New | Colour rev-pollution: China’s big cities see grey smog, purple haze and record red alerts

More than a dozen Chinese provinces and major cities have been smothered in the worst smog for least six months over the last few days.

Air quality had been hazardous in Beijing, Tianjin (天津), Hebei (河北), Henan (河南), Shanxi (山西), Shaanxi (陝西), Shandong (山東), Jiangsu (江蘇), Shanghai, Anhui (安徽), Zhejiang (浙江), Liaoning (遼寧), Jilin (吉林) and Heilongjiang (黑龍江), a China Meteorological Administration news portal said on Thursday.

READ MORE: Heavy smog to cloak northern China until cold front moves in

On Tuesday, Tianjin issued its first red alert, which was due to stay in effect until 6pm today.

In all, 17 Shandong cities were on high pollution alerts and roughly 7,500 inspectors had been sent to factories and building sites to assess emergency efforts to improve air quality, Shandong’s environmental protection administration said.

Chief CMA forecaster Ma Xuekuan said the smog in the north and east was expected to disperse by Saturday with the arrival of a strong cold front.

In Beijing, residents woke to polluted grey skies that did not clear until 2pm.