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{{infobox polonium}}
'''Polonium''' is a [[Chemistry:Chemical element|chemical element]]; it has [[Chemistry:Symbol|symbol]] '''Po''' and [[Physics:Atomic number|atomic number]] 84. A rare and highly [[Physics:Radioactive|radioactive]] [[Chemistry:Metal|metal]] (although sometimes classified as a [[Chemistry:Metalloid|metalloid]]) with no stable [[Physics:Isotopes of polonium|isotopes]], polonium is a [[Chemistry:Chalcogen|chalcogen]] and chemically similar to [[Chemistry:Selenium|selenium]] and [[Chemistry:Tellurium|tellurium]], though its metallic character resembles that of its [[Chemistry:Period 6 element|horizontal neighbors]] in the [[Chemistry:Periodic table|periodic table]]: [[Chemistry:Thallium|thallium]], [[Chemistry:Lead|lead]], and [[Chemistry:Bismuth|bismuth]]. Due to the short [[Physics:Half-life|half-life]] of all its isotopes, its natural occurrence is limited to tiny traces of the fleeting [[Physics:Polonium-210|polonium-210]] (with a half-life of 138 days) in [[Chemistry:Uranium|uranium]] [[Earth:Ore|ore]]s, as it is the [[Physics:Decay chain|penultimate daughter]] of natural [[Physics:Uranium-238#Radium series (or uranium series)|uranium-238]]. Though longer-lived isotopes exist, such as the 124 years half-life of polonium-209, they are much more difficult to produce. Today, polonium is usually produced in milligram quantities by the neutron irradiation of [[Chemistry:Bismuth|bismuth]]. Due to its intense radioactivity, which results in the [[Physics:Radiolysis|radiolysis]] of chemical bonds and radioactive self-heating, its chemistry has mostly been investigated on the trace scale only.

Polonium was discovered in July 1898 by [[Biography:Marie Curie|Marie Skłodowska-Curie]] and [[Biography:Pierre Curie|Pierre Curie]], when it was extracted from the uranium ore pitchblende and identified solely by its strong radioactivity: it was the first element to be so discovered. Polonium was named after Marie Curie's homeland of {{wipe|Poland}}. Polonium has few applications, and those are related to its radioactivity: heaters in [[Engineering:Space probe|space probe]]s, [[Physics:Antistatic device|antistatic device]]s, sources of [[Physics:Neutron|neutron]]s and [[Physics:Alpha particle|alpha particle]]s, and [[Chemistry:Poison|poison]] e.g. poisoning of Alexander Litvinenko. It is extremely dangerous to humans.

==Characteristics==

<sup>210</sup>Po is an [[Physics:Alpha decay|alpha emitter]] that has a half-life of 138.4&nbsp;days; it decays directly to its stable [[Physics:Decay product|daughter isotope]], [[Chemistry:Lead|<sup>206</sup>Pb]]. A milligram (5&nbsp;[[Physics:Curie (unit)|curie]]s) of <sup>210</sup>Po emits about as many alpha particles per second as 5&nbsp;grams of [[Chemistry:Radium|<sup>226</sup>Ra]],<ref name="anl" /> which means it is 5,000 times more radioactive than radium. A few [[Physics:Curie (unit)|curie]]s (1&nbsp;curie equals 37&nbsp;[[Becquerel|gigabecquerels]], 1&nbsp;Ci = 37&nbsp;GBq) of <sup>210</sup>Po emit a blue glow which is caused by [[Astronomy:Ionized-air glow|ionisation]] of the surrounding air.

About one in 100,000&nbsp;alpha emissions causes an excitation in the nucleus which then results in the emission of a [[Physics:Gamma ray|gamma ray]] with a maximum energy of 803&nbsp;keV.<ref>Greenwood, p. 250</ref><ref>{{cite web|url=http://atom.kaeri.re.kr/cgi-bin/decay?Po-210%20A|title=210PO α decay|work=Nuclear Data Center, Korea Atomic Energy Research Institute|date= 2000|access-date=2009-05-05}}</ref>

