Radon risk mapping - a method of predicting problem areas on geological grounds

The Swedish stipulations of a maximum radon daughter level of 200 Bq.m-3 for permanently inhabited buildings, and of 70 Bq.m-3 for buildings built later than 1981, has created a need to evaluate the radon risk caused by the ground. Radon risk mapping is done both on a regional scale and a detailed scale. When mapping, the ground is classified into high, normal and low risk areas. The classification work is started by an interpretation of all available geological material from the investigated area. This is followed by field investigations including radon measurements in possible risk areas, and control of radium content by gamma spectrometry in the typical rock types of the area. Results from MRM Konsult's radon measurements show a very large increase of high radon houses within high risk areas, classified according to the above model, if compared to randomly distributed measurements. (author)