PM 2.5 in 2024-25 winter Kolkata's best since 2019

Time of India

26-05-2025

Kolkata: This winter brought a breath of relatively cleaner air to Kolkata, with the city recording its best particulate pollution levels since 2019. Data from a six-year analysis by West Bengal Pollution Control Board (WBPCB) painted a picture of cautious optimism.
Dec 2024 saw the PM2.5 level drop to 73 µg/m³, the lowest in recent years, followed by 77 µg/m³ in Jan 2025. These are the best readings in Kolkata for these months since the beginning of the dataset in 2019.
However, even with the notable dip, the PM2.5 concentration during the peak pollution months of Dec and Jan continued to exceed the national safe limit of 40 µg/m³.
PM2.5 refers to fine particulate matter with a diameter of 2.5 microns or less.
They are tiny enough to penetrate deep into lungs and enter the bloodstream, contributing to respiratory and cardiovascular illnesses. Winter months typically see a spike in PM2.5 due to a combination of lower wind speeds, temperature inversions, and increased emission from vehicles and biomass burning.
While the reduction in average concentration levels signals progress — likely driven by stricter vehicular emission norms, cleaner fuels, and increased public awareness — the city is still far from achieving truly breathable air, experts warned.
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The peak pollution year was 2020-21, coinciding with the post-lockdown reopening of industries and transport after the first Covid-19 wave. During that winter, Dec and Jan saw exceptionally high PM2.5 levels of 140 µg/m³ and 131 µg/m³, respectively. Since then, gradual improvement was observed.
Summer and monsoon months of April-Sept generally showed cleaner air, aided by factors like rainfall. July recorded the lowest pollution levels across all years, dropping to 13 µg/m³ in 2023-24.
However, the summer period appears to have hit a plateau, with no significant air quality gains in recent years.
The data highlights that while regulatory efforts and better public awareness seem to be contributing to declining winter pollution, Kolkata's air quality remains vulnerable because of constant construction activities and increasing automobiles. Experts warned that without sustained intervention, like promotion of green transport, clean energy, and emission controls, the progress may be short-lived.
"The pandemic gave us a brief moment of cleaner air but the real challenge lies in making those improvements permanent. The transboundary pollution often undoes our clean air efforts, particularly in winter months. Winters still pose health risks, especially for vulnerable populations," said WBPCB chairman Kalyan Rudra.