From CK Nayak
NEW DELHI, May 29: The “historically clean” Northeastern region, including Meghalaya, has transformed into a pollution hotspot due to overall particulate matter (PM) pollution over the last few years, a recent study said.
“Between 2000 and 2024, PM pollution across Northeast India shifted drastically, transforming the region from a historically clean area into a highly polluted year-round hotspot,” a landmark 25-year satellite data study published by researchers at the Bose Institute, Kolkata, showed.
Overall aerosol loading and PM pollution in the region rose by over 20% to 50% depending on the pollutant type, during this period, it said. The findings for the region are among the starkest.
Overall particulate matter pollution surged by more than 20% during the 2010-2019 decade compared to the 2000-2009 baseline. Organic carbon aerosols—fine particles associated with smoke—increased by nearly 50% in the Northeast between the two decades, the study added.
Between 2020 and 2024, organic carbon aerosol levels climbed an additional 30% to 40%, pushing the region firmly into “highly polluted” territory, the study said. The spatial footprint of intense pollution expanded significantly across state borders over the 24-year timeline.
Severe carbon pollution was highly localised, restricted to isolated pockets of Assam, Meghalaya, and Tripura. High-pollution zones swallowed almost all of Assam, Meghalaya, and Tripura, merging seamlessly with cross-border pollution belts over Bangladesh and the lower Indo-Gangetic Plain (IGP).
Major hubs like Guwahati registered PM2.5 levels up to 53% higher than National Ambient Air Quality Standards, the most massive geographic growth in PM footprint over previously pristine rural and non-urban areas, the study said. Unlike northern India, where industrial activity and vehicle emissions dominate air quality degradation, the Northeast’s pollution rise is distinct.
The overarching driver is rural biomass usage (wood, dung, and organic matter) for domestic heating and cooking. Intensified jhum cultivation (slash-and-burn practices) triggered massive seasonal spikes in smoke and carbonaceous PM, it added.
Winds flowing along the Brahmaputra River Valley carry massive amounts of sulphate and carbon emissions from West Bengal and Bihar into the valleys of the Northeast and the eastern Himalayas. Because India’s National Clean Air Programme (NCAP) is heavily city-focused, large rural swathes of the Northeast are driving these biomass emissions, which currently remain outside structured policy interventions.
Most of the region has now crossed into ‘highly polluted’ territory, yet it remains outside the scope of India’s clean air programme. The study also found strong inter-Himalayan transport: emissions from the central and eastern Himalayas, in turn, affect the Northeast.
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 Northeast 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,” the study said.
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. The Northeast’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. The research, published in the journal ‘Atmospheric Environment’, led by Abhijit Chatterjee and Soumen Raul of the Bose Institute, mapped PM pollution trends across the IGP, the Northeast, and the Himalayas from 2000 to 2024.
