Why is Zhengzhou more polluted than Beijing?

First, in second-tier cities, people's economic level is limited, which leads to poor awareness.

Secondly, Zhengzhou itself is in the plain, and the weather itself is relatively dry. What's more, there is little rain and the weather is dry.

Third, there are many people and many cars.

Fourth, roads are being built everywhere. Zhengzhou now extends in all directions.