Polonium
Polonium is a metal so radioactive that a few curies of it make the surrounding air glow blue. It sits at number 84 on the periodic table, and nearly everything about it is extreme. Its isotopes all fall apart quickly. Its natural traces are tiny. Its handling rules are strict enough to require sealed glove boxes under constant suction. Yet this fleeting element has turned up in a Moon rover, in a bomb core, in a car engine and in a murder inquiry. How do you find an element that no one can easily isolate? Who named it, and what was the name meant to say? Why does it hide in so many unexpected places? And what makes an amount too small to see so dangerous?
Pitchblende, a uranium ore, handed Marie Skłodowska-Curie and Pierre Curie a puzzle in 1898. After they stripped out the radioactive uranium and thorium, the leftover material was more radioactive than the two combined. Something else had to be hiding in the ore. The Curies went looking, and the first new element they pulled out was polonium. They identified it solely by its strong radioactivity, which made it the first element ever discovered that way.
They tentatively called it radium F, but the name that stuck came from Polonia, the form of Marie's native Poland. At the time, Poland did not exist as an independent country. Russia, Germany and Austria-Hungary had partitioned it between them. Marie hoped the new name would draw attention to that missing independence. Polonium may be the first element named to highlight a political controversy.
Five months after separating polonium from pitchblende, the Curies isolated a second element from the same ore, radium.
In 1902, the German scientist Willy Marckwald isolated 3 milligrams of polonium. He thought he had found something new and called it radio-tellurium. It took until 1905 for anyone to show that his radio-tellurium and the Curies' polonium were the same element.
A single milligram of polonium-210 carries 5 curies of radioactivity. It emits as many alpha particles each second as 5 grams of radium-226, which makes it 5,000 times more radioactive than radium. Its half-life is 138.4 days, and it decays straight into stable lead-206. About one in 100,000 of its alpha emissions leaves the nucleus excited, and the nucleus then releases a gamma ray with a maximum energy of 803 keV.
At 55 degrees Celsius, half of a heated sample of polonium-210 vaporizes within 45 hours. That is surprising, because the metal melts at 254 degrees and boils at 962. More than one explanation exists. One suggestion is that alpha decay knocks small clusters of atoms off the surface.
The solid metal comes in two forms. The alpha form has a unit cell with an edge of 335.2 picometers. It is the only known example of a simple cubic crystal built from a single kind of atom under standard conditions. The beta form is rhombohedral.
Dissolve polonium in dilute acid and the solution first turns pink, colored by Po2+ ions. Soon it turns yellow, because alpha radiation ionizes the solvent and converts Po2+ into Po4+. The same radiation makes the liquid bubble and give off heat. Glassware holding it gives off heat and light as it absorbs alpha particles. Unless a solution is sealed, it evaporates within days.
Chemically, polonium is a chalcogen that behaves much like selenium and tellurium. Its metallic character, however, resembles thallium, lead and bismuth. More than 50 compounds are known, and almost all are synthetic. The most stable are the polonides, made by reacting polonium directly with another element. Thulium polonide melts at 2200 degrees Celsius, while mercury polonide decomposes at about 300. Lead polonide is one of the few that occurs in nature, since polonium's alpha decay produces lead. Polonium hydride is a volatile liquid at room temperature, and water is the only other liquid hydrogen chalcogenide.
Because the element wrecks its own chemistry with radiation, most of what chemists know comes from trace-scale experiments.
Uranium ores hold about 0.1 milligrams of polonium per metric ton, roughly 0.2 percent of the abundance of radium. Nine isotopes, numbered 210 through 218, appear in traces as products of the decay chains of uranium-238, uranium-235, thorium-232 and neptunium-237. Only polonium-210 has a half-life longer than 3 minutes. The amounts in the Earth's crust are not harmful.
In all, 42 isotopes of polonium are known, running from 186 to 227, and every one is radioactive. Two outlast polonium-210. Polonium-209 has a half-life of 124 years and polonium-208 a half-life of 2.898 years. Both are made by firing protons at bismuth in a cyclotron.
