34 of radiation exposure. The inhalation of 10 curies might produce recognizable symptoms of exposure but would have a very small probability of being fatal. One could select a number of radionuclides of which a curte might be taken into the body under conditions which would not be lethal. One_ may also select radionuclides of which the intake of a curie under credible . circumstances would be fatal. However, nature of the damage to the body and the length of time that might elapse before death occurs could vary greatly from one such radionuclide’ to another. Familiar radionuclides of greater than average hazard are strontium 90, barium 140, cesium 137, radium 226, thorium 230 and plutonium 239. Question 5B . Apparently less than a eurie of strontium-90 would be lethal. ’ less? Half a curie? vf of a curie? 1/100th? ' Answer 5B: , Row much ) The answer to this for man is undetermined since man is not used for - such experimental investigations. There have been many studies in which rodents and larger animals have been given various amounts of strontium-90 either by feeding or injection, in single or multiple doses. Some of these studies have been reviewed by McClellan and Jones (2°sr Induced Neoplasis: A Selective Review, in Delayed Effects of Bone-Seeking Radionuclides, edited by Mays, Jee and Lloyd, University of Utah Press, Salt Lake City, Utah, 1969). At. the ‘University of California - Davis, beagle dogs have been fed various levels of strontium-90 for long periods of time. At a level of 12 yCi/day for 1-1/2 years, which gives an average skeletal dose of 6.0 rads/day, no significant