Air quality in Chennai worsened in 2025, with PM2.5 pollution levels increasing across all seasons compared to 2024, according to a new analysis examining pollution patterns in major Indian cities.
The study titled ‘Meteorology-Driven Persistence of PM2.5 Pollution in Indian Cities’ analysed daily air quality data from 2024–2025 across six cities — Delhi, Patna, Kolkata, Mumbai, Chennai, and Bengaluru — using Central Pollution Control Board (CPCB) monitoring records.
In Chennai, the annual average PM2.5 concentration rose from 27.5 µg/m³ in 2024 to 30.5 µg/m³ in 2025, marking an increase of about 10.9%, the report found.
The increase was most pronounced during winter. Seasonal average PM2.5 levels rose from 37.8 µg/m³ in winter 2024 to 45.7 µg/m³ in winter 2025, indicating deteriorating air quality during the colder months. Summer pollution also increased slightly from 21.3 µg/m³ to 23.9 µg/m³, while monsoon levels remained largely stable at around 21 µg/m³. Post-monsoon pollution rose from 34.1 µg/m³ to 36 µg/m³.
Monthly data further highlighted the trend. In 2025, December recorded the highest PM2.5 average at 53.7 µg/m³, followed by January (46.8 µg/m³) and November (43.5 µg/m³). In contrast, pollution levels during summer and monsoon months generally stayed between 20–26 µg/m³.
