Most of the major cities in China reported slightly improved air quality this week, according to the weekly air-quality report issued by the China Environmental Monitoring Center.

From October 29 to November 4, cold air current moving southward slowed down the spread of pollutants over most of China, thus reducing air pollution in some cities in the north.

During this period, the air quality in nine cities including Nanning and Kunming in southwest China was excellent while 26 other cities, including Tianjin, Wuhan, Xi'an, Shenyang, Chengdu, Guangzhou, Nanjing and Suzhou reported good air quality.

Beijing, Urumqi, Zhengzhou, Shijiazhuang, Shanghai, Taiyuan and Qinhuangdao reported slightly polluted air quality.

The air quality in Xining in the northwest and Hohhot in the north was polluted, and that in Lanzhou in the northwest was seriously polluted.

Lanzhou, Hohhot, Xining and 14 other cities blamed suspended particles as the major pollutant.

Nitrogen oxide was the major pollutant in Beijing, Shanghai, Guangzhou and five other cities, while Chongqing, Changsha, Qindao and Guiyang claimed sulfur dioxide as the major problem.