I am aware of the report published in July this year by the Radiological Protection Institute of Ireland, RPII, which represents the results of a national survey of indoor radon concentration levels in domestic dwellings carried out by the institute between 1992 and 1999.
Radon is a naturally occurring radioactive gas found in variable amounts in rocks and soil. When it surfaces in the open air, it is quickly diluted. However, where it enters an enclosed space, such as a house, it can reach unacceptably high concentration levels. There is evidence to suggest that long-term exposure to high levels of radon can be a contributory factor in increasing the risk of lung cancer. The RPII's survey involved measuring radon concentrations in over 11,000 houses nationwide. The survey was geographically based, using the 10km grid squares of the Irish national grid as the unit area.
The results of the survey were used by the RPII to predict the percentage of houses in each grid square with radon in excess of 200 becquerels per cubic metre of air. In 1990, the Government on the advice of the then Nuclear Energy Board, adopted an annual radon concentration of 200 becquerels per cubic metre as the national reference level above which remedial action to reduce indoor radon concentration level in domestic dwellings should be considered by the householder. This advice is consistent with EU and internationally accepted guidelines. Based on the results of the survey, the RPII estimated that just over 91,000 houses nationwide or some 7% of the national housing stock have indoor radon levels in excess of the national reference level. The RPII also used the results of the survey to designate as "high radon areas" areas where the predicted percentage of dwellings with radon levels above the national reference level is 10% or more.