3c Assessment of human exposure to natural radionuclides by using in vivo measurements

摘要

Geologically, Finland is part of the Fennoscandian shield and the bedrock consists mainly of granitoids. The average concentrations of natural radionuclides in granitoids, especially in granites, are high. Consequently, exceptionally high concentrations of natural uranium (~(234, 235, 238)U) and the daughter nuclides of uranium and thorium series (~(222)Rn, ~(226, 228)Ra, ~(210)Po, ~(210)Pb) have been found in wells drilled in bedrock. The concentrations of natural radionuclides both in drinking water and indoor air have been observed to vary markedly in Finland depending on the location. The highest concentrations have been measured in the granite areas of Southern Finland. Exposure to natural radionuclides in drinking water is usually chronic and may persist for many years before it is recognised. It is normally difficult to assess individual cumulative exposures of afflicted persons with biokinetic models because of several problems: activity concentrations in water may show great temporal variations, assumptions on individual water consumption rates have to be made and many biokinetic parameters are uncertain. Due to these difficulties with biokinetic models it would be useful to have a biological indicator in the human body itself. This would provide more direct information on the cumulative exposure. The objective of this study is to demonstrate the feasibility of estimating individuals' cumulative exposure to uranium and ~(210)Pb by measuring the amounts of these nuclides in their skeletons.