The largest batch ever taken from natural sources, in the first half of the 20th century, held only 40 curies of polonium-210, about 9 milligrams. Getting it meant processing 37 tonnes of residues left over from radium production.
A 1934 experiment pointed to an easier route. Bombarding natural bismuth-209 with neutrons creates bismuth-210, which then decays to polonium-210 by beta-minus decay. Modern production follows that path in nuclear reactors, using their high neutron fluxes, and finishes with pyrochemical purification and liquid-liquid extraction. The output is only about 100 grams a year, practically all of it in Russia.
The same reaction causes trouble inside lead-bismuth cooled reactors, such as those in the Soviet Navy's K-27. Engineers there had to plan for polonium-210 escaping from the coolant.
During World War II, the United States produced polonium through the Dayton Project, part of the Manhattan Project. Mixed with beryllium, it formed the Urchin initiator at the center of the bomb's spherical pit. Urchin started the chain reaction at the moment of prompt-criticality, so that the weapon would not fizzle. Early American weapons used it, and later ones switched to a pulse neutron generator. Much of polonium's basic physics stayed classified until after the war. Its role in gun-type nuclear weapons stayed secret until the 1960s.
A one-gram sample of polonium-210 heats itself above 500 degrees Celsius and produces about 140 watts of power. That made it a heat source for radioisotope thermoelectric generators. Polonium heaters kept internal parts warm through the lunar nights aboard the Moon rovers Lunokhod 1 in 1970 and Lunokhod 2 in 1973. They also flew on the satellites Kosmos 84 and 90 in 1965.
Beryllium oxide converts alpha particles into neutrons at a rate of 93 neutrons per million alpha particles. Such mixtures served as passive neutron sources, as triggers for nuclear weapons, and for inspecting oil wells. The Soviet Union used about 1500 sources of this type every year, each with an activity of 1850 curies. Soviet polonium alpha sources also measured the thickness of industrial coatings, by how much the coating weakened the radiation.
Brushes holding up to 500 microcuries of polonium-210 drained static charge from photographic plates, textile mills, paper rolls, plastic sheets and car parts before painting. The alpha particles ionize air molecules, and those neutralize charges on nearby surfaces. In the US, devices with no more than 500 microcuries of sealed polonium-210 could be bought in any amount under a general license, with no registration. Because of its short half-life, the polonium needed replacing nearly every year. Less dangerous beta sources have mostly taken its place.
From 1940 to 1953, Firestone marketed polonium spark plugs. Alfred Matthew Hubbard had built a radium prototype first. The idea behind both was that radiation would ionize the fuel and let the engine fire faster and more efficiently. The radiation was minuscule and posed no threat to drivers. The benefit faded after about a month, as the half-life ran down and buildup on the conductors blocked the radiation.
Small needle sources of polonium-210 are still sold to the public in the US by scientific supply companies, for experiments such as cloud chambers. A layer of polonium is plated over with a material such as gold. The gold lets alpha radiation through but keeps the polonium from escaping and creating a toxic hazard.
In the mid-1940s, five patients at the University of Rochester received small doses of polonium-210 to study how the body handles it. The work was funded by the Manhattan Project and the Atomic Energy Commission. Four men and a woman took part, all with terminal cancers and aged from their early thirties to early forties. Experimenters chose them because none had been exposed to polonium through work or accident. Four were injected and one swallowed the dose. None of the doses came close to a fatal amount.
By mass, polonium-210 is around 250,000 times more toxic than hydrogen cyanide. The lethal amount for an average adult is less than 1 microgram, compared with about 250 milligrams for the cyanide. Polonium has no toxic chemical properties. The danger is its radioactivity.
