Levels of pollution have soared past the levels considered hazardous by the World Health Organisation, as dense smog hangs over Beijing and 30 other cities in northern and eastern China.
Chinese media say that although some of the smog can be attributed to wintry weather conditions, the human contribution is one of the biggest factors.
Tabloid the Global Times said China was risking serious long-term environmental damage, while the official People's Daily referred to the low visibility as a 'suffocating siege'.
British expats in Beijing say although air pollution is 'nothing new' in the city, the most recent levels of smog have shocked even long-term residents.
The noxious haze in Beijing thickened on Thursday and is expected to linger until the middle of this week.
As for the cause, experts and the media alike have differing theories.
Beijing's online community, along with state-run media outlets, have called for a reduction in the number of vehicles on the city's roads.
Health experts say that the current smog levels are not necessarily due to an increase in pollutant particles, more a lack of wind in dispersing the haze.
The China Daily said there are also not enough 'green areas' in the city 'to help soak up the fumes discharged by vehicles and industries'.
There has also been rapid industrialisation in China and a heavy reliance on coal power, which have both contributed to the problem.
Coupled with Beijing's enormous rise in car ownership (5 million vehicles and rising) and a blase attitude towards environmental laws, and it is easy to see how air pollution has spiralled out of control.
China Daily produced an unusually outspoken editorial in which they said Beijing residents should use their cars less and governments officials should also reduce vehicle use to lower emissions.
Experts say it may take years to properly tackle the smog in Beijing, as a lot of it is blown in from heavily-industrialised areas surrounding Beijing.