Why Do So Many Non-Smokers Get Lung Cancer?
Read: "A Susceptibility Locus on Chromosome 6q Greatly Increases Lung Cancer Risk Among Light and Never Smokers". If you've got the gene your risk of lung cancer goes up nearly 500% even if you never smoke (in fact smoking only weakly increases your risk if you've got the gene). Interestingly, if you don't have the gene and you smoke your risk goes through the roof.