Polonium-210: Why Is Po-210 So Poisonous? - Medical News Today Polonium-210: Why Is Po-210 So Poisonous? 4.5 43 4 Polonium-210 is familiar to most people as the deadly poison used to kill Alexander Litvinenko, an MI6 agent and former Soviet and Russian spy who succumbed to radiation sickness in London in the UK in November 2006. While polonium-210 is highly dangerous, it may surprise some to know that this radioactive material is found naturally in the human body due to low levels in the normal environment.1,2 Tobacco smokers also accumulate polonium isotope 210 in their lungs, and the radioactive substance is also present in the food chain, especially in seafood. It is alleged that Litvinenko ingested a fatal dose of Po-210 by drinking tea at a business meeting with two other Russians, both of whom have been charged with his murder.

3,4,21 Several locations in London, including a restaurant and nightclub, were closed by authorities during the investigation amid fears of potential public exposure to Po-210.20 Litvinenko's autopsy was a complicated process involving multiple safety measures to avoid contamination with radioactive material. Some 700 or so people were thought to have been exposed to polonium-210 connected to Litvinenko's death, but none experienced serious sickness.21 An inquiry into Litvinenko's death was established by the British government and is ongoing, with public court hearings having commenced at the end of January 2015.5,21 Most recently, a world-leading expert in theoretical physics told the inquiry that the polonium-210 in this case could only have come from a specific closed nuclear facility in Sarov, Russia.22 Use this page to discover what polonium-210 is and how the radioactive material - one of the most toxic substances known to humankind6 - poses its threat as a poison and weapon of terror. Contents of this article: British inquiry into Litvinenko's death Fast facts on polonium-210 Here are some key points about polonium-210.

More detail and supporting information is in the body of this article. Polonium-210 is a rare radioactive metal discovered by Marie Curie in the late 19th century. It has a half-life of 138 days, decaying to lead. During its radioactive decay, polonium-210 emits alpha particles. The alpha particles are a very high-energy form of radiation but do not travel far - they can be blocked by a few sheets of paper, and lose all their energy after travelling through a few centimeters of air. Polonium-210 is poisonous only once it has entered the body, where it is powerful and deadly, even at doses of less than a microgram. By mass, polonium-210 is one of the deadliest toxins. It is around 250,000 times more toxic than hydrogen cyanide - the lethal dose of which is 250 milligrams. It would be very difficult to obtain polonium for poisoning, necessitating access to a nuclear reactor. But once acquired, polonium is relatively safe to transport and hide from detection.

Unlike most radioactive substances, polonium-210 emits alpha radiation rather than gamma radiation, which is why it is not detected by Geiger counters. Polonium-210 becomes poisonous when it is breathed in, swallowed, or otherwise enters the body, such as through broken skin. A high enough dose of polonium by mouth will lead to acute radiation syndrome - the severity of which, and time to illness and death, depends on the amount of radioactive material absorbed. The liver, bone marrow and other soft tissues are particularly sensitive to the effects of polonium. Acute radiation syndrome presents as vomiting, hair loss , and reductions in white blood cells. Specialist radiation detectors are needed to diagnose contamination with polonium-210. Treatment is limited to supportive care against the effects of the radiation, although chelation agents may be able to help eliminate polonium if a case of poisoning is identified early enough. The prognosis in a case of polonium-210 poisoning depends largely on the amount of radiation absorbed by the body. Former spy Alexander Litvinenko was assassinated by polonium poisoning in London in 2006. British police identified that the polonium-210 had been introduced via a teapot.

What is polonium-210?7-9 Polonium is a radioactive chemical element (atomic number 84) that was discovered in 1898 by Marie Curie. Polonium is one of the most toxic substances known to humankind. Being a Polish chemist, Curie named the element after her home country, and her discovery won her the Nobel Prize in Chemistry in 1911, which was also a recognition of her discovery of another element, radium.10 In its natural state at room temperature, polonium is a solid metal with a silver color. Polonium-210 is one of 25 known radioactive isotopes of polonium and it has a half-life of 138 days (meaning half its radioactivity dies away in this time), decaying into a new, stable metal - lead. Polonium is very rare, as Marie Curie found when she discovered it in a source of uranium known as pitchblende. As little as about 100 micrograms (0.0001 grams) of polonium occurs in one ton of uranium ore.

Curie's pioneering work, however, produced enough polonium to fatally expose her daughter Irène in a lab accident in 1946 - she went on to suffer leukemia , dying in 1956 at the age of 58.11 Modern production of the substance is usually done by creating another radioactive element in a nuclear reactor, which itself then decays to polonium-210. Polonium-210 is abbreviated to Po-210, (210)Po, or 210Po. Beneficial uses of polonium include: Insulating instruments in Russian lunar landing craft - polonium decay generates significant heat relative to its light weight Application in commercial devices to remove static electricity, in which polonium is usually electroplated onto other metals Inspecting oil wells (using the same principles as when using polonium to trigger nuclear weapons) To measure the thickness of industrial coatings (through alpha radiation attenuation). How dangerous is polonium-210? Hydrogen cyanide is well known to be highly poisonous, but is far less toxic than polonium-210.

Matched milligram for milligram, polonium-210 is 250 billion times more toxic.8,11 This makes polonium-210 one of the most toxic substances known to man.6 Toxicologists estimate that one gram of polonium could be enough to kill 50 million people, on top of another 50 million who would become ill; in the case of Litvinenko, less than one millionth of that amount would have been enough to cause his death (less than a microgram).8 How could an assassin use polonium-210 for poisoning? Clearly, polonium-210 is extremely dangerous - but it is also extremely difficult to obtain.

Its commercial application onto devices that remove static has largely been replaced by non-radioactive technology and is done in such a way that it is infeasible to separate the polonium for use as a poison.9,12 Even buying pure polonium from legitimate sources would not be feasible since it is sold in such tiny quantities - 15,000 orders would have to be placed to enable enough for poisoning.9,12 If a person was to acquire some polonium, say from a nuclear industrial process, it is not particularly dangerous to carry around as its high-energy radiation can be blocked by a relatively thin barrier for a radioactive material. Polonium-210 is unable to penetrate the epidermis (the skin), and is blocked by just a few sheets of thin paper. Additionally, alpha particles usually lose all their energy after traveling through a few centimeters of air.11,13 The rapid application and damaging effects of polonium-210, added to its relatively safe transportation and minimal risk of detection make it an attractive potential poison.

The perpetrator(s) of Alexander Litvinenko's murder by polonium poisoning would have needed access to "a reactor capable of producing and irradiating materials, and a radiochemical laboratory," according to quotes in New Scientist from Professor Nick Priest, one of few UK experts to have worked with polonium-210.3 Speaking at the British inquiry into Litvinenko's death, Norman Dombey, emeritus professor of theoretical physics at the University of Sussex, said the polonium used was produced at a closed nuclear facility in the city of Sarov, 450 miles south-east of Moscow.22 This Soviet-era plant (known as Avangard) was the only place in the world with a polonium production line, and the last remaining source of commercial polonium. The US and UK stopped making polonium in the 1970s as did all other countries. Dombey also told the inquiry that the dose of polonium used to kill Litvinenko was exceptionally large (26.5 micrograms).22 He determined that polonium was likely used in this case because it is unlikely to be detected, given that it emits alpha radiation rather than the gamma radiation emitted by most radioactive materials.

