A new survey of radioactive radon gas in Irish homes found that radon-reducing measures do not guarantee safe levels, the Radiological Protection Institute of Ireland (RPII) has warned.
It says homeowners should test for radon if they want to be certain of safe levels.
The institute has continued its ongoing radon survey with a study in Kilkenny. This compared older homes without radon-protection measures and newer homes that should have barriers against radon.
Building regulations require all homes built since July 1st, 1998, in high radon areas such as Kilkenny to have a radon-blocking barrier in the foundations.
The study showed, however, that three of 33 new homes which were tested had radon concentrations above the national reference or safety limits set by government. One of them had radon levels almost eight times above the reference limit.
The institute did not know whether the homes found to be above the safety limit conformed with the building regulations by having a radon barrier fitted, said the RPII's director of advisory services Dr Tony Colgan.
"There is no way (to know)without going back and inspecting the homes," he said yesterday after the institute released the new study.
"We also know from the international experience that the barrier won't always ensure homes are under the reference level."
Dr Colgan said the reference level was measured in becquerels (Bq), and all homeowners in the study found to be above the 200Bq safety limit were notified. They had been offered advice on what actions should be taken to reduce the radon to safer limits.
He said a third of the Republic is considered to have high radon levels, and 7 per cent of homes tested in a long series of radon studies were found to be above the 200Bq limit.
For this reason it recommends that all householders in high radon areas should test their homes. The test costs about €45.
The 1998 regulations require a radon-blocking membrane in the foundations and a "sump" or collection space for radon that can easily be cleared using a fan if high radon levels are detected. High radon exposures increase the risk of lung cancer over time.
The survey of 85 homes in Kilkenny is the third comparative study looking at new and old homes. The first two were in Ennis and Tralee.
In Kilkenny, new homes fitted with radon-blocking membranes had radon levels about a third lower than older homes without a membrane. A similar study in Tralee showed that new homes with barriers had radon levels about half that of older homes.
"We found that the barriers do bring down radon levels in these homes," Dr Colgan said.
Three of the 52 older homes surveyed and three of the newer homes in Kilkenny were above the 200Bq reference level. The highest level found in an older home was just over 400Bq. The highest found in a newer home was about 1,550Bq.
The survey also revealed that 42 per cent of homeowners were unaware of the presence or absence of a radon sump under their homes. Some 24 per cent did not know if their home had a radon barrier.