Comparative Toxicity of 226 Ra,  239 Pu,  241 Am,  249 Cf, and 252 Cf in C57BL/Do Black and Albino Mice

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Abstract
Groups of C57BL/Do (black and albino) mice were injected with graded activities of 226Ra, 239Pu, 241Am, 249Cf or 252Cf and were followed throughout life. Bone sarcoma was the principal radiation-induced end point, and the risks associated with average skeletal doses of the 4 transuranium radionuclides, relative to Ra, were determined. The relative biological effectiveness (RBE) was calculated for each emitter by dividing its risk coefficient (bone sarcomas/106 mouse-rad) by the risk coefficient for 226Ra. Combined data for males and females in black and albino mice gave the following values .+-. SD for the RBE relative to 226Ra = 1.0: 239Pu = 15.3 .+-. 3.9, 241Am = 4.9 .+-. 1.4, 249Cf = 5.0 .+-. 1.4 and 252Cf = 2.6 .+-. 0.8. About 70% of the tumors occurred in the axial skeleton, and the risk coefficient for females averaged .apprx. 4-fold higher than for males when all 5 nuclides were included. The RBE of fission fragment irradation from 252Cf for cancer induction, relative to .alpha.-irradiation, for the combined data in all animals given 252Cf and 249Cf, was 0.02 .+-. 0.28, in agreement with the calculated theoretical vaue of 0.03, based on the ratio of summed track lengths in tissue.