2 I NTRODUCTION

This is the Environm ental Protection Agency’s (EPA or the Agency ) Final Work Plan (FWP) for the registration review of halosulfuron

- methyl. This work plan addresses public comments received concerning the Preliminary Work Plan (PWP) , which was posted in halosulfuron

methyl's registration review docket (EPA

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- 0745 ). Halosulfuron

- methyl is a sulfonylurea herbicid e that is primarily absorbed through the leaves of plants. Sulfonylurea herbicides disrupt the synthesis of amino acids in plants by inhibiting the enzyme acetolactate synthase (ALS). ALS inhibition in plants adversely affects plant growth and reproducti on. Although the sulfonylurea herbicides all act upon the same enzyme system in plants, that system is not present in humans or other mammals. Halosulfuron

- methyl is registered for use on various crops including corn, cotton, nuts, rice, sorghum, soybean s, squash, sugarcane, and fruiting vegetables to control broadleaf weeds and annual and perennial sedges

. In addition to the agricultural food uses, halosulfuron

- methyl is also registered for use on turfgrass, ornamentals, and a variety of non

- crop areas including, but not limited to, airports, cemeteries, fallow non

crop areas, golf courses, landscaped areas, public recreation areas, residential and commercial lawns, sod and turf farms, sports fields, tennis courts, race tracks, fairgrounds, and rights

- of

- way.

The Agency is implementing the registration review program pursuant to Section 3(g) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and will review each registered pesticide every 15 years to determine whether it continues to meet the F IFRA 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 the statutory standard. The public phase of registration review begins when the initial docket is opened for each case. Informatio n on this program is provided on the Agency’s website 1

. The FWP begins with any updates since the PWP was issued. Next is a summary of substantive
comments received during the public comment period for the PWP concerning anticipated data needs

, expected risk assessments, or the estimated timeline identified in the PWP

, and a

summ ary of the Agency’s response s to th o se comments

. This section is followed by halosulfuron

- methyl's registration review planned data needs, risk assessments expected to be conducted , and the projected registration review timeline. Lastly, there is a discu ssion of next steps.

UPDATES SINCE THE PWP WAS ISSUED

Testing Requirements for Sulfonyl u rea Herbicides

. The Agency is aware of new information suggesting that effects observed in plant reproductive toxicity studies conducted with sulfonylurea herbicides occur at concentrations similar to those at which effects were observed in the guideline vegetative vigo r studies (850.4150). The Agency is currently evaluating this information to determine if additional testing beyond the standard vegetative vigor studies is warranted for this class of compounds, or if data from the vegetative vigor guideline study are

su fficiently protective of potential impacts to plant reproduction.

Focus Meeting with Technical Registrant

. Canyon Group LLC (Canyon)

, a technical registrant of halosulfuron

- methyl, plans to submit European Union (EU) ecotoxicity and environmental fate da ta that they believe may satisfy identified data gaps and/ or justify why certain data are not

1 http://www.epa.gov/oppsrrd1/registration_review/3 needed for the registration review of halosulfuron

- methyl. Upon receipt and review of this information, EPA will determine any impacts on the planned r isk assess ments and data needs. The Agency held a focus meeting with Gowan Company, an agent for Canyon

, on September 19, 2012 and the following was discussed:

• Enhanced Hydrolysis Study; and Fresh Water Fish and Invertebrate Data

- Canyon presented information from a recent open literature publication on the hydrolysis of halosulfuron

- methyl

, as well as EU freshwater fish and invertebrate data

, and will formally submit these studies for Agency review. EPA agrees that these data may fulfill several data requirem ents. However, the enhanced hydrolysis study and freshwater fish and invertebrate studies remain as data requirements until data have been formally submitted and reviewed for acceptability.

• Aerobic Soil Metabolism Study (GLN 835.4100) & Enhanced Aerobic Soil Metabolism Study (Non

- GLN)

- An enhanced aerobic soil metabolism study (in at least 10 soils) is identified as a data gap because of discrepancies between available field and laboratory study results regarding halosulfuron

- methyl’s persistence in diffe rent soils. The study should include information (or limited data) on the decline of halosulfuron

- methyl in at least 10 soils. Full aerobic soil metabolism studies (i.e., with characterization of the formation and decline of major degradates) are to be c onducted for the two soils where halosulfuron

- methyl is most persistent. However, if the aerobic soil metabolism data, which Canyon will be formally submitting for review by the Agency, is found to be acceptable and fulfill s GLN 835.4100, this portion of the (non

- GLN) enhanced aerobic soil metabolism study will not likely be required. The data gaps for GLN 835.4100, aerobic soil metabolism and a non

- guideline enhanced aerobic soil metabolism study will remain until the data have been formally submitted and EPA has completed a full evaluation of the data. Canyon agreed to work with the Agency to develop an appropriate study protocol.

