Page Last modified 28 Jun 2022
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Indoor radon in buildings is a major cause of lung cancer in Europe, a risk enhanced by exposure to air pollution and tobacco smoke. Although radon comes into the buildings from natural sources, that doesn't make it any less hazardous. Exposure to indoor radon can and should be reduced through well tested technical and policy solutions.

Radon and cancer

As radon[1] forms naturally by radioactive decay inside minerals, part of it escapes into the atmosphere and indoor air, where it becomes a potential hazard to the occupants, exposed mainly through inhalation (Joint Research Centre, 2019). Radon and its decay products are known carcinogens, causing, or contributing to, lung cancer, a risk enhanced by exposure to air pollution and smoking. Although cancer risks from radon are limited to exposure to relatively high and sustained indoor concentrations, radon is one of the leading causes of lung cancer (Ruano-Ravina et al., 2017). 1.2-1.9% of all cancer cases, and 1 in 10 lung cancer cases in Europe may be due to indoor radon exposure (Darby et al., 2005; Brown et al., 2018; IARC, 2018; Couespel and Price, 2020). According to Global Burden of Disease study data, around 19,000 lung cancer deaths in Europe in 2019 may have been due to naturally occurring indoor residential radon (Murray et al., 2020). The risk of lung cancer increases in non-smokers by about 11-16% for exposure to every additional 100Bq/m3 (a measure of exposure to radiation) increase in long-term average indoor radon concentration (Ruano-Ravina et al., 2017; WHO, 2021b). While the association of radon with other types of cancer has been studied, the evidence is still inconclusive.

Although radon comes from natural sources, exposure can be reduced in existing and new buildings, and radon prevention should be considered at the design stage in radon-prone areas. WHO (2021b) lists technical solutions that can significantly reduce radon levels in existing buildings, such as increasing under-floor ventilation, installing a radon sump system, preventing radon passing from the basement into living spaces, sealing floors and walls, and improving ventilation. Recommended policy solutions include providing information on radon levels and health risks, establishing radon concentration reference levels, including radon prevention in building codes, radon measurement testing protocols and programmes, education on and subsidies for radon reduction measures, and including radon as a risk factor in national strategies related to cancer control, tobacco control, indoor air quality and energy conservation.

Trends in exposure to radon in Europe

The spatial distribution of indoor radon concentrations across Europe reflects the underlying geology, with high indoor concentrations found in granitic zones and areas with certain types of rock. Climatic and some anthropogenic factors also contribute to indoor radon concentrations, but their spatial distribution is still unclear (Joint Research Centre, 2019). Radon concentrations also increase with depth, which contributes to high levels of occupational exposure in some types of mining activities and higher radon concentrations in ground and lower floors in dwellings (Kropat et al., 2014). There are no robust data on trends in indoor radon concentrations over time, although some studies suggest that improvements in insulation in dwellings may in fact have led to an increase in radon levels, with older buildings having lower indoor radon concentrations (Ringer, 2014; Baeza et al., 2018; Florică et al., 2020). Specifically, energy efficiency-oriented retrofitting, such as replacing old windows with energy-efficient double-glazed ones, insulating walls and ceilings, or replacing old doors with better-sealing ones, may reduce ventilation and increase buildings’ airtightness, thus increasing indoor concentrations in radon-prone areas (WHO Europe, 2009; Pampuri et al., 2018; Symonds et al., 2019).

What the EU is doing about radon

The Basic Safety Standards Directive (EU, 2013) introduced for the first time legally binding requirements on protection from exposure to natural radiation sources and mandated all EU Member States to establish national radon action plans, define reference levels for indoor radon concentrations in dwellings and workplaces, and identify and delineate radon priority areas. Europe’s Beating Cancer Plan supports Member States in implementing the requirements on protection from ionising radiation, particularly radon, which causes a substantial number of lung cancers. One of the 12 messages of the European Code against Cancer calls upon citizens to “Find out if you are exposed to radiation from naturally high radon levels in your home. Take action to reduce high radon levels.”


[1]For the purposes of this report, ‘radon’ encompasses 222Rn and its progeny.


Baeza, A., et al., 2018, ‘Influence of architectural style on indoor radon concentration in a radon prone area: a case study’,Science of the Total Environment.

Brown, K. F., et al., 2018, ‘The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015’,British Journal of Cancer118(8), pp. 1130-1141 (DOI: 10.1038/s41416-018-0029-6).

Couespel, N. and Price, R., 2020,Strengthening Europe in the fight against cancer, European Parliament, Policy Department of Life Policies (

Darby, S., et al., 2005, ‘Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies’,BMJ330(7485), p. 223 (DOI: 10.1136/bmj.38308.477650.63).

EU, 2013, Council Directive 2013/59/Euratom of 5 December 2013 laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation, and repealing Directives 89/618/Euratom, 90/641/Euratom, 96/29/Euratom, 97/43/Euratom and 2003/122/Euratom (OJ L 13, 17.1.2014, p. 1-73).

Florică, S., et al., 2020, ‘The path from geology to indoor radon’,Environmental Geochemistry and Health42(9), pp. 2655-2665 (DOI: 10.1007/s10653-019-00496-z).

IARC, 2018,Les cancers attribuables au mode de vie et à l’environnement en France métropolitaine, International Agency for Research on Cancer (

Joint Research Centre, 2019,European atlas of natural radiation, Publications Office of the European Union, Luxembourg.

Kropat, G., et al., 2014, ‘Major influencing factors of indoor radon concentrations in Switzerland’,Journal of Environmental Radioactivity129, pp. 7-22 (DOI: 10.1016/j.jenvrad.2013.11.010).

Murray, C. J. L., et al., 2020, ‘Global burden of 87 risk factors in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019’,The Lancet396(10258), pp. 1223-1249 (DOI: 10.1016/S0140-6736(20)30752-2).

Pampuri, L., et al., 2018, ‘Effects of buildings’ refurbishment on indoor air quality. Results of a wide survey on radon concentrations before and after energy retrofit interventions’,Sustainable Cities and Society42, pp. 100-106 (DOI: 10.1016/j.scs.2018.07.007).

Ringer, W., 2014, ‘Monitoring trends in civil engineering and their effect on indoor radon’,Radiation Protection Dosimetry160(1-3), pp. 38-42 (DOI: 10.1093/rpd/ncu107).

Ruano-Ravina, A., et al., 2017, ‘Action levels for indoor radon: different risks for the same lung carcinogen?’,European Respiratory Journal50(5) (DOI: 10.1183/13993003.01609-2017).

Symonds, P., et al., 2019, ‘Home energy efficiency and radon: an observational study’,Indoor Air29(5), pp. 854-864 (DOI: 10.1111/ina.12575).

WHO, 2021b, ‘Radon and health’, World Health Organization (

WHO Europe, 2009,Radon levels in dwellings, Fact Sheet 4.6, World Health Organization Regional Office for Europe (

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Filed under: radiations, cancer, radon
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