## 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 c c} \hline  & & **(1) Eastern Region** & **(2) Central Region** & **(3) Western Region** \\ \hline  & & **InAEP** & **InAEP** & **InAEP** \\ \hline  & LR\_Total & & & \\  & wlnAPI & \(-1.519\) & \(-0.353\) & \(-2.281\) \\  & & (\(-1.293\)) & (\(-0.317\)) & (\(-1.601\)) \\  & Iner & \(-0.398\)\({}^{***}\) & \(-0.294\)\({}^{**}\) & \(0.020\) \\  & & (\(-3.095\)) & (\(-2.492\)) & (\(0.244\)) \\  & Inden & \(0.467\) & \(0.548\)\({}^{**}\) & \(-0.118\) \\  & & (\(1.606\)) & (\(2.570\)) & (\(-0.743\)) \\ The Total Effect & Inbua & \(0.875\)\({}^{**}\) & \(-0.623\) & \(-2.527\)\({}^{***}\) \\  & & (\(2.172\)) & (\(-1.193\)) & (\(-4.098\)) \\  & Iney & \(-2.167\)\({}^{***}\) & \(-1.932\)\({}^{***}\) & \(-1.302\)\({}^{***}\) \\  & & (\(-8.243\)) & (\(-6.824\)) & (\(-4.361\)) \\  & Inin & \(7.304\)\({}^{***}\) & \(1.925\)\({}^{***}\) & \(0.078\) \\  & & (\(9.752\)) & (\(3.254\)) & (\(0.126\)) \\  & \(N\) & \(1386\) & \(1400\) & \(1204\) \\  & \(R^{2}\) & \(0.665\) & \(0.459\) & \(0.284\) \\ \hline  & LR\_Direct & & & \\  & wlnAPI & \(-1.347\)\({}^{***}\) & \(-1.261\)\({}^{***}\) & \(-3.144\)\({}^{***}\) \\  & & (\(-4.082\)) & (\(-3.313\)) & (\(-4.392\)) \\  & Iner & \(-0.048\)\({}^{**}\) & \(-0.054\)\({}^{**}\) & \(-0.048\)\({}^{*}\) \\  & & (\(-2.165\)) & (\(-2.074\)) & (\(-1.726\)) \\  & Inden & \(-0.100\)\({}^{*}\) & \(-0.072\) & \(-0.146\)\({}^{**}\) \\  & & (\(-1.854\)) & (\(-1.344\)) & (\(-2.098\)) \\ The Direct Effect & Inbua & \(-0.059\) & \(-0.303\)\({}^{***}\) & \(-0.700\)\({}^{***}\) \\  & & (\(-0.878\)) & (\(-2.717\)) & (\(-3.473\)) \\  & Iney & \(-1.590\)\({}^{***}\) & \(-2.056\)\({}^{***}\) & \(-1.478\)\({}^{***}\) \\  & & (\(-20.968\)) & (\(-17.781\)) & (\(-12.321\)) \\  & Inin & \(2.162\)\({}^{***}\) & \(1.639\)\({}^{***}\) & \(-0.761\)\({}^{**}\) \\  & & (\(10.122\)) & (\(7.059\)) & (\(-2.421\)) \\  & \(N\) & \(1386\) & \(1400\) & \(1204\) \\  & \(R^{2}\) & \(0.665\) & \(0.459\) & \(0.284\) \\ \hline  & LR\_Indirect & & & \\  & wlnAPI & \(-0.172\) & \(0.908\) & \(0.863\) \\  & & (\(-0.162\)) & (\(0.873\)) & (\(0.616\)) \\  & Iner & \(-0.350\)\({}^{**}\) & \(-0.240\)\({}^{**}\) & \(0.069\) \\  & & (\(-3.077\)) & (\(-2.258\)) & (\(0.922\)) \\  & Inden & \(0.567\)\({}^{**}\) & \(0.620\)\({}^{***}\) & \(0.029\) \\  & & (\(2.194\)) & (\(3.194\)) & (\(0.197\)) \\ The Indirect Effect & Inbua & \(0.935\)\({}^{***}\) & \(-0.320\) & \(-1.827\)\({}^{***}\) \\  & & (\(2.601\)) & (\(-0.682\)) & (\(-3.430\)) \\  & Iney & \(-0.577\)\({}^{**}\) & \(0.124\)\({}^{*}\) & \(0.176\) \\  & & (\(-2.465\)) & (\(0.467\)) & (\(0.626\)) \\  & Inin & \(5.142\)\({}^{***}\) & \(0.286\) & \(0.839\)\({}^{*}\) \\  & & (\(8.185\)) & (\(0.540\)) & (\(1.676\)) \\ \(N\) & \(1386\) & \(1400\) & \(1204\) \\  & \(R^{2}\) & \(0.665\) & \(0.459\) & \(0.284\) \\ \hline \end{tabular} \(t\) statistics in parentheses. \({}^{*}p<0.1\), \({}^{**}p<0.05\), \({}^{***}p<0.01\).  
\end{table} 
Table 11: The Regression Results of SDM Model Heterogeneity in Eastern, Central and Western Regions. In the western region, the direct effect of atmospheric self-purification capacity on environmental pollution proves significantly negative, with a coefficient of \(-3.144\). Generally speaking, inconveniently located and sparsely populated, the western region is less economically developed than the eastern and central regions. The lower level of economic development objectively diminishes environmental pollution. In the western region, environmental pollution arises from the consumption of resources and the emission of pollutants in economic growth. In 2001, China implemented the strategy of development of the western regions in China, which improves the scale and quality of economic growth in the western region. On this basis, the western region reinforces the governance and control of polluting industries, increases investment to pollution treatment, realizes green and healthy development of enterprises, and transforms the traditional model into a new model in industrial development.