## 4 Results and Analysis
### Results of Simultaneous Equations Model
#### 4.2.1 Impact of Industrial Structure on Air Pollution
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **(1)** & **(2)** & **(3)** & **(4)** & **(5)** & **(6)** \\ \hline
3S & & & & & & & \\ _PM2.5_ & \(-0.180\)\({}^{*}\) & \(-0.148\) & \(-0.131\)\({}^{***}\) & \(-0.149\)\({}^{***}\) & \(-0.307\)\({}^{***}\) & \(-0.290\)\({}^{***}\) \\  & (\(-1.91\)) & (\(-1.56\)) & (\(-3.05\)) & (\(-3.73\)) & (\(-9.46\)) & (\(-9.11\)) \\ _FA_ (_ln_) & 4.396 \({}^{***}\) & 4.259 \({}^{***}\) & \(-3.268\)\({}^{***}\) & \(-3.201\)\({}^{***}\) & \(-2.776\)\({}^{***}\) & \(-2.761\)\({}^{***}\) \\  & (7.25) & (6.99) & (\(-5.48\)) & (\(-5.45\)) & (\(-4.52\)) & (\(-4.54\)) \\ _Innovation_ (_ln_) & & & 7.400 \({}^{***}\) & 7.416 \({}^{***}\) & 7.555 \({}^{***}\) & 7.516 \({}^{***}\) \\  & & & (15.44) & (15.67) & (13.45) & (13.53) \\ _Open_ & & & & & & \(-0.135\) & \(-0.114\) \\  & & & & & & \(-0.62\)) & (\(-0.53\)) \\ _\_cons_ & \(-19.261\)\({}^{***}\) & \(-18.959\)\({}^{***}\) & 49.172 \({}^{***}\) & 49.108 \({}^{***}\) & 50.961 \({}^{***}\) & 49.941 \({}^{***}\) \\  & (\(-2.64\)) & (\(-2.58\)) & (7.29) & (7.36) & (7.28) & (7.21) \\
**PM2.5** & & & & & & & \\ _3S_ & 0.969 \({}^{***}\) & \(-423.210\)\({}^{***}\) & \(-0.467\)\({}^{**}\) & \(-0.436\)\({}^{*}\) & \(-0.385\)\({}^{*}\) & \(-0.425\)\({}^{*}\) \\  & (3.04) & (\(-5.09\)) & (\(-2.08\)) & (\(-1.89\)) & (\(-1.63\)) & (\(-1.85\)) \\ _Pop_ (_ln_) & 10.804 \({}^{***}\) & \(-311.644\)\({}^{***}\) & 8.021 \({}^{***}\) & 7.693 \({}^{***}\) & 4.100 \({}^{***}\) & 3.959 \({}^{***}\) \\  & (4.79) & (\(-4.82\)) & (5.52) & (5.31) & (3.28) & (3.17) \\ _FDI_ (_ln_) & & & 1880.267 \({}^{***}\) & \(-2.806\)\({}^{**}\) & \(-0.293\) & 3.984 \({}^{***}\) & 4.462 \({}^{***}\) \\  & & & (5.25) & (\(-2.16\)) & (\(-0.18\)) & (2.91) & (3.23) \\ _Trans_ (_ln_) & & & & 17.185 \({}^{***}\) & 15.340 \({}^{***}\) & 24.773 \({}^{***}\) & 22.647 \({}^{***}\) \\  & & & & (8.00) & (6.50) & (9.89) & (8.36) \\ _Enviro_ & & & & \(-0.680\)\({}^{***}\) & \(-0.771\)\({}^{***}\) & \(-0.622\)\({}^{***}\) & \(-0.601\)\({}^{***}\) \\  & & & & (\(-4.21\)) & (\(-4.46\)) & (\(-4.52\)) & (\(-4.36\)) \\ _Open_ & & & & & \(-1.492\)\({}^{**}\) & \(-1.450\)\({}^{**}\) & \(-1.644\)\({}^{***}\) \\  & & & & & (\(-2.23\)) & (\(-2.50\)) & (\(-2.86\)) \\ _UL_ & & & & & & \(-1.235\)\({}^{***}\) & \(-1.248\)\({}^{***}\) \\  & & & & & & (\(-5.25\)) & (\(-5.47\)) \\ _CEI_ & & & & & & & \(-1.646\)\({}^{**}\) \\  & \(\_\)_cons_ & \(-63.662\)\({}^{***}\) & \(-4094.03\)\({}^{***}\) & 21.775 & 4.761 & \(-6.153\) & 3.316 \\  & (\(-2.81\)) & (\(-5.91\)) & (1.32) & (0.26) & (\(-0.39\)) & (0.20) \\ R-sq & \(-0.379\) & 375e+04 & 0.441 & 0.449 & 0.544 & 0.564 \\ \(N\) & 234 & 234 & 234 & 234 & 234 & 234 \\ \hline \multicolumn{6}{l}{Note: The numbers in brackets are t statistics; \({}^{***}\), \({}^{**}\), and \({}^{*}\) represent their significance at 1%, 5%, and 10% levels, respectively.} \\ \end{tabular}
\end{table} 
Table 5: Estimated results of the simultaneous equations for tertiary industry and air pollution. international cooperation in the Beijing-Tianjin-Hebei region has brought advanced technology to the local area, thereby allowing the processing and manufacturing processes to become cleaner. At the same time, urbanization can increase the utilization rate of public facilities and public transportation, form industrial agglomeration, and thereby reduce energy consumption and pollution treatment costs, which is conducive to reducing pollution emissions. Interestingly, the energy intensity coefficient is also significantly negative, which shows that the carbon dioxide reduction measures issued by the government have not played a role in reducing air pollution levels, but caused the situation to be worse, indicating that the Beijing-Tianjin-Hebei region urgently needs to expand and improve the existing environmental regulations.