2 THIFENSULFURON METHYL AM ENDED FINAL WORK PLAN

Introduction:

This is the Environmental Protection Agency’s (EPA or the Agency) Amended Final Work Plan for the registration review of thifensulfuron met hyl. This document amends the September
2011 Thifensulfuron methyl Final Work Plan (FWP) to remove data requirements previously included in the summary of data gaps. Unless ot herwise stated in this amendment, all other elements of the Agency’s 2011 Thifensulfuron methyl FWP remain unchanged.

Changes to Ecological Data Needs:

The Registration Review - Preliminary Problem Fo rmulation for the Ecol ogical Risk Assessment of Thifensulfuron methyl was completed on March 10, 2011. The data needs liste d in the problem formulation were amended by the memorandum EFED update on Data Needs for Thifensulfuron (PC code 128845) Associated wi th the Registration Review DCI Issuance , dated December 8, 2011.

Given the structural similarity of thiefens ulfuron methyl degradates IN-L9225, IN-L9226, and IN-JZ789 to parent thifensulfuron methyl, the Agen cy will consider these degradates to be of equal toxicity to the parent compound. In additio n, structural analysis su ggests that degradates IN-V7160, IN-L9223, and IN-A4098 will not likely retain phytotoxic prope rties. Therefore, the Agency has determined that studies for the th ifensulfuron methyl degr adates are no longer
needed.

The Agency has completed its review of th e study and supplemental information (MRIDs 48043101 and 48043102) submitted to fulfill GDLN 835.4300 Aerobic Aquatic Metabolism. While this study is classified as supplementa l and does not entirely fulfill the guideline requirements, the Agency believes that the ex isting fate data are sufficient to conduct a comprehensive ecological risk assessment. Theref ore, no additional data are needed to satisfy this requirement for thifensulfuron methyl.

For GDLN 850.2100, Avian Acute Oral Toxicity Test (passerine species), the Agency has determined that the low application rate of thif ensulfuron methyl and low toxicity to other avian species tested indicate that risk to passerine species is unlikely to exceed levels of concern and, therefore, the study is no longer needed.

To summarize, the Agency has removed the following ecological data requirements from the list of data needs for thifensulfuron methyl specified in the Final Work Plan:

o GDLN 850.2100 Avian Acute Oral Toxicity Test (parent, passerine species)

o GDLN 850.4100 Seedling Emergence Test, Ti er II (degrada tes IN-A4098, INJZ789, IN-L9223, IN-L9225, IN-L9226, and IN-V7160)

o GDLN 850.4150 Vegetative Vigor Test, Tier II (degradate IN-L9223)

o GDLN 835.4300 Aerobic Aquatic Metabolism3 o GDLN 850.4400 Plant Toxicity Test with Lemna spp, Tier II (degradates INA4098, IN-JZ789, IN-L9223, IN-L9225, IN-L9226, and IN-V7160)

All other environmental fate and ecological effects data requireme nts remain as listed in the September 29, 2011 FWP.

Summary of Data Gaps – Thifensulfuron methyl

The table below summarizes the data needs for thifensulfuron methyl in the Registration Review Preliminary Problem Formulation for the Ecological Risk Assessment of Thifensulfuron methyl

, March 10, 2011, the EFED update on Data Needs for Thifensulfuron (PC code 128845) Associated with the Regist ration Review DCI Issuance , dated December 8, 2011, and the Thifensulfuron methyl. Human Health Assessme nt Scoping Document in Support of Registration
Review , dated March 15, 2011.

Guideline
Number Data RequirementTestMaterialEstimatedTimeframe

835.6100 Terrestrial Field Dissipation 1 TGAI 12

835.6200 Aquatic Field Dissipation 2 TGAI 12

NonGuideline Special Study for Non-Target Plant Reproductive Toxicity TEP 24

870.3200 21/28 Day Dermal Toxicity Study TGAI 12 870.3465 90-day Inhalation Toxicity Study 3 TGAI 24 870.6200 Neurotoxicity Battery (Acute and Subchronic Studies) TGAI 24 870.7800 Immunotoxicity Study TGAI 12

1 Only Environmental Chemistry Method for Resi dues in Soil and (associated ILV) are needed.

2 Only Environmental Chemistry Method for Resi dues in Water and (associated ILV) are needed.

3 Based on expected duration of exposure, the DCI is expected to provide that registrants may conduct a 28-day inhalation toxicity study in lieu of a 90-day study.