Evaluation of lung burden following acute inhalation exposure to highly insoluble PuO2.

On 15 October 1965, a fire in a plutonium fabrication plant resulted in a largescale spread of plutonium oxide. The Rocky Flats body counter was used to measure the plutonium in the lungs of all employees working in the area. Of approximately 400 employees counted, 25 were found to have enough plutonium in their lungs to deliver a dose of 15 rem/yr or greater. Data from each employee were obtained with two scintillation detectors in contact with the subject's chest. The 60-keV photon peak of z41Am was used in the measurements. The 2 4 1 h content of the plutonium released in the fire was determined and the plutonium quantity was then determined from calibrations done on a chest phantom with similar z4lAm:239pu ratios. The plutonium consisted of "high-fired" PuO,. Particle size measurements of air samples collected after the fire indicated a 0.32-p mass median diameter (MMD) with a geometric deviation (og) of 1.83. Lung data so far show very slow clearance. This confirms the high degree of insolubility and the small particle size. On the average, 30 per cent of material initially deposited was cleared in 2-3 months. The remaining material is clearing very slowly with little or no measurable absorption into the bloodstream. INTRODUCTION SINCE June, 1964, plutonium inhalation cases have been under study in the Rocky Flats body counter.('B2) I t is known that estimates of lung burdens of plutonium can be made using the body counter if the amount of 2r1Am present in the exposure material is known. O n 15 October 1965, during a maintenance operation in which an attempt was made to unplug an oil coolant line on a lathe, plutonium metal chips caught fire. The fire occurred outside of a glovebox in a 70,000-ft2 plutonium production area. About 400 employees were working in the room. Even though the fire was extinguished in a few minutes, airborne contamination spread quickly throughout the area. Air sampler filters indicated a n activity range of greater than 1 ,uCi/m3 down to 10-6 ,uCi/m" a t the most remote locations. Because the contamination spread so rapidly, * C.S . Atomic Energy Commission Contract NO. AT(29-1)-1106. many employees were in high airborne contamination areas without respiratory protection. Those showing high levels of contamination about the nose and mouth were scheduled for body counting first, followed by those with lower contamination levels. As soon as a man was decontaminated externally, he went to the body counter. Within 2 hr after the fire the first person was counted. Fourteen people were counted on the first day and evening of the fire. Seven of these showed significant amounts of plutonium in the chest. Eighteen additional exposures were found in the following weeks. DTPA treatments were given by the medical department to eight of the first positive cases. T h e treatments did not enhance plutonium excretion in the urine, so they were stopped. Subsequent positive cases did not receive DTPA treatments. INITIAL SCREENING PROCEDURE The Rocky Flats body counter has been described elsewhere.(3) Two 4-in.-dia. by