Human Health Risk Assessment of Heavy Metals and Polycyclic Aromatic Hydrocarbons in Seafood from Southern Nigeria’s Coastal Regions

Aim: The levels of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in tilapia fish, prawn, oyster and periwinkle samples from southern Nigeria’s coastal regions were evaluated to determine possible human health risk associated with consumption. Study Design: Ten (10) samples each of the selected seafood were collected from mangrove swamps along Bakana River in the study area. The samples were analyzed for nutrient levels and concentrations of toxic metals and PAHs. Methodology: The concentrations of heavy metals and PAHs in the selected seafood samples were determined using Gas Chromatography Flame Ionization Detector and Atomic Absorption Spectrophotometry. Probable human health risk associated with the seafood consumption for adult and children populations was evaluated using Estimated Daily Intake (EDI), Target Hazard Quotient (THQ) and Carcinogenic Risk (CR) assessment for heavy metals and PAHs. Results: The seafood samples showed the presence of heavy metals (Cr, Cd, Cu, Pb and Zn) but values were all below regulatory permissible limits of 0.6, 0.05, 3.0, 0.2 and 5.0 mg/kg respectively. PAH compounds (fluorene and anthracene) were below detectable limits in the seafood samples; phenanthrene was detected in all the seafood samples but highest in Tilapia fish, recording 28.32±0.05 mg/kg. Benzo (a) pyrene was below detectable limit in the investigated seafood samples. Carcinogenic Risk (CR) assessment values for heavy metals in the seafood samples were significantly (p<0.05) high for Cd, Pb, Cr and Ni in both adult and children populations. CR values for PAHs were within regulatory threshold of 10E-6 – 10E-4. Conclusion: This study revealed that individual carcinogenic potencies for heavy metals (Cd, Pb, Ni, Cr) in the seafood samples exceed the guideline screening value for human consumption, indicating high potential for carcinogenic risk. Our findings suggest that Bakana river is exposed to substantial amount of carcinogenic environmental pollutants associated with deleterious environmental and epidemiological effects.