Lung clearance and translocation of 239Pu and 244Cm in rats following inhalation individually or as a mixed oxide.

Wistar rats were exposed via inhalation to aerosols of 239PuO2, 244Cm oxide or a mixed Pu-Cm oxide with an activity ratio of about 1:1. Activity in lung and several extrapulmonary tissues were examined up to 120 d after exposure to determine whether calcining Pu and Cm together affected lung clearance or translocation to other sites in the body for either nuclide. Initial deposition was about 1,200 Bq (32 nCi) for 239PuO2, 4,200 Bq (115 nCi) for 244Cm, and 2,400 Bq (65 nCi) total alpha for the mixed oxide. The kinetics of single nuclides were as expected, with Pu oxide confined mainly to lung at all times and cleared with a half-time of 42 d. Curium was translocated rapidly to liver, with a peak activity of about 10% of the initial alveolar deposition at 7-14 d. Skeleton activity increased gradually, amounting to 12-15% of initial deposition near the end of the study. Lung clearance of Cm was more rapid than for Pu, with about 13% of Pu and less than 5% of Cm remaining at the end of the experiment. Both Pu and Cm remained in the lung somewhat longer when administered as a mixed oxide than the respective nuclides administered singly, and virtually all activity in the body was confined to the lung. Translocation of Cm to extrapulmonary tissues was almost entirely prevented by incorporation into the PuO2 matrix. Therefore, calcining the two radionuclides together in an aerosol altered the kinetics of both following inhalation in rats, but most dramatically for 244Cm. The resulting change in radionuclide distribution for the lung and the body following such a mixed inhalation exposure would presumably alter the long-term health effects compared to those seen with the pure compounds.