The influence of increased population density in China on air pollution.

Even though the relationship between population density and air pollution in China has been studied in recent years, most previous studies have suggested that an increase in population density increases air pollution. Using a panel dataset of 284 cities over the years 2003-2016 and 30 provinces during 2004-2015, as well as PM2.5 and SO2 used as air pollution indicators, the results show that an increase in population density will reduce air pollution in china. Through the mediation effect test, we found that clean energy and public transportation are the two mediation channels for population agglomeration to affect air quality. The concentration of population in cities is conducive to reducing the average cost of natural monopoly industries such as electricity, coal gas, liquefied petroleum gas, natural gas, and public transportation, thereby increasing residents' consumption of clean energy and public transportation services, reducing gas emissions that cause pollution, and improving air quality.