Retention half times in the skeleton of plutonium and 90Sr from above-ground nuclear tests: A retrospective study of the Swiss population

Abstract

Plutonium and 90Sr are considered to be among the most radiotoxic nuclides produced by the nuclear fission process. In spite of numerous studies on mammals and humans there is still no general agreement on the retention half time of both radionuclides in the skeleton in the general population. Here we determined plutonium and 90Sr in human vertebrae in individuals deceased between 1960 and 2004 in Switzerland. Plutonium was measured by sensitive SF-ICP-MS techniques and 90Sr by radiometric methods. We compared our results to the ones obtained for other environmental compartments to reveal the retention half time of NBT fallout 239Pu and 90Sr in trabecular bones of the Swiss population. Results show that plutonium has a retention half time of 40 ± 14 years. In contrast 90Sr has a shorter retention half time of 13.5 ± 1.0 years. Moreover 90Sr retention half time in vertebrae is shown to be linked to the retention half time in food and other environmental compartments. These findings demonstrate that the renewal of the vertebrae through calcium homeostatic control is faster for 90Sr excretion than for plutonium excretion. The precise determination of the retention half time of plutonium in the skeleton will improve the biokinetic model of plutonium metabolism in humans.