Docket Number: EPA-HQ-OPP-2008-0842 

www.regulations.gov

Methamidophos 

Proposed Registration Review Decision 

February 2010 

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TABLE OF CONTENTS 

I. INTRODUCTION........................................................................................4

II. BACKGROUND INFORMATION ...........................................................4 

III. PROPOSED REGISTRATION REVIEW DECISION ...........................5 

IV. NEXT STEPS AND TIMELINE................................................................6
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I. INTRODUCTION 

This document is the Environmental Protection Agency’s (EPA or the Agency) 

Proposed Registration Review Decision for methamidophos and is being issued pursuant 

to 40 CFR § 155.57 and § 155.58. A registration review decision is the Agency’s 

determination whether a pesticide meets, or does not meet, the standard for registration in 

the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). 

 FIFRA, as amended by the Food Quality Protection Act (FQPA) of 1996, 

mandated the continuous review of existing pesticides. All pesticides distributed or sold 

in the United States must generally be registered by EPA, based on scientific data 

showing that they will not cause unreasonable risks to human health or the environment 

when used as directed on product labeling. 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 of no 

unreasonable adverse effects to human health or the environment. Through the 

registration review program, the Agency periodically reevaluates pesticides to make sure 

that as change occurs, products in the marketplace can be safely used. Information on 

this program is provided at: http://www.epa.gov/oppsrrd1/registration_review/. 

In 2006, the Agency implemented the Registration Review program pursuant to 

FIFRA Section 3(g), and will review each registered pesticide every 15 years to 

determine whether it continues to meet the FIFRA standard for registration. 

 Pursuant to 40 CFR § 155.50, the Agency formally initiated registration review 

for methamidophos (case 0043). The following timeline highlights significant events that 

have occurred during the registration review of methamidophos: 

• December 17, 2008 – Publication of the Methamidophos Summary Document, 

Scoping Document, and Problem Formulation Document in the docket (EPA-HQOPP-2008-0842) for a 90-day public comment period. The Summary Document

also included the preliminary work plan. 

• May 13, 2009 – Publication of the methamidophos Final Work Plan. 

• July 22, 2009 – Publication of a Notice of Receipt of Requests to Voluntarily 

Cancel Certain Pesticide Registrations for methamidophos in the Federal 

Register. No comments were received during a 30-day comment period. 

• September 23, 2009 – Publication of a Product Cancellation Order for 

methamidophos in the Federal Register. 

II. BACKGROUND INFORMATION 

Methamidophos is a restricted use organophosphate insecticide, which in 2009 

was registered for use on potato, cotton, tomato, and alfalfa grown for seed. 

Methamidophos was the subject of a July 2002 Interim Reregistration Eligibility 

Decision (IRED), and in July 2006, the Reregistration Eligibility Decision (RED) for 
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methamidophos was finalized upon completion of the Organophosphate (OP) Cumulative 

Risk Assessment. The Methamidophos RED is the Agency’s most recent comprehensive 

assessment of the human health, and ecological risk of methamidophos use. 

Additionally, in July 2007, EPA completed an endangered species assessment that 

evaluated the California red-legged frog’s exposure to methamidophos. 

On May 20, 2009, pursuant to a voluntary request by Bayer CropScience, EPA published 

an order in the Federal Register to terminate all methamidophos use on cotton as of 

September 30, 2009. Existing stocks for use on cotton may be sold and distributed by 

persons other than the registrant until July 31, 2010. Existing stocks labeled for use on 

cotton may be used until September 30, 2011, provided that such use complies with the 

EPA-approved labels and labeling of the products. 

 In 2009, the sole methamidophos registrant, Bayer CropScience, informed the 

Agency that they were requesting to voluntarily cancel all of their remaining 

methamidophos product registrations. Following publication of a Federal Register notice 

announcing receipt of those requests and the completion of the corresponding public 

comment period, the Agency issued the product cancellation order on September 23, 

2009 for all methamidophos product registrations (copies of those notices are included in 

the docket for this registration review). All methamidophos product cancellations 

became effective on December 31, 2009. Existing stocks provisions included in the order 

allowed Bayer CropScience to sell and distribute methamidophos products, excluding 

products cancelled by the cotton use termination referred to above, until December 31, 

2010. Persons other than the registrant may continue to sell, distribute, and use these 

methamidophos products until exhausted, provided that such sale, distribution, and use is 

consistent with the terms of the previously approved labeling on, or that accompanied, 

the canceled products. 

III. PROPOSED REGISTRATION REVIEW DECISION 

As stated in the Preliminary Work Plan for methamidophos, the Agency had 

intended to revise the existing risk assessments for methamidophos. However, due to the 

cancellation order issued affecting all methamidophos product registrations in the United 

States, the Agency has found that it is not necessary to conduct new risk assessments for 

methamidophos and is, therefore, issuing a proposed decision pursuant to 40 CFR Part 

155.53(c)(2) and 40 CFR Part 155.58. The voluntary cancellation of all U.S. 

methamidophos registrations has occurred prior to the previously planned completion 

dates for the revised methamidophos risk assessments. The effective date of cancellation 

for methamidophos products registered for use in the U.S. was December 31, 2009. The 

Registration Review Timeline introduced in the methamidophos Preliminary Work Plan 

proposed that the Agency would complete the revised risk assessments by December 

2013 and issue a decision in 2015. 

The Agency does not expect the current risks associated with methamidophos use 

to differ from those identified during the methamidophos reregistration process. In order 

to mitigate the risks identified in the RED, the Agency specified mitigation measures in 
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the RED, which are already in effect on methamidophos product labels. The existing 

stocks sales and distribution deadlines included in the September 23, 2009 cancellation 

order ensure that methamidophos sale, distribution, and use will decline and then cease 

entirely in the United States in the future. During this period, given the mitigation 

measures that are specified in the RED and are currently in place, the Agency believes 

that existing stocks of methamidophos products may be used until depleted without 

causing unreasonable risk to human health and the environment. Pursuant to 40 CFR § 

155.57 and 155.58, the Agency proposes that the registration review decision be issued, 

thus concluding the methamidophos registration review, for the reasons discussed above. 

The affected product registrations are subject to the terms and conditions of the 

September 23, 2009 cancellation order. 

IV. NEXT STEPS AND TIMELINE 

Pursuant to 40 CFR § 155.58, this proposed registration review decision 

document is being entered into the methamidophos docket (EPA-HQ-OPP-2008-0842). 

A Federal Register notice will announce the availability of this proposed registration 

review decision for methamidophos and allow a 60-day comment period. If there are no 

significant comments or additional information submitted to the docket during the 

comment period that leads the Agency to change its decision, EPA will issue a 

registration review decision for methamidophos, Case 0043, which will be announced in 

the Federal Register. The Agency anticipates that a decision will be issued in 2010. In 

addition, the Agency will propose to revoke all tolerances resulting from methamidophos 

use in a timeframe that will allow for the exhaustion of existing stocks.