Seasonal Variations of Heavy Metal Distribution and Bioaccumulation Patterns with Health Risk Assessment in Commercial Freshwater Fish from Karanja Reservoir, India

Seasonal variations in metal contamination and the potential human exposure through fish consumption is poorly understood for many Indian reservoirs. This study aims to assess the concentrations, seasonal variations and bioaccumulation patterns of ten heavy metals (As, Cd, Co, Cu, Cr, Fe, Hg, Ni, Pb and Zn) in different tissues (all the fins, gills, muscles, liver and whole body) of five commercially important species of fishes: Channa striata, Labeo rohita, Mystus cavasius, Notopterus synurus and Oreochromis mossambicus along with surface and bottom water collected from Karanja Reservoir, Bidar, Karnataka (India), during January 2023 to December 2024. In addition, this study evaluates the potential human health risks posed by metal contamination through fish consumption which has not been documented earlier for this reservoir. Heavy metal concentrations varied significantly among fish tissues and between water samples. The bioaccumulation patterns and order of occurrence were also assessed. Comparative analyses with the WHO and Indian standards revealed that Cd, Ni and Pb levels in both fish and water exceeded permissible limits, while Cr in water was also higher than WHO standards. Whereas As, Co, Cu, Ni, Pb and Zn concentrations generally remained within the permissible limits. Bioaccumulation pattern varied among species and tissues; Fe showed the highest bioaccumulation in the fins of N. synurus, whereas the lowest was recorded in the muscles of O. mossambicus, remaining below threshold values. Health risk assessment indices (Estimated Daily Intake- EDI, Target Hazard Quotient- THQ and Hazard Index- HI) indicated that non-carcinogenic risks from fish consumption were within acceptable safety thresholds. Carcinogenic risk (CR) values for As, Cd, Cr, Ni and Pb were below the critical limit, suggesting negligible cancer risk, except for As, which showed a potential carcinogenic threat. Overall, the findings highlight the need for regular monitoring of heavy metal contamination and public awareness regarding safe fish consumption from the Karanja Reservoir.