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This booklet on radon has been developed for physicians by the U.S. Environmental Protection Agency in consultation with the American Medical Association (AMA). Its purpose is to enlist physicians in the national effort to inform the American public about the serious health risk posed by indoor radon gas. INTRODUCTIONLung cancer's very high associated mortality rate is even more tragic because a significant portion of lung cancer is preventable. While smoking remains the number one cause of lung cancer, radon presents a significant second risk factor. That is why, in addition to encouraging patients to stop smoking, it is important for physicians to inquire about and encourage patients to test for radon levels in their homes. One way to do this is for physicians to join those health care professionals and organizations who have begun to include questions about the radon level in patients' homes on standardized patient history forms. Because the public views physicians as advisors on health and prevention of disease, physicians are in a unique position to play a vital role in informing the public about the common and serious risk of radon, and in educating their patients in testing procedures and remediation methods for correcting elevated indoor radon levels, thereby helping to reduce the number of lung cancer deaths. Free radon information materials (posters, pamphlets, videos) are available from your state radon office to assist you in educating your patients about radon.
Radon Causes Thousands Of Preventable Lung Cancer Deaths Each YearEach year in the United States exposure to indoor radon gas causes thousands of preventable lung cancer deaths. In fact, the Surgeon General has warned that radon is the second leading cause of lung cancer in the United States. Extensive epidemiological evidence from studies of underground miners, complemented by animal data, indicates that radon causes lung cancer in both smokers and nonsmokers, although malignancy is especially likely to occur in cigarette smokers. Exposure to both smoking and radon greatly enhances the risk of lung cancer. The carcinogenicity of radon is supported by a consensus of opinion among national and international health organizations. By informing patients about the health risk posed by radon exposure and providing practical advice about radon testing and mitigation, physicians can have a tremendous positive impact on the national effort to prevent radon-induced lung cancer. Radon is estimated to cause about 14,000 deaths per year -- however, this number could range from 7,000 to 30,000 deaths per year. The numbers of deaths from other causes are taken from the 1990 National Safety Council reports.
Radon Is Easy To Detect And Reduce In A HomeThe danger posed by radon can be detected rather easily through inexpensive do-it yourself testing, or through a trained radon contractor. Radon test kits can be purchased by mail order or in hardware stores and other retail outlets. Because of the serious health risk posed by radon, the U. S. Environmental Protection Agency (EPA) recommends that all homes be tested for radon below the third floor. If an elevated radon level is discovered in a home, it can be corrected. It is recommended that a confirmed radon level of 4 picocuries per liter (pCi/L) of air or higher be reduced to decrease the risk of developing lung cancer. The cost of radon mitigation in a typical home ranges from about $500 to about $2,500. Your state radon information office (see page toward end of this brochure) can provide general advice about radon testing and mitigation, as well as specific information about qualified radon contractors in your state.
Return to the Table of Contents Radon-222 is a radioactive gas released during the natural decay of thorium and uranium, which are common, naturally occurring elements found in varying amounts in rock and soil. Odorless, invisible, and without taste, radon cannot be detected with the human senses. Radon-222 decays into radioactive elements, two of which -- polonium-218 and polonium-214 -- emit alpha particles, which are highly effective in damaging lung tissues. These alpha-emitting radon decay products have been implicated in a causal relationship with lung cancer in humans. Return to the Table of Contents CHARACTERISTICS AND SOURCES OF RADONOutdoors, where it is diluted to low concentrations in the air, radon poses significantly less risk than indoors. In the indoor air environment, however, radon can accumulate to significant levels. The magnitude of radon concentration indoors depends primarily on a building's construction and the amount of radon in the underlying soil. The soil composition under and around a house affects radon levels and the ease with which radon migrates toward a house. Normal pressure differences between the house and the soil can create a slight vacuum in the home that can draw radon gas from the soil into the building. Radon gas can enter a home from the soil through cracks in concrete floors and walls, floor drains, sump pumps, construction joints, and tiny cracks or pores in hollow-block walls. Radon levels are generally highest in basements and ground floor rooms that are in contact with the soil. Factors such as the design, construction, and ventilation of the home affect the pathways and sources that can draw radon indoors. Another source of radon indoors may be air released by well water during showering and other household activities. Compared to radon entering the home through soil, radon entering the home through water will in most cases be a small source of risk.