A fatal dose of 4.5 sieverts can come from swallowing 8.8 megabecquerels, about 50 nanograms, or from inhaling 1.8 megabecquerels, about 10 nanograms. On paper, one gram could poison 20 million people and kill 10 million. Real toxicity is lower. The biological half-life of polonium in humans is 30 to 50 days, and exposure spread over weeks does less harm than a sudden dose. One estimate puts the median lethal dose at 15 megabecquerels, or 0.089 micrograms. A grain of table salt weighs about 60 micrograms.
Alpha particles cannot cross the outer layer of skin, so polonium outside the body is harmless as long as it stays away from the eyes. Swallowed, inhaled or absorbed, it damages tissue easily. The spleen and liver are its target organs. They are small, so polonium concentrated there threatens life more than the same amount spread through the body. Over the long term, radiation exposure carries a cancer death risk of 5-10 percent per sievert.
Even microgram amounts of polonium-210 call for a negative-pressure alpha glove box with high-performance filters. Gloves are a particular weak point. Polonium dissolved in concentrated nitric acid can diffuse through latex, or the acid can attack the gloves. Denser neoprene and butyl gloves shield alpha particles better, and extra surgical gloves are added inside and out.
In 2007, the US Nuclear Regulatory Commission began tracking purchases of more than 16 curies of polonium-210, enough for 5,000 lethal doses. The International Atomic Energy Agency was reported to be considering tightening that threshold tenfold, to 1.6 curies.
In one experiment, rats given a fatal dose of polonium-210 all died within 44 days when left untreated. Of those given the chelation agent HOEtTTC, 90 percent were still alive after five months. British anti-Lewisite, also called dimercaprol, has been suggested for decontaminating humans. Doctors confirm poisoning by alpha particle spectrometry of biological specimens. Healthy people excrete 5-15 millibecquerels of polonium-210 a day, and a level above 30 suggests excessive exposure.
On the 10th of July 1954, a 41-year-old man in the Soviet Union died in the first documented death directly caused by polonium. He had sought treatment on the 29th of June with severe vomiting and fever. The day before, he had spent five hours in an area where a capsule of polonium-210 had depressurized and dispersed as an aerosol. His intake was estimated at 0.11 gigabecquerels, almost 25 times the inhalation LD50. Treatment failed, and he died 13 days after the exposure.
From 1955 to 1957, the Windscale Piles had been releasing polonium-210. Testing of the land downwind after the Windscale fire turned it up. The estimated release was 8.8 terabecquerels, or 240 curies.
Irène Joliot-Curie was accidentally exposed in 1946, when a sealed capsule of polonium exploded on her laboratory bench. She died of leukaemia in 1956, and it has been suggested that polonium's radiation was to blame.
In 1957, a leak was discovered at a laboratory of the Weizmann Institute in Israel. Traces of polonium-210 were found on the hands of Professor Dror Sadeh, a physicist who studied radioactive materials. Medical tests showed no harm, although they did not cover bone marrow. Over the next few years, Sadeh, one of his students and two colleagues died of various cancers. Several deaths between 1957 and 1969 have been alleged to stem from polonium. The matter was investigated in secret, and no connection was ever formally admitted.
The Church Rock uranium mill spill of the 16th of July 1979 is reported to have released polonium-210. Animals there carried higher concentrations of lead-210, polonium-210 and radium-226 than control animals.
Alexander Litvinenko, a former Russian FSB agent who had defected to the United Kingdom in 2001, died in 2006 of poisoning with a lethal dose of polonium-210. It was later determined that two Russian ex-security agents, Andrey Lugovoy and Dmitry Kovtun, had probably given it to him deliberately. His is the first, and so far the only, confirmed case of polonium's toxicity used with malicious intent. The Russian businessman Roman Tsepov is also suspected of having been killed with polonium, since his symptoms resembled Litvinenko's.
