APPLICATION OF A CANINE PU-238 BIOKINETICS DOSIMETRY MODEL TO HUMAN BIOASSAY DATA/

Associated with the use of Pu-238 in thermoelectric power sources for space probes is the potential for human exposure, primarily by inhalat ion and most likely as (PuO2)-Pu-238. Several models have been develop ed for assessing the level of intake and predicting the resulting radi ation dose following human exposure to Pu-239. However, there are indi cations that existing models do not adequately describe the dispositio n and dosimetry of Pu-238 following human exposure. In this study, a c anine model that accounts for these differences has been adapted for u se with human excretion data. The model is based on existing knowledge about organ retention of plutonium. An analysis of the sensitivity of the model to changes in aerosol-associated properties indicated that predictions of urinary excretion are most sensitive to changes in part icle solubility and diameter and in the ratio of fragment:particle sur face area. Application of the model to urinary excretion data from sev en workers exposed to a Pu-238 ceramic aerosol gave estimated intakes of 390-8,200 Bq and associated initial pulmonary burdens of 80-1,700 B q. The resulting 50-y dose commitments to critical organs per Bq of Pu -238 intake were estimated to be 0.5 mSv for the thoracic region, 0.2 mSv for the liver, and 1 mSv for the bone surfaces.