A 25-year satellite study has identified Bihar and West Bengal as major particulate pollution hotspots in eastern India.
The study found that particulate matter pollution rose by more than 20% across the Indo-Gangetic Plain, the Himalayas and north-east India between 2000 and 2024.
Researchers said biomass burning, including rural fuel use and agricultural burning practices, is driving much of the growing pollution burden in the eastern Indo-Gangetic Plain and north-east India.
The findings also warn that emissions from the Indo-Gangetic Plain are affecting aerosol loading across the Himalayas.
A 25-year satellite study has identified Bihar and West Bengal as major particulate pollution hotspots, warning that the eastern Indo-Gangetic Plain (IGP) and north-east India are carrying a growing pollution burden driven largely by biomass burning.
The study, Decadal shifts in aerosol hotspots and source attribution over IGP, north-east India and Himalayas: A 25-year (2000–2024) study, found that particulate matter (PM) pollution rose by more than 20 per cent across the IGP, the Himalayan region and north-east India over the study period. The research was published in the journal Atmospheric Environment.
Using the Moderate Resolution Imaging Spectroradiometer, the Earth-observing instrument aboard National Aeronautics and Space Administration's Terra and Aqua satellites, the researchers discovered the highest PM concentrations in the eastern IGP, particularly Bihar, southern West Bengal and large parts of Bangladesh, the researchers observed.
Pollution levels across the IGP, the Himalayan region and north-east India rose by 10 per cent to 40 per cent between 2010 and 2019, compared with the previous decade, the study said.
More worryingly, the researchers found that the composition of PM had also changed. Organic carbon and sulphate components of PM, both closely associated with biomass burning, increased by almost 50 per cent, according to the study.
The sharp rise in pollution levels in north-east India can be directly linked to “intensified slash-and-burn agricultural practices and the extensive use of biomass for domestic energy in rural households,” the study said.
“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,” said Abhijit Chatterjee, one of the study’s authors, affiliated with the Bose Institute in Kolkata, West Bengal.
The study also mapped how pollution hotspots have expanded over the past two decades. Between 2000 and 2009, pollution was mostly concentrated in Bihar, Uttar Pradesh, northern West Bengal, Assam, Meghalaya, Tripura and Bangladesh, the researchers found.
By 2020-24, hotspot regions had expanded to cover all of West Bengal and Bihar, along with Bangladesh and much of Assam, Meghalaya and Tripura, according to the study. Uttar Pradesh was an exception, with pollution levels showing a decline, the researchers said.
The spike in pollution in these regions corresponds more closely to increased rural biomass burning and urban solid-waste burning than to industrial or vehicular emissions, according to the research.
The study found differences in the composition of PM across the IGP. In the eastern parts of the region, carbonaceous aerosols, which are “particles released by the burning of crop residue, wood and other organic material”, showed an increasing trend. In the western IGP, dust pollution remains the main pollutant but has shown a declining trend, the study found.
The study also warned that pollution from the IGP is increasingly affecting higher-altitude regions, including the Himalayas.
“Emissions are now directly affecting aerosol (suspension of microscopic solid or liquid particles such as dust, soot, and chemical droplets in the atmosphere) loading across the Himalayas, with pollution from Punjab, Haryana, and Delhi reaching the western and central ranges, and emissions from Bihar and West Bengal influencing the eastern Himalayas”, the study warned.
The study suggested that India’s National Clean Air Programme (NCAP), a central initiative launched in 2019 by the Union Ministry of Environment, Forest and Climate Change, should expand beyond urban centres to include rural areas and ecologically sensitive zones such as the Sundarbans. The Sundarbans is already an ecologically stressed region, the researchers noted.
The study found mixed results for the NCAP. States in the IGP, including Bihar, West Bengal and Assam, were able to bring down overall particulate matter levels in the period after the programme began, according to the study. However, biomass burning increased significantly during the same period.