The United States Environmental Protection Agency established 4 picocuries per liter of air as the recommended action level for radon in homes. If the radon levels in a home are above the recommended action level, the homeowner should take steps to reduce the amount of radon present.
Exposure to radon at any level, even below the recommended action level, poses an increased risk of lung cancer. According to the U.S. Surgeon General, exposure to radon gas indoors is the second-leading cause of lung cancer in the United States. The only way to determine radon levels within a home is to perform testing. Do-it-yourself radon testing kits are available.