UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

Date: October 22, 2013 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: Quizalofop Ethyl and Quizalofop-P-Ethyl, Response to Comments on the Human 

Health Risk Assessment for Registration Review. 

PC Codes: 128709, 128711 

Decision No.: 482484 

Petition No.: NA 

Risk Assessment Type: NA 

TXRNo.: NA 

MRIDNo.:NA 

DP Barcode: 0414555 

Registration No.: NA 

Regulatory Action: Registration Review 

Case No.: NA 

CAS Nos.: 76578-14-8, 100646-51-3 

40 CFR: § 180.441 

FROM: Danette Drew, Chemist/Risk Asses......._-

Ideliz Negron-Encarnacion, Ph.D., Chemist 

Risk Assessment Branch V /VII 

Health Effects Division (7509P) 

Office of Pesticide Programs 

THROUGH: Michael Metzger, Branch Chie{ } J J), 

Risk Assessment Branch V Nit'{ M · 

Health Effects Division (7509P) 

Office of Pesticide Programs 

TO: Khue Nguyen, Chemical Review Manager 

Risk Management and Implementation Branch 1 

Pesticide Re-Evaluation Division (7508P) 

E.l. du Pont de Nemours & Company (DuPont Crop Protection) has submitted comments on the 

Health Effect's Division (HED) document titled Quizalofop Ethyl and Quizalofop-P-Ethyl, 

Summary of Human Health Risk Assessment.for Registration Review ( 12/12/12; D394192). 

Those comments pertain to the residue chemistry data requirements as found on p.9 of D394192. 

In the present memo, each chemistry deficiency is briefly summarized, followed by DuPont's 

comments (from their submission dated 5/20/13, DuPont Crop Protection Comments to Federal 

Register/Vol. 78, No.54/Wednesday, March 20, 2013, Pages 17201-17204; Quizalofop 

Registration Review, Case No. 7215, Pesticide Docket Identification No. EPA-HQ-OPP-2007-

1 089; No MRID No.) and the current HED response. 

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Residue Chemistry Deficiency 

1) Directions for Use (860.1200): The Section 3 label of Assure II (EPA Reg. No. 352-541) 

indicates that grazing of livestock is prohibited in treated areas. This restriction is not considered 

practical. Based on the most recent version of the label (dated 04/12/20 12), this restriction has 

not yet been removed. 

DuPont: DuPont would like to discuss the possibility for a modified version of the grazing 

statement i.e. "Do not graze livestock in areas treated with Assure II for xx days after treatment." 

DuPont agrees to modify the second statement to "Do not feed forage, hay, or straw from treated 

areas to livestock." 

HED: For most crops, livestock grazing and feeding restrictions or prohibitions on labels are not 

considered practical as the treated commodities may not always be under grower control (Table 1 

Feedstuffs (June 2008)). For the same reason, a livestock restriction with a pre-grazing or preharvest interval may also be considered impractical. The restriction should be removed from the 

Assure II label. If desired, a feeding or grazing restriction may be imposed only for soybean 

forage, silage, or hay (those treated commodities considered being primarily under grower 

control). Note that the removal of the livestock restrictions from the labels will not have an 

impact the current estimated livestock dietary burden or on the current tolerances of quizalofop 

on livestock commodities (meat, milk, eggs). 

2) Multi-residue Methods (MRM) (860.1360): Multi-residue method data (recovery data) for 

the metabolites, quizalofop acid and quizalofop-methyl remain outstanding. 

DuPont: Further evaluation of the existing multi-method data submitted previously for 

quizalofop ethyl; PAM, Vol. 1, Appendix II (FDA PESTDATA database dated 10/99) is 

required. 

HED: Upon submission, HED will review any additional MRM data to determine if the 

requirement for MRM recovery data on the metabolites (quizalofop acid and quizalofop-methyl) 

has been fulfilled. 

