We do know smoking tobacco and being exposed to radon have a cumulative effect. If you smoke and you're subjected even to moderate levels of radon, the chances of developing lung cancer are much greater than if you do not have radon in your home or are exposed to low levels of radon. Radon has been found in elevated levels in homes in every state. The U.S. Environmental Protection Agency estimates that as many as one in 15 homes across the U.S. has elevated radon levels. The primary source of high levels of radon in homes is the soil below the dwelling.
Radon is a natural, radioactive decay product of radium, which is itself a decay product of uranium.
Uranium and radium are both common elements found in rock, soil, and water. Radon is harmlessly dispersed in outdoor air, but when trapped in buildings it can be harmful, especially at elevated levels. Radon gas enters a home the same way air and other soil gases enter the home, through cracks in the foundation, floor or walls, hollow-block walls, and openings around floor drains, pipes, and sump pumps. It can also be present in some construction materials and in water from underground sources including private wells. Testing for Radon Radon is measured in picocuries per liter of air, a measurement of radioactivity.