Establishing a regional reference indoor radon level on the basis of radon survey data

The establishment of national reference levels is a new requirement of the ICRP radiological protection system. For protection against indoor radon exposure measures based on a common national reference level tend to be less effective in regions where the probability of high indoor radon concentrations is relatively low in comparison with the national average. Therefore it makes sense to establish individual indoor radon reference levels for large sub-national regions as well as for urban agglomerations separately. Analysis of indoor radon surveys of the territory, taking into account the type of building, year of construction, building material, floor and other factors influencing indoor radon concentration, provides essential and important data for defining the reference level. For Ekaterinburg, Russia it is suggested to set the reference indoor radon concentration to a level of 70 Bq m(-3) which corresponds to the 90th percentile of radon concentration in a representative group of buildings constructed in the period 1970-89, in which the lowest average indoor radon concentration was observed.