Can national urban agglomeration construction reduce PM2.5 pollution? Evidence from a quasi-natural experiment in China

Urban agglomerations, as a new model of urbanization and a means of regional integration, provide modern ideas for achieving haze pollution control. Treating the implementation of Urban Agglomeration Development Plan as a quasi-natural experiment, the multi period DID method is applied to examine the impact of the national urban agglomeration construction (NUAC) on PM2.5 pollution reduction. Furthermore, the heterogeneity analysis, transmission mechanism and spatial spillover effects are explored in depth. Our analysis yields the following conclusions. First, NUAC has a positive effect on PM2.5 pollution control. More Specifically, the annual average PM2.5 concentration will decrease by 7.9% in urban agglomeration cities. And a series of robustness tests confirms the credibility of this conclusion. Second, regarding the heterogeneity of urban characteristics, the pollution mitigation effect of NUAC is more pronounced in central and western cities, small-scale cities, non-resource-based cities and cities with stricter environmental regulation. Third, analysis of transmission mechanism suggests that NUAC suppresses haze pollution mainly by accelerating industrial agglomeration, promoting technological innovation and reducing resource misallocation. Finally, taking the spatial correlation of air pollutants into account, the environmental improvement effect of NUAC still exists. Furthermore, results of spatial spillover effects show that the pilot policy is detrimental to PM2.5 pollution reduction in other urban agglomeration cities, which means that there is no linkage effect in regional pollution control and environmental management. These results provide reference to not only the Chinese government for effective strategies to cope with PM2.5 pollution but also the studies on regional environmental governance in the international context.