===Solid state form===
[[File:alpha po lattice.jpg|thumb|left|The alpha form of solid polonium]]
Polonium is a radioactive element that exists in two [[Chemistry:Metal|metal]]lic allotropes. The alpha form is the only known example of a simple cubic crystal structure in a single atom basis at [[Standard conditions for temperature and pressure|STP]] ([[Space group|space group]] Pm{{overline|3}}m, no. 221). The unit cell has an edge length of 335.2 picometers; the beta form is rhombohedral.<ref>Greenwood, p. 753</ref><ref>{{cite book |first1=Gary L. |last1=Miessler |first2=Donald A. |last2=Tarr |title=Inorganic Chemistry |edition=3rd |page=[https://archive.org/details/inorganicchemist03edmies/page/285 285] |isbn=978-0-13-120198-9 |date=2004 |publisher=Pearson Prentice Hall |location=Upper Saddle River, N.J. |url=https://archive.org/details/inorganicchemist03edmies/page/285 }}</ref><ref>{{cite web| url = http://cst-www.nrl.navy.mil/lattice/struk/a_i.html| archive-url = https://web.archive.org/web/20010204004200/http://cst-www.nrl.navy.mil/lattice/struk/a_i.html| archive-date = 2001-02-04|date= 2000-11-20|work=Naval Research Laboratory |title = The beta Po (A_i) Structure| access-date = 2009-05-05}}</ref> The structure of polonium has been characterized by [[Physics:X-ray|X-ray]] [[Physics:Diffraction|diffraction]]<ref>{{cite journal |last=Desando |first=R. J. |author2=Lange, R. C. |date=1966 |title=The structures of polonium and its compounds—I α and β polonium metal |journal=Journal of Inorganic and Nuclear Chemistry |volume=28 |issue=9 |pages=1837–1846 |doi=10.1016/0022-1902(66)80270-1}}</ref><ref>{{cite journal |last=Beamer |first=W. H. |author2=Maxwell, C. R. |date=1946 |title=The Crystal Structure of Polonium |journal=Journal of Chemical Physics |volume=14 |issue=9 |page=569 |doi=10.1063/1.1724201|hdl=2027/mdp.39015086430371 |hdl-access=free }}</ref> and [[Physics:Electron diffraction|electron diffraction]].<ref>{{cite journal |last1=Rollier |first1=M. A. |last2=Hendricks |first2=S. B.|last3= Maxwell|first3=L. R. |date=1936 |title=The Crystal Structure of Polonium by Electron Diffraction |journal=Journal of Chemical Physics |volume=4 |issue=10 |page=648 |doi=10.1063/1.1749762 |bibcode = 1936JChPh...4..648R|doi-access=free }}</ref>

<sup>210</sup>Po (in common with [[Physics:Plutonium-238|<sup>238</sup>Pu]]{{citation needed|reason=I found no mention of this at the page for plutonium-238.|date=April 2019}}) has the ability [[Chemistry:Volatility|to become airborne with ease]]: if a sample is heated in air to {{convert|55|C|F}}, 50% of it is vaporized in 45 hours to form [[Chemistry:Diatomic molecule|diatomic]] Po<sub>2</sub> molecules, even though the melting point of polonium is {{convert|254|C|F}} and its boiling point is {{convert|962|C|F}}.<ref>{{cite journal| first1 = Bogdan |last1=Wąs| first2 = Ryszard |last2=Misiak| first3 = Mirosław |last3=Bartyzel| first4 = Barbara |last4=Petelenz | title = Thermochromatographic separation of <sup>206,208</sup>Po from a bismuth target bombarded with protons | journal =Nukleonika | date =2006| volume =51 | issue = Suppl. 2 | pages = s3–s5 | url =http://www.ichtj.waw.pl/ichtj/nukleon/back/full/vol51_2006/v51s2p03f.pdf}}</ref><ref name="CRC">{{RubberBible86th}}</ref><ref name="Thayer p78" />
More than one hypothesis exists for how polonium does this; one suggestion is that small clusters of polonium atoms are [[Physics:Spallation|spalled off]] by the alpha decay.<ref>{{cite conference|title=Pseudo-evaporation of high specific activity alpha-emitting materials|author1= Condit, Ralph H.|author2=Gray, Leonard W.| author3=Mitchell, Mark A.|url=https://www.osti.gov/biblio/1162255| conference=EFCOG 2014 Safety Analysis Workshop|year=2014|publisher=Lawrence Livermore National Laboratory|osti= 1162255|conference-url=https://www.osti.gov/biblio/1169821}}</ref>

