Delhi Most Polluted City in 2024-25, Patna Second: Climate Trends Study

• Delhi recorded the highest annual PM2.5 levels and prolonged 'severe' air quality in winter, making it the most polluted city in 2024-25.
• Patna emerged as the second most polluted city, experiencing persistently high PM2.5 concentrations, particularly in the eastern Indo-Gangetic Plain.
• Mumbai and Chennai saw increased annual average pollution levels in 2025, indicating a growing year-round air quality concern.
• Bengaluru and Chennai also showed signs of air quality deterioration during winter months, a new vulnerability trend.
• IIT Delhi expert Sagnik Dey called for NCAP reforms, including separate winter targets and meteorology-adjusted metrics, to improve policy effectiveness.