An overview of Radon Surveys in Europe

G. Dubois
Radioactivity Environmental Monitoring
Emissions and Health Unit

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Preface

With the aim of preparing a European atlas of natural radiation, the Institute for Environment and Sustainability (IES) of the Directorate General Joint Research Centre (JRC) of the European Commission (EC) has conducted a European survey to assess the means and methods used by national authorities to describe radon levels in their countries.

Radon is a naturally radioactive gas that is, by far, the main contributor to the exposure received by the population from natural background radiation. It is also considered to be the main leading cause of lung cancer second to smoking, and most European countries have therefore adopted a number of regulations and made large efforts to identify radon-prone areas. Because indoor radon levels can fluctuate largely over short scale, establishing radon risk maps can become very difficult. It is the purpose of this report to explore the variety of the means and methods used in the European countries to measure and report radon levels.

By presenting the radon maps derived by the various authorities, this report should also help make its readers aware that part of their environment is also naturally radioactive.

Acknowledgements

This report was only possible thanks to the excellent collaboration of all the national authorities and contact persons whose names are indicated in the report. Our deepest gratitude also goes to the many researchers who provided useful advice, explanations, hints, addresses and references.

We would also like to thank our colleagues from the REM group and DGTREN for their helpful suggestions.

Introduction

Radioactivity is everywhere in our environment and can thus be detected in the water we drink, in the food we ingest, in the air we breathe. Ionising radiation can have artificial or natural origins, and its relative contribution to the total dose we receive on the average per year is summarised in Table 1 [1]. By far, natural radiation is the main contributor to the total dose since less than 10% of the radiation we receive is man-made, from which 98% come from medical activities (diagnostics and therapy) (Figure 1).

In most circumstances, the naturally radioactive gas called radon (Rn222 isotope with a half-life of 3.8 days) is the major contributor to the total dose. This gas is produced by the radioactive decay of uranium which is an element that is naturally present in the earth’s crust. Radon transports radioactivity mainly by diffusion mechanisms through the ground, and its concentration in our environment thus depends mainly on geological factors, soil texture, soil water content, and the pressure difference between the gas in the soil and at the surface. Relatively heavier than air, radon shows low concentrations outdoor but tends to be trapped in basements and the lower floors of buildings. For the same reasons, it is often found at high concentrations in mining galleries.

Because radon is considered to be the main contributor to lung cancer second to smoking, the European Commission constantly makes efforts to inform the public about this natural hazard. Recent studies [2] have shown that radon in homes causes about 20,000 lung cancer deaths in the European Union (EU) each year. This is about 9% of the total lung cancer deaths in the EU and about 2% of cancer deaths overall.

Table 1. Worldwide average annual effective doses at year 2000 from natural and man-made sources of radiation in millisievert (mSv) [1].

Source of radiation Dose (mSv) %
Natural background (total, all sources) 2.4 46.07
Inhalation (mainly radon) 1.2 23.04
Terrestrial gamma rays 0.5 9.60
Cosmic rays 0.4 7.68
Ingestion 0.3 5.76
Medical diagnostics 0.4 7.68
Atmospheric nuclear testing 0.005 0.10
Chernobyl accident 0.002 0.04
Nuclear power production 0.002 0.04
Total doses / year 5.209 100.00

RadonFig1

Figure 1. Pie chart showing the relative doses from natural and man-made sources of radiation. Derived from table 1 [1].

Exposure to radon in dwellings is also the subject of Commission Recommendation of 21 February 1990 on the protection of the public against indoor exposure to radon (90/143/Euratom) [3]. Indoor radon concentration levels of 200 and 400 Becquerel per cubic metre (Bq/m3) are the reference concentrations above which mitigation measures should be taken in new and old buildings, respectively, to reduce exposure to radon. This can be done simply by improving the ventilation of the basements and/or by reducing the permeability of the foundations of the house to the gas.

To further identify regions that are susceptible to high radon levels, most European countries have organized large sampling campaigns, mainly by performing indoor and soil-gas measurements.

National radon surveys

To assess efforts made by European countries in identifying regions with increased radon levels, the JRC sent a questionnaire to national authorities, universities and research centres in the 25 Member States of the European Union, as well as Bulgaria, Romania, Croatia, Turkey, Norway, Switzerland, FYROM and Serbia-Montenegro. Addressed were the authorities that deal with ionizing radiations and the universities and research centres that have contributed to national radon surveys.

