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Mediation Analysis and the Human Health Effects of Improved Air Quality Trends
Citation:
Peterson, G., A. Corrigan, C. Hogrefe, R. Mathur, L. Neas, AND A. Rappold. Mediation Analysis and the Human Health Effects of Improved Air Quality Trends. The International Environmetrics Society (TIES) 2018 Annual Conference, Guanajuato, Guanajuato, MEXICO, July 16 - 21, 2018.
Impact/Purpose:
This abstract makes a modest contribution to the growing body of scientific knowledge on the adverse effect of particulate matter and the benefits of recent improvements in air quality on mortality in a nationwide US study.
Description:
Background: In the United States, cardiovascular mortality rates have declined along with improvements in air quality. Between 1990 and 2010, cardiovascular mortality decreased by 45.66% (standard error SE=0.02%) while fine particulate matter (PM2.5) exposures decreased by 29.5% (SE=0.2%). We investigate the extent to which reductions in cardiovascular mortality rates can be attributed to reductions in PM2.5. Methods: We obtained cardiovascular standardized mortality rates (SMR) for 2132 counties from the US National Center for Health Statistics between 1990 and 2010. We use the Community Multiscale Air Quality model to calculate population-weighted annual average PM2.5 concentrations for each county. We adapt mediation analysis to calculate the temporal trends in PM-related cardiovascular mortality rates, and consider both a fixed and random effects model to account for spatial confounding. We examine which PM components and their emission sources contribute most to PM2.5-related mortality. Results: Between 1990 and 2010, cardiovascular SMR related to total PM2.5 decreased by 12.3 (SE=0.4) deaths per 100,000 person-years, approximately 6.5% (SE=0.2%) of the overall decrease in cardiovascular SMR. Reduction in particulate sulfate levels, driven by reductions in sulfur dioxide emissions, mediated 10.8 (SE=0.6) cardiovascular SMR. Per unit mass of emissions, reduction in elemental carbon is most efficient at 1.20 (SE=0.10) cardiovascular SMR per metric kiloton. Emissions of elemental carbon from mobile vehicles have significantly decreased, while emissions from wildland fires and other area sources have increased. Conclusions: Particulate sulfates contribute the most to total PM2.5-related cardiovascular mortality, but reductions in carbon was more efficient at reducing PM2.5-related cardiovascular mortality. Disclaimer: Statements in this abstract do not necessarily reflect the views or policies of the U.S. EPA.