India, Dec. 24 -- The air quality forecast failed as Delhi's AQI slipped into the 'severe' category above 400, with the national capital and neighbouring Noida recording the worst air quality in the country.

A grey haze enveloped the capital on Tuesday as the 24-hour average Air Quality Index (AQI) stood at 412 in the severe category at 4 pm, deteriorating sharply from 373 in the very poor category at the same time a day earlier, according to data from the Central Pollution Control Board (CPCB).

Out of the 40 functional monitoring stations in the city, five recorded severe-plus AQI levels above 450, including Nehru Nagar (465), Mundka (457), Chandni Chowk (453), Okhla (452) and Jahangirpuri, while 26 stations remained in the severe cate...