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 Fenbutatin-Oxide FINAL WORK PLAN 

Introduction

This is the Environmental Protection Agency’s (EPA’s) Final Work Plan (FWP) for the 

registration review of fenbutatin-oxide. The FWP includes the expected registration 

review timeline. The FWP also addresses public comments received concerning the 

Preliminary Work Plan in the Summary Document, which was posted in the fenbutatinoxide registration review docket (EPA-HQ-OPP-2009-0841), and any other comments 

concerning the initial docket postings. The Summary Document provided information 

on what EPA knows about the pesticide and what additional risk analyses and data or 

information the Agency believes are needed to make a registration review decision. 

The Agency is implementing the new registration review program and will review each 

registered pesticide every 15 years to determine whether it continues to meet the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA) standard for registration. Changes 

in science, public policy, and pesticide use practices will occur over time. The 

registration review program is intended to make sure that, as the ability to assess risk 

evolves and as policies and practices change, all registered pesticides continue to meet 

the statutory standard. The public phase of registration review begins when the initial 

docket is opened for each case. Information on this program is provided at: 

http://www.epa.gov/oppsrrd1/registration_review/. 

Fenbutatin-oxide is an organotin acaricide/insecticide currently registered for ornamental, 

recreational, agricultural and residential uses to control various insects such as thrips, 

whiteflies, mealy bugs, mites, and aphids. Fenbutatin-oxide is a restricted use pesticide 

due to ecological toxicity and, therefore, may only be applied by professional pesticide 

applicators. The mode of action for fenbutatin-oxide is the inhibition of oxidative 

phosphorylation (which affects energy production). There is one technical registration 

and two end-use product registrations containing fenbutatin-oxide. 

Comments Received on Preliminary Work Plan

One comment was received on the fenbutatin-oxide Preliminary Work Plan (PWP) 

during the 60-day public comment period, which began on December 16, 2009 and 

closed on February 16, 2010. This comment did not change the work plan or timeline 

established in the PWP. In addition, through the PWP, EPA solicited comments on three 

specific topics: environmental justice, water body impairment, and trade irritants. No 

comments or information were received during the comment period concerning these 

topics. 
 

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Risk Assessment and Data Needs

Ecological Risk: 

• The most recent ecological risk assessment was completed in August of 2007 in 

support of the fenbutatin-oxide Section 3 assessment for a new use on pistachios. 

• The Agency has not conducted a risk assessment that supports a complete 

endangered species determination. The ecological risk assessment planned during 

registration review will allow the Agency to determine whether the use of 

fenbutatin-oxide has “no effect” or “may affect” federally listed threatened or 

endangered species (listed species) or their designated critical habitats. When an 

assessment concludes that a pesticide’s use “may affect” a listed species or its 

designated critical habitat, the Agency will consult with the U.S. Fish and 

Wildlife Service and/or National Marine Fisheries Service (the Services), as 

appropriate. 

• The Agency anticipates needing the following data in order to conduct an 

endangered species and non-target ecological risk assessment for fenbutatinoxide. 

o (GLN 835.4300) Aerobic Aquatic Metabolism 

o (GLN 835.4400) Anaerobic Aquatic Metabolism 

o (GLN 850.1730) Bioaccumulation in Fish 

o (GLN 850.2100) Avian oral toxicity – Passerine species 

o (GLN 850.1075) Freshwater fish – Acute toxicity 

o (GLN 850.1010) Freshwater invertebrates – Acute toxicity 

o (GLN 850.1350) Mysid chronic toxicity test 

o (GLN 850.1400) Saltwater fish – Early life stage test 

o (GLN 850.1735) Whole sediment toxicity invertebrates, freshwater 

o (GLN 850.1740) Whole sediment toxicity invertebrates, marine 

o (GLN 850.4100) Terrestrial Plant toxicity Tier 1 seedling emergence 

o (GLN 850.4150) Terrestrial Plant toxicity Tier 1 vegetative vigor 

o (GLN 850.5400) Aquatic Plant Growth: algae 

o (GLN 850.4400) Aquatic Plant Growth: vascular plants 

• For more information regarding the status and review of ecological fate and 

effects of fenbutatin-oxide, please refer to the document: Registration Review: 

Problem Formulation for Ecological Risk, Environmental Fate, Endangered 

Species, and Drinking Water Assessments for Fenbutatin-oxide (Vendex) in the 

fenbutatin-oxide registration review docket (EPA-HQ-OPP-2009-0841).
 

