Polycyclic aromatic hydrocarbons (PAHs) in fish (Clarias gariepinus) of southwestern rivers, Nigeria: Occurrence, distribution, and potential human exposure risks

This study was undertaken to analyze Polycyclic aromatic hydrocarbons (PAHs) in fish (Clarias gariepinus) from six major rivers within southwest Nigeria to assess the ecotoxicological and human health risks. The average concentrations of total PAH (∑PAH) ranged from 12.18 to 49.12 µg/g and from 10.35 to 38.09 µg/g during the dry and wet seasons, respectively, and the ranges were significantly higher than the prescribed WHO (0.001 µg/g) and European Union (0.002 µg/g) recommended safe levels for human consumption. The low molecular weight PAHs (2–3 rings) dominated the profile, suggesting petrogenic sources. Phenanthrene remains the highest contributor to PAH intake across all locations and seasons. The toxicity equivalent quotients (TEQ), which represents the sum of B(a)P equivalent concentration [B(a)Peq] ranged from 0.851 to 2.014 μg BaP/g with a slightly higher range of 1.046–2.763 μg BaP/g during the dry and wet seasons, respectively. Across both seasons, the estimated hazard quotient (HQ) and hazard index (HI) were found to be < 1, suggesting consumption of Clarias gariepinus has no non-carcinogenic risks. The estimated excess cancer risk value (1.55×10−2 to 5.03×10−2) from consumption of C gariepinus exceeded all regulatory guideline values for potential cancer risk. The excess cancer risk, predominated by B(a,h)A (0.0194 µg/g) and B(a)P (0.0163 µg/g) suggests a greater risk of exposure during the wet season. The study showed no human health risk due to PAHs in Clarias gariepinus obtained from southwestern rivers in Nigeria. However, due to bioaccumulation, policies that will ensure regular monitoring of PAHs in seafood are recommended to maintain a sustainable ecosystem. •Phenanthrene contributed the highest intake of PAH across all locations and seasons.•LMW-PAHs dominated the profile probably due to their higher concentration in water•PAHs determined in the fish are attributed to multiple PAH sources•Excess cancer risk value showed ecotoxicological risk to fish including carcinogenic•Hazard index and hazard ratio indicate no non-carcinogenic risks.