Is Iodine radioactive?
2011 Tōhoku earthquake and tsunami
It was reported that radioactive iodine was detected in the tap water in Fukushima, Tochigi, Gunma, Tokyo, Chiba, Saitama, and Niigata, and radioactive caesium in the tap water in Fukushima, Tochigi and Gunma. Radioactive caesium, iodine, and strontium were also detected in the soil in some places in Fukushima. There may be a need to replace the contaminated soil. Many radioactive hotspots were found outside the evacuation zone, including Tokyo. Food products were also found contaminated by radioactive matter in several places in Japan. On 5 April 2011, the government of the Ibaraki Prefecture banned the fishing of sand lance after discovering that this species was contaminated by radioactive caesium above legal limits. As late as July 2013 slightly elevated levels of radioactivity were found in beef on sale at Tokyo markets.
Radon
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead and various other short-lived radioactive elements; radon itself is the immediate decay product of radium. Its most stable isotope, Rn, has a half-life of only 3.8 days, making radon one of the rarest elements since it decays away so quickly. However, since thorium and uranium are two of the most common radioactive elements on Earth, and they have three isotopes with very long half-lives, on the order of several billions of years, radon will be present on Earth long into the future in spite of its short half-life as it is continually being generated. The decay of radon produces many other short-lived nuclides known as radon daughters, ending at stable isotopes of lead.
Hydroxide
"Ortho"-periodic acid can lose all its protons, eventually forming the periodate ion [IO]. It can also be protonated in strongly acidic conditions to give the octahedral ion [I(OH)], completing the isoelectronic series, [E(OH)], E = Sn, Sb, Te, I; "z" = −2, −1, 0, +1. Other acids of iodine(VII) that contain hydroxide groups are known, in particular in salts such as the "meso"periodate ion that occurs in K[IO(OH)]·8HO.
Radioactive waste
Depending on the decay mode and the pharmacokinetics of an element (how the body processes it and how quickly), the threat due to exposure to a given activity of a radioisotope will differ. For instance iodine-131 is a short-lived beta and gamma emitter, but because it concentrates in the thyroid gland, it is more able to cause injury than caesium-137 which, being water soluble, is rapidly excreted through urine. In a similar way, the alpha emitting actinides and radium are considered very harmful as they tend to have long biological half-lives and their radiation has a high relative biological effectiveness, making it far more damaging to tissues per amount of energy deposited. Because of such differences, the rules determining biological injury differ widely according to the radioisotope, time of exposure
and sometimes also the nature of the chemical compound which contains the radioisotope.
Iodine
Iodine pentafluoride (IF), a colourless, volatile liquid, is the most thermodynamically stable iodine fluoride, and can be made by reacting iodine with fluorine gas at room temperature. It is a fluorinating agent, but is mild enough to store in glass apparatus. Again, slight electrical conductivity is present in the liquid state because of dissociation to and . The pentagonal bipyramidal iodine heptafluoride (IF) is an extremely powerful fluorinating agent, behind only chlorine trifluoride, chlorine pentafluoride, and bromine pentafluoride among the interhalogens: it reacts with almost all the elements even at low temperatures, fluorinates Pyrex glass to form iodine(VII) oxyfluoride (IOF), and sets carbon monoxide on fire.
Iodine-131
Iodine-131 can be "seen" by nuclear medicine imaging techniques (i.e., gamma cameras) whenever it is given for therapeutic use, since about 10% of its energy and radiation dose is via gamma radiation. However, since the other 90% of radiation (beta radiation) causes tissue damage without contributing to any ability to see or "image" the isotope, other less-damaging radioisotopes of iodine such as iodine-123 (see isotopes of iodine) are preferred in situations when "only" nuclear imaging is required. The isotope I-131 is still occasionally used for purely diagnostic (i.e., imaging) work, due to its low expense compared to other iodine radioisotopes. Very small medical imaging doses of I-131 have not shown any increase in thyroid cancer. The low-cost availability of I-131, in turn, is due to the relative ease of creating I-131 by neutron bombardment of natural tellurium in a nuclear reactor, then separating I-131 out by various simple methods (i.e., heating to drive off the volatile iodine). By contrast, other iodine radioisotopes are usually created by far more expensive techniques, starting with reactor radiation of expensive capsules of pressurized xenon gas.
Isotopes of iodine
Radioisotopes of iodine are called radioactive iodine or radioiodine. Dozens exist, but about a half dozen are the most notable in applied sciences such as the life sciences and nuclear power, as detailed below. Mentions of radioiodine in health care contexts refer more often to iodine-131 than to other isotopes.
Iodane
At lower temperatures in the presence of NaOH, (diacetoxyiodo)benzene can also be hydrolyzed to iodosylbenzene which is actually a polymer with the molecular formula (CHOI). Iodosylbenzene is used in organic oxidations. Dess-Martin periodinane (1983) is another powerful oxidant and an improvement of the IBX acid already in existence in 1983. The IBX acid is prepared from 2-iodobenzoic acid and potassium bromate and sulfuric acid and is insoluble in most solvents whereas the Dess-Martin reagent prepared from reaction of the IBX acid with acetic anhydride is very soluble. The oxidation mechanism ordinarily consists of a ligand exchange reaction followed by a reductive elimination.
Sodium iodate
Sodium iodate (NaIO) is the sodium salt of iodic acid. Sodium iodate is an oxidizing agent, and as such it can cause fires upon contact with combustible materials or reducing agents.
Iodine-131
Much smaller incidental doses of iodine-131 than those used in medical therapeutic procedures, are supposed by some studies to be the major cause of increased thyroid cancers after accidental nuclear contamination. These studies suppose that cancers happen from residual tissue radiation damage caused by the I-131, and should appear mostly years after exposure, long after the I-131 has decayed. Other studies can't find a correlation.
Uranium acid mine drainage
Results from studies done in 2002 showed a significant negative correlation between both dissolved uranium radionuclides and hydrogen ions with pH in mine waters. Sorption of dissolved uranium radionuclides in rivers combine with nearby rock sediments can form minerals like Uranophane for example. The chemistry and findings in this case is essentially representative of other uranium mines in the world.
A uranium radionuclide is a radioactive isotope. Radioactivity is natural in the environment, however uranium radionuclides can lead to radioactive decay.In the case of uranium mines, these radionuclides can leach into the water and cause the radioactivity to be carried elsewhere, as well as form precipitates that can be harmful to the environment. The uranium radionuclides can eventually be carried to fruits and vegetables via contaminated waters. Sulfuric acid, oxidation, and alkaline leaching are processes of how radionuclides make their way into the environment. When uranium decays it also produces the isotopes Ra and Rn, which may be environmentally harmful due to the fact that radon is present as an inert gas and therefore, might enter into the soil or atmosphere. Radon then can emit alpha particles and gamma radiation. Three different radioactive isotopes of uranium are uranium-238, uranium-235, and uranium-234. Each has a different half life which determines the isotope's decay rate. When uranium-235 combines with other molecules it creates a chemical reaction that can cause detrimental effects to water. Even though isotope formation occurs naturally, when combined with other elements it can cause the pH of water to become more acidic as discussed previously.
Thyrotoxic myopathy
One treatment option is the use of radioactive iodine which directly destroys the overactive thyroid gland. The thyroid gland naturally uses iodine to produce thyroxine and other hormones. It cannot distinguish between normal iodine and the radioactive version. Administering the radioactive isotope causes the thyroid to take in the lethal iodine and quickly radiation destroys it. Typically overproduction of thyroxine using radio-iodine is blocked with one dose. The drawback to this treatment is the thyroid gland is completely destroyed and patients often develop hypothyroidism. Some do so only a few months after treatment while others may not be affected for 20–30 years. Hypothyroidism patients must begin a lifelong regimen of thyroid replacement hormones. While the onset of hypothyroidism is most common with radio-iodine treatment, the condition has been observed in patients treated with medication series and surgery.
