253Es, a pure alpha emitter with a half life of 20.5 days, is now available in microgram amounts. The potential for human exposure to it and the lack of published observa-tions on its behavior in animals led us to study its whole-body retention, excretion and organ distribution in mice. Citrated 253Es was injected intramuscularly; half the mice also received DTPA treatment beginning 2 hr after the injection. Daily whole-body counts were obtained by L X-ray counting, and the organ and tissue activities were measured by X-ray and alpha counting at 4 and 14 days. Comparison was made with our earlier Am and Cf study in mice. Einsteinium behaved according to predictions based on its place among the actinides. DTPA therapy was about as effective for Es as for the other actinides. The validity of the L X-ray method for whole-body, organ, tissue and excreta counts, using empirically determined correction factors, was established for the mouse. The method offers simplifications for future studies of this sort.
©1972Health Physics Society