Yasser Arafat, the Palestinian leader, died on the 11th of November 2004 of uncertain causes. An allegation of polonium poisoning surfaced in 2011. In July 2012, the Institut de Radiophysique in Lausanne, Switzerland, found polonium-210 well above normal levels in his clothes and belongings. Yet his symptoms were acute gastroenteritis with diarrhoea and vomiting. The institute's spokesman said these were not consistent with polonium poisoning, and no conclusions could be drawn. In 2013, the team found levels in Arafat's ribs and pelvis 18 to 36 times the average, even though the amount had shrunk by a factor of 2 million. Forensic scientist Dave Barclay said, "In my opinion, it is absolutely certain that the cause of his illness was polonium poisoning." French and Russian teams later claimed the raised levels did not come from deliberate poisoning and did not cause his death.
Radon-222, a noble gas with a half-life of 3.8 days, starts the chain that puts polonium-210 into nearly every human body. It forms when natural uranium-238 in the Earth's crust decays through solid intermediates, including radium-226. Some radon diffuses into the atmosphere and decays through several more steps to polonium-210. Much of that polonium, with a half-life of 138 days, is washed back down to the surface. It enters the biosphere before finally decaying to stable lead-206.
As early as the 1920s, the French biologist Antoine Lacassagne used polonium supplied by his colleague Marie Curie to study rabbit tissues. He found high concentrations in the liver, kidney and testes. More recent evidence suggests polonium takes the place of its relative sulfur in sulfur-containing amino acids, and that human tissues show similar patterns. Polonium contributes appreciably to the natural background dose. The dose varies widely with geography and culture, and arctic residents carry particularly high levels. It also moves through the food chain, especially in seafood.
The polonium isotopes 214 and 218, born from radon, are thought to cause most of the estimated 15,000-22,000 lung cancer deaths a year in the US attributed to indoor radon.
Tobacco adds more. The presence of polonium in tobacco smoke has been known since the early 1960s. Most of it comes from lead-210 that settles on tobacco leaves from the air. That lead-210 is a product of radon-222, much of which appears to come from radium-226 in fertilizers applied to tobacco soils. Polonium-210 in tobacco contributes to many cases of lung cancer worldwide. Some of the world's biggest tobacco firms spent 40 years researching ways to remove the substance without success, and the results were never published.
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Common questions
Who discovered polonium and how was it found?
Marie Skłodowska-Curie and Pierre Curie discovered it in 1898. They extracted it from the uranium ore pitchblende and identified it solely by its strong radioactivity, making it the first element found that way.
Why is it called polonium?
It was named after Poland, Marie Skłodowska-Curie's homeland. Poland was then partitioned among Russia, Germany and Austria-Hungary, and she hoped the name would publicize its lack of independence.
What is polonium used for?
Its uses depend on its radioactivity. They include heat sources for space probes such as the Lunokhod Moon rovers, static-removing brushes, neutron and alpha particle sources, and, in the case of Alexander Litvinenko, poison.
How toxic is polonium-210?
By mass it is around 250,000 times more toxic than hydrogen cyanide. One estimate puts the median lethal dose at 0.089 micrograms, far less than a 60-microgram grain of table salt.
Is polonium found in nature?
Yes, in tiny traces. Uranium ores hold about 0.1 milligrams per metric ton. Polonium-210 also occurs in human tissues, tobacco smoke and seafood through the uranium-238 decay chain.
