Page 2 of 3 environmental fate and effects, this document addresses only those comments pertinent to human health aspects of the preliminary work plan (PWP) for flufenacet

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CONCLUSIONS/RECOMMENDATIONS

The A gency thanks Bayer CropScience for their comments regarding flufenacet

. HED and BCS are in full agreement regarding the outstanding data requirements for Human Health Risk Assessment

. The Agency will consider all of BCS’ comments during the development o f the final work plan for flufenacet registration review

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DETAILED CONSIDERATI ONS

Bayer CropScience to the Office of Pesticide Programs (OPP) Regu latory Public Docket (7502P). Registration Review docket for Flufenacet Docket Opened for Review and Comment. Docket Number: EPA

- HQ

- OPP

- 2010

- 0 863

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Bayer CropScience’s comment: As a part of this order, the EPA has recommended a separate group of rat pups be treated by gavage with the low dose that was tested in the DNT study (1.7 mg/kg/day) to determin e whether thyroid endpoint s are affected at this dose. The absence of an effect in these assays at 1.7 mg/kg/day would support this dose as a NOAEL (instead of a LOAEL) for the DNT study and for young animals generally.

The revised human health risk assessments for flufenacet should take into account the collective results from these assays, since the Agency’s judgment that the low dose of t he DNT was LOAEL is the basis f or the acute and chronic reference dose.

HED’s Response : HED agrees that, if de signed and executed properly, the CTA may be used to confirm or refute offspring body weight effects (approximately 15% decrease in all dose groups) upon which the DNT LOAEL (1.7 mg/kg/day) is based

. The Agency will consider the results from the CTA , DNT and entire toxicology database collectively to make a weight

- of

- evidence determination of toxicological effects

. Bayer CropScience’s comment : The study (860.1500) is complete and has been submitted to the Agency for review (MRIDs 47930801 and 48456001). Define SC is a “suspension concentrate” formulation of flufenacet (i.e., not a soluble concentrate or emulsifiable concentrate) and Define DF is a “dry flowable” formulation of this active. The SC was developed to enable users to pump the formulation in a closed system as opposed to pouring the dry flowable. Results from a “side by side” comparison study indicate that the residues in/on corn matrices resulting from the use of Define SC were similar to or lower than the residues observed in/on the same co rn matrices resulting from the use of Define DF. Collectively, the data demonstrate that the corn tolerances as published in 40 CFR 180.527 are adequate to support the use of either formulation on field or sweet corn at postemergence application timings t hrough growth stage V5 at labeled application rates.

HED’s Response : Bay er CropScience has submitted a third bridging stu d y to support p ostemergence a pplication u ses of the soluble concentrate (SC) formulation to the Agency for review . The study has been screened and, while the rationale for conductingPage 3 of 3 the bridging study in Kansas rather that Iowa was not provided, the data are considered adequate and support the results from the two earlier bridging studies

, pending f inal review

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