With the Chinese capital, Beijing's first ever pollution ''red alert'' coming into effect, schools have closed and outdoor construction has come to a halt. The alert, the highest possible warning level, was sounded yesterday and would last until midday on Thursday.
China, the world's worst polluter, has placed limits on car use and has ordered a number of factories to stop operations. China is currently engaged in talks on carbon emissions in Paris.
This is the first time a red alert was declared under the four-tier alert system, which was adopted a little over two years ago, although pollution levels were nowhere near the city's worst.
When the alert went into effect at 7:00 local time today, (23:00 GMT Monday), according to the US Embassy's air pollution monitor in Beijing the intensity of the tiny particles known as PM 2.5 was at 291 micrograms per cubic metre.
It dropped very slightly to 250 by 11:00, still a level described as "very unhealthy". The suburbs saw levels of the poisonous particles in the suburbs at several times that number.
The safe level had been pegged by the World Health Organization at 25 micrograms per cubic metre.
Meanwhile, in a reversal of trading patterns, Cambridge Mask Company in the UK is making pollution masks and selling them to China, where such items are widely seen in Beijing's streets.
Christopher Dobbing, CEO of the company, told Reuters in a television interview that he spotted a gap in the market due to "the Beijing cough", a reaction to pollution familiar to many visitors.
The idea was to make quality British goods needed in the country and yesterday, Beijing's pollution seemed to be favouring the company's plan.
The Cambridge company was, however, not the only one to produce masks for China, but, according to Dobbing, he had a unique selling point.
"If you look to China they really like British products. It may sound silly but 160 million people watched the last season of Downton Abbey and so there's just this natural affinity with British products and Britishness," he said.
According to the company, carbon filters, as used by the UK military and sewn into the masks, eliminated 99 per cent of viruses, bacteria and pollution.
"The carbon material we use is about a 100 times more expensive than other carbon cloths that you could use. So it costs us a lot to make a mask, particularly in Britain," Dobbing said.
"But, as I say we get a really good combination of quality labour and quality materials that means we come out with a really good quality mask."