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Public health, environmental and social determinants of health About us News and events Health topics Publications WHO calls for tighter standards on indoor radon The World Health Organization has called on countries to either establish or to strengthen existing programmes to control the presence of radon in homes and other residential settings. Radon is a naturally occurring radioactive gas that has been classified as a human carcinogen, and can lead to an increased risk of lung cancer. A new WHO Handbook on Indoor Radon: A Public Health Perspective published today, indicates that radon exposure is a major and growing public health threat in homes and recommends that countries adopt reference levels of the gas of 100 Bq/m3 (Becquerel per cubic metre). If this level cannot be implemented under the prevailing country-specific conditions, WHO recommends that the reference level should not exceed 300 Bq/m3. “Radon is the second most important cause of lung cancer after smoking in many countries,” notes Dr Maria Neira, Director of WHO's Public Health and Environment Department. “Most of radon-induced lung cancers occur from low and medium dose exposures in people’s homes. Strengthened action by policy makers, and by construction and building professionals can substantially lower the health impact by preventing and reducing radon exposure.” While radon is found outdoors as well, the levels are very low due to dilution in the air. Radon levels are higher indoors, and much higher radon concentrations can be found in places such as mines, caves and water treatment facilities. The lower concentrations - found, for example, in normal buildings and to which large populations are exposed – also confer health risks. For most people, by far the greatest exposure to radon comes in the home. The concentration of radon in a home depends on the amount of radon-producing uranium in the underlying rocks and soils, the routes available for its passage into the home and the rate of exchange between indoor and outdoor air. Radon gas enters houses through openings such as cracks at concrete floor-wall junctions, gaps in the floor, small pores in hollow-block walls, and through sumps and drains. Consequently, radon levels are usually higher in basements, cellars or other structural areas in contact with soil. While the lung cancer risks of high dose radon, typically found among uranium miners for example, have been known for many years, new studies in Europe, North America and China - summarized in the new WHO handbook - have confirmed that low and medium level exposures to radon in homes contributes substantially to the occurrence of lung cancers world-wide. Recent estimates of the proportion of such lung cancers range from 3 to 14%. Lung cancer risk rises 16% per 100 Bq/m3 increase in radon exposure. Studies show that radon is the primary cause of lung cancer among people who have never smoked. However, the absolute numbers of radon-induced lung cancers are much larger in people who smoke, or who have smoked in the past, due to a strong combined effect of smoking and radon. “Key actions needed to achieve radon concentrations at or below the recommended reference level of 100 Bq/m3 include establishing and strengthening radon measurement and mitigation programmes and developing building codes that require radon prevention measures in homes under construction,” notes Dr Neira. “Countries are encouraged to use the handbook to initiate national radon programmes or to promote their existing programmes. “ Radon levels in indoor air can be lowered in a number of ways very effectively and with relatively inexpensive techniques such as sealing cracks in floors and walls to increasing the ventilation rate of the building. These techniques have been developed to reduce radon in both new and existing buildings. Other techniques are described in the Handbook. The WHO handbook is the first comprehensive international compilation of information and recommendations on radon and its public health effects. It includes the latest evidence on health risks, measurements, mitigation and prevention techniques and their cost effectiveness as well as information on radon risk communication. Additionally, specific recommendations are presented for national radon programmes. The International Radon Project (WHO-IRP), producers of the WHO handbook on indoor radon, has involved over 100 experts from more than 30 countries. For more information contact: Ms Nada OSSEIRAN Communications Officer, Public Health & Environment Department, World Health Organization Tel: +4122 7914475 E-mail: osseirann@who.int Ms Sari SETIOGI Media Relations Officer, Health Security and Environment Tel: + 41 22 791 3576 Mobile +41 79 701 9467 E-mail: Setiogis@who.int Related links WHO Handbook on Indoor Radon: A Public Health Perspective WHO Radon Webpage Public Health and Environment What we do Countries Frequently asked questions Procurement Regions