A new study has revealed a hidden danger carried by clouds drifting over the Himalayas.

These clouds were once thought to bring pure drinking water are instead transporting toxic heavy metals from polluted lowlands to some of the world’s highest and most fragile ecosystems.

This alarming discovery highlights serious health risks linked to these airborne pollutants, which pose potential threats from cancer to developmental disorders.

Researchers at the Bose Institute, an autonomous entity under Department of Science and Technology, identified significant levels of toxic metals such as cadmium (Cd), copper (Cu), and zinc (Zn) in non-precipitating clouds during the early monsoon season over the Western Ghats and Eastern Himalayas.

The pollution levels in clouds over the Eastern Himalayas were found to be 1.5 times higher, primarily due to emissions from heavy traffic and industrial activity in nearby foothill regions.

Led by Dr. Sanat Kumar Das, the atmospheric research team employed detailed statistical modeling to trace the sources of these metals and quantify associated health risks. Their analysis demonstrated that children in affected areas face a 30% higher risk of health issues relative to adults.

Inhalation emerged as the major exposure route, especially for non-carcinogenic diseases, with toxic metals dissolved in cloud water infiltrating human systems via skin contact, breathing polluted air, and consumption of rainwater.

The study also noted increased carcinogenic risk due to inhalation of dissolved chromium (Cr), emphasizing the growing threat posed by cloudborne pollutants. While Indian clouds remain relatively less polluted compared to counterparts in China, Pakistan, Italy, and the USA, the findings shatter the longstanding myth of pristine mountain rain and underscore an urgent need for monitoring airborne pollution and protecting vulnerable high-altitude communities.

Published recently in the journal Environmental Advances, this study opens new avenues for atmospheric pollution research and public health strategies, spotlighting clouds as unexpected vehicles of toxic metal transport from industrialized regions to remote mountainous environments.

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