An office in Co Cork has been identified as having the second highest radon reading ever detected in Ireland.
The Radiological Protection Institute said the level of the radioactive gas present at The Corkman newspaper in Mallow was 60 times higher than the acceptable limit.
Radon is the second biggest cause of lung cancer in Ireland, causing up to 200 deaths per year.
It is a colourless, odourless, tasteless gas which occurs naturally from the decay of radioactive uranium in rocks and soils. It only becomes a problem when it builds up in basements of houses and offices.
The institute said levels at one office of The Corkman newspaper in Mallow would be equivalent to receiving 39 chest X-rays per day, or nearly 10,000 in a working year.
However, the RPII said the office in question was largely unoccupied, and so the risk to employees was significantly reduced.
The RPII's Chief Executive, Dr Ann McGarry, said over 100,000 homes and offices are estimated to be at risk and while the Corkman took the appropriate action, many others were being irresponsible for not testing for radon.