Human Health Risk from Consumption of Contaminated Seafood in Obio/Akpor Local Government Area, Port Harcourt: A Quantitative Risk Assessment of Heavy Metals

This study assesses the human health risks associated with the consumption of seafood contaminated by heavy metals in Port Harcourt, Nigeria. Commonly consumed species—mud crab (Scylla serrata), shrimp (Penaeus monodon), bonga fish (Ethmalosa fimbriata), and catfish (Clarias gariepinus)—were analyzed using Atomic Absorption Spectrophotometry (AAS) to quantify lead (Pb), cadmium (Cd), nickel (Ni), copper (Cu), zinc (Zn), and iron (Fe) concentrations. Results revealed that Pb levels ranged from 2.21 mg/kg in bonga fish to 2.92 mg/kg in mud crab, exceeding the WHO limit of 2.0 mg/kg. Cd concentrations ranged from 0.18 mg/kg (bonga fish) to 0.41 mg/kg (catfish), nearing or exceeding the threshold of 0.3 mg/kg. Other metals, including Zn (5.90–6.78 mg/kg), Fe (22.04–25.98 mg/kg), and Cu (1.13–1.24 mg/kg), were within regulatory limits. Estimated Daily Intake (EDI) for Pb reached 1.04 × 10⁻² mg/kg/day and Cd 1.46 × 10⁻³ mg/kg/day in catfish, surpassing oral reference doses. Target Hazard Quotient (THQ) values exceeded 1.0 in mud crab and catfish, with THQ_Pb = 2.60 and THQ_Cd = 1.46, indicating non-carcinogenic risk. The Hazard Index (HI) for all species exceeded the safety threshold, highest in catfish (4.42). Carcinogenic Risk (CR) for Cd in catfish (2.19 × 10⁻²) and mud crab (1.71 × 10⁻²) was significantly above the acceptable USEPA range (10⁻⁶ to 10⁻⁴). These results call for urgent environmental regulation, continuous seafood safety monitoring, and public health intervention in the Niger Delta.