The quality of air in 29 major Chinese cities was good this week, while that in some northern cities was poor, the China Environmental Monitoring Center said on January 21.

In their weekly report issued January 21, the center said weak winds in north China during the first half of the week were responsible for the increased concentration of pollutants in the air, causing serious air pollution.

Despite stronger winds later in the week that helped disperse some of the pollutants, the air in most major cities in north China was slightly worse than last week.

From January 14 to 21, the cities of Guilin, Wenzhou, Nantong, Zhanjiang, Haikou, and Fuzhou reported excellent air, while Zhuhai,Wuhan, Zhengzhou, Chengdu, Qingdao, Shanghai, and 16 other cities in south China reported fairly good air.

Tianjin, Guangzhou, Changchun, Chongqing, and nine other citiesreported slightly polluted air.

Beijing and Shijiazhuang in north China, and Urumqi in northwest China, reported unhealthy air, while Hohhot in north China reported hazardous air.

Hohhot, Beijing, Shijiazhuang, Urumqi, and 24 other cities listed suspended particles as the major pollutant.

Nitrogen oxide was the major pollutant in Shanghai, Guangzhou, Shenzhen, Zhuhai, and Wuhan, while Chongqing, Jinan, Guiyang, Changsha, Yantai, and Qingdao reported sulfur dioxide as the main culprit.