The World Health Organization has released the first air quality database, which contains air quality data of nearly 9 1100 cities in 9 countries and regions around the world, including capital cities and cities with a population of over 65,438+million. This database collects the data of air suspended particulate matter, which has the greatest impact on human health, and investigates two specifications of suspended particulate matter from 2003 to 20 10 (most data come from 2008 and 2009), that is, particles with diameters less than or equal to 10 micron (PM 10) and particles with diameters less than 2. The air quality in Beijing is almost at the bottom. The results of the global air test conducted by the World Health Organization show that despite the short-term success in cleaning up polluted air during the 2008 Olympic Games, Beijing is still ranked as the dirtiest capital in the world with a score of 10, only slightly better than Ulaanbaatar, Gaborone, New Delhi, Islamabad, Riyadh, Dakar, Cairo, Dhaka and Kuwait City. Among the 30 cities in Chinese mainland covered by this test, Beijing ranks 26th. In 2009, the content of suspended particles per cubic meter of air was 1, 2 1 microgram. Ma of Tsinghua University said that this ranking highlights the gap between Beijing and international metropolises in industrialized countries in environmental pollution control. He said: "We have made great achievements, but obviously we still have a lot of room for improvement." Haikou ranks 8 14, which is the city with the best air quality in Chinese mainland, with 38 micrograms of suspended particles per cubic meter of air. Lhasa and Nanning rank second and third in mainland cities respectively, and Guangzhou ranks sixth, with 70 micrograms of suspended particulate matter per cubic meter of air. The cities with the lowest content of inhalable particulate matter in China are Haikou (8 14), Lhasa (89 1) and Nanning (892). Beijing is 1035, and Hangzhou, Zhengzhou, Nanjing, Harbin, Tianjin, Shijiazhuang, Chongqing, Wuhan, Taiyuan, Shenyang, Chengdu, Hefei, Xi, Jinan, Urumqi and Xining rank above 1000. The most serious is Lanzhou, ranking 1058.