Radon is a chemical element with the symbols Rn and atomic number 86. It is a noble gas that is odorlessly radioactive, colorless, odorless, tasteless. This occurs naturally in minute amounts as a further step in the normal radioactive decay chain through which thorium and uranium slowly decay into lead and other short-lived radioactive elements; radon itself is a direct product of radium decay. The most stable isotope, 222 Rn, has a half-life of only 3.8 days, making radon one of the rarest elements because it decays very quickly. However, since thorium and uranium are the two most common radioactive elements on Earth, and they have three isotopes with very long half-lives, in the order of several billions of years, radon will be present on Earth far into the future despite a short half-life like that continually generated. Radon decay produces many short-lived nuclides known as radon children, ending in stable isotopes of lead.
Unlike all other intermediate elements in the aforementioned decay chains, radon, under normal conditions, is gas-shaped and readily inhaled. Radon gas is considered a health hazard. This is often the largest contributor to individual background radiation doses, but due to geological differences at the local level, the degree of hazard radon-gas differs from one location to another. Despite its short lifespan, radon gas from natural sources, such as uranium-containing minerals, can accumulate in buildings, especially, because of its high density, in low areas such as basements and crawl spaces. Radon can also occur in groundwater - for example, in some springs and hot springs.
Epidemiological studies have shown a clear association between high concentrations of radon respiration and the incidence of lung cancer. Radon is a contaminant that affects indoor air quality throughout the world. According to the US Environmental Protection Agency, radon is the second most frequent cause of lung cancer, after smoking, causing 21,000 deaths from lung cancer per year in the United States. About 2,900 of these deaths occur among people who have never smoked. While radon is the second most frequent cause of lung cancer, it is the number one cause among non-smokers, according to EPA estimates. When radon itself decays, it produces decay products, which are other radioactive elements called radonic children (also known as radon progeny). Unlike the radon gas itself, the radon daughter is a solid and attached to the surface, just like the dust particles in the air. If the contaminated dust is inhaled, these particles can also cause lung cancer.
Video Radon
Characteristics
Physical properties
Radon is a gas that is colorless, odorless, and tasteless and therefore can not be detected by the human senses alone. At standard temperature and pressure, radon forms monoatomic gas with a density of 9.73 kg/m 3 , about 8 times the Earth's atmospheric density at sea level, 1,217 kg/m 3 . Radon is one of the densest gas at room temperature and is the densest gas of the noble. Although not colored at standard temperature and pressure, when cooled below freezing 202Ã, Â ° K (-71Ã, Â ° C; -96Ã, Â ° F), radon emits a brilliant radioluminescence that changes from yellow to orange-red when temperature decreased. After condensation, radon shines because of the strong radiation it produces. Radon is slightly soluble in water, but more soluble than lighter noble gases. Radon is more soluble in organic liquids than in water.
Chemical Properties
Being a noble gas, radon is chemically not very reactive. However, the 3.3-day half-day radon-222 makes it useful in physics as a natural tracer. Because radon is a gas in standard conditions, unlike his parents, he can easily be taken from them for research.
Radon is a member of zero-valency element called a noble gas. It is inactive for the most common chemical reactions, such as combustion, because the outer valence skin contains eight electrons. This results in a stable minimum energy configuration in which the outer electrons are tightly bound. 1037 kJ/mol is required to extract one electron from its shell (also known as first ionization energy). In accordance with the periodic trend, radon has a lower electronegativity than the one previous period element, xenon, and therefore more reactive. Initial studies concluded that radon hydrate stability should have the same sequence as chlorine hydrate ( Cl
2 ) or sulfur dioxide ( SO
2 ), and significantly higher than hydrogen sulfide hydrate stability ( H
2 S ).
Because of their costs and radioactivity, experimental chemical research is rarely done with radon, and as a result very few reported radon compounds, all fluoride or oxide. Radon can be oxidized by powerful oxidizing agents such as fluorine, thereby forming a radon of difluoride. It decomposes back to its elements at temperatures above 250 Â ° C, and is reduced by water into radon gas and hydrogen fluoride: it can also be reduced back to its elements by hydrogen gas. It has low volatility and is considered RnF
2 . Because of the short radon beak time and radioactivity of the compounds, it is not possible to study the compound in detail. The theoretical study on this molecule predicts that it must have an Rn-F bond distance of 2.08Ã, ÃÆ'..., and that the thermodynamic compound is more stable and less volatile than its lighter counterpart XeF
2 . The octahedral molecule RnF
6 enthalpy of formation lower than difluoride. The higher the fluoride, RnF 4 and RnF 6 have been claimed, and calculated stable, but it is doubtful whether they have not been synthesized. Ions [RnF] are believed to be formed by the following reactions:
- Rn (g) 2 [O
2< br> 6 ] -
(s) -> [RnF]
[Sb
2 F
11 ] - /span> (s) 2 O
2 (g)
For this reason, antimony pentafluoride along with chlorine trifluoride and N 2 F 2 Sb 2 F 11 have been considered for removal of radon gas in uranium mines due to the formation of radon-fluorine compounds. The presence of RnF 2 allows for the safer handling of radion parent radium as fluoride, since alpha radiation from 226 Ra is not strong enough to cause radiolysis from Ra- strong. F bonds; so 226 RaF 2 decays to form involatile 222 RnF 2 . In addition, the salt of [RnF] cation with anions SbF -
6 , TaF < span> -
6 , and BiF -
6 is known. Radon is also oxidized by dioxide dioxide into RnF 2 at -100Ã, Â ° C.
