UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

 

MEMORANDUM

Date: February 22, 2011

SUBJECT: Mefenpyr-diethyl (Safener HOE 107892)

Sorghum and Grass Grown for Seed.

and Residue Data. 

PC Code: 811800 (multiple actives 035302, 

128920, 000692)

Decision No.: 425581

Petition No.: 9F7679 (related to 9F7678 and 

9F7680)

Risk Assessment Type: NA

TXR No.: None

MRID No.: 47815001, 47815002

 

 

FROM: Alexandra LaMay, Biologist

Toiya Goodlow, Chemist

Risk Assessment Branch VII

Health Effects Division (7509P)

THROUGH: Christine Olinger, Chemist

Michael S. Metzger, Branch Chief

Risk Assessment Branch VII

Health Effects Division (7509P)

TO: Bethany Benbow

Herbicide Branch

Registration Division (7505P)

Executive Summary

Mefenpyr-diethyl (AE F107892, 

Safeners are substances added to herbicidal active ingredients in formulations to protect crops 

from potential adverse effects of the herbicides. Although safeners are not considered to be 

pesticidal by the Agency, they are often similar in molecular stru

the Agency has established some tolerances for safeners including 

Page 1 of 20

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND

 POLLUTION PREVENTION

(Safener HOE 107892). Petition for Section 3 Registration of 

Sorghum and Grass Grown for Seed. Revised Summary of Analytical Chemistry

811800 (multiple actives 035302, DP Barcode: 380768

Registration No.: NA

(related to 9F7678 and Regulatory Action: Section 3 Registration

Case No.: NA

CAS No.: 135590-91-9

47815001, 47815002 40 CFR: 180.509

LaMay, Biologist

Toiya Goodlow, Chemist

Risk Assessment Branch VII

Health Effects Division (7509P)

, Chemist

Michael S. Metzger, Branch Chief

Risk Assessment Branch VII

Division (7509P)

Herbicide Branch

Registration Division (7505P)

AE F107892, HOE 107892) is a safener used with several herbicides. 

Safeners are substances added to herbicidal active ingredients in formulations to protect crops 

from potential adverse effects of the herbicides. Although safeners are not considered to be 

pesticidal by the Agency, they are often similar in molecular structure to active pesticides. 

the Agency has established some tolerances for safeners including mefenpyr-diethyl

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF CHEMICAL SAFETY AND

POLLUTION PREVENTION

Registration of 

Summary of Analytical Chemistry

Section 3 Registration

HOE 107892) is a safener used with several herbicides. 

Safeners are substances added to herbicidal active ingredients in formulations to protect crops 

from potential adverse effects of the herbicides. Although safeners are not considered to be 

cture to active pesticides. Thus, 

diethyl.
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Bayer CropScience has requested new uses of mefenpyr-diethyl on sorghum and grass grown for 

seed (PP #9F7679). Huskie herbicide is an emulsifiable concentrate which also contains active 

ingredients (ais) bromoxynil and pyrasulfotole; related petitions 9F7678 and 9F7680 were 

submitted to support the establishment of tolerances for these ais. In conjunction with the new 

uses on sorghum and grass grown for seed, the petitioner is proposing the establishment of 

permanent tolerances for residues of the herbicide safener mefenpyr-diethyl (1-(2,4-

dichlorophenyl)-4,5-dihydro-5-methyl-1H-pyrazole-3,5-dicarboxylic acid, dichlorophenylpyrazoline metabolites at a rate of 0.053 pound safener per acre in/on the following 

commodities:

Grass, forage ................................................................1.5 ppm

Grass, hay ...................................................................0.05 ppm

Sorghum, forage ...........................................................0.1 ppm

Sorghum, grain ..........................................................0.01 ppm

Sorghum, stover ........................................................0.05 ppm

The metabolism of mefenpyr-diethyl in plants (barley) and animals (goat, rat, and hen) is well 

understood. Identified metabolic pathways are substantially similar in plants and animals. EPA 

has determined that mefenpyr-diethyl parent and its three 2,4-dichlorophenyl-pyrazoline 

metabolites: AE F113225, AE F109453, and AE F094270 (also known as HOE 113225, HOE 

109453, and HOE 094270) are the residues of concern for risk assessment and tolerance setting 

purposes.

An enforcement method for plants entitled “An Analytical Method for Determination of 

Residues of AE F107892 (mefenpyr-diethyl) and its Metabolites in Wheat and Barley by Gas 

Chromatography using Mass Selective Detection (Report Supplement to EPA MRID 45457401)” 

is available. Radiovalidation and independent laboratory validation (ILV) data have been 

submitted for the plant method. The Agency determined that this method is suitable for crop

tolerance enforcement of mefenpyr-diethyl and the three metabolites AE F094270, AE F113225, 

and/or AE F109453. 

In the data-collection method used in the grass and sorghum field trial studies, the residues of 

mefenpyr-diethyl and its metabolites AE F113225, AE F109453, and AE F094270 were 

quantitated by high pressure liquid chromatography with electrospray ionization /tandem mass 

spectrometry (LC-MS/MS). The lower limit of method validation (LLMV) for each analyte was 

0.10 ppm in sorghum and grass forage, 0.01 ppm in sorghum grain, and 0.05 ppm in sorghum 

stover and grass hay. The method is acceptable based on concurrent recoveries.

Multiresidue method testing data are available for mefenpyr-diethyl and its metabolites. 

Mefenpyr-diethyl and its metabolites have been screened through FDA Multiresidue Method 

Protocols A, B, C, D, E and F. Mefenpyr-diethyl and AE F094270 were recovered through 

protocol C and partially recovered through protocol D. AE F113225 and AE F109453 were not 

recovered through any of the protocols tested. No additional multiresidue testing is required. 

Adequate confined rotational crop data for mefenpyr-diethyl are available. [Phenyl14C] 

HOE 107892 (mefenpyr-diethyl parent) was applied to soil at a rate significantly higher than the 
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proposed use rate. Spinach, carrot, and wheat were planted back at 29 days and 1 year. Based 

on the results of the residue uptakes, HED recommended a 30-day plant-back interval (PBI) for 

leafy, fruiting, and root vegetables, and 12-month PBI for all other crops other than wheat and 

barley, which can be replanted at any time.

