Radon is found throughout the world and is a byproduct of the decay of naturally occurring uranium in the rocks and soil. While outdoor radon levels aren't highly concentrated and pose little danger to humans, indoor radon levels may become elevated and represent a serious threat to your health. Long-term inhalation of radon can lead to lung cancer and death.
Origin
Radon occurs naturally in all parts of the United States and can be found in the air, water and rocks. The source of radon gas is uranium. According to the U.S. Geological Survey, all rocks contain some uranium, although the amount is usually only 1 to 3 parts per million, which is not harmful to humans. Some types of rock, such as granite and dark shale, contain larger amounts of uranium---as high as 100 parts per million. As uranium naturally decays, it produces radon gas and radium.
Granite Countertops
While granite naturally contains uranium and its daughter product, radon gas, the EPA has determined that the small amount of radon from granite countertops is unlikely to be a serious health problem. Because kitchens and bathrooms are usually well-ventilated, radon from countertops is less likely to become trapped and cause health problems.
Air
Radon gas leaches out of surrounding rocks and foundations and becomes trapped in buildings. The Environmental Protection Agency estimates that radon is the leading cause of lung cancer for nonsmokers and may be responsible for 21,000 deaths each year. Radon is found in outside air as well as inside air but is not concentrated outdoors and is less of a health problem. Even small amounts of radon gas, when inhaled over a period of several years, can cause cancer. The average American home has radon concentrations more than three times higher than are found outdoors. The EPA considers radon to be unsafe in any concentration.
Well Water
Radon can also be found in well water. Surface water, such as rivers and lakes, allows radon to dissipate into the atmosphere, leaving the water with a low level of radon. In enclosed areas such as wells, however, radon seeps into the water from surrounding rock, where it becomes trapped. Once the well water is brought to the surface, the radon gas escapes from the water into the air inside the home. Groundwater that flows through granite rock formations is most likely to contain radon.
Basements
Radon released from rocks and soil can enter buildings through cracks in the foundation or through holes for pipes. The air pressure inside a home is generally less than that in the surrounding ground, so radon is sucked into the home and becomes trapped in basements and other parts of the building. Radon concentrations tend to be higher in basements and lower levels of the home. Remediation techniques include venting the basement or crawlspace areas of the home and sealing cracks and basement floors with a nonporous caulk or sealant.