Isotopes of iodine
The isotope I has a half-life less than seven hours, which is too short to be used in biology. Unavoidable "in situ" production of this isotope is important in nuclear reactor control, as it decays to Xe, the most powerful known neutron absorber, and the nuclide responsible for the so-called iodine pit phenomenon.
Potassium iodide
Potassium iodide cannot protect against any other mechanisms of radiation poisoning, nor can it provide any degree of protection against dirty bombs that produce radionuclides other than those of iodine.
Iodine-125
Iodine-125 is commercially available in dilute NaOH solution as I-iodide (or the hypohalite sodium hypoiodite, NaOI) . The radioactive concentration lies at 4 to 11 GBq/ml and the specific radioactivity is >75GBq/µmol. The chemical and radiochemical purity is high. The radionuclidic purity is also high; some I (t=13.1d) is unavoidable due to the neutron capture noted above. The I-126 tolerable content (which is set by the unwanted isotope interfering with dose calculations in brachytherapy) lies at about 0.2% atom fraction of the total iodine (the rest being I-125).
Decay chain
The intermediate stages each emit the same amount of radioactivity as the original radioisotope (i.e. there is a one-to-one relationship between the numbers of decays in successive stages) but each stage releases a different quantity of energy. If and when equilibrium is achieved, each successive daughter isotope is present in direct proportion to its half-life; but since its activity is inversely proportional to its half-life, each nuclide in the decay chain finally contributes as many individual transformations as the head of the chain, though not the same energy. For example, uranium-238 is weakly radioactive, but pitchblende, a uranium ore, is 13 times more radioactive than the pure uranium metal because of the radium and other daughter isotopes it contains. Not only are unstable radium isotopes significant radioactivity emitters, but as the next stage in the decay chain they also generate radon, a heavy, inert, naturally occurring radioactive gas. Rock containing thorium and/or uranium (such as some granites) emits radon gas that can accumulate in enclosed places such as basements or underground mines.
Iodine in biology
When mixed with ammonia and water, elemental iodine forms nitrogen triiodide, which is extremely shock-sensitive and can explode unexpectedly.
Thyroid blocker
If a person consumes a dose of one of these chemical compounds, his or her thyroid may saturate with stable iodine, preventing accumulation of radioactive iodine found after a nuclear meltdown or explosion.
Iodine
The other iodine radioisotopes have much shorter half-lives, no longer than days. Some of them have medical applications involving the thyroid gland, where the iodine that enters the body is stored and concentrated. Iodine-123 has a half-life of thirteen hours and decays by electron capture to tellurium-123, emitting gamma radiation; it is used in nuclear medicine imaging, including single photon emission computed tomography (SPECT) and X-ray computed tomography (X-Ray CT) scans. Iodine-125 has a half-life of fifty-nine days, decaying by electron capture to tellurium-125 and emitting low-energy gamma radiation; the second-longest-lived iodine radioisotope, it has uses in biological assays, nuclear medicine imaging and in radiation therapy as brachytherapy to treat a number of conditions, including prostate cancer, uveal melanomas, and brain tumours. Finally, iodine-131, with a half-life of eight days, beta decays to an excited state of stable xenon-131 that then converts to the ground state by emitting gamma radiation. It is a common fission product and thus is present in high levels in radioactive fallout. It may then be absorbed through contaminated food, and will also accumulate in the thyroid. As it decays, it may cause damage to the thyroid. The primary risk from exposure to high levels of iodine-131 is the chance occurrence of radiogenic thyroid cancer in later life. Other risks include the possibility of non-cancerous growths and thyroiditis.
Nuclear fission product
At least three isotopes of iodine are important. I, I (radioiodine) and I. Open air nuclear testing and the Chernobyl disaster both released iodine-131.
Iodine-123
Dosing can vary; is recommended for thyroid imaging while an uptake test may use . There is a study that indicates a given dose can effectively result in effects of an otherwise higher dose, due to impurities in the preparation. The dose of radioiodine I is typically tolerated by individuals who cannot tolerate contrast mediums containing larger doses of iodine such as used in CT scan, intravenous pyelogram (IVP) and similar imaging diagnostic procedures. Iodine is not an allergen.
Isotopes of iodine
Colloquially, radioactive materials can be described as "hot," and non-radioactive materials can be described as "cold." There are instances in which cold iodide is administered to people in order to prevent the uptake of hot iodide by the thyroid gland. For example, blockade of thyroid iodine uptake with potassium iodide is used in nuclear medicine scintigraphy and therapy with some radioiodinated compounds that are not targeted to the thyroid, such as iobenguane (MIBG), which used to image or treat neural tissue tumors, or iodinated fibrinogen, which is used in fibrinogen scans to investigate clotting. These compounds contain iodine, but not in the iodide form. However, since they may be ultimately metabolized or break down to radioactive iodide, it is common to administer non-radioactive potassium iodide to insure that metabolites of these radiopharmaceuticals is not sequestered by thyroid gland and inadvertently administer a radiological dose to that tissue.
Radiation effects from the Fukushima Daiichi nuclear disaster
The primary releases of radioactive nuclides have been iodine and caesium; strontium and plutonium have also been found. These elements have been released into the air via steam; and into the water leaking into groundwater or the ocean. The expert who prepared a frequently cited Austrian Meteorological Service report asserted that the "Chernobyl accident emitted much more radioactivity and a wider diversity of radioactive elements than Fukushima Daiichi has so far, but it was iodine and caesium that caused most of the health risk – especially outside the immediate area of the Chernobyl plant." Iodine-131 has a half-life of 8 days while caesium-137 has a half-life of over 30 years. The IAEA has developed a method that weighs the "radiological equivalence" for different elements. TEPCO has published estimates using a simple-sum methodology, TEPCO has not released a total water and air release estimate.
Lugol's iodine
Lugol's iodine, also known as aqueous iodine and strong iodine solution, is a solution of potassium iodide with iodine in water. It is a medication and disinfectant used for a number of purposes. Taken by mouth it is used to treat thyrotoxicosis until surgery can be carried out, protect the thyroid gland from radioactive iodine, and to treat iodine deficiency. When applied to the cervix it is used to help in screening for cervical cancer. As a disinfectant it may be applied to small wounds such as a needle stick injury. A small amount may also be used for emergency disinfection of drinking water.
Side effects may include allergic reactions, headache, vomiting, and inflammation of the whites of the eyes. Long term use may result in trouble sleeping and depression. It should not typically be used during pregnancy or breastfeeding. Lugol's iodine is a liquid made up of two parts potassium iodide for every one part elemental iodine in water.
Lugol's iodine was first made in 1829 by the French physician Jean Lugol. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. Lugol's iodine is available as a generic medication and over the counter. In the United Kingdom the NHS pays 9.57 pounds per 500 ml of solution. Lugol's solution is available in different strengths of iodine. Large volumes of concentrations more than 2.2% may be subject to regulation.
Iodine
Elemental iodine is slightly soluble in water, with one gram dissolving in 3450 ml at 20 °C and 1280 ml at 50 °C; potassium iodide may be added to increase solubility via formation of triiodide ions, among other polyiodides. Nonpolar solvents such as hexane and carbon tetrachloride provide a higher solubility. Polar solutions, such as aqueous solutions, are brown, reflecting the role of these solvents as Lewis bases; on the other hand, nonpolar solutions are violet, the color of iodine vapour. Charge-transfer complexes form when iodine is dissolved in polar solvents, hence changing the colour. Iodine is violet when dissolved in carbon tetrachloride and saturated hydrocarbons but deep brown in alcohols and amines, solvents that form charge-transfer adducts.
