Fenoxaprop-p-ethyl Summary of Analytical Chemistry and Residue Data Barcode D415998, D416001

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND

 POLLUTION PREVENTION

MEMORANDUM

Date: 05-December-2013

Subject: Fenoxaprop-p-ethyl. Petition for the Establishment of a Permanent Tolerance and 

Registration for Use on Grass Grown for Seed (Grass Hay). Summary of Analytical 

Chemistry and Residue Data for Registration Review.

PC Code: 129092 DP Barcode: D415999, D416001

Decision No.: 466648, 477911 Registration No.: 264-666, 264-1073, 264-

653

Petition No.: 2E8051 Regulatory Action: Section 3 Registration, 

Registration Review

Risk Assessment Type: NA Case No.: NA

TXR No.: NA CAS No.: 71283-80-2

MRID No.: 48834301 40 CFR: 180.430

From: Donald Wilbur, Chemist

Risk Assessment Branch VI

Health Effects Division (7509P)

Through: Sheila Piper, Senior Chemist

Risk Assessment Branch VI

Health Effects Division (7509P)

To: Shalu Shelat, Risk Assessor

Risk Assessment Branch VI

Health Effects Division (7509P)

 Andrew Ertman/ Barbara Madden, Risk Managers

 Risk Integration Minor Use, and Emergency Response Branch

 Registration Division (7505C)

 Molly Clayton, Chemical Review Manager

 Risk Management and Implementation Branch III 

 Pesticide Re-evaluation Division (7508P)
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Table of Contents

1.0 Executive Summary............................................................................................................ 3

2.0 Regulatory Recommendations............................................................................................ 3

2.1 Data Deficiencies/Data Needs.......................................................................................... 4

2.2 Tolerance Considerations................................................................................................. 4

2.2.1 Enforcement Analytical Method............................................................................... 4

2.2.2 Established Tolerances.............................................................................................. 4

2.2.2.1 Revisions to Established Tolerances ................................................................. 5

2.2.3 Petitioned-For Tolerances......................................................................................... 5

2.2.3.1 Revisions to Petitioned-For Tolerances............................................................. 5

2.2.4 International Harmonization ..................................................................................... 6

3.0 Introduction......................................................................................................................... 6

3.1 Chemical Identity ............................................................................................................. 6

3.2 Physical/Chemical Characteristics................................................................................... 6

3.3 Pesticide Use Pattern/Directions for Use (860.1200)....................................................... 7

4.0 Metabolite/Degradate Residue Profile................................................................................ 9

4.1 Nature of the Residue....................................................................................................... 9

4.1.1 Summary of Plant Metabolism (860.1300)............................................................... 9

4.1.2 Summary of Livestock Metabolism (860.1300)....................................................... 9

4.1.3 Summary of Confined Rotational Crops (860.l850)............................................... 10

4.2 Comparison of Metabolic Pathways .............................................................................. 10

4.3 Residues of Concern Summary...................................................................................... 11

5.0 Residue Profile.................................................................................................................. 11

5.1 Residue Analytical Methods (860.1340)........................................................................ 11

5.1.1 Data Collection Method (Grass Hay) ..................................................................... 11

5.1.2 Tolerance Enforcement Method ............................................................................. 12

5.1.3 Multi-Residue Methods (860.1360)........................................................................ 12

5.1.4 Submittal of Analytical Reference Standards (860.1650) ...................................... 12

5.2 Storage Stability (860.1380) .......................................................................................... 12

5.3 Residue Data .................................................................................................................. 13

5.3.1 Crop Field Trials (860.1500) .................................................................................. 13

5.3.2 Field Rotational Crops (860.1900) ......................................................................... 13

5.3.3 Processed Food and Feed (860.1520)..................................................................... 14

5.3.4 Meat, Milk, Poultry and Eggs (860.1480) .............................................................. 14

5.3.5. Food Handling (860.1460)...................................................................................... 14

5.3.6 Water, Fish, and Irrigated Crops (860.1400).......................................................... 14

5.4 Food Residue Profile...................................................................................................... 14

6.0 Tolerance Derivation ........................................................................................................ 15

7.0 ChemSAC Reference ........................................................................................................ 15

Appendix A. International Residue Limits Table ........................................................................ 16

 
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1.0 Executive Summary

Fenoxaprop-p-ethyl [FPE; (+)-ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate] is 

a selective aryloxy phenoxy-propionate herbicide used to control grass weeds after emergence. 

FPE is currently registered for use on barley, cotton, rice, soybeans, and wheat. FPE is also

registered for non-agricultural use on conservation reserves, ornamentals, rights-of-way, and turf. 

The Interregional Research Project No. 4 (IR-4) has submitted a petition requesting a new 

tolerance be established on grass, hay to support a new use on grass grown for seed in the states 

of Oregon, Washington, and Utah only. Based on a ChemSAC’s recommendation (See Section 

7.0), data were only generated for grass hay. Additionally, this updated residue chemistry 

summary document is being drafted to support the registration review of FPE.

The requirements for residue analytical methods are fulfilled for the purposes of the proposed 

use as well as for registration review. Adequate methods are available for tolerance enforcement 

and data collection purposes for plant and animal commodities.

