Metabolism of organically bound tritium in man.

The classic methodology for estimating dose to man from environmental tritium assumes that all tritium, whether organically bound or free, enters directly into man's free body water compartment and is uniformly distributed as tritiated water. This methodology ignores the fact that organically bound tritium in foodstuffs may be directly assimilated in the bound compartment of tissues without previous oxidation. A four-compartment model consisting of a free body water compartment, two organic compartments, and a small, rapidly metabolizing compartment is proposed. The utility of this model lies in the ability to input organically bound tritium directly into organic compartments representing tissue solids. The model will be used to illustrate the potential importance of organically bound tritium to cumulative dose estimates. It is found that organically bound tritium in foodstuffs can increase cumulative total body dose by a factor of 1.7-4.5 times the free body water dose alone, depending on the bound-to-loose ratio of tritium in the diet.