Except for Albania, Bosnia-Herzegovina and Bulgaria, all the countries that were contacted replied to the questionnaire. Each one of them has carried out radon surveys (see Table 2). As a consequence, the JRC could prepare short reports for these countries (see the Annex to this report).

For Albania the JRC found some relevant information in the scientific literature. At the time of printing this report, Turkey was finishing the analysis of its survey, and the JRC expects to publish these results in a later version of this report.

Outdoor radon concentrations are known to be low (the mean annual concentration is on the order of 10 Bq/m3) and to have no major impact on health. Hence, all countries have concentrated their efforts on monitoring radon in dwellings or in soil-gas. The last approach is used to delineate radon-prone areas on the basis of physical, rather than mainly statistical and geographical, criteria (see Table 2).

Sampling strategies

Measurements are usually made on the ground floor of houses and buildings as radon is around nine times heavier than air. To assess doses received by inhabitants, measurements are usually made in bedrooms and living rooms. One can estimate the number of dwellings that have been investigated in Europe to between 1.5 and 2 million. The number of measurements can be multiplied by 2 since most surveys monitored several rooms in the same habitation.

Measurements of radon in soils, called soil-gas measurements, are made in all countries but systematically only in a few. These measurements are mainly used for identifying radon-prone areas. Given the large diversity in design and construction materials used to build houses, indoor measurements are usually made in addition to assess directly the exposure of the population in these areas.

Even if the countries have adopted various sampling strategies (systematic, preferential or random) and targeted various types of buildings (e.g. public places, hospitals, schools, multifamily and/or single family houses), one can consider that, overall, most radon-prone areas have been identified and delineated throughout Europe, with a lower resolution in the Balkans.

Measurement techniques

Measurements have been made using various types of detectors and for different time intervals. Most countries that have frequently organised very large monitoring campaigns used so-called alpha-track detectors as these are small enough to be sent by mail. These are then left in the main living area of the dwelling for a minimum of three months (winter time is usually preferred because exposure is highest due to lesser ventilation) but generally for a whole year.

Other measurements involving air pumps have also been made in a few countries, but these methods can run for a few days only and require the intervention of specialized personnel.

As a result of this variety in measurement techniques and sampling time (ranging from a few hours to more than a year), direct comparison between estimated levels measured in the different countries should be made with caution.

Table 2. National sampling efforts for monitoring radon.

Country Population (x 106) Number of dwellings monitored Soil-gas campaign?
Albania 3.6 110 NA
Austria 8.2 16 000 60
Belgium 10.4 9 000 NA
Croatia 4.5 782 38
Cyprus 0.8 84 NA
Czech Republic 10.2 150 000 9 000
Denmark 5.4 3 120 NA
Estonia 1.3 515 566
Finland 5.2 73 074 400
France 60.7 12 261 230
FYROM 2.0 NA NA
Germany 82.4 > 50 000 4 019
Greece 10.7 1 277 NA
Hungary 10.0 15 602 NA
Ireland 4.0 11 319 NA
Italy 58.1 5 361 NA
Latvia 2.3 300 NA
Lithuania 3.6 400 70
Luxembourg 0.5 2 619 NA
Malta 0.4 90 NA
Netherlands 16.4 1 846 475
Norway 4.6 51 925 NA
Poland 38.6 4 098 210
Portugal 10.6 3 317 NA
Romania 22.33 567 NA
Serbia-Montenegro* 10.8 968 NA
Slovakia 5.4 4 019 NA
Slovenia 2.0 2 512 NA
Spain 40.3 5 600 NA
Sweden 9.0 500 000 > 2000
Switzerland 7.5 55 000 NA
United Kingdom 60.4 450 000 NA

* Province of Vojvodina only
NA = Not Available.

Delineating and reporting radon levels

Most countries have used the European recommendation [3] on the annual mean indoor concentrations that should not be exceeded, that is 400 Bq/m3 in existing buildings and 200 Bq/m3 for new constructions, as reference for defining radon risk maps. As recommended by the UK, the criterion for identifying radon areas is frequently considered to be those where the number of dwellings with concentrations higher than 200 Bq/m3 exceeds 1%.

Because radon-prone areas are sampled more than others, overall statistics are usually biased and not always meaningful. Hence, the summary information regarding average levels found in Europe are estimations based on statistics and or models and, here again, one should be careful when using the information summarized in Table 3.