===Chemistry===
The chemistry of polonium is similar to that of [[Chemistry:Tellurium|tellurium]], although it also shows some similarities to its neighbor [[Chemistry:Bismuth|bismuth]] due to its metallic character. Polonium dissolves readily in dilute [[Chemistry:Acid|acid]]s but is only slightly [[Chemistry:Solubility|soluble]] in [[Chemistry:Alkali|alkali]]s. Polonium [[Chemistry:Solution|solution]]s are first colored in pink by the Po<sup>2+</sup> ions, but then rapidly become yellow because alpha radiation from polonium ionizes the solvent and converts Po<sup>2+</sup> into Po<sup>4+</sup>. As polonium also emits alpha-particles after disintegration so this process is accompanied by bubbling and emission of heat and light by glassware due to the absorbed alpha particles; as a result, polonium solutions are volatile and will evaporate within days unless sealed.<ref name="nbb" /><ref>Bagnall, p. 206</ref> At pH about 1, polonium ions are readily hydrolyzed and complexed by acids such as [[Chemistry:Oxalic acid|oxalic acid]], [[Chemistry:Citric acid|citric acid]], and [[Chemistry:Tartaric acid|tartaric acid]].<ref>{{Ullmann | first1=Cornelius |last1=Keller |first2=Walter |last2=Wolf |first3=Jashovam |last3=Shani | title = Radionuclides, 2. Radioactive Elements and Artificial Radionuclides | doi = 10.1002/14356007.o22_o15}}</ref>

====Compounds====
Polonium has no common compounds, and almost all of its compounds are synthetically created; more than 50 of those are known.<ref>Bagnall, p. 199</ref> The most stable class of polonium compounds are [[Chemistry:Polonide|polonide]]s, which are prepared by direct reaction of two elements. [[Chemistry:Sodium polonide|Na<sub>2</sub>Po]] has the antifluorite structure, the polonides of [[Chemistry:Calcium polonide|Ca]], Ba, Hg, Pb and lanthanides form a NaCl lattice, BePo and CdPo have the [[Chemistry:Wurtzite|wurtzite]] and [[Chemistry:Magnesium polonide|MgPo]] the nickel arsenide structure. Most polonides decompose upon heating to about 600&nbsp;°C, except for HgPo that decomposes at ~300&nbsp;°C and the [[Chemistry:Lanthanide|lanthanide]] polonides, which do not decompose but melt at temperatures above 1000&nbsp;°C. For example, the polonide of [[Chemistry:Praseodymium|praseodymium]] (PrPo) melts at 1250&nbsp;°C, and that of [[Chemistry:Thulium|thulium]] (TmPo) melts at 2200&nbsp;°C.<ref name="g766">Greenwood, p. 766</ref> [[Chemistry:Lead polonide|PbPo]] is one of the very few naturally occurring polonium compounds, as polonium [[Physics:Alpha decay|alpha decay]]s to form [[Chemistry:Lead|lead]].<ref>{{cite journal |last1=Weigel |first1=F. |date=1959 |title=Chemie des Poloniums |journal=[[Chemistry:Angewandte Chemie|Angewandte Chemie]] |volume=71 |pages=289–316 |doi=10.1002/ange.19590710902 |issue=9|bibcode=1959AngCh..71..289W }}</ref>

[[Chemistry:Polonium hydride|Polonium hydride]] ({{chem|Po||H|2}}) is a volatile liquid at room temperature prone to dissociation; it is thermally unstable.<ref name="g766" /> [[Chemistry:Properties of water|Water]] is the only other known [[Chemistry:Hydrogen chalcogenide|hydrogen chalcogenide]] which is a liquid at room temperature; however, this is due to hydrogen bonding. The three oxides, [[Chemistry:Polonium monoxide|PoO]], [[Chemistry:Polonium dioxide|PoO<sub>2</sub>]] and [[Chemistry:Polonium trioxide|PoO<sub>3</sub>]], are the products of oxidation of polonium.<ref>{{cite book| author = Holleman, A. F.| author2 = Wiberg, E. |title = Inorganic Chemistry| publisher = Academic Press| location = San Diego| date = 2001| isbn = 978-0-12-352651-9}}</ref>

[[Chemistry:Halide|Halide]]s of the structure PoX<sub>2</sub>, PoX<sub>4</sub> and PoF<sub>6</sub> are known. They are soluble in the corresponding hydrogen halides, i.e., PoCl<sub>X</sub> in HCl, PoBr<sub>X</sub> in HBr and PoI<sub>4</sub> in HI.<ref name="figgins" /> Polonium dihalides are formed by direct reaction of the elements or by reduction of PoCl<sub>4</sub> with SO<sub>2</sub> and with PoBr<sub>4</sub> with H<sub>2</sub>S at room temperature. Tetrahalides can be obtained by reacting polonium dioxide with HCl, HBr or HI.<ref name="g765">Greenwood, pp. 765, 771, 775</ref>

