Clomazone Summary of Analytical Chemistry and Residue Data DP#: D410436

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

MEMORANDUM

Date: March 6, 2014

SUBJECT: Clomazone. PP#2E8136. Brassica, Head and Stem, Subgroup 5A; Rhubarb; and 

Pea, Southern. Summary of Analytical Methods and Residue Data.

PC Code: 125401 DP Barcodes: D410436

Decision Nos: 473594 Registration No.: 279-3052

Petition Nos.: 2E8136 Regulatory Action: Section 3 Registration

Risk Assessment Type: Res Chem Case No.: 7203

TXR No.: NA CAS No.: 81777-89-1

MRID No.: 49026901, 49026902, 

49026903

40 CFR: 180.425

FROM: Susan V. Hummel, Chemist & Senior Scientist

Risk Assessment Branch 4

Health Effects Division (7509P)

THROUGH: Thurston Morton, Chemist

Risk Assessment Branch 4

Health Effects Division (7509P)

TO: Kable Davis, PM25

Herbicide Fungicide Branch, Registration Division (7505P)

MRID Summary Table

MRID No. Study Type Comments

49026901

49026902

49026903

860.1500 Brassica, head and stem, subgroup 5A

860.1500 Rhubarb

860.1500 Pea, southern

New DER; 49026901.der.docx

New DER; 49026902.der.docx

New DER; 49026903.der.docx

The Interregional Research Project Number 4 (IR-4) has submitted a petition to establish 

tolerances for residues of clomazone on Brassica, head and stem, subgroup 5A; rhubarb; and pea, 

southern. In connection with the petition, IR-4 requests amended registration of the FMC 

product Command Technical (EPA Reg. No. 279-3052), to allow use on Brassica, head and 

stem, subgroup 5A; rhubarb; and pea, southern. Tolerances for residues of clomazone, per se, 

have been established on a number of commodities ranging from 0.02 ppm in rice grain to 0.1 

ppm in cabbage and several squashes in 40 CFR §180.425.
Clomazone Summary of Analytical Chemistry and Residue Data DP#: D410436

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Executive Summary

Clomazone is an herbicide which is registered for use on snap beans, succulent peas, cabbage, 

cotton, cucurbits, pepper, mint, rice, soybeans, sugarcane, and tuberous & corm vegetables 

(except potato). Tolerances for clomazone on these commodities are published in 40 CFR 

180.425, including cabbage at 0.1 ppm. Clomazone products are formulated as emulsifiable 

concentrates and microencapsulated formulations. Applications are usually made as a single or 

split (2) pre-plant, or early post-emergence broadcast applications. The current application 

requests adding Brassica, head and stem, subgroup 5A; rhubarb; and pea, Southern; to the label 

for Command 3ME, and proposes tolerances follows.

Brassica, stem and head subgroup 5A 0.1 ppm

Rhubarb 0.3 ppm

Pea, Southern, succulent seed 0.05 ppm

Pea, Southern, dry seed 0.05 ppm

Pea, Southern, hay 0.05 ppm

And at the same time, revoke the tolerance for cabbage at 0.1 ppm, since cabbage will be 

covered by the new tolerance for Brassica, head and stem, subgroup 5A.

The residue of concern is clomazone, per se. Residues of clomazone following treatment at the 

proposed rates to broccoli and southern pea, are non-quantifiable in broccoli, and southern pea 

seed (succulent and dry) and southern pea hay. Residues of clomazone following treatment at 

the proposed rates to rhubarb resulted in quantifiable residues of up to 0.062 ppm; a 0.15 ppm 

tolerance is recommended.

Regulatory Recommendations and Residue Chemistry Deficiencies

HED recommends for the proposed tolerance, with corrections specified below, and for the 

associated amended use. The current tolerance expression is in accord with our current guidance 

on tolerance expressions. The field trials for clomazone on broccoli, rhubarb, and southern peas

are adequate. The enforcement analytical method is adequate. The residue data are supported by 

available storage stability data.

Tolerance Summary for Clomazone. § 180.425

Commodity Current/Proposed 

Tolerance (ppm)

Recommended 

Tolerance (ppm)

Comments; Correct Commodity 

Definition

Brassica, stem and head

subgroup 5A

0.1 0.10 Brassica, head and stem, subgroup 5A.

