Diwali, derived from the word “Deepavali,” meaning “a row of lights,” is typically celebrated by socializing and exchanging gifts. The dates of the festival are based on the Hindu lunar calendar, typically falling in late October or early November. Shoppers crowded markets to buy flowers, lanterns and candles.

New Delhi is one of the world’s most polluted cities, and the celebrations for the festival of Diwali herald its worst months as cooler air laden with smog is trapped over the city, reducing visibility and raising serious health risks for the more than 30 million people who live in the capital and its metropolitan region.