Water, when in contact with rock containing uranium, absorbs the radon gas. The radon is then carried into the home and released into the air in household dishwashers, faucets, showers, or washing machines. Water-related radon problems usually involve deep private wells rather than community water supplies. In some unusual situations, radon may be released from home construction materials such as stone used to build fireplaces or solar heating storage systems. Radon is not a problem outdoors because it is quickly diluted to low levels by outdoor air.
Cigarette smoking remains the primary cause.
While an area's geology may indicate the potential for radon problems, human senses cannot pick up any evidence of this odorless, colorless gas. Measuring for radon can be done simply and relatively inexpensively. The American Lung Association as well as the EPA and the Surgeon General recommend testing all homes below the third floor for radon. Testing in schools is also recommended. Choose a test kit that has passed EPA's testing program or is state-certified.