A recent study using satellite data has revealed concerning trends in air pollution over a 25-year period in the Indo-Gangetic Plain (IGP), the Himalayan region and North-East India. The findings showed levels of harmful particulate matter (PM) increased by more than 20 per cent from 2010 to 2019 compared to the previous decade, prompting researchers to call for India’s National Clean Air Programme (NCAP) to be expanded to include rural areas.
Rising air pollution in N-E
The study, ‘Decadal shifts in aerosol hotspots and source attribution over IGP, north-east India and Himalayas: A 25-year (2000–2024) study’ led by Professor Abhijit Chatterjee from the Bose Institute in Kolkata, tracked how pollution sources and levels changed over three decades. It tracked emissions patterns from this region affecting air quality in the Himalayas. For example, pollution from states like Punjab, Haryana, and Delhi is reaching the western and central Himalayas, while emissions from Bihar and West Bengal are impacting the eastern Himalayas.
The highest levels of PM were found in the eastern part of the Indo-Gangetic Plain, especially in areas like Bihar, southern West Bengal, and large parts of Bangladesh. Between 2010 and 2019, pollution levels rose by 10-40% across the Indo-Gangetic Plain, the Himalayan region, and North-East India compared to the earlier ten years. In North-East India, two specific components of PM, related to burning biomass, increased by nearly 50%.
Professor Chatterjee noted that the eastern Indo-Gangetic Plain and North-East India are facing a particularly heavy burden of pollution, mainly caused by biomass burning, which was a major finding of the research.
The study published in Atmospheric Environment Journal also showed a shift in the types of pollutants found in the air over the years. For instance, pollution from burning materials like crop waste and wood has become more common, especially in eastern areas, while dust pollution has decreased overall in the region. The research also identified changing pollution hotspots. In the early 2000s, high levels of pollution were mostly found in Bihar, Uttar Pradesh, northern West Bengal, Assam, Meghalaya, Tripura, and Bangladesh. By 2020-2024, these hotspots expanded significantly to include most of West Bengal and large parts of Assam, Meghalaya, and Tripura, driven mainly by biomass burning in rural areas and waste burning in urban areas, rather than by industrial activities or vehicles. However, Uttar Pradesh has seen a decrease in carbon pollution in recent years.
Pollution reaching Himalayas
The study found that emissions from the upper and middle IGP significantly affect aerosol loading over the western and central Himalayas. North-East India and the lower IGP (Bihar, West Bengal, and parts of Bangladesh) are the primary source regions influencing the eastern Himalayas.
It identified strong inter-Himalayan transport as eastern Himalayan regions were found to be substantially influenced by pollution from the western and central (Nepal) Himalayas, while emission from the central and eastern Himalayas in turn affect North-East. Central and eastern Himalayan areas adjacent to the IGP and North-East were found to be more polluted than other parts of the range.
“The Himalayas are not insulated from IGP pollution,” said another co-researcher Soumen Raul, Bose Institute, Kolkata. “Our trajectory analysis shows that what is emitted in Punjab or Bihar does not stay there — it travels into the mountains,” he further said.
Launch of NCAP 2.0
The study strongly suggested interventions to reduce pollution which should include rural areas in India’s updated NCAP 2.0, which has previously been effective in tackling pollution in urban regions.
The researchers argued that NCAP 2.0 must expand its scope beyond non-attainment cities to include rural regions and ecologically sensitive areas. The study specifically named the Sundarbans mangrove ecosystem, North-East India’s biosphere-rich areas and the biodiversity-dense Himalayan regions as zones that warrant inclusion in India’s Clean Air Mission.
