Radon is a radioactive, colorless, odorless gas derived from the radioactive decay of uranium in the soil. The United States Environmental Protection Agency (U.S. EPA) considers radon an environmental health concern because it is the second leading cause of lung cancer, surpassed only by smoking. According to the U.S. EPA, nearly one home in fifteen in the U.S. is estimated to have elevated radon levels-that is, a radon concentration above the U.S. EPA action level of 4 picocuries per liter of air (pCi/L).
According to the U.S. EPA radon program, "Four picocuries of radon per liter of air is a voluntary guideline level based on the existing radon reduction technologies. U.S. EPA chose the level because it can be achieved consistently and economically in nearly all structures."
Radon gas decays into radioactive particles that can get trapped in your lungs when you breathe. As they break down further, these particles release small bursts of energy. This can damage lung tissue and lead to lung cancer over the course of your lifetime. Not everyone exposed to elevated levels of radon will develop lung cancer. And the amount of time between the exposure and the onset of the disease may be years.
Like other environmental pollutants, there is some uncertainty about the magnitude of radon health risks. However, we know more about radon risks than risks from most other cancer-causing substances. This is because estimates of radon risks are based on studies of cancer in humans (underground miners). Additional studies on more typical populations are under way.
Smoking combined with radon is an especially serious health risk. Stop smoking and lower the radon level in your home to reduce your lung cancer risk.
Radon in Your Home
Typically, radon moves up through the ground to the air above and into your home through cracks and other holes in the foundation. Your home traps radon inside, where it can build up. Any home may have a radon problem. This means new and old homes, well-sealed and drafty homes and homes with or without basements.
Radon from soil gas is the main cause of radon problems. Sometimes radon enters the home through well water. In a small number of homes, the building materials can give off radon, too. However, building materials rarely cause radon problems by themselves.
Radon in Water
Compared to radon entering the home through soil, radon entering the home through water will in most cases be a small source of risk. Radon gas can enter the home through well water. It can be released into the air you breathe when water is used for showering and other household uses. Research suggests that swallowing water with high radon levels may pose risks, too, although risks from swallowing water containing radon are believed to be much lower than those from breathing air containing radon.
While radon in water is not a problem in homes served by most public water supplies, it has been found in well water. If you've tested the air in your home and found a radon problem, and your water comes from a well, contact a lab certified to measure radiation in water to have your water tested. If you're on a public water supply and are concerned that radon may be entering your home through the water, call your public water supplier.
Radon problems in water can be readily fixed. The most effective treatment is to remove radon from the water before it enters the home. This is called point-of-entry treatment. Treatment at your water tap is called point-of-use treatment. Unfortunately, point-of-use treatment will not reduce most of the inhalation risk from radon.