Chromosomal analyses in vinyl chloride exposed workers. Results from analysis 18 and 42 months after an initial sampling.

In a previous study (Purchase et al., Mutation Res., 57 (1978) 325-334) it was reported that 57 workers occupationally exposed to vinyl chloride had an increase in the incidence of chromosomal abnormalities in their lymphocytes by comparison with 24 control workers. Since that time (July 1974) threshold limit values for vinyl chloride and plant exposure levels have been reduced. In the present study, 2 further samples from the same population of workers have been analysed for chromosomal aberrations 18 and 42 months after the initial sampling. At 18 months, 21 VC workers and 6 on-site controls were investigated as were 23 workers and 8 on-site controls at 42 months. In the second sampling there was a tendency to an increase in chromosomal abnormalities of VC-exposed workers except in those people who had changed occupation. By the third sampling, however, there was a decrease by comparison with previous samplings and the levels of abnormalities had returned to values similar to those of the controls. Thus, reduction in exposure to vinyl chloride is accompanied by a reduction in the chromosomal abnormalities to levels indistinguishabe from those of controls.