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INTRODUCTION

This is the Environmental Protection Agency’s (EPA or the Agency) Final Work Plan (FWP) for 

the registration review of ametryn. This work plan addresses public comments received 

concerning the Preliminary Work Plan (PWP), which was posted in the ametryn registration 

review docket (EPA-HQ-OPP-2013-0249). Ametryn is a triazine herbicide used for selective 

control of broadleaf and grassy weeds in corn, pineapple, and sugarcane. There are no nonagricultural or residential uses registered. 

 

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 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 review begins when 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 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 responses to those comments. This section is followed by registration 

review planned data needs, risk assessments expected to be conducted, and the projected 

registration review timeline for ametryn. Lastly, there is a discussion of next steps. 

UPDATES SINCE THE PWP WAS ISSUED

The case number for ametryn was inaccurately listed as # 7036 in the PWP. The FWP reflects 

the correct case number for ametryn, which is # 2010. 

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60-day public comment period on the ametryn Preliminary Work Plan, which opened 

on June 26, 2013, and closed on August 26, 2013, the Agency received four sets of public 

comments. The comments were submitted by the technical registrant for ametryn, Syngenta 

Crop Protection, LLC (Syngenta); the FIFRA Endangered Species Task Force (FESTF); a 

citizen; and the South Dakota Corn Growers Association. The comments do not address the 

timeline identified in the PWP, but do address data needs and the planned ecological registration 

review risk assessment. Syngenta submitted one comment on the data requirements identified in 

the PWP, indicating it would submit a waiver for Guideline 870.7800 (Immunotoxicity). EPA 

will consider a request for a waiver when it is submitted; however, a request has yet to be 

submitted and therefore Guideline 870.7800 remains a data requirement to support registration 

review. Syngenta also submitted a comment regarding the planned endangered species 

assessment, which is addressed in the Response to Public Comments on the Registration Review 

 

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 http://www.epa.gov/oppsrrd1/registration_review/ 
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– Preliminary Problem Formulation for Ecological Risk and Environmental Fate, Endangered 

Species, and Drinking Water Assessments for Ametryn.

The comments did not result in a change to the planned data requirements or registration review 

work plan described in the PWP. 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. 

Summarized below are substantive public comments that concerned the anticipated registration 

review data needs or are of a broader regulatory nature. Public comments and EPA responses in 

their entirety are located in the docket, EPA-HQ-OPP-2013-0249. 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 Registration Review – Preliminary 

Problem Formulation for Ecological Risk and Environmental Fate, Endangered Species, and 

Drinking Water Assessments for Ametryn. This section does not address every comment 

received. 

Comments submitted by Mark Gross, President and Lisa Richardson, Executive Director, 

South Dakota Corn Growers Association in EPA-HQ-OPP-2013-0249-0010. 

1. Comment: Ametryn can be applied to corn safely and is most often applied post-directly, 

under a crop’s canopy. It fills a specific need for growers and without it, farmers’ options would 

be limited.

 Response: EPA will consider this comment during registration review. 

Comments submitted by FESTF in EPA-HQ-OPP-2013-0249-0011. 

2. Comment: The technical registrant for ametryn, as identified on the fact sheet included in 

the PWP, is Sygnenta, which is a FESTF member and is entitled to rely on FESTF data. 

 Response: EPA will consider this comment during registration review. 

Comments submitted by Syngenta in EPA-HQ-OPP-2013-0249-0012. 

3. Comment: On page 6 of the PWP and on page 2 of the BEAD Chemical Profile (BCP), EPA 

states that, “Ametryn can be applied as a pre-emergence and as a post-emergence directed 

spray.” Syngenta requests that the PWP and the BCP be revised to state that ametryn can be 

applied as “a post-emergence directed spray (corn) and broadcast spray (sugarcane).” 

 Response: The statement in the PWP and BCP is correct and will not be revised. The intent 

of the sentence was to discuss, in general terms, the different application methods of ametryn. 

Individual product labels provide details on how the product must be used on specific crops. 

4. Comment: Syngenta requests that it be allowed to conduct Guideline 850.4500 (Algal 

Toxicity) and 850.4550 (Cyanobacteria Toxicity) with technical grade active ingredient (TGAI) 

rather than typical end use product (TEP). 
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 Response: Either TEP or TGAI can be used as the test substance in the conduct of Guideline 

850.4500 (Algal Toxicity) and 850.4550 (Cyanobacteria Toxicity). 

5. Comment: In the Acute, Subchronic, and Chronic Toxicity Profile table on page 17 of the 

Ametryn: Human Health Risk Scoping Document in Support of Registration Review, the skin 

sensitization toxicity category is left blank. Syngenta requests that the Scoping Document be 

revised to include “N/A” for the skin sensization toxicity category. 

 Response: EPA acknowledges that because ametryn is not a skin sensitizer, the skin 

sensitization category on page 17 of the Scoping Document for ametryn is not applicable. 

Because the Scoping Document does not indicate that ametryn is a skin sensitizer and the 

inclusion of “N/A” would be an editorial rather than substantive change, the Scoping Document 

will not be revised. 

6. Comment: Syngenta respectfully submits a crop matrix for ametryn.

 Response: EPA thanks Syngenta for the detailed crop use information. EPA will consider 

this information prior to the conduct of the human health and ecological preliminary risk 

assessments to be conducted in support of registration review. 

PLANNED DATA NEEDS

Table 1 below summarizes the planned data needs for ametryn based on the Preliminary 

Problem Formulation for Environmental Fate, Ecological Risk, Endangered Species, and

Human Health Drinking Water Exposure Assessments for Ametryn and Ametryn: Human Health 

Risk Scoping Document in Support of Registration Review. The planned data needs have not 

changed from what was included in the PWP; however, as a result of a comment received, the 

test substances in the table below have been modified to indicate that either TEP or TGAI can be 

used as the test substance in producing data for Guideline 850.4500 (Algal Toxicity) and 

850.4550 (Cyanobacteria Toxicity). 