There are livestock feedstuffs associated with the proposed crop tolerances. These feedstuffs 

include grass forage, grass hay, sorghum forage, sorghum grain and sorghum stover. While the 

addition of this grass forage livestock feed item has increased the dairy cattle livestock dietary

burden slightly, a review of the available metabolism studies indicates that no new or increased 

livestock tolerances are needed to support this action. However, the petitioner is advised that 

any proposed future amendments which impact residues in feed items or any new uses on new 

feed items may trigger the need for animal feeding studies.

Analytical standards for mefenpyr-diethyl, mefenpyr dimethyl metabolite, mefenpyr ethyl 

methyl, and mefenpyr monoethyl (AEF113225) are currently available in the EPA National 

Pesticide Standards Repository. The analytical standards for mefenpyr impurity and metabolite 

of mefenpyr diethyl have expired; the registrant must ensure that analytical standards are 

available for the parent chemical and all metabolites.

No Codex, Canadian, or Mexican maximum residue limits (MRLs) are established for residues 

of mefenpyr-diethyl and metabolites in crop or livestock commodities; therefore, there are no 

issues with international harmonization raised by this action. 

Regulatory Recommendations and Residue Chemistry Deficiencies

Provided RD assures that the petitioner submits a revised Section F as noted below, there are no 

residue chemistry issues that would preclude granting a registration for use of mefenpyr-diethyl 

as a safener in/on grass grown for seed and sorghum. 

The proposed uses and the submitted data support the following tolerances for residues of the 

herbicide safener mefenpyr-diethyl (1-(2,4-dichlorophenyl)-4,5-dihydro-5-methyl-1H-pyrazole3,5-dicarboxylic acid, diethyl ester) and its 2,4-dichlorophenyl-pyrazoline metabolites in/on the 

following crop commodities:

Grass, forage ................................................................1.6 ppm

Grass, hay .....................................................................0.2 ppm

Sorghum, forage ...........................................................0.4 ppm

Sorghum, grain ..........................................................0.04 ppm

Sorghum, stover ..........................................................0.2 ppm

Note to RD: The tolerance expression should be changed as described below: 

Tolerances are established for residues of the safener mefenpyr-diethyl, 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 the sum of mefenpyr-diethyl (1-(2,4-dichlorophenyl)-4,5-dihydro5-methyl-1H-pyrazole-3,5-dicarboxylic acid, diethyl ester) and its 2,4-

dichlorophenyl-pyrazoline metabolites, calculated as the stoichiometric equivalent 
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of mefenpyr-diethyl, in or on the commodity.

860.1480 Livestock Feeding Study

The petitioner is advised that any proposed future amendments which impact residues in feed 

items or any new uses on new feed items may trigger the need for animal feeding studies. The 

livestock feeding study should include validation data for the parent compound and all 

metabolites.

860.1550 Proposed Tolerances

The petitioner is required to submit a revised Section F to correct the tolerance expression to be 

consistent with the guidance issued 5/27/10 (S. Knizner) as well as the correct commodity

definition for the requested crops (presented in Table 8). The tolerance expression should be 

changed as described below: 

Tolerances are established for residues of the safener mefenpyr-diethyl, 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 the sum of mefenpyr-diethyl (1-(2,4-dichlorophenyl)-4,5-dihydro5-methyl-1H-pyrazole-3,5-dicarboxylic acid, diethyl ester) and its 2,4-

dichlorophenyl-pyrazoline metabolites, calculated as the stoichiometric equivalent 

of mefenpyr-diethyl, in or on the commodity.

In addition, the tolerances for canola seed, soybean seed, soybean forage, and soybean hay 

should be moved from section (a) to section (d). The introductory paragraph in section (d) 

should read as follows:

Tolerances for are established for the indirect or inadvertent residues of 

mefenpyr-diethyl, including its metabolites and degradates, in or on the 

commodities identified in the table below. Compliance with the tolerance levels 

specified below is to be determined by measuring only the sum of mefenpyrdiethyl (1-(2,4-dichlorophenyl)-4,5-dihydro-5-methyl-1H-pyrazole-3,5-

dicarboxylic acid, diethyl ester) and its 2,4-dichlorophenyl-pyrazoline 

metabolites, calculated as the stoichiometric equivalent of mefenpyr-diethyl, in or 

on the commodity.

A human health risk assessment is forthcoming in a separate document.

Background

Mefenpyr-diethyl is an herbicide safener used in combination with several herbicides developed 

by Bayer CropScience for agricultural use on cereal grains. The nomenclature of mefenpyrdiethyl is summarized in Table 1, and the physicochemical properties are summarized in Table 2.
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Table 1. Mefenpyr-Diethyl Nomenclature.

Chemical structure

Common name Mefenpyr-diethyl

Company experimental name AE F107892, HOE 107892

IUPAC name (RS)-1-(2-,4-dichlorophenyl)-5-methyl-2-pyrazoline-3,5-dicarboxylic acid

CAS name 1-(2,4-dichlorophenyl)-4,5-dihydro-5-methyl-1H-pyrazole-3,5-dicarboxylic acid, 

diethyl ester

CAS registry number 135590-91-9

End-use product (EP) PUMA 1EC, Silverado, Rimfire, Osprey, Olympus Flex,

AE 0317309 02 SE06 and AE 0317309 03 EC23

Chemical structure of

AE F094270 (HOE 094270) 

metabolite

Chemical structure of

AE F109453 (HOE 109453) 

metabolite

Chemical structure of

AE F113225 (HOE 113225) 

metabolite

O

H3C O

O

O

CH3

N N

Cl Cl

H C3

N N

Cl Cl

H C3 CO2H

N N

Cl Cl

H C3

CO2H

HO2C

N N

Cl Cl

H C3

CO2H

H3CH2COOC
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Table 2. Physicochemical Properties of Mefenpyr-Diethyl.

Parameter Value Reference

Melting point/range 50-52 oC

43-47 oC

MRID 43984109

pH Was not carried out, because mefenpyrdiethyl technical is practically insoluble 

and nondispersible in water.

MRID 43984109

Density (20 oC) 1.31 g/cm3at 20oC MRID 43984109

Water solubility (20 oC) 0.017 g/L at pH 0.9

0.020 g/L at pH 6.2

pH 10 solubility not determined due to 

compound hydrolysis

MRID 43984109

Solvent solubility (20 oC) Methanol >400 g/L

isopropanol 151 g/L

n-hexane 35 g/L

toluene >400 g/L

dichloromethane >500 g/L

acetone >500 g/L

ethyl acetate >400 g/L

dimethylsulfoxide >500 g/L

polyethylene glycol 151 g/L

sesame oil 56 g/L

MRID 43984109

Vapor pressure (20 oC) 6.3 x 10-6Pa MRID 44024001

Dissociation constant, pKa Neither acidic nor basic functional groups. 

