Beijing News reported on April 24 that, within two hours, the city suffered an air pollution level six, which is the highest severity possible. The primary pollutant was PM10. At 7PM, Beijing city air quality index arrived at 350, which qualified as level six. Northwest of Beijing, including the Olympics Village, it reached 400. Some areas, including a few train stations of the city, even reached the maximum index value of 500, which is the highest measurable with the equipment in place. This level of air pollution was unusually high, even for a city like Beijing. {Editor’s note: Particulate Matter 10 (PM10) describes inhalable particles, with diameters that are generally 10 micrometers and smaller. According to the EPA (U.S. Environmental Protection Agency), the U.S. National Annual Second Maximum 24-Hour Average for PM10 has been consistently below 150 for the past 30 years.}
Source: Beijing News, April 24, 2020
http://www.bjnews.com.cn/news/2020/04/24/720854.html