According to the surgeon general, only tobacco smoke causes more lung cancer every year in the United States, the U.S. Environmental Protection Agency (EPA) reports. The EPA estimates that radon is responsible for more than 20,000 deaths in the United States alone each year.
Radon naturally forms underground as uranium deposits degrade. The radioactive gas moves through the soil and water and can seep through even the tiniest cracks or holes in the foundation of any home. It can also enter with well water. Since radon is heavier than air, it becomes trapped once inside.
The EPA recommends that all homeowners regularly test for radon. Inexpensive, short-term tests are available at many hardware stores. For more definitive results you will have to hire a radon testing professional. Radon levels lower than four picocuries (a measurement of radioactivity) per liter of air are normal, but the EPA recommends hiring a radon-proofing service for higher levels. These professionals can seal cracks through which radon enters and install radon handling devices.