Dissociation, if any, is expected to be 

negligible.

MRID 43984109

Octanol/water partition coefficient, 

Log(KOW)

3.83 at pH 6.3 and 21 oC MRID 43984109

UV/visible absorption spectrum (nm) Primary λmax = <200

Secondary λmax = 305

MRID 43984109

860.1200 Directions for Use

The end-use product relevant to the petition (PP#9F7679) is HUSKIETM Herbicide (EPA Reg. 

No. 264-1023), an emulsifiable concentrate (EC) formulation containing 3.3% pyrasultotole, 

13.4% bromoxynil octanoate, and 12.9% bromoxynil heptanoate as the active ingredients 

(equivalent to 0.31 lb ae/gal of pyrasulfotole and 1.75 lbs/gal of bromoxynil). In support of the 

proposed use of HUSKIETM Herbicide on sorghum and grasses grown for seed, the petitioner 

submitted a draft label for HUSKIETM Herbicide. The proposed label states that mefenpyrdiethyl is a safener in the Huskie® Herbicide. Mefenpyr-diethyl, also known as Diethyl-1-(2,4-

Dichlorophenyl)-5-Methyl-2-Pyrazolin-3,5-Dicarboxylate or HOE 107892 is a safener currently 

used with several herbicides on cereal grain. Mefenpyr-diethyl is formulated in HUSKIETM 

Herbicide (containing 0.08 lbs of mefenpyr-diethyl per gallon) and is proposed at application 

rates of 0.010 lbs ai/A for sorghum and 0.009 lbs ai/A for grass grown for seed/conservation 

reserve land. The proposed uses include a maximum of two applications per season for grass 

grown for seed and sorghum. Mefenpyr-diethyl has current registrations for cereal grains 

(wheat, barley, oats, rye). The maximum seasonal use rate is 0.053 lb safener/A in registered 

end-use products. The pre-harvest interval (PHI) for sorghum is 60 days, and the PHI for grass 

hay is 30 days. A summary of the proposed use directions for sorghum and grasses grown for 
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seed is presented in Table 3A.

Table 3A. Summary of Proposed Use Directions of Huskie® Herbicide (EPA Reg. No. 264-1023)

Applic. Timing, Type, and 

Equip.

Applic. 

Rate 

(lb 

safener/A)

Max. No. 

Applic. 

per 

Season

Max. 

Seasonal 

Applic. 

Rate

(lb ae/A)

PHI

(days) Use Directions and Limitations

Grasses Grown for Seed/ Conservation Reserve Land

Broadcast preemergence and 

postemergence application to 

annual and perennial grasses 

grown for seed and 

conservation reserve program 

acres (CRP)

Ground/Aerial/ Chemigation

0.009 2 0.018 30

Apply 13.5 – 15 ounces of 

HUSKIETM Herbicide per 

application per acre. Two 

applications can be made per year 

separated by at least 30 days. Do 

not apply more than 30 ounces of 

HUSKIETM Herbicide per acre 

per year. Grass forage may be 

cut or grazed any time after 

application but do not cut for hay 

within 30 days after treatment.

Sorghum

Broadcast postemergence

application to actively growing 

sorghum 

Ground/Aerial

0.01 2 0.02 60

Apply 12.8-16 ounces of 

HUSKIETM Herbicide per acre. 

Apply the appropriate dosage 

broadcast in a minimum of 10 or 

more gallons of water per acre. 

In denser canopies, 15 gallons of 

water per acre should be used. 

Two applications of HUSKIETM

Herbicide with a total of 32 

ounces may be applied per year. 

A maximum 16 ounces of 

HUSKIETM Herbicide per acre 

per application may be applied. 

There must be an interval of at 

least 11 days between treatments. 

Do not apply through any type of 

irrigation system. Do not graze 

or cut for forage 7 days after a 

HUSKIETM Herbicide 

application. Do not harvest for 

grain or stover within 60 days of 

a HUSKIETM Herbicide 

application.

General Use Directions

Mefenpyr-diethyl is formulated in HUSKIETM Herbicide and is proposed at 0.010 lbs ai/A for 

sorghum, and 0.009 lbs ai/A for grass grown for seed/conservation reserve land, with a 

maximum of two applications per season for grass grown for seed and sorghum. 
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Spray additives: The draft label specifies that spray additives cleared for use on growing crops

under 40 CFR §180.1001 may be used in the spray mixture. A nonionic surfactant (NIS), 

ammonium nitrogen fertilizer or other adjuvants may be used.

Application equipment: Ground applications are to be made in a minimum of 10 gal/A, and 

aerial applications are to be made in a minimum of 5 gal/A. HUSKIETM Herbicide applications 

are not to be made through any type of irrigation equipment for sorghum. HUSKIETM alone or 

in tank mixture with other products on the label, which are registered for chemigation

application, may be applied to grasses in irrigation water at label-recommended rates.

Tank mixtures with other products registered for use on grasses grown for seed and sorghum: 

The draft label provides mixing procedures for tank mixes and specifies tank mix partners for 

sorghum and grasses. The use directions state that, for tank mix combinations, the 

recommendations, restrictions, and limitations for all products must be followed and that the 

most restrictive labeling is to apply. 

For application in sorghum, HUSKIE

TM may be tank mixed with other pesticide products 

registered for use in this way and timing in sorghum. For weed control, the proposed label states 

that HUSKIETM can be tank mixed with 0.25 – 1.0 pound atrazine per acre, and HUSKIETM plus 

atrazine can be tank mixed with phenoxy broadleaf herbicides (such as 2,4-D or dicamba) as 

needed. For insect control, the proposed label states that HUSKIETM Herbicide can be tank 

mixed with Baythroid®XL provided the proper timing for insect and weed control are the same. 

The label prohibits HUSKIETM to be tank mixed with Lorsban as unacceptable crop response 

may occur.

