What are the levels of air pollution index currently used in China?

Interpretation of air pollution index and air quality grade Kang Yongjun of Tianjin Tanggu Education Center broadcasts the forecast of "air pollution index and air quality grade" in the daily weather forecast program. What is the meaning of "air pollution index and air quality grade"? Experts explained that the content, toxicity and environmental impact of various pollutants in the atmosphere are very different. In order to describe the air pollution degree of various pollutants simply and intuitively, the relationship between air quality parameters such as pollutant concentration and pollution level is expressed by a unified mathematical formula, and a simple relative value is calculated to express the intensity of air pollution. People call such a numerical value that can show the degree of air pollution caused by the primary pollutants in the air as the comprehensive index of ambient air quality. In addition, all kinds of pollutants in the air have their own pollution index, which is called sub-index. At present, the monitoring items of air quality in key cities in China are uniformly defined as sulfur dioxide (SO2), nitrogen dioxide (NO2) and total suspended particulate matter (TSP), and the value of air pollution index is represented by a number between 0 and 500. The range of air pollution index is 0 ~ 500, where 0 ~ 50, 5 1 ~ 100, 100 ~ 200, 20 1 ~ 300 and greater than 300 respectively correspond to the daily average values in China air quality standards. The air quality grade and its influence on human health are as follows: First, the air quality is evaluated as excellent and has no influence on human health; Grade II, with good air quality evaluation and no obvious impact on human health; Grade 3, mild pollution, irritating symptoms in healthy people; Grade 4, moderate pollution, and irritating symptoms generally appear in healthy people; Grade 5, serious pollution, and severe irritation to healthy people. 200 1, 1, Lanzhou's pollution index is 448, that is, the air quality is Grade 5, which is a serious pollution. Experts say that air pollution is the enemy of human health, and remind everyone to pay attention to this special weather forecast in order to take appropriate measures to reduce the harm of air pollution.