2

I NTRODUCTION

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

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

methyl registration review docket (EPA

- HQ

- OPP

- 2012

- 0833 ). Mesosulfuron

- methyl is an herbicide in the sulfonylurea family and is registered f or use as a post

- emergence treatment to control annual grasses and broadleaf weeds, especially wild oat (Avena fatua ) and wild mustard (Synapis arvensis), in triticale and wheat (winter, spring, and durum).

The Agency is implementing the registration revi ew 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 FIFRA standard for registration. Changes in scie nce, 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 statu tory 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

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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 summary of the Agency’s response s to th o se comments

. This section is followed by registration review planned data needs, risk assessments expected to be conducted , and the projected registration review timeline for mesosulfuron

- methyl

. Lastly, there is a discussion of next steps.

UPDATES SINCE THE PWP W AS ISSUED

The Agency previously requested evidence that weathered and aged residues are efficiently extracted by the enforcement procedure (possibly using radioactive samples from the livestock metabolism studies); however, HED has now determined that thi s requirement can be waived because the extraction solvents in the goat and hen metabolism studies and in the enforcement method are similar.

The Agency, based on a weight of evidence approach, concludes that immunotoxicity studies are not required as this time for bensulfuron

- methyl, chlorsulfuron, ethametsulfuron, flazasulfuron, foramsulfuron, halosulfuron

- methyl, mesosulfuron

- methyl , metsulfuron

- methyl, orthosulfamuron, primisulfuron

- methyl, prosulfuron, sulfometuron

- methyl, sulfosulfuron, triasulfur on, and triflusulfuron

- methyl.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60

- day public comment period on the m esosulfuron

- methyl Preliminary Work Plan

, which opened on June 26, 2013 and closed on August 26, 2013 , the Agency received 2 public

co mments. Comments were submitted by Bayer Crop Science and the FIFRA Endangered

1 http://www.epa.gov/oppsrrd1/registration_review/3

Species Task Force ( FESTF )

. The co mments do not address the timeline described in the PWP, but they do address the planned ecological and human health risk assessments and data requirements. In the PWP, EPA also solicited comments on the specific topics of environmental justice, water quality concerns , and trade irritants, but no comments or information were received on those issues.

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

HQ

- OPP

- 2012

- 0833 . Summarized public comments and Agency responses related to the anticipated ecological risk assessment or data needs are in the Response to Public Comments on the Mesosulfuron

- methyl Registration

- Review Problem Formulation

. Comments submitted by FIFRA Endangered Species Task Force (FESTF ) in EPA

- HQ

OPP

- 2012

- 0833

- 0009

.

1. Comment: The Preliminary Work Plan notes that an endangered species determination ha s not yet been completed. In response to the Agency’s endangered species data requirements, data developed by FESTF will address species proximity to Mesosulfuron

- methyl uses.

Response: The Agency is aware of the data developed by FESTF for Mesosulfuron

- methyl and when appropriate will use that data to fulfill data requirements.

Comments submitted by Bayer Crop Science in EPA

- HQ

- OPP

- 2012

- 0833

- 0010

.

2

. Comment: There are no unknown major metabolites in the submitted study. All metabolites were identified and described in the reports MRID s 45386430 and 45386431. The structures of the metabolites are reported. BCS also synthesized these metabolites. Metabolite Unknown A (coded as BCS

- CV14885) was synthesized and shown not to have any herbicidal activity (Rosinger, C., 1999; MRID 45386331).Similarly Unknown D (coded as BCS

- CO60720) was synthesized and tested with Lemna and green algae and found to be non

- toxic. Therefore, based on the structural elucidation of these metabolites, the submitted report (Steinfuhrer and Zumdick, 2000; MRID 45386430) should fulfill the requirements and repeat of the study is not warranted.

Response: Two major degradates (unknown A and unknown D) were thought to be unidentified at the time of the problem formulation. BCS indicated that structures (coded BCS

- CV14885 and BCS

- CO60720) were proposed in the aerobic aquatic metabolism study (MRID 45386430). EFED acknowledges these structures.

