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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460

July 17, 2013



### MEMORANDUM OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION



### Subject: EFED Response to Public Comments Submitted in Response to the Bromoxynil Registration Review Problem Formulation PWP

To: Margaret Hathaway, Chemical Review Manager Kevin Costello, Branch Chief



### From: Risk Management and Implementation Branch II Pesticide Re-evaluation Division (PRD) (7508P)

N.E. Federoff, Wildlife Biologist Elyssa Gelmann, Biologist Environmental Risk Branch II Environmental Fate and Effects Division (7507P)



### Through: Brian Anderson, Branch 

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This memorandum contains the Environmental Fate and Effects Division's (EFED) responses to
comments submitted to the Agency regarding the preliminary work plan and supporting documents for the registration review ofbromoxynil and bromoxynil esters (Docket ID No.: EPA-HQ-OPP-2012-0896). Comments relevant to the environmental fate and/or ecological effects of bromoxynil and its esters were submitted by the technical registrants (Bayer CropScience, Nufarm

, Albaugh and Agan Chern Mfg). The comments submitted by FESTF and Washington State Pest Management Resource Services will be addressed by the Pesticide Reevaluation Division. The comments from the registrants are summarized below and followed by

a response from EFED. ·


### Drinking Water Assessments The Agency does not mention the previously required targeted drinking water from surface water study, which was conducted in 1998-2000. In this study, drinking water concentrations were an order of magnitude lower than those predicted by Agency modeling (maximum concentrations of 0.38 and 0.041 ppb in raw and finished drinking water, respectively, and a maximum annual TWA concentration of 0.011 ppb ). These data should be used if additional refinements are needed in the dietary assessment.



### EFED Response: EFED will consider the submitted surface water monitoring data when conducting the drinking water assessment.
12 Bridging Strategy The registrants believe that a bridging strategy is appropriate and is supported by existing data. In respon se to the upcoming data call

- in the registrants will submit existing studies or conduct new studies to provide the requested information.

EFED Respons e: EFED will review the data when they are submitted.

Environmental Fate Data Submissions and Need s: Bromoxynil Aqueous Photolysis : A new aqueous photolysis study is in progress for bromoxynil octanoate and a decision will be made whether to conduct a s imilar study fo r bromoxynil phenol or consider the bromoxynil stable to hydrolysis after the bromoxynil octanoate study is complete. The bromoxyn il octanoate study cannot be used to determine the degradation rate of the bromoxynil phenol metabolite because the first step is debromination rather than the formation

o f bromoxynil phenol. The registrants were appreciative of the advice of the Agency that conducting this study could be very helpful in endangered specie s assessments and will consider this advice in making their decision.

Aerobic Soil Metabolism Studies : The registrants propose providing this inf o rmation through k inetic analysis of aerobic soil metabolism studies conducted with bromoxynil octanoate. Th e

r e gi strants noted that they will submit these analyses in response to a DCI request

. Aerobic Aquatic Metabolism Studies : The registrants propose providing this information through kineti c a nalysis of aerobic aquatic metabolism studies conducted with br omoxynil octanoate. The r egistrants noted that they will submit these analyses in response to a DCI request

. EFED Response: EFED appreciates the information and will review the photolysis, aerobic soil metabolism, and aerobic aquatic metabolism data for bromoxynil when the studies are submitted.

Analytical Methods : The registrants discussed this topic with Agency and offered the Agency a choice of a common moiety method on standard equipment or a method for each compound on equipment which is not readily available

. The Agency advised that a readily ava i lable common multi

- residue method that included these compounds was also an acceptable app r oach

. The registrants have discovered that a multi

- residue method used by the USGS includes bromox y nil
est ers and phenol and plan to submit this method to fulfill these requirements for water. Since the bromoxynil octanoate method (found to be acceptable without a need for an ILV) is a

common moiety method that includes the phenol and heptanoate, no additiona l effort is needed for soil.

EFED Response: EFED confirms that a common multi

- residue method is an acceptable approach and will review the method when it is submitted.

Environmental Fate Data Submissions and Needs: Bromoxynil Octanoate Aqueous Photolysis : A new aqueous photolysis study has been conducted because of difficulties encountered in previous studies due to low solubility of the ester in water. This study shows that the first degradation step is debromination rather than the formation of bromox ynil phenol and that the resulting quantum yield is 0.069. The registrants will submit this study to the Agency in response to a DCI request.3 Aerobic Soil Metabolism Studies : The registrants are examining an existing study for suitability for submission . The registrants will provide either existing studies or conduct new studies in response to a DCI request

. Adsorption/Desorpt io n : Because of difficulties with degradation occurring dur ing previous studies, a new study has been conducted with bromoxynil octanoate. The results range from 8751 to 32,540, with a mean of 24,739. The registrants noted that they will submit this study to EPA in response to a DCI request

. EFED Response: EFED appreciates the information and will review the photolysis, aerobic soil metabolism, and adsorption/desorption data for bromoxynil octanoate when the studies

are submitted.

Environmental Fate Data Submissions and Needs: Bromoxynil Heptanoate Hydrolysis : A previously conducted study has been identified and is undergoing an examination for suitability. The registrants noted that they will provide either existing studies or conduct ne w studies in response to a DCI request

.

Aerobic Soil Metabolism Study : The registrants agree to conduct a new stu d y in support of the bridging strategy in response to a DCI request

. Adsorption/Desorption : Because of difficulties with degradation occurring during previous studies, a new study has been conducted with bromox ynil heptanoate. The results range f rom 11,191 to 47

, 260, with a mean of 28,013. The registrants will submit this study to EPA in response to a DCI request

. EFED Response: EFED appreciates the information and will review the hydrolysis, aerobic soil met abolism, and adsorption/desorption data for bromoxynil heptanoate when the studies

are submitted.

Aquatic Toxicity Data Gaps The A gency indicate d that a full suite of aquatic plant testing with bromoxynil should be submit ted. The registrants remind ed the Agency that a study with Lemna gibba using bromox ynil has bee n recently submitted (MRID 48540504 ) as well as a study with Navicula (MRID 48540503 )

. In addition

, the registrant noted that there are numerous open literature studies that investigate the toxicity of brom o xynil to algae. Previo usly , a literature review of these studies along with other environmental toxicology studies with other taxa was submitted to the Agency (MRID 48540501). The registrants request that these studies be evaluated for their suitability to fill data gaps identified by the Agency

. EFED Response: The L. gibba and N. pelliculosa studies have been submitted and are currently in review. EFED requests that the registrants additionally submit for review either (1) three additional guideline studies on aquatic non

- vascular plants with bromoxynil or (2) the open literature studies on non

- vascular aquatic plants with bromoxynil they believe will fulfill the guideline requirement for a full suite of aquatic n on

- vascular plant studies.