Internal exposure to plutonium and cancer formation. Experimental cancer formation by injection of plutonium

Findings on the experimental cancer formation due to injected Pu are reviewed and discussed about the characteristics of its tumorigenesis. Pu-239, an alpha emitter, is a bone-seeking and surface-seeking radionuclide which deposits in the endosteum from blood and often induces osteosarcoma (OS) in animals. Other bone seekers like 90Sr, a beta emitter, and 226Ra, alpha emitter, seek the bone mineral (volume-seekers) and induce OS similarly, but their potential carcinogenicity differs from each other: e.g., in beagle dogs, when the potential of OS carcinogenicity of 90Sr is 1.0, it is 60 for 226Ra, and 960 for 239Pu. The tendency is also seen in mice and rats. In mice, the malignant hematopoietic disease like leukemia is also induced by the Pu injected, but in dogs, such disease is scarcely reported. In workers of the nuclear weapon factory in Mayak, solid lung, liver and bone tumors are reported to be caused by the inhaled 238/239Pu, and leukemia, from external gamma exposure. At present, it seems that osteosarcoma alone is related with the internal exposure to Pu alpha ray in mammals. (T.T.)