Most national reports present their results in the form of a radon maps. Although this is obviously a powerful mean to delineate areas that are prone to radon, the mapping of radon levels is a task that is very difficult: radon levels between neighbouring houses can vary by a few orders or magnitude depending on the construction material used, the insulation used in the house and the living habits of the inhabitants. Because mapping usually involves some averaging step of the data collected, thus hiding a few areas that present higher levels, it is not a surprise to see that almost all countries adopted different mapping techniques and strategies.

Table 3. Some statistics for European radon surveys.

Country Estimated annual mean levels (Bq/m3) % dwellings > 200 Bq/m3and 3 % dwellings > 400 Bq/m3
Albania NA NA NA
Austria 97 8 4
Belgium 48 1.7 0.3
Croatia 68 5.4 1.8
Cyprus 19 0 0
Czech Republic 140 10 – 15 2 – 3
Denmark 53 2.7 0.2
Estonia 60 2 – 2.5 0.3 – 0.5
Finland 120 8.7 3.6
France 63 6.5 2
FYROM NA NA NA
Germany 50 2.5 < 1
Greece 55 2 1.1
Hungary NA 5.1 0.8
Ireland 89 6 1.5
Italy 70 3.2 0.9
Latvia NA NA NA
Lithuania 55 2.5 0.3
Luxembourg 115 NA 3
Malta 40 0 0
Netherlands 23 0.3 0
Norway 89 6 3
Poland 49 1.6 0.4
Portugal NA NA NA
Romania 45 NA NA
Serbia-Montenegro* 144 18 4
Slovakia 108 14 11
Slovenia 87 5.5 2
Spain 90 4 2
Sweden 108 6 – 7 3 – 4
Switzerland 77 10 7
United Kingdom 20 0.4 0.1

* Province of Vojvodina only
NA: Not Available

To better illustrate these differences, a mosaic has been made from the national radon maps published in this report (see cover and Figure 2).

One will realise that a majority of the countries has adopted administrative boundaries to define local mean values while others have used a grid as a reference system to define these values. A few have used interpolation techniques, including advanced geostatistical techniques.

RadonFig2
Figure 2. Mosaic of published European radon maps.

European maps of radon levels

The survey presented here could highlight large differences between the radon surveys. So far, no attempts have been made to harmonize data and maps at the continental level. As a consequence of these differences, it is difficult to compare maps and data between European countries. The Institute for Environment and Sustainability (IES) of the Joint Research Centre, in collaboration with the Directorate General for Transport and Energy (DG TREN) of the EC are exploring possibilities to harmonise such information with a view to obtain a better picture of the regions that are present elevated levels of radon. This should not only help everyone concerned, citizens and decision-makers alike, to assess better this natural threat to our health, but also to familiarize the population with the fact that their environment is naturally radioactive. More support and information from the European Commission regarding these issues can be found on the internet [4, 5].

Summary

With the aim of preparing a European atlas of natural radiation, the Institute for Environment and Sustainability (IES) of the Directorate General Joint Research Centre (JRC) of the European Commission (EC) has conducted a European survey to assess the means and methods used by national authorities to describe radon levels in their countries.

Radon is a naturally radioactive gas that is, by far, the main contributor to the exposure received by the population from natural background radiation. It is also considered to be the main leading cause of lung cancer second to smoking, and most European countries have therefore adopted a number of regulations and made large efforts to identify radon-prone areas. Because indoor radon levels can fluctuate largely over short scale, establishing radon risk maps can become very difficult. It is the purpose of this report to present the variety of the means and methods used in the European countries to measure and report radon levels.

References

[1] M Charles (2001). UNSCEAR Report 2000: Sources and Effects of Ionizing Radiation. Journal of Radiological Protection, 21(1): 83-85.

[2] S Darby, D Hill, A Auvinen, J M Barros-Dios, H Baysson, F Bochicchio, H Deo, R Falk, F Forastiere, M Hakama, I Heid, L Kreienbrock, M Kreuzer, F Lagarde, I Mäkeläinen, C Muirhead, W Oberaigner, G Pershagen, A Ruano-Ravina, E Ruosteenoja, A Schaffrath Rosario, M Tirmarche, L Tomásek, E Whitley, H-E Wichmann and R Doll. Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies.
BMJ 2005;330:223-, doi:10.1136/bmj.38308.477650.63.

[3] Commission Recommendation of 21 February 1990 on the protection of the public against indoor exposure to radon (90/143/Euratom).
Official Journal of the European Union, OJ L-80 of 27/03/90, page 26.

