New Delhi: The Air Quality Index (AQI) in Delhi reached 280 according to the Central Pollution Control Board. The 24-hour average on Monday was 239, as per the Board.

Low wind speeds for the next three days are likely to reduce ventilation and AQI is expected to worsen to ‘upper end of poor’ or ‘lower end of very poor’. Air quality has also reduced in the vicinity of Delhi's Lodhi Road, Mathura Road, IITs and airports.

An AQI between zero and 50 is considered “good”, 51 and 100 “satisfactory”, 101 and 200 “moderate”, 201 and 300 “poor”, 301 and 400 “very poor”, and 401 and 500 “severe”. The air quality in Delhi, according to a WHO survey of 1,650 world cities, is the worst of any major city in the world.

The index however is likely to improve from February 17, the Pollution Control Board said, owing to moderate wind speed.