title: Short-term exposure to particulate matter constituents and mortality in a national study of U.S. urban communities.
abstract: BACKGROUND
  Although the association between PM2.5 mass and mortality has been extensively studied, few national-level analyses have estimated mortality effects of PM2.5 chemical constituents. Epidemiologic studies have reported that estimated effects of PM2.5 on mortality vary spatially and seasonally. We hypothesized that associations between PM2.5 constituents and mortality would not vary spatially or seasonally if variation in chemical composition contributes to variation in estimated PM2.5 mortality effects.
  
  
  OBJECTIVE
  We aimed to provide the first national, season-specific, and region-specific associations between mortality and PM2.5 constituents.
  
  
  METHODS
  We estimated short-term associations between nonaccidental mortality and PM2.5 constituents across 72 urban U.S. communities from 2000 to 2005. Using U.S. Environmental Protection Agency (EPA) Chemical Speciation Network data, we analyzed seven constituents that together compose 79-85% of PM2.5 mass: organic carbon matter (OCM), elemental carbon (EC), silicon, sodium ion, nitrate, ammonium, and sulfate. We applied Poisson time-series regression models, controlling for time and weather, to estimate mortality effects.
  
  
  RESULTS
  Interquartile range increases in OCM, EC, silicon, and sodium ion were associated with estimated increases in mortality of 0.39% [95% posterior interval (PI): 0.08, 0.70%], 0.22% (95% PI: 0.00, 0.44), 0.17% (95% PI: 0.03, 0.30), and 0.16% (95% PI: 0.00, 0.32), respectively, based on single-pollutant models. We did not find evidence that associations between mortality and PM2.5 or PM2.5 constituents differed by season or region.
  
  
  CONCLUSIONS
  Our findings indicate that some constituents of PM2.5 may be more toxic than others and, therefore, regulating PM total mass alone may not be sufficient to protect human health.
authors.affiliation: Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Jenna R
authors.initials: JR
authors.lastname: Krall
authors.forename: G Brooke
authors.initials: GB
authors.lastname: Anderson
authors.forename: Francesca
authors.initials: F
authors.lastname: Dominici
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Bell
authors.forename: Roger D
authors.initials: RD
authors.lastname: Peng
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D004784:Environmental Monitoring; D006801:Humans; D009026:Mortality; D052638:Particulate Matter / Q000032:analysis* / Q000737:chemistry; D012044:Regression Analysis; D012621:Seasons; D014481:United States; D014505:Urban Population
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter
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