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radon

  (rā'dŏn) pronunciation
n. (Symbol Rn)

A colorless, radioactive, inert gaseous element formed by the radioactive decay of radium. It is used as a radiation source in radiotherapy and to produce neutrons for research. Its most stable isotope is Rn 222 with a half-life of 3.82 days. Atomic number 86; melting point −71°C; boiling point −61.8°C; specific gravity (solid) 4.

[RAD(IUM) + –ON2.]


 
 
Sci-Tech Encyclopedia: Radon

A chemical element, Rn, atomic number 86. Radon is produced as a gaseous emanation from the radioactive decay of radium. The element is highly radioactive and decays by the emission of energetic alpha particles. Radon is the heaviest of the noble, or inert, gas group and thus is characterized by chemical inertness. More than 25 isotopes of radon have been identified. All isotopes are radioactive with short half-lives. See also Periodic table.

Radon is found in natural sources only because of its continuous replenishment from the radioactive decay of longer-lived precursors in minerals containing uranium, thorium, or actinium. 222Rn (half-life 3.82 days), 220Rn (thoron; half-life 55 s), and 219Rn (actinon; half-life 4.0 s), occur in nature as members of the uranium (U), thorium (Th), and actinium (Ac) series, respectively. All three decay by the emission of energetic alpha particles. See also Actinium; Radium; Uranium.

Any surface exposed to 222Rn becomes coated with an active deposit which consists of a group of short-lived daughter products. The radiations of this active deposit include energetic alpha particles, beta particles, and gamma rays. The ultimate decay products of radon following the rapid decay of the active deposit to lead-210 include bismuth-210, polonium-210, and finally, stable lead-206. Radon possesses a particularly stable electronic configuration, which gives it the chemical properties characteristic of noble gas elements. It has a boiling point of −62°C (−80°F) and a melting point of −71°C (−96°F). The spectrum of radon has been extensively studied, and resembles that of the other inert gases. Radon is readily adsorbed on charcoal, silica gel, and other adsorbents, and this property can be used to separate the element from gaseous impurities.

The rocks and soils of the Earth's crust contain approximately 3 parts per million of 238U, the long-lived head of the uranium series; 11 ppm of 232Th, the head of the thorium series; but only about 0.02 ppm of 235U, the long-lived member of the actinium group. The radon isotopes 222Rn and 220Rn are produced in proportion to the amount of the parent present. Some of the newly formed radon atoms which originate in or on the surface of mineral grains escape into the soil gas, where they are free to diffuse within the soil capillaries. Some of the radon atoms eventually find their way to the surface, where they become a part of the atmosphere. Even though thorium (232Th) is generally more abundant than uranium in the Earth's crust, the probability for decay is smaller; hence, the production rate of 222Rn and 220Rn in the soil is roughly the same. Much of the 220Rn decays before reaching the Earth's surface due to its short half-life.

When radon (222Rn or 220Rn) passes from soil to air, it is mixed throughout the lower atmosphere by eddy diffusion and the prevailing winds. Mean radon levels are found to be higher during those times of year when atmospheric stability is the greatest such as may occur during the fall months. Radon and its daughters play an important role in atmospheric electricity. Near the Earth's surface almost half of the ionization of the air is due to 220Rn and 222Rn and their daughter products. The alpha emitters from these chains typically produce about 107 ion pairs per second per cubic meter.

Radon is readily soluble in water. Since ground and surface waters are in close contact with soil and rocks containing small quantities of radium, it is not surprising to find radon in public water supplies.

The radon isotopes 220Rn and 222Rn are used widely in the study of gaseous transport processes both in the underground environment and in the atmosphere. Radon accumulates to high levels of the order of 4000 becquerels/m3 or more in caves unless natural or artificial ventilation occurs. Changes in 222Rn concentrations in spring and well water and in soil and rocks have been suggested as a means of predicting earthquakes.

The tendency of the decay products of radon to attach to aerosols means that these nuclides will be inhaled and deposited in the bronchial epithelium and lungs. The daughter products, therefore, make up the major part of the internal radiation dose from radon. Ways of reducing radon levels within homes or workplaces include increased ventilation and sealing of major sources of entry from soil and building materials. Workers in uranium mines may encounter radon and decay product levels of the order of 50,000 Bq/m3 or more. Ventilation procedures and special filters for the miners must be used.

