A report on air quality in 74 major Chinese cities has released. The days with heavy to severe pollution increased in June by 3 percent compared to May.

The Ministry of Environmental Protection Air says air quality reached standard for 64.4 percent days in June on average. Of those days with air quality below standard, 21.5 percent saw slight pollution, and medium pollution was recorded for 8.8 percent days. Heavy pollution and severe pollution accounted for close to 5 percent days and 0.4 percent days on average.

For 19 out of the 74 cities, over half of the days in June saw air quality below standard. The pollution was particularly bad in north China's Beijing and Tianjin municipalities and Hebei Province. Air quality was up to standard for only 24.2 days of June in the region, over 40 percentage points lower than the average.

The primary source of pollution is PM2.5, that is, particles with a diameter equal to or less than 2.5 micrometers. Ozone is another main source.

(CNTV.cn July 31, 2013)