Carcinogenicity of Inhaled Plutonium-238 in the Rat

III). Only 1% of the initial alveolar lung burden remained in the lung at 1 year, decreasing to 0.3% by 600 days after exposure. The 23Pu body burden was 25% of initial alveolar burden at 1 year, decreasing to 12% by 1000 days after exposure; about half of the body burden was found in the skeleton at these times. The cumulative radiation doses to the lung at 2 years after exposure were 9 rads (I), 32 rads (II), and 375 rads (III). Unexposed controls exhibited a median survival tine of 825 days as compared to experimental survival times of 650 days (I), 675 days (II), and 550 days (III). The incidence of lung tumors in controls was 1.1% as compared to incidences in 23Pu-exposed rats of 6.6% (I), 20.0% (II), and 25.0% (III). The incidence of all tumors, other than mammary tumors, was 4.3% in unexposed controls, and in 238Pu-exposed rats, 26.7% (I),