On Friday, 86 of the 100 most polluted cities globally were in India. As HT reported earlier, Delhi’s air quality deteriorated sharply on Thursday, with the city’s PM2.5 concentration more than doubling in 24 hours. Delhi's air quality plunged into the severe category for the first time this season on Friday morning, with the national capital recording an average AQI of 403. The Air Quality Index stood at 403.