This means that the poison is unlikely to be detected. Indeed, it was only hours before Litvinenko's death that polonium-210 was discovered as the poison that was killing him. In all likelihood, Dombey says, the polonium-210 came from Avangard, after having started out as irradiated bismuth in the Mayak nuclear reactor in the Urals. 22 To convert the metallic polonium-210 into liquid form, Dombey says that a "state institution" would have had to be involved, before the two Russians charged with Litvinenko's murder would have had to smuggle it to London.22 Polonium has a half-life of just 138 days, meaning that it loses half of its radioactivity in that time.

The 138 days for polonium-210 to lose half of its radioactivity means that the specimen used to kill Litvinenko would need to have been made relatively recently.9,11 Finally, when polonium-210 has reached its target, the poison must be introduced into the body to do its fatal damage internally.8,11 The high-energy alpha particles are harmless externally - they are blocked by a few sheets of paper, or the top layer of the skin, the epidermis. But deadly tissue damage can be done via:8,13 Inhalation Ingestion, or Entry through skin abrasions or wounds. Alexander Litvinenko is thought to have ingested the polonium via a cup of tea, which would have hidden the heat generated by the radioisotope. How does polonium poison humans? Polonium-210 does not itself have toxic chemical properties - the danger comes purely from the radiation it emits. But the alpha particles have a very short range across biological tissue.

This is a tiny fraction of a millimeter (40-50 microns or 0.04-0.05 mm), and the particles are stopped by the top layer of the skin.6 Before polonium-210 becomes dangerous to the human body, it must therefore be introduced internally. This can be through broken skin or through inhalation of ingestion by mouth, as in the Litvinenko case. Before the 2006 assassination, polonium-210 was considered to be a highly unlikely murder method.

However, since the event, there has been an increase in expert literature on this kind of poisoning.14 After oral ingestion, polonium-210 is initially concentrated in red blood cells, followed by the liver, kidneys, bone marrow, gastrointestinal tract, and gonads (testicles or ovaries).6 By mouth, polonium-210 is absorbed more readily than some other alpha-emitting radionuclides.8 Once absorbed into the blood, polonium is then distributed through the body mainly in soft tissues and roughly as follows:6,8 30% to the liver 10% to red bone marrow 10% to the kidney 5% to the spleen The remainder to the wider body, including the skin, particularly the hair follicles.

Polonium is a group 1 carcinogen - that is, it is known to cause cancer , rather than merely being suspected as a carcinogen.6 When inhaled, for example, polonium-210 causes lung cancer .13 Environmental levels of polonium are extremely low and harmless to human health, and very low levels of the substance are found naturally in the body (tobacco plants concentrate the radioisotope though - so smokers have higher levels).1 In sufficient amounts, polonium can be lethal within days or weeks. Polonium poisoning typically presents as unexplained vomiting, followed by bone marrow failure and hair loss. Different organs and tissues greatly vary in their sensitivity to the alpha radiation damage, with the blood-making (hematopoietic) tissue in the bone marrow, and the lining of the gut especially vulnerable.8 The bone marrow failure seen in polonium poisoning is accompanied by damage to other organs where polonium-210 concentrations are high, meaning that transfusions to rescue the bone marrow may not be enough to save someone.15 Why is alpha radiation so toxic?

As polonium is distributed around the body, it leaves a trail of reactive radicals because it steals electrons from any molecule in its path.9 Damage to DNA from the alpha particle radiation can cause apoptosis ''" cell suicide - and even low-level DNA damage can cause genetic changes that affect cellular replication.9 How much polonium is needed to cause death? Scientists have a number of ways to quantify amounts of radiation exposure. Polonium is extremely dangerous when inhaled, ingested, or introduced through broken skin. It is relatively safe to transport though, and its radiation will not penetrate the top layer of the skin.

The radiation given off (emitted) by a quantity of polonium is measured in Becquerels (Bq), a unit that describes the rate at which a radioactive material decays in terms of the number of disintegrations of its nucleus per second; a gigabecquerel (GBq) is 100,000,000 disintegrations per second.16 The amount of radiation absorbed by the tissues, meanwhile, is measured in gray units (Gy); the absorption of one joule of radiation energy per one kilogram of matter.16 Scientists estimate that the equivalent of between 0.1-0.3 GBq or more of polonium absorbed into the blood of an adult male would likely prove fatal within one month.15 Assuming 10% of ingested polonium would be absorbed into the blood, 1-3 GBq or more would need to be swallowed for the poison to be deadly15; just a few micrograms of polonium would be enough to kill someone.3 On the next page, we look at the diagnosis, symptoms and treatment of polonium poisoning.

Polonium - Wikipedia, the free encyclopedia Polonium References Polonium ( IPA : /pə(ʊ)ˈləʊniəm/) is a chemical element in the periodic table that has the symbol Po and atomic number 84. A rare and highly radioactive metalloid [1] , polonium is chemically similar to tellurium and bismuth , and it occurs in uranium ores . Polonium has been studied for possible use in heating spacecraft . It is unstable; all isotopes of polonium are radioactive. Contents [ edit ] Applications When it is mixed or alloyed with beryllium , polonium can be a neutron source : beryllium releases a neutron upon absorption of an alpha particle that is supplied by 210Po. It has been used in this capacity as a neutron trigger or initiator for nuclear weapons . Other uses include Devices that eliminate static charges in textile mills and other places. [2] However, beta particle sources are more commonly used and are less dangerous. A non-radioactive alternative is to use a high-voltage DC power supply to ionise air positively or negatively as required.

[3] 210Po can be used as an atomic heat source to power radioisotope thermoelectric generators via thermoelectric materials. Because of its very high toxicity, Polonium can be used as a poison (see, for example, Alexander Litvinenko poisoning ). [ edit ] History Also called tentatively "Radium F", polonium was discovered by Marie Skłodowska-Curie and her husband Pierre Curie in 1898 [4] and was later named after Marie Curie's native land of Poland ( Latin : Polonia). [5] [6] Poland at the time was under Russian, Prussian, and Austrian partition , and did not exist as an independent country. It was Curie's hope that naming the element after her native land would publicize its lack of independence. Polonium may be the first element named to highlight a political controversy. [7] Poland became an independent country again in 1918, following World War I . This element was the first one discovered by the Curies while they were investigating the cause of pitchblende radioactivity .