Other polonium compounds include the polonite, potassium polonite; various polonate solutions; and the [[Chemistry:Acetate|acetate]], [[Chemistry:Bromate|bromate]], [[Chemistry:Carbonate|carbonate]], [[Chemistry:Citrate|citrate]], [[Chemistry:Chromate ion|chromate]], cyanide, [[Chemistry:Formate|formate]], (II) or (IV) hydroxide, [[Chemistry:Polonium tetranitrate|nitrate]], selenate, selenite, monosulfide, [[Chemistry:Sulfate|sulfate]], disulfate or sulfite salts.<ref name="figgins">Figgins, P. E. (1961) [http://www.osti.gov/bridge/purl.cover.jsp?purl=/4034029-SolPsF/ The Radiochemistry of Polonium], National Academy of Sciences, US Atomic Energy Commission, pp. 13–14 [https://books.google.com/books?id=N0MrAAAAYAAJ Google Books]</ref><ref>Bagnall, pp. 212–226</ref>

A limited organopolonium chemistry is known, mostly restricted to dialkyl and diaryl polonides (R<sub>2</sub>Po), triarylpolonium halides (Ar<sub>3</sub>PoX), and diarylpolonium dihalides (Ar<sub>2</sub>PoX<sub>2</sub>).<ref name="Z">{{cite book |last=Zingaro |first=Ralph A. |chapter=Polonium: Organometallic Chemistry |date=2011 |title=Encyclopedia of Inorganic and Bioinorganic Chemistry |publisher=John Wiley & Sons |pages=1–3 |doi=10.1002/9781119951438.eibc0182|isbn=9781119951438 }}</ref><ref name="M">{{cite journal |last1=Murin |first1=A. N. |last2=Nefedov |first2=V. D. |first3=V. M. |last3=Zaitsev |first4=S. A. |last4=Grachev |date=1960 |title=Production of organopolonium compounds by using chemical alterations taking place during the β-decay of RaE |url=http://www.mathnet.ru/links/d4bd811f2ded6e2b1d67f43a93e2910e/dan23789.pdf |journal=Dokl. Akad. Nauk SSSR |volume=133 |issue=1 |pages=123–125 |access-date=12 April 2020 |language=ru}}</ref> Polonium also forms soluble compounds with some chelating agents, such as 2,3-butanediol and [[Chemistry:Thiourea|thiourea]].<ref name="Z" />

{|class="wikitable" style="text-align:center"
|+Polonium compounds<ref name="g765" /><ref>Wiberg, Egon; Holleman, A. F. and Wiberg, Nils [https://books.google.com/books?id=Mtth5g59dEIC&pg=PA594 Inorganic Chemistry], Academic Press, 2001, p. 594, {{ISBN|0-12-352651-5}}.</ref>
|-
!Formula!!Color!! [[Physics:Melting point|m.p.]] (°C)|| [[Sublimation (phase transition)|Sublimation]] <br/>temp. (°C) ||Symmetry||[[Physics:Pearson symbol|Pearson symbol]] || [[Space group]] ||No||a (pm) || b(pm) || c(pm) || Z || [[Physics:Density|ρ]] (g/cm<sup>3</sup>) ||ref
|-
|[[Chemistry:Polonium monoxide|PoO]]|| black|| || || || || || || || || || || ||
|-
|[[Chemistry:Polonium dioxide|PoO<sub>2</sub>]]|| pale yellow|| 500 (dec.) ||885 ||fcc ||cF12||Fm{{overline|3}}m ||225 ||563.7||563.7||563.7||4|| 8.94 || <ref name="Bagnall">{{cite journal |last1=Bagnall |first1=K. W. |last2=d'Eye |first2=R. W. M. |date=1954 |title=The Preparation of Polonium Metal and Polonium Dioxide |journal=[[Organization:Journal of the Chemical Society|J. Chem. Soc.]] |pages=4295–4299|doi=10.1039/JR9540004295 }}</ref>
|-
|[[Chemistry:Polonium hydride|PoH<sub>2</sub>]]|| || -35.5 || || || || || || || || || || ||
|-
|[[Chemistry:Polonium dichloride|PoCl<sub>2</sub>]]|| dark ruby red|| 355 ||130 ||[[Chemistry:Orthorhombic|orthorhombic]] ||oP3||Pmmm||47 ||367||435||450||1|| 6.47 || <ref name="PoCl">{{cite journal|doi=10.1039/JR9550002320|title=The polonium halides. Part I. Polonium chlorides|date=1955|last1=Bagnall|first1=K. W.|last2=d'Eye|first2=R. W. M.|last3=Freeman|first3=J. H.|journal=Journal of the Chemical Society (Resumed)|page=2320}}</ref>
|-
|[[Chemistry:Polonium dibromide|PoBr<sub>2</sub>]]||purple-brown|| 270 (dec.)|| || || || || || || || || || ||<ref name="PoBr">{{cite journal|doi=10.1039/JR9550003959|title=The polonium halides. Part II. Bromides|date=1955|last1=Bagnall|first1=K. W.|last2=d'Eye|first2=R. W. M.|last3=Freeman|first3=J. H.|journal=Journal of the Chemical Society (Resumed)|page=3959}}</ref>
|-
|[[Chemistry:Polonium tetrachloride|PoCl<sub>4</sub>]]|| yellow||300 || 200 ||[[Chemistry:Monoclinic|monoclinic]] || || || || || || || || ||<ref name="PoCl" />
|-
|[[Chemistry:Polonium tetrabromide|PoBr<sub>4</sub>]]|| red||330 (dec.) || ||fcc || cF100 || Fm{{overline|3}}m ||225||560||560||560||4|| || <ref name="PoBr" />
|-
|[[Chemistry:Polonium tetraiodide|PoI<sub>4</sub>]]||black || || || || || || || || || || || || <ref>{{cite journal|doi=10.1039/JR9560003385|title=657. The polonium halides. Part III. Polonium tetraiodide|date=1956|last1=Bagnall|first1=K. W.|last2=d'Eye|first2=R. W. M.|last3=Freeman|first3=J. H.|journal=Journal of the Chemical Society (Resumed)|page=3385}}</ref>
|}
{{col-begin}}
{{col-break}}
'''Oxides'''
* [[Chemistry:Polonium monoxide|PoO]]
* [[Chemistry:Polonium dioxide|PoO<sub>2</sub>]]
* [[Chemistry:Polonium trioxide|PoO<sub>3</sub>]]
{{col-break}}
'''Hydrides'''
* [[Chemistry:Polonium hydride|PoH<sub>2</sub>]]
{{col-break}}
'''[[Chemistry:Halide|Halide]]s'''
* PoX<sub>2</sub> (except PoF<sub>2</sub>)
* PoX<sub>4</sub>
* [[Chemistry:Polonium hexafluoride|PoF<sub>6</sub>]]
* PoBr<sub>2</sub>Cl<sub>2</sub> (salmon pink)
{{col-end}}

