Radon gas is an odorless, tasteless, invisible gas which is produced as a result of the decay of uranium present in soil and rock. The gas can diffuse from the ground into the air, and can also seep into groundwater. Radon exposure may lead to cancer if the gas exposure occurs consistently over a long period of time.
Radon is present in very small amounts in almost all of the world’s air supply. At these very low concentrations, there is no risk of radon exposure causing toxic effects. In some locations, such as areas where ventilation is inadequate or where increased amounts of radon gas are present, however, radon concentration may approach toxic levels.
Low-ventilation locations such as mines are at risk of high levels of radon accumulation. Private homes and public buildings are at risk too, although the risk is much lower. In above-ground buildings, radon gas can seep through holes and cracks in floors and walls. Buildings most at risk are those which are located on or close to soil which contains high levels of uranium. Generally, it is the basement and lower floors which are at greatest risk of toxic levels of radon. People who work or live in such locations are at risk of radon exposure and the cancer that can develop as a consequence.
Chronic radon gas exposure is known to cause at least one type of cancer. When radon gas is inhaled, radioactive particles damage the cells of the lungs, causing DNA damage that cells are unable to repair. Accumulated DNA damage can eventually lead to the development of cancer.
Lung cancer is the only cancer which has been conclusively linked to exposure to radon gas. Although the existence of the link is clear, the strength of the link is not entirely certain because radon gas is not the only cause of lung cancer. One estimate indicates that between 15,000 and 22,000 people die from lung cancer caused by radon exposure each year in the United States alone.
The risk of developing lung cancer as a result of radon gas exposure is greater among people who smoke. Most people who die from radon-related lung cancer are smokers; however the reason why the combination of smoking and radon exposure is more lethal is unknown. There is also an increased risk for people who live with smokers and who are exposed to higher concentrations of radon gas.