Delhi, Kolkata, and other urban centres see alarming pollution spikes, with experts urging stronger action to tackle air quality crisis nationwide

India’s major cities have faced a dramatic increase in air pollution levels this winter, with Delhi remaining the most polluted megacity, according to a new analysis by the Centre for Science and Environment (CSE). The think tank’s report sheds light on the severity of the pollution crisis, urging immediate, more aggressive measures to address the nation’s air quality challenges.

Delhi, infamous for its poor air quality, recorded a staggering average PM2.5 concentration of 175 micro grams per cubic metre (µg/m³) during the 2024-25 winter, far surpassing the safe threshold for air quality. The national capital endured 8 days of ‘severe plus’ air quality, 12 days of ‘severe’ AQI, and 68 days of ‘very poor’ air quality. In a particularly alarming event, PM2.5 levels peaked at 602 µg/m³ on 18 November, marking the worst daily pollution levels in four years.

Kolkata ranked second among the most polluted megacities, with an average PM2.5 of 65 µg/m³, while other major urban centres such as Hyderabad, Mumbai, Bengaluru, and Chennai also saw significant pollution increases. Despite relatively better climates, localised pollution hotspots in cities like Mumbai, Chennai, and Bengaluru experienced spikes as much as 60% above citywide averages.

The report highlighted the troubling fact that air quality across all six cities worsened despite their diverse climatic conditions. In particular, Kolkata and Delhi, situated in the Indo-Gangetic Plain, saw the highest pollution levels. Meanwhile, cities like Hyderabad, Mumbai, Chennai, and Bengaluru recorded localised pollution peaks, despite their comparatively more favorable climates.

Long-term trends reveal mixed results, with some cities showing a slight decline in winter pollution compared to last year. Delhi saw a 7 per cent reduction from the previous winter, but it still remained 5 per cent worse than two years ago. Hyderabad, in contrast, showed the most significant improvement, with a 51 per cent drop in its peak winter pollution levels, while Bengaluru followed with a 42 per cent decline.

Despite the implementation of the National Clean Air Programme five years ago, air quality improvements have been slow, and many cities still fail to meet national clean air standards. The report underscored the urgent need for comprehensive action to address the root causes of air pollution and safeguard public health across the country.