title: Impact of covariate models on the assessment of the air pollution-mortality association in a single- and multipollutant context.
abstract: With the advent of multicity studies, uniform statistical approaches have been developed to examine air pollution-mortality associations across cities. To assess the sensitivity of the air pollution-mortality association to different model specifications in a single and multipollutant context, the authors applied various regression models developed in previous multicity time-series studies of air pollution and mortality to data from Philadelphia, Pennsylvania (May 1992-September 1995). Single-pollutant analyses used daily cardiovascular mortality, fine particulate matter (particles with an aerodynamic diameter ≤2.5 µm; PM(2.5)), speciated PM(2.5), and gaseous pollutant data, while multipollutant analyses used source factors identified through principal component analysis. In single-pollutant analyses, risk estimates were relatively consistent across models for most PM(2.5) components and gaseous pollutants. However, risk estimates were inconsistent for ozone in all-year and warm-season analyses. Principal component analysis yielded factors with species associated with traffic, crustal material, residual oil, and coal. Risk estimates for these factors exhibited less sensitivity to alternative regression models compared with single-pollutant models. Factors associated with traffic and crustal material showed consistently positive associations in the warm season, while the coal combustion factor showed consistently positive associations in the cold season. Overall, mortality risk estimates examined using a source-oriented approach yielded more stable and precise risk estimates, compared with single-pollutant analyses.
authors.affiliation: National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, Mailcode B-243-01, Research Triangle Park, NC 27711, USA. sacks.jason@epamail.epa.gov
authors.forename: Jason D
authors.initials: JD
authors.lastname: Sacks
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ito
authors.forename: William E
authors.initials: WE
authors.lastname: Wilson
authors.forename: Lucas M
authors.initials: LM
authors.lastname: Neas
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects* / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D002318:Cardiovascular Diseases / Q000209:etiology / Q000401:mortality*; D003627:Data Interpretation, Statistical; D004781:Environmental Exposure / Q000009:adverse effects* / Q000032:analysis; D006801:Humans; D015233:Models, Statistical; D052638:Particulate Matter / Q000009:adverse effects* / Q000032:analysis / Q000737:chemistry; D015143:Philadelphia; D025341:Principal Component Analysis; D012044:Regression Analysis; D012307:Risk Factors; D012621:Seasons
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter