Health risk assessment of polychlorinated biphenyls in a fish species (Clarias gariepinus) from southwestern rivers, Nigeria

Abstract

The catfish (Clarias gariepinus) is commonly eaten in Nigeria, especially in the southwestern region. In this study, the levels of polychlorinated biphenyls (PCBs) in the muscles of Clarias gariepinus from six major rivers in the area were measured using gas chromatography with an electron capture detector. The PCB concentration ranged from 4.63 to 21.96 mg kg⁻¹ in the dry season and from 5.26 to 23.52 mg kg⁻¹ in the wet season. There were significant differences in PCB concentrations between the two seasons. The ∑PCB concentrations at any location were above the Food and Drug Administration tolerance level of 2.0 mg kg⁻¹ and other regulatory limits. The study found that chlorinated PCB congeners with a high octanol–water partition coefficient (K_ow) dominated the congener profiles. The most dominant congener was #101, comprising 12.3% to 17.8% of the total PCB concentration. The study also found that the levels of non-carcinogenic hazard quotient (HQ) and hazard index (HI) were below 1, suggesting no non-carcinogenic health risks from consuming Clarias gariepinus. However, the cumulative cancer risks (∑CR) fall within the low CR classification (10⁻⁶–10⁻⁴) by USEPA for all age categories. Also, the toxic equivalent quantity range was comparatively and significantly higher than the estimated non-carcinogenic screening values, suggesting potential health concerns. The study concluded that regular and continuous consumption of Clarias gariepinus as a significant portion of the diet may expose humans to unacceptable PCB concentrations due to residual environmental concentrations rather than a recent introduction.