Late Somatic Effects in Female RF/Un Mice Irradiated with Single Doses of 14-MeV Fast Neutrons

Summary RF/Un female mice (∼ 1700 animals), 10-11 weeks old, were given a single whole-body irradiation with 14 meV neutrons (either 0, 50, 100, 200 or 400 rads) at a dose-rate of 1-2 rads/min. The mean age at death for 30-day survivors decreased with increasing dose. The incidence of thymic lymphoma and of myeloid leukaemia increased with dose. The incidence of ovarian tumours increased with dose to a maximum at 100 rads. Radiation enhanced the decline in haematocrit with age. Lens opacities developed in all irradiated groups by 3 months after exposure, progressed at a dose-dependent rate, and ultimately attained a level of severity which greatly exceeded any senile changes in the controls. Other common non-neoplastic diseases were not increased in incidence by irradiation, but all occurred earlier in irradiated animals. The results suggest that 14 meV neutrons are more effective than gamma-rays for shortening life and for producing lens opacities but not necessarily for inducing neoplasms, depending on the neoplasm in question.