According to a report, 18 of the 20 most polluted cities in the world are in India alone, where air pollution has historically increased between 2010 and 2019 and there has also been an alarming increase in PM 2.5 levels. 18 cities of India who dream of becoming Vishwaguru have become pollution gurus. In the list of world's most populous cities, Delhi is most polluted with PM 2.5. Watch this video to know more.