For further details, a summary of this m eeting is posted in the halosulfuron

- methyl registration review docket EPA

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- 0745. If changes are made to the work plan, data requirements, or timeline, the Agency will amend the FWP and announce this amendment in the Federal Register.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60

- day public comment period on the h alosulfuron

- methyl PWP , which opened on March 28, 2012 and closed on May 29, 2012 , the Agency received two sets of public comments. Comments were submitted by Gowan Company LLC, authorized agent for Canyon Group LLC, and the F IFRA Endangered Species Task Force . The comments submitted by Canyon address the planned ecological risk assessment and data requirements

. In the PWP, EPA also solicited comments on the specific topics of environmental justice, water quality concerns , and tr ade irritants, but no comments or information were received on those issues.

This section does not capture every comment made on the PWP nor all of the Agency’s
responses. Summarized below are public comments that addressed the anticipated registration review data needs, risk assessments, and are of a broader regulatory nature. Public comments and EPA responses in their entirety are located in the docket, EPA

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- 0745. Summarized public comments and Agency responses related to the anticipated ecological risk
assessment or data needs are in the EFED Response to Public Comments Submitted on the4 Halosulfuron

- methyl Preliminary Workplan

, dated September 20, 2012 . No comments were received on the anticipated human health risk assessment or data needs.

Comments submitted by Gowen Company LLC, Authorized Agent for Canyon Group LLC in EPA

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.

1. Comment: EPA outlined a requirement for further testing for aerobic soil metabolism of halosulfu ron

- methyl , Guideline 835.4100 and a non

- guideline enhanced aerobic soil metabolism study

. A previously submitted aerobic soil metabolism study, MRID 42 139410, was carried out using an acidic and an alkaline soil that had variance in other soil properties as well. To address EPA’s concerns, an additional laboratory study of the transformation of halosulfuron

- methyl in soil will be submitted under separate cover

.
Response: Cursory review o f the aerobic soil metabolism data supports Canyon’s contention that this study might add to the understanding of the variability in halosulfuron

- methyl degradation in different soils. However, the se data have not been formally submitted or reviewed . Therefore, the requirement s for Guidel ine 835.4100 , aerobic soil metabolism and a

non

- guideline enhanced aerobic soil metabolism study will remain until the data have been formally submitted and E PA has completed a full evaluation of the data.

2. Comment: Canyon disagrees with EPA’s require ment for a non

- guideline hydrolysis study for halosulfuron

- methyl. A previously submitted study, MRID 42139409 was acceptable and fulfilled Guideline 835.2120, hydrolysis. It is well known that hydrolysis rates of halosulfuron

methyl, and other sulfonylure as (SUs), change with regard to pH and temperature. There are several recent papers in the published literature that address t his issue for SUs in general and for halosulfuron

- methyl in particular

. Canyon believes that an additional study will not provide new or additional data that can be used to refine the halosulfuron

- methyl risk assessment.

Response: The Agency does not believe Canyon Group has provided sufficient justification that the change in halosulfuron

- methyl hydrolysis rates

, with factors such as pH and temperature

, has been adequately addressed solely from the existing guideline study. Often in standard hydrolysis studies

, pesticides degrade with a predictable , defined trend of increasing or decreasing rate , with increasing or decreasing pH r eflecting a single dominating site for hydrolysis on the pesticide molecule ; or at least consistent effects at multiple active sites. Although there was a trend for an increase in the halosulfuron

- methyl hydrolysis rate with higher pH in the standard guid eline study, this does not appear to be a consistent trend in the environment as some field dissipation rates were slower than expected . A lso a published study seems to confirm that there are more complex trends affecting the hydrolysis rate

. Per the Sep tember 19, 2012 meeting between EPA and Canyon

, this study will be formally submitted by Canyon and reviewed by the Agency. However, t he enhanced hydrolysis study remains a s a data requirement until the data have been formally submitted and reviewed for acceptability.

3. Comment: Canyon disagrees with EPA’s requirement for a non

- guideline non

- target plant reproductive toxicity test. It is reasonable to conclude that effects on reproduction and growth in terrestrial plants would be comparable to those in higher aquatic plants such as Lemna gibba

. Consequently, it should not be necessary to conduct further studies with terrestrial plant s as it can be concluded that the toxicity end points in the seedling emergence and vegetative vigor studies are conserva tive and represent a worst case for growth and reproduction.

