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The risk assessment of indoor radon exposure


In the radon health study organised in Brittany-Vendée by CEA/IPSN, in close collaboration with the University of Brest and INSERM, 270 lung cancer cases matched each with 2 controls have been registrated. The set-up is in complete conformity with that of the Ardennes-Eiffel study. For the moment the study has also been initiated in other parts (Limousin, Auvergne, Languedoc-Roussillon) of France. In the almost completed epidemiological study organised in Cornwall-Devon by ICRF and NRPB, complete information has been obtained for a total of 965 confirmed cases of lung cancer and for about 1400 (hospital as well as community) controls.

It was agreed that case and control enrolment should last up to mid 1995. Measurements in current homes will be completed by the end of 1995. Measurements in past homes will be intensified and are planned to be completed by September 1996.

As different types (open and closed) of radon detectors are used by the radon laboratories of the involved countries, quality control tests in the radon chamber at the university of Gent, as well as side-by-side inter-comparisons in real house conditions were organised at regular intervals.

In a first experiment 5 different type of detectors were exposed under controlled laboratory conditions, followed immediately by a field test under comparable exposure conditions (660 kBq/m{3}h). One type of detector was out of range as compared to the others and was therefore excluded for further use in the study.

In a second experiment, the 4 remaining types of detectors were installed in 5 houses with exposure levels within the range encountered frequently in the study area. Five detectors of each type were exposed in every house for respectively 3 and 6 months. For reasons of multiple control of all influencing effects, an analysis of variance scheme (ANOVA) was conducted. No significant differences were observed between the different types of closed detectors and a small difference of about 15% was observed between the means of open and closed detectors.

The radon levels in all participating houses are rather low. In order to study the validity of the observations over a wide range of exposure levels, the exercise has been extended to some houses within the 200-500 Bq/m{3} exposure range. From the observations made it became clear that, in a pooling on a larger scale, much attention will also have to be paid to the (differences in) response of the different types of radon detectors under epidemiological field conditions. Therefore such a large-scale inter-comparison exercise for epidemiology, was set-up in December 1993. Currently all available results are being analysed.

In all of the studies it is impossible to perform radon measurements in some of the former residences. For assessing missing past exposures, the usefulness of geological information in combination with the details obtained during the interview as to the construction of the dwellings, and/or the information obtained from the measurements of implanted P0-210 activity is being studied. After all, appropriate past exposure determination is a key issue for correct risk estimation.

From the present status of the studies it can be foreseen that by the end of 1996 complete information for the originally planned number of cases and controls will be attained. It is expected that only limited number of data will be available for relatively high exposure levels. In order to obtain a precise estimate about the risk of indoor radon over a wide range of exposure levels, it will be necessary to perform a pooled analysis of different studies. Care needs to be taken as to the compatibility of the data to be pooled. In this field, the experience gained by the Ardennes-Eiffel study group in co-ordinating and pooling of epidemiological data will be of great use.
This project is the continuation of the work in progress under contract nr. B17-0007-C(TT)
The principal objective consists in estimating the risk of indoor radon exposure with sufficient precision by means of the case-control method. As part of this effort the Ardennes-Eifel study was set up. It is a collaborative study between the research groups of the Centre d'Energie Atomique, the Bergische Universitat of Wuppertal, la Division de la Radioprotection du Grand-Duché de Luxembourg, the Imperial Cancer Research Fund and the University of Gent, who is also acting as coordinator. The study areas coincides more or less with a geological zone, covering parts of France, Belgium, Luxemburg and Germany. A common protocol and questionnaire are used in all centers of the 4 participating countries. The field work that started already in all centers in autumn of 1990 will be continued. At least 2/3 of all interviews are planned-to be completed by the end of '93. The final statistical analysis will be performed by the center of the university of Wuppertal. To achieve this, a common coding schedule is being compiled, according to which every country will send every six months the national data, as a standardised ascii-file, to the group of Gent. Here a data-filter will be constructed to transfer all data in an appropriate form to Wuppertal.
In France the same study design is also used in the epidemiological studies about radon in Brittany and the Massif Central. The data of these studies will also be included for final statistical analysis.
In view of pooling with other case-control studies about radon, some Preparation work will already be performed during the next coming two years.
The Cornwall-Devon study with an approach- very similar to that of the Ardennes-Eifel study, is also part of this project.
The principal epidemiological investigators of Sweden, Norway, Finland and Germany will be consulted regularly, in order to prepare the pooling on an European level to the best.
In order to improve the quantification of the health effects of low doses, the ongoing work in the high background areas of Brasil will be continued. Based upon the favourable circumstances (high levels, good collaboration


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