Winter pollution crisis in megacities of India: Going beyond Delhi Chennai

March 18, 2025

The winter air quality in Chennai has remained largely stable compared to previous years, according to a new analysis by the Urban Lab at the Centre for Science and Environment (CSE). The city’s seasonal average PM2.5 concentration for winter (October 1, 2024 – January 31, 2025) was recorded at 36 µg/m³—just 1.2 per cent higher than the average of the past three winters. The highest daily PM2.5 level this season was observed on October 31, 2024, at 119 µg/m³, reflecting a 19 per cent decline compared to past winter peaks. However, individual monitoring stations saw significant variations, with Velachery recording the highest daily peak of 193 µg/m³.

Despite the relatively low seasonal average, winter pollution levels across Chennai’s monitoring stations surged well above annual averages, with increases of 3–40 per cent. Arumbakkam, Royapuram, and Perungudi saw the sharpest seasonal rise of over 35 per cent compared to their annual levels. The impact of winter pollution was evident in the number of poor air quality days—Alandur experienced the highest with 14 days classified under ‘poor’ and ‘very poor’ AQI categories.