Evaluating the effects of air pollution control policies in China using a difference-in-differences approach

Air pollution has caused wide concern in China, and many governance policies and plans have been implemented in recent years. Based on counterfactual quasi-natural experiments, we analyzed the implementation effects of autumn and winter air pollution control policies in the Jing-Jin-Ji region and surrounding areas using a difference-in-differences (DID) model. The control group was selected based on geographical and meteorological factors, and we analyzed the impact of the policies on six pollutants. The results show that the policies reduced air pollution overall, but not every pollutant. Due to the policy contribution, the concentrations of PM_2.5 and PM₁₀ in autumn and winter from 2017 to 2018 decreased by 6.9 % and 8.5 %, respectively. The numerical value of PM_2.5, PM₁₀, CO, and AQI in 2018-2019 decreased by 18.2 %, 7.2 %, 13.9 %, and 8.8 %, respectively. The role in the reduction of O₃, SO₂, and NO₂ was not obvious. This work provides a research paradigm for evaluating the effects of atmospheric environment policy which can be applied to other studies and provide references for formulating additional policies.