Delhi Reclaims World's Most Polluted Capital Amid Surge in Winter Pollution

The megacities of India experienced a surge in air pollution during the winter of 2024-25 with Delhi topping the charts recording highest level of pollution during winter, according to a study by Centre for Science and Environment (CSE).

The study revealed that other urban centres including Kolkata, Mumbai, Chennai, Hyderabad and Bengaluru also recorded major pollution spikes during the winter period.

Delhi recorded an average fine particulate matter (PM) 2.5 concentrations of 175 micrograms per cubic metre (µg/m³) this winter exceeding the safe air quality limits by a large margin. The capital city registered eight days of ‘severe+’ air quality, 12 days of ‘severe’ Air Quality Index (AQI) and 68 days of ‘very poor’ AQI. The capital experienced no ‘good’ air quality days with peak pollution reaching 602 µg/m³ on November 18, 2024, marking the worst daily PM 2.5 level in four years.

According to the study, Kolkata ranked second among the mega cities with a winter PM 2.5 average of 65 µg/m³, followed by Hyderabad (52 µg/m³), Mumbai (50 µg/m³), Bengaluru (37 µg/m³) and Chennai (36 µg/m³).

Despite these statistics, the study indicated that worst affected locations within megacities recorded pollution levels rising as much as 60% above citywide averages. Mumbai, Chennai and Bengaluru saw the fastest worsening of localised pollution levels, stated the study.

“The peaking of pollution during winter in any climatic zone is a sign of the underlying problem of persistent air pollution in these rapidly urbanising and motorising cities. The growing impact of local sources of pollution shows up in the pollution hotspots across these cities, increasing local exposures and risks,” said Anumita Roychowdhury, Executive Director, Research and Advocacy, CSE.

Delhi as World’s Most polluted Capital

According to another study titled 2024 World Air Quality Report published by IQAir on March 11, Delhi became the most polluted capital city in the world with an average  PM 2.5 concentration of micrograms per cubic metre (µg/m³).

According to the report, 13 out of the 20 most polluted cities in the world are in India with Byrnihat on the Assam-Meghalaya border being the most polluted metropolitan area of 2024, with an annual average PM2.5 concentration of 128.2 µg/m3.

The region of Central & South Asia was home to the top seven most polluted cities in the world. India was home to six of the nine most polluted global cities.

India is the fifth most polluted country in the world, with an average Air Quality Index (AQI) of 50.6 μg/m3 – 10 times higher than the World Health Organization’s (WHO) annual PM2.5 guideline value of 5 μg/m3. In 2023, it was the third most polluted country, reported The Indian Express.