Drivers of Ozone-related Premature Mortality in China: Implications for Historical and Future Scenarios

Long-term exposure to ambient ozone (O) poses a severe public health threat in China. However, the drivers of premature mortality caused by O pollution are still poorly constrained, despite being prerequisites for addressing the threat. Here, we demonstrate the contributions of historical and future changes in peak-season O, population size, age structure, and baseline mortality to China's O-related mortality using decomposition analysis. From 2013 to 2021, O-related mortality decreased dramatically from 78.8 (40.8-124.6) to 68.7 (36.0-107.2) thousand, especially in densely populated areas with high pollution. Variations in peak-season O, population size, age structure, and baseline mortality led to changes in O-related mortality of +27.3 (14.8-41.3), +2.6 (1.4-4.1), +22.3 (11.5-35.2), and -40.3 (20.9-63.7) thousand, respectively. The influence of peak-season O on O-related mortality shifted from positive during 2013-2019 (+8.4% per year) to negative during 2019-2021 (-8.8% per year), which highly regulated the interannual trend of mortality. From 2021 to 2035, O-related mortality is expected to increase by 31% in the current context of peak-season O levels, primarily caused by increased aging. Even reducing peak-season O to the WHO interim target 1 (IT-1) would only reduce O-related mortality by 3.9%, while a more rigorous standard (IT-2) would prevent 83.7% of mortality. These findings suggest that improving ambient O can lead to significant health benefits, but substantial mitigation strategies are merited given the future trend of population aging.