## 4 Measurement Estimation and Analysis
### Robustness Test
#### 4.4.2 The Analysis of the Regression Results of Eastern, Central, and Western Regions
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **(1)** & **(2)** \\ \hline  & **InPM** & **InPM** \\ \hline wlnAPI & \(-0.827\)*** & \(-0.822\)*** \\  & \((-10.479)\) & \((-10.438)\) \\ Inden & \(0.043\)*** & \(0.043\)*** \\  & \((8.153)\) & \((8.187)\) \\ Inbua & \(-0.086\)*** & \(-0.087\)*** \\  & \((-7.233)\) & \((-7.315)\) \\ lner & \(-0.078\)*** & \(-0.082\)*** \\  & \((-10.608)\) & \((-11.070)\) \\ Inin & \(0.300\)*** & \(0.302\)*** \\  & \((14.075)\) & \((14.180)\) \\
0\_catf\_c.lner & \(-0.006\)** & \(-0.037\)*** \\  & \((-2.004)\) & \((-4.788)\) \\
1\_catf\_c.lner & \(0.002\) & \((-0.000)\) \\
0\_catf\_c.lner & \((0.978)\) & \((-0.154)\) \\
2\_catf\_c.lner & & \(0.006\)** \\  & \((2.565)\) \\  & \(\mathrm{\_cons}\) & \(3.170\)*** \\  & \((30.962)\) & \((30.951)\) \\ \hline \multicolumn{2}{c}{\(N\)} & \(3990\) & \(3990\) \\ \multicolumn{2}{c}{\(R^{2}\)} & \(0.225\) & \(0.229\) \\ \hline \hline \end{tabular}
\end{table} 
Table 9: The Robustness Test of Threshold Effect. As Table 11 evidences, in the eastern region, local atmospheric self-purification capacity has a significant inhibitory effect on environmental pollution. To put it in another way, in terms of the direct effect, the impact of atmospheric self-purification capacity on environmental pollution proves significantly negative at the level of 1%, with a coefficient of \(-\)1.347. The continuous increase in the concentration of atmospheric environmental pollution implies the rapid development of industrial enterprises and highly polluting industries, thus driving the fast development of the urban economy in the eastern region. However, when the emission of environmental pollutants exceeds environmental bearing capacity, it will destroy atmospheric self-purification capacity, exacerbate environmental pollution, and curb the development of the eastern region. In the eastern region, with the implementation of environmental regulation, such as national policy intervention and increased emission tax, enterprises continue to enlarge the R & D investment to green-technology innovation, promote the green transformation of production, and offset the consumption and pollution of environmental resources by technological means. To create a new situation of environment-friendly and high-quality economic development, the eastern region shifts to tertiary industry such as the software industry, light industry, finance and service industry in the transformation of industrial structure, which alleviates environmental pressure. However, it is an arduous task for the eastern region to promote the governance of environmental pollution. Particularly, in Beijing-Tianjin-Hebei region, the governance effect of air pollution remains unstable. Eastern region needs to take measures such as infrastructure construction and urban-greening construction to consolidate atmospheric self-purification capacity and improve the quality of the atmospheric environment. In the central region, the direct effect of atmospheric self-purification capacity on environmental pollution proves significantly negative, with a coefficient of \(-\)1.261 at the level of 1%. The central region serves as the core region of China's heavy industry. Traditional extensive production model fosters rapid economic development and causes serious environmental pollution. China initiated the strategy of \"the Rise of Central China\" in 2004. Since then, on the one hand, the central region undertook the industrial transfer of manufacturing from the eastern region and increased the proportion of