UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

PC Code: 119011 

DP Barcode: 412964 

MEMORANDUM 

DATE: 

SUBJECT: 

TO: 

FROM: 

THROUGH: 

August 1, 2013 

EPA Response to Waiver Request for Non-Target Plant Reproduction Toxicity 

Testing Related to the Preliminary Problem Formulation for Ecological Risk and 

Environmental Fate, Endangered Species, and Drinking Water Assessments for 

Flazasulfuron. 

Khue Nguyen, Chemical Review Manager 

Neil Anderson, Chief RMIB 1, RMS 1 

Pesticide Re-Evaluation Division 

7508P 

Stephen Carey, Biologist ~~ !/ /3 

Environmental Risk Brancr:'~U ( f 1-...; 

Environmental Fates and Effects Division 

7507P 

Mark Corbin, Branch Chief . /j I n I\ n 

Environmental Risk Branch 6 :-tU.J(_ U 

Environmental Fates and Effects Division 

7507P 

In response to the posting in the public docket of the "Registration Review - Preliminary 

Problem Formulation for Ecological Risk and Environmental Fate, Endangered Species, and 

Drinking Water Assessments for Flazasulfuron (Document ID EPA-HQ-OPP-2011-0994 in 

www.regulation.gov), the· registrant ISK Biosciences Corporation (ISKBC) provided a waiver 

request during the public comments period related to the data requests for a non-target plant 

reproduction study for flazasulfuron. The purpose of this memorandum is to address the waiver 

request for a non-target plant reproduction toxicity test. 

ISKBC is citing DuPont's studies (MRIDs 48776901-48776905) in lieu of generating data 

regarding the potential effect of flazasulfuron on plant reproduction. EFED concurs that these 

data, in addition to a review of available open literature, as summarized in the memo from EFED 
to Michael Goodis, PRD, "Review of Sulfonyl Urea (SU) Plant Reproduction Studies" (Riley et 

al. 2012), are sufficient to fulfill the data requirement. 

EFED agrees with ISKBC that a non-target plant reproduction study can be waived from the data 

requirements for flazasulfuron. EFED's Plant Technical Team (PTT) determined that additional 

data on the effects to plant reproduction are not necessary for the registration review risk 

assessment for flazasulfuron. After analyzing available SU plant reproduction data from the open 

literature and the registrant-submitted study for chlorosulfuron, PTT's analysis determined that 

data from the vegetative vigor studies (OCSPP Guideline No. 850.4150) are sufficiently 

protective of potential impacts to plant reproduction from exposure during reproductive stages. 

The analysis indicated that plants exposed to SU herbicides during the reproductive life stage are 

likely to exhibit adverse effects on reproduction at concentrations similar to those effects on 

growth and survival seen in the vegetative vigor studies, so additional data on effects to plant 

reproduction are not required for the registration review risk assessment for flazasulfuron. Thus, 

when significant reductions of growth and/or survival effects are observed in the vegetative vigor 

studies, it can be assumed that reproduction effects on seed number or seed weight would be 

affected as well at similar concentrations. 

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