 For this population about 62 people in a total of 1,000 will die of lung cancer compared to 7 people in a total of 1,000 for people who have never smoked.It cannot be excluded that the risk of non-smokers should be primarily explained by a combination effect of radon and passive smoking.Radon, like other known or suspected external risk factors for lung cancer, is a threat for smokers and former smokers.