Tracking long-term population exposure risks to PM2.5 and ozone in urban agglomerations of China 2015-2021

China has experienced severe air pollution in the past decade, especially PM2.5 and emerging ozone pollution recently. In this study, we comprehensively analyzed long-term population exposure risks to PM2.5 and ozone in urban agglomerations of China during 2015-2021 regarding two-stage clean-air actions based on the Ministry of Ecology and the Environment (MEE) air monitoring network. Overall, the ratio of the population living in the regions exceeding the Chinese National Ambient Air Quality Standard (35 mu g/m(3)) decreases by 29.9 % for PM2.5 from 2015 to 2021, driven by high proportions in the Middle Plain (MP, 42.3 %) and Lan-Xi (35.0 %) regions. However, this ratio almost remains unchanged for ozone and even increases by 1.5 % in the MP region. As expected, the improved air quality leads to 234.7 x 10(3) avoided premature mortality (Delta Mort), mainly ascribed to the reduction in PM2.5 concentration. COVID-19 pandemic may influence the annual variation of PM2.5-related Delta Mort as it affects the shape of the population exposure curve to become much steeper. Although all eleven urban agglomerations share stroke (43.6 %) and ischaemic heart disease (IHD, 30.1 %) as the two largest contributors to total Delta Mort, cause-specific Delta Mort is highly regional heterogeneous, in which ozonerelated Delta Mort is significantly higher (21%) in the Tibet region than other urban agglomeration. Despite ozone-related Delta Mort being one order of magnitude lower than PM2.5-related Delta Mort from 2015 to 2021, ozone-related Delta Mort is predicted to increase in major urban agglomerations initially along with a continuous decline for PM2.5-related Delta Mort from 2020 to 2060, highlighting the importance of ozone control. Coordinated controls of PM(2.)5 and O-3 are warranted for reducing health burdens in China during achieving carbon neutrality.