What is the reason for the foggy weather in Shanghai?

The general smog in developed cities is mainly due to air stagnation, which makes tiny particles in the air gather and float in the air. The ground is dusty and the air humidity is low. People and vehicles on the ground stir up dust. Automobile exhaust is the main pollutant emission, and there are more and more cars. Automobile exhaust is a factor of smog. Secondary pollution produced by factories. CO2 and other pollutants emitted by heating in winter! It is very harmful to the human body! I use ZRA, very satisfied! For your health!