2

I NTRODUCTION

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

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

methyl’s registration review docket (EPA

- HQ

- OPP

- 2011

- 0844 ). Primisulfuron

- methyl is a selective post

- emer gent sulfonylurea herbicide absorbed and transported throughout the plant roots and foliage. The mechanism of action is the inhibition of amino acid synthesis in plants through inhibition of acetolactate synthase (ALS). ALS is the first common enzyme in the biosynthesis of branched

- chain amino acids (valine, leucine

, and isoleucine). ALS inhibition in plants adversely affects plant growth and reproduction. Although the sulfonylurea herbicides all act upon the same enzyme system in plants, that system is not present in humans or other mammals.

The Agency is implementing the registration review program pursuant to Section 3(g) of the Federal In secticide, 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 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 revie w 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 summary of the Agency’s response s to th o se comments

. This section is followed by primisulfuron

- methyl’s registr ation review planned data needs, risk assessments expected to be conducted , and the projected registration review timeline. Last, there is a discussion of next steps.

UPDATES SINCE THE PWP WAS ISSUED

Proposed Tolerance Revocation. On May 9, 2012, EPA p ublished a proposed rule revoking the tolerances for primisulfuron

- methyl on sweet corn (40 CFR 180.452 : corn, sweet, forage and corn, sweet, stover). See 90 FR 27164. The Agency expects to publish th e final rule revoking the primisulfuron

- methyl tolerances on sweet corn in September 2012. There are no active U

. S registrations for use of primisulfuron

- methyl on sweet corn.

Testing Requirements for Sulfonyl Urea Herbicides

. T he Agency is aware of new information suggesting that effects observed in plant r eproductive toxicity studies conducted with sulfonylurea herbicides occur at concentrations similar to those at which effects were observed in the guideline vegetative vigor studies (850.4150). The Agency is currently evaluating this information to determ ine if additional testing beyond the standard vegetative vigor studies is

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

warranted for this class of compounds, or if data from the vegetative vigor guideline study are sufficiently protective of potential impacts to plant reproduction.

SUMMARY OF COMMEN TS AND AGENCY RESPONSES

During the 60

- day public comment period on the p rimisulfu r on

- 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 the technical registrant, Syngenta Crop Protection, and by the FIFRA Endangered Species Task Force (FESTF). The comments do not address the timeline described in the PWP, but they do address the planned ecological 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.

Public comments on the p rimisulfuron

- methyl PWP and EPA responses are summarized below. A detailed summar y of public comments and EPA’s responses related to the anticipated ecological risk assessment and data needs are in the July 30, 2012 memo, The Environmental Fate and Effects Division responses to Syngenta and FESTF Comments on the Primisulfuron

methyl Pr eliminary Work Plan (PWP) for Registration Review

, located in the public docket.

Comments submitted by Syngenta Crop Protection in EPA

- HQ

- OPP

- 2011

- 0844

- 0009

.

1. C omment: The Primisulfuron

- methyl Summary Document states that this pesticide was first registered in 1991. This should be corrected to 1990.

Response: Syngenta is correct. P rimisulfuron

- methyl was first registered in March 1990

.

2. Comment: Syngenta has noticed a value of 0.0268 lb ai/A listed as the maximum application rate for corn. However, a higher value is provided on the EPA

- approved Beacon herbicide label (EPA Registration Number 100

- 705). This product has a maximum application rate of 0.0356 lb ai/A.

Response: The Agency has verified that the use rate provided by Syngenta is correct for the cited product label ( EPA Reg istration N umber 100

- 705 ) . The label spreadsheet has been revised and updated to reflect this information. The revised spreadsheet, PRD Label Data Report: Food/Feed & Non

- Food/Non

- Feed Uses Considered in the Registration Review Work Planning for Primisulfuron

- methyl

, dated June 20, 2012, is located in docket EPA

- HQ

- OPP

- 2011

- 0844

.

3. C omment: The Problem Formula tion for environmental fate and ecological risk cites a NOAEC of 0.41 mg/ai/L for a daphnia study. The original report for this study (MRID 41418609) cites the NOAEC as 0.70 mg/L but the reviewer recalculated the NO A EC to be 0.41 mg/L based on the low mea n measured test substance concentration for days 7 and 14 of the study . On these days, the pH in the exposure tanks varied from 7.5 to 8.1, thus influencing the solubility of the test substance

. Syngenta suggests that the NOAEC be calculated based on the mean measured test substance concentration for the entire exposure period, from day zero to day 21.4

Response: EPA will re

- evaluate this study to determine if the NOAEC needs to be corrected.

