Based on ground observation data and satellite remote sensing, the Tsinghua team found that, compared to 2013, the average PM2.5 concentration in Hebei fell by 39.6%, in the Yangtze River Delta by 34.3%, and in the Pearl River Delta by 27.7%, Through implementation of the “Air Pollution Action Plan” of 2013 and other measures,, nationwide sulfur dioxide emissions were reduced by 16.4 million tons, nitrogen oxides by 8 million tons, and primary PM2.5 by 3.5 million tons. Improvements in industry standards such as ultra-low power conversion and improvements in key industries such as steel and concrete, countermeasures for coal-fired boilers, delayed production capacity dredging, and clean-up of civilian fuels to improve air quality, PM2.5 exposure levels across the country were reduced down to 2.2 micrograms per cubic meter.
https://www.pnas.org/content/early/2019/11/12/1907956116