Byrnihat most polluted city in India in first half of 2025: Analysis

Byrnihat, located on the Assam-Meghalaya border, ranked as the most polluted city in India in the first half of 2025 while Delhi stood a distant second, according to a new analysis.

According to the analysis by independent research organisation Centre for Research on Energy and Clean Air (CREA), Byrnihat recorded an average PM2.5 concentration of 133 micrograms per cubic metre, while Delhi's PM2.5 levels reached twice the national ambient air quality standard at 87 micrograms per cubic metre.

Hajipur (Bihar), Ghaziabad, Gurugram, Sasaram (Bihar), Patna, Talcher (Odisha), Rourkela (Odisha) and Rajgir (Bihar) were the other cities in the top 10 most polluted list.


Aizawl in Mizoram was the cleanest city in the country in the first half of the year.

From January to June, CREA said, particulate matter data was available for over 80 per cent of the days in 239 out of 293 cities with continuous ambient air quality monitoring stations (CAAQMS).

Among the 239 cities, 122 exceeded the annual National Ambient Air Quality Standard (NAAQS) of 40 micrograms per cubic metre, while 117 cities remained below the annual limit.

CREA said that while the introduction of vehicle restrictions, such as the end-of-life ban in Delhi, is an important component of air quality management, focusing solely on vehicular emissions risks overlooking other critical year-round sources of pollution.

According to source apportionment studies from the Portal for Regulation of Air Pollution in Non-Attainment Cities (PRANA) and IIT Delhi, in addition to transport (17 per cent-28 per cent) and dust (17 per cent-38 per cent), several other sectors contribute significantly to PM levels, including residential combustion (8 per cent-10 per cent), agricultural burning (4 per cent-7 per cent) and industrial activities and power plants (22 per cent-30 per cent).

These studies consistently show that Delhi-NCR's air quality crisis is not solely due to vehicles or seasonal biomass burning, but is also driven by continuous emissions from multiple sources across sectors.

For example, despite clear Supreme Court directives, critical pollution control technologies such as flue gas desulfurisation (FGD) systems are still absent in most thermal power plants near Delhi, CREA's analyst Manoj Kumar said.

As of mid-2025, only two out of eleven plants within a 300-kilometre radius of the capital -- NTPC Dadri and Mahatma Gandhi coal-fired power plants -- have operational FGDs.

This regulatory gap weakens the gains made through stricter vehicle policies and creates an uneven enforcement landscape, where agricultural sources face heavy scrutiny while other sectors continue to pollute unchecked, CREA said.