2 INTRODUCTION

This is the Environmental Protection Agency’s (E PA or the Agency) Final Work Plan (FWP) for the registration review of MSMA. This work plan addresses pub lic comments received concerning the Preliminary Work Plan (PWP), which was posted in the MSMA registration review docket (EPA-HQ-OPP-2013-0107). MSMA is a broad-spectrum, post-emergent, organic arsenical herbicide currently registered for use to selectively control gras ses and broadleaf weeds in cotton and turf grass ( i.e ., golf courses, sod farms, and highway rights-of-way). MSMA cannot be used in Florida, except for on cotton in certain counties.

The remaining uses on turf grass were to be phased out and prohibited after December 31, 2013 according to a 2009 Agreement in Principle with the technical registrants. However, the 2009 Agreement also provided for a scientific peer re view related to the carc inogenic mode of action (MOA) of inorganic arsenic (iAs), prior to the final phase-out of the remaining MSMA turf uses. In light of a Congressional di rective to the National Academy of Sciences (NAS) (House Report 112-151 accompanying HR 2584) to evaluate the carcinogenic mode of action of inorganic arsenic, EPA and the MSMA registrants recently agreed to modify the 2009 Agreement (letter from Richard P. Keigwin Jr., Director, Pestic ide Re-evaluation Division, to Lynn Bergeson on behalf of the Organic Arsenical Products Task Force, dated Sept. 14, 201 2) to include the NAS as a potential peer review body. It is EPA’s current intention to rely on the NAS for the peer review of the mode of action, a lthough EPA retains the right to utilize eith er of the Agency’s scientific peer review bodies (Science Advisory Board or FIFR A Science Advisory Panel) if it later determines that utilization of an Agency peer review body would be more appropriate. The NAS final report is currently scheduled to be completed in late 2015. Therefore, EPA will postpone any decision regarding th e phase-out of the uses of MS MA on golf courses, sod farms, and highway rights-of-way until the NAS review is complete and the Agency has analyzed and responded to the NAS report. The Agency documents discussed above can be found in the Organic Arsenicals; Amendment to Reregistra tion Eligibility Decision docket EPA-HQ-OPP2009-0191.

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 th e FIFRA standard for registration. Changes in scienc e, public policy, and pesticide us e practices occur over time. The registration review program is intended to make su re that, as the ability to assess risk evolves and as policies and practices change, al l registered pesticides continue to meet the statutory standard. The public phase of registration review begins wh en the initial docket is opened for each case. Information on this program is provided on the Agency’s website. 1

The FWP begins with any updates since the PWP wa s issued. Next is a summary of substantive comments received during the public comment peri od 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 responses to those comme nts. This section is followed by registration review planned data needs, risk assessments expected to be conducted, and the projected registration review timeline for MSMA. Las tly, there is a discu ssion of next steps.

1 http://www.epa.gov/oppsrrd1/registration_review/3 UPDATES SINCE TH E PWP WAS ISSUED

There are no additional updates on MSMA since the PWP.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60-day public comment period on the MSMA Preliminary Work Plan, which opened on March 27, 2013 and closed on May 28, 2013, the Agency received one comment from the Organic Arsenicals Product Task Force (OAPTF ), addressing several issues including the timeline described in the PWP, as well as th e planned ecological and human health risk assessments and data requirements. In the PW P, 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.

The OAPTF comment did not result in changes to th e anticipated registration review data needs, risk assessments, or timeline. Public comments and EPA responses in their entirety are located in the docket, EPA-HQ-OPP-2013-0107. Agency respons es related to the anticipated ecological
risk assessment and data needs are in the EFED Response to Public Comments on the Monosodium Methanearsonate (MSMA) Problem Formulation for Ecological Risk and Drinking Water Exposure while those relevant to the anticipated human health risk assessment and data
needs are in the HED Monosodium Methanearsonate (M SMA): Response to Comments on the Registration Review Workplan.4 PLANNED DATA NEEDS

Table 1 below summarizes the planne d data needs for MSMA based on the Registration Review: Preliminary Problem Form ulation for Monosodium Ac id Methanearsonate (MSMA) , the Monosodium Methanearsonate (MSMA): Revised Registration Review Scoping Document for Human Health Assessments, and the Response to Comments documents. The planned data needs have not changed from what was included in the PWP.

Table 1: Planned Data Needs for the MSMA Registration Review

Guideline

Number 2 Study Title 2 Test Material Estimated

Timeframe
(Months from receipt of DCI)

835.4300 Aerobic aquatic metabolism 3 TGAI or PAIRA; Methylated arsenics (V) 24

850.1300 Aquatic invertebrate life cycle (freshwater) TGAI; Methylated arsenics (V) 12

850.1350 Aquatic invertebrate life cycle (saltwater) TGAI; Methylated arsenics (V) 12

850.1500 Fish life cycle (Freshwater) TGAI; Methylated arsenics (V) 24

850.1735 Whole sediment: acute freshwater invertebrates TGAI; Methylated and inorganic arsenics (III) 24

Nonguideline Whole sediment: chronic freshwater invertebrates ( Hyalella or Chironomus ) TGAI; Methylated and inorganic arsenics (III) 24

850.2100 Avian oral toxicity (passerine) TGAI; Methylated arsenics (V) 12

850.2300 Avian reproduction TGAI; Methylated arsenics (V) 24

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 Av ailability” 77 FR 38282 , June 27, 2012. http://www.regulations.gov/#!documen tDetail;D=EPA-HQ-OPPT-2009-0154-0028

