Bacteria from desert dust storms ride the wind from western India to the Himalayas, posing emerging health risks associated with respiratory, skin, and gastrointestinal infections in high-altitude regions long considered pristine, Indian scientists from the Bose Institute, an autonomous institute under the Department of Science and Technology (DST), have found.
Challenging the long-held perception of the Himalayan hill-top atmosphere as uniformly clean and health-protective, the scientists have identified disease-causing airborne pathogens travelling with elevated desert dust plumes from arid regions of western India to the Eastern Himalayas.
Lead author of the study, Sanat Kumar Das, said high-altitude Himalayan regions are already physiologically demanding due to cold climatic conditions and low oxygen levels, which heighten vulnerability to infections. However, evidence directly linking airborne microbial exposure to health risks in these regions has remained limited. The microbiological dimension of long-range dust transport, in particular, has been poorly understood—prompting the researchers to undertake the present study titled “Long-range transported bacteria perturbing airborne bacterial diversity and pathogenicity over Eastern Himalayas, India.”
Over more than two years of continuous monitoring, the scientists tracked dust storms rising from the Thar Desert and other arid regions of western India. The study shows that powerful dust plumes can travel hundreds of kilometres, crossing the densely populated and polluted Indo-Gangetic Plain before settling over Himalayan hilltops, added Das.
Crucially, these dust clouds do not travel alone. They carry a complex mix of airborne bacteria, including pathogens capable of affecting human health. The researchers found that desert dust-attached bacteria significantly alter the composition and diversity of airborne microbial communities over the Himalayas, said lead author Sanat Kumar Das from the Bose Institute. He was assisted by his colleagues Antara Pramanick, Shahina Raushan Saikh, and Md. Abu Mushtaque, while researchers Damodararao Karri and Naveen Gandhi represented the Center for Climate Change Research, Indian Institute of Tropical Meteorology, Pune.
In addition to horizontal transport from distant deserts, the study found that vertical uplift of polluted air from Himalayan foothills injects locally sourced pathogens into the high-altitude atmosphere. These locally derived microbes mix with long-range travellers from desert dust, collectively reshaping the bacterial population floating above Himalayan regions.
The combined effect has tangible health implications. While desert dust-attached bacteria were found to contain a high proportion of skin-infecting pathogens, vertically uplifted pollution primarily carried respiratory disease-causing bacteria. Downward transport from the free troposphere contributed bacteria associated with gastrointestinal infections. Local Himalayan bacterial populations, though smaller in number, were also consistently loaded with pathogens.
Published in the journal Science of the Total Environment, the study is the first of its kind to quantitatively demonstrate how both long-range desert dust transport and vertical atmospheric mixing perturb the Himalayan airborne bacterial community, with direct implications for public health.
Using culture-independent metagenomic analysis, ground-based aerosol measurements, chemical characterisation of particles, satellite observations, and atmospheric back-trajectory modelling, the researchers analysed airborne bacteria over the Eastern Himalayas during 2022 and 2023. Their findings showed that nearly 80 per cent of the airborne bacterial population over Himalayan hilltops originates from long-range horizontal and vertical transport processes, causing about a 60 per cent disturbance in bacterial diversity.
Space-borne observations revealed thick dust layers between two and three kilometres above the Eastern Himalayas, traced back to the Thar Desert. Long-range dust transport led to a 40 per cent increase in unique bacterial loading, while upwelling pollution and downwelling air masses contributed additional distinct bacterial genera.
The researchers noted that the Himalayan atmosphere emerges from the study as a dynamic and globally connected system—acting as a conveyor belt for microorganisms, including pathogens, across vast distances.
Das said the findings provide critical inputs for strengthening national health action plans and developing health-forecast systems that can anticipate disease risks linked to atmospheric transport. Such insights, the authors noted, align with India’s long-term development goals under Viksit Bharat @ 2047, particularly as climate change is expected to intensify dust activity and atmospheric circulation patterns.
