Chronic fine and coarse particulate exposure, mortality, and coronary heart disease in the Nurses' Health Study

BACKGROUND: The relationship of fine particulate matter < 2.5 μm in diameter (PM_2.5) air pollution with mortality and cardiovascular disease is well established, with more recent long-term studies reporting larger effect sizes than earlier long-term studies. Some studies have suggested the coarse fraction, particles between 2.5 and 10 μm (PM_10-2.5), may also be important. With respect to mortality and cardiovascular events, questions remain regarding the relative strength of effect sizes for chronic exposure to fine and coarse particles. OBJECTIVES: We examined the relationship of chronic PM_2.5 and PM_10-2.5 exposures with all-cause mortality and fatal and nonfatal incident coronary heart disease (CHD), adjusting for time-varying covariates. METHODS: The current study included women from the Nurses' Health Study living in metropolitan areas of the northeastern and midwestern United States. Follow-up was from 1992 to 2002. We used geographic information systems-based spatial smoothing models to estimate monthly exposures at each participant's residence. RESULTS: We found increased risk of all-cause mortality [hazard ratio (HR), 1.26; 95% confidence interval (CI), 1.02-1.54] and fatal CHD (HR = 2.02; 95% CI, 1.07-3.78) associated with each 10-μg/m³ increase in annual PM_2.5 exposure. The association between fatal CHD and PM_10-2.5 was weaker. CONCLUSIONS: Our findings contribute to growing evidence that chronic PM_2.5 exposure is associated with risk of all-cause and cardiovascular mortality.