Radon oxide are some of the other reported radon compounds; only trioxide (RnO 3 ) has been confirmed. Higher fluids may have been observed in experiments where products not containing unknown radon are distilled together with xenon hexafluoride, and possibly in the production of radon trioxide: this is probably RnF 4 , RnF 6 , or both. Extrapolation under the noble gas group will also suggest the possibility of the presence of RnO, RnO 2 , and RnOF 4 , as well as the chemically stable first chloride that is chemically stable, RnCl 2 and RnCl 4 , but nothing has been found yet. RnCO carbonyl radon has been predicted stable and has a linear molecular geometry. Molecules Rn
2 and RnXe found to be significantly stabilized by spin-orbit coupling. Radon confined inside fullerenes has been proposed as a cure for tumors. Despite the presence of the compound Xe (VIII), no Rn (VIII) has been claimed to exist; RnF 8 must be very chemically unstable (XeF 8 thermodynamically unstable). It is estimated that the most stable Rn (VIII) compound is barium perradonate (Ba 2 RnO 6 ), analogous to barium perxenate. The instability of Rn (VIII) is due to the relativistic stabilization of the 6s shell, also known as the inert pair effect.
Radon reacts with liquid halogen fluoride ClF, ClF 3 , ClF 5 , BrF 3 , Brf 5 , and IF 7 to form RnF 2 . In a solution of halogen fluoride, radon is labile and exists as RnF and Rn 2 cations; addition of fluoride anion results in the formation of complex RnF - 3 and RnF 2 - 4 , parallel to the chemistry of beryllium (II) and aluminum (III). The standard electrode potential of the Rn 2 /Rn pair has been estimated as 2.0 V, although there is no evidence for the formation of stable radon ions or compounds in an aqueous solution.
Isotope
Radon does not have stable isotopes. Thirty-seven radioactive isotopes have been characterized, with atomic masses ranging from 193 to 229. The most stable isotope is 222 Rn, which is a decay product 226 Ra, a product decay < soup> 238 U. A number of traces of isotopes (very unstable) 218 Rn also among girls 222 Rn.
Three other radon isotopes have a half-life of more than one hour: 211 Rn, 210 Rn and 224 Rn. Isotope 220 Rn is the natural decay product of the most stable thorium isotope ( 232 Th), and is usually referred to as thoron. It has a half-life of 55.6 seconds and also emits alpha radiation. Similarly, 219 Rn is derived from the most stable acrylic isotope ( 227 Ac) - named "actinon" - and is an alpha emitter with a half-life of 3.96 seconds. No isotope radon occurs significantly in the decay series of neptunium ( 237 Np), although trace amounts of the highly unstable Rn <$> isotope are generated.
Daughters
222 Rn is included in the radium decay chain and uranium-238, and has a half-life of 3.8235 days. The first four products (excluding marginal decay schemes) are very short-lived, which means that appropriate disintegration is an indication of the initial radon distribution. Decay it in the following order:
- 222 Rn, 3.82 days, alpha rot to...
- 218 Po, 3.10 min, alpha decayed to...
- 214 Pb, 26.8 minutes, beta rot to...
- 214 Bi, 19.9 minutes, beta rot to...
- 214 Po, 0.1643Ã, ms, alpha decay to...
- 210 Pb, which has a longer half-life of 22.3 years, beta rot to...
- 210 Bi, 5,013 days, beta rot to...
- 210 Po, 138,376 days, alpha rot to...
- 206 Pb, stable.
The radon equilibrium factor is the ratio between the activity of all short-run radon progeny (which is responsible for most of the biological effects of radon), and the activity to be in equilibrium with the mother radon.
If the closed volume is constantly supplied with radon, the short-lived concentration of isotopes will increase until equilibrium is reached whereby the decay rate of each decay product will be equal to the radon itself. The equilibrium factor is 1 when both activities are equal, meaning that the decay product has remained close to the mother radon long enough to achieve balance, within a few hours. In this condition each additional pCi/L radon will increase exposure, with 0.01 WL (Work Rate - the radioactivity measure commonly used in mining) Detailed explanations of WL are given in the Concentration Unit. This condition is not always fulfilled; in many homes, the equilibrium part is usually 40%; ie, there will be 0.004 WL girls for every pCi/L radon in the air. 210 Pb takes longer (decades) to come in equilibrium with radon, but, if the environment allows dust accumulation over long periods of time, 210 Pb and its decay products can contribute to overall radiation levels as well.
