Kolkata: The city's air quality continues to show a predictable seasonal pattern—temporary relief during monsoon months followed by severe deterioration in winter—with little sustained improvement over the past three years, according to official data shared in Parliament and findings from a recent National Clean Air Programme (NCAP) study.
The issue came up in the Rajya Sabha after BJP MP from West Bengal Samik Bhattacharya sought details on whether the Central Pollution Control Board (CPCB) was monitoring Kolkata's Air Quality Index (AQI) and whether a source apportionment study had been conducted for the city. In a written reply, Union minister of state for environment Kirti Vardhan Singh said the CPCB, in coordination with the West Bengal Pollution Control Board (WBPCB), regularly monitors ambient air quality and that a source apportionment study was completed in 2025.
Average AQI data for 2023, 2024 and 2025 reveal a consistent trend of high pollution levels during winter months, partial improvement during the monsoon, and a steady rise in pollution from Oct onwards. Jan remains the most polluted month across all three years, with AQI levels touching 225 in Jan 2023 and 2024, before easing slightly to 172 in Jan 2025.
While air quality improves during the summer and monsoon months—particularly between June and Sept, when AQI levels often fall below 60—this relief is short-lived. Pollution levels begin rising sharply in the post-monsoon period, peaking in Nov and Dec. In Dec2025, the AQI surged to 202, the highest Dec reading recorded in the three-year period, pointing to a worsening winter pollution trend.