Why does the air quality get worse when there is fog?

The problem is just the opposite: it is precisely because of the deterioration of air quality that smog appears. Once night falls, the temperature of the air will drop and the water vapor in the air will condense into liquid water. At this time, they will gather together with small solid particles as the center to form small droplets; In other words, small solid particles are a necessary condition for fog formation. If there are a lot of small solid particles in the air (that is, polluted), we will see countless small water droplets, also known as fog.