Population Exposure to Ambient PM at the Subdistrict Level in China.

Fine-particulate pollution is a major public health concern in China. Accurate assessment of the population exposed to PM requires high-resolution pollution and population information. This paper assesses China's potential population exposure to PM, maps its spatiotemporal variability, and simulates the effects of the recent air pollution control policy. We relate satellite-based Aerosol Optical Depth (AOD) retrievals to ground-based PM observations. We employ block cokriging (BCK) to improve the spatial interpolation of PM distribution. We use the subdistrict level population data to estimate and map the potential population exposure to PM pollution in China at the subdistrict level, the smallest administrative unit with public demographic information. During 8 April 2013 and 7 April 2014, China's population-weighted annual average PM concentration was nearly 7 times the annual average level suggested by the World Health Organization (WHO). About 1322 million people, or 98.6% of the total population, were exposed to PM at levels above WHO's daily guideline for longer than half a year. If China can achieve its Action Plan on Prevention and Control of Air Pollution targets by 2017, the population exposed to PM above China's daily standard for longer than half a year will be reduced by 85%.