P.5 All around the world large cities have the same problem. The problem is air pollution. Mexico City has very bad air. The there is dirty and very unhealthy. Cars are one reason for the drive in the city.The factories in the area also cause air pollution. These factories put a lot of smoke into the air It is not easy to clean up the air in large city.The government has to make new laws and everyone has to help. 1. air pollution 2.Mexico City,air pollution 3. how factories cause air pollution.