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

China is confronting the challenge of opposite health benefits (OHBs) during ambient ozone (O) mitigation because the same reduction scheme might yield opposite impacts on O 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 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-related deaths in urban areas, respectively, accompanying 21,512, 3442, 5614, and 642 avoided O-related deaths in rural areas, respectively, at the same control stage. Additionally, potential disbenefits during O 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 abatement, we proposed a two-phase control strategy, whereby the reduction ratio of NO (nitrogen oxide) to VOCs (volatile organic compounds) was adjusted according to health benefit distribution patterns. Our study provided novel insights into China's O attainment and references for other countries facing the dual challenges of environmental pollution and associated inequality issues.