3 A study is under Agency review for the aerobic aquatic metabolism data requirement. This data requirement has not been included in a DCI previously, therefore it will be included in the Registration Review DCI.5 Table 1: Planned Data Needs for the MSMA Registration Review

Guideline

Number 2 Study Title 2 Test Material Estimated

Timeframe
(Months from receipt of DCI)

860.1500 Crop Field trials (cotton gin byproducts) 4 TEP 24

870.7800 Immunotoxicity TGAI; Methylated arsenics (V) 12

TGAI = technical grade active ingredie nt; TEP = typical end-use product;

4 The data requirement for crop field trials for cotton gin byproducts has not been included in a DCI previously; therefore it will be included in the Registration Review DCI.6 RISK ASSESSMENTS FOR REGISTRATION REVIEW

During registration review, the Agency will conduct a comprehensive ecological risk assessment, including an endangered species a ssessment, for all uses of MSMA . For human health, EPA will conduct revised dietary, resident ial, occupational, and aggreg ate risk assessments. If toxicological endpoints or points of departure are revised based on the data that are required for registration review, they will be considered in th e new assessments, as well as any changes to the standard operating procedures or default exposure assumptions.

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

Table 2: Planned Risk Assessments for the MSMA Registration Review

Type of Risk Assessment Conduct? Notes

Ecological and Environmental Fate Comprehensive ecological (species to be assessed include terrestrial and aquatic organisms), including endangered species Yes Arsenic speciation was not quantitatively considered in the Reregistration Eligibility Assessment (RED) for MSMA and DSMA, but will be considered in this updated assessment.

Incidents

Will check for updates A formal review is not pl anned, but the agency will continue to monitor incident data throughout registration review. For a discussion of MSMA’s reported ecological incidents, see page 17 of the
Problem Formulation.

Human Health Dietary

Food

Yes These assessments may be required, and would use existing data for m onomethylarsonic acid, dimethylarsinic acid, and iAs; the most updated information and policies, re vised points of departure (PoDs) or uncertainty fa ctors including any NAS Review revised cancer MoA; updated consumption information and the latest dietary exposure model; and updated estimated dri nking water concentrations (EDWC’s). Drinking water

Occupational Handlers (mixers, loaders, applicators) Yes An updated assessment may be required due to changes to the use pattern and revisions to scenario specific surrogate handler exposure data since the
assessment done for the RED.7 Table 2: Planned Risk Assessments for the MSMA Registration Review

Post-application

Yes An updated dermal assessment may be necessary. A quantitative post-applica tion inhalation exposure assessment is not required at this time; however, if new policies and procedures are put into place to incorporate volatilization of pesticides as a potential source of post-application inhalation exposure, the need for this assessment may be revisited.

Residential

Handlers

Yes A revised non-cancer asse ssment may be required that includes post-applicati on exposure to treated golf courses and will incorporate as necessary updated SOP’s, human factor a ssumptions, and currently registered use patterns. Th e need for spray drift and
volatilization assessments w ill also be evaluated. Post-application

Other Aggregate

Yes Evaluates the combined risk from dietary and residential exposures. This assessment may be required because of the potential for short-term residential post-applicati on exposure from the golf course use. Updated PoDs, uncertainty and safety factors, and drinking wate r assessment revisions and residential assessment findings will be incorporated.

Cumulative

No At this time, EPA does not have available data to
determine whether MSMA has a common mechanism of toxicity with other substances.

Tolerances

No The current tolerance expre ssion as listed in the 40 CFR § 180.289(a) will need to be revised to reflect product cancellations following the 2006 RED and subsequent agreements with the registrants. These changes are detailed in the Monosodium Methanearsonate (MSMA): Registration Review Scoping Document for Human Health Assessments.

Incidents

Will check for updates A formal review is not pl anned, but the agency will continue to monitor incident data throughout registration review. For a discussion of MSMA’s reported human incidents, see page 11 of the Scoping

Document.

TIMELINE

EPA has created the following estimated timelin e for the completion of the MSMA registration review in Table 3 below. The projected timelin e has been revised since the PWP, because it is expected that less time will be required to issue the Data Call-In (DCI).8 Table 3: Registration Review for MSMA – Projected Registration Review Timeline

Activities Estimated Date Opening the Docket Open Docket and 60-day Public Comment Period March 2013– Completed

Close Public Comment May 2013 – Completed Case Development

Final Work Plan August 2013 – Completed Issue DCI 2014 – January - March Data Submission 2016 – January - March 60-day Public Comment Period for Draft Risk Assessments 5 2017- July - September Registration Review Decision 60-day Public Comment Period fo r Proposed Registration Review
Decision 2019 – January - March

Registration Review Decision and Begin Post-Decision Follow-up 2019 Total (years) 6

NEXT STEPS

As noted previously, the Agency plans to requir e several environmental fa te, ecological effects, and human health studies for MSMA through a Data Call-In Notice, expected to be issued in January – March 2014.

5 The regulations governing Registration Review require the Agency to provide a public comment period of at least

30 calendar days for draft risk assessments; see 40 CFR Pa rt 155.53(c). The Agency pl ans to provide a 60 calendar day public comment period for draft risk assessm ents as a general standard of practice.