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