Comparison of ICRP 67 and Other Plutonium Systemic Model Predictions with the Biokinetic Data from Nonhuman Primates

Despite the presence of a relatively large amount of human data available on the metabolism of plutonium, the experimental animal data is still important in constructing and parameterizing the biokinetic models. Recognizing this importance, the biokinetic data obtained from studies done by P.W. Durbin in nonhuman primates (NHP) were evaluated against the ICRP 67 systemic model and the two human models developed thereafter. The default transfer rates recommended for adult humans in these models predict the urinary excretion in NHP to a certain extent. However, they were unable to describe the fecal excretion rates several days post intake and the activities in skeleton and liver at the time of the death. These inconsistencies between the human reference models and the NHP biokinetic data are the result of metabolic and physiological differences between the species, as demonstrated by early biokinetic studies.