The nature of the residue is adequately understood based on submitted barley, soybean, rice, 

cotton, peanut, and wheat metabolism studies. An adequate number of magnitude of the residue 

(MOR) field trial studies were conducted, with appropriate geographic representation and 

application scenarios. All samples were analyzed using a validated analytical method and were 

supported by sufficient storage stability data. Processing studies showed that residues of FPE do 

not concentrate in any regulated processed commodities. 

The nature of the residue in livestock (poultry and ruminants) is adequately understood based on 

submitted goat and laying hen metabolism studies. Tolerances on ruminant livestock 

commodities have been established based on dietary burden calculations and the submitted 

ruminant feeding study. Based on the submitted poultry metabolism study, the Agency has 

concluded that there is no reasonable expectation of finite residues in poultry commodities [40 

CFR 180.6(a)(3)]; accordingly, no poultry tolerances are needed. 

It is important to note that FPE is an enriched isomer formulation (95% d and 5% l enantiomers) 

based on the previously registered product fenoxaprop ethyl (FE, PC Code 128701) which is a 

50:50 racemic mixture of d and l enantiomers. All current tolerances from the use of FPE are 

listed under FE in 40CFR. HED has concluded that FE and FPE have comparable toxicity 

profiles and the toxicological databases have been bridged. Therefore, even though the 

tolerances are in terms of FE, they are protective for all uses of FPE based on the comparable 

toxicity as well as the fact that the data-collection and tolerance enforcement methods are not 

stereo-specific and cannot differentiate between FE and FPE (i.e., cannot distinguish between the 

two isomers or the level of enrichment of the d enantiomer). For this reason, any discussion of 

tolerances with respect to FPE is described in terms of FE in this document.

2.0 Regulatory Recommendations

HED has examined the residue chemistry database for FPE. Pending submission of a revised 

Section F (see requirements under Revisions to Petitioned-For Tolerances below) there are no 

residue chemistry issues that would preclude the establishment of a tolerance with regional 

restriction on grass, hay. Additionally, all regulatory requirements related to residue chemistry 

for FPE are considered adequate for registration review.
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A human-health risk assessment is forthcoming.

2.1 Data Deficiencies/Data Needs

There are no residue chemistry data deficiencies identified for FPE. 

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

An adequate analytical method is available to enforce tolerances for FE in plant and animal 

commodities. A gas chromatography with electron capture detection (GD-ECD) method, based 

on Hoechst HRAV Analytical Method HRAV-4B, was previously reviewed by the Agency and

was incorporated into the Food and Drug Administration (FDA) Pesticide Analytical Manual, 

Volume II (PAM II). The method has a limit of quantitation (LOQ) of 0.05 ppm in all matrix 

types. 

The method is described as follows. Briefly, samples are refluxed with a solution of acetonitrile, 

concentrated HCl, and water for 6 hours and filtered through filer paper. An aliquot is

transferred onto an Extrelut column and equilibrated with the column matrix. The hydrolysis 

product 6-chlorobenzoxazolone is eluted with hexane:diethyl ether and evaporated to dryness. 

The residue is dissolved with ethyl acetate and the ethyl acetate evaporated to dryness. The 

residue is then derivatized in a mixture of toluene, acetic anhydride, and pyridine for 2 hours at 

130° C. The residue with reaction product acyl 6-chlorobenzoxazolone (AE F083312) is dried, 

and cleaned up on a silica gel SPE cartridge. FE and its metabolites are then determined as 

6-chlorobenzoxazolone (AE F083312) by GC-ECD. Total residue is then expressed as FE 

equivalents.

FE has also been subjected to analysis by the Food and Drug Administration (FDA) multiresidue method (MRM) protocols. Multi-residue methods are available for residues of FE and 

the metabolites of concern under Protocols 1 through 4.

2.2.2 Established Tolerances

Currently there are tolerances established for residues of FE as listed in Table 2.2.2 below. The 

tolerance expression for FE is as follows:

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

fenoxaprop-ethyl, (±)-ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate, and its 

metabolites, 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid and 6-chloro-2,3-

dihydrobenzoxazol-2-one, calculated as the stoichiometric equivalent of fenoxaprop-ethyl.

Table 2.2.2 Tolerance Summary for FE

Commodity Tolerance (ppm) Comments/Corrected 

Commodity Definition

180.430 (a) General

Barley, grain 0.05

Barley, straw 0.1

Cattle, fat 0.05

Cattle, meat byproducts 0.05
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Cattle, meat 0.05

Cotton, undelinted seed 0.05

Goat, fat 0.05

Goat, meat byproducts 0.05

Goat, meat 0.05

Hog, fat 0.05

Hog, meat byproducts 0.05

Hog, meat 0.05

Horse, fat 0.05

Horse, meat byproducts 0.05

Horse, meat 0.05

Milk 0.02

Peanut 0.05

Peanut, hulls 0.05 Revoke, no longer a regulated 

commodity

Rice, grain 0.05

Sheep, fat 0.05

Sheep, meat byproducts 0.05

Sheep, meat 0.05

Soybean 0.05 Soybean, seed

Wheat, grain 0.05

Wheat, straw 0.05

180.430 (b) Section 18 emergency exemptions

Grass, forage 0.05 Expires 12/31/2013

Grass, hay 0.05 Expires 12/31/2013

2.2.2.1 Revisions to Established Tolerances

HED is recommending that certain existing tolerances be amended to reflect current polices. 

