Ecotoxicological and Human Health Risks from Heavy Metal Contamination in Water and in the Muscle Tissue of Oncorhynchus mykiss in the Sonche River Basin, Amazonas, Peru

Heavy metal contamination of surface water resources poses a critical threat to aquatic biodiversity and food security in Andean ecosystems. In this study, we evaluated the concentrations of arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) in surface water samples and in the muscle tissue of rainbow trout (Oncorhynchus mykiss) collected at four representative sites in the Sonche River basin (Amazonas, Peru) during the dry and rainy seasons. Quantitative measurements were performed using anodic stripping voltammetry (ASV), however, due to the lack of certified reference materials, the method was not fully validated, and results should be considered semi-quantitative. The hydrochemical results revealed that the concentrations of Cd and Pb in the water exceeded the Environmental Quality Standards (ECA-Water, Category 4), with the highest levels recorded at the Rondón site (P3) during the rainy season—a pattern that could be associated with runoff from the municipal landfill. In the muscle tissue of O. mykiss, mean concentrations exceeded the international maximum permissible limits (SANIPES/EU) for Cd (0.176–0.536 mg kg−1) and Pb (0.933–2.516 mg kg−1) at all sites and seasons and for Hg (0.520 mg kg−1) at P3 during the dry season. Bioaccumulation factors (BAF) were calculated, identifying mercury as the element with the greatest capacity for bioconcentration in the biota. Based on estimated daily intake (EDI) and hazard quotient (HQ) calculations, Hg posed the primary potential non-carcinogenic risk, with the hazard index (HI) exceeding the threshold (HI > 1.0) at all sampling sites and periods. These findings indicate significant bioaccumulation of toxic metals in O. mykiss and suggest that, under the high-consumption assumptions used in this assessment, frequent consumption of these fish may pose a potential health risk to local populations.