3) Storage Stability (860.1380): Storage stability data for quizalofop-P-ethyl and quizalofop 

acid inion field corn and processed commodities have not been received. The available wheat 

storage stability data were tentatively considered adequate to support submitted crop field trial 

on corn. However, when the storage stability study on corn is submitted, the adequacy of the 

storage stability data will be re-evaluated. 

DuPont: Storage stability data for field corn were submitted in March 2013 and the report was 

assigned MRID 49090601. 

HED: A storage stability study has been submitted for quizalofop-P-ethyl and its acid form, 

quizalofop-P, in corn commodities (MRID 49090601; Dow AgroSciences LLC). That study has 

been reviewed by HED (I. Negron-Encarnacion, 711 I/ 13, D410951) with the following 

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conclusion: HED tentatively concurred that residues of quizalofop-P-ethyl can be quantitatively 

monitored in stored samples by measuring residues of both quizalofop-P-ethyl and its acid form 

quizalofop-P. Based on this, HED determined that the tolerances proposed for residues of 

quizalofop ethyl on field corn are still adequate. However, the storage stability study (MRID 

49090601) was tentatively classified as scientifically acceptable pending adequate resolution of 

the following issues: ( 1) the study did not include a description of how samples were prepared 

prior to frozen storage (e.g., stored whole, coarsely chopped, or homogenized); (2) the limits of 

quantitation for the method were not reported; (3) no data were provided for apparent residues in 

unfortified samples; (4) individual results for quizalofop-P in samples fortified with quizalofopP-ethyl were not reported; and (5) no raw data, such as dates of analysis, dilution factors, peak 

heights/areas, or method correction factors, were included with the study. DuPont recently 

submitted a revised storage stability report (MRID 49194801) addressing the above issues. HED 

has reviewed the revised report and the deficiencies previously noted were addressed (1. NegronEncarnacion; 10/21113; D414248). The previous study can be upgraded to scientifically 

acceptable. 

4) Processed Food and Feed (860.1520): Studies to determine the residues inion cotton, meal; 

cotton, hulls; cotton gin byproducts; and cotton, refined oil are required to determine if separate 

tolerances are needed for these food/feed items. 

DuPont: The current pre-harvest interval restriction for cotton is 80 days and DuPont believes 

that this supports the need for current tolerance on undelinted seed cotton. 

HED: EPA has recently received a data waiver request (no MRID) from DuPont Crop 

Protection, for the residue studies on cotton gin byproducts. HED has evaluated that waiver 

request and also reexamined the need for the processing studies on the other cotton processed 

commodities (cotton, meal; cotton, hulls; and cotton, refined oil). That review may be found in 

Quizalofop-P-Ethyt. Response to the Waiver Request from DuPont on the Cotton Processing 

Studies (I. Negron-Encarnacion, 09/25113, D412960) with the following conclusions: Potential 

residues in cotton gin byproducts will not have an effect on the livestock dietary burden, 

livestock commodity tolerances, or the dietary risk assessment. HED recommends waiving the 

cotton gin byproducts magnitude of residue studies and recommends the establishment of a 

tolerance of 3 ppm for residues of quizalofop ethyl in cotton gin byproducts based on translation 

of pea vine residue data. Processing studies for the other cotton commodities (cotton, meal; 

cotton, hulls; and cotton, refined oil) are not needed and tolerances need not be established for 

residues of quizalofop ethyl in those cotton processed commodities. 

5) Submittal of Analytical Reference Standards (860.1650): A reference standard of 2-

methoxy-6-chloroquinozaline should be sent to the analytical standard repository. 

DuPont: Will confirm any issues to synthesize this metabolite reference standard and estimated 

timeline to ship to the USEPA repository. 

HED: HED acknowledges DuPont's intent to prepare and ship the 2-methoxy-6-

chloroquinozaline standard to the repository and to inform EPA of the estimated timeline. 

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Standards may be sent to the attention of either Theresa Cole or Thuy Nguyen at the following 

address: 

US EPA 

National Pesticide Standards Repository/ Ana lytical Chemistry Branch/OPP 

701 Mapes Road 

Fort George G. Meade, MD 20755-5350 

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