Abstract: The micronucleus test (MCNT) on root tip cells of Vicia faba was used to monitor the cytogenetic toxicity of black carbon. The results showed that when black carbon concentration was 10-40 mg/L, no significant effect of black carbon on micronucleus ratio, karyokinesis index and multi-nucleolus ratio was found compared with that of the control（P>0.05）. However, as the concentration of black carbon increased to 80-320 mg/L, the micronucleus ratio and multi-nucleolus ratio significantly rose（P<0.05）, while the karyokinesis index significantly decreased（P<0.05）. At 320 mg/L, the micronucleus ratio was 38.9 ‰，the multi-nucleolus ratio was 35.91%, and karyokinesis index was only 1.075%. The results suggested that the genetic toxicity of black carbon at low concentrations was low and had a certain extent genetic toxicity at high concentrations.

Key words: black carbon, Vicia fabaroot tip, micronucleus, karyokinesis, multi-nucleolus