Probability of Home Having Elevated Radon Levels

The EPA estimates that about 1 in 15 US homes (approximately 6.7%) has radon levels at or above the recommended action level of 4 picocuries per liter (pCi/L). Radon is a naturally occurring radioactive gas that seeps into buildings from the ground and is the second leading cause of lung cancer (after smoking), causing about 21,000 deaths per year.

Radon is present in all 50 states, though levels vary significantly by geography. The highest concentrations tend to occur in the northern and central United States, particularly in areas with granite, shale, and phosphate-rich soils. Radon enters homes through cracks in foundations, gaps around pipes, and other openings. It cannot be seen, smelled, or tasted.

Testing is the only way to know your home's radon level. Short-term test kits (2-7 days) are available at hardware stores for about $15-30, and many state health departments offer free or low-cost kits. If levels are elevated, radon mitigation systems (typically a vent pipe and fan that pulls radon from beneath the foundation) cost $800-$2,500 and reduce radon levels by up to 99%. Testing before buying a home is strongly recommended.