The pitchblende, after removal of the radioactive elements uranium and thorium , was more radioactive than both the uranium and thorium put together. This spurred the Curies on to find additional radioactive elements. The Curies first separated out polonium from the pitchblende, and then within a few years, also isolated radium . [ edit ] Occurrence Polonium is a very rare element in nature because of the short half-life of all its isotopes. It is found in uranium ores at about 100 micrograms per metric ton (1 part in 1010), which is approximately 0.2% of the abundance of radium. The amounts in the Earth's crust are not harmful. Polonium has been found in tobacco smoke from tobacco leaves grown with phosphate fertilizers. [8] [9] [ edit ] Synthesis by (n,γ) reaction In 1934 an experiment showed that when natural 209Bi is bombarded with neutrons , 210Bi is created, which then decays to 210Po via β decay. Polonium may now be made in milligram amounts in this procedure which uses high neutron fluxes found in nuclear reactors .

Only about 100 grams are produced each year, practically all of it in Russia, making polonium exceedingly rare. [10] [11] [ edit ] Synthesis by (p, n) and (p,2n) reactions It has been found that the longer lived isotopes of polonium can be formed by proton bombardment of bismuth using a cyclotron . Other more neutron rich isotopes can be formed by the irradiation of platinum with carbon nuclei. [12] [ edit ] Isotopes Polonium has 25 known isotopes , all of which are radioactive . They have atomic masses that range from 194u to 218u. 210Po is the most widely available. 209Po (half-life 103 years) and 208Po (half-life 2.9 years) can be made through the alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron .

[ edit ] 210Po 210Po is an alpha emitter that has a half-life of 138.376 days; it decays directly to its daughter isotope 206Pb . A milligram of 210Po emits as many alpha particles per second as 4.215 grams of 226Ra . A few curies (1 curie equals 37 gigabecquerels ) of 210Po emit a blue glow which is caused by excitation of surrounding air. A single gram of 210Po generates 140 watts of power. [13] Because it emits many alpha particles , which are stopped within a very short distance in dense media and release their energy, 210Po has been used as a lightweight heat source to power thermoelectric cells in artificial satellites ; for instance, 210Po heat source was also used in each of the Lunokhod rovers deployed on the surface of the Moon , to keep their internal components warm during the lunar nights.

[14] Some anti-static brushes contain up to 500 microcuries of 210Po as a source of charged particles for neutralizing static electricity in materials like photographic film. [15] The majority of the time 210Po decays by emission of an alpha particle only, not by emission of an alpha particle and a gamma ray . About one in 100,000 decays results in the emission of a gamma ray. [16] This low gamma ray production rate makes it more difficult to find and identify this isotope. Rather than gamma ray spectroscopy, alpha spectroscopy is the best method of measuring this isotope. [ edit ] Chemical characteristics The chemistry of polonium is similar to that of tellurium and bismuth . Polonium dissolves readily in dilute acids , but is only slightly soluble in alkalis . The hydrogen compound PoH2 is liquid at room temperature ( M.P. -36.1°C to B.P. 35.3°C). Halides of the structure PoX2, PoX4 and PoX6 are known. The two oxides PoO2 and PoO3 are the products of oxidation of polonium.

[17] 210Po (in common with 238Pu ) has the ability to become airborne with ease : if a sample is heated in air to 328 K (55°C, 131°F), 50% of it is vaporized in 45 hours, even though the melting point of polonium is 527 K (254°C, 489°F) and its boiling point is 1235 K (962°C, 1763°F). [18] More than one hypothesis exists for how polonium does this; one suggestion is that small clusters of polonium atoms are spalled off by the alpha decay. It has been reported that some microbes can methylate polonium by the action of methylcobalamin . [19] [20] This is similar to the way in which mercury , selenium and tellurium are methylated in living things to create organometallic compounds. As a result when considering the biochemistry of polonium one should consider the possibility that the polonium will follow the same biochemical pathways as selenium and tellurium. The alpha form of solid polonium.

[ edit ] Solid state form The alpha form of solid polonium has a simple cubic crystal structure with an edge length of 3.352 Å. The beta form of polonium is rhombohedral ; it has been reported in the chemical literature, along with the alpha form, several times. A picture of it is present on the web. [21] Two papers report X-ray diffraction experiments on polonium metal. [22] [23] The first report of the crystal structure of polonium was done using electron diffraction . [24] [ edit ] Gamma counting By means of radiometric methods such as gamma spectroscopy (or a method using a chemical separation followed by an activity measurement with a non-energy-dispersive counter), it is possible to measure the concentrations of radioisotopes and to distinguish one from another. In practice, background noise would be present and depending on the detector, the line width would be larger which would make it harder to identify and measure the isotope . In biological/medical work it is common to use the natural 40K present in all tissues/body fluids as a check of the equipment and as an internal standard.

Intensity against alpha energy for four isotopes, note that the line width is narrow and the fine details can be seen Intensity against alpha energy for four isotopes, note that the line width is wide and some of the fine details can not be seen. This is for liquid scintillation counting where random effects cause a variation in the number of visible photons generated per alpha decay [ edit ] Alpha counting The best way to test for (and measure) many alpha emitters is to use alpha-particle spectroscopy as it is common to place a drop of the test solution on a metal disk which is then dried out to give a uniform coating on the disk. This is then used as the test sample. If the thickness of the layer formed on the disk is too thick then the lines of the spectrum are broadened, this is because some of the energy of the alpha particles is lost during their movement through the layer of active material. An alternative method is to use internal liquid scintillation where the sample is mixed with a scintillation cocktail. When the light emitted is then counted, some machines will record the amount of light energy per radioactive decay event.

Due to the imperfections of the liquid scintillation method (such as a failure for all the photons to be detected, cloudy or coloured samples can be difficult to count) and the fact that random quenching can reduce the number of photons generated per radioactive decay it is possible to get a broadening of the alpha spectra obtained through liquid scintillation. It is likely that these liquid scintillation spectra will be subject to a Gaussian broadening rather than the distortion exhibited when the layer of active material on a disk is too thick. A third energy dispersive method for counting alpha particles is to use a semiconductor detector. From left to right the peaks are due to 209Po, 210Po, 239Pu and 241Am. The fact that isotopes such as 239Pu and 241Am have more than one alpha line indicates that the nucleus has the ability to be in different discrete energy levels (like a molecule can).

[ edit ] Overview By mass, polonium is around 250 billion times more toxic than hydrogen cyanide (the oral LD50 for 210Po is about 50 ng (see below) compared to about 250 mg for hydrogen cyanide [25] ). The main hazard is its intense radioactivity (as an alpha emitter), which makes it very difficult to handle safely - one gram of Po will self-heat to a temperature of around 500°C. Even in microgram amounts, handling 210Po is extremely dangerous, requiring specialized equipment and strict handling procedures. Alpha particles emitted by polonium will damage organic tissue easily if polonium is ingested, inhaled, or absorbed (though they do not penetrate the epidermis and hence are not hazardous if the polonium is outside the body). [ edit ] Acute effects The median lethal dose ( LD50 ) for acute radiation exposure is generally about 4.5 Sv . [26] The committed effective dose equivalent 210Po is 0.51 µSv/ Bq if ingested, and 2.5 µSv/Bq if inhaled.

