title: Workgroup report: workshop on source apportionment of particulate matter health effects--intercomparison of results and implications.
abstract: Although the association between exposure to ambient fine particulate matter with aerodynamic diameter < 2.5 microm (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, Arizona, USA. 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 makeups. Intergroup correlation analyses indicated that soil-, sulfate-, residual oil-, and salt-associated mass were most unambiguously identified by various methods, whereas 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 indicated that source types were a significant predictor of RR, whereas 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.
authors.affiliation: Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo Park, New York 10987, USA. thurston@env.med.nyu.edu
authors.forename: George D
authors.initials: GD
authors.lastname: Thurston
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ito
authors.forename: Therese
authors.initials: T
authors.lastname: Mar
authors.forename: William F
authors.initials: WF
authors.lastname: Christensen
authors.forename: Delbert J
authors.initials: DJ
authors.lastname: Eatough
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Henry
authors.forename: Eugene
authors.initials: E
authors.lastname: Kim
authors.forename: Francine
authors.initials: F
authors.lastname: Laden
authors.forename: Ramona
authors.initials: R
authors.lastname: Lall
authors.forename: Timothy V
authors.initials: TV
authors.lastname: Larson
authors.forename: Hao
authors.initials: H
authors.lastname: Liu
authors.forename: Lucas
authors.initials: L
authors.lastname: Neas
authors.forename: Joseph
authors.initials: J
authors.lastname: Pinto
authors.forename: Matthias
authors.initials: M
authors.lastname: Stölzel
authors.forename: Helen
authors.initials: H
authors.lastname: Suh
authors.forename: Philip K
authors.initials: PK
authors.lastname: Hopke
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D004781:Environmental Exposure; D009026:Mortality; D010316:Particle Size; D012044:Regression Analysis; D018570:Risk Assessment; D014481:United States; D014484:United States Environmental Protection Agency
chemical_list: D000393:Air Pollutants