For applications in annual and perennial grasses grown for seed and conservation reserve 

program acres (CRP), HUSKIE

TM may also be tank mixed with other pesticide products 

registered for use in this way and timing in grasses. For weed control, the proposed label states 

that HUSKIETM can be tank mixed with Puma®, Nortron, Rely, 2-4-D ester/amine, AimTM, 

bromoxynil products (Bronate AdvancedTM, Buctril®), Curtail M/Curtail®, Dicamba, Goal, 

Glean, MCPA ester/ MCPA amine, Sencor®, Starane®/Starane NXT/ Starane Ultra, and 

WideMatchTM. For insect control, HUSKIETM may be tank mixed with Baythroid®XL, Capture, 

Lorsban®, Mustang MaxTM, or Warrior® insecticides provided that proper timing for insect and 

weed control are the same. For disease control, HUSKIE

TM Herbicide may be tank mixed with 

Absolute, Tilt®, Quadris®, QuiltTM or Bravo fungicides when timing for application of each 

tank mix partner is the same.

Rotational crop plantback intervals: The draft label specifies that the rotational crops listed in 

Table 3B may be planted after applying HUSKIETM at recommended rates.
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Table 3B. Rotational Crop Plantback Intervals Listed on the HUSKIETM Herbicide.

Crop To Be Planted Minimum Rotation Interval

(Days or Months After Last HUSKIETM

Application)

Wheat, Barley, Oats, Rye and Triticale 1 month

Alfalfa 1, Millet, Sorghum (grain) and Soybeans 4 months

Canola, Canaryseed, Chickpeas, Corn, Dry Beans, Flax, Field 

Peas, Green Beans, Green Peas, Lentils 2, Mustards, Potatoes, 

Safflower, Sunflowers, and Sugarbeets

9 months

* Do not plant any rotational crop within 30 days following a HUSKIETM Herbicide application.

1 Thorough tillage prior to planting alfalfa and a minimum of 12 inches of rainfall, overhead, furrow or flood 

irrigation or any combination of these water sources totaling 12 inches is required between the time following a 

HUSKIETM Herbicide application and the time of alfalfa seeding.

2

 For Lentils, 9 month minimum rotation interval for all states except 18 months in MN, MT, ND and SD.

Conclusions. The available draft label for HUSKIETM Herbicide is adequate to allow evaluation 

of residue data relative to the proposed use on grasses grown for seed and sorghum. 

860.1300 Nature of the Residue - Plants

Residue Chemistry Memo DP#s 238730, 271364, 264319, 276208, 11/22/02, Y. Donovan (PP# 7F04850)

The metabolism of mefenpyr-diethyl in plants (barley) is well understood. Identified metabolic 

pathways are substantially similar in plants and animals (goat, rat, and hen). EPA has 

determined that mefenpyr-diethyl parent and its three 2,4-dichlorophenyl-pyrazoline metabolites 

(AE F113225, AE F109453, and AE F094270) are the residues of concern for tolerance setting 

purposes.

860.1300 Nature of the Residue - Livestock

Residue Chemistry Memo DP#s 238730, 271364, 264319, 276208, 11/22/02, Y. Donovan (PP# 7F04850)

Meeting of Metabolism Assessment Review Committee, DP# 263039, 3/27/00, Y. Donovan 

The qualitative nature of the residue in animals is adequately understood based on acceptable 

studies conducted on goats and laying hens. The metabolic pathways are the same as those in 

plants. HED has concluded that the regulated residues in animal commodities should be the 

parent compound and those free metabolites AE F113225, AE F109453, and AE F094270.

860.1340 Residue Analytical Methods

Residue Chemistry Memo DP#s 238730, 271364, 264319, 276208, 11/22/02, Y. Donovan (PP# 7F04850); DERs for 

MRIDS 47815001 and 47815002, T. Goodlow, 2/22/11.

Plant commodities

Enforcement method: In a previous petition (PP#7F04850), the petitioner proposed a GC/MSD 

method, entitled “An Analytical Method for Determination of Residues of AE F107892 

(mefenpyr-diethyl) and its Metabolites in Wheat and Barley by Gas Chromatography using Mass 

Selective Detection (Report Supplement to EPA MRID 45457401)” for the enforcement of 

tolerances for barley and wheat commodities. Radiovalidation and ILV data have been 
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submitted for this method. This method has been forwarded to Agency analytical lab for petition 

method validation, and the Agency analytical lab concluded that this method is suitable for food 

tolerance enforcement of mefenpyr-diethyl (AE F107892) and the three metabolites AE 

F094270, AE F113225, and/or AE F109453. 

Data-collection method: Samples of sorghum forage, grain, and stover and grass forage and hay

were analyzed for residues of mefenpyr-diethyl, and its metabolites AE F094270, AE F109453, 

and AE F113225 using LC-MS/MS Bayer Method 01032, as modified by RAAIP025 Method 

Modification-01, and with minor modifications by Pyxant Labs Inc. to improve recovery and 

chromatography. Mefenpyr-diethyl metabolite standards were prepared in individual analyte 

equivalents and residues were converted to parent equivalents during calculations.

Residues of mefenpyr-diethyl and its metabolites AE F094270, AE F113225 and AE F109453 

were extracted from homogenous 5.0-g samples of grass or sorghum with an acetone/water 

mixture using a blender. After filtration and clean up of the extracts, the solutions were subjected 

to HPLC-MS/MS analysis. HPLC separation was performed with a Luna C18(2), 3μm, 150 mm 

× 2.0 mm HPLC column. The LLMVs were 0.10 ppm in sorghum and grass forage, 0.01 ppm in 

sorghum grain, and 0.05 ppm in sorghum stover and grass hay. 

The above method was adequately validated by the petitioner, and is deemed adequate for datagathering purposes.

Animal Commodities

No new livestock tolerances are required; therefore a discussion of an enforcement method for 

those commodities is not relevant to this risk assessment.

860.1360 Multiresidue Methods

Residue Chemistry Memo D358191, 11/25/08, D. Davis (PP# 7E7224)

Adequate multiresidue method data have been submitted and reviewed by the Agency. MRID 

45447701 entitled Pam I Multiresidue Protocol Testing for Mefenpyr-Diethyl and Metabolites 

(AE F113225, AE F109453, and AE F094270) provided sufficient data to validate the 

multiresidue method testing of mefenpyr-diethyl and its metabolites through FDA Multiresidue 

Method Protocols A, B, C, D, E and F. Mefenpyr-diethyl and AE F094270 were recovered 

through protocol C and partially recovered through protocol D. AE F113225 and AE F109453 

were not recovered through any of the protocols tested. 

