Toxicity and risk evaluation of polychlorinated biphenyls in River Otamiri, Imo State

Polychlorinated biphenyls are a family of dangerous, long-lasting chemicals that can be detrimental to human health and also have a significant propensity to build up in the environment as organic pollutants. In this regard, the toxicity, carcinogenic, and non-carcinogenic health risks of PCBs in the surface water and sediment of the River Otamiri in Imo State were investigated. This study collected surface water and sediment samples from the River Otamiri at four sampling points. An Agilent 7890A gas chromatograph connected to an Agilent 5975C mass selective detector was used to conduct the PCB analysis. Twenty-eight PCB congeners were detected in the water and sediment samples. Also, the PCB congeners' descriptive statistics (mean and standard deviation) in the studied matrices were reported. The total levels of PCBs in the surface water and sediment ranged from 622.87 - 935.84 ng L-1 and 1621.03 - 2748.17 mu g kg-1 respectively. The concentration of PCB congeners in the studied matrices revealed that PCB-118 had the highest concentration, while the lowest concentration was recorded in PCB-157. The toxicity equivalent quotient (TEQ) was used to assess the harmful effect of dioxin-like PCBs in the studied matrices. High TEQs beyond the World Health Organization's (WHO) acceptable limit were observed for PCB-126 and PCB-169 congeners in both surface water and sediments.This raises the possibility of an ecosystem risk. Furthermore, the lifetime cancer risk values of dioxin-like polychlorinated biphenyls (DL-PCBs) in surface water and sediments were within the tolerable risk limit, whereas the hazard quotient values exceeded the recommended tolerable limit stipulated by the WHO. It is critical to notice that PCB-126 contributions had a major impact on the high hazard index values. Additionally, the possibility of non-cancer risks in children is significantly higher than that of adults because of their lower body mass and pickier habits. This indicates that children are more susceptible to the non-carcinogenic effect of DL-PCBs in the studied matrices. In conclusion, awareness programs and environmental policies are required to ensure the safety of the river from organic pollutants.