Fine particulate matter constituents and cardiopulmonary mortality in a heavily polluted Chinese city

Background: Although ambient fine particulate matter (PM_2.5; particulate matter ≤ 2.5 µm in aerodynamic diameter) has been linked to adverse human health effects, the chemical constituents that cause harm are unknown. To our knowledge, the health effects of PM_2.5 constituents have not been reported for a developing country.Objectives: We examined the short-term association between PM_2.5 constituents and daily mortality in Xi’an, a heavily polluted Chinese city.Methods: We obtained daily mortality data and daily concentrations of PM_2.5, organic carbon (OC), elemental carbon (EC), and 10 water-soluble ions for 1 January 2004 through 31 December 2008. We also measured concentrations of fifteen elements 1 January 2006 through 31 December 2008. We analyzed the data using over-dispersed generalized linear Poisson models.Results: During the study period, the mean daily average concentration of PM_2.5 in Xi’an was 182.2 µg/m³. Major contributors to PM_2.5 mass included OC, EC, sulfate, nitrate, and ammonium. After adjustment for PM_2.5 mass, we found significant positive associations of total, cardiovascular, or respiratory mortality with OC, EC, ammonium, nitrate, chlorine ion, chlorine, and nickel for at least 1 lag day. Nitrate demonstrated stronger associations with total and cardiovascular mortality than PM_2.5 mass. For a 1-day lag, interquartile range increases in PM_2.5 mass and nitrate (114.9 and 15.4 µg/m³, respectively) were associated with 1.8% [95% confidence interval (CI): 0.8%, 2.8%] and 3.8% (95% CI: 1.7%, 5.9%) increases in total mortality.Conclusions: Our findings suggest that PM_2.5 constituents from the combustion of fossil fuel may have an appreciable influence on the health effects attributable to PM_2.5 in Xi’an.