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Docket Number EPA-HQ-OPP-2011-0706 

www.regulations.gov

Tralkoxydim Final Work Plan 

Registration Review 

February 2012 

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Introduction

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

the registration review of tralkoxydim. The FWP includes the expected registration review 

timeline. The FWP also addresses any public comments received on the Preliminary Work Plan 

(PWP) in the Summary Document, which was posted in the tralkoxydim registration review 

docket (EPA-HQ-OPP-2011-0706). The Summary Document, dated September 27, 2011, 

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’s implementation of the registration review program requires review of 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 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 that 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/. 

Tralkoxydim is a systemic, postemergence herbicide registered for agricultural use to selectively 

control certain annual grass weeds in wheat, barley, and triticale. Target weeds include wild 

oats, green foxtail, yellow foxtail, annual ryegrass (Italian), and Persian darnel. There are 

currently no residential uses. Tralkoxydim was first registered in the U.S. in 1998; therefore, it 

was not subject to the reregistration requirements of FIFRA. 

Comments Received on the Summary Document 

No comments were received during the 60-day public comment period on the planned ecological 

assessment and human health scoping document discussed in the Preliminary Work Plan. In the 

Preliminary Work Plan, EPA also 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 three topics. 

Anticipated Risk Assessment and Data Needs

The Agency will conduct comprehensive human health and ecological risk assessments, 

including an endangered species risk assessment, for all uses of tralkoxydim. The Agency will 

require data for use in conducting these assessments. Below is a summary of the issues relevant 

to the registration review of tralkoxydim and a list of the data requirements. 
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Ecological Risk: 

• The most recent ecological risk assessment was a Section 3 review conducted in 1998 in 

support of new uses of tralkoxydim on wheat and barley. 

• The Agency will conduct an updated environmental fate and ecological risk assessment 

for tralkoxydim, including an endangered species assessment, during registration review. 

The new assessment will incorporate the most up-to-date modeling methodologies, 

updated toxicological endpoints, and any new data submitted and determined to be 

adequate. 

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

species determination for tralkoxydim. The ecological risk assessment planned during 

registration review will allow the Agency to determine whether tralkoxydim’s use 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 (USFWS) and/or National Marine 

Fisheries Service (NMFS) (the Services), as appropriate. 

• Data gaps exist in the environmental fate and ecological toxicity database for tralkoxydim 

and two of its degradates. The Agency needs the following data for use in conducting a 

complete ecological risk assessment, including an endangered species assessment, for 

tralkoxydim and its degradates:

Environmental Fate

o Guideline Number 835.4300 – Aerobic Aquatic Metabolism with Compounds 8 and 

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Ecological Toxicity

o Guideline Number 850.1400 – Fish Early Life-stage Toxicity Test (freshwater) with 

tralkoxydim TGAI 

• Please refer to the Problem Formulation for the Environmental Fate, Ecological Risk, 

Endangered Species, and Drinking Water Exposure Assessments in Support of 

Registration Review of Tralkoxydim, dated September 13, 2011, located in docket EPAHQ-OPP-2011-0706 at www.regulations.gov, for a more detailed discussion of the 

ecological risk assessment and data needs.
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Human Health Risk: 

• The most recent human health risk assessments were conducted in the 1999 Health 

Effects Division Risk Characterization Document for the First Food Use of Tralkoxydim 

in/on Wheat and Barley. 

• During registration review, the endpoints, doses, and safety factors used in the most 

recent human health risk assessments will be revisited based on current policy as well as 

to incorporate any new data received and determined to be adequate. 

• The Agency will conduct updated dietary (food and water), aggregate, and occupational 

exposure risk assessments to include any changes in toxicological endpoints, doses, and 

procedures for risk assessment. 

• The Agency will also conduct an updated drinking water exposure risk assessment during 

registration review. 

• Currently, there are no registered residential uses for tralkoxydim or uses that would 

result in residential exposure. However, residential bystander inhalation exposures 

resulting from off-site transport (e.g., spray drift or volatilization) may occur as a result 

of applications of tralkoxydim. The Agency is in the process of examining its policies 

and refining the methods used to complete residential exposure assessments. Therefore, 

the potential need for a bystander inhalation risk assessment for tralkoxydim will be 

examined during registration review. 

 

• During registration review, the Agency will conduct both an occupational handler 

exposure risk assessment and an occupational postapplication exposure risk assessment 

based on updated doses, endpoints, and procedures for risk assessment. 

• The tolerance expression for tralkoxydim in 40 CFR §180.548 will be reviewed during 

registration review to ensure that it appropriately covers the metabolites and degradates 

of tralkoxydim and that it specifies the residues to be measured in each commodity. 

• The Agency will modify tolerance levels as needed, and work to harmonize 

tolerances/maximum residue limits (MRL), where possible, in key export markets during 

registration review. 
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• The toxicity database for tralkoxydim is complete except for the following studies, which 

the Agency will require for use in conducting an updated human health risk assessment: 

Toxicology Data

o Guideline Number 870.6200 – Acute and Subchronic Neurotoxicity 

o Guideline Number 870.7800 – Immunotoxicity 

• Please refer to Tralkoxydim. Human Health Assessment Scoping Document in Support of 

Registration Review ̧ dated September 19, 2011, available in docket EPA-HQ-OPP-2011-0706 at 

www.regulations.gov, for a detailed discussion of the human health risk assessment and data 

needs. 

Endocrine Disruptor Screening Program

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. As part of its most recent registration decision, EPA reviewed these data and 

selected the most sensitive endpoints for relevant risk assessment scenarios from the existing 

hazard database. However, as required by FFDCA section 408(p), tralkoxydim is subject to the 

endocrine screening part of the Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. Tralkoxydim 
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is not among the group of 58 pesticide active ingredients on the initial list to be screened under 

the EDSP. Accordingly, as part of registration review, EPA will issue future EDSP orders/data 

call-ins, requiring the submission of EDSP screening assays for tralkoxydim. For further 

information on the status of the EDSP, the policies and procedures, the list of 67 chemicals, 

future lists, the test guidelines and the Tier 1 screening battery, please visit our website: 

http://www.epa.gov/endo/. 

Timeline

 

The projected timeline for the completion of the tralkoxydim registration review is presented in 

Table 1. 

Table 1. Projected Tralkoxydim Registration Review Timeline 

Activity Estimated Date 

Opening the Docket 

Open Docket and Open Public Comment Period 2011 – September 

Close Public Comment Period 2011 – November 

Case Development 

Develop Final Work Plan (FWP) 2012 – February 

Issue Data Call-In (DCI) 2012 – Oct. – Dec. 

Data Submission 2014 – Oct. – Dec. 

Develop Preliminary Risk Assessments and Open Public Comment 

Period 

2016 – April – June 

Close Public Comment Period 2016 – July – Sept. 

Registration Review Decision 

Develop Proposed Registration Review Decision and Open Public 

Comment Period 

2016 – Oct. – Dec. 

Close Public Comment Period 2017 – Jan. – March 

Issue Registration Review Decision and Begin Post-Decision Follow-up 2017 

Total (years) 6 

 

Next Steps

The Agency plans to conduct a human health risk assessment and comprehensive ecological risk 

assessment, including an endangered species risk assessment, for tralkoxydim. Drafts of the risk 

assessments are scheduled to be available for public comment in 2016.