 
Real Estate Dictionary: Radon

A naturally appearing (not man-made) gas that may contaminate water or air in buildings. Studies from mines have indicated a correlation between radon and lung cancer in humans. Homes that are too well insulated may trap radon gas, increasing its concentration. A pipe that serves to vent radon, especially from the basement to the roof, is often suggested to prevent its buildup.
Example: Because the region was known for radon, a cautious purchaser bought a kit to test for its presence inside the home, including its water supply.

 
Dental Dictionary: radon

n

A byproduct of radium decomposition used in radiotherapy.

 
Encyclopedia of Public Health: Radon

Radon-222 and radon-220 (thoron) are invisible, inert, and odorless radioactive gases formed in the decay of uranium-238 and thorium-232, respectively. Uranium-238 and thorium-232 are radionuclides that are widely distributed in the earth's crust. The half-life of radon-222 is long enough (3.82 days) to enable appreciable quantities of this element to accumulate in the environment, whereas the half-life of radon-220 is so short (55 seconds) that it does not attain environmental concentrations that produce demonstrable biological effects. Radon-222, seeping out of the soil, is ubiquitous in outdoor air, where its concentration averages about 15 becquerels per cubic meter (5 Bqm-3 or 0.4 pCi/L). (The becquerel [Bq] and the curie [Ci] are units of radioactivity; 1 Bq = 1 disintegration per second, and 1 Ci = 3.7 × 1010disintegrations per second. Radon is measured in picocuries per liter of air [pCi/L] or becquerels per cubic meter [Bqm-3].) In indoor air, the concentration of radon tends to be much higher than in outdoor air, especially in poorly ventilated basements and underground mines, where it may exceed 1,000 Bqm-3 (20 pCi/L). Indoor levels may be increased substantially by the use of groundwater or well water containing elevated concentrations of radon.

The alpha particles emitted by radon outside the body do not penetrate the skin, and radon itself, like other inert gases, is breathed in and out of the lungs without interacting significantly with the surrounding tissues. Hence the biological effects of radon result from inhalation of its solid, short-lived, alpha-emitting decay products (principally polonium-218 and polonium-214), which deposit on the lining of the bronchial airway. The dose to internal organs from radon that is ingested in drinking water, even at high concentrations, is extremely low.

In humans and laboratory animals, the risk of lung cancer increases with increasing exposure to inhaled radon and its short-lived decay products. In underground miners the risk appears to increase in proportion to the total cumulative dose to cells lining the airway, and to be about two times higher in smokers than in nonsmokers. The risk from exposure to residential indoor radon at a given concentration, although yet to be defined precisely, is generally estimated to be comparable to the corresponding risk in miners. As a result, radon is thought to be the single most important cause of lung cancer in nonsmokers and to cause 10 to 15 percent of all lung cancers, or 15,000 to 20,000 lung cancer deaths each year in the United States. Hence, the U.S. Environmental Protection Agency has recommended that indoor radon concentrations not be allowed to exceed 4 pCi/L, a concentration that might be expected to double the risk of lung cancer if inhaled throughout an average lifespan.

Methods for reducing the concentration of radon and its decay products in indoor air include ventilation; air filtration; sealing of cracks in basement floors and walls; installation of a subslab exhaust system beneath the basement floor; and remediation of heavily contaminated groundwater or well water that is used for drinking, bathing, or showering. Radon can be measured in the home with a number of relatively inexpensive devices, which are available from some state and local governments as well as private firms. Pertinent information can generally be obtained from the local state radiation or the Environmental Protection Agency office.

Bibliography

Eisenbud, M., and Gesell, T. (1997). Environmental Radioactivity: From Natural, Industrial, and Military Sources, 4th edition. San Diego, CA: Academic Press.

Harley, N. (2000). "Radon and Daughters." In Environmental Toxicants, 2nd edition, ed. M. Lippmann. New York: John Wiley and Sons.

National Academy of Sciences/National Research Council (1998). Health Effects of Exposure to Radon. Washington, DC: National Academy Press.

U.S. Geological Survey. The Geology of Radon. Available at http://energy.ct.us.gov/radonhome.html.