Due to its electrostatic charge, the radon progeny is attached to the surface or dust particles, whereas the radon gas is not. Attachments remove it from the air, usually causing the balance factor in the atmosphere to be less than one. Equilibrium factors are also derived by air circulation or air filtration devices, and enhanced by airborne dust particles, including cigarette smoke. In high concentrations, airborne radionic isotopes contribute significantly to human health risks. The equilibrium factor found in the epidemiological study was 0.4.
Maps Radon
History and etymology
Radon is the fifth radioactive element found, in 1899 by Ernest Rutherford and Robert B. Owens, after uranium, thorium, radium and polonium. In 1900 Friedrich Ernst Dorn reported on several experiments where he noticed that radium compounds emit radioactive gas which he named 'Radium Emanation' ('Ra Em'). Before that, in 1899, Pierre and Marie Curie observed that the radium emitted radium remained radioactive for a month. Later that year, Robert B. Owens and Ernest Rutherford, at McGill University in Montreal, noticed variations when trying to measure radiation from thorium oxide. Rutherford noticed that the thorium compound continuously emits radioactive gas that retains radioactive force for several minutes, and calls this 'emanation' gas (from Latin emanare - until it passes and emanatio i> - expired), and then Eorium Thorium ( Th Em ). In 1901, Rutherford and Harriet Brooks indicated that emanations were radioactive, but credited Curies for the discovery of elements. In 1903, a similar emanation was observed from actinium by AndrÃÆ' © -Louis Debierne and called 'Actinium Emanation' ('Ac Em').
Some short names will soon be proposed for three emanations: exradio , exthorio , and exactinio in 1904; radon , thoron , and akton in 1918; radeon , thoreon and actineon in 1919, and finally radon , thoron , and actinon in 1920. (The radon name is not related to Austrian mathematician Johann Radon.) The spectral similarities of these three gases with argon, krypton, and xenon, and observed inertial chemistry led by Sir William Ramsay for suggested in 1904 that "emanations" might contain new elements of the noble gas family.
In 1909, Ramsay and Robert Whytlaw-Gray isolated radon, determining the melting temperature and the approximate density. In 1910 they determined that it was the heaviest known gas. and wrote that "L'expression de l'ÃÆ' Â © manation du radium est fort incommode", (expression 'radium emanation' is very awkward) and suggested the new name niton (Nt) (from the Latin "nitens" meaning "shine" ) to emphasize the nature of radioluminescence, and in 1912 it was accepted by the International Commission for Atomic Weight. In 1923, the International Committee for the Elements of Chemistry and International Union of Pure and Applied Chemistry (IUPAC) chose between the names of radon (Rn), thoron (Tn), and actinon (An). Then, when the isotope is numbered instead of named, the element takes the name of the most stable isotope, radon , while Tn changes its name to 220 Rn and An is named 219 Rn, which causes confusion in the literature regarding element discovery while Dorn discovers radon isotope, he is not the first to discover radon elements. Until the late 1960s, the element was also referred to simply as emanation . The radon fluoride compound, first synthesized, was obtained in 1962. Even today, the word radon can refer to any of its elements or isotopes 222 Rn, with thoron is still used as a short name for 220 Rn to stem this ambiguity.
The danger of high exposure to radon in the mine, where exposure can reach 1,000,000 Bq/m 3 , has long been known. In 1530, Paracelsus described the wasting of miner's diseases, metallorum mala, and Georg Agricola recommending mine vents to avoid the disease of this mountain ( Bergsucht ). In 1879, the condition was identified as lung cancer by Herting and Hesse in the investigation of miners from Schneeberg, Germany. The first major study with radon and health occurred in the context of uranium mining in the Joachimsthal region of Bohemia. In the US, studies and mitigation have only been followed for decades of health effects on uranium miners from the Southwest United States used during the early Cold War; standard not implemented until 1971.
The presence of radon in the indoor air is documented in the early 1950s. In the early 1970s research began to address the source of indoor radon, determinants of concentration, health effects, and mitigation approaches. In the United States, radon problems in the room received widespread publicity and intensive investigation after the incident was widely publicized in 1984. During routine monitoring at a Pennsylvania nuclear power plant, a worker was found to be contaminated with radioactivity. The high concentrations of radon in his home were then identified as responsible.
Genesis
Concentration Unit
All discussions of radon concentrations in the environment refer to 222 Rn. While the average production rate of 220 Rn (from the thorium decay series) is similar to 222 Rn, the number 220 Rn in the environment is much smaller than 222 Rn due to short half-life 220 Rn (55 seconds, compared to 3.8 days).
The concentration of radon in the atmosphere is usually measured in becquerel per cubic meter (Bq/m 3 ), SI derived unit. Another common unit of measurement in the US is picocuries per liter (pCi/L); 1 pCi/L = 37 Bq/m 3 . The typical domestic exposure averages around 48 Bq/m 3 indoors, though this varies greatly, and 15 Bq/m 3 outdoors.
