Application of a canine (238)Pu dosimetry model to human bioassay data

摘要

Associated with the use of 2(sup 238)Pu in thermoelectric power sources for space probes and power supplies for cardiac devices is the potential for human exposure to (sup 238)Pu, primarily by inhalation. In the event of human internal exposure, a means is needed for assessing the level of intake and calculating radiation doses. Several bioassay/dosimetry models have been developed for (sup 239)Pu. However, results from studies with laboratory animals have indicated that the biokinetics, and therefore the descriptive models, of (sup 238)Pu are significantly different from those for (sup 239)Pu. A canine model accounting for these differences has been applied in this work to urinary excretion data from seven humans occupationally exposed to low levels of an insoluble (sup 238)Pu compound. The modified model provides a good description of the urinary excretion kinetics observed in the exposed humans. The modified model was also used to provide estimates of the initial intakes of (sup 238)Pu for the seven individuals; these estimates ranged from 4.5 nCi (170 Bq) to 87 nCi (3200 Bq). Autopsy data on the amount and distribution of (sup 238)Pu retained in the organs may be used in the future to validate or refute both these estimates and the assumptions used to formulate the human model. Modification of the human model to simulate an injection exposure to (sup 239)Pu gave patterns of retention in the organs and urinary excretion comparable to those seen previously in humans; further modification of the model using fecal data (unavailable for the subjects of this study) is indicated.