RELATIVE EFFECTIVENESS OF PU-239 AND SOME OTHER INTERNAL EMITTERS FOR BONE CANCER INDUCTION IN BEAGLES

The toxicity ratio (relative effectiveness per gray of average skeletal dose) has been estimated for bone cancer induction in beagles injected as young adults for a number of bone-seeking internal emitters. These experiments yielded calculated toxicity ratios (+/- SD) relative to Ra-226 = 1.0 of Pu-239 = 16 +/- 5 (single exposure to monomeric Pu) and 32 +/- 10 (continuous exposure from an extraskeletal deposit in the body), Ra-224 = 16 +/- 5 (chronic exposure) and approximately 6 +/- 2 (single exposure), Th-228 = 8.5 +/- 2.3, Am-241 = 6 +/- 0.8, Ra-228 = 2.0 +/- 0.5, Cf-249 = 6 +/- 3, Cf-252 = 4 +/- 2, Sr-90. = 1.0 +/- 0.5 (for high doses) and 0.05 +/- 0.03 (for low doses) and 0.01 +/- 0.01 (for extremely low doses). Because no skeletal malignancies were observed among beagles given only Es-253, the toxicity ratio is undefined.