Tracking PM 2.5 and O 3 Pollution and the Related Health Burden in China 2013-2020.

Based on the exposure data sets from the Tracking Air Pollution in China (TAP, http://tapdata.org.cn/ ), we characterized the spatiotemporal variations in PM 2.5 and O 3 exposures and quantified the long- and short-term exposure related premature deaths during 2013-2020 with respect to the two-stage clean air actions (2013-2017 and 2018-2020). We find a 48% decrease in national PM 2.5 exposure during 2013-2020, although the decrease rate has slowed after 2017. At the same time, O 3 pollution worsened, with the average April-September O 3 exposure increased by 17%. The improved air quality led to 308 thousand and 16 thousand avoided long- and short-term exposure related deaths, respectively, in 2020 compared to the 2013 level, which was majorly attributed to the reduction in ambient PM 2.5 concentration. It is also noticed that with smaller PM 2.5 reduction, the avoided long-term exposure associated deaths in 2017-2020 (13%) was greater than that in 2013-2017 (9%), because the exposure-response curve is nonlinear. As a result of the efforts in reducing PM 2.5 -polluted days with the daily average PM 2.5 higher than 75 μg/m 3 and the considerable increase in O 3 -polluted days with the daily maximum 8 h average O 3 higher than 160 μg/m 3 , deaths attributable to the short-term O 3 exposure were greater than those due to PM 2.5 exposure since 2018. Future air quality improvement strategies for the coordinated control of PM 2.5 and O 3 are urgently needed.