Even that is not as big of a risk as many think. It is not a secret that it has been known for decades that radon is more of a factor in lung cancer than smoking is. Smoking is much more of a factor in emphysema than it is in cancer. This was even known in the 1980's, when a report was released that noticed that the highest risk of a person getting lung cancer was not related to smoking, but if they lived in a basement. And the chances even among a smoker was greatly reduced if they lived in the upper floor of a building. I am not downplaying the risk of smoking and saying it is not harmful. Those that smoke (I am one of them) are at much greater risk of lung and heart disease. But the risk of lung cancer is now blamed more on radon than smoking itself. Especially as over the decades the number of smokers has decreased, yet the rate of lung cancer has hardly budged.