NEW DELHI: This winter, Kolkata and Hyderabad turned out to be the most polluted cities after Delhi, while Mumbai, Chennai and Bengaluru saw the fastest worsening of localised pollution levels. Delhi, with a winter average PM2.5 level of 175 microgramme per cubic metre (µg/m³) remained the most polluted megacity by a wide margin, according to an analysis released on Tuesday.

Notably, four of the six most polluted locations among the 68 monitoring stations across five megacities were in Mumbai, while the remaining two were in Kolkata. In Chennai, Alandur and Manali emerged as the most polluted areas, both recording a seasonal PM2.5 average of 47 µg/m³.

Alandur experienced 14 days of ‘poor’ and ‘very poor’ AQI, while Velachery recorded 7 days.

While the 2024-25 winter average has shown improvement over the previous winter, the Centre for Science and Environment analysis found that PM2.5 pollution in the national capital declined in the 2024-25 winter (October 1 to January 31) compared to the 2023-24 winter (189 micrograms per cubic metre).

When compared to the citywide average, pollution levels in the worst-affected locations within each megacity were significantly higher. Chennai saw a 30% increase, while Bengaluru recorded a 51% rise. Mumbai experienced the highest disparity, with pollution levels 60% higher than the citywide average. In Hyderabad, the worst-affected location had 19% higher pollution, whereas Kolkata and Delhi recorded increases of 23% and 30%, respectively.