Comparative stochastic effects of inhaled alpha- and beta-particle-emitting radionuclides in beagle dogs

The stochastic effects of inhaled, insoluble particles of alpha- or beta-particle-emitting radionuclides were compared in dogs. Male and female beagle dogs were exposed briefly by nasal inhalation to relatively insoluble aerosols of (239)PuO(2) or (144)Ce in fused aluminosilicate particles (FAP) and observed for cancer for their lifetimes. The initial lung burden and retention of each radionuclide was determined by whole-body counting of the emissions from (144)Ce-(144)Pr- or (169)Yb-labeled (239)PuO(2). Lung doses were calculated for each dog from these data. The lung doses ranged from 0.21 to 1200 Gy for (144)Ce FAP and 1.6 to 58 Gy for (239)PuO(2). Dogs with doses to the lung of about 60 Gy or greater from (144)Ce or about 2 Gy or greater from (239)PuO(2) had an increased incidence of lung carcinomas. In dogs exposed to (144)Ce FAP, three organs were targets for neoplasia: lung, tracheobronchial lymph nodes, and heart. The insoluble FAP carried to the lymph nodes draining the lung delivered high radiation doses to the nodes and adjacent heart, resulting in hemangiosarcomas of these organs. In the lung, high radiation doses induced hemangiosarcomas and carcinosarcomas. At lower doses, carcinomas of various histological patterns were induced in the lung. In dogs exposed to (239)PuO(2), the lung was the sole target organ for neoplasia. Nearly all of these neoplasms were carcinomas of various histological patterns. These results indicated that relatively low doses of alpha-particle radiation can induce pulmonary cancers, but relatively large doses of beta-particle radiation are required. In addition, inhaled beta-particle emitters can also induce cancers in lung-associated lymph nodes and heart at these larger absorbed radiation doses.