Why is the air quality index in Shanghai always so bad?

There are Baosteel in the north, Jinshan Petrochemical in the south, Gao Qiao Petrochemical in the east, and millions of vehicles are discharged day and night. Pollution is certain. It's just that Shanghai is not far from the East China Sea after all, and there are many days when the east wind blows, and the air quality is generally better than Beijing. Recently, all gas stations in Shanghai have changed to high-grade and low-pollution oil products, which is actually the result of appeals from all parties and the attention of local governments.