No additional multiresidue testing is required. However, multiresidue method testing appears to 

have limited use for this safener, as two key metabolites are not detected through any of the 

tested protocols. The results of the multiresidue testing have been forwarded to the U.S. FDA 

for further evaluation.
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860.1380 Storage Stability

Residue Chemistry Memo DP#s 238730, 271364, 264319, 276208, 11/22/02, Y. Donovan (PP# 7F04850); DERs for 

MRIDS 47815001 and 47815002, T. Goodlow, 2/22/11.

No storage stability data were submitted with the subject petition. Adequate storage stability

data are available for residues of mefenpyr-diethyl and its metabolites AE F094270, AE 

F109453, and AE F113225 in/on barley. Fortified residues of mefenpyr-diethyl and its 

metabolite AE 094270 are stable during frozen storage for up to 30 months in/on barley grain; 

and fortified residues of mefenpyr-diethyl and its metabolites AE 094270, AE 113225, and 

AE 109453 are stable during frozen storage for up to 30 months in/on barley shoots and straw. 

The maximum storage interval from sampling to extraction prior to analysis of mefenpyr-diethyl

was 384 days for grass forage, 372 days for grass hay, 360 days for sorghum forage, 303 days for 

sorghum grain, and 287 days for sorghum stover. Available barley storage stability results were 

translated to grass and sorghum raw agricultural commodities. The barley storage stability data 

adequately support the storage durations and conditions of samples from the submitted grass and 

sorghum field trial studies.

The storage durations and conditions of samples from the crop field trials submitted to support 

this petition are presented in Table 4.

Table 4. Summary of Storage Conditions for Mefenpyr-diethyl and Metabolites AE F094270, AE F113225, 

AE F109453.

Matrix Maximum Storage 

Temperature1 (°C)

Actual Maximum 

Storage Duration2

(weeks)

Interval of Demonstrated Storage Stability3

Grass forage <0 227-384 days 

(7.3-12.4 months)

30 months for mefenpyr-diethyl and AE 

094270 in/on barley grain.

30 months for mefenpyr-diethyl, AE 094270, 

AE 113225, and AE 109453 in/on barley 

shoots and straw.

Grass hay <0 185-372 days

(6.0-12.0 months)

Sorghum Forage <0 202 to 360 days (6.5 to 

11.6 months)

30 months for mefenpyr-diethyl and AE 

F094270 in/on barley grain.

30 months for mefenpyr-diethyl, AE F094270, 

AE F113225, and AE F109453 in/on barley 

shoots and straw.

Sorghum Grain <0 194 to 303 days (6.3 to 

9.8 months)

Sorghum Stover <0 179 to 287 days (5.8 to 

9.3 months)

1

Samples were stored at the field site and analytical laboratory at <0°C. The storage temperature at BRP between 5/16/2008 and 

2/5/2009 was not recorded, however, the freezers were working properly and all samples remained frozen. 

2

Storage duration is from date of sampling to date of extraction. Samples were analyzed within 0 to 2 days of extraction.

3Refer to DP# 238730, 11/22/02, Y. Donovan

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.
Mefenpyr diethyl Summary of Analytical Chemistry and Residue Data Barcode: D380768

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860.1480 Meat, Milk, Poultry, and Eggs

Residue Chemistry Memo DP#s 238730, 271364, 264319, 276208, 11/22/02, Y. Donovan (PP# 7F04850)

HED DEEM Memo DP# 286489, 11/22/02, Y. Donovan

Tolerances of 0.1 ppm have been established for residues of the herbicide safener mefenpyrdiethyl and its 2,4-dichlorophenyl-pyrazoline metabolites in meat byproducts of cattle, goat, hog, 

horse, and sheep [40 CFR §180.509(a)]. 

There are livestock feedstuffs associated with the proposed crop tolerances. These feedstuffs 

include grass forage, grass hay, sorghum forage, sorghum grain and sorghum stover. The 

residues expected in grass forage ruminant feedstuffs increases the dairy cattle livestock dietary 

burden from 0.57 ppm to 2.9 ppm (Table 5). Based on the tissue/feed ratios estimated from the 

ruminant metabolism study, the maximum residues expected in liver would be 0.01 ppm and 

kidney would be 0.04 ppm, which are both below the established tolerance of 0.1 ppm. The 

maximum residues estimated for all other edible commodities were below 0.01 ppm, again using 

the tissue/feed residues from the metabolism study and the maximum reasonable dietary burden. 

According to the metabolism study, most of the administered dose was eliminated in the urine, 

indicating considerable absorption and metabolism, and minimal accumulation. Residues in 

milk collected throughout the study were low and did not increase, supporting the argument that 

residues are not likely to significantly increase in the feeding study. Revised meat and milk 

tolerances are not required. The existing meat by-product tolerances are sufficient, based on the 

metabolism study, as estimates of kidney and liver residues based on the new dietary burden are 

still well below 0.1 ppm. Detectable residues in other meat/milk matrices are not expected, and 

tolerances are not required. 

Table 5. Proposed Livestock dietary burdens for Mefenpyr-diethyl (Using revised OPPTS Guidance)

Feedstuff Type Tolerance (ppm) % Dry Matter % Diet Dietary Contribution 

(ppm)

Beef Cattle

Wheat, straw R 0.5 88 10 0.0568

Untreated R R - - 5 0

Barley, grain CC 0.05 88 50 0.028

Untreated CC CC - - 30 0

Canola, seed PC 0.02 88 5 0.0011

TOTAL 100 0.0859

Dairy Cattle

Grass, forage R 1.6 25 45 2.88

Barley, grain CC 0.05 88 45 0.025

Canola, seed PC 0.02 88 10 0.0023

TOTAL 100 2.91

R = roughage, CC = carbohydrate concentrate, PC = protein concentrate

860.1500 Crop Field Trials

DERs for MRIDS 47815001 and 47815002, T. Goodlow, 2/22/11.

