The influence of age, sex and smoking habits on the background level of fish-detected translocations.

Chromosomal aberrations have been used for biological dosimetry for many years but dicentric yield decreases with time after irradiation. Since translocation yields should persist in peripheral lymphocytes with time they should prove to be a better indicator in the detection of old and chronic exposures to ionising radiations. The precondition, however, is knowledge of the control level in healthy subjects exposed only to normal background and also knowledge of confounding factors. From 42 healthy subjects, aged between 21 and 73 years, about 120,000 FISH-painted cells were scored using DNA probes for chromosomes 2, 4 and 8, and an all-human centromere probe. The statistical analyses revealed no influence of gender on the translocation frequency. Smoking habits-even a daily consumption of >30 cigarettes-seem to have only a marginal impact on the translocation yield, whereas an age-dependence has been established. Because of the high background level of translocations and the variation in the frequency between subjects, the lowest detectable limit for radiation exposures should be between 0.3 and 0.5 Gy, assuming that blood stem cells have a similar radiation sensitivity to that of peripheral lymphocytes for the induction of translocations.