[27] Since 210Po has an activity of 166 TBq per gram [27] (1 gram produces 166×1012 decays per second), a fatal 4-Sv dose can be caused by ingesting 8.8 MBq (238 micro curie ), about 50 nanograms (ng), or inhaling 1.8 MBq (48 microcurie), about 10 ng. One gram of 210Po could thus in theory poison 100 million people of whom 50 million would die. The actual toxicity of 210Po is lower than these estimates, because radiation exposure that is spread out over several weeks (the biological half-life of polonium in humans is 30 to 50 days [28] ) is somewhat less damaging than an instantaneous dose. It has been estimated that a minimal lethal dose of 210Po for an 80 kg person is 4 millicuries, or 0.89 micrograms, still an extremely small amount.

[29] [ edit ] Long term (chronic) effects In addition to the acute effects, radiation exposure (both internal and external) carries a long-term risk of death from cancer of 5–10% per Sv. [26] The general population is exposed to small amounts of polonium as a radon daughter in indoor air; the isotopes 214Po and 218Po are thought to cause the majority [30] of the estimated 15,000-22,000 lung cancer deaths in the US every year that have been attributed to indoor radon. [31] Tobacco smoking causes significant additional exposure to Po. [ edit ] Regulatory exposure limits The maximum allowable body burden for ingested 210Po is only 1,100 Bq (0.03 microcurie), which is equivalent to a particle weighing only 6.8 picograms. The maximum permissible workplace concentration of airborne 210Po is about 10 Bq/m3 (3 × 10-10 µCi/cm3). [32] The target organs for polonium in humans are the spleen and liver .

[33] As the spleen (150 g) and the liver (1.3 to 3 kg) are much smaller than the rest of the body, if the polonium is concentrated in these vital organs, it is a greater threat to life than the dose which would be suffered (on average) by the whole body if it were spread evenly throughout the body, in the same way as caesium or tritium (as T2O). 210Po is widely used in industry, and readily available with little regulation or restriction. In the US, a tracking system run by the Nuclear Regulatory Commission will be implemented in 2007 to register purchases of more than 16 curies of polonium 210 (enough to make up 5,000 lethal doses). The IAEA "is said to be considering tighter regulations...

There is talk that it might tighten the polonium reporting requirement by a factor of 10, to 1.6 curies." [34] [ edit ] Famous polonium poisoning cases Notably, the alleged murder of Alexander Litvinenko , a Russian dissident, in 2006 was announced as due to 210Po poisoning [35] (see Alexander Litvinenko poisoning ). According to Nick Priest, a radiation expert speaking on Sky News on December 2 , Litvinenko was probably the first person ever to die of the acute α-radiation effects of 210Po. It has also been suggested that Irène Joliot-Curie was the first person ever to die from the radiation effects of polonium (due to a single intake) in 1956. [36] She was accidentally exposed to polonium in 1946 when a sealed capsule of the element exploded on her laboratory bench. A decade later, on 17 March 1956 , she died in Paris from leukemia which may or may not have been caused by that exposure.

According to the book The Bomb in the Basement , several death cases in Israel during 1957-1969 were caused by 210Po. [37] A leak was discovered at a Weizmann Institute laboratory in 1957. Traces of 210Po were found on the hands of Prof. Dror Sadeh , a physicist who researched radioactive materials. Medical tests indicated no harm, but the tests did not include bone marrow. Sadeh died prematurely from cancer . One of his students died of leukemia, and two colleagues died after a few years, both from cancer. The issue was investigated secretly, and there was never any formal admission that a connection between the leak and the deaths had existed. [ edit ] Treatment It has been suggested that chelation agents such as British Anti-Lewisite ( dimercaprol ) can be used to decontaminate humans.

[38] [39] In one experiment, rats were given a fatal dose of 1.45 MBq/kg (8.7 ng/kg) of 210Po; all untreated rats were dead after 44 days, but 90% of the rats treated with the chelation agent HOEtTTC remained alive after 5 months. [40] What is polonium, the rare chemical Russia allegedly used to murder Alexander Litvinenko — Quartz Simon Cotton Senior lecturer in chemistry, University of Birmingham January 21, 2016 The murder of former Russian spy Alexander Litvinenko was one of the most high-profile assassinations of the decade. It particularly captured the public imagination because Litvinenko was killed using polonium-210, a rare but deadly substance that was thought to have been slipped into Litvinenko’s tea. Now a UK public inquiry has issued its findings on the case. But what is polonium? Rare and radioactive Polonium is a radioactive element that occurs naturally in tiny amounts (which are harmless to us). It was discovered in 1898 by Marie Curie, during her research on pitchblende, an ore of uranium.

It has the chemical symbol “Po” and Curie named it after Poland, her native country. If you look at a periodic table, you’ll find polonium at the bottom of the group headed by oxygen and sulfur. There are around 30 different isotopes of polonium ranging in atomic mass from 194 to 218, only differing from each other in their neutron number. The important one is polonium-210, which happens to be the one discovered by Curie. According to an expert who testified to the Litvinenko enquiry, only one place in the world had a polonium “production line.” Uranium atoms slowly decay into other atoms, eventually ending up as lead but with polonium as one stop on the way. Because of this radioactive decay, polonium atoms are continually being formed and decomposed so the element does not naturally accumulate in any significant amount. Although polonium-210 was first isolated from uranium ores, today it can be artificially made by bombarding atoms of the metal bismuth with neutrons.

According to an expert who testified to the Litvinenko enquiry, only one place in the world had a polonium “production line”—a closed nuclear facility in Sarov, just under 500 miles south-east of Moscow—and the sample used in the murder was highly likely to have come from here. Highly toxic Polonium is one of the most toxic substances known. According to some sources, it is up to a trillion times more toxic than hydrogen cyanide. It is radioactive because it emits alpha particles (helium ions). Because these are easily absorbed by other materials, even by a few thin sheets of paper or by a few centimetres of air, polonium has to be inside your body to damage you. Once polonium gets into the blood, it is likely to cause acute radiation syndrome and you will die of multiple organ failure. It’s this radiation that has made minuscule traces of polonium useful in anti-static brushes, which are used to remove static charge from sensitive equipment. The fact that its alpha particles are so easily absorbed also make it hard to detect by radiation detectors such as Geiger counters, so polonium is probably easier to smuggle than some other lethal agents.

