The beevier particles fall. out af the radicactive cloud at early tisce after a detonation, while theiy redicsactivity is still kigh., Therefore, the highest levels of radioactivity oceur over a lecal aren downwind frou the scint of detonation. Ths aren of significant fallcat is expected to oceur entirely Within the uninhabited danger erea surrounding the Saiwetok Proving Ground. As the radioactive cloud is transported avay from the point of detonation, 16 ia widely dispersed by air currenta end diluted ty normal air. ts ratioactivity alec decreases rapidly becsuse of the uoruel provese of radic- active downy.” By the tine the cloud frou « detonation in the Eaivetok Prow ing Groat nee traveled acrose a vast expense of ceeen, 1% wili have become thoroughly dispersed into the air and vill have lost most cf its original radiscactivity. As a vemalt, the exposures to radioactivity in tae United States fras “the Balwetok tests are expected to ba low. Although levels of many time the normal background may be reached in some iscalitios, these increases viil he temporary end will cot arestily insrease the total exposure te radiaticn. Average exposures of residents of the United States to radiation frou veapone Sests during the past five years hee been mich less than the average exposure te rediation from naturel sources during the same period. aT Herta Cehiiae agneiee ants cane at Pretioactive fallout consists of « wixtare of redtotectopes, vith varying baif-lives. The mixture e@ «© whole decreapes in redicectivity in sich a way that for every seven folé increase in sae, the total redicectivity ie decreased Wi-folad. Thus, the refloactivity at seven hours after the XH 1 hour ta only one-tenth that at B+ 1 hour, end in 49 hours te one-tmadredth, ete. (more) ovate