Bayer CropScience has submitted field trial data for the product HUSKIETM herbicide on grass 
Mefenpyr diethyl Summary of Analytical Chemistry and Residue Data Barcode: D380768

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(Bermuda, bluegrass, and fescue). HUSKIETM herbicide is an emulsifiable concentrate mixture 

containing pyrasulfotole (37.5 g ai/L), bromoxynil (210 g ai/L), and mefenpyr-diethyl safener 

(9.38 g ai/L in formulation). Twelve trials were conducted in the United States and Canada 

during the 2008 growing season. The treatment plots each received two applications of the 

formulated product at a target rate of 16.1 fl oz HUSKIE

TM/A/application, which corresponds to 

0.010 lb mefenpyr-diethyl/A/application (0.011 kg mefenpyr-diethyl/ha/application). Total

application rates ranged from 31 to 37 fl oz HUSKIETM/A/season, with a 27- to 30-day retreatment interval (RTI). Grass forage samples were collected at target pre-harvest interval (PHI) 

of 0 days and 7 days. Grass hay samples were collected at a target PHI of 30 days. A residue 

decline trial was also conducted at one site.

After two applications of HUSKIETM Herbicide to grass, total mefenpyr-diethyl residues in grass 

forage ranged from below the LLMV (<0.40 ppm) to 1.59 ppm at a PHI of 0 days and from 

below the LLMV to 1.36 ppm at a PHI of 7 to 11 days. In grass hay samples, residues of 

mefenpyr-diethyl and its metabolites were all below the LLMV (0.05 ppm each). Residue 

decline data showed that residues of mefenpyr-diethyl and metabolites decreased with time in 

grass forage and hay. The results of the grass field trials are summarized in Table 6 below.

TABLE 6. Summary of Grass Residue Data from Crop Field Trials with Mefenpyr-diethyl.

Matrix Total Applic. Rate

(lb a.i./A) (kg a.i./ha)

PHI 

(days)

Residue Levels1,2 (ppm)

n Min. Max. HAFT3 Median

(STMdR)

Mean

(STMR)

Std. Dev.

4

Mefenpyr-diethyl

Grass Forage 0.019 - 0.023

(0.021 - 0.026)

0 24 <0.10 1.09 1.04 0.295 0.351 0.278

7-11 24 <0.10 0.931 0.927 <0.10 0.233 0.265

Grass Hay 0.019 - 0.020

(0.021 - 0.023) 28-31 24 <0.05 <0.05 <0.05 <0.05 <0.05 N/A

AE F094270

Grass Forage 0.019 - 0.023

(0.021 - 0.026)

0 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

7-11 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

Grass Hay 0.019 - 0.020

(0.021 - 0.023) 28-31 24 <0.05 <0.05 <0.05 <0.05 <0.05 N/A

AE F113225

Grass Forage 0.019 - 0.023

(0.021 - 0.026)

0 24 <0.10 0.33 0.31 <0.10 0.14 0.077

7-11 24 <0.10 0.24 0.23 <0.10 0.111 0.036

Grass Hay 0.019 - 0.020

(0.021 - 0.023) 28-31 24 <0.05 <0.05 <0.05 <0.05 <0.05 N/A

AE F109453

Grass Forage 0.019 - 0.023

(0.021 - 0.026)

0 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

7-11 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

Grass Hay 0.019 - 0.020

(0.021 - 0.023) 28-31 24 <0.05 <0.05 <0.05 <0.05 <0.05 N/A

Total Mefenpyr-diethyl Residues

Grass Forage 0.019 - 0.023

(0.021 - 0.026)

0 24 <0.40 1.59 1.54 0.60 0.69 0.34

7-11 24 <0.40 1.36 1.36 0.40 0.54 0.30

Grass Hay 0.019 - 0.020

(0.021 - 0.023) 28-31 24 <0.20 <0.20 <0.20 <0.20 <0.20 N/A

1 LLMV = 0.10 ppm in grass forage and 0.05 ppm in grass hay. LOD for mefenpyr-diethyl = 0.0141 ppm for forage and 0.0111 

for hay. 
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2 Total (ppm) = Sum of mefenpyr-diethyl (ppm), AE F094270 (ppm), AE F113225 (ppm), and AE F109453 (ppm). LLMV 

value was used in calculations when values were <LLMV.

3HAFT = Highest Average Field Trial. 

4NA = not applicable because all replicates were <LLMV.

Bayer CropScience has submitted field trial data for the product HUSKIETM herbicide on 

sorghum grain, forage and stover. Twelve trials were conducted in the United States during the 

2008 growing season. The treatment plots each received two applications of the formulated 

product at a target rate of 16.1 fl oz HUSKIE

TM/A/application, which corresponds to 0.010 lb 

mefenpyr-diethyl/A/application (0.011 kg mefenpyr-diethyl/ha/application). Total application

rates ranged from 32 to 33 fl oz HUSKIE

TM/A/season. The RTI ranged from 11 to 16 days. 

Sorghum forage samples were collected at target PHI of 0 days and 7 days and also at earliest 

commercial harvest (ECH) (BBCH 81, beginning of ripening, to BBCH 87, hard dough), which 

corresponded to PHIs of 32 to 82 days. Sorghum grain and stover samples were collected at a 

target PHI of 60 days. A residue decline trial was also conducted at one site.

After two applications of mefenpyr-diethyl to sorghum, the only residues that were above the 

LLMV were mefenpyr-diethyl and AE F113225 in/on sorghum forage at a PHI of 0 days. 

Mefenpyr-diethyl residues ranged from <LLMV (0.10 ppm) to 1.03 ppm and AE F113225 

residues ranged from <0.10 to 0.12 ppm. Total mefenpyr-diethyl residues (sum of mefenpyrdiethyl and parent equivalents of AE F113225, AE F109453, and AE F094270) ranged from 

<LLMM (0.40 ppm) to 1.34 ppm at a PHI of 0 days in sorghum forage. Total residues of 

mefenpyr-diethyl and its metabolites were undetectable in all sorghum grain and stover samples. 

The residue decline of mefenpyr-diethyl and its metabolites with time in sorghum matrices could 

not be assessed due to residue levels below the LLMV. The results of the sorghum field trials are 

summarized in Table 7 below.

Table 7. Summary of Sorghum Residue Data from Crop Field Trials with Mefenpyr-diethyl.

Matrix

Total 

Applic. Rate

(lb 

a.i./A) (kg 

a.i./ha)

PHI1(days)

Residue Levels2,3,4 (ppm)

n Min. Max. HAFT5 Median

(STMd)

Mean

(STMR)

Std. 

