Delhi overtakes Lahore as smog drives severe air readings

Delhi overtook Lahore as the world’s most polluted major city on Friday, as dense smog reduced visibility and air-quality readings reached hazardous or severe levels under two different measurement systems.

IQAir, a Swiss air-monitoring group, reported Delhi’s air quality index at 334 and ranked the city first among major cities worldwide. India’s Central Pollution Control Board recorded an average reading of about 403 and classified it as severe. The figures are not directly comparable because the systems use different scales and methods.

CPCB data showed 33 of Delhi’s 58 monitoring stations in the severe category on Friday, with several readings above 450. The board’s severe classification covers readings from 401 to 500. IIT Delhi recorded an AQI of 487, while Chandni Chowk and North Campus each registered 476, according to the station-level data.

The city’s average CPCB reading had risen from 299 on Tuesday, November 10, to 313 on Wednesday and 350 on Thursday, November 12. The deterioration followed a brief improvement earlier in the week, with pollution levels rising after Diwali celebrations on November 8.

The India Meteorological Department forecast that Delhi’s AQI would...