Asa river is a major river designated to supply millions of people of Ilorin, Kwara State, Nigeria potable water for drinking but its managements is of grave concern due to anthropogenic activities. Thus, evaluation of genotoxicity of this river was carried out by subjecting the water samples and fish therein to three bioassays (Micronucleus (MN) assay, Ames test and SOS-chromo test). Physicochemical parameters and heavy metals were analysed at three different stations (Aliara (SI), Unity (SII)

more »

... and Tuyil (SIII)) of the river. In SII, most of the heavy metals analysed were above the acceptable limits compare to SI and SIII. The peripheral erythrocyte of the fishes (Oreochromis niloticus, Synodontis batensoda, Synodontis eupterus, Clarias gariepinus and Clarias angullaris) at SI and SII stations showed a significant (p<0.05) induction of MN and different nuclear abnormalities (NA). Water samples from the three stations subjected to Ames test (Salmonella typhimurium TA100) and SOS chromotests (Escherichia coli PQ37) at 25%, 50% and 100% concentrations showed statistically significant (p<0.05) induction of DNA damage at all concentrations in the two tester strains, thus indicating base-pair substitution mutation and excision-repairdeficient, respectively, by the water samples. Therefore, drinking of this water and/or consumption of fish from this river should be taken with caution to avoid a carcinogenic risk.