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Final NAFTA Guidance for Conducting Terrestrial Field Dissipation Studies

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Information about this document as published in the Federal Register.

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This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

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Environmental Protection Agency (EPA).




Under the North American Free Trade Agreement (NAFTA), EPA and the Canadian Pest Management Regulatory Agency (PMRA) have agreed to harmonize their testing guidelines so that one set of tests can be used for the registration of pesticides in Canada and the United States. The NAFTA harmonized guidance for terrestrial field dissipation (TFD) studies are conducted to demonstrate the transformation, transport, and fate of pesticides under representative actual use conditions. These field studies are needed to substantiate the physicochemical, mobility, and biotransformation data from laboratory studies. Environmental fate studies have shown that pesticide dissipation may proceed at different rates under field conditions and may result in degradates forming at levels different from those observed in laboratory studies. The objective of this guidance document is to help ensure that TFD studies are conducted in a manner that will provide risk assessors and risk managers with more confidence in the data generated and with a better understanding of the assumptions and limitations of the data and estimated half-lives of the pesticide. The proposed guidance document for TFD studies was published in the Federal Register on June 15, 2005 (FRL-7713-7). After reviewing the public comments for this Notice, EPA developed a final guidance document, which can be found at:​oppefed1/​ecorisk_​ders/​terrestrial_​field_​dissipation_​guidance.pdf. EPA's response to public comments can be found in the public docket: EPA-HQ-OPP-2005-0129.

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Mark Corbin, Environmental Fate and Effects Division (7507P), Office of Pesticide Programs, Environmental Protection Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460-0001; telephone number: (703) 605-0033; fax number: (703) 305-6309; e-mail address:

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I. General Information

A. Does this Action Apply to Me?

 You may be potentially affected by this action if you are an agricultural producer, food manufacturer, or pesticide manufacturer. Potentially affected entities may include, but are not limited to:

  • Crop production (NAICS code 111)
  • Animal production (NAICS code 112)
  • Food manufacturing (NAICS code 311)
  • Pesticide manufacturing (NAICS code 32532)

-This listing is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be affected by this action. Other types of entities not listed in this unit could also be affected. The North American Industrial Classification System (NAICS) codes have been provided to assist you and others in determining whether this action might apply to certain entities. If you have any questions regarding the applicability of this action to a particular entity, consult the person listed under FOR FURTHER INFORMATION CONTACT.

B. How Can I Get Copies of this Document and Other Related Information?

-1. Docket. EPA has established a docket for this action under docket identification (ID) number EPA-HQ-OPP-2005-0129. Publicly available docket materials are available either in the electronic docket at, or, if only available in hard copy, at the Office of Pesticide Programs (OPP) Regulatory Public Docket in Rm. S-4400, One Potomac Yard (South Building), 2777 S. Crystal Drive, Arlington, VA. The hours of operation of this Docket Facility are from 8:30 a.m. to 4 p.m., Monday through Friday, excluding legal holidays. The Docket telephone number is (703) 305-5805.

-2. Electronic access. You may access this Federal Register document electronically through the EPA Internet under the “Federal Register” listings at​fedrgstr.

II. Background

A. What Action is the Agency Taking?

The Terrestrial Field Dissipation study has been a basic requirement for registrants of new and existing pesticides since 1982. While laboratory environmental fate studies are designed to address one dissipation process at a time, terrestrial field dissipation studies address pesticide loss as a combined result of chemical and biological processes (e.g., hydrolysis, photolysis, microbial transformation) and physical migration (e.g., volatilization, leaching, plant uptake). Data from these studies can reduce potential overestimation of exposure and risk and can confirm assumptions of low levels of toxic degradates. Results can be used to propose scenario-specific effective risk mitigation.

In general, the terrestrial field dissipation study results should allow the risk assessor to:

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  • Compare predicted routes of dissipation identified in the laboratory with those measured in the field;
  • Characterize the rates of dissipation of the parent compound and formation and decline of the major and/or toxicologically significant transformation products under field conditions;
  • Characterize the rates and relative importance of the different transport processes, including leaching, runoff, and volatilization;
  • Establish the distribution of the parent compound and the major transformation products in the soil profile;
  • Characterize the persistence of the parent compound and major transformation products in soil, including retention and residue carryover in the soil to the following crop season; and
  • Characterize the effect(s) of different typical pesticide formulation categories, where applicable.

-EPA and PMRA have developed harmonized guidance for conducting terrestrial field dissipation studies so that one set of tests can be used for registration of a pesticide in Canada, the United States, and Mexico. In developing this guidance document, EPA and PMRA conducted an extensive outreach and review program, soliciting input from stakeholders and the technical community through several forums: Three symposia, one Scientific Advisory Panel (SAP) meeting, and one workshop. Working closely with its stakeholders, PMRA and EPA developed a conceptual model for designing terrestrial studies that will evaluate the overall dissipation of a pesticide in the field. The conceptual model, which is specific for each pesticide, is based on the chemical's physicochemical properties, laboratory environmental fate studies, formulation type and intended use pattern. On June 15, 2005, the Agency published the draft harmonized guidance and conceptual model in the Federal Register and asked for comments. After reviewing all the comments, PMRA and EPA developed the final guidance, which can be found at the following address:​oppefed1/​ecorisk_​ders/​terrestrial_​field_​dissipation_​guidance.pdf.

B. What is the Agency's Authority for Taking this Action?

This action is being taken under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).

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Dated: August 3, 2006.

Steven Bradbury,

Director, Environmental Fate and Effects Division, Office of Pesticide Programs.

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FR Doc. E6-13042 Filed 8-10-06; 8:45 am]