Radon is one of the densest substances that remains a gas under normal conditions. It is also the only gas under normal conditions that only has radioactive isotopes, and is considered a health hazard due to its radioactivity. Intense radioactivity has also hindered chemical studies of radon and only a few compounds are known.
Radon is formed as one intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead. Thorium and uranium are the two most common radioactive elements on earth; they have been around since the earth was formed. Their naturally occurring isotopes have very long half-lives, on the order of billions of years.
Thorium and uranium, their decay product radium, and its decay product radon, will therefore continue to occur for tens of millions of years at almost the same concentrations as they do now. As radon itself decays, it produces new radioactive elements called radon progeny (formerly called daughters) or decay products. Unlike the gaseous radon itself, radon progeny are solids and stick to surfaces, such as dust particles in the air. If such contaminated dust is inhaled, these particles can stick to the airways of the lung and increase the risk of developing lung cancer.
Unlike all the other intermediate elements in the aforementioned decay chains, radon is gaseous and easily inhaled. Thus, naturally-occurring radon is responsible for the majority of the public exposure to ionizing radiation. It is often the single largest contributor to an individual's background radiation dose, and is the most variable from location to location. Despite its short lifetime, some radon gas from natural sources can accumulate to far higher than normal concentrations in buildings, especially in low areas such as basements and crawl spaces due to its density. It can also occur in water where the water comes from a ground source -e.g. in some spring waters and hot springs.
Epidemiological studies have shown a clear link between breathing high concentrations of radon and incidence of lung cancer. Thus, radon is considered a significant contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency, radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States. About 2,900 of these deaths occur among people who have never smoked.
Radon. Radon is a chemical element with symbol rn and atomic number 86.
It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as an indirect decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days. Radon is one of the densest substances that remains a gas under normal conditions. It is also the only gas under normal conditions that only has radioactive isotopes, and is considered a health hazard due to its radioactivity. Intense radioactivity has also hindered chemical studies of radon and only a few compounds are known. Radon is formed as one intermediate step in the normal radioactive decay chains, through which thorium and uranium slowly decay into lead. Epidemiological studies have shown a clear link between breathing high concentrations of radon and incidence of lung cancer. Characteristics Emission spectrum of radon, photographed by Ernest Rutherford in 1908.
Physical properties Chemical properties
History and etymology. Occurrence. Applications. Health effects. Radiohalo. Radiohalos or pleochroic halos are microscopic, spherical shells of discolouration within minerals such as biotite that occur in granite and other igneous rocks.
The shells are zones of radiation damage caused by the inclusion of minute radioactive crystals within the host crystal structure. The inclusions are typically zircon, apatite, or titanite which can accommodate uranium or thorium within their crystal structures (Faure 1986). One explanation is that the discolouration is caused by alpha particles emitted by the nuclei; the radius of the concentric shells are proportional to the particle's energy (Henderson & Bateson 1934). The phenomenon of radiohalos has been known to geologists since the early part of the 20th century, but wider interest has been prompted by the claims of creationist Robert V. Gentry that radiohalos in biotite are evidence for a young earth (Gentry 1992). Production Giant radiohaloes caused some excitement when Robert V. Controversy Robert V. Radiation Exposure Compensation Act. Areas covered by the Radiation Exposure Compensation Program The United States Radiation Exposure Compensation Act (RECA) is a federal statute providing for the monetary compensation of people, including atomic veterans, who contracted cancer and a number of other specified diseases as a direct result of their exposure to atmospheric nuclear testing undertaken by the United States during the Cold War, or their exposure to radon gas and other radioactive isotopes while undertaking uranium mining, milling or the transportation of ore.
The Act provides the following remunerations: $50,000 to individuals residing or working "downwind" of the Nevada Test Site$75,000 for workers participating in atmospheric nuclear weapons tests$100,000 for uranium miners, millers, and ore transporters In all cases there are additional requirements which must be satisfied (proof of exposure, establishment of duration of employment, establishment of certain medical conditions, etc.). Origins Eligibility International Radon Project. The International Radon Project (IRP) is a World Health Organization initiative to reduce the lung cancer risk around the world.
The IRP released their guidance to member countries in September 2009.