Air pollution choking New Delhi has ground outdoor work to a halt and disrupted air travel in the Indian capital.

A sharp spike in Delhi's air pollution was witnessed in the past 24 hours with 30 out of 36 monitoring stations reporting a severe air quality index.

Visibility fell sharply in Delhi this week as a toxic mixture of smoke and fog shrouded the Indian capital even before winter sets in. Here is a look at the problem, and what triggered it. HOW BAD WAS THE SMOG?

Air quality deteriorated to hazardous levels in New Delhi on Wednesday as toxic smog blanketed India, leaving residents of the capital complaining of “apocalyptic” scenes. The crisis also affected neighbouring Pakistan,