Radon is the gaseous product of radium and uranium decay, and as such, it is a radioactive substance. Both of these metals are found naturally in trace amounts in soil and water, meaning that radon gas itself is naturally present in very low levels soil, water and air. In these very low levels, the gas is not harmful. Exposure to high concentrations of radon gas, or exposure to radon gas over a long period of time, can be toxic. Harmful radon effects include respiratory diseases, lung cancer and birth defects.
Toxic levels of exposure to radon gas can occur in certain locations. The most at-risk locations are those where radon gas is naturally present in higher amounts than normal, such as that which can occur in mines. Public and private buildings also can be at risk, especially if they are poorly ventilated or contain sub-ground levels. People who live or work in such places are at risk of chronic exposure to the gas and the harmful radon effects that can result.
Exposure to radon gas is conclusively known as a causative agent of lung cancer. The exact nature of the link is difficult to determine, however, because there are many other agents that cause lung cancer. For example, if someone with lung cancer is a smoker who was exposed to radon gas, it is impossible to determine whether the gas exposure or cigarette smoking was the main cause of the cancer. Despite this, it is clear that radon gas can cause lung cancer, and it is known that someone who has been exposed to radon gas is more likely to develop lung cancer if he or she also is a smoker.
The root cause of cancerous radon effects is the damage done to deoxyribonucleic acid (DNA) as a result of radiation exposure. Radon gas is radioactive, and radioactive particles have the potential to enter cells and cause irreparable DNA damage. Sometimes cells can withstand small amounts of DNA damage without becoming cancerous, but accumulated damage over time eventually can cause cells to become malignant.
Chronic exposure to radon gas can cause other harmful radon effects in the lungs and respiratory system, such as pulmonary fibrosis, emphysema, chronic interstitial pneumonia and respiratory lesions. These diseases develop not as a direct result of DNA damage but because inhalation of radon gas causes chronic respiratory irritation or inflammation. In each disease, the delicate tissue of the lungs or airways is damaged by gas exposure, leading to cell death, scar tissue growth and reduced respiratory function.
Radon exposure usually affects the respiratory system, but some harmful radon effects occur elsewhere. The main non-respiratory radon risk is that a pregnant woman who is exposed to toxic levels of radon gas has a risk of giving birth to a baby with teratogenic birth defects. Teratogenic defects are those that affect the arms and legs, such as the malformation or absence of fingers, toes, a foot, a hand or an entire limb.
One of the problems in determining whether someone has been exposed to radon gas is that there are no acute effects or warning signs associated with radon exposure. Someone who is exposed to radon gas will not experience any radon effects for a very long time, even if he or she is exposed to very high levels of the gas. The risk of developing cancer or a chronic respiratory disease increases as exposure time increases, but there is no known safe level of radon exposure.