Associations of long-term exposure to fine particulate matter and its constituents with cardiovascular mortality: A prospective cohort study in China

Background: Few studies have evaluated long-term cardiovascular effects of fine particulate matter (PM2.5) and its constituents in countries with high air pollution levels. We aimed to investigate the associations of long-term exposure to PM2.5 and constituents with cardiovascular mortality in China. Methods: We conducted a prospective cohort study of 90,672 adults >= 18 years from 2010 to 2017 in 161 districts/counties across China. The residential annual-average exposure to PM2.5 and 6 main components from 2011 to 2017 were estimated by satellite-based and chemical transport models. Associations of PM2.5 and constituents with cardiovascular mortality were analyzed by competing-risk Cox proportional hazards regression. Results: The average PM2.5 exposure throughout the whole period was 46 +/- 22 mu g/m(3). The hazard ratios of mortality (95% confidence intervals) per 10 mu g/m(3) increase in PM2.5 concentrations were 1.02 (1.00, 1.05) for overall cardiovascular disease, 1.05 (1.01, 1.09) for ischemic heart disease, 1.03 (1.00, 1.06) for overall stroke, 0.99 (0.94, 1.04) for hemorrhagic stroke, and 1.11 (1.04, 1.19) for ischemic stroke. PM2.5 constituents from fossil fuel combustion (i.e., black carbon, organic matter, nitrate, ammonium, and sulfate) showed larger hazard ratios than PM2.5 total mass, while soil dust showed no risks. Conclusions: This nationwide cohort study demonstrated associations of long-term exposure to PM2.5 and its constituents with increased risks of cardiovascular mortality in the general population of China. Our study highlighted the importance of PM2.5 constituents from fossil fuel combustion in the long-term cardiovascular effects of PM2.5 in China.