Preliminary Observations on Metabolism and Toxicity of Plutonium in Miniature Swine

Abstract

Miniature swine are being utilized in a series of continuing studies to determine: (a) the blood concentration, organ burden, and excretion pattern following various routes of plutonium administration; (b) the toxicity of plutonium as compared to some other boneseeking nuclides; and (c) the effects in and movement or removal from skin when plutonium is injected or topically applied. Some of the results of these continuing studies are summarized. (1) The distribution and excretion pattern of plutonium seemed dependent on the route of administration when given intravenously, intragastrically, or intratracheally. The form of the plutonium may have contributed to differences, because the Pu²³⁹ nitrate solution used for intravenous administration was buffered with citrate at pH 5–6. (2) Analysis of tissues 450–700 days post-injection (independent of the mode of administration) revealed a greater concentration of plutonium in liver than in bone in every case. The liver: bone concentration ratio appeared to be highest following intravenous administration and lowest following intratracheal administration. (3) Fifty to 77 per cent of the intravenously administered dose was recovered from the liver and skeleton 480–690 days post-injection. By contrast, only about 0.0005 per cent was recovered from the liver and skeleton combined at 580–700 days after intragastric administration and 0.0025 per cent from the same tissues at 580–700 days after intratracheal administration. These latter values are subject to considerable error, however, due to the very low body burdens of plutonium and subsequent difficulty in analysis. (4) Frequent blood sampling in three animals administered plutonium intratracheally showed detectable plutonium in the blood within 15 min. Peak concentrations were reached 4–11 hr post-injection, at which time about 0.06 per cent of the administered dose was in the blood. (5) About 85–98 per cent of the intratracheally administered dose was detected in the feces within 4 days post-injection. (6) A 40 per cent reduction in neutrophile count was observed 6 months after 1-year-old female swine were intravenously injected with 1.3 µc Pu²³⁹/kg of body weight. (7) Early skeletal changes in males injected with 1.3 µc Pu²³⁹/kg of body weight were limited to a slight thickening of the cortical bone, outgrowths of cortical bone into the medullary canal, loss of definitive medullary canal, and increased trabeculation in the spongiosa. The skeletal changes were most severe in the animals injected at 6 weeks of age. (8) Very preliminary data from skin studies suggests that: (a) an effective decontamination method for topically applied plutonium is the application of a plastic adherent and its subsequent removal by peeling; (b) tourniquets applied soon after incurring penetrating wounds may aid in restricting translocation of plutonium from contaminated sites; and (c) suction cups applied to plutonium-contaminated puncture wounds are ineffective in the removal of contamination.