Short-term Exposure to Particulate Matter Constituents and Mortality in a National Study of U.S. Urban Communities

Background: Although the association between PM(2.5) mass and mortality has been extensively studied, few national-level analyses have estimated mortality effects of PM(2.5) chemical constituents. Epidemiologic studies have reported that estimated effects of PM(2.5) on mortality vary spatially and seasonally. We hypothesized that associations between PM(2.5) constituents and mortality would not vary spatially or seasonally if variation in chemical composition contributes to variation in estimated PM(2.5) mortality effects. Objectives: We aimed to provide the first national, season-specific, and region-specific associations between mortality and PM(2.5) constituents. Methods: We estimated short-term associations between nonaccidental mortality and PM(2.5) 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 PM(2.5) 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 PM(2.5) or PM(2.5) constituents differed by season or region. Conclusions: Our findings indicate that some constituents of PM(2.5) may be more toxic than others and, therefore, regulating PM total mass alone may not be sufficient to protect human health. Citation: Krall JR, Anderson GB, Dominici F, Bell ML, Peng RD. 2013. Short-term exposure to particulate matter constituents and mortality in a national study of U.S. urban communities. Environ Health Perspect 121:1148–1153; http://dx.doi.org/10.1289/ehp.1206185