Dynamic distribution of radioisotopes of cerium, ruthenium and silver in sheep tissues

A number of radioisotopes of cerium, ruthenium and silver may be released into the environment and potentially contaminate foodstuffs. For ruminants, data on the absorption, transfer and excretion rates of these radionuclides are sparse and were previously insufficient to allow the development of reliable dynamic models to enable the prediction of contamination levels in food products. In this study, groups of sheep were given single oral administrations of radiocerium, radioruthenium, and radiosilver and slaughtered at various periods up to 1 year. The resulting data were used to develop compartment models to describe the transfer of the three radionuclides to sheep tissues. Values for gut absorption and transfer to muscle (the most important tissue in terms of contamination of the food chain) derived from the models were considerably lower than previously advised values for the radionuclides studied. For all three radionuclides there were certain organs which contained significantly higher activity concentrations than muscle. The models developed allow prediction of the likely levels of these radionuclides in the tissues of sheep as a result of single or continuous contamination events.