Radiation effects from the Fukushima Daiichi nuclear disaster
In a survey by the local and central governments conducted on 1,080 children aged 0 to 15 in Iwaki, Kawamata and Iitate on 26–30 March, almost 45 percent of these children had experienced thyroid exposure to radiation with radioactive iodine, although in all cases the amounts of radiation did not warrant further examination, according to the Nuclear Safety Commission on Tuesday 5 July. In October 2011, hormonal irregularies in 10 evacuated children were reported. However, the organization responsible for the study said that no link had been established between the children's condition and exposure to radiation.
Iodane
(Diacetoxyiodo)benzene, "phenyliodine diacetate", "iodosobenzene diacetate", or "PIDA" is an organic reagent used as an oxidizing agent. It is a versatile reagent that can be used for cleaving glycols and α-hydroxy ketones and a variety of other reactions. Classical organic procedures exist for the preparation of (diacetoxyiodo)benzene from peracetic acid and acetic acid, which was also first prepared by Willgerodt.
Iodine oxide
Iodine oxides are chemical compounds of oxygen and iodine. The chemistry of these compound is complicated with only a few having been well characterized. Many have been detected in the atmosphere and are believed to be particularly important at in the marine boundary layer.
Iodine
Elemental iodine is also a skin irritant, and direct contact with skin can cause damage and solid iodine crystals should be handled with care. Solutions with high elemental iodine concentration, such as tincture of iodine and Lugol's solution, are capable of causing tissue damage if used in prolonged cleaning or antisepsis; similarly, liquid Povidone-iodine (Betadine) trapped against the skin resulted in chemical burns in some reported cases.
Windscale fire
Of particular concern at the time was the radioactive isotope iodine-131, which has a half-life of only eight days but is taken up by the human body and stored in the thyroid. As a result, consumption of iodine-131 often leads to cancer of the thyroid. Estimates of additional cancer cases and mortality resulting from the radiological release have varied.
Windscale fire
The fire burned for three days and there was a release of radioactive contamination that spread across the UK and Europe. Of particular concern at the time was the radioactive isotope iodine-131, which may lead to cancer of the thyroid, and it has been estimated that the incident caused 240 additional cancer cases. No one was evacuated from the surrounding area, but there was a worry that milk might be dangerously contaminated. Milk from about of nearby countryside was diluted and destroyed for about a month.
Iodine-131
A common treatment method for preventing iodine-131 exposure is by saturating the thyroid with regular, non-radioactive iodine-127, as an iodide or iodate salt. Free elemental iodine should not be used for saturating the thyroid because it is a corrosive oxidant and therefore is toxic to ingest in the necessary quantities. The thyroid will absorb very little of the radioactive iodine-131 after it is saturated with non-radioactive iodide, thereby avoiding the damage caused by radiation from radioiodine. The most common method of treatment is to give potassium iodide to those at risk. The dosage for adults is 130 mg potassium iodide per day, given in one dose, or divided into portions of 65 mg twice a day. This is equivalent to 100 mg of iodine, and is about 700 times bigger than the nutritional dose of iodine, which is 0.150 mg per day (150 micrograms per day). See potassium iodide for more information on prevention of radioiodine absorption by the thyroid during nuclear accident, or for nuclear medical reasons. The FDA-approved dosing of potassium iodide for this purpose are as follows: infants less than 1 month old, 16 mg; children 1 month to 3 years, 32 mg; children 3 years to 18 years, 65 mg; adults 130 mg. However, some sources recommend alternative dosing regimens.
Isotopes of iodine
Iodine-135 is an isotope of iodine with a half-life of 6.6 hours. It is an important isotope from the viewpoint of nuclear reactor physics. It is produced in relatively large amounts as a fission product, and decays to xenon-135, which is a nuclear poison with a very large thermal neutron cross section, which is a cause of multiple complications in the control of nuclear reactors. The process of buildup of xenon-135 from an accumulated iodine-135 can temporarily preclude a shut-down reactor from restarting. This is known as xenon-poisoning or "falling into an iodine pit".
Iodine (disambiguation)
Iodine may also refer to:
Isotopes of iodine
Iodine-124 is a proton-rich isotope of iodine with a half-life of 4.18 days. Its modes of decay are: 74.4% electron capture, 25.6% positron emission. I decays to Te. Iodine-124 can be made by numereous nuclear reactions via a cyclotron. The most common starting material used is Te.
Iodine-131
Iodine in food is absorbed by the body and preferentially concentrated in the thyroid where it is needed for the functioning of that gland. When I is present in high levels in the environment from radioactive fallout, it can be absorbed through contaminated food, and will also accumulate in the thyroid. As it decays, it may cause damage to the thyroid. The primary risk from exposure to of I is an increased risk of radiation-induced cancer in later life. Other risks include the possibility of non-cancerous growths and thyroiditis.
Radiation effects from the Fukushima Daiichi nuclear disaster
On 22 September the results were published of a survey conducted by the Japanese Science Ministry. This survey showed that radioactive iodine was spread northwest and south of the plant. Soil samples were taken at 2,200 locations, mostly in Fukushima Prefecture, in June and July, and with this a map was created of the radioactive contamination as of 14 June. Because of the short half-life of 8 days only 400 locations were still positive. This map showed that iodine-131 spread northwest of the plant, just like caesium-137 as indicated on an earlier map. But I-131 was also found south of the plant at relatively high levels, even higher than those of caesium-137 in coastal areas south of the plant. According to the ministry, clouds moving southwards apparently caught large amounts of iodine-131 that were emitted at the time. The survey was done to determine the risks for thyroid cancer within the population.
Iodine
Iodine is an essential element for life and, at atomic number "Z" = 53, is the heaviest element commonly needed by living organisms. (Lanthanum and the other lanthanides, as well as tungsten with "Z" = 74, are used by a few microorganisms.) It is required for the synthesis of the growth-regulating thyroid hormones thyroxine and triiodothyronine (T and T respectively, named after their number of iodine atoms). A deficiency of iodine leads to decreased production of T and T and a concomitant enlargement of the thyroid tissue in an attempt to obtain more iodine, causing the disease known as simple goitre. The major form of thyroid hormone in the blood is thyroxine (T), which has a longer half-life than T. In humans, the ratio of T to T released into the blood is between 14:1 and 20:1. T is converted to the active T (three to four times more potent than T) within cells by deiodinases (5'-iodinase). These are further processed by decarboxylation and deiodination to produce iodothyronamine (Ta) and thyronamine (Ta'). All three isoforms of the deiodinases are selenium-containing enzymes; thus dietary selenium is essential for T production.
Isotopes of iodine
In some ways, I is similar to Cl. It is a soluble halogen, fairly non-reactive, exists mainly as a non-sorbing anion, and is produced by cosmogenic, thermonuclear, and in-situ reactions. In hydrologic studies, I concentrations are usually reported as the ratio of I to total I (which is virtually all I). As is the case with Cl/Cl, I/I ratios in nature are quite small, 10 to 10 (peak thermonuclear I/I during the 1960s and 1970s reached about 10). I differs from Cl in that its half-life is longer (15.7 vs. 0.301 million years), it is highly biophilic, and occurs in multiple ionic forms (commonly, I and IO), which have different chemical behaviors. This makes it fairly easy for I to enter the biosphere as it becomes incorporated into vegetation, soil, milk, animal tissue, etc.
