Co-benefits of China's climate policy for air quality and human health in China and transboundary regions in 2030

Climate policies targeting CO2 emissions from fossil fuels can simultaneously reduce emissions of air pollutants and their precursors, thus mitigating air pollution and associated health impacts. Previous work has examined co-benefits of climate policy from reducing PM2.5 in rapidly-developing countries such as China, but have not examined co-benefits from ozone and its transboundary impact for both PM2.5 and ozone. Here, we compare the air quality and health co-benefits of China's climate policy on both PM2.5 and ozone in China to their co-benefits in three downwind and populous countries (South Korea, Japan and the United States) using a coupled modeling framework. In a policy scenario consistent with China's pledge to peak CO2 emissions in approximately 2030, avoided premature deaths from ozone reductions are 54 300 (95% confidence interval: 37 100-71 000) in China in 2030, nearly 60% of those fromPM2.5. Total avoided premature deaths in South Korea, Japan, and the US are 1200 (900-1600), 3500 (2800-4300), and 1900 (1400-2500), respectively. Total avoided deaths in South Korea and Japan are dominated by reductions in PM2.5-related mortality, but ozone plays a more important role in the US. Similar to co-benefits for PM2.5 in China, co-benefits of China's policy for ozone and for both pollutants in those downwind countries also rise with increasing policy stringency.