Chinese emissions reductions deliver reduced PM2.5-caused mortality across China during 2015-2017

Air pollution is a serious environmental issue and leading contributor to the disease burden in China. Following severe air pollution episodes during the 2012-2013 winter, the Chinese government has prioritised efforts to reduce PM_2.5 emissions, and established a national monitoring network to record air quality trends. Rapid reductions in fine particulate matter (PM_2.5) concentrations and increased ozone concentrations have occurred across China, during 2015 to 2017. We used measurements of particulate matter with a diameter < 2.5 µm (PM_2.5) and Ozone (O₃) from >1000 stations across China combined with similar datasets from Hong Kong and Taiwan to calculate trends in PM_2.5, Nitrogen Dioxide, Sulphur Dioxide and O₃ across the greater China region during 2015-2019. We then use the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) regional air quality simulations, to explore the drivers and impacts of observed trends. Using annually varying emissions from the Multi-resolution Emission Inventory for China, we simulate air quality across China during 2015-2017, and calculate a median PM_2.5 trends of -3.9 µg m^-3 year^-1. The measured nationwide median PM_2.5 trend of -3.4 µg m^-3 year^-. With anthropogenic emissions fixed at 2015-levels, the simulated trend was much weaker (-0.6 µg m^-3 year^-1), demonstrating interannual variability in meteorology played a minor role in the observed PM_2.5 trend. The model simulated increased ozone concentrations in line with the measurements, but underestimated the magnitude of the observed absolute trend by a factor of 2. We combined simulated trends in PM_2.5 concentrations with an exposure-response function to estimate that reductions in PM_2.5 concentrations over this period have reduced PM_2.5-attribrutable premature morality across China by 150 000 deaths year^-1.