Differentiating the effects of ambient fine and coarse particles on mortality from cardiopulmonary diseases: A nationwide multicity study

Background: Both inhalable particles (PM10) and fine particles (PM2.5) are regulated in various countries mainly due to their adverse health effects. However, there is increasing evidence that PM2.5 might be responsible for these effects and coarse particles (PMc) plays little role in adverse health effects, if so, it might be not necessary to monitor PM10. Methods: In this study, we conducted a time-series analysis using a generalized additive model to explore the effects of PM2.5, PMc, and PM10 on mortality from ischemic heart disease (IHD) and chronic obstructive pulmonary disease (COPD) in 96 Chinese cities during 2013-2016. The mortality number and attributable fraction were further estimated using the national air quality standard and WHO's guideline as the reference. Results: We observed significant effects of PM2.5 on IHD and COPD mortality; each 10 ug/m3 increase in lag01 PM2.5 was associated with a 0.26% (95% CI: 0.17%, 0.34%) increase in IHD mortality and a 0.19% (95% CI: 0.09%, 0.29%) increase in COPD mortality. We also found significant effects of PMc and PM10 on mortality from IHD and COPD, but the magnitudes of effects were weaker than those of PM2.5. The results were robust when adjusting for co-pollutants and altering model parameters. We further estimated that about 1.27% (95% CI: 0.29%, 2.30%) of IHD mortality and 1.25% (95% CI: 0.08%, 2.46%) of COPD mortality could be attributable to PM2.5 exposure using WHO's guideline (25 ug/m(3)) as a reference, corresponding to 15,337 (95% CI: 3,375, 27,842) mortalities from IHD and 5,653 (95% CI: 379, 11,152) COPD mortalities in the 96 cities. Across all of China, almost fifty thousand cases of IHD mortality and twenty thousand cases of COPD mortality might be avoidable if the PM2.5 concentration declined to the WHO guideline. Conclusions: Our study indicates that short-term exposure to PM2.5 could be an important risk factor of mortality from IHD and COPD, and substantial cardiopulmonary mortality could be avoidable by reducing daily PM2.5 concentrations. It is nonnegligible to consider the role of PMc in triggering in cardiopulmonary mortality. And it could be necessary to continue monitoring PM10 in the study regions due to the adverse effects of PMc.