High natural radioactivity of bored wells as a radiation hygienic problem in Finland

The high levels of natural radioactivity of ground water in some regions of Finland were detected some years ago. From the point of view of radiation exposure, the bored wells of private homes play a major role. Levels up to 1,2 μCi/l 222Rn and 256 pCi/l 226Ra have been found. The highest radiological risk is the radon liberated to air in connection of cooking, washing of dishes and clothes, bathing etc. In the measurements performed until now, the highest daily average concentration in air, to which the housewife was exposed, was 112 pCi/l, the highest concentration found in normal living conditions being 595 pCi/l (bathroom during washing of clothes). Measurements of radon levels in homes with high concentration of radon in water are going on with a view to determine the ratio of average radon concentrations in room air and household water. Chromosome analyses are performed in some cases when high cumulative radon exposure is suspected. Results gathered until the time of the final writing of the paper will be given. Risk estimates and need for remedial action are disc