— ARTHUR C. UPTON


 
Britannica Concise Encyclopedia: radon

Chemical element, chemical symbol Rn, atomic number 86. The heaviest noble gas, it is colourless, odourless, tasteless, radioactive (see radioactivity), and almost completely unreactive (forming compounds only with fluorine). It is rare in nature because all its isotopes are short-lived and because radium, its source, is scarce. Radon seeps from certain soils and rocks (such as granite) into the atmosphere and can accumulate in poorly ventilated spaces near ground level, including house basements; in some regions of the world the use of such spaces is believed to increase the risk of lung cancer more than any other common factor except smoking. Radon is used in radiotherapy, radiography, and research.

For more information on radon, visit Britannica.com.

 
Architecture: radon

A gaseous emanation produced by the radioactive decay of radium, given off by some soils and rocks; it may collect and constitute a health hazard in buildings with poor ventilation.

 
Columbia Encyclopedia: radon
(rā'dŏn) , gaseous radioactive chemical element; symbol Rn; at. no. 86; mass no. of most stable isotope 222; m.p. about −71°C; b.p. −61.8°C; density 9.73 grams per liter at STP; valence usually 0. Radon is colorless and the most dense gas known. Chemically unreactive, it is classed as an inert gas in Group 18 of the periodic table. Synthesis of radon fluoride has been reported. Radon is highly radioactive and has a short half-life. The chief use of radon is in the treatment of cancer by radiotherapy. It has also found some use (mixed with beryllium) as a neutron source. All naturally occurring radon decays by the emission of alpha particles. The element is found in some spring waters, in streams, and to a very limited extent (about 1 part in 1021) in air. Radon is produced by the disintegration of its precursors in minerals, from which it diffuses in small amounts. In homes and other buildings in some areas of the U.S., radon produced by the radioactive decay of uranium-238 present in soil and rock can reach levels regarded as dangerous, but the seriousness of the problem is unclear. Twenty isotopes of radon are known, but only three occur naturally. Radon-222 (half-life 3.82 days) is produced by the decay of radium-226. Radon-220 (half-life 55 sec), also called thoron, is produced in the decay series of thorium-232. Radon-219 (half-life 4 sec), also called actinon, is produced in the decay series of uranium-235 (actinouranium). Ernest Rutherford discovered thoron in 1899. F. O. Dorn discovered radon-222 in 1900 and called it radium emanation. In about 1902, F. O. Giesel discovered actinon. In 1908 William Ramsay and R. W. Whytlaw-Gray isolated the element, which they called niton, and studied its physical properties. The name radon was adopted in the 1920s to refer to all the isotopes of the element, although the name emanation and symbol Em are sometimes used.

 
Science Dictionary: radon
(ray-don)

A colorless, odorless, radioactive gas that is produced by the decay of radium in the soil.

  • Radon seeping through the ground and into buildings is a major source of indoor air pollution and may represent a significant risk for lung cancer.

    •  
    Veterinary Dictionary: radon

    A chemical element, atomic number 86, atomic weight 222, symbol Rn. Radon is a colorless, gaseous, radioactive element produced by the disintegration of radium.

     
    Wikipedia: radon


    86 astatine ← radon → francium
    Xe
    ↑
    Rn
    ↓
    Uuo
    Rn-TableImage.png
    General
    Name, Symbol, Number radon, Rn, 86
    Chemical series noble gases
    Group, Period, Block 18, 6, p
    Appearance colorless
    Standard atomic weight (222)  g·mol−1
    Electron configuration [Xe] 4f14 5d10 6s2 6p6
    Electrons per shell 2, 8, 18, 32, 18, 8
    Physical properties
    Phase gas
    Density (0 °C, 101.325 kPa)
    9.73 g/L
    Melting point 202 K
    (−71.15 °C, −96 °F)
    Boiling point 211.3 K
    (−61.85 °C, −79.1 °F)
    Critical point 377 K, 6.28 MPa
    Heat of fusion 3.247  kJ·mol−1
    Heat of vaporization 18.10  kJ·mol−1
    Heat capacity (25 °C) 20.786  J·mol−1·K−1
    Vapor pressure
    P(Pa) 1 10 100 1 k 10 k 100 k
    at T(K) 110 121 134 152 176 211
    Atomic properties
    Crystal structure cubic face centered
    Oxidation states 0
    Electronegativity no data (scale Pauling)
    Ionization energies 1st: 1037 kJ/mol
    Atomic radius (calc.) 120  pm
    Covalent radius 145  pm
    Miscellaneous
    Magnetic ordering non-magnetic
    Thermal conductivity (300 K) 3.61 m W·m−1·K−1
    CAS registry number 10043-92-2
    Selected isotopes
    Main article: Isotopes of radon
    iso NA half-life DM DE (MeV) DP
    211Rn syn 14.6 h Epsilon 2.892 211At
    Alpha 5.965 207Po
    222Rn 100% 3.824 d Alpha 5.590 218Po
    References

