The Denver Aerosol Sources and Health (DASH) study began in mid-2004 with the objective to identify the sources of ambient air pollution that contribute to the health effects of short-term exposure to fine particulate matter (PM2.5). Interim analysis using PM2.5 chemical composition data based on an ongoing intensive monitoring and chemical speciation effort that has been underway since mid-2002 indicated that traffic-associated emissions, in particular diesel emissions as reflected by elemental carbon (EC), was more strongly associated with increased daily total and cardio-respiratory mortality than either total PM2.5 mass or other PM components. Preliminary analyses performed in preparing the original study application suggested that daily concentrations of a limited number of PM components were reasonably spatially homogenous in Denver. Since the study began, new information for other US cities (Atlanta, New York City and St. Louis) calls this impression into question with the finding that some PM component and source concentrations appear spatially heterogeneous. The main motivation for requesting supplemental funding for the last year of the DASH study is to gather information to determine whether the use of a single residential (population-oriented) monitoring site as currently used adequately reflects short-term temporal variability in PM components and sources over space in the Denver metropolitan area. The extent of this spatial-temporal variability will affect the interpretation of PM component and source health effect estimates currently being generated by the DASH health studies. To address this, we propose one year of supplemental PM component monitoring in areas selected to reflect spatial variation in PM components that correspond to large portions of the Denver population. This information will be used to examine spatial variability in source contributions in Denver and to estimate effects of this variability on health effects estimates. Supplemental funding is also requested to continue our collection of PM data at the one population-oriented site to allow use of an uninterrupted, long time series of daily PM components and sources in future health studies. Finally, funding is requested to incorporate additional readily accessible health endpoints, specifically hospitalization data that overcome limitations of Medicare data as well as birth outcomes data. Addition of these endpoints will more fully exploit the existing rich PM component data and daily source apportionment. This supplement to the original DASH study is intended to allow the original study findings, when available, to be best interpreted, and to allow better use of the unique data being collected. The resultant improved understanding of the role of emission sources in determining health impacts of air pollution will translate into more effective policies to control these impacts.
While our understanding of the full impact of exposure to outdoor air pollution on human health continues to grow, we know little about which sources of pollution emissions are most harmful.
The aim of this study is to identify emission sources that contribute most to health effects of exposure to air pollution. A focus on air pollution sources will allow public health policies aimed at reducing the health burden of air pollution to be more effective and efficient. ? ? ? ?
