1 Halosulfuron

- methyl Focus Meeting Summary September 1 9 , 2012 3:00

– 4:30 pm

A ttendees

Gowan Company ( Agent for Canyon Group) : Nina Wilson

Exponent: Mark J. Schocken, Ph.D.

Environmental Protection Agency (EPA or Agency) : Avivah Jakob (PRD), Tracy Per ry (PRD), Kaitlin Keller (PRD)

, Allen Vaughan (EFED), Michael Barrett (EFED)

Objective

The purpose of the meeting was for members of the EPA ’s Pesticide Re

- evaluation Division (PRD) and Environmental F ate and Effects Division (EFED) to meet with Canyon G roup , a technical registrant for halosulfuron

- methyl

, for the following reasons: 1) discuss us age information needed for the reg istration review ecological risk assessment s , and 2) discuss anticipated ecotoxicity and environmental fate data requirements an d information that could be submitted to fulfill these data gaps.

Presentation

Canyon ’s presentation covered:

• overview of halosulfuron

- methyl’s registered use patter n s ;

• the history of the chemical and Canyon Group; and

• ecotoxicity and environmental f ate information

o aerobic soil metabolism

o hydrolysis

o freshwater fish and invertebrate toxicity studies

Discussion

Use/Usage Information Canyon provided usage information in terms of amounts used in pounds per year by crop, noting that halosulfuron

- methyl is a small usage product primarily used as a spot treatment. EPA requested that Canyon send the information to EPA, as it was not included in the presentation. EPA also requested usage information in terms of percent treated of total crop production.

E

nvironmental Fate Information Canyon presented a detailed overview of the available aerobic soil metabolism information for halosulfuron

- methyl. A study conducted for European Union (EU) registration s was discussed and was provided to EPA informally in Ju ne 2012. Canyon will formally submit this study for EPA review prior to the anticipated Data Call

- In (DCI) issuance in June 2013. EFED indicated2 that cursory review of the aerobic soil metabolism studies supports Canyon’s contention that this study might add to the understanding of the variability in halosulfuron

- methyl degradation in different soils.

EPA is also requiring a Non

- Guideline (GLN) enhanced aerobic soil metabolism study because of discrepancies between available field and laboratory study results regarding halosulfuron

methyl ’s persistence in different soils. The study should include information (or limited data) on the decline of halosulfuron

- methyl in at least 10 soils. F ull aerobic soil metabolism studies (i.e., with characterization of the formation and d ecline of major degradates) are required for t he two soils where halosulfuron

- methyl is most persistent

. However, if the aerobic soil metabolism data , which Canyon will be formally submitting for review by the Agency, are found to be

a cceptable and fulfill GLN 835.4100, this portion of the (non

- GLN) enhanced aerobic soil metabolism study will not likely be required. Canyon presented their analysis of all available halosulfuron

- methyl field dissipation studies and agreed that difference s in the degrad ation rate do not appear to correlate to a single factor, such as pH or organic matter

. Canyon has committed to conducting the enhanced aerobic soil metabolism 10

- soil degradation study and will submit a protocol for Agency review prior to DCI issuance. T he requirement s for G LN 835.4100, aerobic soil metabolism and a non

- guideline enhanced aerobic soil metabolism study will remain until the data have been formally submitted and E PA has completed a full evaluation of the data.

Canyon also p resented information from a recent open literature publication on the hydrolysis of halosulfuron

- methyl

, as well as EU freshwater fish and invertebrate data

, and will formally submit these studies for Agency review. However, the enhanced hydrolysis study and freshwater fish and invertebrate studies remain as data gaps for Canyon until data have been formally submitted and reviewed for acceptability

.

Follow

- up

• Canyon will submit additional usage information measured in terms of percent of total crop treat ed to help refine future risk assessments.

• EPA and Canyon will continue working together to review available data prior to the DCI issuance.

• Canyon will work with the Agency, prior to DCI issuance, to develop and submit a study protocol for the non

- GLN , enhanced aerobic soil metabolism study.