4. Comment: Two studies in the rat, MRIDs 00403312 and 40512009

, are not included in the citation reference section of the problem formulation document.

Response: Although these two MRIDs 2 were referenced earlier in the Problem Formulation, Syngenta is correct : EPA omitted the complete citation for these s tudies from the Problem Formulation. T hese citations will be included in future risk assessment documents. In addition, t he Agency has identified a typographical error in Table 7 on page 22 of the Problem Formulation. The MRID number for the acute oral toxicity study in rats (MRID 00403312 ) is incorrect ; the correct MRID number is 40331206. The
correct citations for these two studies are as follows:

40331206 Maedgen, J. (1986) Acute Oral Toxicity in Rats: CGA

- 136872 Tech:

Laboratory Study No. 4011

- 86. Unpublished study prepared by Stillmeadow, Inc. 13 p.

40512009 Schardein, J. (1987) Two

- generation Reproduction Study in Albino Rats with

CGA

- 136872: Laboratory Study No. 382

- 115. Unpublished study prepared by International Research and Developm ent Corporation. 604 p.

5. Comment: EPA is asking for an avian reproduction study (in both Bobwhite quail and Mallard Duck) for the degradate CGA

- 171683. Avian reproductive toxicity data (in mallards, MRID 40512004) are available for the parent compound, primisulfuron

methyl. These data for the parent compound show that no reproductive effects occurred at the highest dose tested (500 mg/kg/day). Chronic exposure of birds to a soil

concentra tion at such concentration is unlikely, and additional chronic avian data with the soil degradate would not likely change the risk conclusion for primisulfuron

- methyl.

Response: No ecological toxicity data are available for the soil degradate CGA

- 171683

, and the toxicity and risk from this degradate to terrestrial organisms are a significant area of uncertainty. CGA

- 17 1 683 is a unique sulfonyl urea degradate which is mobile and likely to be persistent in the environment ; 75% of the degradate remains in th e environment for 12 months after application of primisulfuron

- methyl

. Therefore, both acute and chronic exposures to terrestrial species may occur. T he avian reproducti on toxicity study is the only long

- term study available to evaluat e the toxicity o f this degradate in the terrestrial environment

. The value for understanding the relative toxicity of C G A

- 171 6 83 and the parent in the terrestrial environment is high; until data indicate CGA171683 i s not toxic, EPA would assume risks of concern to terrestrial animals and a

“ may effect” finding for federally list ed threatened and/or endangered species.

2 Master Record Identification Number5

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

- HQ

OPP

- 2011

- 0844

- 0010

.

1. Comment: The FIFRA Endangered Species Task Force (FESTF) s ubmitted its information management system contai ning Nature Serve Data (MRID 47260101) to fulfill the data requirements described in PR Notice 20 0 0

- 2. This submission provides the best available data for the proximity analysis of primisulfuron data use and locations of endangered species. Syngenta is a member of FESTF and is entitled to rely on the FESTF data to support primisulfuron

- methyl.

Response: The Agency thanks FESTF for its comment and data submission. EPA will consider this information as it conducts the registration review for primisulfu ron

- methyl.

PLANNED DATA NEEDS

The table below summarizes the data needs for p rimisu l furon

- methyl based on the Registration Review

- Preliminary Problem Formulation for Ecological Risk and Environmental Fate, Endangered Species, and Drinking Water Assessments for Primisulfuron methyl

, P rimisulfuron

methyl. Health Effects Division (HED) Scoping Document for Registration Review , and The Environmental Fate and Effects Division responses to Syngenta and FESTF Comments on the Primisulfuron

- methyl Prelimi nary Work Plan (PWP) for Registration Review

. The data needs have not changed from what was included in the PWP.

Planned Data Needs for Primisulfuron

- methyl ’s Registration Review

Guideline Number Study Title Test Material Estimated

Timeframe (Months from Receipt of DCI)
835.4300 Aerobic Aquatic Metabolism TGAI 24 835.4400 Anaerobic Aquatic Metabolism TGAI 24