If polonium is known to have entered the body very recently, there is a chance of removing it by gastric aspiration (sucking out the stomach contents) or lavage (washing the stomach out with water). Chelating chemical agents, the sort that are used to treat heavy metal poisoning, can also remove polonium from the body if administered very quickly. But once it gets into the blood, it is likely to cause acute radiation syndrome and you will die of multiple organ failure. Effect on the body The alpha radiation breaks apart the chemical bonds in living cells, damages DNA and creates lots of very reactive free radical ions that can do further damage. One specific result is a reduction in your white blood cell count which, apart from anything else, can make you more susceptible to infection and requires blood and platelet transfusions. The liver, kidneys, spleen and bone marrow are particular targets and are massively damaged by the alpha-radiation. The rapid damage to the gastrointestinal tract causes nausea and vomiting. Bone marrow failure can result in days. One other target is hair follicles, which is why Litvinenko lost his hair before he died. Alexander Litvinenko is not the first casualty of polonium.

In 1956, Marie Curie’s scientist daughter Irène Joliot-Curie died of leukaemia that she is believed to have contracted through exposure to polonium years before. There have also been claims that Palestinian leader Yasser Arafat may have been exposed to it in a similar way to which Litvinenko was. This post originally appeared at The Conversation . Follow @ConversationUS on Twitter. We welcome your comments at ideas@qz.com . Read full story What is polonium-210? Radioactive poison used to kill Russian agent Alexander Litvinenko — in plot likely endorsed by Putin — is highly lethal Contact Us What is polonium-210? Radioactive poison used to kill Russian agent Alexander Litvinenko — in plot likely endorsed by Putin — is highly lethal Looking for a hard to detect, highly radioactive and deadly isotope to take out a rival spy? Polonium-210 might be your cup of tea. The toxic material used to murder former Russian agent Alexander Litvinenko in November 2006 is so lethal that a single microgram no bigger than a dust speck is sufficient to cause death.

Once introduced to the system, either by inhaling or ingesting the isotope, polonium-210 wreaks havoc on virtually the entire body — from blood cells to bone marrow to the central nervous system. Read more . 10 Uses for Mostly Useless Chemical Elements Riddle of the Week #10: Einstein's Riddle 10 Uses for Mostly Useless Chemical Elements Gold. Titanium. Oxygen. Some elements get all the glory. But even the least practical residents of the periodic table can find a purpose. Getty By John Wenz Aug 20, 2013 They're the elements with the big atomic numbers. The ones from the far reaches of the periodic table who rarely get mentioned in the same breath as elemental superstars like carbon, nitrogen, or helium. But don't sleep on the weird, rare, and oddball elements. They're surprisingly important. Advertisement - Continue Reading Below The Transuranics: Berkelium (Element 97) and Up As the name would suggest, the transuranics are those elements with atomic numbers higher than that of uranium, and are typically synthesized in a lab.

While neptunium through curium have their places, mostly in nuclear power, berkelium starts a sea of relative uselessness. The elements beginning with einsteinium and going up, in fact, have never been spotted in nature. Most have half-lives of a minute or even fractions of a second, which factors into their not-so-abundant nature. Uses: Physicists believe that there may be an " island of stability " above these elements with comparatively prolonged half-lives. You know, if we could manage to make the darn things. To that end, creating and studying the transuranics in the lab is a step toward one day perhaps finding even heavier elements. Actinium (89) You'll notice two running themes in this list. Often, the hallmark of uselessness in the periodic table involves elements that are expensive to create or extract and highly radioactive. This one–two punch makes it difficult to create uses for actinium. Uses: Thus-far limited application in radiation therapy (though more research is underway) for certain types of cancer such as myeloid leukemia, and some scientific research, including the production of neutrons.

Rhoda Baer/National Cancer Institute Advertisement - Continue Reading Below Scandium (21) Scandium is the lightest element on our list, typically found in nature in small amounts but tied up with other elements. It's hard to find and, once found, difficult to extract. Short of finding a large supply somewhere, scandium will be of scant use. Uses: Scandium is useful in small amounts, usually in alloys. It shows up in the odd aluminum-alloyed baseball bat or aircraft. Roughly 44 pounds of the stuff per year is used in a compound found in high-intensity lights used in stadiums and on movie sets, as the light created is bright-white. Rrausch1974 at Wikipedia Polonium (84) Polonium is nasty stuff: It's a volatile, radioactive, toxic metal first found by Marie Curie. It occurs naturally in uranium ores, though most polonium today is created artificially by bombarding bismuth. Apollo 16 went on a polonium hunt from lunar orbit in an attempt to determine the abundance of uranium on the moon.

Uses: Polonium's high radioactivity was used to keep satellites and other spacecraft components, including some Russian moon rovers, from freezing during the early space program. A capsule of just half a gram can reach temperatures of 500 degrees C. It's occasionally used as a static reducer. And one isotope, polonium-210, was used by an assailant to poison former KGB agent Alexander Litvinenko . Great track record, that. Armael at Wikipedia Advertisement - Continue Reading Below Protactinium (91) Just below uranium on the periodic table, protactinium does . . . well, not much. It occurs naturally as a result of uranium decay, but it's highly radioactive and toxic. Use: Protactinium has found one particular niche use: The isotope protactanium-21 is used to date sediments back roughly to 175,000 years ago, owing to its long half-life of 32,760 years. Rob Lavinsky/iRocks.com Thulium (69) Poor thulium. The much-picked-on element was called the most useless by science writer John Emsley during an National Public Radio interview.

Theodore Gray, another science writer and element collector (which is apparently a thing) appearing on the same episode of Science Friday, rushed to its defense . Uses: Thulium has some applications in portable X-ray devices, superconductors, and lasers. So it may be rare and expensive, but it isn't useless! Jurii at Wikipedia Advertisement - Continue Reading Below Radon (86) Unlike some elements on this list, radon is really too common. The element has been at the heart of numerous public service announcements warning of the dangers of radon in the home. It's second to smoking in terms of lung cancer–causing carcinogens, and the deadly gas is often emitted from the ground, allowing it to accrete in poorly ventilated basements. Uses: There is limited medicinal use: small, targeted radon "seeds" are used in radiation therapy to destroy cancerous cells. But it's controversial and possibly harmful. Some arthritis sufferers seek out radon therapy , a treatment involving intentional exposure to radon to alleviate pain; it's against the law in the United States.

Lutetium (71) This rare-earth element binds well with other such metals, making pure lutetium scarce—so much so that it fetches $10,000 per kilogram. Commonly regarded as the rarest of the rare-earth metals, the price point prevents much use. Uses: In oil refining, lutetium is used as a catalyst to help break down crude oil into smaller chains of molecules in a process known as cracking. It is also used in imaging technologies in radiation research. Jurii at Wikipedia Advertisement - Continue Reading Below Astatine (85) The rarest of rare elements (at least in the everything-below-uranium category), astatine has never been found in nature, and less than 28 grams of the highly radioactive stuff are thought to be found on earth at any point. The name itself derives from the Greek word astatos, meaning "unstable." First synthesized in 1940, the most stable isotope lasts just 8 minutes.

