Current status of Utah long-term 239Pu studies

Osteosarcomas have been the chief cause of death in the Utah young adult beagles injected intravenously with 239Pu citrate solution. There was nearly a 100% incidence of bone sarcomas above the 0.015 μCi/kg dose levels. At the 0.015 μCi/kg dose level there was a 29% (4 of 14) incidence. The latent period lengthened with decreasing injected dose. The only other pathology was liver regenerative foci occurring at doses as low as 0.0018 μCi/kg and an incidence of 12% (3 of 25) bile duct carcinomas at the 0.048 and 0.015 μCi/kg dose levels. Studies using older (5-year) and growing (3-months) beagles, young adult St. Bernards and young adult beagles injected with polymeric 239Pu showed variation in sensitivity for bone tumour induction. The polymeric model represents a continuous cycling of 239Pu from the liver to a mature skeleton and the St. Bernard model typifies the relationship between high spontaneous and radiation-induced tumour sensitivity. No results are available for the older adult, but one bone tumour in a growing beagle injected with 0.3 μCi/kg suggests decreased sensitivity. There is increased sensitivity in St. Bernards and polymeric injected dogs for bone tumour induction. (author)