Tolerance changed to add a significant 

figure.

Rhubarb 0.3 0.30 Tolerance changed to add a significant 

figure.

Pea, Southern, succulent 

seed

0.05 0.05

Pea, Southern, dry seed 0.05 0.05

Pea, Southern, hay 0.05 0.05 Cowpea, hay and Cowpea, forage. 

Southern pea hay is a very minor feed, 

but cowpea is a type of southern pea.
Clomazone Summary of Analytical Chemistry and Residue Data DP#: D410436

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Revisions to Petitioned-For Tolerances and Existing Tolerances

Revisions are recommended to petitioned-for tolerances for consistent naming of commodities, 

and to add a significant figure. The recommended changes are documented in the Table above. 

Tolerances are being established for cowpea, forage, and cowpea, hay, rather than southern pea 

hay, because cowpea is a type of southern pea.

International Harmonization

There are no CODEX MRLs for residues of clomazone on any commodity. Canada has not 

established MRLs for the commodities in this petition.

Required Label Changes

No label revisions are required; however, it should be noted that while the proposed maximum 

use rate on rhubarb is 1 application at 1.5 lb ai/A at dormancy, the submitted field trial data for 

rhubarb would support a second application at 1.0 lb ai/A a minimum of 50 days after the first 

application, with a PHI of 42 days, with a maximum seasonal application rate of 2.5 lb ai/A. If a 

second application on rhubarb is desired, the petitioner should submit an amended petition to 

reflect this proposed use

Background

Clomazone is an herbicide which is registered for use on snap beans, succulent peas, cabbage, 

cotton, cucurbits, pepper, mint, rice, soybeans, sugarcane, and tuberous & corm vegetables 

(except potato). Tolerances for clomazone on these commodities are published in 40 CFR 

180.425, including rice grain and straw at 0.02 ppm.. Clomazone products are formulated as 

emulsifiable concentrates and microencapsulated formulations. Applications are usually made as 

a single or split (2) pre-plant, or early post-emergence broadcast applications. A layby use is 

registered for clomazone on cotton. The current application requests adding Brassica, head and 

stem, subgroup 5A, rhubarb, and southern pea to the Command 3ME label.

The chemical structure and nomenclature of the active ingredient, clomazone, are presented 

below in Table 1. The physicochemical properties are presented below in Table 2.

TABLE 1. Test Compound Nomenclature.

Compound Chemical Structure

Common name Clomazone

Company experimental name FMC 57020

IUPAC name 2-(2-chlorobenzyl)-4,4-dimethylisoxazolidin-3-one

CAS name 2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone
Clomazone Summary of Analytical Chemistry and Residue Data DP#: D410436

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CAS # 81777-89-1

End-use product/(EP) Command ME, EPA Reg. No. 279-3158

TABLE 2. Physicochemical Properties of the Technical Grade Test Compound: Clomazone. 

Parameter Value Reference

Melting point/range 25 C, broad range MRID 00144241

pH 6.89 + 14 (supernatant of slurry) MRID 00144241

Density 1.187 g/mL MRID 00144241

Water solubility ( mg/L at unspecified C) 1100 mg/L MRID 00144241

Solvent solubility (mg/L at unspecified C) >200 mg/L in Tenneco 500-100

 4.5-5.0 mg/L in Isopar M

 >90 mg/L in refined soybean oil

 Infinite in dimethyl formamide

 Infinite in cyclohexanone

MRID 00144241

Vapour pressure at 25 C 1.92 x 10 -2Pa (1.44 x 10 -4 mm Hg) MRID 00144241

Dissociation constant (pKa) N/A neither acidic nor basic MRID 00144241

Octanol/water partition coefficient Log(KOW) 350 (log p = 2.54) MRID 00144241

UV/visible absorption spectrum Not available

860.1200 Directions for Use

Table 3. Summary of Directions for Use of Clomazone

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

Brassica, Head & Stem, Subgroup 5A; Direct Seeded Cabbage; Transplant Broccoli

Broadcast 3.0 lb/gal ME

[279-3158]

0.25 1 NS NS Use as a soil applied 

treatment prior to weed 

emergence.

Transplant Cabbage

Broadcast 3.0 lb/gal ME

[279-3158]

0.25-0.5 1 NS NS Use lower rate on coarse 

soils and higher rate on fine 

soils. Use as a soil applied 

treatment prior to weed 

emergence.

