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The northeastern region of India, including states like Assam and Tripura, is emerging as a major pollution hotspot.
Districts in the region saw elevated PM2.5 levels year-round.
This highlights the need for district-level clean air policies.
Northeast India is now facing a year-round air-pollution crisis, according to a new satellite-based assessment released November 25, 2025.
States like Assam and Tripura recorded high PM2.5 levels in every season, including monsoon — the period when most of India normally sees cleaner air, showed the report by the Centre for Research on Energy and Clean Air (CREA).
The researchers assessed PM2.5 concentrations across four seasons: Summer (March–May 2024), monsoon (June–September 2024), post-monsoon (October–November 2024) and winter (December 2024–February 2025).
During the same period, the Indo-Gangetic airshed was the most polluted, with elevated PM2.5 levels in winter, summer and post-monsoon seasons. An airshed, as defined by the World Bank, is a geographic area where pollutants get trapped and affect the air quality for everyone living within it.
The assessment also showed that poor air quality extended far beyond India’s urban regions and the winter season. Some 447 districts, or 60 per cent the districts studied exceeded India’s National Ambient Air Quality Standard (NAAQS) of 40 microgrammes per cubic metre (µg / m3) for annual average PM2.5 concentration. Not even one district meets the stricter World Health Organization (WHO) guideline of 5 µg / m3.
Fifty worst-affected districts are in Delhi, Assam, Haryana and Bihar, according to the report. Delhi and Assam top the list with 11 districts each, accounting for nearly half of India’s most polluted hotspots.
Bihar and Haryana follow with seven districts each, showing how pollution remains heavily clustered in certain regions.
Other states also featured prominently: Uttar Pradesh has four districts, Tripura three, Rajasthan and West Bengal two each, and one district each in Chandigarh, Meghalaya and Nagaland.
The situation is especially worrying in Delhi, Punjab, Haryana, Himachal Pradesh, Meghalaya, Chandigarh and Jammu & Kashmir, where every district had PM2.5 levels above the NAAQS limit for most of the year, except during the monsoon.
The data revealed a countrywide crisis, demanding action at the district level, not just in selected cities.
At the state- and Union territory-level, the report found that all 33 regions assessed exceed the WHO standard, and 28 have at least one district above NAAQS. Even the so-called “cleaner” states are falling short.
Delhi once again emerged as the most polluted state or UT, with an annual average PM2.5 concentration of 101 μg / m3 — 2.5 times the national limit and 20 times the WHO guideline.
Southern India remained comparatively better off. Puducherry (25 µg / m3) and some other southern states fell below the national standard, offering a chance to move toward WHO interim targets.
But the authors of the report warned that state averages often hide local hotspots. Maharashtra, for example, appeared close to the NAAQS threshold, yet 14 of its districts breached the standard, with industrialised Chandrapur among the most polluted.
In winter, 616 or 82 per cent of the 749 districts exceeded the standard. PM 2.5 stayed high even in the summer months in 405 districts or 54 per cent of the districts in India.
During the monsoon only 10 per cent of the districts exceeded the standard, but once the rains retreated, three out of four districts (75 per cent) again violated the limit, showing that the core problem lies in baseline emissions, not weather patterns.
India needs to widen its clean air policies, according to CREA. At present, the system focuses mainly on 131 “non-attainment cities”, but this is far too limited for a crisis that now affects entire districts, states and even airsheds such as the Indo-Gangetic region.
The authors of the report called for airshed-based governance frameworks, satellite monitoring integration into NCAP, sectoral emission targets and accountability mechanisms.
They urged the government to recognise new and fast-growing pollution hotspots, especially in northeastern and eastern India, where air quality is worsening much quicker than before.
India now needs region-specific standards and strategies because pollution sources and local conditions vary widely across the country, they noted.
The researchers also made it clear that India’s air pollution crisis cannot be handled with short-term, seasonal steps like the Graded Response Action Plan. Instead, it requires strong, year-round policies that address pollution at its source.