Evaluation of Cytogeno toxic Effects of Automobile Service Station Effluents on Allium cepa: A Comparative Study of Treated and Untreated Samples

Abstract

Effluents from automobile service stations are a major source of water pollution, releasing toxic substances into aquatic systems that pose risks to both ecosystems and human health. This study evaluated the cytotoxic and genotoxic effects of treated and untreated effluents from selected service stations near the Vavuniya Tank using the Allium cepa assay, a well-established bioindicator system. The genotoxicity assay was conducted after 48 hours of exposure to effluents at concentrations of 0.01%, 0.1%, 1%, and 10%, with tap water serving as the control. The Allium cepa assay followed standard protocols, where cytogenetic parameters such as mitotic index (MI), limit value of cytotoxicity (LCV), phase index (PI), and chromosomal aberrations were evaluated under oil immersion at high magnification (2500 cells per sample). Results revealed that cytogenetic responses varied with effluent treatment and concentration. A concentration-dependent reduction in MI was observed, with the control, treated, and untreated effluents showing 38.96%, 21.40%, and 17.44% MI, respectively, at 10% concentration. Similarly, LCV decreased with increasing concentrations: from 100% (control) to 54.93% in treated and 44.76% in untreated effluents at 10%. Chromosomal aberration analysis showed that both treated and untreated effluents induced abnormalities, with the frequency of aberrations increasing with concentration. Untreated effluents exhibited genotoxic effects, producing higher numbers of abnormal interphases (54) and sticky prophases (26), compared to treated effluents (abnormal interphases (31) and sticky prophases (21)). Dominant aberrations included abnormal interphase, sticky prophase, and sticky metaphase. Overall, both treated and untreated effluents demonstrated cytotoxic and genotoxic effects on Allium cepa root meristem cells, with untreated effluents exerting a greater impact. The severity of these effects increased with effluent concentration, peaking at 10%.