JFFICIAL USE ONL. Dr. Park, from the Pacific Northwest Laboratory, summarized a long list of plutonium studies being conducted at this installation. The main emphasis in these studies has been on the inhalation route of exposure. At the highest doses of plutonium the dogs die early from pulmonary fibrosis, At lower doses they die late in life from lung tumors. Assays of the tissues show that the highest concentrations of plutonium are in the regional lymph nodes. They have recently started a low dose study at six graded doses extending all the way down into the range of human exposures. He noted that plutonium-238 and plutonium-239 seem to behave quite similarly with respect to deposition, translocation, excretion, etc. In rats exposed to insoluble plutonium by the inhalation route, they are finding a wide variety of tumors. Dr. Park proposed that there is probably some cocarcinogenic interaction between plutonium and other carcinogens such as asbestos, cigarette smoke, etc. The group has screened a number of agents in rats in an attempt to influence the excretion rate of plutonium and has also studied the metabolism and effects of plutonium- 238 injected as microspheres. Dr. Park closed by outlining proposed research in some detail. Proposed studies include examination of the effect of particle size, contaminants in the plutonium, dosimetry, attempts at therapy, theoretical modeling and ancillary studies. Dr. McClellan described the research on alpha emitters being conducted at the Lovelace Foundation, At present a permanent facility is being constructed for the express purpose of studying inhalation toxicity of transuranic elements in dogs. They are looking at americium-241, curium-244, and plutonium-239 by the inhalation route in dogs and are studying californium-252 and amcricium-241, curtum-244, and plutonium-239 by the inhalation route in dogs and are studying californium-252 and americium-241 in rodents. The work at the Lovelace Foundation is unique in that they can make monodisperse aerosols of any desired particle size. This, then, enables them to vary each of the experimental variables independently. For example, they can give different dogs the same smeared dose to the lung by changing the particle size, they vary the local dose and the fraction of the lung irradiated by an enormous factor, They can also keep the local dose around the aerosols constant but vary the total smeared dose to the lung. This work very nicely complements the more empirical approaches being used in other installations. Dr. McClellan also reported on the results of the case of lung lavage. A worker at the Rocky Flats plant received an overexposure to plutonium-239,. He was treated at Lovelace and by lavaging the lung, they retrieved about the same amount by lavage as he excreted in the urine. The urinary excretion was higher than normal since the patient was treated with DTPA, Dr. Richmond, from the Los Alamos Scientific Laboratory, described the work with plutonium being conducted there. Rather than using the inhalation route of administration, they inject particles of various sizes intravenously. These then lodge in the lung and give high doses of local radiation to the area where they lodge. They propose to vary the number of particles, particle size, etc., so that they can look at varying smear doses, varying local doses, and various fractions of the lung irradiated. This work is just getting under way. OFFICIAL USE ONLY