Radon in the same Swedish dwellings in 1976 and in 1990

The aim of the study is to clarify the changes made to the same buildings studied in 1976 and 1990, and their effect on the ventilation rates and indoor radon. This provides a basis for calculation of the uncertainty in the estimation of the exposure to radon in the middle of the 1970s from measurements made today. Measurements of the radon concentration and other parameters have been carried out during 1990 in the same dwellings that were studied in 1976. One conclusion is that it is extremely difficult to compare data sets collected at different times despite the fact that they were carried out by research groups of the same institute. Despite the difficulties, conclusions can be made within each of the three building groups. The overall conclusion is that the radon concentration as an average was similar or had decreased in all the groups of buildings studied. (author)