Investigations on the retrospective estimation of radon exposure in homes had already been carried outin international collaboration in the uranium mining regions of Germany since 1994. Following aConcerted Action named "Retrospectively Estimated Radon in Areas Affected by Uranium MiningActivities " was agreed upon.
The first Norwegian study of historic radon concentrations in 17 dwellings in the high radon areas inNorway has been conducted as part of an international field intercomparison during 1998. Theinvestigation is part of SINI (an acronym for Sweden, Italy, Norway and Ireland) internationalcollaboration on retrospective radon measurements in several European countries having differentclimates and living conditions.