Exploring the multi-faceted health risks of heavy metals exposure in Sikkim's unique Himalayan ecosystem, India

Sikkim, located in the Eastern Himalayas, is a prominent tourist destination. The state exhibits a diverse climatic range spanning from subtropical to alpine zones. Springs and glacier-fed rivers serve as the primary water sources for both residents and tourists. Furthermore, rapid urbanization, climate change, altered precipitation patterns and frequent landslides have significantly stressed these water sources, especially in the lower subtropical regions, resulting in declining water quality. This study aimed to assess heavy metal contamination in surface water, considering both natural and anthropogenic sources, and its impact on different population groups. A total of 155 water samples were collected from households, rivers, springs and hot springs across pre-monsoon, monsoon and post-monsoon seasons. Heavy metals (Al, As, Cd, Co, Cr, Cu, Hg, Fe, Mn, Ni, Pb and Zn) were analyzed, and water quality was assessed using various water pollution indices. The findings revealed that the water is unsuitable for consumption without treatment. A novel approach, Monte Carlo simulation, was employed in health risk assessment, incorporating sensitivity and uncertainty analyses. This method provided greater accuracy in evaluating both carcinogenic and non-carcinogenic risks, with the results indicating moderate to high cancer risks through ingestion and dermal absorption. It is strongly recommended that treated water be used for drinking to mitigate exposure to heavy metal contamination in the region.