Kolkata sees worst Oct in 8 years as AQI deteriorates sharply this festive season
Times of India | 6 November 2025
Kolkata: Kolkata's Oct air quality has worsened over the years, with experts fearing a troubling winter ahead. The city's all-out fireworks revelry this festive season has left a toxic imprint on the atmosphere, making Oct 2025 one of the worst months for air quality in recent memory.
An analysis by the Centre for Research on Energy and Clean Air (CREA) reveals that the city's Oct 2025 PM2.5 air pollution levels deteriorated sharply, ranking among the dirtiest in the past eight years.
Environmental experts say the worrying trend is not just about post-Diwali pollution spikes. Oct's baseline deterioration signals what may be an even harsher winter pollution scenario. With temperatures dropping and the seasonal inversion of the ambient air layer beginning to take effect, pollutants are expected to become trapped closer to the ground, increasing health risks for Kolkata's already vulnerable population.
According to CREA's analysis of the CPCB dataset, the number of "Good" and "Satisfactory" air-quality days in Oct has sharply declined in recent years, while "Moderate" and "Poor" days have risen. In 2025, Kolkata recorded eight Good, 15 Satisfactory, and eight Moderate days. While that may seem balanced at first glance, the noticeable shift is the shrinking number of clean-air days compared to earlier years such as 2020, 2021, and 2022.
The spike in post-festivity pollution, coupled with incessant firecracker use, pushed Oct 2025 into the category of one of the most polluted months since 2018. The city saw multiple days veering towards the "Poor" category—an indication of rising PM2.5 levels even before the peak winter months.
A deeper look at the eight-year air-quality matrix reveals critical shifts. The cleanest Oct in the dataset was 2020 (pandemic-lockdown year with a very tepid Diwali celebration), with 14 Good and 13 Satisfactory days—coinciding with Covid-19 restrictions and reduced mobility.
"Winter and festive periods don't just create India's pollution problem, they expose it. These seasonal spikes merely amplify baseline pollution levels that remain dangerously high throughout the year. This predictable surge is substantially preventable if we prioritise sector-specific emission cuts with clear accountability mechanisms. Instead, policy responses remain reactive and seasonal, failing to address the year-round sources driving this crisis," said Manoj Kumar, analyst at CREA.