Data needs we re reassessed given this new information and EFED has revised its recommendations on the value of data on toxicity to certain aquatic organisms (see below)

. EFED does not have any toxicity data for BCS

- CV14885 or BCS

- CO60720 (BCS incorrectly indicates tha t MRID 45386331 contains information about herbicidal activity of these degradates). BCS

- CV14885 and BCS

- CO60720 are SU bridge

- intact degradates; therefore, toxicity to terrestrial and aquatic plants will be assumed the same as that of mesosulfuron

- methyl in the absence of data and a TTR approach will be used to estimate EECs. Following the same4

assessment procedures in the problem formulation, it was determined that BCS

- CV14885 and BCS

- CO60720 toxicity studies with fish, aquatic invertebrates, aquatic no n

- vascular plants, birds, and mammals are unlikely to change risk conclusions. However, the lack of BCS

CV14885 and BCS

- CO60720 toxicity information for aquatic vascular plants could impact risk conclusions (see pg 22 of problem formulation).

In addit ion, a recent DER review found that the available ECM/ILV water studies (MRID 46451 701 and 46451702) did not include the major degradates of mesosulfuron

- methyl in aquatic environments (USEPA, 2013).

The following studies are recommended in addition to those indicated in the problem formulation: Aquatic plant growth (850.4400)

- vascular plant (BCS

- CV14885 and BCS

- CO60720)

ECM/ILV (water) (850.6100)

- to include the major degradates observed in aquatic environments (AE F160459, AE F160460, AE F140584, AE F147447, AE F092944, BCS

- CV14885 (benzoic acid with guanidine), and BCS

- CO60720 (methyl ester of benzoic acid with guanidine) )

The following study is no longer recommended: Aerobic Aquatic Metabolism (835.4300)

Modifications are made for the followin g study recommended in the problem formulation: ECM/ILV ( soil ) (850.6100)

- to include the major degradates observed in soil environments (AE F154851, AE F099095, and AE F092944) . Minor degradate observed in the soil environment are not recommended.5

PLANNED DATA NEEDS Table 1 below summarizes the planned data needs for m esosulfuron

- methyl based on the Registration Review: Preliminary Problem Formulation for Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments for Mesosulfuron

- methyl

, Mesosulfuron

- methyl

. and Response to Public Comments on the Mesosulfuron

- methyl Registration

- Review Problem Formulation

. The table has been updated since the PWP to reflect public comments which resulted in changes to the data needs

.

Table 1: Planned D ata Needs for the Mesosulfuron

- methyl Registration Review

Guideline Number 2 Study Title 2 Test Material Estimated Timeframe (Months from receipt of DCI)

835.6200 Aquatic Field Dissipation TGAI 24

850.4400 Aquatic plant growth (vascular plants) BCS

- CV14885 BCS

- CO60720 AE F154851 AE F140584 12

850.4500 Aquatic plant growth (freshwater green alga) TGAI 12

850.6100 Environmental chemistry methods and associated independent laboratory validation. (Water) AE F160459 AE F160460 AE F140584 AE F147447 AE F092944 BCS

- CV14885 BCS

- CO60720 12

Environmental chemistry methods and associated independent

laboratory validation. (Soil) AE F154851 AE F099095 AE F092944 12

870.7800 Immunotoxicity 3 TGAI 12 Non

- guideline (Special Study) Non

- Target Plant Reproductive Toxicity 4 TEP 24

TGAI = technical grade active ingredient; TEP = typical end

- use product ;

2 On June 27, 2012, EPA announced certain revisions in harmonized guideline series 850

– Ecological Effects Tests

– including renumbering and other designations or changes for some guideline studies. See “Final Test Guidelines; OCSPP 850 Series; Notice of A vailability” 77 FR 38282, June 27, 2012. http://www.regulations.gov/#!documentDetail;D=EPA

- HQ

- OPPT

- 2009

- 0154

- 0028
3 Based on the weight of evidence approach (WOE) dete rmined in part by review of previously submitted data for other sulfonyl urea herbicide s , the Agency has determined that generation of new Immunotoxicity studies for each sulfonyl urea herbicide is unnecessary. The previously submitted data provide suffic ient information for EPA to characterize potential impacts of the sulfonyl urea herbicides on Immunotoxicity . Therefore, to satisfy this anticipated data requirement, registrants may wish to consider citing these existing data in re sponse to the DCI that the Agenc y expects to issue.
4 Based in part on a review of previously submitted data for another sulfonyl urea herbicide, the Agency has determined that generation of new non

