Using geogenic radon potential to assess designation of radon priority areas in Ireland

Radon is a radioactive gas which emanates from rock, soil and water. Radon concentrations in theatmosphere are generally very low (typically <5 Bq m-3), however it can occur at much higher levelsin soil (typically 10's-100's kBq m-3), or enclosed spaces such as buildings and caves (typically 10's-100's Bq m-3). Exposure to radon and its daughter products is associated with an elevated risk ofdeveloping lung cancer. Ireland has a population weighted indoor radon concentration of 98 Bq m-3resulting in an estimated 300 annual lung cancer cases per year, representing approximately 12% ofthe annual lung cancer cases. A national-scale legislative radon-risk map has a 10 x 10 km spatialresolution and is based exclusively on indoor radon measurements (i.e. it does not contain anygeological information). The legislative map satisfies the European Council Directive2013/59/EURATOM Basic Safety Standard, in that it defines "high radon" areas as those where >10%of homes are estimated to exceed the national reference level of 200 Bq m-3. New buildings in suchareas are legally required to have a barrier, with low radon permeability installed.This research focuses on a karstic region of SE Ireland, which features some exceptionally highindoor radon concentrations (65,000 Bq m-3), even though it is not classified as a "high radon" areaon the national legislative map. Here we demonstrate the use of measuring sub-soil radonconcentrations and sub-soil permeability, in order to construct a radon potential (RP) map of thearea. Extremely high sub-soil radon concentrations (>1443 kBqm-3) and radon potential values(>200) are spatially associated with Namurian shales, interbedded with limestone. Overall, weclassify the study area as high radon potential (RP >35) using this technique. We suggest all areasunderlain by Namurian shales in Ireland should undergo similar radon potential mapping, and ifnecessary, should be re-designated as "high radon" areas. If deemed appropriate (i.e. where RP>35), such a designation will help to protect the general public from the harmful effects of indoorradon exposure, and will help to lower the incidence of radon-related lung cancer in these areas.