Fine particulate matter constituents and cause-specific mortality in China: A nationwide modelling study

Background: Fine particulate matter (with aerodynamic diameter <= 2.5 mu m PM2.5 ) causes huge disease burden worldwide. However, evidence is still inadequate and inconsistent on the relationships between PM2.5 constituents and mortality, especially in low resource settings. Objectives: To evaluate the impact of PM2.5 constituents on cause-specific mortality in China. Methods: We obtained daily mortality data for 161 communities in 2011-2013 from the Disease Surveillance Point system in China. Daily concentrations of major PM2.5 constituents, including organic carbon (OC), elemental carbon (EC), sulphate (SO42-), nitrate (NO3-) and ammonium (NH4+), were estimated by using the modified Community Multiscale Air Quality model. For each community, we applied quasi-Poisson regression and polynomial distributed lag models to estimate the effects of PM2.5 constituents on cause-specific mortality. Then, the pooled effect estimates were calculated by a random-effect meta-analysis based on the restricted maximum likelihood estimation. Stratification analyses were performed by region, gender, age group and education level to identify the vulnerable populations. Results: Each interquartile range change of EC, OC, SO42-, NO3- and NH4+ at lag 0-3 day was associated with increments in non-accidental mortality of 0.45% (95%CI: 0.21, 0.69), 1.43% (0.97, 1.89), 0.71% (0.28, 1.15), 0.70% (0.10, 1.30) and 0.95% (0.39, 1.51), respectively. The associations were stronger for the deaths from cardiovascular disease and myocardial infarction, the elderly, illiterates, and people living in the South region. Conclusions: Our findings suggest positive associations between PM2.5 constituents and cause-specific mortality, particularly for myocardial infarction.