The European map of indoor radon concentrations: status and questions of quality assurance

As a first part of the long-term project "European Atlas of Natural Radiation", a European map of indoor radon concentrations is currently under development. By mid-2011, 21 countries participate in the project, yielding a more or less complete coverage of the European territory. In this article we shortly present the current status before concentrating on questions of quality assurance. Such questions inevitably emerge in a project which attempts to integrate and harmonize large amounts of data of methodically different origin; aggregating them into a common map raises by itself questions of statistical significance.