Of the world's top 10 cities with the worst air quality, three -- Delhi, Kolkata and Mumbai, are in India, data from air quality and pollution city tracking service from IQAir, a Switzerland-based climate group showed.

While Delhi's Air Quality Index (AQI) at 556 made it to the top of the list, Kolkata and Mumbai recorded an AQI of 177 and 169, respectively, at fourth and sixth position, on the list.