The commodity definition for soybean should be changed from soybean to soybean, seed. 

Additionally, the tolerance on peanut, hulls may be revoked since that commodity is no longer a 

regulated raw agricultural commodity (RAC).

2.2.3 Petitioned-For Tolerances

For the purposes of this petition, tolerances for residues of FE in/on grass, hay were not derived 

using the Organization for Economic Cooperation and Development Maximum Residue Level 

(OECD MRL) Calculation Procedures since all of the residue values were less than the limit of 

quantification (<LOQ) of the analytical method. 

Table 2.2.3 Proposed Tolerance Summary for FE

Commodity Proposed 

Tolerance 

(ppm)

HED-Recommended 

Tolerance (ppm)

Comments 

180.430 (c) Tolerances with regional restrictions

Grass, hay 0.15 0.09 For the states of WA, OR, and 

UT only

2.2.3.1 Revisions to Petitioned-For Tolerances

HED is recommending that a tolerance with regional restriction be set for grass, hay as requested 

by the petitioner with the change noted below. 
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The method used for data-collection (as well as tolerance enforcement) converts the residues of 

concern for FE to acyl 6-chlorobenzoxazolone for detection. It is necessary to then convert this 

residue value to parent equivalents. Since the residues found on grass, hay were less than the 

LOQ of 0.05 ppm for acyl 6-chlorobenzoxazolone, HED multiplied this 0.05 ppm value by the 

ratio of the molecular weights (1.71) to arrive at a recommended tolerance of 0.09 ppm.

The requested change to the proposed tolerance level is shown in Table 2.2.3 above.

2.2.4 International Harmonization

There are no international harmonization issues related to the existing or proposed uses of FPE.

Please see Appendix A for a summary of international maximum residue limits (MRLs).

2.3 Label Recommendations

There are no label recommendations based on residue chemistry identified for this petition. 

3.0 Introduction

Fenoxaprop-p-ethyl [FPE; (+)-ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate] is 

a selective aryloxy phenoxy-propionate herbicide used to control grass weeds after emergence. 

FPE is currently registered for use on barley, cotton, rice, soybeans, and wheat. FPE is also

registered for non-agricultural use on conservation reserves, ornamentals, rights-of-way, and turf. 

The chemical structure and nomenclature of FPE are presented in Table 3.1, and the 

physicochemical properties of the technical grade of FPE are provided in Table 3.2.

3.1 Chemical Identity

Table 3.1. FPE Nomenclature

Fenoxaprop-p-ethyl

Common Name Fenoxaprop-p-ethyl

Company Experimental Name AE F046360

IUPAC Name ethyl (R)-2-[4-(6-chloro-1,3-benzoxazol-2-yloxy)phenoxy] propionate

or

ethyl (R)-2-[4-(6-chlorobenzoxazol-2-yloxy)phenoxy]propionate

CAS Name ethyl (2R)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate

CAS # 71283-80-2

3.2 Physical/Chemical Characteristics

FPE has low water solubility. Its octanol/water partition coefficient suggests that it is a 

hydrophobic compound that is more fat soluble than water soluble, exhibiting a tendency to 
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dissolve in fats, oils, lipids, and non-polar solvents more readily than in water. Further, FPE has 

a low vapor pressure. The full complement of physiochemical properties for this active 

ingredient is shown in Table 3.2.

Table 3.2. Physicochemical Properties of the Technical Grade FPE

Parameter Value Reference

Melting Point/Range (°C) 86.5 Health Canada 

Fenoxaprop-p-ethyl 

Proposed ReEvaluation Decision

(PRVD2011-04)

Density (g/cm3) 1.32

Water Solubility ( 20 °C, pH 5.8) (mg/L) 0.7

Solvent Solubility (g/L at 20°C) n-hexane 7.0

acetone >400

toluene >480

dichloromethane >400

methanol 43.1

isopropanol 14.2

ethyl acetate >380

Vapor Pressure (Pa) 5.3 x 10-

7 at 20°C

1.4 x 10-

6 at 25°C

1.1 x 10-4 at 50°C

Dissociation Constant (pKa) Not possible to measure 

in water in the pH range 

1-13 (no acidic or basic 

groups on the molecule)

Octanol/Water Partition Coefficient Log (Kow) 4.58

UV/Visible Absorption Spectrum Not expected to absorb at 

λ > 300nm

3.3 Pesticide Use Pattern/Directions for Use (860.1200)

The only FPE end-use formulation currently registered is as a liquid formulation which may be 

applied post-emergent for the use on various agricultural crops (barley, cotton, rice, soybeans, 

and wheat), ornamentals, turf (residential lawns and sod farms), and commercial sites 

(conservation reserve and right-of-way). There is also a proposed new use for grasses grown for 

seed in Oregon, Washington, and Utah.

A summary of the existing and proposed use patterns for FPE are shown in Table 3.3 below. 

Table 3.3. Summary of Directions for Use of Currently Registered FPE Uses

Applic. 

Timing, Type, 

and Equip.

Formulation 

[EPA Reg. 

No.]

Max 

Applic. 

Rate (lb 

ai/A)

Max. No. 

Applic. per 

Season

Max. 

