This story is part of CBC News special coverage of climate change issues in connection with the United Nations climate change conference (COP21) being held in Paris from Nov. 30 to Dec. 11.
Beijing blanketed in worst smog of the year
While Chinese President Xi Jinping joined other world leaders in Paris for climate talks, schools in Beijing kept children indoors, highways closed and factories scaled back work because of thick, smelly smog that cut visibility to mere metres in the Chinese capital on Monday.
The matter with atmospheric particulate matter
The concentration of hazardous particulate matter (known as PM2.5 particles) in the air exceeded 600 micrograms per cubic metre in places inside Beijing's urban centre, while readings as high as 976 micrograms were recorded at monitoring sites in some suburban areas.
Red alert too disruptive
Critics inside the country say authorities held back from issuing a red alert because China's highest warning is too disruptive, requiring at least half of the vehicles on highways to be pulled off the road and the suspension of schools.
Winter is worst for air pollution
An early cold snap in November meant winter heating — much of which is generated by coal-fired plants and wood fires for many poorer residents — was contributing to a worsening of air quality, which deteriorated over the weekend.
Winter is coming to New Delhi, too
Indian Prime Minister Narendra Modi left similar conditions in New Delhi as he departed for the Paris climate summit.
The Indian capital, which typically suffers a deterioration of air quality in the winter, was blanked in a particularly thick cloud of hazardous, choking smog on Monday.
Too little, too late?
Initiatives to clean up Delhi's air have hit roadblocks in the past. A directive this year to ban all vehicles older than 15 years has been delayed and previous city governments have often ignored court orders to address pollution woes.