===Isotopes===
{{Main|Physics:Isotopes of polonium}}
Polonium has 42 known isotopes, all of which are radioactive. They have [[Physics:Atomic mass|atomic mass]]es that range from 186 to 227 u. [[Physics:Polonium-210|<sup>210</sup>Po]] (half-life 138.376&nbsp;days) is the most widely available and is made via neutron capture by natural [[Chemistry:Bismuth|bismuth]]. The longer-lived <sup>209</sup>Po (half-life 124 years, longest-lived of all polonium isotopes){{NUBASE2020|ref}} and <sup>208</sup>Po (half-life 2.9&nbsp;years) can be made through the alpha, proton, or deuteron bombardment of [[Chemistry:Lead|lead]] or bismuth in a [[Physics:Cyclotron|cyclotron]].<ref name="emsley">{{cite book|last=Emsley|first=John|title=Nature's Building Blocks: An A-Z Guide to the Elements|edition=New|date=2011|publisher=Oxford University Press|location=New York, NY|isbn=978-0-19-960563-7|page=415}}</ref>

==History==
Tentatively called "[[Chemistry:Radium#History|radium F]]", polonium was discovered by [[Biography:Marie Curie|Marie]] and Pierre Curie in July 1898,<ref name="c1">{{cite journal|author1=Curie, P. |author2=Curie, M. |title=Sur une substance nouvelle radio-active, contenue dans la pechblende |trans-title=On a new radioactive substance contained in pitchblende |language=fr |journal=Comptes Rendus |volume=127 |pages=175–178 |date=1898 |url=http://www.academie-sciences.fr/activite/archive/dossiers/Curie/Curie_pdf/CR1898_p175_178.pdf |url-status=unfit |archive-url=https://web.archive.org/web/20130723022419/http://www.academie-sciences.fr/activite/archive/dossiers/Curie/Curie_pdf/CR1898_p175_178.pdf |archive-date=July 23, 2013 }} [http://web.lemoyne.edu/~giunta/curiespo.html English translation.]</ref><ref>{{Cite web|url=http://elements.vanderkrogt.net/element.php?sym=po|title=84. Polonium – Elementymology & Elements Multidict|last=Krogt|first=Peter van der|website=elements.vanderkrogt.net|access-date=2017-04-26}}</ref> and was named after Marie Curie's native land of {{wipe|Poland}} ({{lang-la|Polonia}}).<ref>{{cite journal
| title = Borders of the Nuclear World – 100 Years After Discovery of Polonium
| last = Pfützner | first =M.
| journal = Acta Physica Polonica B
| volume = 30
| issue = 5 | date = 1999
| page= 1197
| bibcode =1999AcPPB..30.1197P}}</ref><ref>{{cite journal
| title = The centennial of the 1903 Nobel Prize for physics
| last = Adloff | first = J. P.
| journal =  Radiochimica Acta
| volume = 91
| issue = 12–2003
| pages=681–688
| date=2003
| doi = 10.1524/ract.91.12.681.23428| s2cid = 120150862 }}</ref> Poland at the time was under [[Place:Russian Empire|Russian]], [[Place:German Empire|German]], and Austro-Hungarian 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.<ref name="Przemysl">{{cite journal
| title = Chemical and Polish aspects of polonium and radium discovery
| last = Kabzinska | first =K.
| journal = Przemysł Chemiczny
| volume = 77
| date = 1998
| pages = 104–107
| issue = 3}}</ref>

