How's the weather?

The urban air quality grade is the pollution index grade and the corresponding pollutant concentration limit determined according to the urban air environmental quality standard and the ecological environmental effects of various pollutants and their impact on human health. At present, the classification standard of urban air quality pollution index is:

(1) The air pollution index (API) is 0 ~ 50, and the daily average air quality is the national first-class standard. The air quality is excellent and meets the air quality requirements of nature reserves, scenic spots and other areas that need special protection.

(2) (API) 5 1 ~ 100, the daily average air quality is the national secondary standard, and the air quality is good, meeting the air quality requirements of residential areas, commercial areas, cultural areas, general industrial areas and rural areas.

(3) (API)101~ 200, which is the third class standard, and the air quality is slightly polluted. If you are exposed to this level of air for a long time, the symptoms of susceptible people will be slightly aggravated, and healthy people will have irritating symptoms. Meet the air quality requirements of specific industrial areas.

④ (API) 20 1 ~ 300, which is a four-level standard, and the air quality is moderately polluted. After exposure to the same level of air for a certain period of time, the symptoms of patients with heart disease and lung disease are obviously aggravated, the exercise tolerance is reduced, and the healthy people generally have symptoms.

⑤(API) is greater than 300, which is a five-level standard and the air quality is heavily polluted. The exercise tolerance of healthy people decreases, with obvious symptoms and some diseases.

This classification standard is the implementation standard of urban air quality forecast, and it is also the main basis for urban environmental function zoning and air quality evaluation.