Uses: It's thought to have some potential use in radiation therapy for certain kinds of cancer, though one isotope, 210, decays into polonium-210, the murderous uses of which we've already covered. MarlonMarin1 at Wikipedia Francium (87) Francium is highly radioactive, completely unstable, and rarely found in nature. Its most stable isotope has a half-life of 22 minutes, and when it decays, one of its nastier byproducts is radon. Its instability means that in order to get francium, you have to make francium . . . and watch it quickly disintegrate. At any given moment less than 30 grams exist in nature . Uses: Francium's use is recursive: The production of francium is mostly done to study francium, because there aren't many other ways to get francium. Kgrr/Flickr | Health , Israel , Russia What is polonium? Polonium is a rare and highly radioactive element. It is found naturally in the atmosphere and in the earth’s crust, though in miniscule quantities.

Marie Curie discovered the element in the late 19th century and named it after her native country of Poland (in Latin: Polonia). It has dozens of isotopes. One of the most common is polonium-210, which emits highly radioactive alpha particles; this was the isotope found on Yasser Arafat’s personal effects during Al Jazeera’s initial investigation. Because of its radioactivity, polonium has been used as a trigger for nuclear weapons, and as a power source for satellites and other spacecraft. The Russian space programme used it to heat rovers that landed on the Moon in the 1970s. A lethal dose of polonium 210 can be caused by ingesting just 50 nanograms or inhaling an even smaller amout of 10 nanograms, which means that only one gram of polonium 210 could in theory poison and kill about 10 million people. Has it been used as a poison before? Yes, at least once. Polonium was used to kill Alexander Litvinenko, a onetime Russian spy turned dissident.

Litvinenko was in good health until November 1, 2006, when he suddenly became sick and was hospitalised. He initially suffered from severe diarrhoea and vomiting; the hospital diagnosed him with a stomach infection. His condition continued to worsen, though. Doctors discovered that his white blood cell count had plummeted, making him susceptible to infection. “His skin had turned yellow, indicating liver dysfunction, and he was tested for the two most likely causes, hepatitis and AIDS, but neither was the case,” John Emsley wrote in Molecules of Murder, which includes a chapter on polonium poisoning. “Then his hair began to fall out.” Doctors eventually decided that Litvinenko was suffering from radiation poisoning, and further tests identified polonium as the culprit. Polonium is also believed to have killed several other people, including Curie’s daughter Irene, and two people working on Israel’s nuclear programme. What are the symptoms of polonium poisoning? Because there have been so few recorded cases, there is not much scientific literature on the subject. The handful of human cases, as well as animal studies, suggest symptoms similar to other forms of radiation poisoning – vomiting, diarrhoea, hair loss, a low white blood cell count.

Traces of the poison reach vital organs like the liver and heart, and cause those organs to fail. How is polonium produced? It occurs naturally in uranium ores, but at extremely small concentrations, as low as 100 micrograms per tonne of ore. Rather than laboriously extracting it from uranium, modern-day manufacturers create polonium in nuclear reactors, by bombarding bismuth with neutrons. Most of the world’s polonium supply is produced in Russia. Content on this website is for general information purposes only. Your comments are provided by your own free will and you take sole responsibility for any direct or indirect liability. You hereby provide us with an irrevocable, unlimited, and global license for no consideration to use, reuse, delete or publish comments, in accordance with Community Rules & Guidelines and Terms and Conditions . MORE FROM AL JAZEERA Advertisement Radioactive poison used on Litvinenko may have harmed Londoners, says lawyer Alexander Litvinenko, former KGB spy and author of the book 'Blowing Up Russia: Terror From Within,' is photographed at his home in London on Friday, May 10, 2002.

(AP / Alistair Fuller, File) Jill Lawless, The Associated Press Published Thursday, July 30, 2015 6:47AM EDT Last Updated Thursday, July 30, 2015 10:27AM EDT LONDON -- The killers of former Russian agent Alexander Litvinenko may have harmed the health of thousands of Londoners as they trailed radioactive polonium-210 around the city, a lawyer for British police said Thursday. Richard Horwell told an inquiry into Litvinenko's death that the killing -- which police blame on two Russians directed by elements in the Kremlin -- may have exposed "hundreds if not thousands of Londoners" to radioactive contamination. "We will never know how dangerous the exposure of polonium to the public at large will be and what long-term effects will be visited on Londoners," Horwell said. Litvinenko, a KGB officer-turned-Kremlin critic who fled to Britain in 2000, died in 2006, three weeks after drinking tea laced with polonium-210 at a London hotel.

On his deathbed, Litvinenko accused Russian President Vladimir Putin of ordering his assassination -- a claim Moscow denies. British authorities say there is evidence of Russian state involvement, and police have accused two Russians who met Litvinenko in London, Dmitry Kovtun and Andrei Lugovoi, of carrying out the killing. Both deny involvement. Horwell said the "the science is such that the finger points unwaveringly" at Kovtun and Lugovoi. "The Metropolitan Police Service want Lugovoi and Kovtun to be tried in this country for murder," Horwell said. But that seems a remote prospect. Moscow refuses to extradite the suspects. Lugovoi is now a lawmaker in Russia, and in March he was given a medal by Putin for services to the nation. Horwell said that "no matter how many state honours Putin may pin to Lugovoi's chest for services to the motherland ...

Lugovoi and Kovtun have no credible answer to the scientific evidence and to the trail of polonium they left behind." Traces of the radioactive isotope, which is deadly if ingested in tiny quantities, were found in sites across London that the pair visited, including hotel rooms, restaurants, nightclubs and the stadium of soccer team Arsenal. Lawyers are making closing statements at the months-long inquiry, which is due to end Friday. Judge Robert Owen, who has heard from dozens of witnesses and seen secret evidence from the British intelligence services, plans to release his conclusions by the end of the year. Horwell said it was clear that "the Russian state in one form or another is likely to have been the sponsor of this plot." Litvinenko had criticized his former employer, the FSB, successor to the KGB, and accused Putin of being involved in criminal activities. Litvinenko also co-authored a book blaming the Russian government for involvement in a series of apartment building explosions in 1999 that were blamed on Chechen rebels. "The Russian state had reasons aplenty for wishing Litvinenko not only harm, but death," Horwell said. The Kremlin has denied all Litvinenko's accusations against the government and Putin.

Related Stories Did it take a nuclear physics lab to murder Alexander Litvinenko? Introduction The news reports on the murder of former KGB agent Alexander Litvinenko with radioactive polonium 210 (Po-210) quote various experts as saying that polonium is an extremely rare and exotic substance. Making the "huge" amount of it needed to murder somebody supposedly would require a nuclear reactor or perhaps a particle accelerator: large, expensive and exotic pieces of equipment far beyond the reach of amateurs. The obvious implication is that the Po-210 was provided by (or stolen from) the Russian nuclear establishment. (The Russians are known to have produced and used Po-210 in various legitimate applications such as heating the Lunokhod lunar rovers during the 2-week lunar night.) See, for example, the Reuters article Polonium - deadly, hard to make and rare poison : Radiation and chemistry experts say large-scale equipment, such as a nuclear reactor, would be needed to produce sufficient amounts to cause death. "It is not as simple as the idea that somebody might have broken into a radioactivity cabinet at some local hospital and walked off with some polonium," Dr Andrea Sella, a lecturer in chemistry at University College London, told Reuters.

