Found in rock, soil, water, natural gas, and some building materials, radon is a radioactive gas. Exposure to radon can cause cancer. Radon can seep in through the foundation of a home or building built on radon-contaminated soil. Inhabitants of homes contaminated with radon or those who work in buildings where radon has seeped in may be at a greater risk of developing cancer than those who do not live or work in such buildings. According to the U.S. Environmental Protection Agency, radon is responsible for about 21,000 deaths from lung cancer each year in the United States alone, and roughly 1 out of every 15 homes in the U.S. has unsafe levels of radon.Radon is most often found in basements because the gas sinks to the lowest points in buildings. However, even those homes or buildings without basements can have unsafe levels of radon. Property owners should have their homes or buildings tested for radon, as exposure to radon does not produce any symptoms, meaning those who live and work in buildings where they are being exposed to radon won't know unless buildings are routinely tested. Kits to test radon levels can be purchased at many hardware stores, or property owners can hire professionals to conduct tests for them.