Dev. 6

Mefenpyr-diethyl

Sorghum Forage

0.020

(0.022)

0 24 <0.10 1.03 0.98 0.205 0.291 0.242

5 to 8 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

ECH (32 to 82) 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

Sorghum Grain 56 to 60 24 <0.01 <0.01 <0.01 <0.01 <0.01 N/A

Sorghum Stover 56 to 60 24 <0.05 <0.05 <0.05 <0.05 <0.05 N/A

AE F094270

Sorghum Forage

0.020

(0.022)

0 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

5 to 8 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

ECH (32 to 82) 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

Sorghum Grain 56 to 60 24 <0.01 <0.01 <0.01 <0.01 <0.01 N/A

Sorghum Stover 56 to 60 24 <0.05 <0.05 <0.05 <0.05 <0.05 N/A
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Table 7. Summary of Sorghum Residue Data from Crop Field Trials with Mefenpyr-diethyl.

Matrix

Total 

Applic. Rate

(lb 

a.i./A) (kg 

a.i./ha)

PHI1(days)

Residue Levels2,3,4 (ppm)

n Min. Max. HAFT5 Median

(STMd)

Mean

(STMR)

Std. 

Dev. 6

AE F113225

Sorghum Forage 0.020

(0.022)

0 24 <0.10 0.12 0.11 <0.10 0.101 0.004

5 to 8 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

ECH (32 to 82) 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

Sorghum Stover 56 to 60 24 <0.05 <0.05 <0.05 <0.05 <0.05 N/A

AE F109453

Sorghum Forage

0.020

(0.022)

0 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

5 to 8 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

ECH (32 to 82) 24 <0.10 <0.10 <0.10 <0.10 <0.10 N/A

Sorghum Stover 56 to 60 24 <0.05 <0.05 <0.05 <0.05 <0.05 N/A

Total Mefenpyr-diethyl

Sorghum Forage

0.020

(0.022)

0 24 <0.40 1.34 1.29 0.505 0.592 0.245

5 to 8 24 <0.40 <0.40 <0.40 <0.40 <0.40 N/A

ECH (32 to 82) 24 <0.40 <0.40 <0.40 <0.40 <0.40 N/A

Sorghum Grain 56 to 60 24 <0.02 <0.02 <0.02 <0.02 <0.02 N/A

Sorghum Stover 56 to 60 24 <0.20 <0.20 <0.20 <0.20 <0.20 N/A

1 ECH = Earliest commercial harvest

2 LLMV = 0.10 ppm in forage, 0.01 ppm in grain, and 0.05 ppm in stover. LOD for mefenpyr-diethyl = 0.016 ppm for forage, 

0.00166 ppm for grain, and 0.007 ppm for stover, and 0.0111 for hay. LOD for AE F094270 = 0.0142 ppm for forage, 0.00183 

ppm for grain, and 0.0105 ppm for stover. LOD for AE F113225 = 0.0309 ppm for forage and 0.0231 ppm for stover. LOD for 

AE F109453 = 0.0214 ppm for forage and 0.0179 ppm for stover. 

3 Total (ppm) for forage and stover = Sum of mefenpyr-diethyl (ppm), AE F094270 (ppm), AE F113225 (ppm), and AE 

F109453 (ppm). Residues of AE F094270 (ppm) and AE F113225 (ppm) were undetectable (below the LLMV and LOD 

values). LLMV value was used in calculations when values were <LLMV

4Total (ppm) for grain = Sum of mefenpyr-diethyl (ppm) and AE F109453 (ppm). LLMV value was used in calculations when 

values were <LLMV.

5HAFT = Highest Average Field Trial. 

6NA = not applicable because all replicates were <LLMV.

The submitted grass and sorghum field trial data have been reviewed and are classified as 

scientifically acceptable. An adequate number of trials were conducted in the appropriate 

geographical regions, and samples were analyzed for the residues of concern using an adequate 

method. Storage stability data are also available to adequately support the storage durations and 

conditions from MRIDs 47815001 and 47815002. 

The residue data support the following recommended tolerances:

Grass, forage ................................................................1.6 ppm

Grass, hay .....................................................................0.2 ppm

Sorghum, forage ...........................................................0.4 ppm

Sorghum, grain ..........................................................0.04 ppm
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Sorghum, stover ..........................................................0.2 ppm

860.1520 Processed Food and Feed

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

860.1650 Submittal of Analytical Reference Standards

Analytical standards for mefenpyr-diethyl, mefenpyr dimethyl metabolite, mefenpyr ethyl 

methyl, and mefenpyr monoethyl (AEF113225) are currently available in the EPA National 

Pesticide Standards Repository (personal communication with Theresa Cole, 9/20/10). The 

analytical standards for mefenpyr impurity and metabolite of mefenpyr diethyl have expired, and 

Bayer is required to send an updated Certificate of Analysis (COA) or a new standard. Bayer 

must ensure that analytical standards are available for the parent chemical and all metabolites.

Analytical reference standards must be supplied and supplies replenished as requested by the 

Repository. The reference standards should be sent to the Analytical Chemistry Lab, which is 

located at Fort Meade, to the attention of either Theresa Cole or Thuy Nguyen at the following 

address:

USEPA

National Pesticide Standards Repository/Analytical Chemistry Branch/OPP

701 Mapes Road

Fort George G. Meade, MD 20755-5350

(Note that the mail will be returned if the extended zip code is not used.)

860.1850 Confined Accumulation in Rotational Crops

Residue Chemistry Memo DP#s 238730, 271364, 264319, 276208, 11/22/02, Y. Donovan (PP# 7F04850)

Adequate confined rotational crop studies were reviewed in PP#7F04850. [Phenyl14C] 

mefenpyr-diethyl was applied to soil at a rate significantly higher than the proposed use rate. 

Spinach, carrot, and wheat were planted back at 29 days and 1 year. Based on the results of the 

residue uptakes, HED recommended a 30-day PBI for leafy, fruiting, and root vegetables, and 

12-month PBI for all other crops other than wheat and barley, which can be replanted at any

time.

