ae Fr oe ttneler nee ee tevin ween . . ee ee gree In 1957, studies were undertaken on uptake by the body and retention after dtrect inhalation of plutonium in the radtoactive cloud after detonation as well as after inhalation of plutonium resuspended by wind action following its deposition on the ground (Stannard, 19733). Rats and dogs were exposed durirg passage of the radioactive cloud, while dogs, sheep and burros were exposed for a long post-event period of up to 160 days at several down-wind locations. The results indicated that dogs exposed to the cloud passage at the time of detonation had higher plutonium burdens than animals exposed to resuspended plutonium for long periods of time, even though the animals exposed to the passing cloud were not exposed to the highest airborne concentrations at ground level. Because of concern about plutonium in the environment from atomic weapons . and, Tater, the nuclear fuel cycle, considerable information has been published on its radioecology (Olafson and Larson, 1962; Stannard, 1973a; Healy, 1975; IAEA, 1976; Friedman, 1976; Hanson, 1980). Plutonium has a low solubility in water and biological fluids and tends to Se noreetile in soils and other media. Hence, plutonium is much Jess likely to move through food chains to man than fission products discussed heretofore. Nonetheless, plutonium in the environment continues to be a timely topic, in view of its role in the end of the nuclear fuel cycle. Metabolic Pathways Because plutonium played a major role in atomic weaponry, considerable re- search on its metabolism and toxicology took place in the 1940s. Studies in rats on the distribution and excretion of plutonfum in various chenical states were made following intravenous (Carritt et al., 1947) or intramuscular