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For more than three decades, the United States Transuranium and Uranium Registries (USTUR) have studied the biokinetics, dosimetry, and biological effects of plutonium, uranium, and americium through voluntary postmortem tissues from persons with known intakes. Radiochemical analyses of tissue obtained at autopsy have shown that plutonium and americium have different biokinetics and an appreciable deposition in the soft tissues of the body as well as the known depots in skeleton and liver. Studies of whole-body Thorotrast donors to the USTUR indicate that commonly accepted risk coefficients for alpha induction of bone sarcoma may be too high while those for leukemia are a factor of six too low. This review considers these and other major contributions of the USTUR.

The distribution of thorium in the tissues of a whole body donor to the United States Transuranium and Uranium Registries is described. This case, identified by the USTUR as Case 0212, had two documented intakes of plutonium and americium from occupational accidents while employed at Hanford but no known occupational exposure to thorium. Concentrations of 239+240Pu, 241Am, and 232Th in the tissues are compared and the distribution of these isotopes in this case is evaluated. The distribution data for 232Th are compared to those from previous studies of thorium in human tissues resulting from environmental exposure and to an individual exposed to Thorotrast (colloidal ThO2) in a medical diagnostic procedure. The 232Th distribution data from this work are also compared against ICRP 30 and ICRP 69 models for the behaviour of thorium in the human body.