Metabolism and Dosimetry of Tritium from Tritium Gas Contaminated Surfaces

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Abstract
Experiments by Hutchin and Vaughan on rats and by Eakins et al. on humans have shown that a surface contaminated by tritiated hydrogen gas (T2) that is brought into contact with intact skin will result in elevated concentrations of organically bound tritium (OBT) in urine, and in skin, at the point of contact. Johnson and Dunford evaluated the range of likely dosimetric consequences of this mode of tritium uptake, and Johnson and Peterman carried out a preliminary experiment in rats to better quantify the retention of this organically bound tritium in skin and in other tissue. Recently, experiments were carried out on rats exposed to T2 contaminated surfaces to extend the measurements of OBT in tissues to several months post exposure; to measure the microdistribution of the OBT in skin tissue; to develop methods of measuring OBT in urine; and to evaluate the effectiveness of decontamination efforts after an exposure. Retention and excretion was followed for 56 days post exposure. Elevated OBT was observed throughout this period, most notably in skin and liver. Autoradiography of skin sections at the point of contact indicates that the OBT is concentrated in the basal layer of the skin, in the epithelium of hair follicles, and in subcutaneous muscle. These data were used to relate the OBT in urine to doses to the skin at the point of contact. Various ion exchange columns were evaluated for their ability to separate out the OBT from the HTO but were not found to be effective. A double distillation method is recommended. Protection by gloves against uptake varied from about a factor of 2 to 100, depending on glove material and length of exposure. Barrier creams did not provide much protection. Washing the skin with a detergent or alcohol immediately after exposure reduced uptake and retention in skin. The effectiveness of this decontamination method decreases rapidly with time.