Sodium in man and the assessment of radiation dose after criticality accidents

Recent observations on the sodium content of the human body, both total and exchangeable, using isotope dilution methods and activation of sodium by whole-body irradiation with neutrons in the course of clinical research, suggest that ICRP Reference Man is a misleading guide to the sodium content of the body and of the skeleton and its parts. They also show that reasonable predictions of body sodium content can be made from body weight, height and age, or even from body weight alone. Mean sodium in the average man is about 1.04 g per kg and in the average women about 0.98 g per kg in British and N. American populations. Within each sex mean tissue concentration is inversely related to body weight. Review of the dosimetry for the criticality accident at Y-12 Oak Ridge shows that dose estimates should be increased by about 10% because whole blood values of 24Na were relied on instead of plasma values. Taking account of body build reduces the range of dose amongst the four most heavily irradiated subjects. The absorbed doses reported for the subjects exposed at the criticality accident at Vinca, Yugoslavia, need to be increased by about 30% because the normal sodium content of the body was grossly overestimated. The more severe clinical picture at Vinca than at Y-12 is now more easily understood in terms of differences in dose. These changes are solely the result of improved information about sodium in the body. Other uncertainties in the dosimetry at Y-12 and Vinca are unaltered.