Seasonal 

Applic. Rate 

(lb ai/A)

PHI 

(days)

Use Directions and 

Limitations

Barley

Groundboom 

and Aerial 

applications

264-666*

264-1073*

264-1075

0.083 1 0.083 57 No chemigation

24 hour REI

Conservation Reserve

Groundboom 264-647* 0.1 NS 0.142 N/A No chemigation
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Table 3.3. Summary of Directions for Use of Currently Registered FPE Uses

Applic. 

Timing, Type, 

and Equip.

Formulation 

[EPA Reg. 

No.]

Max 

Applic. 

Rate (lb 

ai/A)

Max. No. 

Applic. per 

Season

Max. 

Seasonal 

Applic. Rate 

(lb ai/A)

PHI 

(days)

Use Directions and 

Limitations

and Aerial 

applications

24 hour REI

Cotton

Groundboom 

and Aerial 

applications

100-1059* 0.105 1 0.105 90 No chemigation

24 hour REI

Ornamentals 

Groundboom 

and handheld 

applications

432-950* 0.173

0.002 lbs 

ai/gal

3 0.531 N/A No chemigation

24 hour REI

Ornamentals (Residential)

Handheld 

applications 72155-74 0.076 NS 0.531 N/A N/A

Rice

Groundboom 

and Aerial 

applications

264-647

264-682

0.108

(SLN) 1 0.142 65 No chemigation

24 hour REI

Right of Way

Groundboom 

and Aerial 

applications

100-1059

432-950*

0.173 

0.177 

(lbs 

ai/gal)

3 0.531 N/A No chemigation

24 hour REI

Soybean

Groundboom 

and Aerial 

applications

100-1059

264-647* 0.1 2 0.128 90 No chemigation

24 hour REI

Turf (sod/commercial)

Groundboom 

and Aerial 

applications

432-950* 0.173 NS 0.531 NS No chemigation

24 hour REI

Turf (residential lawns)

Ready to use 

Hose-end 

sprayer and 

concentrate 

solutions 

through 

handheld 

equipment

228-716*

72155-74

72155-77

72155-78

0.1 NS NS N/A No aerial, groundboom, or 

chemigation

Wheat

Groundboom 

and Aerial 

applications

100-1429

264-666*

264-1073*

264-1075

0.083 1 0.083 70 No chemigation

24 hour REI

Proposed Grass grown for seed (Oregon, Washington, Utah)

Groundboom 

application 264-266 0.082 NS NS 60 No chemigation no aerial applications
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4.0 Metabolite/Degradate Residue Profile

 

4.1 Nature of the Residue

4.1.1 Summary of Plant Metabolism (860.1300)

HED has previously concluded that the metabolism of fenoxaprop-ethyl is adequately 

understood. Plant metabolism studies have been submitted for barley (PP#3F4182, D.Davis, 

08/17/1993), soybeans (PP#3G2940, R. Loranger, 11/09/83), rice (PP#4G3035, R. Loranger, 

06/07/84), cotton, peanuts and wheat (PP#8F3599, M. Bradley, 05/20/88). It has been concluded 

that the metabolic pathway for fenoxaprop-ethyl is similar in these plants. The parent compound 

fenoxaprop-ethyl is cleaved to yield 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic 

acid which subsequently loses phenoxypropionic acid to yield 6-chloro-2,3--dihydrobenzoxazol2-one. The residue of concern in plants consists of fenoxaprop-ethyl, its free acid metabolite {2-

[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid,} and 6-chloro-2,3--

dihydrobenzoxazol-2-one.

Additionally, a comparison of the metabolism of FE and FPE was submitted for soybeans, rice, 

and wheat (MRID 47113302). The results showed that there is no significant difference in the 

metabolism for FE and FPE. No racemisation occurs for FPE and all metabolites stay in the d

configuration. The metabolism of FE and FPE follow the same path leading to the metabolic 

pathway being identical for the two compounds.

Conclusions. The nature of the residue for is considered to be adequately understood. Plant

metabolism data on barley, soybeans, rice, cotton, peanuts, and wheat were submitted/reviewed 

and found to be scientifically acceptable. Metabolism in these crops shared a common metabolic 

pathway. 

4.1.2 Summary of Livestock Metabolism (860.1300)

Ruminant

The metabolism of fenoxaprop-ethyl in animals has been previously considered in lactating 

ruminants (PP#6F3316, N. Dodd, 02/04/1986). It was reported that 6-chloro-2,3-

dihydrobenzoxazol-2-one constituted 75% of the residue in milk and 50% of the residue in the 

tissues of liver and kidney. No information was available concerning the relative amounts of 

parent and the two metabolites in ruminant tissues, since the analytical method used in the 

ruminant study was the enforcement method resulting in a common analyte, 6-chloro-2,3-

dihydrobenzoxazol-2-one. In HED reviews of 02/02/90 and 12/14/90, (PP#9F3714), it was 

concluded that the residue of concern in ruminants and swine are parent compound, its free acid, 

fenoxaprop, and 6-chloro-2,3-dihydrobenzoxazol-2-one.

