Radioanalytical techniques for in vivo measurements of trace elements

During the last 20 years, non-invasive in vivo techniques have been developed for the determination of the concentration of various toxic elements in different organs. Photon induced X-ray emission (XRF) and neutron activation analysis (NAA) are the two methods, which have acquired the most widespread interest for in vivo elemental analysis. Our research has mainly been focused on the development of new XRF techniques for the determination of lead, cadmium and mercury. Lead: We have now used the XRF technique for determination of lead in finger-bone for almost 20 years. We still use two Co-57 sources for excitation and a GE-detector for registration. The elimination of lead from the skeleton, as studied for almost 20 years in a group of retired lead workers, can be described by a biological half-time of 16 years. The result shows the slow turnover of lead in bone, also indicating that bone lead may constitute a significant endogenous source. Cadmium: The XRF technique for in vivo measurements of cadmium in the human kidney cortex and liver has been significantly improved and the detection limit using a partly plane polarised X-ray beam for excitation and a Si(Li) detector for detection is now about 10 ug/g at a normal kidney depth of 50 mm. This allows measurement on the general population. The effective dose is significantly lower or comparable to the NAA method, even for deeply situated kidneys. The XRF-technique has been applied on groups of non-occupationally as well as occupationally exposed persons. Mercury: Using a similar technique as for cadmium it is now possible to determine the mercury concentration in kidneys of occupationally exposed workers down to levels of around 25 ug/g. In a group of 20 occupationally exposed persons and 12 referents, mercury levels were above the detection limit in nine of the exposed persons, but in none of the referents. levels up to 54 micro g/g were observed. 1 tab., 3 figs., 38 refs. (author)