"You can't make this at home. This is in a different league," he added. But is this true? Maybe you can't make it at home, but I'm not so sure about the rest. To explain why, I have to start with some physics background. Polonium 210 is the second to last entry in the decay chain of U-238 (uranium 238), the most abundant (99.275%) isotope of uranium in nature. Unless they have been removed, all of these isotopes, including Po-210, thus appear in small amounts with uranium wherever it is found. Marie Curie discovered and separated polonium from pitchblende (a uranium ore consisting mainly of uranium dioxide, UO2) in 1897 using purely chemical means. This was over a century ago. The first nuclear reactor and even the particle accelerator were still decades away. Like every other element heavier than iron (the end result of "normal" stellar thermonuclear fusion ), the U-238 present today in the earth was created by the explosion of supernovae long before the solar system and earth were formed about 4.5 billion years ago.

Because it has a 4.5 billion year half life, about half of the U-238 originally present in the earth at its formation is still here today. In undisturbed rocks and ores, U-238 exists in equilibrium with every isotope in its long decay chain. This chain ends with stable Pb-206 (lead 206), so as time passes lead accumulates and the radioactive elements (including the U-238) slowly disappear. At equilibrium, each isotope in the decay chain is produced just as fast as it decays. So every radioactive isotope in the decay chain must have exactly the same radioactivity. That is, if a sample of undisturbed, unprocessed uranium ore contains 1,000 Bq (becquerel) of U-238, then it must also contain 1,000 Bq of thorium 234, 1,000 Bq of palladium 234, etc, all the way down to 1,000 Bq of polonium-210.

(The becquerel is the SI unit of radioactivity, defined as one disintegration per second.) After another 4.5 billion years, assuming the sample is sealed to prevent the escape of gaseous elements such as radon, it will have only 500 Bq of U-238, 500 Bq of Th-234, etc, and 500 Bq of Po-210. Half of the U-238 present today will become Pb-206. Although every isotope in the decay chain has the same radioactivity, the number of atoms of each isotope will vary widely because of their vastly different half lives. In fact, the number of atoms of each isotope in the decay chain at equilibrium is directly proportional to its half life. Polonium-210 has a half life of only 138 days, so the number of Po-210 atoms will be only be 138 days / 4.5 billion years or about 10-10 (1 ten-billionth) of the number of U-238 atoms.

Po-210 as a radiological poison Po-210 decays by 5.407 MeV alpha decay into Pb-206, which is stable. Alpha particles are highly ionizing. Even a small amount of matter, such as a piece of paper or a few inches of air, will stop alpha particles and absorb their energy. A radioactive substance that emits only alpha particles is therefore easy to shield. But if the unshielded substance is taken into and spread throughout the body, then the alpha particles are absorbed by the adjacent tissues where they deposit their harmful energy. This makes alpha emitters like Po-210 potent radiological poisons, but only when they are injected, ingested or inhaled. Outside the body they cause little or no harm. Computing a fatal dose It takes about 5-10 sieverts , equal to 500-1000 rem , of whole-body radiation exposure to cause prompt, severe radiation sickness and probable death within a few days or weeks in previously healthy humans.

The sievert is the SI unit of biological radiation dosage; it is related to the gray and rad , measures of absorbed radiation energy in inert materials, by the biological radiation weighting factor, a dimensionless ratio. One gray is equal to an absorbed energy dosage of 1 joule per kilogram of absorbing material. The biological radiation weighting factor, i.e., the ratio of sieverts to grays, is the product of two values, Q and N. Q depends on the type of radiation (alpha, beta, gamma), and N depends on the particular body tissue. The Q value for alpha particles is 20, reflecting their highly ionizing nature. For human bone marrow, colon, lung and stomach, N=0.12; for several other organs, including the bladder, brain, breast, kidney, liver and small intestine, N=0.05. Taking the larger value of N=0.12 gives a QN product of 2.4. In other words, the deposition of 1 joule of alpha particle energy in 1 kg of human bone marrow (1 gray) would represent a dose of 2.4 sieverts.

To compute the radiation dosage to the body from a given amount of ingested Po-210, we next need to know how much energy is released in its alpha particles. As mentioned above, each Po-210 decay releases an alpha particle with an energy of 5.407 MeV, so we can easily compute the total energy released by the complete decay of a given amount of Po-210 by multiplying the 5.407 MeV alpha energy by the number of polonium atoms. But we can't wait for all of the Po-210 to decay; we'll want to give our victim his fatal dose within, say, one week, and only half of it decays in about 138 days. (It took several weeks for Litvinenko's doctors to figure out what was wrong with him, and by then it was too late.) Radioactive decay is an exponential process; the fraction of undecayed atoms left after time t is e-t * ln(2)/h, where h is the half-life.

The fraction of Po-210 remaining after one week is therefore e-7 * ln(2)/138.376 = 0.9655 This means 1 - 0.9655 = 3.45% of the Po-210 will decay in one week, and we'll need 1/(1-0.9655) = 29 times as much Po-210 to deliver 10 sieverts in 7 days as we'd need to deliver 10 sieverts in infinite time (or 5 sieverts in one half life of 138.376 days). One gram of Po-210 is 1/210 = 4.762 * 10-3 mole . Multiplying this by Avogadro's number , the number of atoms in a mole, we obtain 4.762 * 10-3 * 6.022 * 1023 = 2.87 * 1021 atoms of Po-210.

If we multiply this many atoms by the alpha energy of 5.407 MeV, we obtain a total energy release of 2.87 * 1021 * 5.407 MeV = 1.55 * 1028 eV. One joule equals 6.24 * 1018 eV, so this is equal to 2.48 * 109 joules, or 2.48 gigajoules. The average adult human male has a mass of 70 kg. If we assume the Po-210 is uniformly distributed throughout the body, then the whole-body radiation dosage from 1 gram of Po-210 in one week would be 0.0345 * 2.48 gigajoules / 70 kg * 2.4 sievert/gray = 2.9 * 106 sievert. This is a truly gargantuan dose, but 1 gram is a huge amount of Po-210.

If we only need 10 sieverts/week to kill our victim, then we only need 10 sievert / (2.9 * 106 sievert/gram) = 3.4 * 10-6 g. That's 3.4 micrograms. Uranium ore as a source of Po-210 poison Let's suppose we wanted to follow in Marie Curie's footsteps and extract our fatal dose of Po-210 from natural uranium ore using purely chemical means. How much ore would we need? As discussed above, in a sample of natural uranium in equilibrium with its decay chain, the relative abundance of Po-210 to U-238 is the ratio of their half-lives. The half life of Po-210 is 138.376 days; the half life of U-238 is 4.468 * 109 years, or 1.63 * 1012 days (at 365.25 days/year).

