Radon is a radioactive gas that is colorless, odorless, tasteless, and chemically inert. It is one of the heaviest substances that remains a gas under normal conditions and is considered to be a health hazard due to its radioactivity.
Radon is formed by the natural radioactive decay of uranium in rock, soil, and water. Naturally existing, low levels of uranium occur widely in Earth's crust. It can be found in all 50 states. Once produced, radon moves through the ground to the air above. Some remains below the surface and dissolves in water that collects and flows under the ground's surface.
Breathing high concentrations of radon can cause lung cancer. Thus, radon is considered a significant contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency, radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States.
Depending on how houses are built and ventilated, radon may accumulate in basements and dwellings. Unless you test for it, there is no way of telling how much is present.