Inhalation Carcinogenesis of High-Fired 239 PuO 2 in Rats

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Abstract
Wistar rats were given a single, nose only exposure to freshly prepared, submicron size, high fired 239PuO2 particles, and the rats were examined over their life spans. A total of 343 rats were examined:295 exposed to 239PuO2, and 48 serving as unexposed controls. The activity median aerodynamic diameter of PuO2 was 2.5 .+-. 0.7 .mu.m. About 50% of initial alveolar deposition of 239Pu was cleared during the first 30 days after exposure. The alveolar retention half-time for 239Pu was about 250 days. A significantly increased incidence of malignant tumors was found only in the lung. Most of the lung tumors were adenocarcinomas followed in decreasing order of abundance by squamous cell carcinomas, hemangiosarcomas and 1 fibrosarcoma. The incidences of lung tumors were 0% in unexposed controls, 0% at an initial alveolar deposition of 0.18 nCi 239Pu, 10.0% at 5.0 nCi, 37% at 45 nCi and 53% at 180 nCi. An analysis of radiation dose to lung indicated that a significantly increased incidence of lung tumors occurred at lung doses of > 78 rads.