A study of indoor 220Rn and 222Rn decay product concentrations in the UK

In order to gain a better understanding of the risk of human exposure to Rn-220 indoors, measurements of Rn-220 decay products have been performed in a number of houses in England. The study focused mainly on areas where above-average indoor Rn-220 concentrations were to be expected because of geological or other factors. Thoron (Rn-220) in room air comes mainly from the building materials, with an additional contribution from soil gas; therefore, Rn-220 concentrations were examined in relation to building materials as well as location. Measurements were carried out in 23 houses. The mean equilibrium equivalent Rn-220 (EET) concentration found was 0.39 Bq m(-3) and the mean equilibrium equivalent Rn-222 (EER) concentration was 17.8 Bq m(-3). The Rn-220 concentration values and EET/EER ratios found in this investigation correspond well with other published results. Values imply that the Rn-220 concentrations in English dwellings are a far less important problem than Rn-222 concentrations.