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Human Health Risk: 

• The most recent human health assessment for fenbutatin-oxide was completed in 

2007 to establish a tolerance for fenbutatin-oxide use on pistachios. 

• Based upon the anticipated data requirements, the toxicological endpoints may be 

revised during the registration review of fenbutatin-oxide. 

• The Agency anticipates conducting occupational handler and post-application risk 

assessments during the registration review of fenbutatin-oxide, which will 

incorporate any new hazard information. 

• The Agency anticipates conducting a new aggregate assessment, which will only 

include food plus water, since residential exposures are not expected based on 

currently registered uses. 

• The Agency’s residue chemistry database for fenbutatin-oxide is complete. 

However, the Agency anticipates re-calculating the dietary burden from animal 

feeding studies to reflect current methodology and policy. 

• A new drinking water assessment will be conducted during registration review, 

which will include any updated hazard information, and will incorporate drinking 

water exposure values directly into the dietary exposure assessment. 

• Fenbutatin-oxide can only be applied at residential sites (to ornamental plants) by 

commercial applicators. The Agency does not anticipate conducting either a 

residential handler or post-application risk assessment during the registration 

review of fenbutatin-oxide. 

• The Agency anticipates requiring the following studies, in accordance with the 

revised 40CFR Part 158, to conduct a comprehensive human health risk 

assessment for the registration review of fenbutatin-oxide. 

o (GLN 870.7800) Immunotoxicity 

o (GLN 870.3465) 90-Day Inhalation Toxicity 

o (GLN 870.7600) Dermal Absorption 

o (GLN 870.6300) Developmental Neurotoxicity Study 

• The tolerance expression in 40CFR §180.362(a), (b), and (c) will be reviewed 

during registration review to ensure that it appropriately covers the metabolites 

and degrades of fenbutatin oxide, and that it specifies the residues to be measured 

for each commodity. Any proposed revisions would be to the chemical 

description rather than the individual tolerance level(s). 
 

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• For more information on the status and review of the human health effects of 

fenbutatin-oxide, please refer to the document: Fenbutatin-Oxide: Registration 

Review Scoping Document for Human Health Assessments in the fenbutatin-oxide 

registration review docket (EPA-OPPTS-OPP-2009-00841) for a detailed 

discussion of previous human health assessments. 

Timeline

EPA has created the following estimated timeline for the completion of the fenbutatinoxide registration review. 

Registration Review for Fenbutatin-Oxide 

Projected Registration Review Timeline 

Milestone Date 

Opening the Docket 

Open Docket & Public Comment Period for Fenbutatin-Oxide December 2009 

Close Public Comment Period February 2010 

Case Development 

Final Work Plan May 2010 

Issue DCI Jan. – Mar. 2011 

Data Submission Jan. – Mar. 2013 

Open Public Comment for Preliminary RA Jul. – Sept. 2014 

Close Public Comment Period Oct. – Dec. 2014 

Registration Review Decision 

Open Public Comment for Proposed Registration Review Decision Jan. – Mar. 2015 

Close Public Comment Period Apr. – June 2015 

Final Reg. Review Decision and begin post-decision follow-up 2015 

Total 6 years 

Summary of Comments Received During Docket Opening

The fenbutatin-oxide registration review docket was open for a 60-day public comment 

period which began on December 16, 2009. During that time, the FIFRA Endangered 

Species Task Force (FESTF) submitted a comment which is summarized below. The 

comment did not change the work plan or timeline set out in the preliminary work plan. 

Consequently, this document makes final the work plan for the fenbutatin-oxide 

registration review process. 

Comment from FESTF 

The FESTF submitted a comment requesting that any technical registrant for 

fenbutatin-oxide who is not a member of the FESTF (or a company having met its 

data compensation obligations) be asked to provide a formal offer-to-pay to 

FESTF for reliance on their data. 

 
 

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EPA Response 

The Agency thanks FESTF for its comment and will consider this information as 

it conducts the fenbutatin-oxide registration review process. 

Next Steps 

The Agency will develop a data call-in (DCI) notice for the data gaps listed under the 

“Risk Assessment and Data Needs” section above. 

Both an ecological risk assessment, which will include an endangered species 

assessment, and a human health risk assessment will be conducted as detailed in the 

“Risk Assessment and Data Needs” section above.