Indoor radon levels and dose estimation in two major Spanish cities

Indoor radon levels obtained exposing 337 passive dosemeters over two periods of 3 months, in Madrid and Barcelona, the two major cities in Spain, are presented. Taking advantage of this survey, a larger one is now in progress. The radon concentration annual averages are 68.5 Bq.m-3 for Madrid and Barcelona, respectively. Seasonal variations in the range of 40-60% were found. Only 3.2% of the values were above 200 Bq.m-3. The importance of the ground as a source of indoor radon is confirmed by lower concentrations in the upper floors. Furthermore, dwellings in Madrid located over arkosic soil show, in general, higher values. In accordance with the usual parameters from UNSCEAR, annual effective doses calculated for Madrid and Barcelona are 1.9 mSv and 1.1 mSv, respectively. Gamma doses have been evaluated in some dwellings in the Madrid and Barcelona area using a TLD environmental monitoring system. A mean value of 150 nGy.h-1 has been estimated. (author)