60 cities were affected by a bout of severe air pollution in the Beijing and Tianjin areas during the weekend, triggering the first use of a new warning system in the Beijing-Tianjin-Hebei region.

The unified grading system was adopted at the end of October to standardise air pollution warning systems in all three cities, which used different warning systems. The four-tier system uses red to represent the most severe air quality, followed by orange, yellow and blue.

air pollution
The AQI on Monday morning. Photo: aqicn.org

Red alerts are issued if the Air Quality Index (AQI) is predicted to reach 500 and last for over a day, or if the AQI is predicted to be higher than 200 for three days in a row.

Between Friday and Sunday, red warnings were raised in nine cities in Hebei. Orange warnings were raised in 24 cities including Beijing and Tianjin, yellow warnings were raised in 22 cities in Henan, and five blue warnings were issued in Shandong province, according to state-backed news outlet The Paper.

Construction halted

The Beijing Municipal Environmental Protection Bureau cited a rise in temperature and humidity and mainly southerly winds as reasons for the poor dispersal of the smog.

It called for a halt to demolitions, earthworks, concrete pouring, and other construction activities to mitigate the smog on Friday. Inspections on construction sites, industrial enterprises and high-emission vehicles were carried out in the capital, The Paper reported.

beijing pollution
A woman wears a mask in Beijing on Saturday. Photo: HKFP.

Visibility decreased to one to two kilometres, with visibility of less than 500 metres in some parts of the city. Several highway sections were closed in Hebei to reduce traffic, and some flights flying to and out of Tianjin were delayed due to the smog.

The Ministry of Environmental Protection sent inspection units to Hebei and Shandong to inspect the response of local governments and small enterprises, The Paper reported.

The air in Beijing improved on Monday as a cold front cleared the smog.

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Catherine is a Canadian journalist and photographer who lived in Beijing for almost two years, working in TV and online media. Aside from Hong Kong and mainland affairs, she is also interested in urban spaces, art and feminism. She holds a BA in Literature and Art History from the University of British Columbia.