In the mining industry, displays are traditionally measured in work levels (WL), and cumulative views in work-level months (WLM); 1 WL is equal to the combination of children aged 222 Rn ( 218 Po, 214 214 Po) in 1 liter of air that releases 1,3 ÃÆ'â € "10 5 Me MeV potential alpha energy; one WL is equal to 2.08 Ã,ÃÆ' ± 10 "/-5 joule per cubic meter air (J/m 3 ). SI units of cumulative exposure are expressed in joule-hour per cubic meter (JÃ, · h/m 3 ). One WLM is equivalent to 3.6 ÃÆ'â € "10 -3 JÃ,  · h/m 3 . An exposure to 1 WL for 1 working month (170 hours) equals 1 cumulative exposure WLM. 1 WLM cumulative display is roughly equivalent to one-year live in the atmosphere with a radon concentration of 230 Bq/m 3 .
222 Rn decays to 210 Pb and other radioisotopes. Level 210 Pb can be measured. The deposition rate of this radioisotope depends on the weather.
The radon concentrations found in the natural environment are too low to be detected by chemical means. A 1000 Bq/m 3 (relatively high) concentration corresponds to 0.17Ã, picogram per cubic meter. The average concentration of radon in the atmosphere is about 6 percent molar, or about 150 atoms in every ml of air. Earth's atmospheric radon activity comes from only a few tens of grams of radon, consistently replaced by a greater decay of radium and uranium.
Natural
Radon is produced by radioactive decay of radium-226, which is found in uranium ore, phosphate rock, shale, igneous and metamorphic rocks such as granite, gneiss, and schist, and to a lesser extent, in common rocks such as limestone. Every square mile of ground level, up to a depth of 6 inches (2.6 km 2 to a depth of 15 cm), contains about 1 gram of radium, which releases small amounts of radon into the atmosphere. On a global scale, an estimated 2,400 million curies (90 EBq) of radon are released from the soil every year.
Radon concentration can be very different from one place to another. In the open air, it ranges from 1 to 100 Bq/m 3 , even less (0.1 Bq/m 3 ) above the ocean. In the aired caves or mines, or houses with bad air, the concentration rises to 20-2,000 Bq/m 3 .
Radon concentrations can be much higher in the context of mining. Ventilation regulations are instructed to maintain radon concentrations in uranium mines under "work rates", with 95 percent levels ranging up to nearly 3 WL (546 pCi 222 Rn per liter of air; 20.2 kBq/m < > 3 , measured from 1976 to 1985). The concentration in the air in the Gastein Heat Gallery (unventilated) averages 43kBq/m 3 (1,2Ã,nCi/L) with a maximum value of 160 kBq/m 3 ( 4.3 nCi/L).
Radon mostly appears with radium decay chains and uranium series ( 222 Rn), and few with thorium series ( 220 Rn). This element radiates naturally from the ground, and some building materials, worldwide, wherever traces of uranium or thorium can be found, and especially in areas with granite or shale soils, which have higher uranium concentrations. Not all granite areas are vulnerable to high radon emissions. Being a rare gas, it usually migrates freely through fault and fragmented soil, and can accumulate in caves or water. Because of the very short half-life (four days for 222 Rn), the radon concentration decreases very rapidly as distance from the production area increases. Radon concentrations vary greatly with season and atmospheric conditions. For example, it has been proven to accumulate in the air if there is a meteorological inversion and a slight wind.
High concentrations of radon can be found in some springs and hot springs. Boulder City, Montana; Misasa; Bad Kreuznach, Germany; and the Japanese state has radium-rich springs that emit radon. To be classified as radon mineral water, radon concentration should be above 2 nCi/L (74 kBq/m 3 ). Radon mineral water activity reaches 2,000 kBq/m 3 in Merano and 4,000 kBq/m 3 in Lurisia (Italy).
The natural radon concentration in the Earth's atmosphere is so low that the radon-rich water in contact with the atmosphere will continue to lose radon by evaporation. Therefore, groundwater has a higher concentration of 222 Rn than surface water, since radon is continuously produced by radioactive decay 226 Ra is present in the rock. Similarly, soil saturated zones often have higher radon content than unsaturated zones because of diffuse losses to the atmosphere.
In 1971, Apollo 15 passed 110 km (68 mi) above the Aristarchus plateau on the Moon, and detected a significant increase in alpha particles suspected to be caused by the decay of 222 Rn. The presence of 222 Rn has been inferred later from data obtained from the Lunar alpha particle alpha spectrometer.
Radon is found in some petroleum. Since radon has the same pressure and temperature curve for propane, and the oil refinery separates petrochemicals based on their boiling point, the pipe carrying propane that has just been separated in the oil refinery can become radioactive due to the decaying radon and its products.
