• Indoor radon comes from ground soils or building materials and accumulates mainly in indoor atmosphere where we pass 90% of our lives.
• Epidemiological and experimental studies show that radon is a lung cancer carcinogen. An indoor exposure to 100 Bq/m3 during around 30 years can increase the probability of dying of a lung cancer by 16%.
• Based on estimates of indoor radon exposure of the European population, experts estimate that lifetime exposure to the indoor radon levels in Europe (mean of 59 Bq.m-3) is responsible of 9% of all lung cancer deaths.
• Since action to lower levels in buildings is possible and it is one of the main public health environmental problems, it is important that national authorities engage actions against radon based on solid scientific evidence. HIA applied to different action scenarios is one important tool to assure a sound public health policy.
• Unfortunately there is insufficient epidemiologic information to estimate the relationship between health risks and radon exposure during childhood. Consequently, HIA of childhood exposure is currently not available to support actions to reduce radon in buildings intended for children.
• It is therefore important to do further research on childhood exposure to radon in dwellings and schools and its health impacts during lifetime.

Figure 1. Estimated national annual arithmetic mean of dwelling radon levels

Source : Dubois G.(2005) An Overview of Radon Surveys in Europe. EUR 21892 EN, EC. 168p

Table 1: Health effects associated with exposure to indoor radon (support of evidence) (1)

Radon is an important public health problem. Everybody is exposed to radon in dwellings during his or her entire life.

Radon and lung cancer

Epidemiological studies on miners’ cohorts and case-control studies in general populations provide strong evidence of lung cancer carcinogenicity of dwelling exposure to radon. Furthermore they allow a reliable exposure-response estimate. Applying the exposure-response relation to lifetime exposure in Europe (mean exposure of 59 Bq/m3) allows estimating that about 9% of lung cancer deaths in Europe are attributable to exposure to radon in dwellings.

Radon and leukaemia

There is some evidence based on dosimetry suggesting that there could be a relationship between leukaemia and exposure to radon. However, no epidemiological reliable findings plead for the existence of this relationship. Even though some ecological studies suggest a possible relationship between the risk of leukaemia during childhood and exposure to radon during childhood, there is no strong evidence for the causality of such a correlation. Up to now results of the case-control studies don’t suggest such a relationship.

Children exposure-response functions

Assessing the impact of indoor radon exposure during childhood raises an important methodological problem. What exposure-response relationship should be used? There is a lack of available data to assess the health impact attributable to indoor radon exposure during childhood. Data on young miners (teenagers) exposed to radon in mines in China don’t stress any different relation of what has been observed during adulthood exposure. But there are no epidemiological studies that checked any potential relation between exposure during childhood and risk of lung cancer.Furthermore, to be really relevant, a risk assessment should take into account the variability and the evolution of future exposure to tobacco. Indeed, this factor interacts with radon and is a very strong determinant of lung cancer.

Conclusions

For reasons expressed above HIA on exposure to radon during childhood was considered not feasible for the time being.More epidemiological studies are necessary to assess the issue of childhood radon exposure effects (leukaemia during childhood or lung cancer during adulthood). Applying the BEIRVI exposure response functions to children´s exposure at school in a cost–effectiveness study, the Quebec Public Health institute retained the action on radon in schools and buildings for children as one of the most cost-effective, not without methodological difficulties.There is a need for expert review on the specific topic of extrapolation of exposure response functions from adult exposure to children exposure. We strongly stress the need for a specific focus on the health effects of childhood exposure by the expert committees such as the International Radon Project coordinated by the WHO Geneva http://www.who.int/ionizing_radiation/env/radon/en/index.html, or the European Community research project ALPHARISK.

General: http://www.who.int/ionizing_radiation/env/radon/en/index.html.

Radon and Leukemia

Evrard AS, Hemon D, Billon S, Laurier D, Jougla E, Tirmarche M, Clavel J. Childhood leukemia incidence and exposure to indoor radon, terrestrial and cosmic gamma radiation.

Health Phys. 2006 Jun;90(6):569-79.

Evrard AS, Hemon D, Billon S, Laurier D, Jougla E, Tirmarche M, Clavel J. Ecological association between indoor radon concentration and childhood leukaemia incidence in France, 1990-1998. Eur J Cancer Prev. 2005 Apr;14(2):147-57.

Laurier D, Valenty M, Tirmarche M. Radon exposure and the risk of leukemia: a review of epidemiological studies. Health Phys. 2001 Sep;81(3):272-88. Review.

Radon and lung cancer

National Research Concil. Health Effects of Exposure to Radon: BEIR VI. 1999.

Darby S, Hill D, Auvinen A, Barros-Dios JM, Baysson H, Bochicchio F, Deo H, Falk R, Forastiere F, Hakama M, Heid I, Kreienbrock L, Kreuzer M, Lagarde F, Makelainen I, Muirhead C, Oberaigner W, Pershagen G, Ruano-Ravina A, Ruosteenoja E, Rosario AS, Tirmarche M, Tomasek L, Whitley E, Wichmann HE, Doll R. Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies. BMJ. 2005

Dessau JC, Gagnon F, Lévesque B, Prévost C, Leclerc J-M, Belles-Isles JC. 2005. Le radon au Québec - Évaluation du risque à la santé et analyse critique des stratégies d’intervention. INSPQ, 118 p. + annexes.

Radon exposure data (Source JRC)

Report of the United Nations Scientific Committee on the Effects of Atomic Radiation. New York, United Nations, 2000 Sources and Effects of Ionizing Radiation. UNSCEAR 2000 Report to the General Assembly, with Scientific Annexes. Vol I: Sources. New York: United Nations, 2000. (http://daccessdds.un.org/doc/UNDOC/GEN/N00/587/20/IMG/N0058720.pdf?OpenElement, accessed 4 April 2007).

Dubois G. An overview of radon surveys in Europe. Luxembourg, Office for Official Publications of the European Communities, 2005 (EUR 21892 EN).

WHO ENHIS factsheet indicator: exposure to radon in European countries: ”Radon levels in dwellings”. http://www.enhis.org/object_document/o4723n27388.html.

Authors: Philippe Pirard, InVS.

Reviewers: Hajo Zeeb (IMBEI), Olivier Catelinois (InVS), Alejandro Ramirez (ISCIII), Elena Boldo (ISCIII), Sylvia Medina (InVS).

Long paper available on request, please e-mail to info@ecehbonn.euro.who.int

HIA guidelines on radon (.pdf)