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Radon is a naturally occurring, invisible, odorless gas that comes from deposits of uranium in sod, rock, and water. 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 a decay product of uranium. Both uranium and radium are common elements in soil.
The primary source of high levels of radon in homes is the surrounding soil and underlying rock. Radon in water is found in nearly all sources of surface water and groundwater. Water that flows through or over radium rich rock formations chiefly found in the Piedmont and mountain regions of the sate, accumulate radium and thus radon from the decay process. Groundwater usually has much higher levels than surface water because radon in groundwater is "trapped" by being submerged and cannot easily escape.
Air pressure inside your home is usually lower than pressure in the soil around your home's foundation. Because of this difference in pressure, your house acts like a vacuum, drawing radon in through foundation cracks and other openings like floor drains, ductwork, and pipes.
Radon may also be present in well water and can be released in the air in your home when water is used for showering and other household uses. In most cases, radon entering your home through water is a small risk compared with radon entering your home from the soil.
Exposure to radon is the second leading cause of lung cancer in the United States. Radon can be inhaled into the lungs, where it undergoes radioactive decay. As it decays, radon releases tiny bursts of energy called alpha particles, which can harm sensitive lung tissue by damaging the DNA. This damaged DNA can lead to lung cancer.
The main type of cancer caused by radon in water is also lung cancer. This is because a large fraction of radon in water is released to the air when water is used in common household tasks such as showering, washing clothes, and other uses where water can become vaporized.
Radon is measured in picocuries per liter or air (pQ/L). The U.S. Environmental Protection Agency and the Centers for Disease Control and Prevention recommend that homes with radon levels or about 4 pG/L be fixed. The "action" levels in water are set much higher at 300 pG/L.
The water levels are considerably higher because it takes high levels of radon in water to produce significant levels of radon in air. The rule of thumb is that it takes 10,000 pG/L or radon in water to raise the level of radon in air 1 pG/L. Using this rule, it would take 40,000 pG/L in water to raise the indoor air radon level to 4 pG/L.
The Environmental Health Services Division at the Orange County Health Department has radon air sampling canisters available at no charge for residents in areas where there may be concern about high levels of indoor radon. A limited number of water sample kits are also available through Environmental Health. Staff will either collect the water samples or help homeowners to self-collect water samples.
You may also get air testing and water testing kits through a list of distributors on the web site at the bottom of the page or by calling Orange County Health Department at 919-245-2360 if you do not have internet access.
Radon problems can sometimes by fixed by caulking cracks along basement foundations, sealing leaks around pipes, or installing a pipe and fan system to vent the radon away from beneath the house. If water is releasing a significant amount into the indoor air space, water aeration or carbon filters that absorb the radon may help the situation. There is a list of North Carolina organizations that specialize in radon mitigation (radon reduction systems) on the North Carolina extension website or by calling Orange County Environmental Health Services at 919-245-2360.