• Radon is the number one cause of lung cancer among non-smokers, according to EPA estimates. 
• Overall, radon is the second leading cause of lung cancer. 
• Radon is responsible for about 21,000 lung cancer deaths every year. 
• About 2,900 of these deaths occur among people who have never smoked. 
• "Indoor radon gas is the second-leading cause of lung cancer in the United States and breathing it over prolonged periods can present a significant health risk to families all over the country.  It's important to know that this threat is completely preventable.  Radon can be detected with a simple test and fixed through well-established venting techniques."  January 2005 U.S. Surgeon General Health Advisory

Studies Find Direct Evidence Linking Radon in Homes to Lung Cancer - Two studies show definitive evidence of an association between residential radon exposure and lung cancer.  Two studies, a North American study and a European study, both combined data from several previous residential studies.  These two studies go a step beyond earlier findings.  They confirm the radon health risks predicted by occupational studies of underground miner’s who breathed radon for a period of years. 

Early in the debate about radon-related risks, some researchers questioned whether occupational studies could be used to calculate risks from exposure to radon in the home environment.  “These findings effectively end any doubts about the risks to Americans of having radon in their homes,” said Tom Kelly, Director of EPA’s Indoor Environments Division.  “We know that radon is a carcinogen.  This research confirms that breathing low levels of radon can lead to lung cancer.”