Winter has come to Delhi and with it, a familiar sense of gloom. The sky here is grey and there is a thick, visible blanket of smog. If you stay outdoors for more than a few minutes, you can almost taste ash. You will feel breathless within minutes if you try to run or even walk at a brisk pace in the smog.

India's pollution control authority said the national capital territory's 24-hour air quality index (AQI) reading was at 484, classified as "severe plus", the highest this year.

Residents in India's northern states woke up to another day of poor air quality on Tuesday, as a layer of dense fog shrouded most of the region, and pollution in the capital Delhi remained severe. India battles air pollution every winter as cold,