Rhubarb

Broadcast 3.0 lb/gal ME 

[279-3158]

1.5 NS NS NS Apply to dormant rhubarb 

prior to leaf emergence.

Peas, Southern

Broadcast 3.0 lb/gal ME 

[279-3158]

0.52 1 NS NS Use as a soil applied 

treatment prior to weed 

emergence.

Label restrictions include: 

Command 3ME herbicide may be utilized as a soil applied treatment prior to weed emergence, 

for suppression or control of annual grass and broadleaf weeds in snap beans (succulent), 
Clomazone Summary of Analytical Chemistry and Residue Data DP#: D410436

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brassica (head and stem subgroup 5A), cucumbers, peas (southern), peas (succulent), peppers, 

rhubarb, squash (including processing pumpkins) and sweet potatoes. 

Make a single herbicide application in a minimum of 10 gallons of water per acre at the rate(s) 

specified in the individual crop listings hereafter. Apply as a pre-emergent soil applied treatment 

prior to seeding or transplanting, or after seeding but prior to crop emergence. Place seed, or 

roots of the transplants, below the chemical barrier when planting.

Rotational Crop Restrictions include suggestions for minimizing increased risk to rotational 

crops plus the following instructions for applications on rice at up to 0.8 lb ai/A

- The following crops may be planted anytime: cabbage (transplants), cotton, peas, 

peppers, rice, soybeans, squash, sweet potatoes, tobacco, tuberous and corm vegetables. 

- The following crops may be planted after 9 months: All crops listed above plus: beans 

(succulent and dry), cabbage (direct seeded), corn (field, pop, seed, sweet), cotton, cucurbits, 

peanuts, potatoes, sorghum, sugar beets, tomatoes (transplanted).

- The following crops may be planted after 12 months: All crops listed above plus: 

tomatoes (direct seeded) and wheat

- The following crops may be planted after 16 months: all crops.

Conclusions. The label use directions for clomazone on Brassica, head and stem subgroup 5A, 

transplant broccoli and cabbage; and southern peas are adequate to evaluate the residue field trial 

data. The use directions for rhubarb are not clear. The number of applications per season, and 

maximum seasonal application rate are not stated. The submitted field trial data for rhubarb 

would support a second application at 1.0 lb ai/A a minimum of 50 days after the first 

application, with a PHI of 42 days, with a maximum seasonal application rate of 2.5 lb ai/A.

OPPTS GLN 860.1300 Nature of the Residue - Plants

Soybeans: PP#4G2987, L. Propst, 4/17/84; PP#4F3128, J. Worthington, 9/24/84

Corn: PP#0G3919, J. Garbus, 11/8/91

Cotton: PP#2F4077, R.W. Cook, 10/28/92

Sweet Potatoes: PP#8E3628, M. J. Nelson, 4/22/92

Tomatoes and Bell Pepper: PP#9E3778, F. D. Griffith, 8/6/90

Alfalfa: PP#8E3608, A. Smith, 3/15/88

Based on metabolism studies on soybeans, corn, cotton, sweet potatoes, tomatoes and bell 

peppers, and alfalfa, HED concludes that the nature of the residue in plants is adequately 

understood. The major metabolite was 2-chlorobenzyl alcohol. The postulated major route of 

metabolism of clomazone in plants is hydroxylation of the methylene bridge carbon of 

clomazone to form the carbinolamide; decomposition of the unstable intermediate, the 

carbinolamide, to form the isoxazolidinone moiety and 2-chlorobenzaldehyde. 2-

chlorobenzaldehyde reduces to the alcohol or is oxidized to the carboxylic acid. The alcohol, the 

carboxylic acid, and the isoxazolidinone metabolites form glycosides and/or amino acid 

conjugates. Minor pathways include hydroxylation of clomazone to form monohydroxylated and 

possibly dihydroxylated metabolites. Based on low levels of these metabolites found in crops, 

the residue of concern for regulatory and risk assessment purposes in plants is clomazone per se 

(PP#8E3628, M. J. Nelson, 4/22/92).

The nature of the residue in plants and livestock is adequately understood. The residue of 
Clomazone Summary of Analytical Chemistry and Residue Data DP#: D410436

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concern is clomazone per se as specified in 40 CFR 180.425.

