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1999 > Klaus Becker 1999 |
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In many countries of the world, visits to radon-rich springs have been successfully used in the treatment of painful arthritic and rheumatic diseases back into pre-historic times. The positive health effects of radon and its daughter products have been recently verified in Europe by randomized double-blind studies, and in the eleven oficial radon spas of the German speaking countries, 75,000 patients have been treated in 1997 (the well-known "Heilstollen Bad Gastein" charges about 550 $ US for ten hours of inhalation of 165.000 Bqm-3 (1)). In careful, much disputed studies involving essentially the whole residential population in the USA and considering all possible confounding factors, a decrease of lung cancer was observed with increasing residential radon levels (2). Similar effects have been found in China and Canada, but slightly different results in some other countries (3). On the other hand, radon has been frequently called to be the most dangerous environmental health hazard. The US National Research Council just published an official report (3), estimating 15,700 to 23,600 additional annual lung cancer deaths in the USA to be caused by residential radon. This claim is officially supported by several countries in Europe, as well as by ICRP and other international bodies. Consequently, action limits for buildings have been proposed in the 150-600 Bqm -3 region. Amounts in the multi-billion dollar range are being spent on radon monitoring, research, and remediation worldwide (e.g. about 2x109 in former uranium mining areas in Saxony/Germany since 1990) related to assumed radon hazards (5), thus creating a profitable "radon industry". Such developments not only raise the question whether more funds should be devoted to get higher or lower radon exposures, but it is also an interesting test for the validity of the LNT hypothesis, as well as closely related concepts such as Collective Dose, and regulations based on these assumptions. The observation of a high incidence of a lung disease among silver miners in the Ore Mountains of Southern Saxony dates back about 460 y. This disease was identified as lung cancer 120 y ago, and in 1913 first related to the extremely high radon levels in these mines. Even in homes in this area, up to 115,000 Bqm -3 have been measured, and 12 % of all homes exceed 15,000 Bqm-3 . In the mines, from which 220,000 tons of uranium have been extracted for the Soviet weapons program between 1945 and 1990, radon exposures of the miners sometimes exceeded 500 WLM, corresponding to 2 mill. Bqm-3 (or 5 Sv/y according to ICRP). Such exposures, in combination with high dust and toxic mineral inhalation, diesel exhaust fumes, nitrous gases, and heavy smoking among the miners, caused thousands of additional lung cancers during the early postwar years. Similar observations in Czechoslovakia and other countries have later been used for a linear extrapolation from miner data to residential conditions. The multiplication of low concentrations with large population numbers resulted in the frightening estimates mentioned above. This procedure is, however, highly questionable. Comparing, for example, test groups of non-smoking women in high-radon areas with those in low-radon areas of Saxony, one finds substantially less, instead of more, lung cancers in the high radon areas (4). Even in the highest (> 500 Bqm -3) group, no increase over the lowest (< 100) group could be detected. This has been confirmed by further, more detailed studies (5), indicating a reduction also of leukernia in high background areas. There is supporting evidence for such findings, e.g. recent results from Hungary (6); and for the effect of external low-LET radiation (X and g) on human lung cancer induction (7). Experiments on single alpha particle effects in cells (8) also lead to the conclusion that a linear dose-response relation is not plausible. New theoretical explanations for such results are available (9). The current situation may be summarized as follows:
References.
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The
Seventh International Conference on Nuclear Engineering April 21, 1999 |
RSH > Documents > Tokyo 1999 >
Klaus Becker 1999
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