Assessment of long-term particulate nitrate air pollution and its health risk in China

Air pollution is a major environmental and public health challenge in China and the Chinese government has implemented a series of strict air quality policies. However, particulate nitrate (NO3-) concentration remains high or even increases at monitoring sites despite the total PM2.5 concentration has decreased. Unfortunately, it has been difficult to estimate NO3- concentration across China due to the lack of a PM2.5 speciation monitoring network. Here, we use a machine learning model incorporating ground measurements and satellite data to characterize the spatiotemporal patterns of NO3-, thereby understanding the disease burden associated with long-term NO3- exposure in China. Our results show that existing air pollution control policies are effective, but increased NO3- of traffic emissions offset reduced NO3- of industrial emissions. In 2018, the national mean mortality burden attributable to NO3- was as high as 0.68 million, indicating that targeted regulations are needed to control NO3- pollution in China.