Impact/Purpose:

The objectives for NERL's PM research program are directly linked to developing methods, data, and models that characterize and predict human exposure to PM of ambient origin and will improve the scientific foundation for risk assessments of PM in future reevaluations of the NAAQS. Specific objectives in accord with the research priorities established by the NRC are to:

- determine the quantitative relationships between concentrations of particulate-matter and gaseous copollutants measured at stationary outdoor air-monitoring sites, and the contributions of these concentrations to actual personal exposures, especially for potentially susceptible subpopulations and individuals (NRC research area 1: Outdoor Measures Verses Actual Human Exposure).

- determine the exposures to biologically important constituents and specific characteristics of particulate-matter that cause responses in potentially susceptible subpopulations and the general population (NRC research area 2: Exposure to Toxic PM Constituents)

- determine the linkages between emission sources and ambient concentrations of the biologically important components of particulate matter (NRC Research Topic 4: (Revised): Air-Quality-Model Development and Testing).

- determine the physicochemical characteristics of particulate matter that elicit adverse health effects and what subpopulations are at increased risk of adverse health outcomes from particulate matter (NRC research areas 5 and 8: Assessment of Hazardous PM Components and Topic 8: Susceptible Subpopulations).

- develop and facilitate the availability, operation, and adequate performance of ambient air monitoring methods for PM to determine attainment status and, where necessary, to develop appropriate abatement strategy (This area of research was referred to as "Technical Support" in the NRC 1999 report).

Description:

In July 1997, the EPA Administrator issued new Particulate Matter (PM) National Ambient Air Quality Standards (NAAQS) that added PM2.5 (PM less than 2.5 micrometers in size). The new standard was developed largely on the basis of epidemiological studies that found relatively consistent but poorly understood associations between ambient PM concentrations and various adverse health effects. Because PM is a complex mixture of chemically diverse materials, there are important questions about the physical and chemical properties of the particles that are causing the adverse health effects, the sources of particles with these physical and chemical properties, and the actual human exposure to these particles and copollutants such as sulfur dioxide, carbon monoxide, ozone, and nitrogen dioxide, which may also influence effects.

In 1998, Congress directed the EPA Administrator to arrange for an independent study by the National Research Council (NRC) to identify the most important research priorities and to develop a conceptual plan for PM research that would answer the most important scientific questions related to the new PM2.5 NAAQS. A report was issued, Research Priorities for Airborne Particulate Matter I: Immediate Priorities and a Long-range Research Portfolio followed by an update in 1999, Research Priorities of Airborne Particulate Matter; II. Evaluating Research Progress and Updating the Portfolio. The NERL PM research program has been structured to addresses many of the NRC's highest priority research activities, particularly research to determine and model exposures to human subpopulations at the greatest risk of harm from the most hazardous components of PM.
The implementation of NAAQS for PM also requires a number of research efforts to determine compliance and develop strategic control strategies for cost-effective implementation of the NAAQS requirements. Reference monitors and procedures are being developed to determine compliance. The concentration, chemical composition, and size distribution of airborne PM are controlled by numerous atmospheric processes and research is being conducted to help understand these factors. Results of this research are then utilized by air quality models to address current and projected atmospheric loading of PM of varying size distributions, composition, and chemistry across varying spatial and temporal scales.
(Keywords: PM, Particulate Matter, Source Apportionment, Monitoring, Methods, Personal Exposure, Modeling)

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