Urinary excretion of tritium following exposure of man to HTO--a two exponential model.

Data on urinary excretion of tritium by a 41-year-old male who accidentally inhaled (or ingested) tritium, presumed to be in the form of HTO, are presented along with an interpretation of these data and an estimate of the radiation dose delivered to tissues. Measurements of levels in urine were made as long as 255 days after the intake of the tritium. The data could be represented as a sum of two exponential terms, one with a half-life of about 9 days, the other of about 34 days. The total dose to body water was estimated to be about 16 rem, the long-term exponential contributing about 2% of the total. A two-compartment model was applied to the data. Equations were derived for the amounts of tritium in each compartment, and an estimate was obtained for the total dose in any tissue, based on a comparison with the content of hydrogen in the tissue. This method of estimating the dose may be applicable for other radionuclides and compounds. It assumes the stable element and its radioactive isotope behave similarly, or identically, in the body, but does not involve assumptions concerning the mathematical form of the retention function.