Toxicity of inhaled 238PuO2 in beagle dogs: A. Monodisperse 1.5 μm 238PuO2 particles. B. Monodisperse 3.0 μm 238PuO2 particles I

Studies on the metabolism, dosimetry, and biological effects of inhaled 238PuO2 particles have been initiated in Beagle dogs. To obtain essential information on the importance of the homogeneity or non-homogeneity of the radiation dose to lung (the hot particle question), dogs have been exposed to monodisperse aerosols (sigma/sub g/ less than 1.2) of 238PuO2 of either 1.5 μm or 3.0 μm aerodynamic diameter. By using monodisperse particles of these two sizes, the average dose to lung is held constant for a given initial lung burden (ILB) but the local alpha dose around the two sizes of particles varies by a factor of about 10. To date, 48 dogs have been exposed to each of the two particle sizes of 238PuO2 (total of 96 dogs) resulting in graded ILBs which range from 0.008 to 2.2 μCi/kg of body weight. Sixteen dogs exposed to a diluent aerosol are serving as controls. Of the total activity inhaled, the dogs exposed to 1.5 μm AD particles deposited 53 percent in total body and 43 percent in the pulmonary region while corresponding deposition values in the dogs exposed to 3.0 μm AD aerosols were 73 percent and 45 percent. All the dogs are surviving with no detectable abnormalities at from 10 to 293 days post-inhalation exposure. It is anticipated that an additional 48 dogs (24 for each particle size) and 8 controls will be added to these dose-response studies over the next few months. In addition, a serial sacrifice study will be initiated to determine the radiation dose pattern resulting from inhalation of these monodisperse sizes of 238PuO2. (U.S.)