    Radon (IPA: /ˈreɪdɒn/) is a chemical element that has the symbol Rn and atomic number 86. Radon is a radioactive noble gas that is formed by the decay of radium. It is one of the heaviest gases and is considered to be a health hazard. The most stable isotope is 222Rn which has a half-life of 3.8 days and is used in radiotherapy. Radon is a significant contaminant that affects indoor air quality worldwide. Radon gas from natural sources can accumulate in buildings and reportedly causes 21,000 lung cancer deaths per year in the United States alone.[1]

    Notable characteristics

    Essentially chemically inert but radioactive, radon is the heaviest noble gas and one of the heaviest gases at room temperature. At standard temperature and pressure radon is a colorless gas, but when it is cooled below its freezing point (202 K ; −71 °C ; −96 °F) it has a brilliant phosphorescence which turns yellow as the temperature is lowered, and becomes orange-red at the temperatures air liquefies (below 93 K ; −180 °C).

    Natural radon concentrations in Earth's atmosphere are so low that radon-rich water in contact with the atmosphere will continually lose radon by volatilization. Hence, ground water has a higher concentration of 222Rn than surface water, because it is continuously produced by radioactive decay of 226Ra present in rocks. Likewise, the saturated zone of a soil frequently has a higher radon content than the unsaturated zone because of diffusional losses to the atmosphere.

    History

    Radon (named after radium) was discovered in 1900 by Friedrich Ernst Dorn, who called it radium emanation. In 1908 William Ramsay and Robert Whytlaw-Gray, named it niton (Latin nitens meaning "shining"; symbol Nt) and isolated it, determined its density, and determined that it was the heaviest known gas. It has been called "radon" since 1923.

    The first major studies of the health concern occurred in the context of uranium mining, first in the Joachimsthal region of Bohemia and then in the Southwestern United States during the early Cold War. Because radon is a product of uranium, uranium mines have high concentrations of radon and its highly radioactive daughter products. Many Native Americans, Mormons, and other miners in the Four Corners region contracted lung cancer and other pathologies as a result of high levels of exposure to radon gas while mining uranium for the Atomic Energy Commission in the mid-1950s. Safety standards instituted required expensive ventilation and as such were not widely implemented or policed.

    The danger of radon exposure in dwellings was discovered in 1984 with the case of Stanley Watras, an employee at the Limerick nuclear power plant in Pennsylvania. Watras set off the radiation alarms on his way into work for two weeks straight while authorities searched for the source of the contamination. They were shocked to find that the source was astonishingly high levels of radon, around 100,000 Bq/m3 (2,700 pCi/L), in his house's basement and it was not related to the nuclear plant. The risks associated with living in his house were estimated to be equivalent to smoking 135 packs of cigarettes every day. Following this event, which was highly publicized, national radon safety standards were set, and radon detection and ventilation became a standard homeowner concern.

    Radon is the second most frequent cause of lung cancer, after cigarette smoking, and radon-induced lung cancer is thought to be the 6th leading cause of cancer death overall.[2][3]

    Occurrence

    On average, there is one atom of radon in 1 x 1021 molecules of air.[citation needed] Radon can be found in some spring waters and hot springs.[4] The towns of Boulder, Montana, Misasa, Japan, and Bad Kreuznach, Germany boast radium-rich springs which emit radon.

    Radon emanates naturally from the ground all over the world, particularly in regions with soils containing granite or shale. However, not all granitic regions are prone to high emissions of radon. Depending on how houses are built and ventilated, radon may accumulate in basements and dwellings. The highest average radon concentrations in counties in the U.S. are found in Iowa and in the Appalachian Mountains areas in southeastern Pennsylvania. [5]

    Radon, along with other noble gases krypton and xenon, is also produced during the operation of nuclear power plants. A small fraction of it leaks out of the fuel, through the cladding and into the cooling water, from which it is scavenged. It is then routed to a holding tank where it remains for a large number of half-lives. It is finally purged to the open air through a tall stack which is carefully monitored for radiation level.

