Radon and its decay products are inhaled and the decay products become lodged in the lungs where they can radiate the cells lining the respiratory system. The radioactive decay products of the radon emit alpha particles that are damaging to these tissues. Exposure to elevated levels of radon greatly enhances the risk of lung cancer. Even small exposures to radon can result in increased cancer risk. Smoking combined with radon poses a very serious risk. The effect of radon among smokers is about 9 times higher than in non-smokers.