Impact of Heavy PM 2.5 Pollution Events on Mortality in 250 Chinese Counties.

We explored the impact of heavy PM 2.5 pollution events on the health of residents in 250 counties in China. A time-series approach involving a two-stage analysis was applied to estimate the association between heavy PM 2.5 pollution events and mortality from 2013 to 2018. The associations between heavy (PM 2.5 ≥75 μg/m 3 and <150 μg/m 3 ) and extremely heavy (PM 2.5 ≥150 μg/m 3 ) PM 2.5 pollution days with mortality were explored. The added effects of the heavy PM 2.5 pollution events were evaluated by controlling PM 2.5 concentration in the model. From 2013 to 2018, there were 57,279 county days of heavy PM 2.5 pollution and 21,248 county days of extremely heavy PM 2.5 pollution. The risks of mortality during this period of heavy PM 2.5 pollution events increased by 1.22% (95% CI: 0.82-1.63%), 1.14% (95% CI: 0.74-1.53%), 1.09% (95% CI: 0.58-1.60%), and 1.30% (95% CI: 0.40-2.20%), for all-cause, nonaccidental, circulatory, and respiratory mortality, respectively. We also observed that heavy PM 2.5 pollution events had an added effect on mortality risk associated with all-cause, nonaccidental, circulatory, and respiratory mortality, evident from an observed increase by 0.77% (95% CI: 0.29-1.24%), 0.73% (95% CI: 0.27-1.19%), 0.96% (95% CI: 0.37-1.55%), and 0.55% (95% CI: -0.52-1.63%), respectively. Heavy PM 2.5 pollution events increased mortality risks and caused an independent added effect. The findings serve as a foundation for policymakers in developing early warning systems and policy interventions.