Isotopes of iodine
Iodine fission-produced isotopes not discussed above (iodine-128, iodine-130, iodine-132, and iodine-133) have a half lives of a couple of hours or minutes, rendering them almost useless in other applicable areas. Those mentioned are neutron-rich and so go through beta decay to their xenon counterparts. Iodine-128 (25 min half-life) can decay to either tellurium-128 by electron capture, or to xenon-128 by beta decay. It has a specific radioactivity of 2.177 x 10 TBq/g.
Iodine-131
Because of the carcinogenicity of its beta radiation in the thyroid in small doses, I-131 is rarely used primarily or solely for diagnosis (although in the past this was more common due to this isotope's relative ease of production and low expense). Instead the more purely gamma-emitting radioiodine iodine-123 is used in diagnostic testing (nuclear medicine scan of the thyroid). The longer half-lived iodine-125 is also occasionally used when a longer half-life radioiodine is needed for diagnosis, and in brachytherapy treatment (isotope confined in small seed-like metal capsules), where the low-energy gamma radiation without a beta component makes iodine-125 useful. The other radioisotopes of iodine are never used in brachytherapy.
Environmental impact of nuclear power
Nuclear power reactor accidents can result in a variety of radioisotopes being released into the environment. The health impact of each radioisotope depends on a variety of factors. Iodine-131 is potentially an important source of morbidity in accidental discharges because of its prevalence and because it settles on the ground. When iodine-131 is released, it can be inhaled or consumed after it enters the food chain, primarily through contaminated fruits, vegetables, milk, and groundwater. Iodine-131 in the body rapidly accumulates in the thyroid gland, becoming a source of beta radiation.
Iodine
Iodine is the least abundant of the stable halogens, comprising only 0.46 parts per million of Earth's crustal rocks (compare: fluorine 544 ppm, chlorine 126 ppm, bromine 2.5 ppm). Among the eighty-four elements which occur in significant quantities (elements 1–42, 44–60, 62–83, and 90–92), it ranks sixty-first in abundance. Iodide minerals are rare, and most deposits that are concentrated enough for economical extraction are iodate minerals instead. Examples include lautarite, Ca(IO), and dietzeite, 7Ca(IO)·8CaCrO. These are the minerals that occur as trace impurities in the caliche, found in Chile, whose main product is sodium nitrate. In total, they can contain at least 0.02% and at most 1% iodine by weight. Sodium iodate is extracted from the caliche and reduced to iodide by sodium bisulfite. This solution is then reacted with freshly extracted iodate, resulting in comproportionation to iodine, which may be filtered off.
Isotopes of iodine
The gamma-emitting isotopes iodine-123 (half-life 13 hours), and (less commonly) the longer-lived and less energetic iodine-125 (half-life 59 days) are used as nuclear imaging tracers to evaluate the anatomic and physiologic function of the thyroid. Abnormal results may be caused by disorders such as Graves' disease or Hashimoto's thyroiditis. Both isotopes decay by electron capture (EC) to the corresponding tellurium nuclides, but in neither case are these the metastable nuclides Te-123m and Te125m (which are of higher energy, and are not produced from radioiodine). Instead, the excited tellurium nuclides decay immediately (half-life too short to detect). Following EC, the excited Te-123 from I-123 emits a high-speed 127 keV internal conversion electron (not a beta ray) about 13% of the time, but this does little cellular damage due to the nuclide's short half-life and the relatively small fraction of such events. In the remainder of cases, a 159 keV gamma ray is emitted, which is well-suited for gamma imaging.
Iodine
The simplest compound of iodine is hydrogen iodide, HI. It is a colourless gas that reacts with oxygen to give water and iodine. Although it is useful in iodination reactions in the laboratory, it does not have large-scale industrial uses, unlike the other hydrogen halides. Commercially, it is usually made by reacting iodine with hydrogen sulfide or hydrazine:
At room temperature, it is a colourless gas, like all of the hydrogen halides except hydrogen fluoride, since hydrogen cannot form strong hydrogen bonds to the large and only mildly electronegative iodine atom. It melts at −51.0 °C and boils at −35.1 °C. It is an endothermic compound that can exothermically dissociate at room temperature, although the process is very slow unless a catalyst is present: the reaction between hydrogen and iodine at room temperature to give hydrogen iodide does not proceed to completion. The H–I bond dissociation energy is likewise the smallest of the hydrogen halides, at 295 kJ/mol.
Potassium iodide
But equally important to the question of KI is the fact that radioactivity releases are not "local" events. Researchers at the World Health Organization accurately located and counted the cancer victims from Chernobyl and were startled to find that "the increase in incidence [of thyroid cancer] has been documented up to 500 km from the accident site... significant doses from radioactive iodine can occur hundreds of kilometers from the site, beyond emergency planning zones." Consequently, far more people than anticipated were affected by the radiation, which caused the United Nations to report in 2002 that "The number of people with thyroid cancer... has exceeded expectations. Over 11,000 cases have already been reported."
Iodine
Though it is the least reactive of the halogens, iodine is still one of the more reactive elements. For example, while chlorine gas will halogenate carbon monoxide, nitric oxide, and sulfur dioxide (to phosgene, nitrosyl chloride, and sulfuryl chloride respectively), iodine will not do so. Furthermore, iodination of metals tends to result in lower oxidation states than chlorination or bromination; for example, rhenium metal reacts with chlorine to form rhenium hexachloride, but with bromine it forms only rhenium pentabromide and iodine can achieve only rhenium tetraiodide. By the same token, however, since iodine has the lowest ionisation energy among the halogens and is the most easily oxidised of them, it has a more significant cationic chemistry and its higher oxidation states are rather more stable than those of bromine and chlorine, for example in iodine heptafluoride.
Health effects of radon
Radon () is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of radium. It is one of the densest substances that remains a gas under normal conditions, and is considered to be a health hazard due to its radioactivity. Its most stable isotope, Rn, has a half-life of 3.8 days. Due to its high radioactivity, it has been less well-studied by chemists, but a few compounds are known.
Iodine-131
Most I-131 production is from nuclear reactor neutron-irradiation of a natural tellurium target. Irradiation of natural tellurium produces almost entirely I-131 as the only radionuclide with a half-life longer than hours, since most lighter isotopes of tellurium become heavier stable isotopes, or else stable iodine or xenon. However, the heaviest naturally occurring tellurium nuclide, Te-130 (34% of natural Te) absorbs a neutron to become tellurium-131, which beta decays with a half-life of 25 minutes, to I-131.
Isotopes of iodine
All other iodine radioisotopes have half-lives less than 60 days, and four of these are used as tracers and therapeutic agents in medicine. These are I, I, I, and I. All industrial production of radioactive iodine isotopes involves these four useful radionuclides.
Iodine
In early periodic tables, iodine is often given the symbol "J", for "jod", its name in German.
Iodine-125
To isolate radioiodine, the irradiated capsule is first cooled (to collect free iodine gas on the capsule sides) and the remaining Xe gas is allowed to escape. The inner walls of the capsule are then rinsed with dilute NaOH solution to collect iodine as soluble iodide and hypoiodite OI, according to the standard disproportionation reaction of halogens in alkaline solutions. Any cesium immediately oxidizes and passes into the water as Cs. In order to eliminate any long-lived Cs and Cs which may be present in small amounts, the solution is passed through a cation-exchange column, which exchanges Cs for another non-radioactive cation. The radioiodine (as anion I or OI ) remains in solution as iodide/hypoiodite.
Chemical oxygen iodine laser
Chemical oxygen iodine laser, or COIL, is an infrared chemical laser. As the beam is infrared, it cannot be seen with the naked eye. It is capable of output power scaling up to megawatts in continuous mode. Its output wavelength is 1315 nm, a transition wavelength of atomic iodine.
