Radon risk mapping in ireland

The work described in this paper is based upon the results of the recently completed National Surveyof Radon in Dwellings [1] carried out by the Radiological Protection Institute of Ireland (RPII).Measurements were carried out in 11,054 dwellings, located in 832 10 km grid squares across thecountry. The main objective of the survey was to identify High Radon Areas throughout the country;a High Radon Area is a grid square in which 10% or more of the houses are predicted to have radonconcentrations in excess of 200 Bq/m3, the national Reference Level.It is generally accepted that the distribution of indoor radon levels in houses follows a log-normaldistribution. Based upon this assumption the percentage of houses exceeding the Reference Level in agrid square, was predicted using the Geometric Mean (GM) and Geometric Standard Deviation (GSD)for the data obtained. An improvement to this prediction can be made by examining the distributionof the radon concentrations measured and applying a corrected log transform to achieve normality.For grid squares in which fewer than five measurements were obtained, a smoothing algorithm basedupon data in neighbouring squares was used to obtain values for the GM and GSD and a predictionmade using these interpolated results.