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Even as Delhi is considered to be the most polluted city in India and every year courts and governments discuss over stubble burning and vehicle emissions as the main source, surprisingly, it is not the most polluted city, at least in October 2025. The latest study by the Centre for Research on Energy and Clean Air (CREA) revealed that Delhi is ranked as the sixth most polluted city in India in October 2025, ahead of which are its neighbouring cities like Ghaziabad and Noida. Which is the most polluted city? CREA’s study involved factors like continuous ambient air quality monitoring data, which pointed out an alarming decline in air quality across the country, with the Indo-Gangetic Plain, particularly the National Capital Region (NCR), witnessing the sharpest declines. Among the most polluted cities, Haryana’s Dharuhera ranked first during October 2025, with an alarming average PM2.5 concentration of 123 g/m, greatly surpassing the National Ambient Air Quality Standard (NAAQS) on around 77% of the days. The city saw two ‘Severe’ and nine ‘Very Poor’ air quality days, highlighting the consistent pollution crisis. During the same time, Delhi's monthly average PM2.5 level stood at 107 g/m, making it almost thrice that of its September average of 36 g/m, underlining a continuous, fast, and shocking rise in air pollution. Other Top 10 most polluted cities? According to official data, stubble burning contributed to less than 6 per cent of Delhi’s PM in October, but the massive rise in pollution last month was a result of emission sources throughout the year, suggesting that short-term seasonal measures like the Graded Response Action Plan (GRAP) have limited impact. This also suggests that the government needs to opt for strong and long-term mitigation strategies to fight emissions from vehicles, industries, and construction activities. The top 10 most polluted cities also included other cities around Delhi like Rohtak, Ghaziabad, Noida, Ballabgarh, Bhiwadi, Greater Noida, Hapur, and Gurgaon, most parts of the NCR region, and the neighbouring states of Haryana and Uttar Pradesh. On the other hand, Meghalaya's capital city of Shillong was ranked as the cleanest city with an average PM2.5 concentration of just 10 g/m. Karnataka and Tamil Nadu were also among the list of cleanest cities. However, although 212 out of 249 cities recorded PM2.5 levels which is within India's NAAQS limit of 60 g/m, only six cities aligned with the World Health Organisation’s daily safe guideline of 15 g/m.
