Contamination and risk assessment of heavy metals in water and fish obtained in Bunza River in Kebbi State, Nigeria

Background: Fish are consumed worldwide due to their nutritional and health benefits; however, heavy metal pollution is compromising their safety. This study aimed to determine heavy metal safety in water and fish, specifically tilapia (Oreochromis niloticus) and catfish (Clarias gariepinus), collected from Bunza River in Kebbi State, Nigeria. Methods: Water and fish samples underwent analysis for zinc (Zn), cadmium (Cd), copper (Cu), and lead (Pb) using atomic absorption spectroscopy. The obtained values were then utilized to assess the associated health risks. Results: The atomic absorption spectroscopy of fish revealed significant differences (P < 0.05) between heavy metal concentrations in the fish organs and FAO/WHO standards. It indicated non-tolerable concentrations of copper (1.77-5.24 mg kg-1) and lead (1.85-4.53 mg kg-1). The estimated daily intake (EDI) of Pb and Cd through fish consumption was above the recommended daily intake (RDI). However, the hazard quotient (HQ) and health risk index (HI) of all the heavy metals were within tolerable limits ( < 1). On water samples, non-tolerable levels of the heavy metals and significant differences (P < 0.05) were observed when compared with the standards. The water samples had average concentrations of Cu (4.64 ± 0.62 mg kg-1), Pb (1.78 ± 0.70 mg kg-1), Cd (0.50 ± 0.02 mg kg-1), and Zn (18.90 ± 3.08 mg kg-1). The average daily ingestion (ADI) and HQ of the heavy metals through the consumption of the water were above the recommended limits. Conclusion: Based on the results, the fish and water samples could cause heavy metal-related toxicity. There is a need for policies aimed at decontaminating the river.