Iodide
An iodide ion is the ion I. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts, not organoiodine compounds. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine deficiency affects two billion people and is the leading preventable cause of intellectual disability.
Iodine-125
Long irradiations are disadvantageous. Iodine-125 itself has a neutron capture cross section of 900 barns, and consequently during a long irradiation, part of the I formed will be converted to I, a beta-emitter and positron-emitter with a half-life of 13.1 days, which is not medically useful. In practice, the most useful irradiation time in the reactor amounts to a few days. Thereafter, the irradiated gas is allowed to decay for three or four days to dispose of short-lived unwanted isotopes, and to allow the newly created xenon-125 (half-life 17 hours) to decay to iodine-125.
Iodine
Most of the iodides of the pre-transition metals (groups 1, 2, and 3, along with the lanthanides and actinides in the +2 and +3 oxidation states) are mostly ionic, while nonmetals tend to form covalent molecular iodides, as do metals in high oxidation states from +3 and above. Ionic iodides MI tend to have the lowest melting and boiling points among the halides MX of the same element, because the electrostatic forces of attraction between the cations and anions are weakest for the large iodide anion. In contrast, covalent iodides tend to instead have the highest melting and boiling points among the halides of the same element, since iodine is the most polarisable of the halogens and, having the most electrons among them, can contribute the most to van der Waals forces. Naturally, exceptions abound in intermediate iodides where one trend gives way to the other. Similarly, solubilities in water of predominantly ionic iodides (e.g. potassium and calcium) are the greatest among ionic halides of that element, while those of covalent iodides (e.g. silver) are the lowest of that element. In particular, silver iodide is very insoluble in water and its formation is often used as a qualitative test for iodine.
Ioflupane (123I)
The iodine introduced during manufacture is a radioactive isotope, I-123, and it is the properties of this isotope that makes the solution visible to a gamma camera. I-123 has a half-life of approximately 13 hours and a gamma photon energy of 159 keV making it an appropriate radionuclide for medical imaging. The solution also contains 5% ethanol to aid solubility and is supplied sterile since it is intended for intravenous use.
Portable water purification
Iodine used for water purification is commonly added to water as a solution, in crystallized form, or in tablets containing tetraglycine hydroperiodide that release 8 mg of iodine per tablet adaptation to chronic tetraglycine hydroperiodide. The iodine kills many, but not all, of the most common pathogens present in natural fresh water sources. Carrying iodine for water purification is an imperfect but lightweight solution for those in need of field purification of drinking water. Kits are available in camping stores that include an iodine pill and a second pill (vitamin C or ascorbic acid) that will remove the iodine taste from the water after it has been disinfected. The addition of vitamin C, in the form of a pill or in flavored drink powders, precipitates much of the iodine out of the solution, so it should not be added until the iodine has had sufficient time to work. This time is 30 minutes in relatively clear, warm water, but is considerably longer if the water is turbid or cold. Iodine treated drinking water, treated with tablets containing tetraglycine hydroperiodide, also reduces the uptake of radioactive iodine in human subjects to only 2% of the value it would otherwise be. This could be an important factor worthy of consideration for treating water in a recent post nuclear event survival situation, where radioactive iodine ingestion is a concern for internal radiotoxicity. If the iodine has precipitated out of the solution, then the drinking water has less available iodine in the solution. Also the amount of iodine in one tablet is not sufficient to block uptake. Tetraglycine hydroperiodide maintains its effectiveness indefinitely before the container is opened; although some manufacturers suggest not using the tablets more than three months after the container has initially been opened, the shelf life is in fact very long provided that the container is resealed immediately after each time it is opened.
Iodane
Iodane generally refers to any organic derivative of iodine. Without modifier, "iodane" is the systematic name for the parent hydride of iodine, HI. Thus, any organoiodine compound with general formula RI (e.g., CHI or CHI) is a substituted iodane. However, as used in the context of organic synthesis, the term "iodane" more specifically refers to organoiodine compounds with nonstandard bond number (i.e., bond number greater than one), making this term a synonym for hypervalent iodine. These iodine compounds are hypervalent because the iodine atom formally contains more than the 8 electrons in the valence shell required for the octet rule. When iodine is ligated to an organic residue and electronegative ligands (e.g. halides or carboxylates), hypervalent iodine compounds occur with a +3 oxidation number as iodine(III) or λ-iodanes or as a +5 oxidation number as iodine(V) or λ-iodanes. (Here, lambda convention is used to give the nonstandard bond number.)
Iodine trichloride
It is an oxidizing agent, capable of causing fire on contact with organic materials.
Iodine
In 1811, iodine was discovered by French chemist Bernard Courtois, who was born to a manufacturer of saltpetre (an essential component of gunpowder). At the time of the Napoleonic Wars, saltpetre was in great demand in France. Saltpetre produced from French nitre beds required sodium carbonate, which could be isolated from seaweed collected on the coasts of Normandy and Brittany. To isolate the sodium carbonate, seaweed was burned and the ash washed with water. The remaining waste was destroyed by adding sulfuric acid. Courtois once added excessive sulfuric acid and a cloud of purple vapour rose. He noted that the vapour crystallised on cold surfaces, making dark crystals. Courtois suspected that this material was a new element but lacked funding to pursue it further.
Period 6 element
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, Rn, 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 that is radioactive under normal conditions, and is considered a health hazard due to its radioactivity. Intense radioactivity also hindered chemical studies of radon and only a few compounds are known.
Iodine-129
I is one of the seven long-lived fission products that are produced in significant amounts. Its yield is 0.706% per fission (U-235). Larger proportions of other iodine isotopes such as I are produced, but because these all have short half-lives, iodine in cooled spent nuclear fuel consists of about  I and the only stable iodine isotope, I. 
Because I is long-lived and relatively mobile in the environment, it is of particular importance in long-term management of spent nuclear fuel. In a deep geological repository for unreprocessed used fuel, I is likely to be the radionuclide of most potential impact at long times.
Effects of the Chernobyl disaster
Some children in the contaminated areas were exposed to high radiation doses of up to 50 gray (Gy), mostly due to an intake of radioactive iodine-131 (a relatively short-lived isotope with a half-life of 8 days) from contaminated milk produced locally. Several studies have found that the incidence of thyroid cancer among children in Belarus, Ukraine, and Russia has risen sharply since the Chernobyl disaster. The International Atomic Energy Agency (IAEA) notes "1800 documented cases of thyroid cancer in children who were between 0 and 14 years of age when the disaster occurred, which is far higher than normal", although this source fails to note the expected rate. The childhood thyroid cancers that have appeared are of a large and aggressive type but, if detected early, can be treated. Treatment entails surgery followed by iodine-131 therapy for any metastases. To date, such treatment appears to have been successful in the vast majority of cases.
Isobar (nuclide)
The Mattauch isobar rule states that if two adjacent elements on the periodic table have isotopes of the same mass number, (at least) one of these isobars must be a radionuclide (radioactive). In cases of three isobars of sequential elements where the first and last are stable (this is often the case for even-even nuclides, see above), branched decay of the middle isobar may occur; e.g. radioactive iodine-126 has an almost equal probabilities for two decay modes, which lead to different daughter isotopes: tellurium-126 and xenon-126.