All sources
145 references cited across the entry
- 2JournalThe discovery of radioactivityPierre Radvanyi et al. — 1 November 2017
- 3Greenwood, p. 250
- 4210PO α decay2000
- 5Greenwood, p. 753
- 6BookInorganic ChemistryGary L. Miessler et al. — Pearson Prentice Hall — 2004
- 7The beta Po (A_i) Structure2000-11-20
- 8JournalThe structures of polonium and its compounds—I α and β polonium metalR. J. Desando — 1966
- 9JournalThe Crystal Structure of PoloniumW. H. Beamer — 1946
- 10JournalThe Crystal Structure of Polonium by Electron DiffractionM. A. Rollier et al. — 1936
- 11JournalThermochromatographic separation of 206,208Po from a bismuth target bombarded with protonsBogdan Wąs et al. — 2006
- 12Pseudo-evaporation of high specific activity alpha-emitting materialsCondit, Ralph H. et al. — Lawrence Livermore National Laboratory — 2014
- 13Bagnall, p. 206
- 14Bagnall, p. 199
- 15Greenwood, p. 766
- 16JournalChemie des PoloniumsF. Weigel — 1959
- 17BookInorganic ChemistryHolleman, A. F. — Academic Press — 2001
- 18Greenwood, pp. 765, 771, 775
- 20Bagnall, pp. 212–226
- 21BookEncyclopedia of Inorganic and Bioinorganic ChemistryRalph A. Zingaro — John Wiley & Sons — 2011
- 22JournalProduction of organopolonium compounds by using chemical alterations taking place during the β-decay of RaEA. N. Murin et al. — 1960
- 24JournalThe Preparation of Polonium Metal and Polonium DioxideK. W. Bagnall et al. — 1954
- 25JournalThe polonium halides. Part I. Polonium chloridesK. W. Bagnall et al. — 1955
- 26JournalThe polonium halides. Part II. BromidesK. W. Bagnall et al. — 1955
- 27Journal657. The polonium halides. Part III. Polonium tetraiodideK. W. Bagnall et al. — 1956
- 28BookThe Chemistry of the Actinide and Transactinide ElementsZenko Yoshida et al. — Springer — 2006
- 29BookThe Environmental Behaviour of PoloniumF. Carvalho et al. — International Atomic Energy Agency — 2017
- 30JournalSur une substance nouvelle radio-active, contenue dans la pechblendeCurie, P. et al. — 1898
- 3184. Polonium – Elementymology & Elements MultidictPeter van der Krogt
- 32JournalBorders of the Nuclear World – 100 Years After Discovery of PoloniumM. Pfützner — 1999
- 33JournalThe centennial of the 1903 Nobel Prize for physicsJ. P. Adloff — 2003
- 34JournalChemical and Polish aspects of polonium and radium discoveryK. Kabzinska — 1998
- 35JournalSur une nouvelle substance fortement radio-active contenue dans la pechblendeCurie, P. et al. — 1898
- 36JournalPolonium and Radio-Tellurium1906
- 37BookChronologie Chemie: Entdecker und EntdeckungenSieghard Neufeldt — John Wiley & Sons — 2012
- 39Restricted data declassification decisions, 1946 to the present (RDD-7)US Department of Energy Office of Declassification — 2001-01-01
- 41"Studies of polonium metabolism in human subjects", Chapter 3 in Biological Studies with Polonium, Radium, and Plutonium, National, Nuclear Energy Series, Volume VI-3, McGraw-Hill, New York, 1950, cit
- 43JournalOccurrence of the (4n + 1) series in natureD. F. Peppard et al. — 1952
- 44JournalThe Environmental Behaviour of PoloniumF. Carvalho et al. — International Atomic Energy Agency — 2017
- 45Greenwood, p. 746
- 46Bagnall, p. 198
