Ionizing radiation in the 20th century and beyond

Ionizing radiation and radioactivity have been subjected to very different evaluations since their discovery in the late 19th century. This is due to their potential effects, which are beneficial in medical diagnosis and treatment as well as in technical applications, and cause damage at high doses. In the light of the early finding that high doses are harmful, some first concepts limiting the exposure to manmade radiation were elaborated in the twenties of the last century. They were based on effects detectable at an early stage, and were lowered step by step as far as dose limits were concerned. The question about possible genetic effects, which was still open in the fifties, and the definition of the linear dose - effect hypothesis, resulted in further decreases of limits. It is doubtful to what extent current levels can be justified and are able to protect the health and lives of people, given the limited financial resources available to protect the public. In connection with the debate about the peaceful uses of nuclear power and the necessary final storage of radioactive waste, possibly in repositories in deep underground geologic formations, attention should be drawn to two natural facts: Natural sources annually release 2 to 5 orders of magnitude more radioactive substances into the atmosphere than all manmade sources taken together. The cumulated activities released by all nuclear power plants worldwide today roughly correspond to the natural activities of approx. 3 km3 of terrestrial rock in some 500 years. Accordingly, the human contribution to the natural flow of radioactivity is rather minimal, especially as it can be controlled and limited. (orig.)