OPPTS GLN 860.1300 Nature of the Residue - Livestock

Ruminants: 40070001, PP#4F3128, L. Bradley, 5/11/87, DEB#5505, F. Griffith, 7/26/89

Poultry: 41663304, 41663305, PP#0G3919, J. Garbus, 11/8/91

As there are no livestock feed stuffs currently associated with Brassica, rhubarb, or southern 

peas, issues pertaining to the nature of the residue in livestock are not germane to this petition.

Goats were fed 0.5 ppm or 5.0 ppm ring-labeled clomazone by capsule (MRID 40070001) . 

Morning and evening milk samples were pooled by day. The majority (86-93%) of the residue 

was eliminated in the urine or feces. Less than 1% of the residue was found in each of the 

tissues, and the residues were below detectable levels. 

Poultry were fed 0.5 ppm or 5.0 ppm ring-labeled clomazone in their feed (MRIDs 41663304, 

41663305). Only egg yolk and liver contained significant levels of residues. Clomazone, per se, 

was not detected in any tissue. Unidentified residues polar conjugates, which appeared to be 

amino acid adducts. 

Ortho-chlorobenzoic acid (OCBA) is a plant metabolite of clomazone which is not a rat 

metabolite. OCBA is about 5% of the residue in alfalfa. The polar residues in plants are 

postulated to be multiple hydroxylated metabolites. 

OPPTS GLN 860.1340: Analytical Enforcement Methodology

PAM II, Method I

Adequate enforcement methods are available for the determination of the residues of clomazone 

in plants. Briefly, samples are acid hydrolyzed, hexane extracted, Na2CO3 washed, and cleanedup with a Florisil column. The resulting samples are analyzed by gas chromatography (GC) 

using a nitrogen phosphorus detector (NPD) or mass spectrometer (MS). The limit of 

quantitation (LOQ) for this method is 0.05 ppm. A confirmatory procedure (GC/MS-SIM) is 

available (Method I, PAM II).

Clomazone was determined in broccoli using the analytical method adapted from method FMC 

No. ACG 124. A number of minor modifications to the method were specified, including the use 

of an accelerated solvent extractor (ASE) in place of the extraction/partition steps and the use of 

an MSD detector in place of the nitrogen-phosphorus detector. Briefly, clomazone residues were

extracted from a five-gram sample of broccoli with hexane using an ASE. The extracts were 

placed in a freezer for at least 1 hour and then evaporated to dryness. Residues were redissolved 

in hexane for GC/MSD analysis, using single ion monitoring (SIM), monitoring m/z 204, for 

quantitation.. The column used was not specified in the report. The LOQ (determined as the 

LLMV) was 0.03 ppm for broccoli and rhubarb; and 0.05 ppm in southern pea commodities. 

The calculated LOQ and LOD, respectively, were 0.01850 and 0.006168 ppm in broccoli; 0.0394 

and 0.0131 ppm in rhubarb, and .

Conclusions. An adequate enforcement method is available. The residue data were gathered 

with an adequate data collection method.
Clomazone Summary of Analytical Chemistry and Residue Data DP#: D410436

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860.1360 Multiresidue Methods

MRID 42325301, PP#0G3919, J. Garbus, D178768, 9/21/92

Multiresidue methods data are available for clomazone tested through Protocols C, D and E. 

Due to the chemical structure of clomazone, Protocols A and B are not applicable. GC 

parameters were gathered for clomazone in Protocol C. Recovery of clomazone through 

protocol E was partial and variable (7 to 58%). 

860.1380 Storage Stability

49026901.der.docx, 49026902.der.docx, 49026903.der.docx

D242601, M. Perry, 1/29/98; and D272158, D. Vogel, 1/24/01. 

Concurrent storage stability data were included with each field trial report in this submission, 

although no zero day data were provided. Storage stability samples were stored under the same 

conditions as the field trial samples, and residues of clomazone on broccoli, rhubarb, and pea 

commodities were stable. Storage stability data also are available for field corn, rice and 

sugarcane which demonstrate that residues of clomazone are stable for up to 12 months (Memos, 

TABLE 4. Summary of Storage Conditions.