Response: The Agency is aware of new information suggesting that effects observed in plant5 reproductive toxicity studies conducted with sulfonylurea herbicides occur at concentrations similar t o those at which effects were observed in the guideline vegetative vigor studies (850.4150). The Agency is currently evaluating this information to determine if additional testing beyond the standard vegetative vigor studies is warranted for this class of compounds, or if data from the vegetative vigor guideline study are sufficiently protective of potential impacts to plant reproduction.

4. Comment: E PA outlined a requirement for Guideline 850.1010, acute toxicity freshwater invertebrate test, and Guideline 850.1075, acute freshwater fish toxicity test, because halosulfuron

- methyl will be directly applied to water when used on rice. In response to this requirement, Canyon has provided study reports testing a formulated product on freshwa ter fish and aquatic invertebrates

.
Response: Cursory review of these studies su pports Canyon’s contention that the toxicity exhibited by the products derives from the active ingredient, as the toxicity endpoints are comparable. However, the studies hav e not been formally submitted to EPA. Therefore, Guidelines 850.1010 , acute toxicity freshwater invertebrate and 850.1075 , acute freshwater fish toxicity remain as data gaps for Canyon until the data have been formally submitted and reviewed for acceptabi lity.

5. Comment: EPA outlined a requirement for submission of environmental chemistry methods for halosulfuron

- methyl and its metabolites in soil and water along with an independent laboratory validation, Guidelines 835.6100 and 835.6200 (Footnote 7 of 40 CFR 158.1300). Canyon Group provided a detailed listing of the analytical methods that have been historically submitted to the Agenc y. Canyon state d that all of these methods will be resubmitted but notes that a method for halosulfuron

- methyl and its major metabolites has been shown to be robust and repro ducible over a two

- year period.

Response: The summary of the available analytical methods is useful, but an independent laboratory validation of a method or methods for halosulfuron

- methyl and its major metabolites in soil and water will still be required.

Comment submitted by FIFRA Endangered Species Task Force in EPA

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1

. Comment: The FIFRA Endangered Species Task Force (FESTF) submitted a comment that neither of the halosu lfuron

- methyl technical registrants are member s of the FESTF ; and therefore

, must provide a formal offer

- to

- pay to FESTF in conjunction with their support of the active ingredient , or develop similar data on their own to provide for EPA risk assessments for registration review.

Response: The Agency thanks FESTF for its comment

. However, Canyon Group is a joint venture between Gowan Company and Nissan Chemical Industries . As Gowan is a member of FESTF, EPA expects that Gowan could rely on any FESTF data used for risk assessment
purposes.

PLANNED DATA NEEDS

The table below summarizes the planned data needs for halosulfuron

- methyl based on Registration Review : Preliminary Problem Formulation for the Environmental F ate and6 Ecological Risk, Endangered Sp ecies and Drinking Water Assessments for Halosulfuron

- methyl

, March 8, 2012, the Halosulfuron

- methyl : Human Health Assessment Scoping Document in Support of Registration Review

, March 6, 2012, and EFED Response to Public Comments Submitted on the Halosulfuron

- methyl Preliminary Workplan

, dated September 20, 2012

.

Planned D ata Needs for Halosulfuron

- methyl ’ s Registration Review

Guideline Number Study Title Test Material Estimated Timeframe (Months from receipt of DCI)

835.4100 Aerobic Soil Metabolism (two soils) TGAI 24

835.4300 Aerobic Aquatic Metabolism TGAI 24

835.6100 Terrestrial Field Dissipation 2 TGAI 12

835.6200 Aquatic Field Dissipation TEP 24

850.1010 Acute Toxicity Freshwater Invertebrates TEP 12

850.1075 Acute Freshwater Fish Toxicity TEP 12

860.1650 Submittal of Analytical Reference Standards 3 PAI; residue of

concern 24

870.7800 Immunotoxicity TGAI 12 NON

GDLN Enhanced Aerobic Soil Metabolism Study 4 TGAI 48

NON

GDLN Enhanced Hydrolysis Study 5 TGAI 12

NON

GDLN Special Study for Non

- target Plant Reproductive Toxicity 6 TEP 24
TGAI = technical grade active ingredient; TEP = typical end

- use product ; PAI= pure active ingredient.

