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%.