Matrix Storage Temperature 

(°C)

Actual Storage Duration1 Limit of Demonstrated Storage Stability2

Broccoli 

(Flower head and 

stem)

Frozen (at NDSU lab)

-28 to -13 (at MSU lab)

323-531 days

(10.6-17.5 months)

539 days

(17.7 months)

Rhubarb Petioles Frozen (at NDSU lab)

-28 to -9 (at MSU lab)

236-276 days

(7.8-9.1 months)

278 days

(9.1 months)

Succulent Shelled 

Pea

~ -20 860-1015 days

(28.3-33.4 months)

1102 days

(36.3 months)

Plants With Pods, 

Fresh

871-1027 days

(28.7-33.8 months)

1103 days

(36.3 months)

Shelled Dry Pea 886-1020 days

(29.1-33.6 months)

1101 days

(36.2 months)

Plants with Pods, 

Dry

858-1014 days

(28.2-33.4 months)

1099 days

(36.2 months)

Conclusions. Storage stability data are adequate to support the submitted field trial data.

860.1400 Water, Fish, and Irrigated Crops

This topic is not pertinent to the current application for amended registration.

The Clomazone 3ME label contains a label restriction, prohibiting use of rice water on rice fields 

in which concurrent crayfish or catfish farming are included in the cultural practices, and use 

water of containing Command 3ME residues from rice cultivation to irrigate food or feed crops 

which are not registered for use with Command 3ME.
Clomazone Summary of Analytical Chemistry and Residue Data DP#: D410436

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Conclusions. No further information is required.

860.1460 Food Handling

This topic is not pertinent to the current submission.

860.1480 Meat, Milk, Poultry, and Eggs

Garbus, J., 11/8/91; PP#0G3919

No change is needed to the rice tolerance. So far, no detectable residues have been found in rice 

commodities. A ruminant metabolism study is available which demonstrated that 5.0 ppm 

clomazone in the livestock diet resulted in 2 to 9 ppb in milk, and 0.03 to 0.05 ppm in the liver 

and kidney tissue (Memo, Joel Garbus, 11/8/91; PP#0G3919). Since, under the proposed use, 

clomazone is not detectable in livestock feed/feedstuffs (<0.05 ppm) and it is transferred to meat 

and milk at a low level, no detectable residues are expected in meat, or milk. While rice grain is 

a poultry feedstuff, high clomazone doses in poultry yielded low levels in tissue and eggs, so that 

no clomazone residues are expected in poultry commodities. 

860.1500 Crop Field Trials

Broccoli: 49026901.der.docx, 

Rhubarb: 49026902.der.docx, 

Southern peas: 49026903.der.docx

IR-4 has submitted field trial data for clomazone on broccoli, rhubarb, and southern peas. 

Broccoli. Eight field trials were conducted in the United States during the 2002 growing season

in the North American Free Trade Agreement (NAFTA) Growing Zones 1 (NY; 1 trial), 6 (TX; 

1 trial), 10 (CA; 5 trials), and 12 (OR; 1 trial). At each trial location, the treated crops received 

one preplant application of a 3 lb ai/gal microencapsulated (ME) formulation of clomazone 

(Command® 3 ME) at 0.24-0.25 lb ai/A. Applications were made using ground equipment in 

spray volumes of 20.0-35.6 gal/A. Adjuvants were not added to the spray mixture at any of the 

trial sites. Samples of broccoli (flower head and stem) were harvested from all trials at a 52- to 

120-day preharvest interval (PHI).

Samples were analyzed for residues of clomazone using an adequate gas chromatography 

method with mass spectrometric detection (GC/MSD), with single ion monitoring (m/z 204), 

adapted from FMC No. ACG 124, as discussed above under Analytical Methodology. The 

samples were stored frozen awaiting analysis, as discussed above under Storage Stability. 

Following one preplant application of the 3 lb ai/gal ME formulation of clomazone at 0.24-0.25 

lb ai/A, residues of clomazone in/on broccoli flower head and stem harvested at a 52- to 120-day

PHI were all <LOQ (<0.03 ppm).
Clomazone Summary of Analytical Chemistry and Residue Data DP#: D410436

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TABLE 5. Summary of Residue Data from Broccoli Field Trials with Clomazone.

Commodity Analyte Total Rate

(lb ai/A)

PHI 

(days)

Residue Levels (ppm)1

n Sample 

Min.

Sample 

Max.

LAFT2 HAFT2 Median Mean Std. 

Dev.

