The first Norwegian study of historic radon concentrations in 17 dwellings in the high radon areas inNorway has been conducted as part of an international field intercomparison during 1998. Theinvestigation is part of SINI (an acronym for Sweden, Italy, Norway and Ireland) internationalcollaboration on retrospective radon measurements in several European countries having differentclimates and living conditions.

Ventilation systems are known to influence radon concentrations indoors considerably. However, the initial results of the largest radon survey in 3660 Norwegian kindergartens conducted during heating seasons from 1996 to 1998 showed marginal effect of such systems. Clarification of this surprising result required a more detailed secondary investigation in a smaller group of kindergartens with balanced ventilation systems operating under special ventilation regime.

The results of field investigations of natural radiation exposures of the general populations in twostable rural communities in Yugoslavia are presented. The principal emphasis was on exposures tocontemporary indoor radon but measurements of external penetrating radiation absorbed dose rates inair were carried out in the majority of cases. In addition in a limited number of dwellings,measurements of thoron gas concentrations were made.

Exposure to high concentrations of radon (222Rn) progeny produces lung cancer in both undergroundminers and experimentally exposed laboratory animals. The goal of the study was to determinewhether or not residential radon exposure exhibits a statistically significant association with lungcancer in a state with high residential radon concentrations.A population-based, case-control epidemiologic study was conducted examining the relationshipbetween residential radon gas exposure and lung cancer in Iowa females who occupied their currenthome for at least 20 years.

The use of contemporary radon (222Rn) gas concentrations to estimate retrospective radon-relateddoses can introduce substantial uncertainties in epidemiological analyses. These uncertainties tend tobias the results of radon-lung cancer epidemiologic studies towards the null. Temporal variability ofradon progeny over past decades and the variability in the dose effectiveness of airborne radonprogeny caused by indoor atmospheric differences are among the main sources of uncertainties in ourregion.

Different aspects of the geogenic radon potential in a coal mining area in south-western Germany arediscussed. Due to the rather low specific radium activities of rocks and soils varying between 10 and70 Bq/kg a low geogenic radon potential can be expected. Radon concentrations in soil gas inabandoned mining areas are characterized by a lognormal distribution with a median value of 20kBq/m3. In the neighboring area with deep mining generally younger than two years, radon contentsincrease up to a median value of 38 kBq/m3.

The radium distribution of the soil is one important parameter governing radon emanation. The present study’s main objective is to investigate radium distribution in different Swedish soils, using chemical selective sequential extraction, and to compare t

The aim of this study is to develop a new technique for reducing high radon level in indoor air bymethod of membrane permeation using a hollow fiber module. The experiment has been carried outfor MERASILOX-S module of fine hollow fibers of silicon rubber that has high permeability constantand MHF hollow fiber module made of thin segment polyurethane membrane. The radon permeabilityconstants of hollow fiber membranes have been estimated from the decrease rate of radonconcentration in a radon permeation system.

In order to characterise the behaviour of radon decay products under domestic conditions, long-termmeasurements were carried out from May 1997 to April 1998 in a typical dwelling located in Brittany(France). In particular, the unattached fraction and equilibrium factor were continuously measured.Moreover, the size distributions of unattached and attached radon daughters were investigated byusing specific instruments implemented in the laboratory. All these experiments were carried outunder different typical aerosol conditions.

High radon concentration in work and living places are caused by a high geological radon potentialof the soil , by technological processes, the use of building materials with high uranium, thoriumand radium content and the building construction. Further the influence of the working and living conditions on the dose estimation is very important. Especially the equilibrium factor and the unattached fraction are influenced by the working and living conditions.