Delhi's air quality deteriorated sharply into the severe category on Friday, with the national capital recording a city-level Air Quality Index of 403 according to the Central Pollution Control Board. Thirty-three of 58 monitoring stations reported readings above 400, while PM2.5 remained the dominant pollutant.

The Swiss group IQAir listed Delhi at a hazardous 334 on its scale, placing the city ahead of Lahore, Pakistan, as the world's most polluted major city. India's CPCB scale rated conditions more severely than the international measure due to differences in methodology.

Several locations posted extreme readings early Friday. IIT Delhi reached 488, Chandni Chowk hit 479 or higher in morning reports, and North Campus of Delhi University recorded 478. Other sites including Pusa, Punjabi Bagh, and Burari Crossing exceeded 450.

Conditions across the National Capital Region also worsened. Noida reported an AQI near 365 to 474 depending on the hour, while Gurugram, Greater Noida, and Faridabad stayed in the very poor range.

The spike followed Diwali celebrations and stemmed from an elevated pollution baseline combined with firecracker emissions, agricultural burning in neighboring states, and stagnant meteorological conditions that trapped particulates near the surface. Transport contributed roughly 18.5 percent of the load according to the Decision Support System.

Visibility dropped across the city under a thick smog layer, prompting respiratory complaints from residents. The India Meteorological Department forecast very poor to severe air quality persisting through at least November 16.

Delhi has faced recurring winter pollution episodes driven by seasonal factors and urban activity. Authorities continue to monitor stations in real time while the public faces heightened health risks, particularly for children and the elderly.