Tumor Induction in B6C3F1 Mice by Californium-252

The tumorigenicity of 252Cf, a nuclide being used as a neutron source, was examined in B6C3F1 mice. Both sexes of mice were exposed to 252Cf at different doses of 0 (control), 12.5, 50 or 200 cGy at 6 weeks of age. They were observed for 13 months after exposure. Among the mice exposed to 200 cGy of 252Cf, hepatic tumor was found 55% in male and 29% in female, values being significantly higher than those of the unirradiated controls. Furthermore, the incidence of hepatic tumors increased dose dependently in both sexes (correlation coefficient in males r = 0.72, in females r = 0.98). Number of hepatic tumors and average tumor size correlated to the tumor incidence. Tumor sites were found most frequently in lobe 5 followed by lobe 3. Adrenal tumors in the female mice were observed only in adrenal cortex and also showed dose dependent increase (r = 0.995). Ovarian tumors were found with incidences of 14% in 200 cGy group and 30076 in 50 cGy group.