This element was the first one discovered by the Curies while they were investigating the cause of [[Chemistry:Uraninite|pitchblende]] radioactivity. Pitchblende, after removal of the radioactive elements [[Chemistry:Uranium|uranium]] and [[Chemistry:Thorium|thorium]], was more radioactive than the uranium and thorium combined. This spurred the Curies to search for additional radioactive elements. They first separated out polonium from pitchblende in July 1898, and five months later, also isolated [[Chemistry:Radium|radium]].<ref name="nbb" /><ref name="c1" /><ref name="c2">{{cite journal |author1=Curie, P. |author2=Curie, M. |author3=Bémont, G. |title=Sur une nouvelle substance fortement radio-active contenue dans la pechblende |trans-title=On a new, strongly radioactive substance contained in pitchblende |language=fr |journal=Comptes Rendus |volume=127 |pages=1215–1217 |date=1898 |url=http://www.academie-sciences.fr/activite/archive/dossiers/Curie/Curie_pdf/CR1898_p1215_1217.pdf |archive-url=https://web.archive.org/web/20130722232602/http://www.academie-sciences.fr/activite/archive/dossiers/Curie/Curie_pdf/CR1898_p1215_1217.pdf |archive-date=July 22, 2013 }} [http://www.aip.org/history/curie/discover.htm English translation] {{Webarchive|url=https://web.archive.org/web/20090806083923/http://www.aip.org/history/curie/discover.htm |date=6 August 2009 }}</ref> German scientist Willy Marckwald successfully isolated 3 milligrams of polonium in 1902, though at the time he believed it was a new element, which he dubbed "radio-tellurium", and it was not until 1905 that it was demonstrated to be the same as polonium.<ref>{{cite journal | title = Polonium and Radio-Tellurium | journal = Nature | volume = 73 | issue = 549 | pages = 549 |date = 1906 | doi = 10.1038/073549b0| bibcode = 1906Natur..73R.549. | doi-access = free }}</ref><ref>{{cite book |last = Neufeldt |first = Sieghard | title = Chronologie Chemie: Entdecker und Entdeckungen | publisher = John Wiley & Sons | year = 2012 | isbn = 9783527662845 | url = {{Google books|0lFQjLAlgC0C|plainurl=y|page=115}} }}</ref>

In the United States, polonium was produced as part of the [[Physics:Manhattan Project|Manhattan Project]]'s Dayton Project during [[Social:World War II|World War II]]. Polonium and [[Chemistry:Beryllium|beryllium]] were the key ingredients of the '[[Physics:Modulated neutron initiator#Urchin|Urchin]]' initiator at the center of the bomb's spherical [[Physics:Pit (nuclear weapon)|pit]].<ref name="nwfaq41">[http://nuclearweaponarchive.org/Nwfaq/Nfaq4-1.html Nuclear Weapons FAQ, Section 4.1, Version 2.04: 20 February 1999]. Nuclearweaponarchive.org. Retrieved on 2013-04-28.</ref> 'Urchin' initiated the [[Physics:Nuclear fission|nuclear chain reaction]] at the moment of prompt-criticality to ensure that the weapon did not fizzle. 'Urchin' was used in early U.S. weapons; subsequent U.S. weapons utilized a pulse neutron generator for the same purpose.<ref name="nwfaq41" />

Much of the basic physics of polonium was classified until after the war. The fact that a polonium-beryllium (Po-Be) initiator was used in the gun-type nuclear weapons was classified until the 1960s.<ref name="FAS_Project">{{cite web | author=US Department of Energy Office of Declassification | title=Restricted data declassification decisions, 1946 to the present (RDD-7) | website=FAS Project on Government Secrecy (1991-2021), fas.org | date=2001-01-01 | url=https://sgp.fas.org/othergov/doe/rdd-7.html#I16 | access-date=2024-01-30}}</ref>

