| The Effects of Components of Fine Particulate Air Pollution on Mortality in California: Results from CALFINE Bart Ostro,1 Wen-Ying Feng,2 Rachel Broadwin,1 Shelley Green,1 and Michael Lipsett3 1California Office of Environmental Health Hazard Assessment, Oakland, California, USA; 2Graduate Group in Biostatistics, University of California, Davis, California, USA; 3Department of Epidemiology and Biostatistics, University of California, San Francisco, California, USA Abstract
Objective: Several epidemiologic studies provide evidence of an association between daily mortality and particulate matter < 2.5 µm in diameter (PM2.5) . Little is known, however, about the relative effects of PM2.5 constituents. We examined associations between 19 PM2.5 components and daily mortality in six California counties. Design: We obtained daily data from 2000 to 2003 on mortality and PM2.5 mass and components, including elemental and organic carbon (EC and OC) , nitrates, sulfates, and various metals. We examined associations of PM2.5 and its constituents with daily counts of several mortality categories: all-cause, cardiovascular, respiratory, and mortality age > 65 years. Poisson regressions incorporating natural splines were used to control for time-varying covariates. Effect estimates were determined for each component in each county and then combined using a random-effects model. Results: PM2.5 mass and several constituents were associated with multiple mortality categories, especially cardiovascular deaths. For example, for a 3-day lag, the latter increased by 1.6, 2.1, 1.6, and 1.5% for PM2.5, EC, OC, and nitrates based on interquartile ranges of 14.6, 0.8, 4.6, and 5.5 µg/m3, respectively. Stronger associations were observed between mortality and additional pollutants, including sulfates and several metals, during the cool season. Conclusion: This multicounty analysis adds to the growing body of evidence linking PM2.5 with mortality and indicates that excess risks may vary among specific PM2.5 components. Therefore, the use of regression coefficients based on PM2.5 mass may underestimate associations with some PM2.5 components. Also, our findings support the hypothesis that combustion-associated pollutants are particularly important in California. Key words: EC, fine particles, mortality, nitrates, OC, particulate matter, PM2.5, species. Environ Health Perspect 14:13–19 (2007) . doi:10.1289/ehp.9281 available via http://dx.doi.org/ [Online 29 August 2006]
Address correspondence to B. Ostro, California Office of Environmental Health Hazard Assessment, 16th Floor, 1515 Clay St., Oakland, CA 94612 USA. Telephone: (510) 622-3157. Fax: (510) 622-3210. E-mail: Bostro@oehha.ca.gov Supplemental Material is available online at http://www.ehponline.org/docs/2006/9281/suppl.pdf We thank the anonymous reviewers for their helpful comments, J. Kim, and B. Malig for his editorial assistance. The opinions expressed in this article are solely those of the authors and do not represent the policy or position of the State of California or the California Environmental Protection Agency. The authors declare they have no competing financial interests. Received 21 April 2006 ; accepted 29 August 2006.
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