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THE WORKSHOP ON THE SOURCE APPORTIONMENT OF PM HEALTH EFFECTS: INTER-COMPARISON OF RESULTS AND IMPLICATIONS
Citation:
NEAS, L. M., G. D. THURSTON, T. MAR, D. J. EATOUGH, E. J. KIM, R. LALL, L. HAO, J. P. PINTO, H. H. SUH, K. ITO, W. F. CHRISTENSEN, R. C. HENRY, F. LADEN, T. V. LARSON, M. STOLZEL, AND P. K. HOPKE. THE WORKSHOP ON THE SOURCE APPORTIONMENT OF PM HEALTH EFFECTS: INTER-COMPARISON OF RESULTS AND IMPLICATIONS. ENVIRONMENTAL HEALTH PERSPECTIVES. National Institute of Environmental Health Sciences (NIEHS), Research Triangle Park, NC, 113(12):1768-1774, (2005).
Impact/Purpose:
To examine the relationship between the particle types/sources of fine particulate matter and human mortality
Description:
While the association between exposure to ambient fine particulate matter mass (PM2.5) and human mortality is well established, the most responsible particle types/sources are not yet certain. In May 2003, the U.S. Environmental Protection Agency's Particulate Matter Centers Program sponsored the "Workshop on the Source Apportionment of PM Health Effects". The goal was to evaluate the consistency of the various source apportionment methods in assessing source contributions to daily PM2.5 mass-mortality associations. Seven research institutions, using varying methods, participated in the estimation of source apportionments of PM2.5 mass samples collected in Washington, DC and Phoenix, AZ. Apportionments were evaluated for their respective associations with mortality using Poisson regressions, allowing a comparative assessment of the extent to which variations in the apportionments contributed to variability in the source-specific mortality results. The various research groups generally identified the same major source types, each with similar elemental make-ups. Inter-group correlation analyses indicated that soil, sulfate, residual oil, and salt-associated mass were most unambiguously identified by various methods, while vegetative burning and traffic were less consistent. Aggregate source-specific mortality relative risk (RR) estimate confidence intervals overlapped each other, but the sulfate-related PM2.5 component was most consistently significant across analyses in these cities. Analyses found source types to be a significant predictor of RR, while apportionment group differences were not. Variations in the source apportionments added only some 15% to the mortality regression uncertainties. These results provide supportive evidence that existing PM2.5 source apportionment methods can be used to derive reliable insights into the source components that contribute to PM2.5-health effects.