| Abstract: | Male Syrian hamsters were scheduled to be exposed by inhalation approximately every 60 days for 1 year (7 exposures) to aerosols of 239PuO2 beginning at 84 days of age. Other hamsters were exposed once when 84 or 320 days of age. Plutonium-239 deposited in the lungs by the repeated inhalation exposures was cleared from the lungs at a rate similar to that following a single inhalation exposure. The incidence of radiation pneumonitis, bronchiolar epithelial hyperplasia, and alveolar squamous metaplasia were the only lesions that were related to radiation dose. Only two primary lung tumours were found among the hamsters exposed to 239PuO2. No primary lung tumours were found in the control hamsters. It was concluded that the incidence of lung tumours was not increased by the protraction of the alpha radiation dose to the lungs from repeated inhalation exposure. |