The Po-210/U-238 half-life (and abundance) ratio is therefore 138.376 / (1.63 * 1012) = 8.48 * 10-11 (or about 1 part in 10 billion, as mentioned earlier). That's about one atom Po-210 per 11.8 billion atoms of U-238. But we only need 3.4 micrograms of Po-210. That corresponds to (238/210) * (3.4 * 10-6 g / 8.48 * 10-11 = 4.54 * 104 g = 45.4 kg U-238. In other words, we only need as much natural uranium ore as contains 45.4 kg of U-238. That's not all that much, is it?

Concluding thoughts The above calculation leaves out several factors I do not know, such as the speed and yield of the chemical extraction process, the chemical form and biological behavior (uptake, distribution and excretion) of the polonium in Litvinenko's body, and the actual dose that he ingested. Since he was reported to fall ill within hours of his presumed exposure, it is entirely possible that his dose was much greater than the single-digit microgram amounts that I have assumed. This would require a larger and presumably less practical chemical extraction process. On the other hand, one would have difficulty explaining why Litvinenko survived for nearly a month given that it took nearly that long to find out what had poisoned him, and presumably to begin any effective therapies to remove the polonium from his body. In any event, microgram amounts of Po-210 seem very dangerous indeed, so the utility, at least in theory, of chemical extraction cannot be ruled out. If the only possible source of the Po-210 that killed Alexander Litvinenko was a large nuclear laboratory, this would point strongly at Russia, either for deliberately murdering him or for failing to secure their inventories of Po-210.

But counter to the intuitive claims of the experts in the media, I don't think we can rule out chemical extraction from manageable amounts of uranium ore with a technique that was first developed (and published) over a century ago. It is also worth pointing out that, unlike a finite stockpile of Po-210 produced in a reactor or particle accelerator, uranium ore is a nearly infinitely renewable source of Po-210. After extraction, a significant amount is replenished in a matter of weeks by further decay of the parent isotopes in the U-238 decay chain. I think this might have some practical implications vis a vis use of pure Po-210 (stolen or allocated) for international political assassinations. Once pure Po-210 is used, it cannot be reused -- but the stock of uranium ore used to breed it could be. Po-210 also decays relatively rapidly -- a consideration if the international smuggling of radioactive isotopes is time consuming (and I have no way of knowing). Uranium ore, on the other hand, would be an assassin's gift that keeps on giving.

Phil Karn, v 1.02, 26 November 2006 The Dark History of Polonium | Yasser Arafat Credit: Anthony Correia / Shutterstock.com Little did scientists Marie and Pierre Curie suspect, when they discovered polonium in 1898, that the radioactive element would go on to have one of the darkest and most intriguing histories of any known substance. In 2004, Palestinian leader Yasser Arafat died of uncertain causes in Percy Hospital in Paris. He complained of nausea and stomach pain, suffered liver and kidney failure, and eventually lapsed into a coma before dying. In 2012, Arafat's remains were exhumed because of persistent rumors that he was the victim of an assassination that used polonium as a deadly weapon. A report published last week in the medical journal The Lancet confirmed that traces of polonium were found on Arafat's toothbrush, underwear and other personal items, fueling reports that he was assassinated. And Arafat isn't the first person who's believed to have been murdered by polonium.

[ The 13 Oddest Medical Case Reports ] Polonium can't penetrate unbroken skin, but if ingested or inhaled it can cause severe radiation damage to bodily tissues, organs and DNA, according to the U. S. Nuclear Regulatory Commission. Exposure to polonium also increases the risk of cancer, while an amount smaller than a grain of salt is enough to kill an adult. 'The angel of death' Alexander Litvinenko, a Russian political dissident, was living in London in 2006 when, on Nov. 1, he was enjoying a pot of tea in the Pine Bar of the Millennium Hotel with two other Russian men. Later that day, he became severely ill, and it wasn't long before poisoning was suspected. Tests eventually discovered that polonium-210 (an isotope of polonium) was not only in Litvinenko's body, but was found in lethal amounts throughout the Pine Bar and the adjacent kitchen area. One of Litvinenko's dining companions, Andrei Lugovoy, was a former KGB officer who emerged as a prime suspect in the poisoning.

Litvinenko died a few weeks later, but on his deathbed, he accused Russian president Vladimir Putin of orchestrating his assassination. "As I lie here I can distinctly hear the beating of wings of the angel of death," Litvinenko said in a statement, according to the Washington Post . "You may succeed in silencing one man, but the howl of protest from around the world will reverberate, Mr. Putin, in your ears for the rest of your life." [ How 13 of the World's Worst Dictators Died ] The assassination set off an international scandal: British Prime Minister Gordon Brown called it "intolerable" that Russian authorities refused to extradite Lugovoy for trial. "You cannot have people assassinated on British soil, and then discover that we wish to arrest someone who is in another country, and not be in a position to do that," according to the Telegraph . Putin dismissed Brown's statements as "insulting," and the case remains a diplomatic sticking point between the two nations — and a chilling reminder that Cold War-style political intrigue is not just the stuff of Tom Clancy thrillers.

Evidence of polonium-210 found The eight years that passed between Arafat's death and the time his body was exhumed for examination have made it more difficult to determine a cause of death, partly because polonium-210 has a biological half-life — the time needed for its levels in the body to fall by half — of just 50 days, and because Arafat's widow requested no autopsy following his death, the Guardian reports. "An autopsy would have been useful in this case because, although potential polonium poisoning might not have been identified during that procedure, body samples could have been kept and tested afterwards," the authors of the Lancet report wrote.

Nonetheless, the authors found evidence that "support the possibility of Arafat's poisoning with polonium-210," adding that "although the absence of myelosuppression [decrease in bone marrow activity] and hair loss does not favor acute radiation syndrome, symptoms of nausea, vomiting, fatigue, diarrhea and anorexia, followed by hepatic and renal failures, might suggest radioactive poisoning." The evidence that Arafat might have been killed by polonium has reignited some claims that he was assassinated, either by political rivals within the Palestinian community or by Israeli authorities, a claim that Israel has repeatedly denied. A trail of death Arafat and Litvinenko aren't the only two people who are suspected of dying after exposure to polonium, which Marie Curie named after her beloved native Poland. Irène Joliot-Curie, the daughter of Marie and Pierre Curie, may have been the first person to die of exposure to polonium, possibly related to a laboratory accident in 1946 (like her parents, Irène was a noted scientist who won the Nobel Prize in chemistry in 1935). She fell ill shortly thereafter and died of leukemia in 1956.

Despite its hazards, polonium — a soft, silvery-gray metal — does have some industrial applications. It can be used to eliminate static electricity in machine processes such as paper rolling and fiber spinning, according to the International Atomic Energy Agency. And because of its radioactivity, polonium-210 has been used as a heat source in satellites and in the Soviet 1970s-era Lunokhod moon rovers .

Question: An isotope of which chemical element was used to poison Alexander Litvinenko?
Answer: Polonium