RISK ASSESSMENTS FOR REGISTRATION REVIEW

During registration review, t he Agency will conduct a comprehensive ecological risk assessment, including an endangered species assessment, for all uses of halosulfuron

- methyl

. The Agency does not anticipate conducting updated dietary , residential, aggregate, or occupational risk

2 See footnote 7 of 40 CFR 158.1300. The DCI will require only the environmental chemistry analytical method and independent laboratory validation portion s of GLN 835.6100

, Terrestrial Field Dissipation. 3 Analytical reference standards are available for halosulfuron

- methyl and the 3

- CSA (3

- chlorosulfonamide acid) metabolite but not for the rearrangement ester (RRE) of halosulfuron

- methyl. An analyt ical reference standard for the RRE of halosulfuron

methyl must be submitted to the EPA National Pesticide Standards Repository.
4 The DCI will require a protocol be submitted within 90 days of receipt of the DCI for review and approval by the Agency prior to initiation of this study. 5 The DCI will require the protocol for GLN 835.2120

, hydrolysis be followed

. Suggested parameters include testing at pHs of 5, 7, and 9 and at temperatures of 10, 15, 20, and 25 C for 60 days (and additional ly pH 4, 6, and 8 at 15 C), and analysis for halosulfuron

- methyl and potential major hydrolysis products. 6 The Agency is currently evaluating new information to determine if additional testing beyond the standard vegetative vigor studies is warranted for this class of comp ounds, or if data from the vegetative vigor guideline study are sufficiently protective of potential impacts to plant reproduction.7 assessment s during regist ration review. N o risks above the Agency’s level of concern were identified in the most recent human health assessment; and changes in Agency models and policies that have occurred since that assessment are not expected to alter risk conclusions. Theref ore, the Agency plans to rely on the most recent comprehensive human health assessment in making its registration review decision. If the results of the additional toxicity study that is expected to be required changes assessment endpoints or uncertain t y/ safety factors, the Agency will reconsider the need for an updated human health risk assessment.

The table below summarizes the planned registration review risk assessments based on the EFED Problem Formulation and HED Scoping Document . T he planned assessments have not changed from what was included in the PWP

.

Planned Risk Assessments for Halosulfuron

- methyl's Registration Review
Type of Risk Assessment Conduct ? Notes
Eco logical and Environmental Fate Comprehensive ecological (species to be assessed include terrestrial and aquatic organisms ), including endangered species Y

Incidents Y For a discussion of halosulfuron

- methyl's reported ecological incidents, see page 26 of the Problem Formulation. Human Health Dietary Food N If the results of the additional toxicity study that is expected to be required changes assessment endpoints or uncertain t y/safety factors, the Agency will reconsider the need for updated human health dietary risk assessments. Drinking water N

Occupational Handlers (mixers, loaders, applicators) N If the results of the additional toxicity study that is expected to be required changes assessment endpoints or uncertain t y/safety factors, the Agency will reconsider the need for updated human health occupational risk assessments. Post

- application N

Residential Handlers N If the results of the additional toxicity study that is expected to be required changes as sessment endpoints or uncertaint y/safety factors, the Agency will reconsider the need for updated human health residential risk assessments. Post

- application N

Other Aggregate N E valuates the combined risk from dietary and residential exposures. Cumulative N8 Planned Risk Assessments for Halosulfuron

- methyl's Registration Review
Type of Risk Assessment Conduct? Notes
Other Tolerances Y The Agency anticipates updating the current halosulfuron

- methyl tolerance expression in 40 CFR §180. 479 to be consistent with the Chemical Abstracts Service (CAS) nomenclature or the International Union of Pure and Applied Chemistry (IUPAC) nomenclature. Incidents Y For a discussion of halosulfuron

- methyl's reported human incidents, see page 10 of the Scoping Document.

TIMELINE

EPA has created the following estimated timeline for the completion of halosulfuron

- methyl's registration review

. The projected timeline has not changed since the PWP.

Registration Review for Halosulfuron

- methyl

– Projected Registration Review Timeline
Activities Estimated Date Opening the Docket Open Docket and Public Comment Period March 2012

– Completed Close Public Comment May 2012

– Completed Case Development Final Work Plan Sept

. 2012

– Completed Issue DCI April

– June 2013 Data Submission April

– June 2017 Open Public Comment Period for Draft Risk Assessments Oct.

– Dec. 2018 Close Public Comment Period Jan.

– March 2019 Registration Review Decision Open Public Comment Period for Proposed Registration Review Decision April

– June 2019 Close Public Comment Period July

– Sept. 2019 Registration Review Decision and Begin Post

- Decision Follow

- up 2020 Total (years) 8

NEXT STEPS

As noted previously, the Agency plans to require several environmental fate, ecological effects, and human health studies for halosulfuron

- methyl through a data call

- in, expected to be issued in mid

- 2013.