Docket Number: EPA-HQ-OPP-2009-0755 www.regulations.gov



## Hexazinone Final Work Plan Registration Review August 2010Introduction :

This is EPA’s Final Work Plan (FWP) for the registration review of hexazinone. The FWP includes the expected registration review timeline. The FWP also addresses public comments received concerning the Preliminary Work Plan (PWP) in the Summary Document posted in the hexazinone regi stration review docket (EPA-HQOPP-2009-0755), 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 in formation the Agency believes are needed to make a registration review decision.

The Agency is implementing the regist ration review program and will review each registered pesticide every 15 years to de termine whether it continues to meet the Federal Insecticide, Fungicide, and Rodentic ide Act (FIFRA) standard for registration. Changes in science, public policy, and pesticid e use practices will occur over time. The registration review program is intended to ma ke sure that, as the ability to assess risk evolves and as policies and pract ices change, all registered pe sticides continue to meet the statutory standard. The public phase of registration review begins when the initial docket is opened for each case. Inform ation on this program is provided at: http://www.epa.gov/oppsrr d1/registration_review/

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Hexazinone is a herbicide that was first registered in the United States in 1975 for general weed control in non-cropl and areas, and is currently re gistered for use on alfalfa, blueberries, forest trees, pasture and range grasses, ornamental pl ants, pineapples, and sugarcane to control br oadleaf weeds, grasses, and some woody plants. Hexazinone is a triazine herbicide, but it is structurally and toxicologically dissimilar to the other triazine herbicides such as atrazine. Therefore, hexazinone has not been included in any

cumulative assessment.

Comments Received on Preliminary Work Plan :

The hexazinone registration review docket received five comments during the 60- day comment period on the PWP, which began on May 6, 2010 and ended on July 7, 2010. Although the hexazinone registration re view docket was scheduled to open on March 31, 2010, with a public comment pe riod ending on June 1, 2010, the supporting documents were not posted to the dock et until May 6, 2010, so the public comment period was extended to the proceeding 60 days. The comments received resulted in the removal of three anticipated data requirements and the need for the Agency to revise its registration review ecological risk problem formulation document. However, the comments received do not change the timeline detailed in the hexazinone PWP.

Risk Assessment and Data Needs :

The Agency anticipates conducting an eco logical risk assessment for hexazinone, including an endangered speci es assessment. The Agency also anticipates conducting

human health risk assessments for hexazinone.

3Ecological Risk:

• The Agency has conducted a risk assessmen t that supports a complete endangered species determination for the California Red-Legged Frog (CRLF) as well as

Pacific salmon and steelhead. The CRLF assessment resulted in a “Likely to Adversely Affect” determination for both dir ect and indirect effects to the CRLF. The Agency concluded that hexazinone w ill not present a direct effect on Pacific

salmon and steelhead or their critical hab itat. These assessments were submitted

to the Services for initia tion of formal consultation.

• Terrestrial plant toxicity data (G uidelines 850.4100 and 850.4150), which were identified in the PWP as data needs, will not be required. Information submitted by the registrant during the PWP public co mment period was sufficient to satisfy these data requirements. For more de tails, see the “Summary of Comments Received During the Comment Period” section of this document.

• EPA anticipates needing the following gui deline studies for hexazinone in order to conduct a complete environmental fate and ecological risk assessment during the registration review of hexazinone:

o 835.4100 Aerobic Soil Metabolism

o 835.4200 Anaerobic Soil Metabolism

o 835.4300 Aerobic Aquatic Metabolism

o 835.4400 Anaerobic Aquatic Metabolism

o 835.6100(7) Independent Laboratory Validation of Environmental Chemistry Analytical Method for Soil

o 835.6200(7) Environmental Chemistry An alytical Method for Water and an Associated Independent Laboratory Validation

o 850.2100 Avian Oral Toxicity (Passerine species)

• Please refer to EFED Registration Review Problem Formulation for Hexazinone dated January 12, 2010, located in the hexazinone docket, for a detailed discussion of the anticipated ecological risk assessment needs.

Human Health Risk:

• While there are no registered residential uses of hexazi none, it is registered for use on industrial turf grass, and current labe ls do not restrict this use in residential settings. Since this could potentially result in post-application residential exposure, the Agency intends to conduc t a residential risk assessment during registration review. A new aggregate ri sk assessment may also be needed.

• The Agency intends to conduct a dr inking water exposure assessment for registration review.

4• The hexazinone tolerance expression (40 CFR 180.396) will be reviewed during registration review to ensure that it appropriately covers the metabolites and degradates of hexazinone and that it specifi es the residues to be measured for each commodity.

• The Agency anticipates an updated occupational and occupational postapplication risk assessments will be needed for hexazinone. The new occupational post-application risk assessment will use data from the Agricultural Reentry Task Force to update the exposur e estimates based on current transfer

coefficients. In addition, the existing 48 hour Rest ricted Entry Interval (REI) may

be revisited.

