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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 (CI)jet:. , {;rd !.,+----/ \~r JeanHolmes,RAPL rt'Jr,tf f~ .-r//1 !j 

Environmental Risk Branch II 

Environmental Fate and Effects Division (7507P) 

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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. 

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Bridging Strategy

The registrants believe that a bridging strategy is appropriate and is supported by existing data. 

In response to the upcoming data call-in the registrants will submit existing studies or conduct 

new studies to provide the requested information.

EFED Response: EFED will review the data when they are submitted.

Environmental Fate Data Submissions and Needs: Bromoxynil 

Aqueous Photolysis: A new aqueous photolysis study is in progress for bromoxynil octanoate 

and a decision will be made whether to conduct a similar study for bromoxynil phenol or 

consider the bromoxynil stable to hydrolysis after the bromoxynil octanoate study is complete. 

The bromoxynil 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 

of bromoxynil phenol. The registrants were appreciative of the advice of the Agency that 

conducting this study could be very helpful in endangered species assessments and will consider 

this advice in making their decision.

Aerobic Soil Metabolism Studies: The registrants propose providing this information through

kinetic analysis of aerobic soil metabolism studies conducted with bromoxynil octanoate. The 

registrants noted that they will submit these analyses in response to a DCI request.

Aerobic Aquatic Metabolism Studies: The registrants propose providing this information through

kinetic analysis of aerobic aquatic metabolism studies conducted with bromoxynil octanoate. 

The registrants 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 available common 

multi-residue method that included these compounds was also an acceptable approach. The 

registrants have discovered that a multi-residue method used by the USGS includes bromoxynil 

esters 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 additional 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 bromoxynil 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.
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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/Desorption: Because of difficulties with degradation occurring during 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 new

studies in response to a DCI request.

Aerobic Soil Metabolism Study: The registrants agree to conduct a new study 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 bromoxynil heptanoate. The results range from

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 metabolism, and adsorption/desorption data for bromoxynil heptanoate when the studies 

are submitted. 

Aquatic Toxicity Data Gaps

The Agency indicated that a full suite of aquatic plant testing with bromoxynil should be 

submitted. The registrants reminded the Agency that a study with Lemna gibba using 

bromoxynil has been 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 bromoxynil to algae. Previously, 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 non-vascular plant studies.