    The European Union recommends that action should be taken starting from concentrations of 400 Bq/m3 (11 pCi/L) for old houses and 200 Bq/m3 (5 pCi/L) for new ones. After publication of the North American and European Pooling Studies, Health Canada has proposed a new guideline that lowers their action level from 800 to 200 Bq/m3 (22 to 5 pCi/L).[6] The United States Environmental Protection Agency (EPA) strongly recommends action for any house with a concentration higher than 148 Bq/m3 (4 pCi/L)[7], and encourages action starting at 74 Bq/m3 (2 pCi/L). EPA radon risk level tables including comparisons to other risks encountered in life are available in their citizen's guide.[8] Nearly one in 15 homes in the U.S. has a high level of indoor radon according to their statistics. The U.S. Surgeon General and EPA recommend all homes be tested for radon.

    Radon emitted from the ground has been shown to accumulate in the air if there is a meteorological inversion and little wind.[9]

    Compounds

    Some experiments indicate that fluorine can react with radon and form radon fluoride. Radon clathrates have also been reported.

    Isotopes

    Main article: isotopes of radon

    There are twenty known isotopes of radon. The most stable isotope is 222Rn, which is a decay product (daughter product) of 226Ra, has a half-life of 3.823 days and emits alpha particles. 220Rn is a natural decay product of thorium and is called “thoron.” It has a half-life of 55.6 seconds and also emits alpha radiation. 219Rn is derived from actinium, is called “actinon,” is an alpha emitter and has a half-life of 3.96 seconds.

    The full decay series of 238U which produces natural radon is as follows (with half-lives):

    238U (4.5 x 109 yr), 234Th (24.1 days), 234Pa (1.18 min), 234U (250,000 yr), 230Th (75,000 yr), 226Ra (1,600 yr), 222Rn (3.82 days), 218Po (3.1 min), 214Pb (26.8 min), 214Bi (19.7 min), 214Po (164 µs), 210Pb (22.3 yr), 210Bi (5.01 days), 210Po (138 days), 206Pb (stable).

    Applications

    Radon therapy

    In the United States and Europe there are a few "radon spas," where people sit for minutes or hours in a high-radon atmosphere in the belief that airborne radiation will invigorate or energize them. However, there is no scientific evidence for this belief, nor any known biological mechanism by which such an effect could occur. In addition, it conflicts with the internationally recognized standard that there is no safe threshold for radiation exposure and that exposure should be limited to that "as low as reasonably achievable" (ALARA).

    Radioactive water baths have been applied since 1906 in Jáchymov, Czech Republic, but even before radon discovery they were used in Bad Gastein, Austria. Hot radium-rich spring releasing radon is also used in traditional Japanese onsen in Misasa, Tottori prefecture. Drinking therapy is applied in Bad Brambach, Germany. Inhalation therapy is carried out in Gasteiner-Heilstollen, Austria, in Kowary, Poland and in Boulder, Montana, United States.

    Hydrologic studies

    Because of radon's rapid loss to air and comparatively rapid decay, radon is used in hydrologic research that studies the interaction between ground water and streams. Any significant concentration of radon in a stream is a good indicator that there are local inputs of ground water.

    Geologic studies

    Some researchers have looked at elevated soil-gas radon concentrations, or rapid changes in soil or groundwater radon concentrations, as a predictor for earthquakes. Results have been generally unconvincing but may ultimately prove to have some limited use in specific locations.

    Radon soil-concentration has been used in an experimental way to map buried close-subsurface geological faults, because concentrations are generally higher over the faults. Similarly it has found some limited use in geothermal prospecting.

    Atmospheric studies

    Radon emanation from the soil varies with soil type and with surface uranium content, so outdoor radon concentrations can be used to track air masses to a limited degree. This fact has been put to use by some atmospheric scientists.

    Radon is a known pollutant emitted from geothermal power stations, though it disperses rapidly, and no radiological hazard has been demonstrated in various investigations. The trend in geothermal plants is to reinject all emissions by pumping deep underground, and this seems likely to ultimately decrease such radon hazards further. Radon is also used in dating of oil contained soil because radon have a high affinity of oil like substance.