The Atomic Energy Commission and the [[Physics:Manhattan Project|Manhattan Project]] funded human experiments using polonium on five people at the [[Organization:University of Rochester|University of Rochester]] between 1943 and 1947. The people were administered between {{convert|9|and|22|µCi|kBq|lk=on}} of polonium to study its [[Biology:Excretion|excretion]].<ref name="congress1986">[http://contentdm.library.unr.edu/cdm4/item_viewer.php?CISOROOT=/conghear&CISOPTR=102&CISOBOX=1&REC=1#metajump American nuclear guinea pigs: three decades of radiation experiments on U.S. citizens] {{Webarchive|url=https://web.archive.org/web/20130730200210/http://contentdm.library.unr.edu/cdm4/item_viewer.php?CISOROOT=%2Fconghear&CISOPTR=102&CISOBOX=1&REC=1#metajump |date=2013-07-30 }}. United States. Congress. House. of the Committee on Energy and Commerce. Subcommittee on Energy Conservation and Power, published by U.S. Government Printing Office, 1986, Identifier Y 4.En 2/3:99-NN, Electronic Publication Date 2010, at the University of Nevada, Reno, unr.edu</ref><ref name="nes1950">"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, cited in "American Nuclear Guinea Pigs&nbsp;...", 1986 House Energy and Commerce committee report</ref><ref>Moss, William and Eckhardt, Roger (1995) [https://fas.org/sgp/othergov/doe/lanl/pubs/00326640.pdf "The Human Plutonium Injection Experiments"], Los Alamos Science, Number 23.</ref>

==Occurrence and production==
Polonium is a very rare element in nature because of the short half-lives of all its isotopes. Nine isotopes, from 210 to 218 inclusive, occur in [[Physics:Trace radioisotope|traces]] as decay products: <sup>210</sup>Po, <sup>214</sup>Po, and <sup>218</sup>Po occur in the [[Physics:Decay chain|decay chain]] of [[Physics:Uranium-238|<sup>238</sup>U]]; <sup>211</sup>Po and <sup>215</sup>Po occur in the decay chain of [[Physics:Uranium-235|<sup>235</sup>U]]; <sup>212</sup>Po and <sup>216</sup>Po occur in the decay chain of [[Physics:Thorium-232|<sup>232</sup>Th]]; and <sup>213</sup>Po and <sup>217</sup>Po occur in the decay chain of [[Physics:Neptunium-237|<sup>237</sup>Np]]. (No primordial <sup>237</sup>Np survives, but traces of it are continuously regenerated through (n,2n) knockout reactions in natural <sup>238</sup>U.)<ref name=4n1>{{cite journal |last1=Peppard |first1=D. F. |last2=Mason |first2=G. W. |last3=Gray |first3=P. R. |last4=Mech |first4=J. F. |title=Occurrence of the (4n + 1) series in nature |journal=Journal of the American Chemical Society |date=1952 |volume=74 |issue=23 |pages=6081–6084 |doi=10.1021/ja01143a074 |url=https://digital.library.unt.edu/ark:/67531/metadc172698/m2/1/high_res_d/metadc172698.pdf }}</ref> Of these, <sup>210</sup>Po is the only isotope with a half-life longer than 3&nbsp;minutes.<ref name="po484">{{Cite book| last1=Carvalho|first1=F.|last2=Fernandes|first2=S.|last3=Fesenko|first3=S. |last4=Holm|first4=E.|last5=Howard|first5=B.|last6=Martin|first6=P.|last7=Phaneuf|first7=P. |last8=Porcelli|first8=D.|last9=Pröhl|first9=G.|last10=Twining|first10=J.|title=The Environmental Behaviour of Polonium|journal=Technical Reports Series – International Atomic Energy Agency|series=Technical reports series|volume=484|publisher=International Atomic Energy Agency|location=Vienna|date=2017|page=1|isbn=978-92-0-112116-5}}</ref>

Polonium can be found in [[Chemistry:Uranium|uranium]] ores at about 0.1&nbsp;mg per metric ton (1 part in 10<sup>10</sup>),<ref>Greenwood, p. 746</ref><ref>Bagnall, p. 198</ref> 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 [[Chemistry:Tobacco smoke|tobacco smoke]] from tobacco leaves grown with [[Chemistry:Phosphate|phosphate]] fertilizers.<ref>{{cite journal| last = Kilthau | first = Gustave F. |title = Cancer risk in relation to radioactivity in tobacco |journal = Radiologic Technology |volume = 67 |pages = 217–222| pmid = 8850254| date = 1996| issue = 3}}</ref><ref>{{cite web|url=http://kidslink.bo.cnr.it/besta/fumo/epolonio.html |title=Alpha Radioactivity (210 Polonium) and Tobacco Smoke |access-date=2009-05-05 |url-status=dead |archive-url=https://web.archive.org/web/20130609055245/http://kidslink.bo.cnr.it/besta/fumo/epolonio.html |archive-date=June 9, 2013 }}</ref><ref name="Muggli08">{{cite journal |title = Waking a Sleeping Giant: The Tobacco Industry's Response to the Polonium-210 Issue |last1 = Monique | first1 = E. Muggli |journal = American Journal of Public Health |volume = 98 |issue = 9| date = 2008 |pmid = 18633078|pmc = 2509609 |doi = 10.2105/AJPH.2007.130963 |pages = 1643–50 |last2 = Ebbert |first2 = Jon O. |last3 = Robertson |first3 = Channing |last4 = Hurt |first4 = Richard D.}}</ref>