Broccoli Clomazone 0.24-0.25 52-120 8 <0.03 <0.03 <0.03 <0.03 0.03 0.03 N/A

1

 Except for sample min/max, values reflect per trial averages; n = no. of field trials. N/A = Not applicable.

2

 LAFT = lowest average field trial; HAFT = highest average field trial.

Brassica, head and stem, subgroup 5A. There are 2 representative commodities for Brassica, 

head and stem, subgroup 5A, broccoli or cauliflower, and cabbage. The broccoli residue data are 

discussed above. A tolerance has been established for residues of clomazone on cabbage at 0.1 

ppm (PP#4E4311, N. Dodd, D199086, 04/17/95, MRID 43077301). Command 4EC was 

applied at 0.5 lb ai/A as a single broadcast application in at least 10 gallons of water per acre, 

using ground equipment before seeding or transplanting cabbage. Clomazone is incorporated to 

a depth of 1 inch or less. Residues were reported to be non-quantifable at less than 0.1 ppm 

except in one sample in which interferences were noted, and the limit of quantitation was 0.17 

ppm.

Rhubarb. Four field trials were conducted in the United States during the 2003 growing season

in the North American Free Trade Agreement (NAFTA) Growing Zones 5 (MI; 1 trial) and 12 

(OR; 3 trials). At each trial location, the high- and low-rate treated plots, respectively, received 

two broadcast applications of a 3 lb ai/gal microencapsulated (ME) formulation of clomazone 

(Command® 3 ME) at 1.49-1.66 or 0.96-1.14 lb ai/A for application one and 0.98-1.14 or 0.75-

0.85 lb ai/A for application two, for a total seasonal rate of 2.49-2.76 or 1.71-1.99 lb ai/A. The 

first application was made to dormant plants followed by a second application to rhubarb 

approximately 8-24 inches in height. Applications were made at 44- to 63-day retreatment 

intervals (RTIs) using ground equipment in spray volumes of 19.6-45.7 gal/A. Adjuvants were 

not added to the spray mixture at any of the trial sites. Samples of rhubarb were harvested from 

all trials at a 41- to 44-day preharvest interval (PHI).

Samples were analyzed for residues of clomazone using an adequate gas chromatography 

method with mass spectrometric detection (GC/MSD), with single ion monitoring (m/z 204), 

adapted from FMC No. ACG 124, as discussed above under Analytical methodology. The 

samples were stored frozen awaiting analysis, as discussed above under Storage Stability. 

Following two foliar broadcast applications of the 3 lb ai/gal ME formulation of clomazone at 

2.49-2.76 (~1.7 – 1.8x) and 1.71-1.99 lb ai/A (~1.1 – 1.3x), respectively, residues of clomazone 

(and per trial averages) in/on rhubarb petioles harvested at a 41- to 44-day PHI were <0.03-0.180 

(<0.033-0.114) and <0.03-0.076 (<0.03-0.062) ppm.

TABLE 6. Summary of Residue Data from Rhubarb Field Trials with Clomazone.

Commodity Analyte Total Rate

(lb ai/A)

PHI 

(days)

Residue Levels (ppm)1

n Sample 

Min.

Sample 

Max.

LAFT2 HAFT2 Median Mean Std. 

Dev.

Rhubarb 

Petioles

Clomazone 2.49-2.76 41-44 4 <0.03 0.180 <0.033 0.114 0.046 0.060 0.038

1.71-1.99 4 <0.03 0.076 <0.03 0.062 0.044 0.045 0.017

1

 Except for sample min/max, values reflect per trial averages; n = no. of field trials.

2

 LAFT = lowest average field trial; HAFT = highest average field trial.

Southern Peas. Four field trials were conducted in the United States during the 2007 growing 
Clomazone Summary of Analytical Chemistry and Residue Data DP#: D410436

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season in the North American Free Trade Agreement (NAFTA) Growing Zones 2 (SC; 1 trial), 4 

(TN; 1 trial), and 6 (TX; 2 trials). At each trial location, the treated plots received one preemergent application of a 3 lb ai/gal microencapsulated (ME) formulation of clomazone 

(Command® 3 ME) at 0.484-0.501 lb ai/A. Applications were made using ground equipment in 

spray volumes of 16.9-27.6 gal/A. Adjuvants were not added to the spray mixture at any of the 

trial sites. Samples of shelled succulent pea and fresh pea plants with pods were harvested from 

all trials at a 62- to 77-day preharvest interval (PHI). A second harvest occurred at a 77- to 91-

day PHI to collect samples of mature dry pea plants with pods and shelled dry pea.