Iodine in biology
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for iodine in 2000. For people age 14 and up, the iodine RDA is 150 μg/day; the RDA for pregnant women is 220 μg/day and the RDA during lactation is 290 μg/day. For children 1–8 years, the RDA is 90 μg/day; for children 8–13 years, 130 μg/day. As a safety consideration, the IOM sets tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. The UL for iodine for adults is 1,100 μg/day. This UL was assessed by analyzing the effect of supplementation on thyroid-stimulating hormone. Collectively, the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
Astatine
Less reactive than iodine, astatine is the least reactive of the halogens, although its compounds have been synthesized in microscopic amounts and studied as intensively as possible before their radioactive disintegration. The reactions involved have been typically tested with dilute solutions of astatine mixed with larger amounts of iodine. Acting as a carrier, the iodine ensures there is sufficient material for laboratory techniques (such as filtration and precipitation) to work. Like iodine, astatine has been shown to adopt odd-numbered oxidation states ranging from −1 to +7.
Hyperthyroidism
In iodine-131 (radioiodine) radioisotope therapy, which was first pioneered by Dr. Saul Hertz, radioactive iodine-131 is given orally (either by pill or liquid) on a one-time basis, to severely restrict, or altogether destroy the function of a hyperactive thyroid gland. This isotope of radioactive iodine used for ablative treatment is more potent than diagnostic radioiodine (usually iodine-123 or a very low amount of iodine-131), which has a biological half-life from 8–13 hours. Iodine-131, which also emits beta particles that are far more damaging to tissues at short range, has a half-life of approximately 8 days. Patients not responding sufficiently to the first dose are sometimes given an additional radioiodine treatment, at a larger dose. Iodine-131 in this treatment is picked up by the active cells in the thyroid and destroys them, rendering the thyroid gland mostly or completely inactive.
Period 5 element
Iodine is found on Earth mainly as the highly water-soluble iodide I, which concentrates it in oceans and brine pools. Like the other halogens, free iodine occurs mainly as a diatomic molecule I, and then only momentarily after being oxidized from iodide by an oxidant like free oxygen. In the universe and on Earth, iodine's high atomic number makes it a relatively rare element. However, its presence in ocean water has given it a role in biology (see below).
Nuclear fission product
The short-lived isotopes of iodine are particularly harmful because the thyroid collects and concentrates iodide – radioactive as well as stable. Absorption of radioiodine can lead to acute, chronic, and delayed effects. Acute effects from high doses include thyroiditis, while chronic and delayed effects include hypothyroidism, thyroid nodules, and thyroid cancer. It has been shown that the active iodine released from Chernobyl and Mayak has resulted in an increase in the incidence of thyroid cancer in the former Soviet Union.
Iodine
The antimicrobial action of iodine is quick and works at low concentrations, and thus it is used in operating theatres. Its specific mode of action is unknown. It penetrates into microorganisms and attacks particular amino acids (such as cysteine and methionine), nucleotides, and fatty acids, ultimately resulting in cell death. It also has an antiviral action, but nonlipid viruses and parvoviruses are less sensitive than lipid enveloped viruses. Iodine probably attacks surface proteins of enveloped viruses, and it may also destabilise membrane fatty acids by reacting with unsaturated carbon bonds.
Iodine
Iodine oxides are the most stable of all the halogen oxides, because of the strong I–O bonds resulting from the large electronegativity difference between iodine and oxygen, and they have been known for the longest time. The stable, white, hygroscopic iodine pentoxide (IO) has been known since its formation in 1813 by Gay-Lussac and Davy. It is most easily made by the dehydration of iodic acid (HIO), of which it is the anhydride. It will quickly oxidise carbon monoxide completely to carbon dioxide at room temperature, and is thus a useful reagent in determining carbon monoxide concentration. It also oxidises nitrogen oxide, ethylene, and hydrogen sulfide. It reacts with sulfur trioxide and peroxydisulfuryl difluoride (SOF) to form salts of the iodyl cation, [IO], and is reduced by concentrated sulfuric acids to iodosyl salts involving [IO]. It may be fluorinated by fluorine, bromine trifluoride, sulfur tetrafluoride, or chloryl fluoride, resulting iodine pentafluoride, which also reacts with iodine pentoxide, giving iodine(V) oxyfluoride, IOF. A few other less stable oxides are known, notably IO and IO; their structures have not been determined, but reasonable guesses are I(IO) and [IO][IO] respectively.
More important are the four oxoacids: hypoiodous acid (HIO), iodous acid (HIO), iodic acid (HIO), and periodic acid (HIO or HIO). When iodine dissolves in aqueous solution, the following reactions occur:
Carbonyl oxidation with hypervalent iodine reagents
The mechanism of carbonyl oxidation by iodine(III) reagents varies as a function of substrate structure and
reaction conditions, but some generalizations are possible. Under basic conditions, the active iodinating species are iodine(III) compounds in which any relatively acidic ligands on iodine (such as acetate) have been replaced by alkoxide. In all cases, the α carbon forms a bond to
iodine. Reduction of iodine(III) to iodine(I) then occurs via attack of a nucleophile on the now electrophilic α
carbon. Under basic conditions, nucleophilic attack at the carbonyl carbon is faster than attack at the α carbon. Iodine
displacement is actually accomplished intramolecularly by the carbonyl oxygen, which becomes the α-hydroxyl oxygen in the
product.
Iodine-131
Due to its mode of beta decay, iodine-131 is notable for causing mutation and death in cells that it penetrates, and other cells up to several millimeters away. For this reason, high doses of the isotope are sometimes less dangerous than low doses, since they tend to kill thyroid tissues that would otherwise become cancerous as a result of the radiation. For example, children treated with moderate dose of I-131 for thyroid adenomas had a detectable increase in thyroid cancer, but children treated with a much higher dose did not. Likewise, most studies of very-high-dose I-131 for treatment of Graves disease have failed to find any increase in thyroid cancer, even though there is linear increase in thyroid cancer risk with I-131 absorption at moderate doses. Thus, iodine-131 is increasingly less employed in small doses in medical use (especially in children), but increasingly is used only in large and maximal treatment doses, as a way of killing targeted tissues. This is known as "therapeutic use".
Iodic acid
Iodic acid, HIO, can be obtained as a white or off-white solid. It dissolves in water very well, but it also exists in the pure state, as opposed to chloric acid or bromic acid. Iodic acid contains iodine in the oxidation state +5 and is one of the most stable oxo-acids of the halogens in its pure state. When iodic acid is carefully heated, it dehydrates to iodine pentoxide. On subsequent heating, the iodine pentoxide further decomposes, giving a mix of iodine, oxygen and lower oxides of iodine.
Committed dose
The intake of radioactive material can occur through four pathways:Some artificial radioisotopes such as iodine-131 are chemically identical to natural isotopes needed by the body, and may be more readily absorbed if the individual has a deficit of that element. For instance, Potassium iodide (KI), administered orally immediately after exposure, may be used to protect the thyroid from ingested radioactive iodine in the event of an accident or attack at a nuclear power plant, or the detonation of a nuclear explosive which would release radioactive iodine.
Iodine value
The iodine value (or iodine adsorption value or iodine number or iodine index) in chemistry is the mass of iodine in grams that is consumed by 100 grams of a chemical substance. Iodine numbers are often used to determine the amount of unsaturation in fatty acids. This unsaturation is in the form of double bonds, which react with iodine compounds. The higher the iodine number, the more C=C bonds are present in the fat. It can be seen from the table that coconut oil is very saturated, which means it is good for making soap. On the other hand, linseed oil is highly unsaturated, which makes it a drying oil, well suited for making oil paints.
Iodine-123
The Auger electrons from the radioisotope have been found in one study to do little cellular damage, unless the radionuclide is incorporated chemically directly into cellular DNA, which is not the case for present radiopharmaceuticals which use I-123 as the radioactive label nuclide. The damage from the more penetrating gamma radiation and 127 keV internal conversion electron radiation from the initial decay of Te-123 is moderated by the relatively short half-life of the isotope.
