Air pollution prevention and control action plan substantially reduced PM_2.5 concentration in China

As part of China's committed efforts to alleviate and control air pollution in key regions, the Air Pollution Prevention and Control Action Plan (APPCAP) was implemented in 2013 and a series of regulatory measures, including a mandatory and strengthened enterprise air pollutant emission standard was rolled out. However, the present literature has focused limited attention to the actual effects of APPCAP on PM_2.5 pollution treatment. Using panel data from 271 prefecture-level cities covering 2008 and 2018, this paper used the difference-in-differences (DID) and propensity score matching difference-in-differences (PSM DID) to explore for the first time the policy effect on air quality. The superposition effect caused by the establishment of a carbon emission trading scheme is empirically considered by using the difference-in-difference-in- differences (DDD) strategy. Several important findings are derived: 1) The APPCAP exerts significant negative effects on fine particulate matter (PM_2.5) concentration and SO₂ emissions in the pilot areas. 2) Results of the DDD model show that China's APPCAP still exert significant negative effects on PM_2.5 concentration and SO₂ emissions in the pilot areas of the carbon emission trading scheme. 3) The heterogeneity analysis results indicate that the effects of China's APPCAP on air pollution in the key urban agglomerations are consistent and significantly negative under different conditions.