A new study using 25 years of satellite data finds that North-East India has seen one of the sharpest pollution increases in the entire Indo-Gangetic Plain region. Carbonaceous aerosols — driven by slash-and-burn agriculture and biomass-based cooking and heating — rose nearly 50% between the two decades studied. Most of the region has now crossed into ‘highly polluted’ territory, yet it remains outside the scope of India’s clean air programme.
Research published in the journal Atmospheric Environment, led by Prof Abhijit Chatterjee and Soumen Raul of the Bose Institute, Kolkata, has mapped particulate matter (PM) pollution trends across the Indo-Gangetic Plain (IGP), North-East India, and the Himalayas from 2000 to 2024. The findings for North-East India are among the study’s starkest.
Organic carbon and sulphate components of PM, both closely associated with biomass burning, increased by nearly 50% in North-East India during 2010–2019 compared to the 2000–2009 baseline. Hotspots that were once concentrated in Assam, Meghalaya, and Tripura have expanded across all three states and into Bangladesh. Most of North-East India has crossed the threshold from ‘polluted’ to ‘highly polluted’ for carbonaceous aerosols over the past two decades.
Slash-and-Burn and Domestic Biomass: The Primary Drivers
The sharp rise in carbonaceous PM across the region is attributed to two main sources: intensified slash-and-burn agricultural practices, and the extensive use of biomass — wood, crop residue, cow dung — for cooking and heating in rural households. These are deeply embedded in rural livelihoods, and India’s current clean air framework has no significant mechanism to address them.
“NCAP is primarily designed as a city-focused initiative. But our data shows that air pollution in rural India is equally severe, and in some cases more so. Biomass burning (for cooking, heating, agriculture) is not being adequately addressed by the programme as it currently stands. The rural dimension needs to be explicitly built into the clean air mission.” — Prof Abhijit Chatterjee, Bose Institute, Kolkata
Assam’s Industrial Belt: A Separate and Growing Concern
The study identifies a specific and worsening industrial pollution problem in Assam. Sulphate emissions in the state rose by more than 30% after NCAP implementation, driven by thermal power plants, oil refineries, and cement industries concentrated in Bongaigaon, Guwahati, Dibrugarh, Digboi, Numaligarh, and Bokajan. Dust pollution showed some improvement, declining to relatively safer limits in Kokrajhar, Dhubri, and Bongaigaon — but the industrial sulphate signal is moving in the opposite direction.
North-East India’s Pollution is Crossing into the Eastern Himalayas
The satellite study shows that North-East India, along with the lower IGP, is a primary source region for aerosol loading over the eastern Himalayas. The study also found strong inter-Himalayan transport: emissions from the central and eastern Himalayas, in turn, affect North-East India. The region is both a significant source and a receptor of long-range pollution — a dynamic that is entirely outside any current policy framework.
“The eastern Indo-Gangetic Plain, and increasingly North-East India, are carrying a disproportionate pollution burden — and it is being driven almost entirely by biomass burning. That is the signal that stands out most clearly across 25 years of data.” — Prof Abhijit Chatterjee, author from Bose Institute, Kolkata
What the Research Recommends
The researchers argue that NCAP 2.0 must go beyond its current mandate of 131 non-attainment cities to include rural regions and ecologically sensitive areas. North-East India’s biosphere-rich zones are named explicitly in the paper as warranting inclusion in India’s Clean Air Mission alongside the Sundarbans and the Himalayan regions. Without this expansion, the programme will continue to miss the dominant and growing sources of PM pollution in the country.
About The Research
Research led by: Prof Abhijit Chatterjee, Bose Institute, Kolkata
Main research fellow: Soumen Raul
Published in Atmospheric Environment: https://doi.org/10.1016/j.atmosenv.2026.121810
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