• The Agency anticipates that a revised dietary assessment will be needed.

• Based on comments by the registrant, the Agency will reassess hexazinone toxicity categories and e ndpoints for the upcoming re gistration review human

health risk assessment.

• The field rotational crops data (Guide line 860.1900), which was identified as a data need in the PWP, will not be required. Information submitted by the registrant during the PWP public comment period was sufficient to satisfy this data requirement. The Agency anticipa tes establishing a to lerance of 0.50 ppm

for inadvertent hexazinone residues in/ on corn stover, sorghum stover, and wheat straw. For more details, see the “S ummary of Comments Received During the

Comment Period” sectio n of this document.

• The toxicity and residue chemistry databa ses are complete with the exception of the following guideline studies, which the Agency anticipates requiring in order to conduct a complete human health assessment:

○ 870.3465 28-Day Inhalation Toxicity

○ 870.7800 Immunotoxicity (rats)

○ 870.6200 Neurotoxicity Battery (acu te and subchronic studies)

• Please refer to Hexazinone: Registration Review Scoping Document for Human

Health Assessments dated January 12, 2010, located in the hexazinone docket, for

a detailed discussion of the anticipated human health risk assessment needs.

Endocrine Disruptor Screening Program :

As required under FFDCA section 408(p) , EPA has developed the Endocrine Disruptor Screening Program (EDSP) to dete rmine whether certain substances (including pesticide active and other ingred ients) may have an effect in humans or wildlife similar to an effect produced by a “natur ally occurring estrogen, or othe r such endocrine effects as the Administrator may designate.” The ED SP employs a two-tiered approach to making the statutorily required determinations. Tier 1 consists of a battery of 11 screening assays

5to identify the potential of a chemical substa nce 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 inte ract with E, A, or T hormonal systems will proceed to the next stage of the EDSP wher e EPA will determine which, if any, of the Tier 2 tests are necessary based on the availa ble data. Tier 2 te sting is designed to identify any adverse endocrine related eff ects caused by the substance, and establish a quantitative relationship between the dose and the E, A, or T effect.

Between October 2009 and February 2010, EPA is issuing test orders/data call-ins for the first group of 67 chemicals, which c ontains 58 pesticide ac tive ingredients and 9 inert ingredients. This list of chemicals was selected based on the potential for human exposure through pathways such as food and wa ter, residential activity, and certain postapplication agricultural s cenarios. This list should not be construed as a list of known or likely endocrine disruptors.

Hexazinone is not among the group of 58 pesticide active ingredients on the

initial list to be screened under the EDSP. Under FFDCA sec. 408(p) the Agency must screen all pesticide chemicals. Accord ingly, EPA anticipates issuing future EDSP orders/data call-ins for all registration review cases, including those for which EPA has already opened a registration review docke t for a pesticide active ingredient.

For further information on the status of the EDSP, the policies and procedures, the list of 67 chemicals, the test guidelines and the Tier 1 screening battery, please visit our

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

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6Timeline :

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

Registration Review for Hexazinone– Pr ojected Registration Review Timeline

Activities Estimated Date Opening the docket Open Docket and Public Comment Period 2010 – March

Close Public Comment 2010 – May Case Development

Final Work Plan 2010 – August

Issue DCI 2011 – Apr.- June

Data Submission 2013 – Apr. - June Open Public Comment Period for Preliminary Risk Assessments 2014 – Oct. - Dec.

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

Decision 2015 – Apr. – June.

Close Public Comment Period 2015 – July – Sept. Final Registration Review Decision a nd Begin Post-Decision Follow-up 2016 Total (years) 6

Summary of Comments Received During the Comment Period :

The hexazinone registration review docke t was open for a 60-day comment period beginning on May 6, 2010. Technical registrant DuPont submitted comments on the registration review Problem Formulati on and Scoping documents. The comments challenge the Agency’s understand ing of issues related to en vironmental fate, ecotoxicity, and residue chemistry of hexazinone, as well as the need for several data requirements anticipated in the PWP. Additionally, the regi strant pointed out an error in the Agency’s registration review Scoping Do cument. Page 20 of the document indicates that an acute neurotoxicity study was submitted. However, th e Agency has not received such a study. The Agency appreciates th e registrant’s correction.

A description of the comments received and the Agency’s response to these comments is available in the following docum ents, which are located in the hexazinone registration review docket:

EFED Registration Review Problem Fo rmulation for Hexazinone, August 19,

2010. Hexazinone. Response to Comments from the Revised Registration Review Scoping Document for Human Health Risk Assessments, August 16, 2010.

7Finally, in the PWP, the Agency solic ited comments on three specific topics: environmental justice, water body impairment, and trade irritants. No comments or information were received during the co mment period concerning these issues.

Next Steps :

Risk assessments will be conducted as de tailed in the Risk Assessment and Data

Need section of this document. As noted previously, the Agency will require several studies through the Data Call-In process to conduct comple te human health, ecological, and endangered species risk assessm ents for all uses of hexazinone.

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