Cities across China have been experiencing heavy air pollution in early November. One tenth of the land territory has been blanketed by heavy smog.

Most affected are the northern and northeastern areas. Seven provinces and municipalities, including Beijing and Tianjin, have seen different levels of pollution.

On Thursday, Beijing issued an orange alert for smog. Visibility in some areas had dropped to below 100 meters. Flights were delayed and cancelled. In Baoding, Hebei province, the PM 2.5 Index peaked at a severely hazardous level of 326 points on Friday.

The Air Quality Index even reached 500 in the cities of Suihua, Harbin and Daqing in the Northeast provinces over the last days. The Ministry of Environmental Protection had already sent in 12 inspection teams. The ministry says excessive toxic emissions, coal and large-scale straw burning are the major causes of the pollution.