Poultry

A poultry metabolism study (MRID #43426201, 01/22/1998) was submitted in response to 

deficiencies noted in the review of PP#3F4182 (D.Davis, 08/17/93). The submitted study 

resolved all outstanding deficiencies regarding poultry metabolism (S. Knizner, 01/22/98). The 

nature of the residue in poultry has been adequately delineated. The principal route of 

metabolism is de-esterification to the free acid, followed by cleavage of the ether linkage to yield 

6-chloro-2,3-dihydrobenzoxazol-2-one and phenoxypropionic acid. Further, based on the low 

levels of TRR found in edible tissues of poultry following dosing at highly exaggerated rates, 
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there is no reasonable expectation of finite residues (180.6(a)(3)). Therefore, a poultry feeding 

study is not required, nor are tolerances for poultry/eggs required.

Conclusions. The nature of the residue in livestock for FPE based on the currently registered and 

proposed uses is considered to be adequately understood. Both ruminant and poultry metabolism 

studies were submitted/reviewed and found to be scientifically acceptable. 

Based on the submitted poultry metabolism, the existing and proposed proposed uses can be 

classified as 40 CFR 180.6 (a)(3), no reasonable expectation of finite residues in poultry

livestock commodities. However, this decision may be reconsidered if the use pattern changes 

and/or additional poultry feedstuffs are proposed in the future. 

4.1.3 Summary of Confined Rotational Crops (860.l850)

A confined rotational crop study was submitted and reviewed in support of an experimental use 

permit (EUP) on soybeans (8340-EUP-T, 01/04/1984). Rotational crops were planted at 120 and 

364 days after the first application of radiolabeled FE. Wheat, lettuce, carrots, radishes, 

soybeans, and corn were then allowed to grow to maturity. Samples of these representative 

rotational crops did not show significant uptake of radiolabeled FE after 120 and 364 days. The 

parts of the plants that had measurable levels of radioactivity are not used for human 

consumption. Only total radioactive residue (TRR) was measured in the study.

Additionally, the European Food Safety Authority (EFSA) has published its conclusions 

regarding the peer review FPE (EFSA Scientific Report 2007-121, 11/29/2007). In this report, 

two separate confined rotational crop studies are discussed; one with FPE and one with FE. TRR 

in plants grown at 30 days, 120 days, and 365 days at labeled application rates (similar to rates in 

the US) were below the LOQ for all crops tested (leafy vegetables, root vegetables, and small 

grains). Based on that, EFSA concluded that field trials for rotational crops are not required.

Conclusions. Confined rotational crop data were submitted, reviewed and found to be 

scientifically acceptable. Based on the results of this study and the results of the studies from 

EFSA, no field accumulation studies are required.

4.2 Comparison of Metabolic Pathways

The metabolism of FPE in plants is similar. The parent compound is rapidly metabolized to 

yield 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid which subsequently loses 

phenoxypropionic acid to yield 6-chloro-2,3--dihydrobenzoxazol-2-one. Residues in plants tend 

to be surface residues with no translocation to newly formed leaves or plants parts. There is no 

difference between the metabolic profiles of FE and the enriched FPE.

Metabolism studies performed in rat, goat, and laying hen showed a common metabolic pathway 

in animals. FPE is metabolized in animals primarily by de-esterification to the free acid, 

followed by cleavage of the ether linkage to yield 6-chloro-2,3-dihydrobenzoxazol-2-one and 

phenoxypropionic acid. 
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4.3 Residues of Concern Summary

The residues of concern for FPE are summarized below in Table 4.3.

Table 4.3. Summary of Metabolites and Degradates Recommended for inclusion in the Risk

Assessment and Tolerance Expression

Matrix Residues Included In Risk Assessment Residues Included In 

Tolerance Expression

Plants fenoxaprop-ethyl,

2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid,

6-chloro-2,3 dihydrobenzoxazol-2-one

Same as those included in RA

Rotational crops NA NA

Livestock

(ruminants and 

poultry)

fenoxaprop-ethyl

2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid 

6-chloro-2,3 dihydrobenzoxazol-2-one

Same as those included in RA

Drinking Water fenoxaprop-ethyl and all degradates containing the 6-chloro2-benzoxazol moiety NA

NA – Not applicable. 

5.0 Residue Profile

5.1 Residue Analytical Methods (860.1340)

5.1.1 Data Collection Method (Grass Hay)

Samples of grass hay were analyzed for fenoxaprop-p-ethyl (AE F046360), fenoxaprop-p 

(AE F088406), and 6-chlorobenzoxazolone (AE F054014) using Cornell Analytical Laboratory 

Method “Residue Analysis of Fenoxaprop-P-Ethyl (AE F046360) and its Metabolites on Grasses 

by GC/Mass Spectrum Detection. Version #1”. This working method was derived from Hoechst 

HRAV Analytical Method HRAV-4B “Gas Chromatographic Determination of Fenoxapropethyl [Ethyl-2-(4-(6-Chloro-2-Benzoxazolyloxy) Phenoxy)Propanoate] and its Metabolites, 2-(4-

(6-Chloro-2-Benzoxazolyloxy) Phenoxy)Propanoic acid and 6-Chloro-2,3-Dihydrobenzoxazol2-one, as Residues in Wheat and Barley Grain, Straw, and Milled Products”. Modifications were 

made to improve the performance of the method.

