Biological effects of repeated inhalation exposure of Syrian hamsters to aerosols of 239PuO2. III

Syrian hamsters have been repeatedly exposed by inhalation to 169Yb-labeled aerosols of 239PuO2 to compare the resulting biological effects with those after a single exposure. Groups of Syrian hamsters have been repeatedly exposed to 239PuO2 to reestablish lung burdens (LB) of 2, 10, or 50 nCi 239Pu for the first 12 months after the initial exposure. Control Syrian hamsters were either nonexposed or exposed once or repeatedly to stable Yb2O3 or 169Yb2O3. Repeated exposures resulted in approximately a two-fold increase in the cumulative alpha radiation dose to the lungs compared with the Syrian hamsters exposed once. The radiation dose rate to the lungs was maintained at a relatively constant rate during the course of repeated exposures compared with the Syrian hamsters that had been exposed once. The median survival time in Syrian hamsters repeatedly exposed to reestablish LB's of 2 or 10 nCi was similar to those of control hamsters. Reestablishment of the LB at 50 nCi markedly shortened the median survival time. A bronchoalveolar carcinoma was observed in one Syrian hamster that died 512 days after the first inhalation exposure to 239PuO2 with an estimated dose of 1050 rads to the lungs to death