This study emphasizes the importance of considering the metabolic and toxicity mechanisms of environmental concern chemicals in real-life exposure scenarios. Furthermore, environmental chemicals may require metabolic activation to become toxic, and competition for binding sites on receptors can affect the severity of toxicity. The multicomplex process of chemical toxicity is reflected in the activation of multiple pathways during toxicity of which AhR activation is major. Real-life exposure to a mixture of concern chemicals is common, and the composition of these chemicals determines the severity of toxicity. Nutritional essential elements can mitigate the toxicity of toxic heavy metals, while the types and ratio of composition of PAH can either increase or decrease toxicity. The epigenetic mechanisms of heavy metals and PAH toxicity involves either down-regulation or up-regulation of some non-coding RNAs (ncRNAs) whereas specific small RNAs (sRNAs) may have dual role depending on the tissue and circumstance of expression. Similarly, decrease DNA methylation and histone modification are major players in heavy metals and PAH mediated toxicity and FLT1 hypermethylation is a major process in PAH induced carcinogenesis. Overall, this review provides the understanding of the metabolism of environmental concern chemicals, emphasizing the importance of considering mixed compositions and real-life exposure scenarios in assessing their potential effects on human health and diseases development as well as the dual mechanism of toxicity via genetic or epigenetic axis.

Lagos lagoon is constantly being polluted from industrial and human activities. Fishes from Lagos lagoon contribute significant percentages of fish consumption in the Lagos metropolises. Therefore, this study evaluated heavy metal concentrations in tissues of four fish species (Sarotherodon melanotheron, Chrysichthys nigrodigitatus, C. gariepinus, and Ethmalosa fimbriata) from Lagos lagoons and their human health implication. Concentrations of heavy metals and potential health hazard to consumers were evaluated with reference to Estimated Daily Intake (EDI), Target Hazard Quotient (THQ) and Cancer Risk (CR). Concentration of the heavy metals in the fish tissues was below the maximum permissible limit in fish. Similarly, the. EDI of the heavy metals in all the tissues was below the recommended allowance whereas, the. THQ estimated for the heavy metals in the tissues of the fish were less than 1. Consumption of arsenic, nickel, and cadmium in the fish might however pose carcinogenic risk. Although, the measured heavy metal concentration were within permissible limits for human consumption, the calculated health risk values indicated that Arsenic, cadmium and nickel might pose significant health risks to consumers. Therefore, biomonitoring of heavy metal accumulation in tissues of fishes must be put into consideration by regulatory authority.