ABSTRACT
People are generally exposed to radiation from natural sources. Radon is the most important radiation source among natural sources. Radon is a naturally occurring, radioactive noble gas that is odorless and tasteless. Radon is normally found at very low levels in outdoor air and in drinking water from rivers and lakes but higher levels in indoor air in homes, schools, and office buildings, and in well water. When radon undergoes radioactive decay, it expels high-energy alpha particles. The alpha particle radiation dose from long-term exposure increases the chance of developing lung cancer. Radon is the second most important cause of lung cancer after smoking. There is no known threshold concentration below which radon exposure presents no risk. Even low concentrations of radon can result in a small increase in the risk of lung cancer. No study of the radon exposure-lung cancer association has been performed in Korea. What is needed is a large-scale prospective study of the association between residential radon exposure and lung cancer. The cumulative indoor radon exposure is an important environmental health hazard (carcinogen).