Residues from the petroleum and natural gas industries often contain radium and their daughters. The sulfate scale of the oil wells can be rich in radium, while water, oil, and gas from wells often contain radon. Radon decays form a solid radioisotope that forms a layer on the inside of the pipe.
Accumulation in buildings
High concentrations of radon at home were discovered by chance in 1985 after rigorous radiation testing conducted at the entrance of a nuclear power plant revealed that Stanley Watras, an engineer at the plant, was contaminated by radioactive substances. The typical domestic exposure is about 100 Bq/m 3 (2.7 pCi/L) indoors. Some radon levels will be found in all buildings. Radon mostly enters a building directly from the ground through the lowest level in the building in contact with the ground. High levels of radon in the water supply can also increase the level of radon air in the room. The radon entry points into the building are cracks in solid foundations, construction joints, wall cracks, hanging floor gaps, cracks around service pipes, inner cavities, and water supply. Radon concentrations in the same location may differ by a factor of two over a period of 1 hour. Also, the concentration in one room of a building may differ significantly from the concentration in adjacent rooms. The soil characteristics of the dwelling are the most important radon source for the ground floor and higher indoor radon concentrations observed on the lower floors. Most high radon concentrations have been reported from places near the cesarean zone; then the existence of the relationship between the respiratory rate of the cesarean and the inner radon concentration is clear.
The distribution of radon concentrations generally will vary from room to room, and the reading is averaged according to the regulatory protocol. The concentration of radon in a room is usually assumed to follow a lognormal distribution in a particular region. Thus, the geometric mean is generally used to estimate the "average" radon concentration in an area.
The average concentration ranges from less than 10 Bq/m 3 to over 100 Bq/m 3 in some European countries. The typical geometric deviation standard found in the study ranged between 2 and 3, which means (given rule 68-95-99,7) that the radon concentration is expected to be more than a hundred times the average concentration for 2 to 3% of cases.
Some of the highest radon hazards in the United States are found in Iowa and in the Appalachian Mountain area in southeastern Pennsylvania. Some of the highest readings ever recorded in the Irish town of Mallow, County Cork, prompted local fears about lung cancer. Iowa has the highest average radon concentration in the United States due to the significant glaciation that lands granite rock from the Canadian Shield and stores it as the soil that forms rich Iowa farmland. Many cities in the state, such as Iowa City, have passed the requirements for radon resistant construction in new homes.
In some locations, uranium tailings have been used for landfill and then built on, allowing increased radon exposure.
Since radon is a colorless and odorless gas, the only way to know how much is in the air or water is to do a test. In the United States radon test kits are available to the public at retail stores, such as hardware stores, for home use and testing available through licensed professionals, who often become home inspectors. Attempts to reduce indoor radon levels are called radon mitigation. In the US, the Environmental Protection Agency recommends all homes tested for radon.
Industrial production
Radon is obtained as a by-product of uraniferous ore after being transferred to a 1% solution of hydrochloric acid or hydrobromate. The gas mixture extracted from the solution contains H
2 , O
2 , He, Rn, CO
2 , H
2 O and hydrocarbons. The mixture is purified by passing it over copper at 720 ° C to remove H
2 and O
2 , and then KOH and P
2 O
5 is used to remove acids and moisture with sorption. Radon is condensed by liquid nitrogen and purified from residual gas by sublimation.
The commercialization of the radon is regulated, but is available in small quantities for the calibration of the <22> measurement system Rn, at a price of nearly $ 6,000 per milliliter of radium solution (which contains only about 15 radon picograms actually at any given moment). Radon is produced by a radium-226 solution (half-life of 1600 years). Radium-226 decays by emission of alpha-particles, producing radon that collects more than a sample of radium-226 at a rate of about 1 mm 3 /day per gram of radium; fast equilibrium is achieved and radon is produced in a stable stream, with the same activity as radium (50 Bq). The gas 222 Rn (half life about four days) comes out of the capsule through diffusion.
Concentration Scale
Apps
Medical
The early form of shamanism of the 20th century was the treatment of disease in the radiotorium. It is a small enclosed space for the patient to be exposed to radon because of its "drug effect". The carcinogenic nature of radon due to ionizing radiation becomes clear later on. Radon radon radon radon has been used to kill cancer cells, but it does not improve the health of healthy cells. Ionizing radiation causes the formation of free radicals, which produce damage to genetic and other cells, resulting in increased rates of disease, including cancer.
Radon exposure, a process known as radiation therapy, has been suggested to reduce autoimmune diseases such as arthritis. As a result, in the late twentieth and early twentieth centuries, the "health mines" established in Basin, Montana attracted people seeking help from health problems such as arthritis through limited exposure to radioactive and radon mine water. This practice is not recommended because of the poorly documented effects of high-dose radiation on the body.
