There are many reasons for being close to the countryside. For example, some factories need raw materials produced in local rural areas and are built nearby, which reduces the transportation links of raw materials and facilitates the storage and processing of raw materials; Other factories are highly polluting enterprises. If they are built in cities, they will inevitably cause great pollution to the urban environment and air, while the urban population is relatively concentrated, so the impact is great. If they are built in rural areas, the population is small and the impact is relatively small. Then an ugly phenomenon appeared. Some unscrupulous enterprises set up factories in rural areas to evade inspection by environmental protection departments and steal sewage and harmful gases.