Kolkata: Winter is yet to set in, but Kolkata has already exceeded its annual PM10 pollution level. An analysis of air-quality monitoring data by CREA (Centre for Research on Energy and Clean Air) has revealed that the city accumulated enough particulate pollution by mid-Oct to breach India’s annual air-quality benchmark — 60 µg/m³ — even if its air were to remain completely free of PM10 for the rest of the year.This has led to fears of a more polluted winter.The findings suggest that Kolkata is entering its most pollution-prone months with an already excessive burden of airborne particles, raising fresh concerns over the city’s deteriorating air quality.According to an analysis by CREA’s lead researcher Manoj Kumar, based on Central Pollution Control Board (CPCB) continuous monitoring data, Kolkata’s average PM10 concentration between Jan 1 and Oct 16 stood at 76 micrograms per cubic metre (µg/m³), up from 72 µg/m³ during the corresponding period in 2025. This represents an increase of nearly 6%, reversing the improvement observed over previous years.India’s National Ambient Air Quality Standards prescribe an annual PM10 limit of 60 µg/m³. The World Health Organization’s recommended annual guideline is considerably stricter, just 15 µg/m³. Kolkata’s average concentration during the study period was therefore more than five times the WHO guideline.The CREA researchers adopted an unusual approach to illustrate the accumulated pollution burden. They calculated the cumulative PM10 concentration recorded since Jan 1 and divided it by 365 days. The date on which this figure reached 60 µg/m³ was identified as the point when a city’s annual pollution allowance had effectively been exhausted.Delhi crossed this threshold within the first four months of 2026, followed by Bengaluru in late Sept and Kolkata in mid-Oct. Chennai and Mumbai were approaching the same benchmark when the analysis ended.For Kolkata, the timing is particularly worrying. The city typically sees its sharpest deterioration in air quality between Nov and Feb, when falling temperatures, weaker winds and reduced atmospheric mixing let pollutants accumulate closer to the ground.This means Kolkata has entered the winter pollution season having already accumulated enough PM10 to push its full-year average to the national limit.The findings also challenge the tendency to judge air quality primarily through daily AQI readings or exceptionally polluted winter days. The cumulative exposure experienced throughout the year is equally important for assessing long-term health risks.