The radioactive water baths have been applied since 1906 in JÃÆ'¡chymov, Czech Republic, but even before the discovery of radon they were used in Bad Gastein, Austria. Radium-rich springs are also used in traditional Japanese onsen in Misasa, Tottori Prefecture. Drinking therapy is applied in Bad Brambach, Germany. Inhalation therapy is done in Gasteiner-Heilstollen, Austria, at? WieradÃÆ'³w-ZdrÃÆ'³j, Czerniawa-ZdrÃÆ'³j, Kowary, L? Dek ZdrÃÆ'³j, Poland, at Harghita B? I, Romania, and in Boulder, United States. In the US and Europe there are some "radon spas", where people sit for a few minutes or hours in the high radon atmosphere in the belief that low-dose radiation will refresh or energize them.
Radon has been commercially produced 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 implanted seeds, made of gold or glass, mainly used to treat cancer. Gold seeds are produced by filling long tubes with radon pumped from a radium source, the tubes are then divided into short sections by shriveling and cutting. The golden layer keeps radon inside, and filters out alpha and beta radiation, while allowing gamma rays to escape (which kills the diseased tissue). Its activities can range from 0.05 to 5 millicuries per seed (2 to 200 MBq). Gamma rays are produced by radon and the first short elements of the decay chains ( 218 Po, 214 Pb, 214 Bi, 214 Po).
Radon and its first decay products are very short-lived, the seeds are left in place. After 12 half-lives (43 days), radon radioactivity is at 1/2000 of the original level. At this stage, the major residual activity is derived from a decay product of <210 Pb radon decay, whose half-life (22.3 years) is 2000 times of radon (and whose activity is 1/2,000 radon), and its derivatives < soup> 210 Bi and 210 Po.
At the beginning of the 20th century in the US, gold contaminated with radon daughter 210 Pb entered the jewelry industry. It comes from a golden seed that has held 222 Rn that has been melted after radon decays.
Scientific
Emanation Radon of the soil varies with soil type and with surface uranium content, so that the external radon concentration can be used to track air mass to a limited extent. This fact has been used by some atmospheric scientists. Because of the rapid loss of radon into the air and relatively rapid decay, radon is used in hydrological studies that examine the interactions between groundwater and flow. Any significant radon concentration in the flow is a good indicator that there is local input from ground water.
Radon soil concentrations have been used in an experimental way to map buried underground geological fissures because the concentrations are generally higher than the fault. Similarly, he has found some limited use in prospecting for geothermal gradients.
Some researchers have investigated changes in groundwater radon concentration for earthquake prediction. Radon has a half-life of about 3.8 days, which means that it can be found only shortly after it is produced in a radioactive decay chain. For this reason, it has been hypothesized that the increase in radon concentration is due to a new crack generation underground, which will allow increased groundwater circulation, flushing out radon. New crack generation may not be unreasonably assumed to precede major earthquakes. In the 1970s and 1980s, scientific measurements of radon emissions near the fault found that earthquakes often occur without radon signals, and radon is often detected without an earthquake to follow. It was then dismissed by many as an unreliable indicator. In 2009, it was being investigated as a possible precursor by NASA.
Radon is a known pollutant that is emitted from geothermal power plants because it is present in a material that is pumped from underground. It spreads rapidly, and there is no radiological hazard that has been shown in any investigation. In addition, the typical system re-injects the material deep underground and releases it on the surface, resulting in minimal environmental impact.
In the 1940s and '50s, radon was used for industrial radiography, another X-ray source, which became available after World War II, rapidly replaced radon for this application, because it was cheaper and had more alpha radiation hazards a little.
Health risks
In the mines
Radon-222 decay products have been classified by the International Agency for Research on Cancer as carcinogenic in humans, and as inhalable gas, lung cancer is a particular concern for people exposed to high levels of radon for a sustained period. During the 1940s and '50s, when safety standards requiring expensive ventilation at the mine were not widely implemented, radon exposure was associated with lung cancer among uranium non-smoking miners and other hard rock materials in what is now Republic Czech, and then among them. miners from the Southwest United States and South Australia. Although this danger was known in the early 1950s, the dangers of this work remained poorly managed in many mines until the 1970s. During this period, some entrepreneurs opened uranium mines in the United States to the general public and advertised the alleged health benefits of inhaling the underground radon gas. The claimed health benefits include pain, sinus, asthma and rheumatism, but this proved wrong and the government banned the advertisement in 1975.
Since then, ventilation and other measures have been used to reduce radon levels in most affected mines that continue to operate. In recent years, the average annual exposure of uranium miners has fallen to the same level with inhaled concentrations in some homes. This has reduced the risk of cancer caused by the work of radon, although health problems can persist for those currently working in affected mines and for those who have worked in the past. Since the relative risk for miners has decreased, so has the ability to detect excess risk among the population.
Residues from uranium ore processing can also be a source of radon. Radon produced from high radium content in landfills and tailings pools that are not found can be easily released into the atmosphere and affect people living nearby.
In addition to lung cancer, researchers have theorized the possibility of an increased risk of leukemia due to exposure to radon. Empirical support from studies on the general population is inconsistent, and studies of uranium miners find correlations between exposure to radon and chronic lymphocytic leukemia.
