Kolkata: The city has emerged as the third most-polluted state capital in India during the winter of 2025–26 in terms of average PM2.5 concentration, according to an analysis by Centre for Research on Energy and Clean Air (CREA). Delhi emerged as the most polluted megacity with winter PM2.5 concentration of 163 µg/m³, followed by Bhubaneswar at 81 µg/m³. Kolkata recorded an average PM2.5 concentration of 78 µg/m³ during the Oct–Feb period.
The findings are part of CREA's winter air quality analysis based on data from continuous ambient air quality monitoring stations (CAAQMS) operated by the central pollution control board between Oct 1, 2025, and Feb 28, 2026.
In Kolkata, winter PM2.5 levels fluctuated over the past five years but remained well above India's national ambient air quality standard (NAAQS) of 40 µg/m³. The data show that after a dip last winter, pollution levels rebounded this season, placing the city significantly above the national limit.
Across India, the CREA analysis found that winter air pollution worsened in many cities. Of 238 cities with sufficient monitoring data, 204 recorded winter average PM2.5 concentrations above the national standard, up from 173 in the winter of 2024–25. None of the analysed cities met World Health Organization's much stricter guideline of 5 µg/m³.
Mumbai and Chennai also exceeded the national standard with winter averages of 48 µg/m³ and 44 µg/m³, respectively. Bengaluru was the only capital to stay within the national limit, with average PM2.5 concentration of 39 µg/m³.
The study also found widespread pollution across India's National Clean Air Programme (NCAP) cities. Of the 96 NCAP cities with adequate data, 84 exceeded the national PM2.5 standard.
In the Indo-Gangetic Plain — one of the world's most polluted regions — 75 of 79 monitored cities recorded PM2.5 levels above the national standard during winter 2025–26.
CREA analyst Manoj Kumar said the findings indicate persistent and widespread non-compliance with air quality standards. "While the commission for air quality management set PM2.5 reduction targets for NCAP cities, similar nationwide targets are needed, with stronger controls on gaseous pollutants like sulphur dioxide, nitrogen dioxide, and volatile organic compounds that contribute to secondary PM2.5 formation," he said.
The analysis also ranked Ghaziabad as the most polluted city with an average PM2.5 concentration of 172 µg/m³, followed by Noida at 166 µg/m³. On the other hand, Karnataka's Chamarajanagar emerged as the cleanest city, with an average PM2.5 concentration of 19 µg/m³ during this winter.