Return to the Table of Contents How Does Radon Induce Cancer?If inhaled, radon decay products (polonium-218 and polonium-214, solid form), unattached or attached to the surface of aerosols, dusts, and smoke particles, become deeply lodged or trapped in the lungs, where they can radiate and penetrate the cells of mucous membranes, bronchi, and other pulmonary tissues. The ionizing radiation energy affecting the bronchial epithelial cells is believed to initiate the process of carcinogenesis. Although radon-related lung cancers are mainly seen in the upper airways, radon increases the incidence of all histological types of lung cancer, including small cell carcinoma, adenocarcinoma, and squamous cell carcinoma. Lung cancer due to inhalation of radon decay products constitutes the only known risk associated with radon. In studies done on miners, variables such as age, duration of exposure, time since initiation of exposure and especially the use of tobacco have been found to influence individual risk. In fact, the use of tobacco multiplies the risk of radon-induced lung cancer enormously. What is the Evidence?More is known about the health risk of radon exposure to humans than about most other human carcinogens. This knowledge is based on extensive epidemiological studies of thousands of underground miners, carried out over more than fifty (50) years world-wide, including miners in the United States and Canada. In addition to the miner data, experimental exposures of animals confirm that radon and its decay products can cause lung cancer. The research on lung cancer mortality in miners exposed to radon progeny is substantial and consistent. Studies of thousands of miners, some with follow-up periods of thirty (30) years and more, have been conducted in metal, fluorspar, shale, and uranium mines in the United States, Canada, Australia, China, and Europe. These studies have consistently shown an increase in lung cancer occurrence with exposure to radon decay products, despite differences in study populations and methodologies. The miner studies produced some interesting findings.
The following table lists seven (7) of the major epidemiological studies of underground miners and their reported relative risk coefficients.
A detailed discussion of the strengths and weaknesses of the various miner studies can be found in the EPA's Technical Support document for the 1992 Citizen's Guide to Radon, available from your state radon office, or the BEIR IV Report (National Academy of Sciences (NAS) 1988). Animal experiments conducted in the United States and France also have confirmed the carcinogenicity of radon and have provided insight into the nature of the exposure-response relationship, as well as the modifying effects of the exposure rate. To date these animal studies have produced several relevant findings.
In 1988, a panel of world experts convened by the World Health Organization's International Agency for Research on Cancer unanimously agreed that there is sufficient evidence to conclude that radon causes cancer in humans and in laboratory animals (IARC, 1988). Scientific committees assembled by the National Academy of Sciences (NAS, 1988), the International Commission on Radiological Protection (ICRP, 1987), and the National Council on Radiation Protection and Measurement (NCRP, 1984) also have reviewed the available data and agreed that radon exposure causes human lung cancer. Recognizing that radon is a significant public health risk, scientific and professional organizations such as the American Medical Association, the American Lung Association, and the National Medical Association have developed programs to reduce the health risks of radon. The National Institute for Occupational Safety and Health (NIOSH) reviewed the epidemiological data and recommended that the annual radon progeny exposure limit for the mining industry be lowered (NIOSH 1987). Is Occupational Exposure to Radon Comparable to Residential Exposure? Because questions have been raised about the appropriateness of using the epidemiological studies of underground miners as a basis for estimating the risk radon poses to the general population, the EPA commissioned the National Academy of Sciences (NAS) to investigate the difference between underground miners and members of the general public in the doses they receive per unit exposure due to inhaled radon progeny. The NAS report, published in 1991 (National Academy of Sciences, 1991, Comparative Dosimetry of Radon in Mines and Homes. National Academy Press, Washington, D.C.), concluded that it is reasonable to extrapolate from the miner data to a residential situation, but that the effective doses per unit of exposure for people in their homes is approximately thirty percent (30%) less than for the miners. In its analysis, NAS considered variables such as the amount and type of dust to which the radon decay particles would attach, the breathing rate of working miners compared to that of people at home, and the presence of women and children in the homes. EPA has adjusted its residential risk estimates accordingly. The result is still considerable--EPA now estimates that approximately 14,000 lung cancer deaths in the United States per year are due to residential radon exposures, with an uncertainty range of 7,000 to 30,000. As more data are gathered about residential radon exposures, the risk estimates may be adjusted further. Enough data exists now, however, to be able to say with certainty that thousands of preventable lung cancer deaths annually in the United States are attributable to indoor residential exposure to radon. More information about residential exposure to radon is needed to answer important questions about radon's effect on women and children--groups not included in the occupational studies of miners. Although children have been reported to be at greater risk than adults of developing certain types of cancer from radiation, currently there is no conclusive evidence that radon exposure places children at any greater risk. Some miner studies and animal studies indicate that for the same total exposure, a lower exposure over a longer