- 47JournalCancer risk in relation to radioactivity in tobaccoGustave F. Kilthau — 1996
- 49JournalWaking a Sleeping Giant: The Tobacco Industry's Response to the Polonium-210 IssueE. Muggli Monique et al. — 2008
- 50JournalThe Dawn of RadiochemistryAdloff, J. P. — 1995
- 51Greenwood, p. 249
- 52JournalNeutronic Chain Reactions for Polonium-210 ProductionSolomon Lim — 2023
- 53JournalPyrochemical Extraction of Polonium from Irradiated Bismuth MetalWallace W. Schulz — 1969
- 54Q&A: Polonium-210RSC Chemistry World — 2006-11-27
- 55Most Polonium Made Near the Volga RiverThe Moscow Times – News — 2007-01-11
- 56JournalLong-lived radionuclides of sodium, lead-bismuth, and lead coolants in fast-neutron reactorsV. I. Usanov et al. — 1999
- 57JournalАтомная СтратегияNaumov, V. V. — November 2006
- 58JournalLight Polonium Isotopes from Carbon Ion Bombardments of PlatinumAtterling, H. — 1959
- 59Bagnall, p. 225
- 60PoloniumArgonne National Laboratory
- 61Greenwood, p. 251
- 62BookThe sun and space weatherArnold Hanslmeier — Springer — 2002
- 64BookSolar System LogAndrew Wilson — Jane's Publishing Company Ltd — 1987
- 65Comparative Study of Gamma to Neutron Ratios of various (alpha, neutron) Neutron SourcesSebastian Ritter — 2021
- 66BookNature's Building BlocksJohn Emsley — Oxford University Press — 2001
- 67BookDark Sun: The Making of the Hydrogen BombRhodes, Richard — Walker & Company — 2002
- 69JournalMortality Among Mound Workers Exposed to Polonium-210 and Other Sources of Radiation, 1944–1979John D. Boice et al. — 2014
- 71NewsBBC News : College breaches radioactive regulations2002-03-12
- 72Staticmaster Ionizing BrushesAMSTAT Industries
- 74Radioactive spark plugsOak Ridge Associated Universities — January 20, 1999
- 75PoloniumCassandra Pittman — University of Toledo — February 3, 2017
- 77Bagnall, pp. 202–6
- 78Polonium-210: Effects, symptoms, and diagnosis28 July 2017
- 79JournalFormation and emission of volatile polonium compound by microbial activity and polonium methylation with methylcobalaminN. Momoshima et al. — 2001
- 80JournalBiologically induced Po emission from fresh waterN. Momoshima et al. — 2002
- 81JournalMetabolism of 210Po in rats: volatile 210Po in excretaChunsheng Li et al. — 2010
- 84JournalEffective half-life of polonium in the humanNaimark, D.H. — 1949-01-04
- 85Polonium PoisoningCarey Sublette — 2006-12-14
- 86JournalPolonium-210 as a poisonJ. Harrison et al. — 2007
- 87Approximately how many atoms are in a grain of salt?Yasar Safkan
- 88BookHealth Risks of Radon and Other Internally Deposited Alpha-Emitters: BEIR IVNational Academy Press — 1988
- 89BookHealth Effects of Exposure to Indoor RadonNational Academy Press — 1999
- 91JournalSources of polonium Po and radio-lead Pb in human body in PolandAlicja Boryło et al. — 2022-02-10
- 92Nuclear Regulatory Commission limits for 210PoU.S. NRC — 2008-12-12
- 94JournalMetabolism and biological effects of polonium-210B. B. Moroz et al. — 1972
- 95JournalDiagnosis and treatment of polonium poisoningRobert D. Jefferson et al. — 2009
- 96JournalRadioactive Materials in Biosolids: National Survey, Dose Modeling & POTW GuidanceR.K. Bastian et al. — 2004-01-01
- 97NewsOpinion: The Smoky Bomb ThreatPeter D. Zimmerman — 2006-12-19
- 98Bagnall, p. 204.
