Data are presented on the concentrations of plutonium in air, precipitation, total diet, milk and human tissue samples collected in the United States during the period 1964-1966. These data show that 23gPu in monthly composites of particulates collected from surface level air in Winchester, Massachusetts, ranged from 0.047 to 0.437 fCi/mS from May 1965 to April 1966, and that the average 23BPu to ' OSr ratio was 0.019 and the average 238Pu to =' Pu ratio was 0.04. Monthly deposition of =' Pu from precipitation over the same period ranged from 0.86 to 8.8 pCi/m2. Children's diets collected from six widely spaced geographical areas showed average concentrations which ranged from 2.7 to 5.8 fCi/kg for monthly samples for the period July-December 1965. Milk samples collected in a similar manner over a similar period showed concentrations which were not significantly different from zero.

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Patients who have received injections of colloidal thorium dioxide (Thorotrast) into the circulatory system constitute a pool from which information on the effects of long-term exposure to radiation can be obtained.The dosimetry of thorotrast is complicated by movement of the various daughter nuclides involved throughout the body. Radionuclide analysis of autopsy samples provides direct information on tissue concentrations of these nuclides which can be used for establishing the doses to organs of interest. This paper presents the results obtained on samples of tissues from two cases in the New England area. The first analyses, in each case, were performed about 24 hr post mortem.The concentrations of 228Ra, 228Th, 224Ra and 212Pb were determined by repetitive gamma examination over a period from 24 hr to 30 days. The samples were then dissolved and the concentrations of 232Th and 228Th determined by radiochemistry. The data indicate (1) that approximately 65% of 228Ra, the first daughter of 232Th is eliminated from the body, (2) that the parent 232Th is translocated to bone, and (3) that considerable quantities of 2zoRn are liberated to blood. The effects of these findings on dosimetry are discussed. The autopsy findings are compared with whole body counting data, available on one of the patients.

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