time is more hazardous than short, high exposures. These findings increase concerns about residential radon exposures. Epidemiological case control studies are underway in the U.S. and Europe, the pooled results of which should enhance the understanding of the risk of residential exposure to radon. What About Smoking and Radon Exposure? Some people ask whether the lung cancer deaths attributed to radon exposure actually may be the result of smoking. A 1989 study by researchers from the National Institute for Occupational Safety and Health, the Centers for Disease Control, the Harvard School of Public Health, and the University of California at Davis demonstrated a greatly incased lung cancer risk in nonsmoking uranium miners exposed to high radon concentrations: compared to typical non-smoking populations, these miners had nine (9) to twelve (12) times the risk of developing lung cancer (Roscoe et al, JAMA 262(5): 629-633, 1989). Evidence from some of the epidemiological studies of underground miners, primarily U. S. uranium miners, indicate that radon exposure and smoking may have a synergistic relationship. Either smoking or radon exposure can independently increase the risk of lung cancer; however, exposure to both greatly enhances that risk. Return to the Table of Contents Why Should Every Home be Tested?The EPA and the U. S. Surgeon General recommend testing all homes below the third floor for radon. Data gathered by the EPA national radon survey indicate that elevated radon levels are present in about six million (6,000,000) homes throughout the United States. In every state there are homes with dangerously high radon levels. Because the radon concentration inside a home is due to factors relating to its structure and geographic location, each individual home must be tested to determine its radon level. Two adjacent houses may have radically different radon levels. And any kind of home can have elevated levels -- new or old, drafty or well-sealed, and basement or non-basement. How do You Obtain a Reliable Test Result?Although radon cannot be seen or smelled, with the proper equipment its presence is relatively easy to detect. The EPA operates a voluntary Natonal Radon Proficiency (RPP) Program that evaluates radon measurement companies and the test services they offer. EPA recommends that testing services be purchased from one of the organizations listed by EPA or certified by the state. Most companies indicate U.S. EPA or RMP approval on the test kit box by displaying the phrase, "Meets EPA Requirements." A list of radon measurement companies and individuals the EPA has determined to be "proficient" can be obtained from our web site or the State Radon Office. A test kit obtained from a qualified company, if used according to directions, should provide accurate results. Radon Testing MethodsThe quickest way to test for radon is with a short-term "do-it-yourself" radon test kit, available by mail order and in many retail outlets or by hiring an EPA qualified or state-certified radon tester. Common short-term test devices are charcoal canisters, alpha track detectors, liquid scintillation detectors, electret ion chambers, and continuous monitors. A short-term testing device remains in the home for two (2) to ninety (90) days, depending on the type of device. Because radon levels tend to vary from day-to-day and season-to-season, a long-term test is more likely than a short-term test to measure the home's year-round average radon level. If results are needed quickly, however, a short-term test followed by a second short-term test may be used to determine the severity of the radon problem. Long-term test devices, comparable in cost to devices for short-term testing, remain in the home for more than three (3) months. A long-term test is more likely to indicate the home's year-round average radon level than a short-term test. Alpha track detectors and electret ion detectors are the most common long-term test devices. Radon Test DevicesCharcoal canister and liquid scintillation detectors contain small quantities of activated charcoal. Radon and its decay products are absorbed onto the charcoal and are measured by counting with a sodium iodide detector or a liquid scintillation counter. Alpha track detectors contain a small sheet of plastic that is exposed for a period of one (1) to three (3) months. Alpha particles etch the plastic as they strike it. These marks are then chemically treated and counted in the laboratory to determine the radon concentration. Electret ion detectors contain an electrostatically charged Teflon disk. Ions generated by the decay of radon strike and reduce the surface voltage of the disk. By measuring the voltage reduction, the radon concentration can be calculated. Continuous monitors are active devices which need power to function. They require operation by trained testers and work by continuously measuring and recording the amount of radon in the home. How To TestDuring a short-term test, doors and windows are closed twelve (12) hours prior to testing and throughout the testing period. (A short-term test lasting two (2) or three (3) days should not be conducted during unusually severe storms or periods of unusually high winds.) The test kit is placed in the lowest lived-in level of the home, at least twenty (20) inches above the floor, in a room that is used regularly, but not in the kitchen or bathroom where high humidity or the operation of an exhaust fan could affect the validity of the test. At the end of the test period, the kit is mailed to a laboratory for analysis; results are mailed back in a few weeks. In some cases, such as real estate transactions, trained EPA-listed or state-certified contractors conduct the radon test. The EPA's pamphlet Home Buyer's and Seller's Guide to Radon, which addresses issues during real estate transactions, is also available from state radon offices.
Basis for the 4 pCi/L Radon "Action Level"
Radon Reduction Methods
Return to the Table of Contents OTHER INDOOR AIR POLLUTANTSEnvironmental Tobacco Smoke (ETS)
Return to the Table of Contents
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