Harvested 6-8 DAT.

Figure III-3.	Lognormal Probability Plot for Residues of Chlorimuron
Ethyl in/on Corn Stover Harvested 5-7 DAT.

Figure III-4.	Data Summary Table for Residues of Chlorimuron Ethyl in/on
Corn Stover Harvested 5-7 DAT.



Table III-2.		Chlorimuron ethyl Residues in/on Soybean Forage and Hay.

Regulator:	Chlorimuron ethyl

Chemical:	Soybean Forage	Soybean Hay

Crop:	0 days	14 days (extrapolated)	0 days	14 days (extrapolated)

PHI:	0.06 lb ai/A	0.06 lb ai/A

App. Rate:	DuPont	DuPont

Submitter:	MRID 47548202	MRID 47548202

MRID Citation:	Residues	Residues	Residues	Residues

	1.6	0.068	1.0	0.048

	1.6	0.068	1.5	0.072

	1.9	0.080	1.6	0.077

	2.0	0.085	2.2	0.105

	2.0	0.085	3.5	0.168

	2.2	0.093	5.3	0.254

	2.3	0.097	6.2	0.297

	2.8	0.118	6.6	0.316

	2.8	0.118	6.7	0.321

	2.9	0.123	7.0	0.336

	3.0	0.127	7.4	0.355

	3.2	0.135	7.9	0.379

	3.2	0.135	8.1	0.388

	3.3	0.139	8.6	0.412

	3.3	0.139	10	0.479

	3.5	0.148	11	0.527

	3.6	0.152	13	0.623

	3.7	0.156	13	0.623

	3.8	0.161	13	0.623

	4.0	0.169	14	0.671

	4.0	0.169	15	0.719

	4.2	0.177	15	0.719

	4.3	0.182	15	0.719

	4.5	0.190	16	0.767

	4.6	0.194	18	0.863

	4.6	0.194	18	0.863

	4.7	0.199	20	0.959

	4.8	0.203	20	0.959

	5.2	0.220	20	0.959

	5.2	0.220	21	1.007

	5.7	0.241	21	1.007

	6.0	0.254	22	1.054

	6.2	0.262	23	1.102

	6.9	0.292	24	1.150

	7.6	0.321	24	1.150

	7.9	0.334	25	1.198

	8.3	0.351	26	1.246

	9.0	0.380	29	1.390

Figure III-5.	Lognormal Probability Plot for Residues of Chlorimuron
Ethyl in Soybean Forage Harvested at 0 DAT.

Figure III-6.	Data Summary Table for Residues of Chlorimuron Ethyl in
Soybean Forage Harvested at 0 DAT.

Figure IIII-7.	Lognormal Probability Plot for Residues of Chlorimuron
Ethyl in Soybean Forage Extrapolated to a 14-day PHI.

Figure III-8.	Data Summary Table for Residues of Chlorimuron Ethyl in
Soybean Forage Extrapolated to a 14-day PHI.

Figure III-9.	Lognormal Probability Plot for Residues of Chlorimuron
Ethyl in Soybean Hay Harvested at 0 DAT.

Figure III-10.	Data Summary Table for Residues of Chlorimuron Ethyl in
Soybean Hay Harvested at 0 DAT.

Figure III-11.	Lognormal Probability Plot for Residues of Chlorimuron
Ethyl in Soybean Hay Extrapolated to a 14-day PHI.

Figure III-12.	Data Summary Table for Residues of Chlorimuron Ethyl in
Soybean Hay Extrapolated to a 14-day PHI.



Page   PAGE  1  of   NUMPAGES  48 

Chlorimuron ethyl	Summary of Analytical Chemistry and Residue Data	DP#: 
360845