In August, 338 domestic cities in China experienced an average of about 27 days with good air quality, as levels of major airborne pollutants such as PM2.5 — fine particulate matter less than 2.5 microns in diameter that is especially hazardous for human health — were greatly reduced, the Ministry of Environmental Protection said on Monday.

The cities' registered 89.6 percent of days in August as having good air quality, a year-on-year increase of 1.9 percent, said Luo Yi, head of the ministry's environmental monitoring department.

Average concentration levels of PM2.5 for the cities decreased by 14.7 percent year-on-year, to 29 micrograms per cubic meter, surpassing the national safety standard, the ministry's monthly report said.

Concentration levels of PM10 — fine particulate matter less than 10 microns in diameter?- fell by 17.5 percent year-on-year, it added.

For the 74 major cities, Chengdu, capital of Southwest China's Sichuan province, was ranked the second-most polluted city in August, behind Langfang in North China's Hebei province, which was ranked the most polluted, the ministry said.

Hebei province, which usually has six or seven of the top-10 most polluted cities, had five cities on the list for August, including Langfang, Tangshan, Hengshui, Handan and Xingtai.

The 10 least-polluted cities in August included three metropolises: Shanghai; Zhuhai in Guangzhou province; and Qingdao in Shandong province.