UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

PC Codes: 128922 and 128923 

DP Barcode: D421435 

Date: August 5, 2013 

MEMORANDUM 

SUBJECT: Response to Public Comments on the Imazethapyr and lmazethapyr Ammonium 

FROM: 

Salt Registration Review Problem Formulation :.L" 

Edward Odenkirchen, Ph.D., Senior Scientist 2"'

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Stephen Wente, Ph.D., Biologist /~ - ~ P / >"j /7 

Environmental Risk Branch I 

Environmental Fate and Effects Division (7507P) 

Office of Pesticide Programs 

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Environmental Risk Branch I 

Environmental Fate and Effects Division (7507P) 

Office of Pesticide Programs 

TO: Katherine St. Clair, Chemical Review Manager 

Cathryn Britton, Team Leader 

Kevin Costello, Branch Chief 

Risk Management and Implementation Branch II 

Pesticide Re-Evaluation Division 

Office of Pesticide Programs (7508P) 

In response to the "Registration Review Problem Formulation for Imazethapyr and lmazethapyr 

Ammonium Salt" (D4 15245), BASF and the California Department of Pesticide Regulation 

(DPR) submitted comments (BASF) and monitoring data (California DPR) during the public 

comment period. The purpose of ~his memorandum is to address these comments and data 

submissions. 

Monitoring Data 

The Agency greatly appreciates receiving relevant monitoring data from the California 

Department of Pesticide Regulation. The data will be considered and used (as appropriate) in 

future risk assessments. 
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Comments by BASF 

Comment: Honey bee toxicity of residues on foliage study (OCSPP Guideline 850.3030) is a 

conditional study required only when the formulation contains one or more active ingredients 

having an acute LD50 of < 11 μg per bee as determined in the honey bee acute contact study (40 

CFR 158.630). The Environmental Fate and Effects Division (EFED) Preliminary Problem 

Formulation document states on page six (2002 ecological risk assessment for imazethapyr use 

on rice and clover) that, “Imazethapyr is practically non-toxic (LD50 >100 μg/bee) to honey bees; 

therefore low risk was assumed for beneficial terrestrial invertebrates.” Thus, BASF respectfully 

requests that the requirement for honey bee toxicity of residues study be waived. 

EPA Response: The requested study can be waived. 

Comment: Honey bee larval toxicity study (OECD 237) requested in the preliminary work plan 

is a new data requirement. BASF agrees to conduct this study, and would like to note that the 

TGAI is the test material most often used to support all outdoor end-use products. The TEP is 

used for testing only when there are specific concerns with the TEP formulation. 

EPA Response: The study should be conducted with TGAI. 

Comment: The Executive Summary on page four of the Environmental Fate and Effects 

Division (EFED) Preliminary Problem Formulation document states that the Tier 2 seedling 

emergence study (OCSPP guideline 850.4100) is listed as a data gap “place holder” pending 

completion of data evaluation for the submitted study (MRID 44996102). BASF requests the 

Data Evaluation Record (DER) for this study. 

EPA Response: The study is still undergoing review. When the DER is completed, BASF will 

receive notification and a copy. 

Comment: The Executive Summary on page four of the Environmental Fate and Effects 

Division (EFED) Preliminary Problem Formulation document states that the Tier 2 vegetative 

vigor study (OCSPP guideline 850.4150) is listed as a data gap “place holder” pending 

completion of data evaluation for the submitted study (MRID 44996101). BASF requests the 

Data Evaluation Record (DER) for this study. 

EPA Response: The study is still undergoing review. When the DER is completed, BASF will 

receive notification and a copy. 

Comment: BASF had previously submitted an aquatic plant growth study for degradate CL 

266858 with Lemna gibba (MRID 45161322). Page 28 of the Environmental Fate and Effects 

Division (EFED) Preliminary Problem Formulation document states that this study was 
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classified as invalid. BASF will review this study for deficiencies, and is aware that “In the 

absence of acceptable data, the compound may be considered of equal toxicity as the parent 

herbicide, or an extrapolation from available structural analogs’ toxicity relative to parent will be 

used to establish an endpoint.” 

EPA Response: No response necessary.