Radon gas emissions contain radioactive particles which disperse naturally outdoors, but can build up in indoor environments. Most of the radon we breathe is exhaled immediately, but some of the particles can attach themselves to the lungs, exposing them to damaging levels of radiation.
Researchers analysed 7,148 cases of lung cancer and 14,208 controls (people who had not developed lung cancer) across Europe. In the largest study of its kind, they examined radon levels in the present and past homes of all the lung cancer sufferers and the controls. They also obtained detailed smoking histories, including the effects of second-hand smoke on lifelong non-smokers.
They found that radon accounted for 20,000 deaths from lung cancer in Europe each year, equating to 9% of lung cancer deaths and 2% of all cancer deaths across Europe. The risk of radon-induced lung cancer increased proportionally to how much radon people were exposed to.
Smokers were at much greater risk of developing lung cancer, as radon exposure multiplied the effects of smoking.
Concentrations of radon in homes vary widely from house to house, and urban areas tend to have lower levels than rural areas. Action can however be taken to reduce radon exposure in the home, say the authors. At moderate cost increasing underfloor ventilation would reduce high radon concentrations in existing homes. As new homes are constructed, a radon proof barrier installed at ground level would be even lower cost, they conclude.