Radon

First—What is Radon?

Radon is a naturally occurring element on the Periodic Table (#86) and is a radioactive gas. It has no smell, color, or taste, and is produced from the natural radioactive decay of uranium in rocks and soil. Radon can also be found in water.

Radon gas escapes easily from the ground into the air. Outdoors, radon quickly dilutes to very low concentrations and is generally not a problem. However, because it is heavy, it tends to concentrate in enclosed spaces, such as underground mines, houses, and other buildings. Soil gas infiltration is recognized as the most important source of residential radon. Other sources of radon include building materials and water from wells, but they are less important.

Radon has a short half-life (about 4 days)and causes lung damage through its radioactive decay. It breaks down into solid radioactive elements, such as Polonium and Lead (radon progeny), that cling to dust particles and settle in the airways. These trapped particles emit alpha radiation directly into lung tissue. Those high-energy particles cause lethal or sublethal lesions in the epithelial cells lining the lungs, leading to DNA mutations. Because these cells cannot repair DNA damage effectively, they can become malignant, leading to lung cancer.

Radon is the second leading cause of lung cancer behind smoking. It causes between 3–14% of all lung cancers, depending on the average radon level and the smoking prevalence in a country. Radon is much more likely to cause lung cancer in people who smoke: smokers are 25 times more at risk from radon than non-smokers.

Radon levels are primarily measured in picocuries per liter (pCi/L). Its exposure in homes is often compared to smoking cigarettes based on equivalent lung cancer risk, with the United States EPA noting that 4 pCi/L of radon is comparable to smoking 8 cigarettes per day. To convert your tested home radon level, simply multiply it by 2 to obtain an equivalent cigarette-smoking risk.