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

Abstract

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 49.12µg/g and from 10.35 to 38.09µg/g during the dry and wet seasons, respectively, and the ranges were significantly higher than the prescribed WHO (0.001µg/g) and European Union (0.002µg/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 2.014μg BaP/g with a slightly higher range of 1.046 to 2.763μg 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 (0.0194µg/g) and B(a)P (0.0163µg/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.