Study: PM Pollution Increased Over 20% in a Decade, Reaching Himalayas

A satellite-based study covering 25 years of data across the Indo-Gangetic Plain, the Himalayan region, and North-East India has found that overall particulate matter (PM) pollution increased by more than 20% in a single decade (during 2010–2019 compared to the 2000–2009 baseline) with Bihar and West Bengal being the worst-affected zones. It also found that the emissions from the Plain are now reaching the Himalayas, noting that the mountains are no longer insulated from air pollution.

Published in Atmospheric Environment journal, the study by the Bose Institute, Kolkata also analysed India’s National Clean Air Programme (NCAP), flagging that the city-focused initiative under it has shown measurable results in urban PM levels but has yet to address biomass burning - the dominant and growing source across the region. It accordingly pitched for “urgent need for rural interventions” in the updated programme.

It further pointed out that the “persistent emissions from thermal power plants, rural biomass burning, and urban solid waste burning have limited reductions in carbon pollution despite the programme”. The study is a comprehensive long-term (2000-24) assessment of PM pollution trends across this region, tracing shifts in pollution levels, sources, and hotspots across three decades.

Noting how the Indo-Gangetic Plain (IGP) pollution is now reaching the Himalayas, the study flagged that the emissions from the plain 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. It said pollution from Punjab, Haryana, and Delhi is reaching the western and central ranges whereas the emissions from Bihar and West Bengal are influencing the eastern Himalayas.

“The Himalayas are not insulated from IGP pollution. Our trajectory analysis shows that what is emitted in Punjab or Bihar does not stay there — it travels into the mountains. These are ecologically and climatically sensitive zones, and they are currently outside the scope of any structured clean air intervention in India,” said Soumen Raul, primary researcher at the Bose Institute.

Assessing the effectiveness of interventions under NCAP, the study noted that Bihar, West Bengal, and Assam showed “measurable improvements” in overall PM levels in the post-NCAP period but pollution from biomass burning has not declined significantly in any of these states, and they continue to be hotspots for carbonaceous aerosols.

“NCАP 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,” said Abhijit Chatterjee who led the research at the Bose Institute.

Mapping the decadal shifts in pollution hotspots, the study noted that the high carbon pollution which used to be concentrated in parts of Bihar, Uttar Pradesh, northern West Bengal, Assam, Meghalaya, Tripura, and Bangladesh during 2000–2009 had by 2020–2024 expanded to all of West Bengal, Bihar, Bangladesh, and most of Assam, Meghalaya, and Tripura. The research attributed the expansion predominantly to rural biomass burning and urban solid waste burning rather than industrial or vehicular sources. It, however, underlined that Uttar Pradesh was a notable exception, registering a decline in carbon pollution in recent years.