    Health effects and epidemiology

    The general effects of radon to the human body are caused by its radioactivity and consequent risk of radiation-induced cancer. As an inert gas, radon has a low solubility in body fluids which lead to a uniform distribution of the gas throughout the body.[10] Radon gas and its solid decay products are carcinogens. The greatest health risks come from exposure to the inhaled solid radon gas decay products that are produced during the radioactive decay of radon gas. Two of these decay products, polonium-218 and 214, present a significant radiologic hazard.[11] Once the radioactive decay products are inhaled into the lung, they undergo further radioactive decay, releasing small bursts of energy in the form of alpha particles that can either cause DNA breaks or create free radicals.[11]

    Based on studies carried out by the National Academy of Sciences in the United States, radon is the second most common cause of lung cancer after cigarette smoking, accounting for 15,000 to 22,000 cancer deaths per year in the U.S.[12] The Surgeon General of the United States has reported that over 20,000 Americans die each year of radon-related lung cancer.[13] The United States Environmental Protection Agency (EPA) recommends homes be fixed if an occupant's long-term exposure will average 4 picocuries per liter (pCi/L) (148 Bq m−3) or higher.[14]

    The most elaborate case-control epidemiologic radon study performed by R. William Field and colleagues demonstrated a 50% increased lung cancer risk with prolonged radon exposure at the EPA's action level of 4 pCi/L.[15] Iowa has the highest average radon concentrations in the nation and a very stable population which added to the strength of the study. Pooled epidemiologic radon studies[16][17] have also shown an increased lung cancer risk from radon below the EPA's action level of 4 pCi/L.

    It is unknown whether radon causes other types of cancer, but recent studies suggest a need for further studies to assess the relationship between radon and leukemia.[18][19]

    Testing and mitigation

    ASTM E-2121 is a standard for reducing radon in homes as far as practicable below 4 picocuries per liter (pCi/L) in indoor air.[20][21]

    Radon test kits are commercially available. The kit includes a collector that the user hangs in the lowest livable floor of the house for 2 to 7 days. The user then sends the collector to a laboratory for analysis. The National Environmental Health Association provides a list of radon measurement professionals.[22] Long term kits, taking collections for up to one year, are also available. An open land test kit can test radon emissions from the land before construction begins. The EPA and the National Environmental Health Association have identified 15 types of radon testing.[23] A Lucas cell is one type of device.

    Radon levels fluctuate naturally. An initial test might not be an accurate assessment of your home's average radon level. Transient weather can affect short term measurements.[24] Therefore, a high result (over 4 pc/l) justifies repeating the test before undertaking more expensive abatement projects. Measurements between 4 and 10 pc/l warrant a long term radon test. Measurements over 10 pc/l warrant only another short term test so that abatement measures are not unduly delayed. Purchasers of real estate are advised to delay or decline a purchase if the seller has not successfully abated radon to 4 pc/l or less.

    The National Environmental Health Association administers a voluntary National Radon Proficiency Program for radon professionals consisting of individuals and companies wanting to take training courses and examinations to demonstrate their competency.[25] A list of mitigation service providers is available.[26] Indoor radon can be mitigated by sealing basement foundations, water drainage, or by sub-slab de-pressurization. In severe cases, mitigation can use air pipes and fans to exhaust sub-slab air to the outside. Indoor ventilation systems are more effective, but exterior ventilation can be cost-effective in some cases. Modern construction that conserves energy by making homes air tight exacerbates the risks of radon exposure if radon is present in the home. Older homes with more porous construction are more likely to vent radon naturally. Ventilation systems can be combined with a heat exchanger to recover energy in the process of exchanging air with the outside. Homes built on a crawl space can benefit from a radon collector installed under a radon barrier (a sheet of plastic that covers the crawl space).


