Preliminary Health Risk Assessment of Potentially Toxic Metals in Surface Water of the Himalayan Rivers, Nepal

This study investigates the contamination levels and risk assessments of 14 elements (Ba, Cd, Co, Cr, Cu, Pb, Li, Mn, Mo, Ni, Sb, Sr, V and Zn) in three sub-basins of Himalayan rivers. Water samples were collected and the hazard quotient (HQ), hazard index (HI), and water quality index (WQI) were calculated. Total average concentrations of the metals were 135.03, 80.10 and 98.34 µg/L in Gandaki, Indrawati and Dudh Koshi rivers, respectively. The results of HQ and HI were less than unity, suggesting a low risk of metals in the region. However, HQ for antimony (Sb) was found to be 4.4 × 10⁻¹, 2.1 × 10⁻¹ and 5.4 × 10⁻¹ in three river basins and HI near unity, suggesting its potential risk. Additionally, HI for Cd in Indrawati was 5.4 × 10⁻¹ also close to unity, suggesting that Cd could have a potential risk to the local residents and aquatic ecosystems. Further, WQI suggested that the rivers Gandaki and Indrawati fell into the excellent water quality and river Dudh Koshi fell into good water quality.