Data on urinary excretionof tritium hy a 41.year-oltl male who accidentally inhaled (or ingested) tritium, presumed to h e In the form of HTO, a r e presented along wlth an interpretation of these data and an e-timate of the radiation dose delivered to tissue<. JIeasurements of levels in urine were made as long as 255 clays after the intake of the tritium. The data could he represented as a sum of two exponential terms, one with a half-life of about 9 clays, the other of ahout 31 day.:. The total dose t o body water was estlmated to be ahout 16 rem, the long-term esponentlal contributing about 2"b of the total. A two-compartment model was applied to the data. Equations were derived for the amounts of tritium i n each compartment, and an estimate was obtained for the total tloae in a n y tisaue, ha.;ed on a comparinon with the content of hydrogen in the ti;iue. This method of estlmatlng the dose may he applicable for other raclionuclide~ anti compound-. I t assumes the stable element and Its radioactive isotope hehaw similarly, or itlenticallj-, in the hotly, but does not involve assumptions concernunp the mathematical form o f t h e retention function.

Two groups of 11-week-old swine (40 miniature and 40 domestic swine) received a single oral administration of 1.9 X 10(8) Bq (5.2 mCi) of 241Am citrate, and groups of eight animals, four of each type, were killed and sampled at 1, 2, 4, 8, 16, 24, 48, 72, and 96 h and 30 days later. Uptake and excretion patterns of the radioactivity appeared to occur in three phases: rapid uptake, rapid excretion, and then a slower excretion. All animals were systematically dissected, and the eviscerated carcasses were autoclaved for separation of bone and muscle. The predominant site of deposition was bone, and autoclaving had little effect on releasing 241Am from either bone or muscle. The maximum fractional gastrointestinal absorption of 1.1 X 10(-3) occurred 8 h after radionuclide administration. The tissue distribution data suggest partitions of 50, 20, and 30%, for bone, liver, and other soft tissues, respectively. Two metabolic models were evaluated: a modified Mewhinney-Griffith model and the ICRP 30 model to compare the biological data with model predictions. All models underestimated the actual early time data, but the fits to the experimental results were better at later times.

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