As India's north continues to struggle with extreme pollution levels, the story has put a fresh spotlight on air quality in cities across Asia.Beijing has long been notorious for its smog - but statistics show that India, Pakistan and Bangladesh have worse air by far, reports BBC.
So why is South Asia so much more polluted?
Asia's most polluted cities
Of the world's most polluted 30 cities, 22 are in India, according to research by IQ AirVisual, a Swiss-based group that gathers air-quality data globally, and Greenpeace.
The remaining eight cities are all in Pakistan, Bangladesh and China - but the list doesn't include Beijing, which comes in at number 122.
Today, pollution levels in Europe, Australia and the US are significantly lower than the extreme readings that India has experienced in the past few days.