Briefly, samples were refluxed with a solution of acetonitrile, concentrated HCl, and water for 

6 hours and filtered through filer paper. An aliquot was transferred onto an Extrelut column and 

equilibrated with the column matrix. The hydrolysis product 6-chlorobenzoxazolone was eluted 

with hexane:diethyl ether and evaporated to dryness. The residue was dissolved with ethyl 

acetate and the ethyl acetate evaporated to dryness. The residue was then derivatized in a 

mixture of toluene, acetic anhydride, and pyridine for 2 hours at 130° C. The residue with 

reaction product acyl 6-chlorobenzoxazolone (AE F083312) was dried, dissolved in toluene 

followed by hexane, and transferred onto a silica gel SPE cartridge. The acyl 6-

chlorobenzoxazolone was eluted with toluene, collected, dried, brought to volume with toluene, 

and analyzed by GC/MS. 

The LLMV in this study was 0.05 ppm for the three fenoxaprop-ethyl-derived analytes. Based 

on recoveries of samples fortified at the LLMV, the limit of detection (LOD) and limit of 

quantitation (LOQ) were calculated as 0.0066 ppm and 0.020 ppm, respectively, for fenoxapropp-ethyl; as 0.017 ppm and 0.052 ppm, respectively, for fenoxaprop-p; as 0.0031 ppm and 

0.0094 ppm, respectively, for 6-chlorobenzoxazolone.
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5.1.2 Tolerance Enforcement Method

An adequate analytical method is available to enforce tolerances for FE in plant and animal 

commodities. A gas chromatography with electron capture detection (GD-ECD) method, based 

on Hoechst HRAV Analytical Method HRAV-4B, was previously reviewed by the Agency and 

was incorporated into the Food and Drug Administration (FDA) Pesticide Analytical Manual, 

Volume II (PAM II). The method has a limit of quantitation (LOQ) of 0.05 ppm for residues of 

FE in all matrix types. 

The method is described as follows. Briefly, samples are refluxed with a solution of acetonitrile, 

concentrated HCl, and water for 6 hours and filtered through filer paper. An aliquot is

transferred onto an Extrelut column and equilibrated with the column matrix. The hydrolysis 

product 6-chlorobenzoxazolone is eluted with hexane:diethyl ether and evaporated to dryness. 

The residue is dissolved with ethyl acetate and the ethyl acetate evaporated to dryness. The 

residue is then derivatized in a mixture of toluene, acetic anhydride, and pyridine for 2 hours at 

130° C. The residue with reaction product acyl 6-chlorobenzoxazolone (AE F083312) is dried, 

and cleaned up on a silica gel SPE cartridge. FE and its metabolites are then determined as 

6-chlorobenzoxazolone (AE F083312) by GC-ECD. Total residue is then expressed as FE 

equivalents.

5.1.3 Multi-Residue Methods (860.1360)

FE has also been subjected to analysis by the Food and Drug Administration (FDA) multiresidue method (MRM) protocols. Multi-residue methods are available for residues of FE and 

the metabolites of concern under Protocols 1 through 4.

5.1.4 Submittal of Analytical Reference Standards (860.1650)

The analytical standard for FE, with an expiration date of 07/04/2018, is currently available in 

the EPA National Pesticide Standards Repository [personal communication from T. Cole of 

BEAD/ACB to D. Wilbur, 11/18/2013]. Reference standard supplies need to be 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 Theresa Cole at the following address:

USEPA

National Pesticide Standards Repository/Analytical Chemistry Branch/OPP

701 Mapes Road

Fort George G. Meade, MD 20755-5350

The full 9 digit zip code is mandatory or the mail will be returned.

5.2 Storage Stability (860.1380)

Storage stability data have been previously submitted for residues of fenoxaprop-ethyl on 

soybeans for intervals up to 2 years (PP#6F3316, N. Dodd, 02/04/86), in peanuts for intervals for 

up to 6 months (PP#8F3599, M. Bradley, 05/20/88), and in barley grain and straw for a period of 

1 year (MRID #42563002, D. Davis, 08/17/93). Crop field trial samples in the grass hay 

magnitude of the residue study were analyzed within one year and data from barley straw can be 

translated to grass hay. Therefore, no additional storage stability data are required to support a 
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permanent tolerance on grass hay.

5.3 Residue Data

5.3.1 Crop Field Trials (860.1500)

Existing Uses (Barley, Cotton, Peanut, Rice, Soybean, Wheat)

Field trial data have been previously submitted depicting residues of FPE in/on barley 

(PP#3F4182, D. Davis, 08/17/1993); rice and soybeans (PP#6F3316, N. Dodd, 02/04/1986); and 

cotton, peanuts and wheat (PP#8F3599, M. Bradley, 05/20/1988). All of these data are 

considered adequate for tolerance setting and support the existing tolerances and registrations.

Proposed Use (Grass Hay)

The Interregional Research Project No. 4 (IR-4) has submitted field trial data for fenoxaprop-pethyl (FPE) on grasses (grown for seed). Four field trials were conducted in the United States 

during the 2008 growing season the North American Free Trade Agreement (NAFTA) Growing 

Zones 11 (Washington- one trial) and 12 (Oregon – three trials). These data were submitted in 

support of a regional registration (Oregon, Washington, and Utah) for the use FPE on grasses 

grown for seed.

