Plutonium Inhalation Studies-VII Bronchiolo-alveolar Carcinomas of the Canine Lung Following Plutonium Particle Inhalation

Abstract

Inhalation of 239PuO2 particles by 40 beagle dogs caused spontaneous death in 10 animals having lung burdens of from 0.5 to 2.0 [mu]c. Deaths occurred at 29 to 56 months post-exposure. The pathologic effects observed in the lungs of these animals consisted primarily of severe fibrosis followed by alveolar ceU hyperplasia, and bronchiolar and squamous types of metaplasia. Five of the animals showed bronchiolo-alveolar carcinomas, an incidence of 13% as compared to a primary lung tumor incidence of 0.2% in canine necropsy material. All neoplasms originated in peripheral lung areas in association with particle retention, fibrosis, and bronchiolo-alveolar metaplasia. The irradiated, proliferating cells, comprising the hyper-plastic and metaplastic response to lung scarring, appeared to be the nidus of tumor formation. Metastases were seen in one dog.