Guwahati: Byrnihat has emerged as the most polluted city in India during the first half of 2025, surpassing Delhi, according to a new analysis by the Centre for Research on Energy and Clean Air (CREA).
The analysis revealed that Byrnihat recorded an average PM2.5 concentration of 133 µg/m³, significantly above the national ambient air quality standard (NAAQS) of 40 µg/m³. In comparison, Delhi reported an average PM2.5 level of 87 µg/m³ — more than twice the national limit.
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Other cities that featured in the top 10 most polluted list include Hajipur (Bihar), Ghaziabad, Gurugram, Sasaram (Bihar), Patna, Talcher (Odisha), Rourkela (Odisha), and Rajgir (Bihar). Meanwhile, Aizawl in Mizoram was ranked the cleanest city in the country during this period.
The report, covering January to June 2025, analysed data from 239 out of 293 cities equipped with Continuous Ambient Air Quality Monitoring Stations (CAAQMS). Of these, 122 cities exceeded the annual NAAQS limit, while 117 cities remained within acceptable levels.
Earlier this year, Byrnihat was also labelled the “most polluted metropolitan area in the world” by the 2024 IQAir World Air Quality Report, which reported an annual PM2.5 average of 128.2 µg/m³, vastly exceeding the World Health Organization’s recommended limit of just 5 µg/m³.
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Byrnihat, located on the Assam-Meghalaya border, is a major industrial hub with 39 industrial units in Assam and 41 in Meghalaya. In Meghalaya, most units are located in the Export Promotion Industrial Park (EPIP) in Ri-Bhoi district, while Assam’s industries are concentrated in Tamulkuchi, Kamrup (Metro).
Chairman of the Meghalaya State Pollution Control Board (MSPCB), R. Nainamalai, blamed Assam for the high pollution levels. He noted that 20 of Assam’s 39 industries fall into the “Red” category — denoting high pollution potential — compared to just 2 of 41 in Meghalaya.
He also highlighted a stark contrast in air quality at the beginning of the year. On January 26, the AQI on the Assam side reached a “very poor” 341, as measured at the Central Academy for State Forest Service. Meanwhile, the Meghalaya side recorded “satisfactory” air quality across four EPIP monitoring stations at 15th Mile, 17th Mile, and Killing.