Mitigating China's Ozone Pollution with More Balanced Health Benefits.

China is confronting the challenge of opposite health benefits (OHBs) during ambient ozone (O 3 ) mitigation because the same reduction scheme might yield opposite impacts on O 3 levels and associated public health across different regions. Here, we used a combination of chemical transport modeling, health benefit assessments, and machine learning to capture such OHBs and optimize O 3 mitigation pathways based on 121 control scenarios. We revealed that, for the China mainland, Beijing-Tianjin-Hebei and its surroundings ("2 + 26" cities), Yangtze River Delta, and Pearl River Delta, there could be at most 2897, 920, 1247, and 896 additional O 3 -related deaths in urban areas, respectively, accompanying 21,512, 3442, 5614, and 642 avoided O 3 -related deaths in rural areas, respectively, at the same control stage. Additionally, potential disbenefits during O 3 mitigation were "pro-wealthy", that is, residents in developed regions are more likely to afford additional health risks. In order to avoid OHBs during O 3 abatement, we proposed a two-phase control strategy, whereby the reduction ratio of NO X (nitrogen oxide) to VOCs (volatile organic compounds) was adjusted according to health benefit distribution patterns. Our study provided novel insights into China's O 3 attainment and references for other countries facing the dual challenges of environmental pollution and associated inequality issues.