Lead concentrations (microgram/g wet weight) in human bone (tibia) were measured noninvasively in vivo employing an X-ray fluorescence technique. Forty-five workers who had been subjected to chronic industrial exposure were found to have a mean bone lead content of 52.9 micrograms/g wet weight (0 to 198 micrograms/g). In addition to bone lead content, blood lead, body burden of lead as assessed by urinary lead excretion after EDTA chelation, zinc protoporphyrin, and unstimulated urinary lead excretion were evaluated. The results suggest that the in vivo measurement of tibia lead content may serve as an acceptable indicator of body lead burden and provide a practical technique for lead screening purposes. The correlation coefficient between X-ray fluorescence findings and lead excretion following Ca-EDTA administration is 0.69; p less than 0.001.
This article is a review of the problem of evaluating the radiation hazard from plutonium in occupationally-exposed personnel. Although these people are exposed to plutonium most typically by inhalation, the only experimental kinetic studies conducted with human beings as the subjects involved the intravenous administration of plutonium. Kinetic data from animal studies indicate that when plutonium enters the body by inhalation it tends to be retained in the lungs for prolonged periods of time, being removed from the lungs with a half-time of the order of 300 days. The plutonium in the lungs thus acts as a continuous source of plutonium entering the circulation. It is suggested that the plutonium from the lungs introduces a significant error in those estimations of the plutonium body burden that are calculated from plutonium urinary excretion data using formulas derived from the injection experiments, and which at least tacitly assume that, after an initial period, the urinary plutonium reflects bone and liver plutonium concentrations. The animal studies suggest that it may be feasible to evaluate the lung burden more directly by external counting methods and through the use of plutonium fecal excretion data.The animal plutonium-239 toxicity data are also reassessed in regard to the maximum permissible body burden of plutonium, and no change in the currently accepted value of 0.04 pc Pu239 is considered to be indicated on the basis of the available data.
Methods have been developed for measuring the body content of 197Cs and the thyroid content of 1311 using rather simple, compact equipment. Procedures for calibrating the equipment were designed to provide reproducible results with a variety of counting equipment and environmental conditions. The methods and calibrations were tested by interlaboratory comparison among seven laboratories throughout the U.S. These methods should find application for measuring 137Cs and I3lI in those people who do not have access to an established wholebody counting facility.
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