Some areas within counties Dublin, Meath, Kildare, Wicklow, Wexford, Kilkenny, Cork, Kerry, Limerick, Clare and Galway are a radon gas risk, according to a new assessment.
Radon gas can leave a resident at risk of lung cancer.
Around 280 of the approximately 2,300 lung cancer cases in Ireland per year are related to indoor radon exposure, according to Trinity College Dublin.
A new assessment using 32,000 residential radon measurements throughout Ireland points to specific radon priority areas.
Radon is a naturally occurring radioactive gas, which does not have any taste, odour or colour.
It can only be detected using specialised equipment. Radon escapes from the ground and dissipates to the atmosphere where it is diluted to very low concentrations, or it may accumulate to higher concentrations in enclosed spaces.
Indoor radon levels vary from house to house depending on location, construction type and usage.
Radon is the principal source of ionising radiation exposure, representing over 56pc of the overall dose received by the Irish population, and exposure to radon increases the likelihood of developing lung cancer.
Globally, radon exposure is the second highest cause of lung cancer after smoking.