This article is more than 6 years old

This article is more than 6 years old

Beijing's skyscrapers receded into a dense gray smog on Thursday as the capital suffered the season's first wave of extremely dangerous pollution, with the concentration of toxic small particles registering more than two dozen times the level considered safe.

The air took on an acrid odour and many of the city's commuters wore industrial strength face masks as they headed to work.

The city's air quality is often poor, especially in winter when stagnant weather patterns combine with an increase in coal-burning to exacerbate other forms of pollution and create periods of heavy smog lasting days. But the readings early on Thursday for particles of PM2.5 pollution were the first of the season above 500 micrograms per cubic metre.

The density of PM2.5 was about 350 to 500 micrograms and had reached as high as 671 at 4am at a monitoring post at the US embassy in Beijing. That is about 26 times as high as the 25 micrograms considered safe by the World Health Organisation and was the highest reading since January 2013.

Serious air pollution plagues most major Chinese cities, where environmental protection is sacrificed for the sake of economic development. Coal burning and emissions from automobiles have been major sources of pollution. In recent years China has beefed up regulations and pledged financial resources to fight pollution.

In the far northeastern city of Harbin, some monitoring sites reported PM 2.5 rates of up to 1,000 micrograms per cubic metre in October when the winter heating season began.

In December dirty air smothered the coastal city of Shanghai and its neighbouring provinces for days, with the density of PM 2.5 exceeding 600.

Beijing authorities said the haze on Thursday reduced the visibility to several hundred metres and the severe pollution was likely to continue through Friday.