Excretion kinetics of ingested uranium

Monitoring of occupational incorporation of uranium is normally based on measurements of urinary excretion. To predict uptake, and hence dose and risk, from excretion measurements, the assumed biokinetic model must reliably describe the excretion pattern. In the present study, urinary uranium excretion patterns in healthy subjects were investigated after defined intake regimes of environmental uranium. In 3 healthy male subjects a total of 6 investigations on dietary urinary excretion of uranium were performed. None of them had a history of previous occupational exposure to uranium. For a period of 1 resp. 3 weeks, the subjects had an additional daily uranium intake of approximately 20 μg from consumption of mineral water. The total investigation period was 5 resp. 7 weeks. Uranium excretion in urine was measured by high resolution ICP-MS (Inductively Coupled Plasma - Mass Spectrometry). The results of these investigations demonstrate that the current excretion model for uranium (ICRP Publication No. 78) does not predict the excretion pattern of ingested uranium correctly and may therefore be substantially misleading. Modifying the excretion parameters for a better fit to the experimental data results in increased radiation doses; by a factor of approx. 4 for the kidneys and by a factor of 2 for the effective dose. (orig.)