I add some information here to present the control strategies which have been done by China government.
A series of paper have reported that coal combustion is the main cause of the air pollution in China. This issue usually gets worse in the winter months due to the fact that coal is used for domestic heating.
In the winter of 2017, China government decided to transform the fuel types for each of the residents even in rural areas within north Chian as fast as possible. Here is a figure I captured near my campus, the giant pipes convey the natural gas to each of the residents for heating and other uses.
Although the heating fee might increase, the consumption of coal, especially for those bulk coal (known as cheap with high amount of emissions) was cut significantly.
The effects of energy structure adjustment has been observed clearly. As shown in this figure presenting the monthly variations of PM2.5 in 2015, 2016 and 2017, the improvement of air quality is an obvious one. Especially in December when the strict control strategies were implemented, the concentration decreased sharply compared to 2015/2016.
By sharing the example of Beijing, I make a point that the improvement of air quality is possible by applying the current technology. What's more, the movement from traditional fuels to clean fuels seems to be a more efficient approach compared to the end-of-pipe control with advanced technology.