Implications of postmortem human tissue analysis on biokinetic models for actinides

Changes and refinements to original biokinetic models, based on postmortem radiochemical measurements of the concentration and distribution of actinides in tissues obtained from volunteer donors with known occupational experience with actinides, are discussed with emphasis on applications to operational health physics. Analysis of five whole body donations to the United States Transuranium Registry indicates that the²³⁹Pu model put forth in ICRP Publication 30 is generally applicable, although there is a significant fraction missing from the model that is retained in the muscle. For²⁴¹Am, the more recent model put forth in ICRP Publication 48 fits the autopsy data better than the model in Publication 30, although the observed retention half-time in the liver is on the order of two to three years rather than 20 years proposed by the model. An estimated 20% of the initial systemic deposition for²⁴¹Am goes to the muscle, where it has a residence half-time estimated at ten years. For both Pu and Am, less than 5% of the skeletal actinide in the skeleton is found in the marrow. The highest concentrations appear to be associated with the periosteum and endosteum. A significantly greater fraction of inhaled Pu and Am is retained in the lungs than is predicted by current models. Differences in the actinide distribution between lung and the associated lymph nodes are observed in smokers as compared with non-smokers.