-~h -~ Cosmic rays, which come fron ovter space, have their rediation effect progressively diluted as they pass through the atmosphere. Thus, a person living at an altitude of about one. mile above sea level receives a dosaage of cosmic rays epprodching couble that of a person who lives at sea level. There are other variations in the natural "background" dosages. For example, people living in certain localities of uranium or thorium mineralization will receive much more radiation than the average, and their ancestors have received these much higher doses over centuries in meny parts of the world. Living in a brick house, rather than in a wooden house, will, with certain kinds of bricks in certain parts of the world, © increase radiation exposure many times over that from test fallout. The additional radiation dosageswhich persons recei ve fron fallout are small cunipared to these naturel dosages and even the variations in the natural dosages. To be specific, the dosage to new bone as in children wnich resulisfrom strontivm-90 at present is about the seme as the additional dosase which a resieent at sca level vould receive From cosnmie rays if be sozed from a beach to the top oY a hill a fcw hundred feet hiszh. There is no question that excessive dosages of redicrctive strontium can céuse bone cancer and leukemia in enimals, so ve shculd not casually dismiss the possi- bility of harmful reenlts from test fallout. However, keeping in mind that populations are exposed to natural r iiations considerably greater than the fallout dosagés, we can attempt to detezaine whether these have caused any cstectable effects. We cen examine, for exemple, whether there is any obvious increase in the rate of occui-rence of - bone cancer and leukemia in populations living at higher altitudes or in regions of uranium mineralization, ete. Rxamination of availsble records does not disclose any such effects. Hovever, vital statistics have act zlvsys ocen cavefully kept, and further studies are being carried on vider the aegis of the United Netions Comnittee to deter- ming vhether eny such effects cen be Cetected. Cre fact is apparent, hevever--it certainly is not our normal experience that people can eppreciably increase the occurrence of these Department of Energy Historian’s Offre ARCHIVES (nore) -