| Association of Fine Particulate Matter from Different Sources with Daily Mortality in Six U.S. Cities Francine Laden,1 Lucas M Neas,2 Douglas W Dockery,1,3 and Joel Schwartz1,3 1Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
2Epidemiology and Biomarkers Branch, Human Studies Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
3Environmental Epidemiology Program, Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA Abstract
Previously we reported that fine particle mass (particulate matter  2.5 µm ; PM2.5) , which is primarily from combustion sources, but not coarse particle mass, which is primarily from crustal sources, was associated with daily mortality in six eastern U.S. cities (1) . In this study, we used the elemental composition of size-fractionated particles to identify several distinct source-related fractions of fine particles and examined the association of these fractions with daily mortality in each of the six cities. Using specific rotation factor analysis for each city, we identified a silicon factor classified as soil and crustal material, a lead factor classified as motor vehicle exhaust, a selenium factor representing coal combustion, and up to two additional factors. We extracted daily counts of deaths from National Center for Health Statistics records and estimated city-specific associations of mortality with each source factor by Poisson regression, adjusting for time trends, weather, and the other source factors. Combined effect estimates were calculated as the inverse variance weighted mean of the city-specific estimates. In the combined analysis, a 10 µg/m3 increase in PM2.5 from mobile sources accounted for a 3.4% increase in daily mortality [95% confidence interval (CI) , 1.7-5.2%], and the equivalent increase in fine particles from coal combustion sources accounted for a 1.1% increase [CI, 0.3-2.0%) . PM2.5 crustal particles were not associated with daily mortality. These results indicate that combustion particles in the fine fraction from mobile and coal combustion sources, but not fine crustal particles, are associated with increased mortality. Key words: air pollution, coal combustion, fine particles, mobile sources, mortality, PM2.5, source apportionment. Environ Health Perspect 108:941-947 (2000) . [Online 29 August 2000] http://ehpnet1.niehs.nih.gov/docs/2000/108p941-947laden/ abstract.html Address correspondence to F. Laden, Channing Laboratory, 181 Longwood Avenue, Boston, MA 02115 USA. Telephone: (617) 525-2711. Fax: (617) 731-1541. E-mail: francine.laden@channing.harvard.edu We thank D. Sredl and A. Heff for their expert assistance with the analysis. Supported by U.S. EPA grant R826245-01 and National Institute of Environmental Health Sciences grant ES-000002. F. Laden was supported in part by a National Institute of Health National Research Service Award T32HL07427. The views expressed in this article are those of the individual authors and do not necessarily reflect the views and policies of the U.S. EPA. The research described in this article has been subject to U.S. EPA peer and administrative review and it has been approved for publication. Received 6 January 2000 ; accepted 30 May 2000.
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