Abstract: OBJECTIVE: The micronucleus test with Vicia faba root tip cells was used to study the genotoxicity of tap water from three northern cities. METHODS: 12 samples:including the source water,chlorinated water and supply tap water,were collected from six waterworks in the northern cities of A,B,C. The samples were used to treat Vicia faba root tip cells directly. Micronuclei frequencies and pollution index (PI) were determined and statistics analyses were performed to evaluate differences in micronuclei rates among different samples. RESULTS: Among the 3 waterworks in city A,the chlorinated water in waterwork # 3 induced higher micronuclei rates than the negative control,and the PI was moderate. Other water samples from city A did not induce micronuclei. In city B,the chlorinated water induced higher micronuclei rate than the negative control,and the PI was slight. The other water samples did not induce micronuclei. However,the PI for the supply tap water was slight. In city C,the micronuclei rates induced by all 3 water samples were not different from that of the negative control. However,the PI for all samples were slight and the order of the PI levels was:chlorinated water > supply tap water > source water. CONCLUSION: Based on the evaluation using micronuclei rates and PI,the mutagenic potential of chlorinated water was the strongest. In addition,the water quality of city A was better than that in cities B and C.

Key words: Vicia faba root tip cells, micronucleus frequency, waterworks sample, water quality evaluation