~ ~5- 3 4 dvead diseases by moving to a higher altitude or by moving from a sedimentary soil, where the uranium content is low, to an igncous or granitic surface, where the uranium content is very much higher, or by inoving from a wooden to a brick or concrete house. Another way of evaluating the possible risk from strontium--90 in fallout is throvgh comparison with the permissible concentration of strontiun-90 recommended by authoritative groupse The pernissible amount of strontiun90 for atonic energy workers in the United States is about 2,000 times the present strontiun-90 content of new bone jn the United States resulting from fallout. (Strontium-90 concentrations in the rest of the world are generally lower than these in the United States -) Authoritative groups have recommended that, on grounds of general prudence, the per- missible limit for whole populations be one--tenth of that for atomic energy workers. On this basis, the present level for new bone, that is, in children, in the United States is sonevhat less than one percent of the maximun permissible oncentrvation for the pepulaticn. Perheps a word of explenztion shovld be given regarding these maximum permissible concentrations. As you know, Scientists do not speek of “cisks™ or "hazards" in the scase that the words ordinarily are sed. They try to ineQ— sure possibilities almost to the limits of the finite therefore, risktt includes the possibility of eeffects far beyoid the range of *he provable or detectable. The maximum permissible concent: :tions ére not safety limits, rather, they indicate thet et considerably larger concentrations, perhaps tenfold greater, @nere vould be definitely detectable effects 50 far, I have been discussing principally the possible risks from radicactive strontium. Radicactive fall- aut Snelvudes other materials ihich do not accumulate inside the Vedy, (.1t do emit penetrating rediation which can Irvadiete the sex organs and othce parts of the whole body fiom che outside. Such radiations can produce genetic mutations. feain, in evalvsting the possibility of genetic effects from Fallout, we shovld try to compare it with normal Se. psricnce. VYhe extcrnal dosages from fallout, that is, these (.:ore)