Hydraulic fracturing and radionuclides
As radon decays, it produces radioactive decay products. If the contaminated dust of these "radon daughters" are inhaled, they can lodge in the lungs and increase the risk of developing lung cancer. Iodine in food is absorbed by the body and preferentially concentrated in the thyroid where it is needed for the functioning of that gland. When Iodine-131 is present in high levels in the environment from hydraulic fracturing flowback and blowouts, it can be absorbed through contaminated food and water, and will also accumulate in the thyroid. As it decays, it may cause damage to the thyroid. The primary risk from exposure to high levels of iodine-131 is the chance occurrence of radiogenic thyroid cancer in later life. Other risks include the possibility of non-cancerous growths and thyroiditis. The level of radiation in hydraulic fracturing wastewater has been measured to be as high as 18,035 pCi/L, thousands of times the maximum allowed by the federal standard for drinking water, and there are concerns about radiation exposure during spills and blowouts. Long term exposure to low level radiation is associated with stochastic health effects; the greater the exposure, the more likely the health effects are to occur. A group of doctors from the United States have called for a moratorium on hydraulic fracturing until health effects are more thoroughly studied.
Iodine
The caliche was the main source of iodine in the 19th century and continues to be important today, replacing kelp (which is no longer an economically viable source), but in the late 20th century brines emerged as a comparable source. The Japanese Minami Kanto gas field east of Tokyo and the American Anadarko Basin gas field in northwest Oklahoma are the two largest such sources. The brine is hotter than 60 °C from the depth of the source. The brine is first purified and acidified using sulfuric acid, then the iodide present is oxidised to iodine with chlorine. An iodine solution is produced, but is dilute and must be concentrated. Air is blown into the solution to evaporate the iodine, which is passed into an absorbing tower where sulfur dioxide reduces the iodine. The hydrogen iodide (HI) is reacted with chlorine to precipitate the iodine. After filtering and purification the iodine is packed.
Isotopes of iodine
Due to preferential uptake of iodine by the thyroid, radioiodine is extensively used in imaging of and, in the case of I-131, destroying dysfunctional thyroid tissues. Other types of tissue selectively take up certain iodine-131-containing tissue-targeting and killing radiopharmaceutical agents (such as MIBG). Iodine-125 is the only other iodine radioisotope used in radiation therapy, but only as an implanted capsule in brachytherapy, where the isotope never has a chance to be released for chemical interaction with the body's tissues.
Iodine-123
I is the most suitable isotope of iodine for the diagnostic study of thyroid diseases. The half-life of approximately 13.13 hours is ideal for the 24-hour iodine uptake test and I has other advantages for diagnostic imaging thyroid tissue and thyroid cancer metastasis. The energy of the photon, 159 keV, is ideal for the NaI (sodium iodide) crystal detector of current gamma cameras and also for the pinhole collimators. It has much greater photon flux than I. It gives approximately 20 times the counting rate of I for the same administered dose. The radiation burden to the thyroid is far less (1%) than that of I. Moreover, scanning a thyroid remnant or metastasis with I does not cause "stunning" of the tissue (with loss of uptake), because of the low radiation burden of this isotope. (For the same reasons, I is never used for thyroid cancer or Graves disease "treatment", and this role is reserved for I.)
Halogen
There are two stable and naturally occurring isotopes of bromine, bromine-79 and bromine-81. A total of 32 isotopes of bromine have been discovered, with atomic masses ranging 67 to 98. There is one stable and naturally occurring isotope of iodine, iodine-127. However, there are trace amounts in nature of the radioactive isotope iodine-129, which occurs via spallation and from the radioactive decay of uranium in ores. Several other radioactive isotopes of iodine have also been created naturally via the decay of uranium. A total of 38 isotopes of iodine have been discovered, with atomic masses ranging from 108 to 145.
Iodine
Of the thirty-seven known isotopes of iodine, only one occurs in nature, iodine-127. The others are radioactive and have half-lives too short to be primordial. As such, iodine is monoisotopic and its atomic weight is known to great precision, as it is a constant of nature.
Povidone-iodine
Povidone-iodine (PVP-I), also known as iodopovidone, is an antiseptic used for skin disinfection before and after surgery. It may be used both to disinfect the skin of the patient and the hands of the healthcare providers. It may also be used for minor wounds. It may be applied to the skin as a liquid or a powder.
Side effects include skin irritation. If used on large wounds kidney problems, high blood sodium, and metabolic acidosis may occur. It is not recommended in people who are less than 32 weeks pregnant or are taking lithium. Frequent use is not recommended in people with thyroid problems. Povidone-iodine is a chemical complex of povidone, hydrogen iodide, and elemental iodine. It contains from 9% to 12% available iodine. It works by releasing iodine which results in the death of a range of microorganisms.
Povidone-iodine came into commercial use in 1955. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. Povidone-iodine is available over the counter. The wholesale cost in the developing world is about 3.30 to 11.40 per liter of 10% solution. This amount in the United Kingdom cost the NHS about £10.86. It is sold under a number of brand names including Betadine.
Iodine-125
Iodine-125 (I) is a radioisotope of iodine which has uses in biological assays, nuclear medicine imaging and in radiation therapy as brachytherapy to treat a number of conditions, including prostate cancer, uveal melanomas, and brain tumors. It is the second longest-lived radioisotope of iodine, after iodine-129.
Iodine
Iodine is the fourth halogen, being a member of group 17 in the periodic table, below fluorine, chlorine, and bromine; it is the heaviest stable member of its group. (The scarce and fugitive fifth halogen, the radioactive astatine, is not well-studied due to its expense and inaccessibility in large quantities, but appears to show various unusual properties due to relativistic effects.) Iodine has an electron configuration of [Kr]4d5s5p, with the seven electrons in the fifth and outermost shell being its valence electrons. Like the other halogens, it is one electron short of a full octet and is hence a strong oxidising agent, reacting with many elements in order to complete its outer shell, although in keeping with periodic trends, it is the weakest oxidising agent among the stable halogens: it has the lowest electronegativity among them, just 2.66 on the Pauling scale (compare fluorine, chlorine, and bromine at 3.98, 3.16, and 2.96 respectively; astatine continues the trend with an electronegativity of 2.2). Elemental iodine hence forms diatomic molecules with chemical formula I, where two iodine atoms share a pair of electrons in order to each achieve a stable octet for themselves; at high temperatures, these diatomic molecules reversibly dissociate a pair of iodine atoms. Similarly, the iodide anion, I, is the strongest reducing agent among the stable halogens, being the most easily oxidised back to diatomic I. (Astatine goes further, being indeed unstable as At and readily oxidised to At or At, although the existence of At is not settled.)
Halogen
Iodine is somewhat toxic, being able to irritate the lungs and eyes, with a safety limit of 1 milligram per cubic meter. When taken orally, 3 grams of iodine can be lethal. Iodide anions are mostly nontoxic, but these can also be deadly if ingested in large amounts.
Nuclear fission product
The administration of known goitrogen substances can also be used as a prophylaxis in reducing the bio-uptake of iodine, (whether it be the nutritional non-radioactive iodine-127 or radioactive iodine, radioiodine - most commonly iodine-131, as the body cannot discern between different iodine isotopes).
Perchlorate ions, a common water contaminant in the USA due to the aerospace industry, has been shown to reduce iodine uptake and thus is classified as a goitrogen. Perchlorate ions are a competitive inhibitor of the process by which iodide is actively deposited into thyroid follicular cells. Studies involving healthy adult volunteers determined that at levels above 0.007 milligrams per kilogram per day (mg/(kg·d)), perchlorate begins to temporarily inhibit the thyroid gland’s ability to absorb iodine from the bloodstream ("iodide uptake inhibition", thus perchlorate is a known goitrogen).