    Notes

    1. ^ http://www.epa.gov/radon/pubs/citguide.html
    2. ^ S. Darby, D. Hill, R. Doll (2001). "Radon: A likely carcinogen at all exposures". Annals of Oncology 12 (10): 27. DOI:10.1023/A:1012518223463. 
    3. ^ http://www.cheec.uiowa.edu/misc/Webtop10.ppt
    4. ^ Radon Occurrence and Health Risk, R. William Field, Department of Occupational and Environmental Health, University of Iowa.
    5. ^ http://eetd.lbl.gov/IEP/high-radon/USgm.htm
    6. ^ It's Your Health - Radon, Health Canada
    7. ^ Radiation information: radon. United States Environmental Protection Agency (Oct 2006). Retrieved on 2007-05-25.
    8. ^ A Citizen's Guide to Radon: The Guide to Protecting Yourself and Your Family from Radon, United States Environmental Protection Agency.
    9. ^ Daniel J. Steck, R. William Field, and Charles F. Lynch, "Exposure to Atmospheric Radon", Environmental Health Perspectives, Volume 107, Number 2, February 1999. Online version
    10. ^ Lindgren, 1989
    11. ^ a b Field, R. William (1999). Radon Occurrence and Health Risk (PDF). Retrieved on 2007-08-17.
    12. ^ National Cancer Institute (2004-07-13). Radon and Cancer: Questions and Answers. Retrieved on 2007-08-17.
    13. ^ Surgeon General Releases National Health Advisory On Radon (2005-01-13). Retrieved on 2007-08-17.
    14. ^ EPA (2007-08-08). United States Environmental Protection Agency: Radon. Retrieved on 2007-08-17.
    15. ^ Field, R. W.; et al. (2000). "Residential radon gas exposure and lung cancer: The Iowa radon lung cancer study" (PDF). American Journal of Epidemiology 151 (11): 1091-1102. PMID 10873134. 
    16. ^ University of Iowa News Release (2006-05-05). Journal on Landmark Radon Exposure Studies Co-edited By UI Researcher. Retrieved on 2007-08-17.
    17. ^ Krewski, D.; et al.. "Residential radon and risk of lung cancer: A combined analysis of 7 North American case-control studies" (PDF). Epidemiology 16 (2): 137-45. DOI:10.1097/01.ede.0000152522.80261.e3. 
    18. ^ Smith, B. J.; Zhang, L. & Field, W.R. (2007). "Iowa radon leukaemia study: a hierarchical population risk model for spatially correlated exposure measured with error.". Statistical Medicine E-published. PMID 17373673. 
    19. ^ Rericha, V; Kulich M, Rericha R, Shore DL, Sandler DP (2007). "Incidence of leukemia, lymphoma, and multiple myeloma in Czech uranium miners: a case-cohort study". Environmental Health Perspectives 115 (4): A184-5. PMID 16759978. 
    20. ^ http://www.epa.gov/iaq/radon/pubs/mitstds.html
    21. ^ http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/E2121.htm?L+mystore+xyan5063
    22. ^ http://www.radongas.org/Description_of_Radon_Measurement_Service.html
    23. ^ http://www.radongas.org/device.htm
    24. ^ http://www.radon.com/radon/mitigation.html
    25. ^ http://www.radongas.org/
    26. ^ http://www.radongas.org/Description_of_Radon_Mitigation_Services.html

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    Translations: Translations for: Radon

    Dansk (Danish)
    n. - [kem.] radon

    Nederlands (Dutch)
    radon

    Français (French)
    n. - radon

    Deutsch (German)
    n. - (Chem.) Radon

    Ελληνική (Greek)
    n. - (χημ.) ραδόνιο

    Italiano (Italian)
    radon

    Português (Portuguese)
    n. - rádon (m) (Quim.)

    Русский (Russian)
    радон

    Español (Spanish)
    n. - radón

    Svenska (Swedish)
    n. - (kem) radon

    中文（简体） (Chinese (Simplified))
    氡

    中文（繁體） (Chinese (Traditional))
    n. - 氡

    한국어 (Korean)
    n. - 라돈(라듐에서 나오는 방사성 원소)

    日本語 (Japanese)
    n. - ラドン

    العربيه (Arabic)
    ‏(الاسم) عنصر غازي إشعاعي‏

    עברית (Hebrew)
    n. - ‮רדון (יסוד גזי, NR, מס' אטומי 68)‬

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    Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
    Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.  Read more
    Real Estate Dictionary. Dictionary of Real Estate Terms. Copyright © 2004 by Barron's Educational Series, Inc. All rights reserved.  Read more
    Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
    Encyclopedia of Public Health. Encyclopedia of Public Health. Copyright © 2002 by The Gale Group, Inc. All rights reserved.  Read more
    Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
    Architecture. McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc. All rights reserved.  Read more
    Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/  Read more
    Science Dictionary. The New Dictionary of Cultural Literacy, Third Edition Edited by E.D. Hirsch, Jr., Joseph F. Kett, and James Trefil. Copyright © 2002 by Houghton Mifflin Company. Published by Houghton Mifflin. All rights reserved.  Read more
    Veterinary Dictionary. The Veterinary Dictionary. Copyright © 2007 by Elsevier. All rights reserved.  Read more
    Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Radon".  Read more
    Translations. Copyright © 2007, WizCom Technologies Ltd. All rights reserved.  Read more

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