The gas seeps from soil and rocks into water and air. Radon may enter a basement through cracks or other openings. If the building is in a high-radon area, the gas may build up inside to an unhealthy level. Radon atoms decay by giving off a form of radiation called an alpha particle. When a radon atom decays, it becomes an atom of the radioactive element polonium.
Further decay produces atoms of other elements.
How radon affects health. Radon daughters cling to airborne dust particles and can catch in the lungs when people breathe them. When well water contains high levels, turning on faucets or showers may release radon and its daughters into the air. Some radon may also enter the body when people drink water containing the gas. Alpha particles released by radon and its daughters in the body disrupt the normal genetic or chemical processes of living cells, causing cells to grow abnormally or to die.