Docket Number EPA-HQ-OPP- OPP-2011-0720 

www.regulations.gov 

Butralin Final Work Plan 

Registration Review: Initial Docket 

Case Number 2075 

Approved by: 

Date: 

November 2012 

~~p~~~:n 

Richard P. Keigwin, Jr. 

Director 

Pesticide Re-evaluation Division 

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2

INTRODUCTION

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

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

concerning the Preliminary Work Plan (PWP), which was posted in butralin’s registration review 

docket (EPA-HQ-OPP-2011-0720). Butralin is a dinitroaniline plant growth regulator registered 

for use only on tobacco to inhibit sucker growth; it has no food, feed, or residential uses. 

Butralin inhibits microtubule assembly needed for cell division, thereby disrupting rapid plant 

growth, such as growth of tobacco suckers that would otherwise take energy from leaf formation. 

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 website1.

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 butralin’s

registration 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

There are no updates on the butralin registration review case since the PWP was issued in July 

2012.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

EPA published the Butalin Preliminary Work Plan and initial registration review docket for a 60-

day public comment period, which opened on July 6, 2012. The Federal Register Notice 

announcing the docket opening2erroneously listed the comment period end date as August 19, 

2012. However, on July 10, 2012, EPA extended the comment period until September 10, 2012 

to allow for a full 60-day public comment period. The Agency received no public comments on 

the Butralin Preliminary Work Plan.

 

1

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

2

See 77 FR 40048; FRL-9352-1.
3

PLANNED DATA NEEDS

The following table summarizes the planned data needs for butralin based on the February 14,

2012 EFED Registration Review Problem Formulation for Butralin3and the March 12, 2012 

document, Butralin. Human Health Assessment Scoping Document in Support of Registration 

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

Planned Data Needs for Butralin Registration Review

Guideline 

Number Planned Data Requirements Test Material

Study 

Duration

Environmental Fate and Effects

835.1240 Adsorption/Desorption TGAI 12

835.4100 Aerobic Soil Metabolism TGAI 24

835.4300 Aerobic Aquatic Metabolism TGAI 24

835.4400 Anaerobic Aquatic Metabolism TGAI 24

850.61001

Environmental Chemistry Methods (ECM) and 

Independent Laboratory Validation (ILV) in soil

and water

TGAI 12

850.1350 Chronic Estuarine Invertebrate TGAI 12

850.1400 Fish Early Life-stage (freshwater and saltwater) TGAI 12

850.2100 Avian acute (passerine species)2TGAI 12

850.3020 Acute contact toxicity, Honey bee TGAI 12

Non-guideline Acute oral toxicity, Honey bee2TGAI 12

Non-guideline

Whole Sediment Chronic Toxicity Invertebrates, 

Chirononomus dilutus2,3 TGAI 12

Non-guideline

Whole Sediment Chronic Toxicity Invertebrates, 

Hyallella azteca2,3 TGAI 12

Human Health Effects 

870.6200 Acute and Sub-chronic Neurotoxicity TGAI 24

870.7800 Immunotoxicity TGAI 12

Outstanding Data Requirement under GDCI-106501-17782 

850.4150 Vegetative vigor4 TEP 12

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

1On 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

2The data call-in (DCI) will provide that a study protocol must be submitted for review (within 90 days of receipt of 

the DCI) and approval by the Agency prior to initiation of the study.

3 Acute sediment toxicity studies were inadvertently listed in the Preliminary Work Plan (PWP). This was a 

typographical error. Chronic studies are needed, as indicated on page 4 of the PWP.

4 EPA is currently reviewing a submitted study (MRID 44431002).

 

3 This document contains a January 5, 2012 Tier I Drinking Water Assessment for Butralin Supporting Registration

Review Problem Formulation.
4

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 butralin. For human health, EPA will

conduct a limited assessment to evaluate inhalation exposure and risks to those who smoke from 

butralin residues in tobacco. If toxicological endpoints or points of departure are revised based 

on the data that are required for registration review, the Agency will consider the need to update 

the entire human health assessment. 

The table 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 described in the PWP.

Planned Risk Assessments for Butralin’s Registration Review

Type of Risk Assessment Conduct?

Yes/No Notes

Ecological and Environmental Fate

Comprehensive ecological (species 

to be assessed include terrestrial 

and aquatic organisms), including 

endangered species 

Yes The planned ecological risk assessment will support a 

complete endangered species determination for 

butralin. 

Incident Monitoring Yes For a discussion of butralin’s reported ecological 

incidents, see page 12 of the Problem Formulation.

Human Health

Dietary

Food No Butralin is not used on food or feed commodities. 

Drinking water No EPA does not expect significant dietary exposure to 

butralin residues in drinking water4.

Occupational

Handlers (mixers, loaders, 

applicators)

No EPA will rely on previous assessments, which 

resulted in risk estimates that were not of concern 

Post-application No

Residential

Handlers No Butralin is not registered for residential use.

Post-application No

Inhalation (smokers) Yes EPA will evaluate potential short-term inhalation 

exposure and risk for people who smoke tobacco and 

may be exposed to butralin residues in tobacco. 

Residential/bystander Yes EPA may evaluate potential off-target movement of 

butralin into residential settings.

 

4

See the Tier I Drinking Water Assessment in the EFED Problem Formulation
5

Type of Risk Assessment Conduct? 

Yes/No Notes

Other

Aggregate No There is no dietary exposure from food and no 

significant exposure from drinking water.

Cumulative No EPA has not made a common mechanism of toxicity 

finding for butralin and any other substances.

Furthermore, butralin does not appear to produce a 

toxic metabolite produced by other substances. 

Tolerances No No established US tolerances or Codex, Canadian, or 

Mexican MRLs.

Incidents Yes For a discussion of butralin’s reported human 

incidents, see page 6 of the Scoping Document.

TIMELINE

EPA has created the following estimated timeline for the completion of butralin’s registration

review. Although the registration review docket opening was delayed from June 2012 to July 

2012 for butralin, the overall registration review timeline has not changed from the PWP. 

Registration Review Timeline for Butralin

Activities Estimated Date

Opening the Docket

Open Docket and Public Comment Period 2012 – July

Close Public Comment 2012 – September

Case Development

Final Work Plan 2012 – November

Issue DCI 2013 – July – Sept.

Data Submission 2015 – July – Sept.

Open Public Comment Period for Draft Risk Assessments 2017 – Jan. – March

Close Public Comment Period 2017 – April – June

Registration Review Decision

Open Public Comment Period for Proposed Registration Review 

Decision

2017 – July – Sept.

Close Public Comment Period 2017 – Oct. – Dec.

Registration Review Decision and Begin Post-Decision Follow-up 2018

Total (years) 6

NEXT STEPS

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

and human health studies for butralin through a data call-in, expected to be issued in 2013.