835.6100 Terrestrial Field Dissipation (En v i ronme n tal Chemistry

Methods) 3 TGAI 24

835.6200 Aquatic Field Dissipation (Environmental Chemistry

Methods) 4 TGAI 12

850.2100 Avian Acute Oral Toxicity (passerine species) TGAI 12

850.2300 Avian Reproduction (bobwhite quail and mallard

duck) 5 Degradate 24

3 Data are currently in review for GLN 835.6100, terrestrial field dissipation. Although data have been submitted to EPA, this GLN will be considered a data gap until the data have been reviewed and found to be acceptable . An environmental chemistry analy tical method (ECM) and independent laboratory validation (ILV) are required for soil as part of this guideline.
4 See footnote 7 of 40 CFR 158.1300. The DCI will require only the environmental chemistry analytical methods and independent laboratory (ILV ) portions of this guideline, rather than the full field dissipation study.
5 The DCI will require that this study be conducted with the fluorinated degradate CGA

- 171683.6 Planned Data Needs for Primisulfuron

- methyl ’s Registration Review

Guideline Number Study Title Test Material Estimated

Timeframe (Months from Receipt of DCI)

Non

- GLN Special Study for Non

- target plant reproductive

toxicity 6 TEP 24

870.7800 Immunotoxicity Study TGAI 12
TGAI = Technical Grade Active Ingredient ; TEP = Typical End

- Use Product; D egradate = CGA

- 171683.

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 primisulfuron

- methyl

. For human health, EPA will evaluate the need to conduct revised dietary, residential

, and occupational risk
assessment s during registration review

. If toxicological endpoints or points of departure are revised based on the data that are required for registration review

, they will be considered in the
new assessment s , as well as any changes to the standard operating p rocedures or default exposure assumpti ons

.

The table below summarizes the planned registration review risk assessments based on the EFED Problem Formulation and HED Scoping Document s for primisulfuron

- methyl. The planned
assessments are unchanged from th e PWP

.

Planned Risk Assessments for Primisulfuron

- methyl’s 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 Y To date, EPA has not conducted a comprehensive ecological risk assessment supporting a complete endangered species determination for primisulfuron

methyl.

Incidents Y For a discussion of p rimisulfuron

- methyl’s reported ecological incidents, see page 9 and Appendix C of the Problem Formulation.

6 The Agency is currently evaluating new information to determ ine if the vegetative vigor guideline study is sufficiently protective of potential impacts to plant reproduction.7

Planned Risk Assessments for Primisulfuron

- methyl’s Registration Review Type of Risk Assessment Conduct? Notes Human Health Dietary Food Y EPA may need to update the drinking water assessment to include th e degradate CGA

- 171683 and will revise the dietary assessment accordingly. Drinking water Y

Occupational Handlers (mixers, loaders, applicators) N In the 2002 risk assessment, occupational handler risks were significantly below EPA’s level of concern (MOEs > 100,000). Post

- application Y EPA will evaluate potential post

- application exposure from harvesting treated sod, which was previously
not asses sed. Residential Handlers N Primisulfuron

- methyl is not registered for residential

use. Post

- application Y There are currently no registered residential uses. However, there are several S pecial L ocal N eed (SLN) registrations for use on Kentucky bluegrass for sod production. Because there are no restrictions on the transfer of treated sod to residential sites

, residential post

- application exposure might occur as a result of exposure to treated sod. EPA will evaluate potential post

- application residential/bystander exposure from treated sod. Other Aggregate Y EPA will evaluate the combined risk from d ie t ary and residential exposures. Cumulative N Primisulfuron

- methyl is not a member of a cumulative group for human health effects. Tolerances Y EPA will modify the tolerance expression to reflect current policies. In addition, EPA is revoking primisulfuron methyl tolerances on sweet corn because there are no active registrations on sweet

corn. Incidents N No human health incidents have been rep orted for primisulfuron

- methyl . See p age 7 of the Scoping Document for further details.8

TIMELINE

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

- methyl’s registration review

. The projected timeline has not changed since the PWP

.

Registration Review for Primisulfuron

- methyl

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

- day Public Comment Period March 2012

– Completed Close Public Comment May 2012

– Completed Case Development Final Work Plan Sept

. 2012

– Completed Issue DCI 2013

– April

- June Data Submission 2015

– April

- June Open 30

- day Public Comment Period for Draft Risk Assessments 2016

– Oct.

- Dec. Close Public Comment Period 2017

– Jan.

- March Registration Review Decision Open 60

- day Public Comment Period for Proposed Registration Review Decision 2017

– April

- June

Close Public Comment Period 2017

– July

- Sept. Registration Review Decision and Begin Post

- Decision Follow

- up 2018 Total (years) 6

NEXT STEPS

As noted previously, t he Agency plans to require several environmental fate, ecological effects, and human health studies for primisulfuron

- methyl through a data call

- in, expected to be issued in the spring of 2013.