Activity of vinyl chloride monomer in the mouse micronucleus assay

C57Bl/6J mice of both sexes were exposed to 50 000 ppm vinyl chloride monomer (VCM) for 6 h. Animals were killed 24 and 48 h after cessation of exposure and examined for the presence of micronuclei in bone marrow cells. At 24 h the control incidences of micronuclei per 1000 polychromatic erythrocytes (PCEs) were 2.6 (male) and 1.2 (female), while in animals exposed to VCM the incidences were 24.6 (male) and 25.0 (female). At 48 h the control incidences were 2.2 (male) and 1.6 (female) and in the VCM exposed animals 7.2 (male) and 4.4 (female).