The micronucleus assay in human lymphocytes: screening for inter-individual variability and application to biomonitoring.

Micronuclei levels were assessed in cytokinesis-blocked lymphocytes of 200 male and female healthy donors not occupationally exposed to genotoxic risks and of 33 male industrial painters handling genotoxic substances. Frequency of micronucleated cells was 9.87 +/- 3.1 per 1000 in the control population and was shown to have a large inter-individual variability. The study of factors contributing to this variability showed that only smoking could affect micronucleated cell rate, inducing an increase of 25%, whereas age and sex had no effect. Among the industrial painters, frequency of micronucleated cells averaged 18.30 +/- 7.39 per 1000: the difference between the two populations studied was shown to be statistically significant by the Mann-Whitney rank sum test (one-sided U test) and indicated that exposed painters need preventive measures.