The reduction of the iodide pool by perchlorate has dual effects – reduction of excess hormone synthesis and hyperthyroidism, on the one hand, and reduction of thyroid inhibitor synthesis and hypothyroidism on the other. Perchlorate remains very useful as a single dose application in tests measuring the discharge of radioiodide accumulated in the thyroid as a result of many different disruptions in the further metabolism of iodide in the thyroid gland.
Radioactivity in the life sciences
Iodine-125 is commonly used for labeling proteins, usually at tyrosine residues. Unbound iodine is volatile and must be handled in a fume hood. Its maximum specific activity is 2,176 Ci/mmol (80.51 PBq/mol).
United States Atomic Energy Commission
The AEC had a history of involvement in experiments involving radioactive iodine. In a 1949 operation called the "Green Run," the AEC released iodine-131 and xenon-133 to the atmosphere which contaminated a area containing three small towns near the Hanford site in Washington. In 1953, the AEC ran several studies on the health effects of radioactive iodine in newborns and pregnant women at the University of Iowa. Also in 1953, the AEC sponsored a study to discover if radioactive iodine affected premature babies differently from full-term babies. In the experiment, researchers from Harper Hospital in Detroit orally administered iodine-131 to 65 premature and full-term infants who weighed from . In another AEC study, researchers at the University of Nebraska College of Medicine fed iodine-131 to 28 healthy infants through a gastric tube to test the concentration of iodine in the infants' thyroid glands.
Iodoacetic acid
Iodide is a naturally occurring ion that can be found in many source waters and it is easily oxidized by wastewater disinfectants. One of the products of iodide oxidation is hypoiodous acid (HOI or OI) which is capable of reacting with background organic materials to generate iodinated disinfection by-products (DBPs) including iodoacetic acid. In a study performed by Plewa, et al., IAA was determined to be one of the most cytotoxic of those studied, with a median lethal dose on the order of magnitude of 10 M. It was the most genotoxic of more than 60 DBPs studied and is the most genotoxic DBP identified thus far. Iodoacetic acid has exhibited traits indicating it as a potential carcinogen, however, it has not been proven to be carcinogenic. The trend continues in teratogenicity, with iodoacetic acid’s potency surpassing that of its brominated and chlorinated analogs. Its toxicity correlates to its ability as an alkylating agent, which will modify cysteine residues in proteins. Monohaloacetic acids are the most toxic, with toxicity increasing with halogen size. Iodoacetic acid is more toxic than bromoacetic acid and much more toxic than chloroacetic acid.
Iodine
The usual means of protection against the negative effects of iodine-131 is by saturating the thyroid gland with stable iodine-127 in the form of potassium iodide tablets, taken daily for optimal prophylaxis. However, iodine-131 may also be used for medicinal purposes in radiation therapy for this very reason, when tissue destruction is desired after iodine uptake by the tissue. Iodine-131 is also used as a radioactive tracer.
Iodine in biology
Elemental iodine (I) is poisonous if taken orally in large amounts; 2–3 grams is a lethal dose for an adult human. Potassium iodide, on the other hand, has a median lethal dose (LD) that is relatively high in several other animals: in rabbits, it is 10 g/kg; in rats, 14 g/kg, and in mice, 22 g/kg. The tolerable upper intake level for iodine as established by the Food and Nutrition Board is 1,100 µg/day for adults. The safe upper limit of consumption set by the Ministry of Health, Labor and Welfare in Japan is 3,000 µg/day.
Iodine
Many periodates are known, including not only the expected tetrahedral , but also square-pyramidal , octahedral orthoperiodate , [IO(OH)], [IO(OH)], and . They are usually made by oxidising alkaline sodium iodate electrochemically (with lead(IV) oxide as the anode) or by chlorine gas:
Iodine (medical use)
Iodine is used to treat and prevent iodine deficiency and as an antiseptic. For iodine deficiency it can be given by mouth or injection into a muscle. As an antiseptic it may be used on wounds that are wet or to disinfect the skin before surgery.
Common side effects when applied to the skin include irritation and discoloration. When taken by mouth or injection side effects may include allergic reactions, goitre, and thyroid dysfunction. Use during pregnancy is recommended in regions where deficiency is common, otherwise it is not recommended. Iodine is an essential trace element.
In 1811, Bernard Courtois isolated iodine from seaweed while in 1820 Jean-Francois Coindet linked iodine intake to goiter size. It initially came into use as a disinfectant and for goiter. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. Table salt with iodine, known as iodized salt, is available in more than 110 countries. In areas with low dietary iodine one dose of iodine a year at 0.32 USD per dose may be recommended.
Iodine
When iodine dissolves in strong acids, such as fuming sulfuric acid, a bright blue paramagnetic solution including cations is formed. A solid salt of the diiodine cation may be obtained by oxidising iodine with antimony pentafluoride:
The salt ISbF is dark blue, and the blue tantalum analogue ITaF is also known. Whereas the I–I bond length in I is 267 pm, that in is only 256 pm as the missing electron in the latter has been removed from an antibonding orbital, making the bond stronger and hence shorter. In fluorosulfuric acid solution, deep-blue reversibly dimerises below −60 °C, forming red rectangular diamagnetic . Other polyiodine cations are not as well-characterised, including bent dark-brown or black and centrosymmetric "C" green or black , known in the and salts among others.
Iodine
These sources ensure that Chile and Japan are the largest producers of iodine today. Alternatively, the brine may be treated with silver nitrate to precipitate out iodine as silver iodide, which is then decomposed by reaction with iron to form metallic silver and a solution of iron(II) iodide. The iodine may then be liberated by displacement with chlorine.
Chernobyl disaster
Like many other releases of radioactivity into the environment, the Chernobyl release was controlled by the physical and chemical properties of the radioactive elements in the core. Particularly dangerous are the highly radioactive fission products, those with high nuclear decay rates that accumulate in the food chain, such as some of the isotopes of iodine, caesium and strontium. Iodine-131 and caesium-137 are responsible for most of the radiation exposure received by the general population.
Uranium
Normal functioning of the kidney, brain, liver, heart, and other systems can be affected by uranium exposure, because, besides being weakly radioactive, uranium is a toxic metal. Uranium is also a reproductive toxicant. Radiological effects are generally local because alpha radiation, the primary form of U decay, has a very short range, and will not penetrate skin. Alpha radiation from inhaled uranium has been demonstrated to cause lung cancer in exposed nuclear workers. Uranyl () ions, such as from uranium trioxide or uranyl nitrate and other hexavalent uranium compounds, have been shown to cause birth defects and immune system damage in laboratory animals. While the CDC has published one study that no human cancer has been seen as a result of exposure to natural or depleted uranium, exposure to uranium and its decay products, especially radon, are widely known and significant health threats. Exposure to strontium-90, iodine-131, and other fission products is unrelated to uranium exposure, but may result from medical procedures or exposure to spent reactor fuel or fallout from nuclear weapons.
Although accidental inhalation exposure to a high concentration of uranium hexafluoride has
resulted in human fatalities, those deaths were associated with the generation of highly toxic hydrofluoric acid and uranyl fluoride rather than with uranium itself. Finely divided uranium metal presents a fire hazard because uranium is pyrophoric; small grains will ignite spontaneously in air at room temperature.
Iodine pentoxide
Iodine pentoxide is the chemical compound with the formula IO. This iodine oxide is the anhydride of iodic acid, and the only stable oxide of iodine. It is produced by dehydrating iodic acid at 200 °C in a stream of dry air: