Relevant MEP official recently released air quality of key regions (Beijing-Tianjin-Hebei region, Yangtze River Delta and the Pearl River Delta) and 74 cities (municipalities directly under the central government, capital cities of provinces and municipalities separately listed in the state plan) in May 2013.

Monitoring results indicated that, in May, the average days with up-to-standard air quality in the 74 cities accounted for 60.1% and that exceeded the standard made up 39.9% including 29.4% days of slight pollution, 8.3% medium pollution, 2.1% heavy pollution and 0.1% severe pollution. Of which, up-to-standard rate of Haikou, Zhuhai, Shenzhen and Fuzhou was 100%, that of 14 cities were between 80% and 100%, 34 cities were between 50% and 80%, while 22 cities were lower than 50%. The primary pollutants were O3 and PM2.5.Compared with the previous month, days with up-to-standard air quality in all 74 cities dropped by 3.4 percentage points while that of heavy pollution and severe pollution increased by 0.2 percentage points respectively. As assessed by the "Environmental Standard on Air Quality" (GB3095-2012), compared with last month, the monthly average concentration of PM2.5, PM10, SO2 and NO2 in 74 cities all dropped in May, the standard-exceeding rate of CO was basically the same while that of O3 increased significantly with the enhancement of sunlight and the rise of temperature. The level of PM2.5 exceeded the standard by 20.3% on average. Heifei had the maximum daily average value of 296 μg/m3 and the largest exceeding multiple of 2.9. PM2.5 concentration averaged 55μg/m3 monthly, and Shijiazhuang had the maximum value of 113μg/m3. The standard-exceeding rate of PM10 averaged 17.5%, and Huhhot had the maximum daily average value of 591μg/m3 and the biggest exceeding multiple of 2.9. The monthly average PM10 concentration was 101 mg/m3, and the highest value of 289μg/m3 was recorded in Shijiazhuang. NO2 exceeded the standard by 1.5% on average. Tangshan had the maximum daily average value of 109μg/m3 and the biggest exceeding multiple of 0.4. The monthly average concentration of NO2 was 37μg/m3 and Tangshan had the highest value of 80μg/m3.SO2 exceeded the standard by 0.9% on average, and Tangshan had the maximum daily average value of 260μg/m3 and the largest exceeding multiple of 0.7. The monthly average SO2 concentration was 29μg/m3, and the highest value of 141μg/m3 was recorded in Tangshan. The standard-exceeding rate of CO averaged 0.2%, its maximum daily average value of 4.1 mg/m3 and the biggest exceeding multiple of 0.03 were found in Tangshan. The daily maximum eight-hour average O3 concentrations exceeded the standard by 26.9% on average, with the highest concentration of 430μg/m3 and the biggest exceeding multiple of 1.7 being found in Handan. According to comprehensive index assessment of air quality, cities suffering from air pollution included Shijiazhuang, Tangshan, Xingtai, Handan, Jinan, Baoding, Zhengzhou, Beijing, Hengshui and Tianjin. Conversely, cities posting better air quality included Haikou, Huizhou, Fuzhou, Zhuhai, Zhoushan, Zhongshan, Shenzhen, Jiangmen, Dongguan and Xiamen.

In Beijing-Tianjin-Hebei region, days with up-to-standard air quality accounted for 27.4% on average, which is 32.7 percentage points lower than the national average, by contrast, days of severe pollution accounted for 8.7%, which is 6.5 percentage points higher than the national average. Among the 13 cities in this region, air quality up-to-standard rate of Zhangjiakou and Qinhuangdao ranged from 50% to 80% and that of other cities, however, were lower than 50%, indicating severe air pollution. Regional primary pollutants were PM2.5 and O3. In contrast with the previous month, in May, air quality of this region deteriorated compared with the same period of last year because of the adverse weather conditions impeding air diffusion. In terms of the pollutant concentration, the monthly average concentrations of PM2.5, PM10, SO2 and NO2 were increased by 19.1%、14.4%，3.7% and 4.9% respectively compared with the previous month. Beijing's air quality in May was worse than that in April, with an increase of its monthly average concentration of PM2.5 from 61μg/m3 to 81μg/m3, PM10 from 99μg/m3 to 129μg/m3, SO2 from 21μg/m3 to 26μg/m3, NO2 from 45μg/m3 to 51μg/m3. Thus, its rate of days with up-to-standard air quality decreased from 62.1% to 25.8%, down 36.3 percentage points.

Days with up-to-standard air quality in the Yangtze River Delta accounted for 60.7% on average, which was 0.6 percentage points higher than the national average. Among the 25 cities in this region, Zhoushan and Wenzhou's air quality was relatively good, where the air quality up-to-standard rates were both higher than 80%, by contrast, Nanjing, Xuzhou, Hangzhou and Yangzhou suffered from serious pollution and the rates of all the four cities were lower than 50%. O3 and PM2.5 were the primary pollutants in this region. The data indicated that, compared with last month, the up-to-standard rates of 25 cities in this region dropped from 61.7% to 60.7%, down 1.0 percentage points. Among them, up-to-standard rates of 12 cities such as Wenzhou, Ningbo and Taizhou were increased, that of Zhenjiang remained unchanged, and that of 12 cities including Xuzhou, Huai'an, Taizhou and Jinhua declined. As for the pollutant concentration, the monthly average concentrations of PM2.5, PM10, SO2 and NO2 decreased significantly and daily average CO concentrations were all in line with the standards. However, as the sunlight intensified and the temperature rose in the summer, the daily maximum eight-hour concentration of O3 increased significantly. Air quality in Shanghai has improved, and its rate of days with up-to-standard air quality increased by 11 percentage points, from 60.0% to 71.0%.

Days with up-to-standard air quality in the Pearl River Delta accounted for 89.5% on average, which was 29.4 percentage points higher than the national average. Among the nine cities in this region, air quality of Zhuhai, Zhongshan, Huizhou, Shenzhen, Zhaoqing, Dongguan, Foshan and Jiangmen was relatively good, where the air quality up-to-standard rates were higher than 80%. In contrast, the rate of Guangzhou was 71%. O3 was the primary pollutant in this region. Guangzhou's air quality has improved, and its rate of days with up-to-standard air quality increased by 1.0 percentage points, from 70.0% to 71.0%.