Uranium in the form of uranyl nitrate hexahydrate was administered in drinking water to Sprague-Dawley rats for periods of 28 and 91 d and New Zealand White rabbits for 91 d. The animals consumed food and water ad libitum. Subgroups of rabbits were followed for recovery periods of up to 91 d; 24-h collections of urine and feces were performed for some of the rabbits at various times during the exposure and recovery periods. At the end of the experiment, all animals were sacrificed and femur and kidney samples were analyzed for uranium residues. The results show that both rats and rabbits absorb about 0.06% of ingested uranium in the gastrointestinal (GI) tract. The distribution and retention of uranium in the skeleton and kidneys of rats are comparable to parameters reported for humans. The retention half-time in rabbit bone is substantially longer than for humans. The implications of extrapolating from animal data to effects on humans are discussed.

This paper describes a program of laboratory and field studies undertaken to assess the health impact of radioactive debris from the re-entry of the Soviety nuclear-powered satellite, Cosmos 954, on 24 January 1978. It was estimated that about one-quarter of the reactor core descended over Canada's Northwest Territories in the form of submillimetre particles. The other three-quarters apparently remained as fine dust in the upper atmosphere. Each particle contained megabecquerel quantities of the fission products 95Zr, 95Nb, 103Ru, 106Ru, 141Ce and 144Ce, as well as traces of other fission and activation products. Laboratory tests indicated that these radionuclides would not dissolve significantly in drinking water supplies or in dilute acids. Contamination of air, drinking water, soil and food supplies was not detected. The dose equivalent to the GI tract for an individual who might have inhaled or ingested a particle could have been as high as 140 mSv.