UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, DC 20460 

OFFICE OF CHEMICAL SAFETY ANO POLLUTION PREVENTION 

PC Code: 111 601 

DP Barcode: 0426 180 

Da te: April 14, 20 15 

MEMORANDUM 

Subject: 

To: 

From: 

Through: 

Response to Public Comments on the EFED Registration Review Problem 

Formulation for Oxyfl uorfen 

Benj amin Askin, Chemical Review Manager 

Tom Moriarty, Team Leader 

Neil Anderson. Branch Chief 

Risk Management and Implementation Branch l 

Pesticide Re-Evaluation Division (7508P) 

Meghan Radtke, Ph.D., Biologist 

He Zhong, Ph.D., Biologist 

Environmental Risk Branch I 

Environmental Fate and Effects 

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In response to the preliminary "Registration Review Problem Formulation for Oxytluorfen" (DP 

4 194 19), Dow AgroSciences LLC (DAS) provided comments during the public comment period. 

The purpose of this memorandum is to address comments that are applicable to EFED's problem 

formulation. 

DAS Comment: The following studies will be submitted to further clarify and update aquatic 

photolysis and degradate data: Yoder 2008 and Volkel 2007. 

EFED Response: The Agency will review the studies and incorporate the information into 

future analyses, as appropriate. 
DAS Comment: Studies will be submitted to address the following data gaps: acute avian oral 

toxicity with a passerine species, acute oral adult honeybee study, saltwater fish acute toxicity, 

and saltwater fish early life-stage. 

EFED Response: The Agency will review the studies and incorporate the information into 

future analyses, as appropriate. 

DAS Comment: "However, in course texture sandy soils of low organic matter content, 

oxytluorfen has the potential to leach into shallow groundwater less than three meters deep (Yen 

et al., 2003)" should be revised to read: Oxyfluorfen is not very mobile in soil and may not 

contaminate groundwater under normal conditions. However, in coarse texture sandy soils of 

extremely low organic matter content, oxytluorfen has the potential to leach into shallow 

groundwater less than three meters deep (Yen et al., 2003). 

EFED Response: The Agency believes its paragraph in the Problem Formulation document 

adequately described the soil types and mobility based on the submitted studies. To make 

changes as requested, the Agency needs clarification from the registrant regarding " normal 

conditions" and the differences between " normal conditions" and "abnormal conditions" in a 

field application scenario. 

DAS Comment: "The chemical is unlikely to leach into groundwater, although limited vertical 

movement through soils may be possible in sandy soils of low organic matter" should be revised 

to read: The chemical is unlikely to leach into groundwater, although limited vertical movement 

through soils may be possible in sandy soils of extremely low organic matter. 

EFED Response: The Agency believes its statement is justified. To add "extremely," as 

requested, the Agency needs c larification of the difference in classification between " low organic 

matter" and '·extremely low organic matter.'· In addition, evidence must be provided to the 

Agency that oxytluorfen has no vertical movement in conditions of low organic matter. 

DAS Comment: Larval honeybee toxicity data, adult honeybee chronic toxicity data, pollinator 

semi-field/feeding data, nectar/pollen residue data, and field testing for pollinators studies are not 

necessary because l) oxyfluorfen is not an insect growth regulator; and 2) there is low to no 

potential for exposure through product use because crops with the highest uses (almonds, wine 

grapes, pistachios, and walnuts) are either not attractive to honeybees and/or have restrictions on 

application timing with respect to the bloom of the crop, which would limit exposure to bees. In 

addition, for these crops, oxyfluorfen is only applied to the weeds within the fields and not to the 

crop canopy because of the potential for serious injury to the crop. 

EFED Response: EFED uses honeybee data as a sun-ogate for determining risk to all insect 

pollinators, not just honeybees. Consequently, the Agency must consider a broader scope of 

pollinator behavior than just honeybees. For example, the times when non-honeybee pollinators 

are active/present may be different than honeybees; likewise, food item attractiveness may also 

differ. 

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I) Although oxyfluorfen is an herbicide and not an insect growth regulator, it may still have 

unintended toxicity to non-target organisms. Unintended toxicity to non-target species is the 

basis for all of the testing required by EFED. DAS asserts that the Schmitzer 20 l l study reports 

a 48-hr LDso > l 09 ~L g ai/bee, which would classify oxyfluorfen as "practically non-toxic" to 

adult honeybees, on an acute basis (note that this study has not been submitted to the Agency yet 

and has not undergone review). This classification is only relevant for acute exposure to adult 

bees and does not account for the toxicity of a longer-term, lower dose exposure. The 

physiology of larval and adult honeybees is different, thus one life stage may be more sensitive 

to a pesti cide than the other. 

2) Oxyfluorfen is registered on numerous outdoor uses in addition to the almonds, wine grapes, 

pistachios, and walnuts cited by OAS. Uses include agri cultural, non-agricultural, and 

residential plants and many of the crops and ornamentals arc considered attractive to pollinators. 

DAS indicates that there are application timing restrictions that would limit exposure to 

pollinators for almonds, wine grapes, pistachios, and walnuts; however, other uses do not have 

these restrictions and a complete exposure pathway to honeybees and other insect pollinators is 

possible. 

The Agency is concerned not only about risks to bees visiting blooming crops or ornamentals, 

but also exposures that occur as a result of spray drift onto adjacent blooming weeds. 

Oxyfl uorfen is generally only directly applied to weeds and not the crop; however, if any of 

those weeds are flowering, this would result in a complete exposure pathway. Application types 

include direct spray, spray, chemigation, broadcast, and band treatment, which could result in 

spray drift. Oxyf1uorfen may drift to blooming non-target plants near the site of application and 

thus, exposure to insect pollinators could occur. 

ln summary, EFED believes that there is a reasonable potential that insect pollinators may be 

exposed to oxyfluorfen. Adult honeybees may be exposed on a chronic basis to oxyf1uorfen 

residues via pollen and nectar. Larvae may be exposed through contaminated pollen and nectar 

that are brought back to the hive. Consequently, the adult chronic and larval acute and 

chronic laboratory toxicity tests are needed to assess risk to bees. Tier 2 (semi-field/feeding 

data, residues in pollen/nectar) and Tier 3 (field testing for pollinators) studies may be 

required if the laboratory-generated toxicity data indicate risk concerns for honeybees. 

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