Effect of time post-exposure on the effectiveness of bronchopulmonary lavage in removing inhaled 144Ce in fused clay from beagle dogs

The effectiveness of a single, unilateral bronchopulmonary lavage in removing relatively insoluble radioactive material from the lung was evaluated at various times after inhalation exposure to radioactive aerosol in dogs. Twenty-seven beagle dogs exposed to aerosols of 144Ce fused clay achieved initial lung burdens ranging from 23 to 73 μCi/kg body weight. The dogs were divided into nine groups of three dogs each and each group was given a single bronchopulmonary lavage of the right lung at one of the following times after exposure; 2 hr, 2, 4, 7, 14, 28, 56, 128 and 196 days. Mean percentages of the right lung burden recovered in the lavage fluid were: 45, 25, 22, 19, 25, 12, 17, 14 and 17%, respectively. After the lung lavage, the dogs were sacrificed, dissected, and the tissues analyzed. At least 93% of the sacrifice body burden was found in the lungs out to 56 days after exposure. At 128 and 196 days after exposure, lung burdens were means of 88 and 81% of the sacrifice body burden, respectively. The results indicate that a sizable percentage of the insoluble particles in the lung remains accessible to removal by bronchopulmonary lavage for periods up to 6 months after exposure; however, translocation from the lungs to other tissues increases with time. Also, depending on the isotope, the total radiation dose delivered to lung before lavage can become so large at longer times after exposure that removal of material from the lung has little effect in reducing total cumulative dose to tissues.