Journal of Sci. Res. Dev. 2013, Vol. 14, 25 - 34 Cytogenotoxicity Assessment of a University Borehole Water Supply Using The Allium cepa Test Daniel I. Olorunfemi 1* , Chukwuedozie R. Ofomata 1 and Chibuisi G. Alimba 2 1 Department of Plant Biology and Biotechnology, University of Benin, Benin City, Nigeria. 2 Cell Biology and Genetics Unit, Department of Zoology, University of Ibadan, Nigeria. ABSTRACT The cytotoxic and genotoxic potentials of borehole water supply in six halls of residence of the University of Benin main campus was investigated using the Allium cepa test. The water samples were also analysed for some physico-chemical parameters and heavy metals. The samples induced significant (p < 0.05) inhibition of root growth and induction of chromosome aberrations in A. cepa compared to tap water. The observed cytogenotoxic effects were believed to be caused by the physico-chemical parameters and heavy metals which were present in high concentrations in the borehole water samples than tap water. These findings suggest that the investigated water samples may be contaminated by wastewater from sewage and solid waste leachates and may be of health risk to human and animal populations in case of exposure during consumption. Keywords: Allium cepa, Borehole water, Cytogenotoxicity, Public health. INTRODUCTION The importance of water to humanity includes drinking, cooking, industrial, agricultural and recreational purposes. Since cellular composition of biological systems contains about 75% water (Batmanghelidj, 1997), the provision of safe drinking water is a priority and basic requirement for human development, quality health and well-being. Potable water supply to populations, mostly through pipe and borehole sources, is expected to be free from microorganisms, physical and chemical substances or may contain these substances to a minimum concentration below the permissible limits by regulatory authorities (Hart, 2004). Quality water is necessary for the normal human physiological functioning and in the prevention of health hazards (WHO, 1984). However, underground water supply in most countries is predisposed to heavy metal, organic and microbial contamination due to anthropogenic activities and may become unfit for human consumption and other domestic and industrial uses of water. This is due to increase in physico-chemical and heavy metal characteristics and microbial loads of these underground water supply (Adekunle et al., 2007; Okonko et al., 2008; Omofonmwan and Eseigbe, 2009) compared to the required standards by both national (SON, 2007) and international (WHO, 2006) regulatory authorities. In Nigeria, sequel to increasing industrialisation, population growth and urbanisation, which may result into unsanitary disposal of solid wastes, wastewater and agrochemicals into the environment (Alimba et al., 2006), reports from studies have shown that most surface and underground water supply for human use are contaminated (Okonko et al., 2008; Omofonmwan and Eseigbe, 2009). According to a study conducted by the United Nations Children’s Fund, about 52% of Nigerians make use of these unprotected underground water and surface water for their domestic and commercial activities (Adeyeye, 2006). Contamination of most surface and underground water has elicited both international and national concern on possible health risk associated with the consumption and utilisation of such water for both domestic and industrial uses. Available studies assessing these water supply for contaminations mostly considered well water from both rural and urban settlements and satchet water (nylon pure water) for microbial population density, physico- chemical properties and heavy metal concentrations *Correspondence : udanfem@gmail.com