In each trial, Puma 0.75EC was applied in one broadcast application of approximately 0.0825 lb 

ai/A. Grass for hay was cut 56 to 62 days (8 to 9 weeks) after the application, and hay samples 

were collected 3 to 14 days after drying to a moisture content of approximately 10 to 20%. 

Based on ChemSAC’s review of a proposal submitted by IR-4 to EPA and their 

recommendations, magnitude of residue data were collected only for grass hay.

Sample analysis for residues of fenoxaprop-p-ethyl was conducted by Cornell Analytical 

Laboratories in Geneva, NY. FPE derived residues were determined using a laboratory working 

method based on Hoechst HRAV Analytical Method HRAV-4B “Gas Chromatographic 

Determination of Fenoxaprop-ethyl [Ethyl-2-(4-(6-Chloro-2-Benzoxazolyloxy) 

Phenoxy)Propanoate] and its Metabolites, 2-(4-(6-Chloro-2-Benzoxazolyloxy) 

Phenoxy)Propanoic acid and 6-Chloro-2,3-Dihydrobenzoxazol-2-one, as Residues in Wheat and 

Barley Grain, Straw, and Milled Products.”

Fenoxaprop-ethyl derived residues consist of three analytes: fenoxaprop-p-ethyl (AE F046360), 

fenoxaprop-p (AE F088406), and 6-chlorobenzoxazolone (AE F054014). The lowest level of 

method validation (LLMV) was 0.05 ppm for the fenoxaprop-ethyl derived analytes.

The maximum storage interval for field-treated samples in this study was 363 days. No 

supporting storage stability data were submitted with the petition, as data previously submitted 

on barley straw is adequate to cover the period of frozen storage.

The results from the trials show that no fenoxaprop-ethyl derived residues above the respective 

LLMVs were observed in dried hay collected 8 to 9 weeks after one application of Puma 0.75EC 

at approximately 0.0825 lb ai/A.

5.3.2 Field Rotational Crops (860.1900)

Based on the results and findings in the confined field rotational crop studies, no limited field 

rotational crop data are required.
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5.3.3 Processed Food and Feed (860.1520)

Processing data have been previously submitted depicting residues of FPE in/on soybeans 

(PP#6F3316, N. Dodd, 02/04/1986); barley (PP#1G3827, R. Cook, 04/03/1991); rice 

(PP#14G3035, R. Loranger, 06/07/1984); and cotton, peanuts and wheat (PP#8F3599, M. 

Bradley, 05/20/1988). All of these data are considered adequate and support the existing 

tolerances and registrations. The results of all of these processing studies indicate that residues 

of FPE do not concentrate in processed commodities.

5.3.4 Meat, Milk, Poultry and Eggs (860.1480)

The potential dietary exposure of ruminant livestock to FPE residues was previously calculated 

(PP#9G3714, S. Knizner, 11/03/10997) using conservative tolerance level residues. These highend values were then extrapolated using the submitted ruminant feeding study (PP#8F3599, M. 

Bradley, 05/20/1988) to set tolerances on meat and milk. It is important to note that no 

detectable residues were present on the commodities used to calculate this high-end dietary 

burden. HED is confident that this previously calculated dietary burden is protective for the 

existing uses of FPE as well as the proposed new use on grass hay. This is due to the fact that 

the method used was much more conservative that the current method of using a maximum 

reasonably balanced diet (MRBD). Additionally, residues on grass hay were all below the LOQ 

of the method, which adds further support for this conclusion.

HED has previously concluded (PP#3F4182, D. Davis, 01/22/1998) that based on the low levels 

of TRR found in edible tissues of poultry following dosing at highly exaggerated rates, there is 

no reasonable expectation of finite residues (180.6(a)(3)) in poultry commodities. Therefore, 

tolerances for poultry/eggs are not required. The new use on grass hay does not change this 

conclusion since it is not a poultry feed item.

5.3.5. Food Handling (860.1460)

There are no food handling establishment uses for FPE; therefore a discussion of this guideline is 

not required. 

5.3.6 Water, Fish, and Irrigated Crops (860.1400)

There are no FPE uses involving the direct application to water; therefore a discussion of this 

guideline is not required.

5.4 Food Residue Profile

The results from plant metabolism for FPE indicate that the residues of concern are fenoxapropethyl, its free acid metabolite {2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid,} 

and 6-chloro-2,3-- dihydrobenzoxazol-2-one. These data also show that FPE undergoes limited 

translocation with plants. Supplemental metabolism studies on FE and FPE demonstrated that 

there is no significant difference in metabolism and no racemisation occurs. The metabolism of 

FE and FPE follows the same path leading to the metabolic pathway being identical for the two 

compounds.

Adequate residue chemistry data are available for FPE. Field trials showed levels of FPE
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residues to be less than the LOQ (<0.05 ppm) for all crops with the exception of some animal 

feedstuffs (barley and wheat straw) where very few detects were seen slightly above the LOQ. 

The data were generated using a validated data collection method and are adequately supported 

by frozen storage stability data. Sufficient processing studies are available to elucidate the fate 

of FPE in processed commodities, with no concentration seen in any crop matrix. Tolerances 

have been set on ruminant livestock commodities based on the previously calculated high-end

dietary burden. HED believes that these tolerances are protective for all uses of FPE since the 

method used was much more conservative that the current method of using a maximum 

reasonably balanced diet (MRBD). HED has determined that the uses of FPE are classified as 

180.6 (a) (3), no reasonable expectation of finite residues with respect to residues in poultry

commodities. Metabolism in rotational crops was seen to be limited; with radioactive residues 

less than the LOQ found at 30-days, 120-days, or 365-days in leafy vegetables, root vegetables, 

and small grains.