Samples were analyzed for residues of clomazone using a gas chromatography method with 

mass spectrometric detection (GC/MSD), with single ion monitoring (m/z 204), adapted from 

FMC No. ACG 124, as discussed above under Analytical Methodology. The samples were 

stored frozen awaiting analysis, as discussed above under Storage Stability. 

Following one pre-emergent broadcast application of the 3 lb ai/gal ME formulation of 

clomazone at 0.484-0.501 lb ai/A, residues of clomazone in/on shelled succulent pea and fresh 

plants with pods and shelled dry pea and dry plants with pods and harvested at a 62- to 77-day

and 77- to 91-day PHIs, respectively, were all <LOQ (<0.05 ppm).

TABLE 7. Summary of Residue Data from Southern Pea Field Trials with Clomazone.

Commodity Analyte Total Rate

(lb ai/A)

PHI 

(days)

Residue Levels (ppm)1

n Sample 

Min.

Sample 

Max.

LAFT2 HAFT2 Median Mean Std. 

Dev.

Shelled 

Succulent Pea

Clomazone 0.484-0.501 62-77 4 <0.05 <0.05 <0.05 <0.05 0.05 0.05 N/A

Plants With 

Pods, Fresh

4 <0.05 <0.05 <0.05 <0.05 0.05 0.05 N/A

Shelled Dry Pea 77-91 4 <0.05 <0.05 <0.05 <0.05 0.05 0.05 N/A

Plants with 

Pods, Dry

4 <0.05 <0.05 <0.05 <0.05 0.05 0.05 N/A

1

 Except for sample min/max, values reflect per trial averages; n = no. of field trials. N/A = Not applicable.

2

 LAFT = lowest average field trial; HAFT = highest average field trial.

Conclusions. The submitted field trial studies are adequate to fulfill the data requirements. The 

field trials reflected the proposed use pattern. The analytical method used was adequate for data 

gathering. Samples were analyzed for clomazone, per se, which is the residue of concern. 

Residues were within the proposed tolerances of 0.10, 0.3 ppm, and 0.05 ppm for clomazone in 

or on Brassica, head and stem, subgroup 5A, rhubarb, and southern pea commodities, 

respectively. The basis for the 0.1 ppm tolerance on Brassica, head and stem, subgroup 5A, is 

the existing tolerance for residues of clomazone on cabbage, currently set at 0.1 ppm. Although 

the EC formulation was used in the cabbage field trials, since both the cabbage residues and the 

broccoli residues are less than the limit of quantation, the 0.1 ppm tolerance for residues of 

clomazone on Brassica, head and stem, subgroup 5A, will be considered appropriate. When the 

tolerance on Brassica, head and stem, subgroup 5A, is established, the tolerance on cabbage 

should be revoked. The residue data for southern pea whole plants will support a tolerance for 

residues of clomazone on cowpea forage and hay.

860.1520: Processing Studies
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There are no processed commodities associated with the petitioned for tolerances. This topic is 

not pertinent to the current petition.

860.1850/1900: Rotational Crop 

Offutt,C., 7/2/1985

Creeger, S., 8/27/1985

The minimum PBI, 9 months, has been approved by EFED (Memo, Carolyn Offutt, 7/2/85). 

This restriction was based on low levels of organosoluble residues (<0.02 ppm) observed at the 

10-month interval in the confined rotational crop study conducted at an application rate of 2 lbs 

a.i./A (Memo, Samuel Creeger, 11/23/1984).

Tolerance Recommendations

The current tolerance expression for clomazone in 40 CFR 180.425 is:

Tolerances are established for residues of the herbicide clomazone, including its metabolites and 

degradates, in or on the commodities in the table in this paragraph. Compliance with the 

tolerance levels specified in this paragraph is to be determined by measuring only clomazone, 2-

[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone, in or on the commodity.

The current tolerance expression is in accord with our current guidance on tolerance expressions.

There are no CODEX MRLs for residues of clomazone on any commodity. Canada has not 

established MRLs for the commodities in this petition.