[4] RadonNET. The objective of this network is to help radon stakeholders to communicate, share knowledge, identify problems and propose solutions to the various issues that arise.

[5] European Forum on Radon Mapping. This web site provides support to a European Forum for discussing methods for mapping radon levels.


An overview of Radon Surveys in Europe
The full report, including ANNEX 1, detailing the from all European countries can be found here.

Below are the deta for the United Kingdom

United Kingdom, indoor measurements

Contact point for indoor radon measurements:
Health Protection Agency (HPA)
Chilton, Didcot, Oxfordshire
OX11 0RQ
United Kingdom

Reporting contact point
Jon MILES
Health Protection Agency (HPA)
Chilton, Didcot, Oxfordshire
OX11 0RQ
United Kingdom

Tel.: (+44) 1235 822797
Fax.: (+44) 1235 833891
e-mail: Jon.Miles@hpa-rp.org.uk

Web address of related project.

Selected References:

  • Wrixon, A. D., Green, B. M. R., Lomas, P. R, Miles, J. C. H., Cliff, K. D., Francis, E. A., Driscoll, C. M. H., James, A. C., and O’Riordan, M. C. (1988). Natural radiation exposure in UK dwellings. NRPB R-190.
  • Miles, J. C. H., Green, B. M. R. and Lomas, P. R. (1993). Radon Affected Areas: Scotland and Northern Ireland. Doc. NRPB, 4, No. 6.
  • Miles, J. C. H (1998). Mapping radon-prone areas by lognormal modelling of house radon data. Health Physics, 74: 370-378.
  • Miles, J. C. H (1998). Development of maps of radon-prone areas using radon measurements in houses. Journal of Hazardous Materials, 61:53-58.
  • Green, B. M. R., Lomas, P. R., Miles, J. C. H., Ledgerwood, F. K. and Bell, D. M. (1999) Radon in dwellings in Northern Ireland: Atlas and 1999 review. NRPB-R308.
  • Green, B. M. R., Miles, J. C. H., Bradley, E. J., and Rees, D. M. (2002). Radon Atlas of England and Wales. Chilton, NRPB-W26.
  • Miles, J. C. H. and Appleton, J. D. (2005). Mapping variation in radon potential both between and within geological units. Journal of Radiological Protection, 25: 257-276.

Campaigns

Survey period Dwellings investigated Integrated measurements / dwelling
1980-2005 450 000 2.1

Sampling strategy:

The dwellings investigated have been chosen in different ways at different times: randomly on the whole territory, on a regular grid covering the whole territory and preferentially in regions with expected higher levels. The great majority were made for the purpose of identifying houses above the radon action level (400 Bq/m3 at working place, 200 Bq/m3 at home), so were made in the highest radon areas.

Measurement technique

Detector type Measurements time (days) Season Measurement location
Track-etch detectors (NRPB/HPA, NET, Gammadata) 90-365 all living room and bedroom
Detector type Measurement time (units in days)
Mean Std. Dev. Min. Max.
Track-etch detectors (NRPB/HPA, NET, Gammadata) 107 35 30 550

Statistics of the measurements

Measurements statistics (units in Bq/m3)
Measurements Mean Geo. Mean Std. Dev. Min. Max.
945 000 87 46 148 0 17 000
Estimated mean annual radon levels in British dwellings
Mean (Bq/m3) % of dwellings above 200 Bq/m3 and below 400 Bq/m3 % of dwellings above 400 Bq/m3
20 0.4 0.1

Maps:

Maps were generated using local averages on a predefined grid. The cell size of the grid is 5 km by 5 km but areas with higher measurement density are mapped with a resolution of 1 km. Minimum number of measurements/cells: 5 for 5 km grid square mapping, 30 measurements within 5 km for 1 km mapping.

RadonMap1
Map of radon affected areas in England and Wales. Map reproduced with the kind courtesy of J. Miles © (2005).

RadonMap2
Map of radon affected areas in Northern Ireland. Map reproduced with the kind courtesy of J. Miles © (2005).

RadonMap3
Map of radon affected areas in parts of Scotland. Map reproduced with the kind courtesy of J. Miles © (2005)

EUR 21892 EN – An overview of radon surveys in Europe

Author: G. Dubois
Luxembourg: Office for Official Publications of the European Communities
2005 – 168 pp. – 21.0 x 29.7 cm
Scientific and Technical Research Series
ISBN 92-79-01066-2