A convenient, low-cost, time-integrating monitor based on the track-etching technique wasdeveloped for measuring the deposition rate of attached 220Rn progeny indoors. Simultaneousmeasurements for deposition rates and concentrations of 220Rn progeny were performed in 13 housesduring 12 months. Various values were observed among those houses, but seasonal variations werenot clearly observed. The deposition velocity of attached 220Rn progeny was estimated to be(0.53?0.11)?10-2 cm?s-1, in fair agreement with most of the values of attached 222Rn progeny indwellings in the literature.

The purpose of this contribution is to situate the radon issue within the whole field of radiationprotection. There is among health physicists a fairly general consensus that exposure to radon decayproducts constitutes the largest and most variable contribution to the population exposure. It istherefore ironical that precisely this exposure is the subject of constant disputes with regard to thevalidity of the risk estimates and to the desirability of inciting the population living in radon proneareas to take action.

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.

The International Commission on Radiological Protection (ICRP) and The Council of the European Union has recommended the Member States to take action against radon in homes and at workplaces. In the ERRICCA project the Group on Legal and Building Code Impact was designated to study the current radon legislation and to give advice on future conduct of laws and recommendations. On behalf of the Group a questionnaire on radon-legislation have been send out to all European States and a selection of non-European States.

A simple intercomparison of natural radioactivity and radon emanation factor measurementscoordinated by the Medical Physics Department of the University of Cantabria UC, Spain, has beencarried out during 1998 in the framework of the EU Concerted Action ERRICCA (European Researchinto Radon in Construction Concerted Actio). All the measurements have been made on a "blueconcrete" sample friendly delivered by Dr. G.

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.

The effect of indoor gamma dose rate, permeability of soil, substructure, and ventilation habits of inhabitants were studied using data of 84 low rise residential houses collected in an area of enhanced indoor radon concentration. The radon concentrations varied from 30 to more than 5000 Bqm-3. Cross-tabulation, comparisons of means and multiplicative models were used to test the significance of the effects. In this study a quite high percentage of explained variation R2 - 68% - was found. It was found that the most important factors were the substructure and the permeability of the soil.

In Kinsarvik, Norway, extraordinary high radon levels in dwelling units are revealed. The bedrock geology was expected to give the answer to why the levels are so high. However, the uranium or radium content is not especially high123. Thus, we believe the explanation to the high radon consentration to be related to the unconsolidated sediments4.

A survey has been made of the radiation exposure of inhabitants in a small new housing estate in theNetherlands, where 101 houses are built at about the same time, but according to nine differentdesigns. The objective of this study was to determine which dwelling characteristics affect the indoorradon concentrations and the absorbed dose in air. Both components were examined separately for aperiod of one year in the crawl space, the living room and a first-floor bedroom, using passive tracketchedand thermoluminescence detectors, respectively.