Spatiotemporal trends in PM2.5 levels from 2013 to 2017 and regional demarcations for joint prevention and control of atmospheric pollution in China.

The promulgation and implementation of the Air Pollution Prevention and Control Action Plan (APPCAP) have greatly accelerated air quality improvements in China. In this study, these improvements were assessed and analyzed using arithmetic mean and percentile methods. Air quality status and trends were illustrated meticulously. Air pollution risks remaining since the implementation of the APPCAP were also identified. In addition, a complex network correlation model was created and used to demarcate highly inter-correlated regions within China, which were identified using long-term PM2.5 concentration data. The results indicate that the annual mean PM2.5 concentration decreased by more than 30% throughout the country since the implementation of the APPCAP. However, more than 1 billion people were still exposed to polluted air containing PM2.5 concentrations exceeding the WHO Interim Target-1 (WHO IT-1). Cities with populations of more than 10 million were generally among the most polluted regions in China, while PM2.5 concentrations in locations with populations of less than 1 million met WHO IT-1 standards. Moreover, PM2.5 network correlation analysis defined 7 key Joint Prevention and Control of Atmospheric Pollution (JPCAP) regions with strong synchronicity in PM2.5 mass concentrations; these results suggest that JPCAP could be implemented separately with in each of these demarcated regions. The atmospheric pollution control concepts and methods proposed herein are also broadly applicable for the implementation of JPCAP policies in other regions worldwide.