Excessive exposure to radon gas causes lung cancer, according to the American Cancer Society. It is also possible that radon gas increases the risk of other types of cancer as well as noncancerous respiratory illnesses, but as of 2015, more investigation is necessary to confirm these links.
Lung cancer occurs when radon particles embed themselves in the lining of the lungs and proceed to cause radioactive damage to the lung cells. Individuals who have long-term exposure to cigarette smoke as well as radon gas are most at risk of developing lung cancer, states the American Cancer Society. Some studies indicate that there is a correlation between high levels of radon exposure and incidences of respiratory diseases such as pulmonary fibrosis, emphysema and chronic bronchitis.