It is harmlessly dispersed in outdoor air, but when trapped in buildings, can be harmful, especially at elevated levels. Radon is a radioactive decay product of radium, which is itself a decay product of uranium. Uranium and radium are both common elements in soil. The primary source of high levels of radon in homes is the surrounding soil. Radon has been found in elevated levels in homes in every state, and the U.S. Environmental Protection Agency estimates that as many as one in 15 homes across the U.S. have elevated radon levels.
Warm air rises.
When this happens in your home, it creates a vacuum in the lower areas of the house. Nature hates a vacuum, so something must rush in to fill it. Exposure to radon is the second leading cause of lung cancer in the U.S. Radon can be inhaled into the lungs, where it undergoes radioactive decay. This damaged DNA can lead to lung cancer. Radon test kits that meet EPA guidelines can be obtained from a radon testing company or laboratory.