Miners (as well as milled and ore transport workers) working in the uranium industry in the United States between 1940 and 1971 may be eligible for compensation under the Radiation Compensation Radiation Act (RECA). Survivors may also apply in cases where previously employed persons have died.
Domestic rate exposure
Radon exposure (mostly radonic females) has been associated with lung cancer in various case-control studies conducted in the United States, Europe and China. There are about 21,000 deaths per year in the US due to radon-induced lung cancer. One of the most comprehensive radon studies conducted in the United States by Dr. R. William Field and colleagues found a 50% increased risk of lung cancer even at prolonged exposure to EPA level of 4 pCi/L. Pooled analysis of North America and Europe further supports these findings. However, discussions on opposite results are still ongoing, particularly recent retrospective case-control studies of lung cancer risk showing a substantial decrease in cancer rates for radon concentrations between 50 and 123 Bq per cubic meter.
Most models of residential radon exposure are based on a miner's study, and a direct estimate of the risks posed to homeowners would be more desirable. Because of the difficulty of measuring the risk of radon compared with smoking, the effect model often utilizes it.
Radon has been considered the second leading cause of lung cancer and the leading cause of cancer death by the United States Environmental Protection Agency. Others have reached similar conclusions for England and France. Radon exposure in homes and offices may arise from certain subsurface rock formations, as well as from certain building materials (eg, some granites). The greatest risk of exposure to radon appears in airtight buildings, lack of ventilation, and has a foundation leak that allows air from the ground into basements and dwellings.
Action and reference levels
WHO presented in 2009 recommended reference level (national reference level), 100 Bq/m 3 , for radon at residence. The recommendation also says that if this is not possible, 300 Bq/m 3 should be selected as the highest level. The national reference level should not be a limit, but should represent the maximum acceptable annual maximum radon concentration in a dwelling.
Radon concentrations that can be acted upon at home vary depending on the recommendation organization, for example, the US Environmental Protection Agency encourages action taken at concentrations as low as 74 Bq/m 3 (2 pCi/L), and the Union Europe recommends action taken when concentrations reach 400 Bq/m 3 (11 pci/L) for old houses and 200 Bq/m 3 (5 pCi/L) for a new one. On July 8, 2010, the UK Health Protection Agency issued a new suggestion to set the "Target Level" 100Ã, Bq/m 3 while maintaining the "Level Action" of 200 Bq/m 3 . The same rate (as the UK) applies to Norway from 2010; in all new home precautions should be taken against the accumulation of radon.
Relationship with smoking
The results of epidemiological studies indicate that the risk of lung cancer increases with exposure to residential radon. An example of a famous source of error is smoking. In addition, smoking is the most important risk factor for lung cancer. In the West, tobacco smoke is thought to account for about 90% of all lung cancers.
According to the EPA, the risk of lung cancer for smokers is significant because of the synergistic effects of radon and smoking. For this population about 62 people in a total of 1,000 will die of lung cancer compared to 7 people in a total of 1,000 people who never smoked. It can not be excluded that the risk of non-smokers should be explained primarily by the combined effects of radon and second-hand smoke (see below).
Radon, like any other known or suspected external risk factor for lung cancer, is a threat to smokers and former smokers. This is demonstrated by the European merger research. A commentary for the merger study states: "It is not appropriate to talk about the risk of radon at home, the risk is from smoking, aggravated by the synergistic effects of radon for smokers." Without smoking, the effect seems very small to be insignificant.
According to the European merger study, there is a difference in risk of radon between histologic types. Small cell lung carcinomas, which practically affect only smokers have a high risk of radon. For other histologic types such as adenocarcinoma, the type that mainly affects never smokers, the risk of radon appears to be lower.
A radiation study of postmastectomy radiotherapy showed that a simple model previously used to assess joint risks and separate radiation and smoking should be developed. This is also supported by a new discussion of the calculation method, LNT, which has been routinely used.
An important but unanswered question concerning the possibility that cancer risk from passive smokers can increase with exposure to residential radon. The baseline data for the European merger study makes it impossible to exclude that the effect of such synergies is an explanation for the (very limited) increase in risk of radon expressed for non-smokers.
A 2001 study, which included 436 cases (never smokers with lung cancer), and the control group (1649 never smokers) showed that exposure to radon increased the risk of lung cancer in smokers who never smoked. But groups exposed to secondhand smoke at home seem to bear all the risks involved, while those who are not exposed to secondhand smoke show no increased risk with increased radon levels.
In drinking water
The effects of radon if ingested are equally unknown, although studies have found that the biological half is about 30-70 minutes, with a 90 percent removal in 100 minutes. In 1999 the National Research Council investigated the radon problem in drinking water. Risks associated with consumption are considered almost negligible. Water from underground sources can contain large amounts of radon depending on the conditions of the surrounding rocks and soils, whereas surface sources are generally not.
