Radiation doses from radon in buildings.

Not until about 1970 was it possible to estimate the magnitude of the correlation between additional lung cancer frequency and radon daughter exposure in miners. In addition, it has been realised that high levels of radon daughters in homes may be found in all countries and therefore the interest in radon in buildings has rapidly increased during the last 10 years. Radon gas enters the house from underground, from building materials and in some cases from tap water. Indoor radon daughter concentrations vary between countries and regions. The absorbed dose in the basal cells of the bronchial epithelium based on an average of the population in Canada, U.S.A. and West Germany can be estimated to be about 1 mGy a-1 (average radon daughter concentration about 25 Bq m-3) for Great Britain about half of that value and for the Nordic countries about double this value. 300-3000 lung cancer cases (most probable 1100) may occur in the future in the Swedish population of 8.4 million from radon daughter exposure indoors today. This estimation is made by the National Institute of Radiation Protection. A lower estimate of 100-1000 lung cancer cases is made by the Swedish Cancer Committee. Efforts to decrease the exposure from radon daughters indoors have been made in some countries by establishing limits or recommendations for the radon or radon daughter concentration indoors. Measuring methods for finding houses with high radon daughter concentrations and effective building techniques in order to decrease the radon daughter concentrations in both existing and for planned buildings are available.