Cytogeno Toxicity Evaluation of Waste Water Effluent Discharged from Service Station using Allium Cepa Bioassay

Abstract

Industrial effluents are a main source of toxicants which cause adverse effects on flora, fauna and human health. In order to determine the cytogeno-toxic effects of effluents from service station, Allium cepa bioassay was used. Effluent samples were collected from discharge point and physiochemical characters were evaluated. In growth inhibition assay, root lengths of Allium cepa were measured after 7 days ' exposure in effluents (O, 1,5, 75, and 100% concentration) to determine the EC50 (Effective concentration for 50% of growth inhibition). The genotoxicity assay was carried out after 48hrs exposure in effluents (0.01, 0.1, 1, and 10% concentration). Root tip cells were observed under the microscope and the mitotic index (MI), frequency of aberrant cells were calculated. The values of physiochemical characteristics were within the national tolerance limits specified for waste water. There were strong correlations between the concentration and growth inhibition (R2 = 0.97). Effluent had 50% (EC50) of growth inhibitory effects in 80 % of the discharged concentration. The root growth retardation was significantly concentration dependent (P < 0.05). MI values were decreased and total number of aberrated cells were increased with increasing concentration. The dominant aberrations were sticky meta and sticky anaphases. The damages, including bridges, vagrants and c-metaphases and polar slips were also observed in low effluent concentrations. It is concluded that the toxic effect and growth inhibition can be reduced further by diluting the effluent. The proposed A.cepa bioassay is a reliable tool for this study. Genotoxic effects of other industrial effluents can also be monitored by using this assay