Radon Definition: Radon is a colorless, odorless radioactive gas that occurs naturally in the environment. Produced by the decay of uranium in soil and rock, radon is released into air and water. The average outdoor radon level is about 0.4 pCi/L.
Radon can become concentrated in homes and other buildings. If it occurs at high enough levels, it can cause serious health problems, including lung cancer. In fact, radon is the number one cause of lung cancer in nonsmokers and is the second leading cause of lung cancer overall.
The U.S. Surgeon General, the U.S. Environmental Protection Agency (EPA), the World Health Organization (WHO), and many other organizations and agencies recommend that all homes be tested for radon in air. EPA, the Centers for Disease Control (CDC), the Surgeon General, the American Lung Association, the American Medical Association, and others recommend radon testing and encourage action when levels are above 4 pCi/L (picocuries per liter of air). WHO recommends action at 2.7 pCi/L.
Radon in water also poses serious health risks. Experts recommend that all public and private wells be tested for radon. Based on a National Academy of Science report on radon in drinking water, EPA estimates that radon in drinking water causes about 168 cancer deaths per year, 89 percent from lung cancer caused by breathing radon released from water, and 11 percent from stomach cancer caused by drinking radon-containing water.