Radon is a chemical element with symbol Rn and atomic number 86. Radon is a colorless, odorless, tasteless, naturally occurring, radioactive noble gas that is formed from the decay of radium. It is one of the heaviest substances that remains a gas under normal conditions and is considered to be a health hazard. The most stable isotope,Rn, has a half-life of 3.8 days. While having been less studied by chemists due to its high radioactivity, there are a few known compounds of this generally unreactive element.
Radon is formed from the normal radioactive decay of uranium. Uranium has been around since the earth was formed and has a very long half-life (4.5 billion years), which is the amount of time required for one-half of uranium to break down. Uranium, radium, and thus radon, will continue to exist indefinitely at about the same levels as they do now.
Radon is responsible for the majority of the mean public exposition to ionizing radiations, it is often the single largest contributor to an individual's background radiation dose, and is certainly the most variable from location to location. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as basements.
Radon can be found in some spring waters and hot springs.
Breathing high concentrations of radon can cause lung cancer. Thus, radon is considered as a significant contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency, radon could be the second most frequent cause of lung cancer, after cigarette smoking; and radon-induced lung cancer the 6th leading cause of cancer death overall, causing 21,000 lung cancer deaths per year in the United States.
Radon is a decay product of uranium, which is relatively common in the Earth's crust, but generally concentrated in ore-bearing rocks scattered around the world. Every square mile of surface soil, to a depth of 6 inches, contains approximately 1 gram of radium, which releases radon in small amounts to the atmosphere. On a global scale, it is estimated that 2,400 million curies of radon are released from soil annually.
Medical
Arthritis---It has been said that exposure to radon gas mitigates auto-immune diseases such as arthritis. As a result, in the late 20th century and early 21st century, some "health mines" were established in Basin, Montana which attracted people seeking relief from health problems such as arthritis through limited exposure to radioactive mine water and radon. The practice is controversial because of the "well-documented ill effects of high-dose radiation on the body."
Bathing---Radioactive water baths have been applied since 1906 in Czech Republic, but even before radon discovery they were used in Austria. Radium-rich springs are also used in traditional Japanese onsen prefecture. Drinking therapy is applied in Germany. Inhalation therapy is carried out in Austria, Kowary, Poland, Boulder, Montana, United States. In the United States and Europe there are several "radon spas," where people sit for minutes or hours in a high-radon atmosphere in the belief that low doses of radiation will invigorate or energize them.
Medical Radiography---The radon gas which is used as a cancer treatment in medicine is obtained from the decay of a radium chloride source. In the past, radium and radon have both been used for X-ray medical radiography, but they have fallen out of use as they are radiotoxic alpha radiation emitters which are expensive and have been replaced with iridium-192 and cobalt-60since they are far better photon sources.
Radiotherapy---Radon has been produced commercially for use in radiation therapy, but for the most part has been replaced by radionuclides made in accelerators and nuclear reactors.
Radon has been used in implantable seeds, made of gold or glass, primarily used to treat cancers. The gold seeds were produced by filling a long tube with radon pumped from a radium source, the tube being then divided into short sections by crimping and cutting. The gold layer keeps the radon within, and filters out the alpha and beta radiations, while allowing the gamma rays to escape (which kill the diseased tissue).The gamma rays are produced by radon and the first short-lived elements of its Decay chain.
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