- guideline plant reproduction studies for each sulfonyl urea herbicide is

unneces sary. The previously submitted data provide sufficient information for EPA to characterize potential impacts of the sulfonyl urea herbicides on plant reproduction. Therefore, to satisfy this anticipated data requirement, registrants may wish to consider citing these existing data in re sponse to the DCI that the Agenc y expects to issue.6

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 m esosulfuron

- methyl. For human health, EPA will evaluate whether the existing dietary and occupational risk assessments will need to be updated during re gistration review. If toxicological endpoints or points of departure are revised, they will be considered in the new assessment s , as well as any changes to the standard operating p rocedures

, default exposure assumptions , and estimated drinking water

concen trations.

Table 2 below summarizes the planned registration review risk assessments based on the EFED Problem Formulation and HED Scoping Document and the planned assessments have not changed from what was included in the PWP

.

Table 2: Planned Risk Assessments for the Mesosulfuron

- methyl 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 Yes

Incidents Will check for updates For a discussion of reported ecological incidents for

m esosulfuron

- methyl, see page 19 of the Problem Formulation. Human Health Dietary Food Yes Drinking water Yes I f drinking water r es idu es of concern or estimated residue levels in drinking water are r evised, a new drinking water assessment may be needed. Occupational Handlers (mixers, loaders, applicators) Yes A revised up

- to

- date occupational handler assessment may be needed during Registration Review to account for changes to the Agency’s Occupational and Residential Exposure policies

. Post

- application No There is no dermal endpoint for mesosulfuron

methyl

. Residential Handlers No There are no residential uses of mesosulfuron

methyl.7

Table 2: Planned Risk Assessments for the Mesosulfuron

- methyl Registration Review
Post

- application No There are no residential uses of mesosulfuron

methyl , so a conventional residential post

- application assessment will not be conducted during Registration Review; however, the Agency will examine the need for a spray drift and volatilization assessment for mesosulfuron

- methyl during Reg istration Review. Other Aggregate Yes An aggregate assessment that e valuates the combined risk from dietary and residential exposures will be conducted if drinking water r es idu es of concern or estimated residue levels in drinking water are r evised and a new drinking water assessment is undertaken, or if an assessment is conducted for exposures from spray drift or volatilization

. Cumulative No Mesosulfuron

- methyl has not been identified as a member of a cumulative group that shares a common mechanism of toxicity in mammalian species. Tolerances No Tolerances will not be reassessed, but the tolerance expression for mesosulfuron

- methyl will be revised. See page 8 of the Scoping Document. Incidents Will check for updates For a discussion of reported human incidents for

m esosulfuron

- methyl, see page 8 of the Scoping Document and Mesosulfuron

- methyl: Review of Human Incidents

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TIMELINE

EPA has created the following estimated timeline for the completion of the m esosulfur on

- methyl registration review in Table 3 below

. The projected timeline has changed since the PWP.

Table 3: Registration Review for Mesosulfuron

- methyl

– Projected Registration Review Timeline Activities Estimated Date Opening the D ocket Open Docket and 60

- day Public Comment Period June 2013

– Completed Close Public Comment August 2013

– Completed Case Development Final Work Plan November 2013

– Completed Issue DCI 2014 January

- March Data Submission 2016 January

- March 60

- day Public Comment Period for Draft Risk Assessments 5 2018 July

- September Registration Review Decision 60

- day Public Comment Period for Proposed Registration Review D ecision 2018 January

– March

Registration Review D ecision and Begin P ost

- D ecision F ollow

- up 2019 Total ( years ) 6

NEXT STEPS

As noted previously, the Agency plans to requ ire several environmental fate and ecological effects studies for m esosulfuron

- methyl through a D ata C all

- I n Notice , expected to be issued in January

- March of 2014

.

5 The regulations governing Registration Review generally require the Agency to provide a public comment period of at least 30 calendar days for draft risk assessments; see 40 CFR Part 155.53(c). For conventional pesticides, the Agency plans to provide a 60 calendar day public comment period generally for draft risk assessments.