Besides being digested through drinking water, radon is also released from water as the temperature rises, the pressure decreases and when the water is aerated. Optimal conditions for radon release and exposure occur during bath. Water with a concentration of radon 10 4 pCi/L can increase the concentration of indoor air radon by 1 pCi/L under normal conditions.
Testing and mitigation
There is a relatively simple test for radon gas. In some countries, these tests are methodically performed in areas known to be systematic hazards. The radon detection device is commercially available. Digital radon detectors provide continuous measurements that provide daily, weekly, short-term and long-range readings via digital display. The short-term radon test device used for initial screening purposes is cheap, in some cases free. There are important protocols for taking short-term radon tests and it is very important that they are closely followed. This package includes a collector that users are on the most decent home floor for 2 to 7 days. The user then sends the collector to the laboratory for analysis. Long-term kits, collecting up to a year or more, are also available. An open ground test instrument can test the radon emissions from the soil before construction begins. Radon concentrations can vary each day, and accurate estimates of radon exposure require long-term radon measurements in spaces where an individual spends a lot of time.
Radon levels fluctuate naturally, due to factors such as temporary weather conditions, so preliminary tests may not be an accurate assessment of the average home radon level. Radon levels are at maximum during the coolest part of the day when the pressure difference is greatest. Therefore, high yields (more than 4 pCi/L) justify repetition of tests before undertaking more costly reduction projects. Measurements between 4 and 10 pCi/L guarantee long-term radon test. Measurements of more than 10 pCi/L warrant only other short-term tests so that the reduction steps are not too late. A real estate buyer is advised to delay or refuse a purchase if the seller has not succeeded in subverting radon to 4Ã, pCi/L or less.
Since radon half-life is only 3.8 days, removing or isolating the source will greatly reduce the danger in a few weeks. Another method of reducing radon levels is by modifying building vents. Generally, indoor radon concentrations increase as the ventilation level decreases. In well-ventilated areas, the concentration of radon tends to be parallel to the outer value (usually 10 Bq/m 3 , ranging from 1 to 100 Bq/m 3 ).
The four major ways to reduce the number of home-grown radon are:
- Depressurization of sub-slab (ground suction) by increasing ventilation under the floor;
- Fixed home ventilation and avoided radon transport from the basement to the living room;
- Install a radon system in the basement;
- Put positive pressure or positive supply ventilation system.
According to the EPA method to reduce radon "... mainly used is a ventilation pipe system and fan, which pulls radon from the bottom of the house and outside ventilation", also called sub-slab depressurization, active soil depressurization, or ground suction. Generally, indoor radon can be reduced by deplutization of sub-slab and tiring of radon-filled air into the open air, away from windows and other building openings. "EPA generally recommends methods that prevent the entry of radon.Suction of soil, for example, prevents radon from entering your house by drawing radon from under the house and ventilation through pipes, or pipes, into the air above the house where quickly diluted" and "EPA does not recommend the use self-sealing to reduce radon because, by itself, sealing has not been shown to decrease radon levels significantly or consistently ".
A positive pressure ventilation system can be combined with a heat exchanger to recover energy in the process of exchanging the air with the outside, and only exhausting the basement to the outside is not always a viable solution as this can actually draw radon gas into place to live. Homes built on crawl space can benefit from radon collectors installed under "radon barrier" (a plastic sheet covering the crawl space). For exploration spaces, the EPA states "Effective methods for reducing radon levels in crawlspace homes include covering earth floors with high-density plastic sheets • Ventilation and fan pipes are used to pull radon from the bottom of the sheet and vent into the outdoors. called suction submembrane, and when applied appropriately is the most effective way to reduce radon levels in crawlspace homes. "
See also
- The International Radon Project
- Lucas Cell
- Radiation Exposure Compensation Act
- Radiohalo
References
External links
- Radon and radon publications in the United States Environmental Protection Agency
- Radon National Program Service organized by Kansas State University
- Radon's information from Public Health England
- Frequently Asked Questions About Radon at the National Safety Council
- Radon on Periodic Video Table (University of Nottingham)
- Radon and Lung Health from the American Lung Association
- The impact of Radon on your health - Lung Association
- Radon geology, James K. Otton, Linda C.S. Gundersen, and R. Randall Schumann
- Home Buyers and Seller's Guide to Radon An article by the Certified International Association of Conservatory Homes (InterNACHI)
- Toxicology Profile for Radon, Draft for Public Comment, Toxic Substance and Registry of Disease, September 2008
- Health Effects of Exposure to Radon : BEIR VI. Risk Health Exposure Committee of Radon (BEIR VI), National Research Council is available on-line UNSCEAR 2000's report to the General Assembly, with a scientific attachment: Appendix B: Exposure from natural radiation sources.
- Should you measure radon concentration in your home ?, Phillip N. Price, Andrew Gelman, in Statistics: Guide for the Unknown , January 2004.
Source of the article : Wikipedia
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