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This fourth external review draft document is an updated revision of the Air Quality Criteria for Particulate Matter, published by the United States Environmental Protection Agency (EPA) in 2001, and it will serve as the basis for reevaluating the current National Ambient Air Quality Standards (NAAQS) for particulate matter (PM) set in 1997. The present external review draft critically assesses the latest scientific information relative to determining the health and welfare effects associated with exposure to various concentrations of PM in ambient air. The document is not intended as a complete and detailed literature review, but it does thoroughly evaluate information relevant to PM NAAQS criteria development based on pertinent literature mainly available through April 2002. Two sections of the Clean Air Act (CAA), (Sections 108 and 109, U.S. Code, 1991) govern the establishment, review, and revision of NAAQS. Section 108 directs the Administrator of the EPA to list pollutants that may reasonably be anticipated to endanger public health or welfare, and to issue air quality criteria for them. The air quality criteria are to reflect the latest scientific information useful in indicating the kind and extent of all exposure-related effects on public health and welfare that may be expected from the presence of the pollutant in ambient air.

The document is divided into two volumes: Volume I (Chapters 1 through 5, EPA/600/P-99/002aD) and Volume II (Chapters 6 through 9, EPA/600/P-99/002bD). After the brief general introduction in Chapter 1, Chapters 2 and 3 provide background information on physical and chemical properties of PM and related compounds; sources and emissions; atmospheric transport; transformation and fate of PM; methods for the collection and measurement of PM; and ambient air concentrations; Chapter 4 describes PM environmental effects on vegetation and ecosystems, impacts on man-made materials and visibility, and relationships to global climate change processes; and Chapter 5 contains factors affecting exposure of the general population. Chapters 6 through 8 evaluate information concerning the health effects of PM. Chapter 6 discusses dosimetry of inhaled particles in the respiratory tract; and Chapter 7 assesses information on the toxicology of specific types of PM constituents, including laboratory animal studies and controlled human exposure studies. Chapter 8 discusses epidemiologic studies. Chapter 9 integrates key information on exposure, dosimetry, and critical health risk issues derived from studies reviewed in the prior chapters. The Executive Summary is to be incorporated in Volume I.

Additional Information

For technical questions only, contact Dennis Kotchmar.

All other questions should be directed to the contact listed above.