More than a quarter of the inhabited areas of the Republic have been designated "high-radon areas" in a survey to be published today.
High levels of radon gas in certain regions have been associated with an increased risk of lung cancer for residents of those areas. Radon is the principal everyday source of radiation exposure.
The Radiological Protection Institute of Ireland (RPII) has surveyed almost 11,000 houses in 830 grids of 10km square. It found that in 234 of the grids (28 per cent of the total), radon levels were above the national reference level of 200 becquerels in 10 per cent of dwellings, enough for the grid to be considered "a high radon area."
In almost one in eight of the grids, more than 20 per cent of dwellings had radon levels about the reference level.
The highest levels were found in the west of Ireland in a line stretching from Co Clare to Co Sligo. The southeast - counties Wicklow, Carlow, Kilkenny, Wexford and Waterford - is also particularly affected. Other pockets of high radon levels are scattered around the State.
The level of radon gas in any area is largely determined by geological factors. Household radon levels can also be affected by features of particular buildings, particularly their foundations.
Because it is a gas, radon can move freely through the soil and is quickly diluted to harmless levels in open air. However, if it enters an enclosed space, such as a house, it can build up to unacceptably high levels.
The institute's chief executive, Dr Tom O'Flaherty, says the problem of radon build-up in dwellings can be tackled relatively easily. He recommends that anyone living in a high-radon area should have the level of radon in their home tested.
The test, which is can be done by the RPII or private commercial firms, costs about £15. Remedying the problem usually costs a few hundred pounds and involves extracting air from the sub-floor level and ventilating it outside.
Dr O'Flaherty says that while the level of data on radon levels in other countries varies, the comparable data available would suggest that high levels of radon gas are particularly prevalent in Ireland. The Devon and Cornwall area of England is also particularly affected by the problem.
A detailed map of radon levels around the State will be available from the institute from tomorrow.
The final phase of the institute's work covered counties Galway and Mayo. The last part of the report identified an area of Co Clare stretching from the Burren to the Shannon Estuary as a high-radon area. Other such areas were identified throughout Limerick and in the south of Tipperary.
The completed National Radon Survey will be given to the Minister of State with special responsibility for Nuclear Safety, Mr Joe Jacob, today. Mr Jacob told the Dail last year that 150 lung cancer deaths in the State every year are linked to radon.
The report will explore the health effects of exposure to radon and will make recommendations on how the problem can be tackled in both new and existing dwellings. Mr Jacob will also launch the institute's website.
