Tentative estimate of the risk of chromosomal disease due to radiation-induced translocations in man.

An attempt to estimate one of the parameters establishing the risk of occurrence of abnormal live-born progeny by malsegregation of radiation-induced translocation is reported. A sample of 247 2-break translocations induced by gamma-rays in human lymphocytes was studied in relation to the minimal possible imbalance they could induce in gametogenesis. These imbalances were compared with chromosomal trisomies and monosomies known to be compatible with life after birth in man. It is concluded that at least 106 out of 247 translocations should not give viable products in cases of malsegregation. A second comparison, with translocations ascertained in human subjects for various reasons, led to the conclusion that about 2/5 of the radiation-induced translocations might involve a risk of partial trisomies or monosomies. Cell survival and frequency of meiotic malsegregations are other parameters needed to make a correct estimate. A short discussion shows the difficulty of such estimates from inter-specific comparisons.