The frequencies of micronuclei in cultured cytokinesis-blocked lymphoc
ytes of an urban industrial population of 188 persons were determined.
For the mean and SD, 16.0 +/- 7.3 per 1000 CB cells were obtained. A
slight but definite age dependence - appr. 0.2 parts per thousand incr
ease per year on average - was indicated by thorough statistical analy
sis.