Tolerance recommendations are found in the Executive Summary of this review. The proposed 

tolerances were modified to add a significant figure, to correct the commodity definition, and to 

delete the unneeded tolerance on pea, southern, hay.
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REFERENCES

Creeger, S., “Environmental Fate Review of Registration of Dimethazone Technical and 

Products, 279-GNLE, -GNLG, -GNLU, Accession Number 072819, 248476,” Review by S. 

Hong, EPA Memorandum dated 11/23/1984

Dodd, N., “PP#4E4311. Clomazone on Cabbage. Review of Analytical Methods and Residue 

Data.” D199086, EPA Memorandum dated 04/17/95, MRID 43077301.

Garbus, J., “PP#0G3919. EPA Reg. No. 279-3053. Clomazone in or on Corn R.A.C’s. Request 

for Extension of EUP Program 279-EUP-118 and Temporary Tolerances. Evaluation of 

Analytical Methodology and Residue Data. MRID Nos. 416633-01 thru 4166330-13, 417251-01 

and -02. DEB Nos. 7383, 7384, and 7560.” EPA Memorandum dated 11/8/91.

Garbus, J., “PP#0G3919. EPA Reg. No. 279-3053. Clomazone in or on corn R.A.C’s. Additional 

Analytical Data: Independent Validation of Originally Proposed Enforcement Method and 

Response of Clomazone in FDA Multi-Residue protocols. MRID Nos. 4423253-01 and -02: DP 

Barcodes D178735 and D178768. CBTS Nos. 9947, 9948.” EPA Memorandum dated 8/21/92.

Offutt, C., “Estimated Enviromental Concentrations Review of FMC 57020, 279-GNLE, -

GNLG, & -GNLU.” Reviewed by R. Holst and S. Hong. EPA Memorandum dated 7/2/1985.

Perry, Mark. “PP# 7F04896. Clomazone (Reg. No. 279-3158) in/on Rice. Evaluation of 

Analytical Methods and Residue Data. MRID Nos. 44348401 and 44348402. DP Barcode 

D242601. PC Code 125401” EPA Memorandum to Ed Zager, dated 1/29/98.

Vogel, Dana, “PP#9F06056. Clomazone (i.e. Command7 3ME) in/on Sugarcane. Evaluation of 

Residue Data and Analytical Methods for Sugarcane. MRID#s 449104-02-04. Chemical 

125401. Barcode D272158.” EPA memorandum to Jim Tompkins, dated 14 Jan 2001. 

RDI: TMorton:8/26/2013
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Appendix I: International Residue Status

Clomazone (PC Code 125401; Date of Request 8/21/13)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex3

40 CFR 180.425

Plants: Clomazone, 2-[(2-

chlorophenyl)methyl]-4,4-

dimethyl-3-isoxazolidinone

2-(2-cholorobenzyl)-4,4-dimethyl1,2-oxazolidin-3-oneNone

Commodity1 Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico2 Codex3

Brassica, stem and head subgroup 

5A

0.1

Rhubarb 0.3

Pea, Southern, succulent seed 0.05

Pea, Southern, dry seed 0.05

Pea, Southern, hay 0.05

Completed: M. Negussie; 08/26/13

1

Includes only commodities of interest for this action. Tolerance values should be the HED recommendations and 

not those proposed by the applicant.

2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.

3 * = absent at the limit of quantitation; Po = postharvest treatment, such as treatment of stored grains. PoP = 

processed postharvest treated commodity, such as processing of treated stored wheat. (fat) = to be measured on the 

fat portion of the sample. MRLs indicated as proposed have not been finalized by the CCPR and the CAC.
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Appendix II

Clomazone

Rhubarb

US

2 x 1.5 or 1.0 lb ai/A

Total number of data (n) 8

Percentage of censored data 25%

Number of non-censored data 6

Lowest residue 0.022

Highest residue 0.180

Median residue 0.042

Mean 0.059

Standard deviation (SD) 0.051

Correction factor for censoring (CF) 0.833

Proposed MRL estimate

- Highest residue 0.180

- Mean + 4 SD 0.263

- CF x 3 Mean 0.146

Unrounded MRL 0.263

Rounded MRL 0.3

Residues (mg/kg)

0.030 *

0.035

0.022 *

0.036

0.047

0.180

0.067

0.051