The influence of population agglomeration on air pollution: An empirical study based on the mediating effect model

With rapid urbanization and industrialization, the population of metropolis in China is increasing. Previous studies suggest that population agglomeration would have a significant impact on air pollution in cities. Using a panel dataset of 30 provincial capital cities during 2013-2017, as well as days of air quality equal to or above Grade II as air pollution indicators, the results show that an increase of population density will improve air quality in large cities. Through the mediation effect test, this paper found that tertiary industry is the mediation channel of population agglomeration to reduce air pollution. An increase of population density in big cities is conductive to increasing the proportion of tertiary industry, thereby reducing the proportion of seriously polluting secondary industry, and reducing air pollution.