Genotoxic and toxicity of spent engine oil on Clarias gariepinus
In most of developing nations, pollution of water resources has become a serious problem. Apparently, human and ecological disorder experienced in industrial settlements as a result of improper disposal of chemicals such as engine oil calls for careful surveillance on the state of the environment. The acute toxicity concentrations of 100, 200, 300, 400 and 0 mL L-1 were used to determine the 96 h Lethal Concentration (LC50) value of spent engine oil which was found to be 2.75 (562 mL-1). Definitive test was also carried out every 24 h over a four days period (96 h). Cytogenetic evaluation using micronucleus assay was carried out on Clarias gariepinus juveniles in the laboratory after exposure to sub lethal concentrations of spent engine oil for 14 days. The One way ANOVA was used to analyze the significant difference (p<0.05) in the analysis of variance for micronucleus and bi-nucleated cells. Micronucleus assay showed more bi-nucleated cells than micro nucleated cells in Clarias gariepinus juveniles exposed to sub lethal concentrations of spent engine oil. The species showed varying degrees of micronuclei and bi-nucleated frequencies in their peripheral erythrocytes. Cytological examinations showed bi-nucleated cells and micronucleus formation in erythrocytes of the fish in the test solution. However, the significant difference was not wholly dependent on the period of exposure and the concentration of spent engine oil used. The results show that spent oil commonly discharged in the environment is capable of causing genetic damage to Clarias gariepinus at high concentrations of the assay; this can be employed for the evaluation and the assessment of water pollution and aquatic mutagens. Spent engine oil is toxic to fish and causes cytogenetic changes in cells of fish. Fish are susceptible to spent engine oil; therefore the release of spent engine oil into the aquatic environment should be discouraged.