Is the key-treatment-in-key-areas approach in air pollution control policy effective? Evidence from the action plan for air pollution prevention and control in China

The "Action Plan for Air Pollution Prevention and Control from 2013 to 2017 " (APAPPC) establishes the key treatment for key areas in Beijing-Tianjin-Hebei and its surroundings (BTH), the Yangtze River Delta (YRD), and the Pearl River Delta (PRD) in China. Is the key-treatment-in-key-areas approach effective? Except the targeted pollutants, does there exist the synergistic effects of other air pollutants? Are there differences between the north and the south about the effectiveness of this approach? To answer these new and key questions, this study uses the difference-in-difference (DID) model to evaluate whether it is more effective to implement key treatment policies for two targeted pollutants, PM2.5 and PMcoarse(PM2.5-PM10), and verifies the synergistic emission-reduction effects of the policies on eight other emissions: SO2, NOX, VOC, CO, NH3, BC, OC, and CO2. At the same time, the policy effects are evaluated nationwide, in the north, and in the south using data from 2008 to 2017. The results show the following: (1) The APAPPC's establishment of the key treatment in key areas significantly reduces PM2.5 and PMcoarse by 7.25 % and 10.49 %, respectively, compared with non-key areas nationwide. (2) The key-treatment-in-key-areas policy has synergistic effects on six other emissions: SO2, NOX, CO, BC, OC, and CO2. (3) If viewing the north and the south separately, BTH beats other counterparts in the north by a large margin, while there is no significant difference among provinces and/or areas in the south. This margin is much larger than the one between key areas and other provinces nationwide. Therefore, this paper suggests that key treatment policies in key areas should continue to be implemented, especially for cities that have not dropped, but rather increased, their PM2.5 concentrations. Additionally, air pollution goals should incorporate China's carbon peaking and neutrality goals to reduce air pollutants and greenhouse gas emissions.