“…Considering that monitoring validity and PM2.5 was only available after 2013, we measured HAZ by using Annual Average Concentration of PM10 (mg/m 3 ) of each city, given that PM10 was the principal component of haze pollution, and thus, it could reflect urban air condition to a great extent (Wang et al, ; Yang et al, ; Zhang, Wang, Niu, Zhang, & S., L., Zhang, Y., M.,, & Sun, J., Y., ). As for the threshold variable, environmental regulation (REG), caparisoning scholars' understanding of the five dimensions of the subject, object, goal, means, and nature (Hou et al, ; Porter, ; Xie, Yuan, & Huang, ), we define environmental regulation as a binding force for the purpose of environmental protection, for individuals or organizations, and for the form of physical system or intangible consciousness. For the measurement of environmental regulation, relevant scholars mainly use the following three approaches: The first is the intensity of environmental regulation by pollutant discharge tax (Levinson, ); the second is the ratio of comprehensive utilization output value of “three wastes” (waste gas, wastewater, and industrial residues) to GDP (Hao et al, ); the third is to use the Environmental Policy Strictness Index as proxy (Stern & Zha, ).…”