URANIUM IN THE DIET - RISK ASSESSMENT OF ITS NEPHROTOXICITY AND RADIOTOXICITY

The natural occurrence of compounds of uranium (U), a radioactive heavy metal, in food and drinking water is summarized. The results of U determinations of community well waters and table mineral waters in Switzerland, frequently contributing to a considerable increase of the daily U intake, are presented. The toxicological data are reviewed and a no observable effect level (NOEL) of 1 mgU/kg bodyweight/day based on a dog feeding study concerning nephrotoxic effects is proposed. The comparison between the NOEL and the actual daily U intake reveals a substantial margin of safety with respect to chemical toxicity. Concerning radiotoxicity an U intake of 40-mu-g (1 Bq)/person/day, maximum estimated dietary intake in Switzerland, results in a fatal cancer lifetime risk in the order of 10(-4). Criteria for the evaluation of cancer risks and their applicability in the regulation of naturally occurring radionuclides in food and water are discussed and compared with those criteria commonly used in food toxicology for the evaluation of chemical carcinogens.