- 99JournalBio-volatilization of polonium: Results from laboratory analysesN. Hussain et al. — 1995
- 100JournalPolonium-210 poisoning: a first-hand accountAmit C Nathwani et al. — 2016
- 102BookBiological studies with polonium, radium, and plutoniumRobert Fink — McGraw-Hill
- 103BookRadiacionnaja medicina: rukovodstvo dlja vračej-issledovatelej i organizatorov zdravooxranenija, Tom 2 (Radiacionnye poraženija čeloveka)G. N. Gasteva — IzdAT — 2001
- 104JournalPolonium-210 as a poisonJohn Harrison et al. — 2 March 2007
- 105NewsInnocent chemical a killerJeremy Manier — The Daily Telegraph (Australia) — 2006-12-04
- 106BookThe bomb in the basement: How Israel went nuclear and what that means for the worldMichael Karpin — Simon and Schuster — 2006
- 107NewsA restless killer radiates intrigueThomas Maugh — 2007-01-01
- 108The Church Rock uranium mill tailings spill a health and environmental assessment, page 32Jere Millard, Bruce Gallaher, David Baggett, Steven Gary — September 1983
- 109NewsThe mystery of Litvinenko's deathTom Geoghegan — 2006-11-24
- 110NewsUK requests Lugovoi extradition2007-05-28
- 111ReportThe Litvinenko Inquiry
- 112NewsLitvinenko 'probably murdered on personal orders of Putin'Esther Addley et al. — 21 January 2016
- 113NewsWho else was poisoned by polonium?Steve Boggan — 5 June 2007
- 114NewsPolonium: a silent killerDavid Poort — 6 November 2013
- 115Journal²¹⁰Po poisoning as possible cause of death: forensic investigations and toxicological analysis of the remains of Yasser ArafatPascal Froidevaux et al. — February 2016
- 116Newsالأخبار – ضابط فلسطيني: خصوم عرفات قتلوه عربيAl Jazeera — 17 January 2011
- 117George Galloway and Alex Goldfarb on Litvinenko inquiry21 January 2016
- 118JournalImproving forensic investigation for polonium poisoningP. Froidevaux et al. — 2013
- 120NewsPalestinian leader Yasser Arafat was murdered with polonium: widowPaul Taylor — Nov 7, 2013
- 121Swiss study: Polonium found in Arafat's bonesDavid Poort et al. — www.aljazeera.com — 6 November 2013
- 122NewsSwiss Team: Arafat Poisoned to Death With Polonium6 November 2013
- 125NewsArafat did not die of poisoning, French tests concludeReuters — 3 December 2013
- 126NewsThe Putin bodyguard riddle3 December 2006
- 128JournalReduction of subacute lethal radiotoxicity of polonium-210 in rats by chelating agentsRencováa J. — 1997
- 130JournalLead-210 and Polonium-210 in GrassC. R. Hill — 1960
- 131JournalNatural occurrence of unsupported radium-F (Po-210) in tissueC. R. Hill — 1963
- 132JournalPolonium-210 and lead-210 in marine food chainsM. Heyraud et al. — 1979
- 133Lacassagne, A. & Lattes, J. (1924) Bulletin d'Histologie Appliquée à la Physiologie et à la Pathologie, 1, 279.
- 134JournalBinding of Polonium-210 to Liver MetallothioneinH. Vasken Aposhian et al. — 1991
- 135JournalPolonium-210 in manC. R. Hill — 1965
- 136JournalPolonium-210 Content of Human Tissues in Relation to Dietary HabitC. R. Hill — 1966
- 137JournalRadioactivity of tobacco trichomes and insoluble cigarette smoke particlesE. A. Martell — 1974
- 138JournalTobacco Radioactivity and Cancer in Smokers: Alpha interactions with chromosomes of cells surrounding insoluble radioactive smoke particles may cause cancer and contribute to early atherosclerosis development in cigarette smokersE. A. Martell — 1975
- 139JournalThe big idea: polonium, radon and cigarettesM. J. Tidd — 2008
- 141JournalPolonium 210: a volatile radioelement in cigarettesRadford EP Jr — 1964
- 142JournalPolonium 210 content of mainstream cigarette smokeKelley TF — 1965
- 143JournalEvaluation for Committed Effective Dose Due to Dietary Foods by the Intake for Japanese AdultsOta, Tomoko — 2009
- 144JournalMeasurement of natural radionuclides in U.K. dietSmith-Briggs, JL — 1984
- 145BookAdvances in Inorganic Chemistry and RadiochemistryK. W. Bagnall — Academic Press — 1962
- 146BookChemistry of the ElementsGreenwood, Norman N. — Butterworth–Heinemann — 1997