1. Introduction Radon (222Rn) is a radioactive gas generated from the decay of uranium radioactive series. Inhaling radon radioactive gas and its short-lived decay progenies can damage the respiratory system and increase the incidence of lung cancer. The excess relative risk (ERR) and lung cancer risk due to continuous exposure to high radon concentrations in the home are comparable to those of miners, indicating a correlation between lung cancer risk and residential radon exposure [1,2,3].