Indoor radon levels in buildings in the autonomous community of Extremadura (Spain)

Indoor air samples taken in buildings throughout the provinces of Caceres and Badajoz in the Autonomous Community of Extremadura, Spain, were analysed for airborne radon concentrations using charcoal canisters. Measurements were made during the years 1998-2000. The geometrical mean indoor concentration was 90 Bq m(-3). An estimated annual effective dose of 1.6 mSv y(-1) was calculated for residents, assuming an equilibrium factor of 0.4 and an occupancy factor of 0.8. The relative importance of the principal variables that condition radon concentrations inside buildings was also delimited experimentally. These were: soil type, construction materials used, the height of the room above ground level, and the degree of ventilation. The temporal evolution of the radon concentration was analysed, as this aspect could be particularly important in a Continental-Mediterranean climate such as that of the two provinces of the study.