860.1900 Field Accumulation in Rotational Crops

DER Reference: 47140601.der.doc

Residue Chemistry Memo DP# 342071, 6/3/08, D. Davis (PP# 7E7224)

The submitted limited field rotational crop data for field corn and soybean are adequate. The 

field rotational crop data for field corn will support a 90-day plantback interval (PBI) with no 

need for rotational crop tolerances. The field rotational crop data for soybean will support the 

established soybean and canola tolerances and a 120-day PBI. 
Mefenpyr diethyl Summary of Analytical Chemistry and Residue Data Barcode: D380768

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860.1550 Proposed Tolerances

HED has previously determined that the residues of concern for tolerance setting purposes in 

plant and livestock commodities are mefenpyr-diethyl parent and its three 2,4-dichlorophenylpyrazoline metabolites (HOE 113225, HOE 109453, and HOE 094270). Mefenpyr-diethyl 

tolerances for plant and animal commodities are listed in 40 CFR §180.509 (a) and are expressed 

in terms of the residues of the herbicide safener mefenpyr-diethyl (1-(2,4-dichlorophenyl)-4,5-

dihydro-5-methyl-1H-pyrazole-3,5-dicarboxylic acid, diethyl ester) and its 2,4-dichlorophenylpyrazoline metabolites at a rate of 0.053 pound safener per acre per growing season.

The petitioner needs to submit a revised Section F to correct the tolerance expression to be 

consistent with the guidance issued 5/27/10 (S. Knizner) as well as the correct commodity

definition for the requested crops. The tolerance expression should be changed as described 

below:

Tolerances are established for residues of the safener mefenpyr-diethyl, 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 the sum of mefenpyr-diethyl (1-(2,4-dichlorophenyl)-4,5-dihydro5-methyl-1H-pyrazole-3,5-dicarboxylic acid, diethyl ester) and its 2,4-

dichlorophenyl-pyrazoline metabolites, calculated as the stoichiometric equivalent 

of mefenpyr-diethyl, in or on the commodity.

In addition, the tolerances for canola seed, soybean seed, soybean forage, and soybean hay 

should be moved from section (a) to section (d). The introductory paragraph in section (d) 

should read as follows:

Tolerances for are established for the indirect or inadvertent residues of 

mefenpyr-diethyl, including its metabolites and degradates, in or on the 

commodities identified in the following table below. Compliance with the 

tolerance levels specified below is to be determined by measuring only the sum of 

mefenpyr-diethyl (1-(2,4-dichlorophenyl)-4,5-dihydro-5-methyl-1H-pyrazole-3,5-

dicarboxylic acid, diethyl ester) and its 2,4-dichlorophenyl-pyrazoline 

metabolites, calculated as the stoichiometric equivalent of mefenpyr-diethyl, in or 

on the commodity.

No Codex, Canadian, or Mexican maximum residue limits (MRLs) are established for residues 

of mefenpyr-diethyl and metabolites in crop or livestock commodities. An International Residue 

Limit (IRL) form is appended to this Summary Document and follows this section.

A summary of the recommended tolerances for the petition, to be listed in section (a), are listed 

in Table 8. 
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Table 8. Tolerance Summary for Mefenpyr-diethyl

Commodity Proposed Tolerance 

(ppm)

Recommended 

Tolerance (ppm)

Comments; Correct Commodity 

Definition

Grass Forage 1.5 1.6 Grass, forage

Grass Hay 0.05 0.2 Grass, hay

Sorghum Forage 0.1 0.4 Sorghum, forage

Sorghum Grain 0.01 0.04 Sorghum, grain 

Sorghum Stover 0.05 0.2 Sorghum, stover 

References

DP#s: 238730, 271364, 264319, 276208

Subject: PP# 7F04850: Safener HOE 107892 (mefenpyr-diethyl) – Proposal for 

Tolerances of Residues in/on Barley and Wheat: Analytical Method and Residue 

Chemistry Review.

From: Y. Donovan

To: K. Boyle/R. Forrest

Date: 11/22/02 

MRIDs: 44302906-44302915

DP#s: 342071

Subject: Mefenpyr-diethyl (Safener HOE 107892). Petition for Establishment of 

Rotational Tolerances for Soybean and Canola. Summary of Analytical 

Chemistry and Residue Data.

From: D. Davis

To: Karen Angulo

Date: 6/3/08 

MRIDs: 47140601

DP#s: 358191

Subject: Mefenpyr-diethyl (Safener HOE 107892). Addendum to the Analytical 

Chemistry and Residue Data Summary to Support the Establishment of Rotational 

Tolerances for Soybean and Canola.

From: D. Davis

To: Karen Samek

Date: 11/25/08 

MRIDs: 45447701

DP#s: 286489

Subject: Safener HOE 107892 (mefenpyr-diethyl) Dietary Exposure Assessment for the 

Section 3 Registration Action from the use of HOE-107892 on Barley and Wheat.

From: Y. Donovan

To: K. Boyle/R. Forrest

Date: 11/22/02 

MRIDs: None
Mefenpyr diethyl Summary of Analytical Chemistry and Residue Data Barcode: D380768

Page 19 of 20

DP#s: 353114

Subject: Mefenpyr-diethyl (HOE 107892) Safener: Chronic Aggregate Dietary (Food and 

Drinking Water) Exposure and Risk Assessment for the Section 3 Registration 

Action to Add Soybean and Canola Rotational Crop Tolerances as a Result of 

Increased Application Rate.

From: D. Davis

To: Karen Angulo

Date: 6/3/08 

MRIDs: None

DP#s: 380767

Subject: Mefenpyr-diethyl (HOE 107892) Revised Safener Chronic Aggregate Dietary

(Food and Drinking Water) Exposure and Risk Assessment for the Section 3 

Registration Action to Add New Uses and Establish Tolerances on Sorghum and 

Grasses Grown for Seed.

From: A. LaMay

To: Bethany Benbow

Date: 2/22/11

MRIDs: None

Attachments: 

International Residue Limit Status sheet
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International Residue Limits 

Mefenpyr-diethyl (PC Code 811800; 10/06/10)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex3

40 CFR 180.509:

Plant/Livestock: mefenpyr-diethyl, 1-

(2,4-dichlorophenyl)-4,5-dihydro-5-

methyl-1H-pyrazole-3,5-dicarboxylic acid, 

diethyl ester and its 2,4-dichlorophenylpyrazoline metabolites.

None None

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

US Canada Mexico2 Codex

Grass, forage 1.6

Grass, hay 0.2

Sorghum, forage 0.4

Sorghum, grain 0.04

Sorghum, stover 0.2

Completed: M. Negussie; 10/06/2010

1

Includes only commodities of interest for this action. Tolerance values are 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.