Table 1: Planned Data Needs for the Ametryn Registration Review 

Guideline 

Number1,2 Study Title1 Test Material 

Estimated 

Timeframe 

(Months from 

receipt of DCI) 

835.2240 Photodegradation in water TGAI 12 

835.4100 Aerobic soil metabolism TGAI 24 

835.4300 Aerobic aquatic metabolism TGAI 24 

850.4500 Algal toxicity TEP or TGAI 12 

850.4550 Cyanobacteria toxicity TEP or TGAI 12 

870.3465 90-day inhalation3 TGAI 24 

870.7800 Immunotoxicity4 TGAI 12 

TGAI = technical grade active ingredient; TEP = typical end-use product 
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 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 Availability” 77 FR 38282, June 27, 2012. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0154-0028 2 As noted in the PWP, Page 31 of the Problem Formulation incorrectly indicates environmental chemistry methods 

(ECM) and associated independent laboratory validation (ILV) for water (Guideline 850.6100) are needed for 

ametryn. Acceptable ECM and ILVs for soil, sediment, and water have been submitted for ametryn, and therefore, 

EPA does not plan to require Guideline 850.6100. 

3 A 28-day inhalation toxicity study will be sufficient. Therefore, the study duration can be reduced from 90 days to 

28 days. 

4 Recently, OPP published the findings of its retrospective analysis of immunotoxicity studies submitted to the 

Agency, concluding that none of the studies included in the analysis resulted in a Point of Departure (POD) that is 

lower than the PODs selected from other available guideline toxicology studies 

(http://www.epa.gov/pesticides/regulating/immunotoxicity-retro-analysis.pdf). EPA will consider requests for 

waivers for this study, particularly in light of the retrospective analysis. A weight-of-evidence rationale will be 

considered relative to the chemical’s toxicological profile, primary target organ system(s) and mode of toxic action, 

and any immuno-related data available from structurally-related compounds. 

RISK ASSESSMENTS FOR REGISTRATION REVIEW

During registration review, the Agency will conduct a comprehensive ecological risk assessment, 

including an endangered species assessment, for all uses of ametryn. For human health, EPA 

will conduct revised dietary and occupational risk assessments during registration review. If 

toxicological endpoints or points of departure are revised, they will be considered in the new 

assessments, as well as any changes to the standard operating procedures or default exposure 

assumptions. 

Table 2 below summarizes the planned registration 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 Ametryn 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 Parent ametryn will be considered the stressor of 

concern for the terrestrial exposure assessment. For 

the aquatic exposure assessment, in the absence of 

data on the toxicity of degradates NOA 428383 and 

NOA 423271, these degradates and the parent 

ametryn will be considered the stressors of concern 

using the total toxic residue (TTR) approach. For 

additional information, see page 25 of the Problem 

Formulation. 

Incidents Will check for 

updates 

No ecological incidents reported for ametryn; see 

page 24 of the Problem Formulation. 
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Table 2: Planned Risk Assessments for the Ametryn Registration Review 

Type of Risk Assessment Conduct? Notes 

Human Health 

Dietary 

Food Y EPA will update the dietary assessment during 

registration review to take into account any new 

toxicity or exposure data, changes to safety factors, or 

changes in standard risk assessment operating 

procedures. 

Drinking water N 

Occupational 

Handlers (mixers, loaders, 

applicators) 

Y EPA will update the occupational assessment during 

registration review to take into account any new 

toxicity or exposure data, changes to safety factors, or 

changes in standard risk assessment operating 

procedures. 

Post-application Y 

Residential 

Handlers N Ametryn is not registered for residential use, 

registered uses are not anticipated to result in 

residential exposure, and therefore, a residential risk 

assessment is not required. 

Post-application N 

Other 

Aggregate Y Evaluates the combined risk from dietary and 

residential exposures. Since there are no residential 

uses, EPA will update the aggregate assessment to 

take into account any changes to dietary risk estimates 

only. 

Cumulative N Ametryn has not been identified as a member of a 

cumulative group that shares a common mechanism 

of toxicity. 

 

Tolerances Y Tolerances for ametryn are established under 40 CFR 

§180.258. EPA will update the residue definition for 

the tolerance expression for ametryn in accordance 

with current policy on tolerance definitions. 

Incidents Will check for 

updates 

For a discussion of reported human incidents for 

ametryn, see page 10 of the Scoping Document and 

the Ametryn: Review of Human Incident Reports. 

TIMELINE

EPA has created the following estimated timeline for the completion of the ametryn registration 

review in Table 3 below. The projected timeline has not changed since the PWP. 

  
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Table 3: Projected Ametryn Registration Review Timeline

Activities Estimated Date

Opening the Docket 

Open Docket and 60-day Public Comment Period 2013 – June 

Close Public Comment 2013 – August 

Case Development 

Final Work Plan 2013 – December 

Issue DCI 2014 July - September 

Data Submission 2016 July - September 

60-day Public Comment Period for Draft Risk 

Assessments1

2018 January – March 

Registration Review Decision 

60-day Public Comment Period for Proposed 

Registration Review Decision 

2018 July – September 

Registration Review Decision and Begin Post-Decision 

Follow-up 

2019 

Total (years) 6 1

 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 Part 155.53(c). The Agency plans to provide a 60 calendar 

day public comment period for draft risk assessments as a general standard of practice. 

NEXT STEPS

As noted previously, the Agency plans to require several environmental fate, ecological effects, 

and human health studies for ametryn through a Data Call-In Notice, expected to be issued by 

September 2014.