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Understanding Sources and Exposures in an Airshed

Abstract:

Air pollution from ambient sources continues to adversely impact human health in the United States. A fundamental goal for EPA is to implement air quality standards and regulations that reduce health risks associated with exposures to criteria pollutants and air toxics. However, this is not an easy or straightforward task. The NRC has recommended that research should be conducted to identify those pollutants and sources that are responsible for the most significant risks in air sheds. A critical component of this research is to develop an understanding of how pollutants from sources impact ambient concentrations and, in turn, how these concentrations relate to exposures. This information provides a fundamental linkage for evaluating health impacts and developing effective mitigation strategies.

The purpose of this task is to develop a more sophisticated understanding of what is happening in an airshed by extending to exposure measurements to multiple pollutants, characterizing the spatial variability, determining the sources that contribute to human exposure. The Detroit Exposure and Aerosol Research Study (DEARS) is a study of community, residential, and personal exposures to air pollutants and their sources. The study includes a 3-year field monitoring program with two monitoring seasons per year (summer and winter) that will provide information and data for subsequent modeling and statistical analyses. The data analysis activities will include (1) interpretation of direct field measurements, (2) atmospheric and receptor modeling to understand source apportionment and spatial variability, and (3) human exposure modeling. The primary goal of the study is to evaluate and describe the relationship between air toxics, particulate matter (PM), PM constituents, and PM from specific sources measured at a central site monitor and measurements of residential and personal concentrations. An emphasis is placed on understanding the impact of local sources (point and mobile) on outdoor residential concentrations and the impact of housing type and house operation on indoor concentrations. This information will be used to identify the contribution of various pollutant sources (automotive, industrial and natural sources) at the community and neighborhood level, as well as, to personal exposures. In addition, the study will provide important data to evaluate the suitability of using community monitoring data as a surrogate for human exposures to PM components and air toxics from specific sources in epidemiological studies. Results from this study will be critical in providing exposure data for developing future air quality standards that protect public health.

Objective:

The overall goal of this task is to determine the source-receptor and spatial/temporal relationships for air pollutants measured outdoors at community monitors and in respective personal exposures. The primary objectives of the research task are:

Relevance/Significance/Impact:

This task will provide important information for future air regulations and policies that will likely shift from addressing regional issues, such as regionally transported pollutants emitted from electric utilities, to addressing local scale issues, such as concerns relating to environmental justice or near roadway exposures and health impacts. In addition, research to investigate the potential for a component- or source-based PM NAAQS is likely to include epidemiological studies that attempt to relate speciated PM measurements to health effects. Understanding exposures is essential for developing scientifically sound policies that address either local scale issues and PM component or source-based NAAQS. Furthermore, enhanced exposure assessment is also critical to respond to the NRC's recommendation to identify the pollutants and sources responsible for the most significant exposures and risks. The results from this task will enhance exposure assessments for PM and air toxics and will provide valuable information on how sources impact exposures to PM and air toxics. Specifically, results from DEARS will be used to better understand the applicability of community measurements of air toxics and PM species to represent actual human exposures in epidemiological studies. Results from this research will also inform EPA and the scientific community on approaches that can be used to evaluate health effects associated with PM constituents and PM from various sources. In addition, data collected in the DEARS will be used to develop and evaluate models to estimate exposures integrating community measurements of air pollutants and important deterministic factors such as human activity patterns and the effect of residential characteristics. Finally, the DEARS will also include source apportionment of human exposure measurements which will provide valuable information that may help in identifying effective approaches for mitigating exposures to sources that are responsible for adverse health outcomes. The overall impact of this task will be the development of a spatial and temporal model of exposure to air pollution components and sources that will be used to assess the contribution of sources and components to exposures, to determine suitability of community monitor to represent exposures to sources, and to link sources to exposure to health impact.

Principal Investigator: Ronald W. Williams

Human Exposure and Atmospheric Sciences

Research & Development | National Exposure Research Laboratory

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