radon

^ Department of Experimental Physics, University College Dublin, Dublin 4, IrelandCase-control studies on lung cancer and radon in dwellings have been conducted in North Americaand Europe, including one study in Lazio region, in Central Italy. Great attention is generally devotedto the reduction in the uncertainty in radon exposure assessment because it can give rise to relevantuncertainty in the estimated risk. One of the main potential sources of uncertainty is the use ofcontemporary radon concentration measurements as estimators of past concentration values.

A first review of the numerous data on the areas in Italy where high radon concentration in dwellingshave been found is presented here. The data were obtained from the national survey and from severallocal surveys carried out in areas where high radon concentration values were expected, on the basis ofthe national survey results or of geological considerations. The analysis is restricted to data obtainedwith long-term measurements.

About two hundred volume traps were retrieved from dwellings in various radon prone areas inEurope. They were analysed for the purpose of retrospective radon assessment. Emphasis is put onspecific problems encountered when using field samples as opposed to laboratory exposed samples. Itwas seen that in very dusty circumstances, direct penetration of radon decay products from the outsideto the centre of the volume traps calls for extra caution. Rinsing the samples is proposed as a solutionand was tested in field and laboratory conditions, showing good results.

One could say that the Spanish Radon Program began in 1988 with the development of a nationalsurvey on indoor radon in Spanish houses. Today, 10 years later, many activitites by differentinstitutions and Universities have been carried out and a good information about the radon problemhas been achieved. Spain consists of 50 provinces which are amalgamated to form 17 autonomousregions. In this paper, we show the results of a major research and development program which is stillin progress.

Several kinds of studies have been carried out concerning building materials.The granitic region can be considered as a significant part of the country. In recent years graniticmaterials are being used as ornements or integrated on the walls inside the houses, producing highindoor radon levels. Studies of different coverings for granitic materials were tested employing incolorpaintings in order to reduce the radon exhalation from such granitic stones, without modifying theirappearance.

This paper presents the experimental results of utilizing a flexible thin-film membrane as a passivebarrier to radon gas diffusion. Nine commercially available membranes of various compositions andthicknesses were evaluated as retardant to radon gas diffusion. The radon gas concentration ratiosacross the thin-film membranes alone and in combination with an adjacent concrete sample (effectivediffusion coefficient) were measured in a laboratory system with state-of-the-art instrumentation.

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.

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.

A large-scale radon survey has been carried out from 1995 to 1998 in southern Greece, in order toestimate the radon concentration in Greek dwellings and the exposure of the Greek population toradon. The design was administratively orientated. The statistical criterion for the selection ofsampling locations and the distribution of radon dosimeters was the percentage of dwellings of eachlevel of the administratively classifications in respect to the above level. This way of distributionassured that all the inhabited geographical regions were covered.