It is hard to make predictions about the plans of all nations. If we find—and others also find—that clean weapons are the most desirable, the total strontium contamination is not likely to become more than perhaps two to four times the present value. We believe that all reasons—respect for human life, military considerations and simple sanity—lead to one conclusion. In the development of nuclear explosives we must endeavor to make them clean. But the real reason for this does not lie in the small contamination due to tests. The real reason is that war could turn contamination into a danger to countless people. CHAPTER XII Danger to the Individual How much harm is being done by the atomic tests? Some scientists have claimed that from past tests alone about 50,000 persons throughout the world will die prematurely. There is no general agreement on this point. Some think the number should be smaller. It is possible that radioactivity produces some effects which prolong life rather than shorten it. But even if all the biological consequences of radiation were known many questions would still demand answers. Can tests be justified if they actually shorten some human lives? Even the possibility of a health hazard must be taken most seriously. On the other hand: Are there any reasons which make continued testing necessary? We shall return to these questions in a later chapter. First, however, we shall try to put before the reader the known facts about the fallout danger to the individual. We shall try to put this danger into perspective by relating it to other more familiar dangers to which all of us are exposed. In the following chapter we shall discuss how the fallout may affect future generations. The dangers from big doses of radiation are well known. Exposure to a thousand roentgens over our whole body causes almost certain death in less than thirty days. Four or five hundred roentgens give a fifty-fifty chance of survival. At less than a hundred roentgens, there is no danger of immediate death. Three years ago the Marshallese got a dose of 175 roentgens. None died. Apparently all are in good health. Over longer periods of time even bigger radiation doses can be tolerated. A thousand roentgens spread over a lifetime produce no apparent biological consequences in individual cases. A rough rule (which is not too well-established) is that five times as much radiation can be tolerated if one is exposed to only a little radiation at any one time.