6.0 Tolerance Derivation

Tolerances for residues of FE in/on grass, hay were not derived using the Organization for 

Economic Cooperation and Development Maximum Residue Level (OECD MRL) Calculation 

Procedures since all of the residue values were less than the limit of quantification (<LOQ). 

However, the method used for data-collection (as well as tolerance enforcement) converts the 

residues of concern for FE, namely parent fenoxaprop-ethyl, (±)-ethyl 2-[4-[(6-chloro-2-

benzoxazolyl)oxy]phenoxy]propanoate, 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic 

acid and 6-chloro-2,3-dihydrobenzoxazol-2-one to acyl 6-chlorobenzoxazolone for detection. It 

is necessary to then convert this residue value to parent equivalents using molecular weight 

ratios. Since the residues found on grass, hay were <LOQ of 0.05 ppm for acyl 

6-chlorobenzoxazolone, HED multiplied this LOQ value by the ratio of the molecular weights

(1.71) to arrive at a recommended tolerance of 0.09 ppm.

7.0 ChemSAC Reference

The FPE registration for grass, hay was discussed by the Chemistry Science Advisory Council 

(ChemSAC) on 02/13/2008. The ChemSAC determined that there was not sufficient information 

available to support translation of wheat straw data to grass hay. Instead, the Council agreed that 

IR-4 should conduct the four trials (in OR and WA), ensuring that the hay samples are analyzed 

for all residues of concern. The ChemSAC concurred with IR-4 that it would not be appropriate 

to try to analyze grass forage samples in this case since the forage stage of grass would be long 

past by following the 60-day PHI restriction.
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Appendix A. International Residue Limits Table

Fenoxaprop-p-ethyl (129092), Fenoxaprop-ethyl (128701; 09/09/2013)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico1 Codex

40 CFR 180.430:

Plant and Livestock: Compliance with the 

tolerance levels specified is to be 

determined by measuring only the sum of 

fenoxaprop-ethyl, (±)-ethyl 2-[4-[(6-

chloro-2-

benzoxazolyl)oxy]phenoxy]propanoate, 

and its metabolites, 2-[4-[(6-chloro-2-

benzoxazolyl)oxy]phenoxy]propanoic acid 

and 6-chloro-2,3-dihydrobenzoxazol-2-

one, calculated as the stoichiometric 

equivalent of fenoxaprop-ethyl

(RS)-ethyl-2-[4-(6-

chloro-1,3-benzoxazol-2-

yloxy)

phenoxy]propanoate, 

including the metabolites 

2-[4-

[(6-chloro-2-

benzoxazolyl)-

oxy]phenoxy]propionic

acid and 6-chloro-2,3-

dihydrobenzoxalazol-2-

one

None

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

US Canada Mexico1 Codex

Barley, grain 0.05 0.05

Barley, straw 0.1

Cattle, fat 0.05

Cattle, meat byproducts 0.05

Cattle, meat 0.05

Cotton, undelinted seed 0.05

Goat, fat 0.05

Goat, meat byproducts 0.05

Goat, meat 0.05

Hog, fat 0.05

Hog, meat byproducts 0.05

Hog, meat 0.05

Horse, fat 0.05

Horse, meat byproducts 0.05

Horse, meat 0.05

Milk 0.02 0.02

Peanut 0.05

Peanut, hulls 0.05

Rice, grain 0.05 0.05

Sheep, fat 0.05

Sheep, meat byproducts 0.05

Sheep, meet 0.05

Soybean 0.05 0.05 dry soybeans

Wheat, grain 0.05 0.05

Wheat, straw 0.50

Proposed Tolerances

Grass, hay** 0.15

Completed: M. Negussie; 9/11/13

1 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.
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** Grass hay is a new use. Grass, hay also has a time-limited tolerance of 0.05 ppm expiring 12/31/2013.

*** Time limited tolerance expiring 12/31/2013.

(b) Section 18 emergency exemptions. Time-limited tolerances are established for residues of the 

herbicide fenoxaprop-ethyl, including its metabolites and degradates, in or on the commodities in the 

table in this paragraph in connection with use of fenoxaprop-ethyl under section 18 emergency

exemptions granted by EPA. Compliance with the tolerance levels specified in this paragraph is to be 

determined by measuring only the sum of fenoxaprop-ethyl, (±)-ethyl 2-[4-[(6-chloro-2-

benzoxazolyl)oxy]phenoxy]propanoate, and its metabolites, 2-[4-[(6-chloro-2-

benzoxazolyl)oxy]phenoxy]propanoic acid and 6-chloro-2,3-dihydrobenzoxazol-2-one, calculated as the 

stoichiometric equivalent of fenoxaprop-ethyl, in or on the commodity. The tolerances expire and are 

revoked on the dates specified in the table in this paragraph.

Commodity Parts per million

Expiration/

revocation date

Grass, forage 0.05 12/31/13

Grass, hay 0.05 12/31/13