Radon
Although it has received attention as an environmental hazard only recently, radon is a naturally occurring radioactive gas that is present at low concentrations everywhere in the environment. Colorless and odorless, radon is a decay product of radium; radium is a decay product of the radioactive element uranium, which occurs naturally in the earth's crust. Radon continues to break down into products called radon progeny. Radon is measured in units called picocuries per liter (pCi/L), and it becomes a health concern when people are exposed to concentrations higher than normal background levels. Some geologic formations, such as the Reading Prong in New Jersey, are naturally very high in radon emissions.
During their normal decay process, radioactive elements emit several kinds of radiation, one of which is alpha radiation. The health effects of radon are associated with these alpha particles. These particles are too heavy to travel far and they cannot penetrate the skin, but they can enter the body through the lungs during inhalation. Studies of miners exposed to high concentrations of radon have shown an increased risk of lung cancer, and this is the health effect most commonly associated with radon. Background levels are usually estimated at 1 pCi/L. It is estimated that a person exposed to this concentration for 18 hours a day for five years increases their risk of developing cancer to one in 1000. At radon levels of 200 pCi/L, the increased risk of lung cancer after five years of exposure at 18 hours per day rises to 60 in 1,000. Because cancer is a disease that is slow to develop, it may take five to 50 years after exposure to radon to detect lung cancer.
In the outdoor environment, radon gas and its decay products are usually too well-dispersed to accumulate to dangerous levels. It is indoors without proper ventilation, in places such as basements and ground floors, where radon can seep from the soil and accumulate to dangerous concentrations. The most common methods of reducing radon buildup inside the home include installing blowers or simply opening windows. Plugging cracks and sealing floors that are in contact with soil also reduces the concentration. In the United States, environmental and public health agencies have instituted free programs to test for radon concentrations, and they also offer assistance and guidelines for remedyingthe problem.
The shaded areas on the map have potentially high levels of uranium in the soil and rocks. Radon levels may be high in these areas. (McGraw-Hill Inc. Reproduced by permission.)Radiation Exposure; Radioactive Decay; Radioactive Pollution; Radioactivity
Resources
Books
Brenner, D. J. Radon: Risk and Remedy. Salt Lake City: W. H. Freeman, 1989.
Cohen, B. Radon: A Homeowner's Guide to Detection and Control. Mt. Vernon, NY: Consumer Report Books, 1988.
Kay, J. G., et al. Indoor Air Pollution: Radon, Bioaerosols, and VOCs. Chelsea, MI: Lewis, 1991.
Lafavore, M. Radon: The Invisible Threat. Emmaus, PA: Rodale Press, 1987.
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