[Federal Register Volume 69, Number 4 (Wednesday, January 7, 2004)]
[Notices]
[Page 920]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-321]


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ENVIRONMENTAL PROTECTION AGENCY

[FRL-7607-8]


Developing Relative Potency Factors for Pesticide Mixtures: 
Biostatistical Analyses of Joint Dose-Response

AGENCY: Environmental Protection Agency.

ACTION: Notice of availability.

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SUMMARY: This notice announces the availability of a final report 
titled, ``Developing Relative Potency Factors for Pesticide Mixtures: 
Biostatistical Analyses of Joint Dose-Response (EPA/600/R-03-052F),'' 
which was prepared by the U.S. Environmental Protection Agency's (EPA) 
National Center for Environmental Assessment (NCEA) of the Office of 
Research and Development (ORD).

DATES: This document will be available on or about January 7, 2004.

ADDRESSES: The document will be made available electronically through 
the NCEA Web site (www.epa.gov/ncea). A limited number of paper copies 
will be available from the EPA's National Service Center for 
Environmental Publications (NSCEP), P.O. Box 42419, Cincinnati, OH 
45242; telephone: 1-800-490-9198 or 513-489-8190; facsimile: 513-489-
8695. Please provide your name, your mailing address, the title and the 
EPA number of the requested publication.

FOR FURTHER INFORMATION CONTACT: The Technical Information Staff, 
National Center for Environmental Assessment/Cincinnati Office (MS-
117), U.S. Environmental Protection Agency, 26 W. Martin Luther King 
Drive, Cincinnati, OH 45268. Telephone: 513-569-7257; fax: 513-569-
7475; e-mail: [email protected].

SUPPLEMENTARY INFORMATION: In 1996, the Food Quality Protection Act and 
the Safe Drinking Water Act Amendments were passed, each requiring the 
EPA to consider the risk assessment of chemical mixtures. This report 
responds to the need for risk assessment research on pesticide mixtures 
and on chemicals of concern in drinking water. The Relative Potency 
Factor (RPF) approach is a general methodology for applying dose 
addition to mixtures of chemicals that produce toxicity by the same 
toxic mode of action. The current report develops biological concepts 
and statistical procedures for improving applications of the RPF 
approach, advancing the theoretical basis for RPF-based risk 
assessments. New quantitative methods that extend the application of 
RPFs are shown, addressing the important question of how to assess a 
mixture containing some chemicals that share a common toxic mode of 
action and other chemicals that do not. This research was undertaken to 
continue exploring and developing mixture risk assessment strategies 
beyond current applications and is intended to enrich the available 
library of mixture risk assessment methods for future applications of 
RPF-based risk assessments. This report provides a new set of methods 
to handle groups of chemicals with more than one toxic mode of action 
represented. Dose-response modeling techniques are shown, and two 
algorithms are provided for grouping chemicals into mode of action 
subclasses that can be modeled with a common slope parameter. The 
report details approaches to estimate health risks based on the mode of 
action subclasses and shows a conceptual approach for estimating a 
Reference Dose for a mixture using these methods.

    Dated: December 23, 2003.
Peter W. Preuss,
Director, National Center for Environmental Assessment.
[FR Doc. 04-321 Filed 1-6-04; 8:45 am]
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