Because it is present in small concentrations, isolation of polonium from natural sources is a tedious process. The largest batch of the element ever extracted, performed in the first half of the 20th century, contained only {{convert|40|Ci|TBq|abbr=on}} (9&nbsp;mg) of [[Physics:Polonium-210|polonium-210]] and was obtained by processing 37 tonnes of residues from radium production.<ref>{{cite journal|author=Adloff, J. P.|author2=MacCordick, H. J.|name-list-style=amp |title=The Dawn of Radiochemistry|journal=Radiochimica Acta |volume=70/71|pages= 13–22 |date=1995|url=http://www.nucleonica.com/wiki/Articles/Article03/Article3.htm |doi=10.1524/ract.1995.7071.special-issue.13|s2cid=99790464}}, reprinted in {{cite book|url = https://books.google.com/books?id=whGiCQywLi8C&pg=PA17|title = One hundred years after the discovery of radioactivity|isbn = 978-3-486-64252-0|last1 = Adloff|first1= J. P.|date = 1996|page=17| publisher=Walter de Gruyter GmbH }}</ref> Polonium is now usually obtained by irradiating bismuth with high-energy neutrons or protons.<ref name="nbb" /><ref name="g249">Greenwood, p. 249</ref>

In 1934, an experiment showed that when natural [[Physics:Bismuth-209|<sup>209</sup>Bi]] is bombarded with [[Physics:Neutron|neutron]]s, <sup>210</sup>Bi is created, which then decays to <sup>210</sup>Po via beta-minus decay. By irradiating certain bismuth salts containing light element nuclei such as beryllium, a cascading (α,n) reaction can also be induced to produce <sup>210</sup>Po in large quantities.<ref>{{cite journal |title =Neutronic Chain Reactions for Polonium-210 Production |first =Solomon |last = Lim |journal = SSRN |date = 2023 |doi = 10.2139/ssrn.4469519|s2cid =264176122 }}</ref> The final purification is done pyrochemically followed by liquid-liquid extraction techniques.<ref>{{cite journal |title =Pyrochemical Extraction of Polonium from Irradiated Bismuth Metal |first =Wallace W. |last = Schulz |author2 = Schiefelbein, Gary F. |author3 = Bruns, Lester E. |journal = Ind. Eng. Chem. Process Des. Dev. |date = 1969 |volume = 8 |issue = 4 |pages= 508–515| doi = 10.1021/i260032a013}}</ref> Polonium may now be made in milligram amounts in this procedure which uses high neutron fluxes found in [[Physics:Nuclear reactor|nuclear reactor]]s.<ref name="g249" /> Only about 100&nbsp;grams are produced each year, practically all of it in Russia, making polonium exceedingly rare.<ref>{{cite web |title = Q&A: Polonium-210 |url =http://www.rsc.org/chemistryworld/News/2006/November/27110601.asp |publisher = RSC Chemistry World |date = 2006-11-27 |access-date =2009-01-12}}</ref><ref>{{cite web |date=2007-01-11 |title=Most Polonium Made Near the Volga River |url=https://www.themoscowtimes.com/archive/most-polonium-made-near-the-volga-river |publisher=The Moscow Times – News}}</ref>

This process can cause problems in [[Chemistry:Lead-bismuth eutectic|lead-bismuth]] based [[Physics:Liquid metal cooled reactor|liquid metal cooled nuclear reactors]] such as those used in the Soviet Navy's K-27. Measures must be taken in these reactors to deal with the unwanted possibility of <sup>210</sup>Po being released from the coolant.<ref>{{cite journal|title=Long-lived radionuclides of sodium, lead-bismuth, and lead coolants in fast-neutron reactors|journal=Atomic Energy|volume =87|issue=3 |year=1999|pages=658–662|doi=10.1007/BF02673579|last1=Usanov|first1=V. I.|last2=Pankratov|first2=D. V.|last3=Popov|first3=É. P.|last4=Markelov|first4=P. I.|last5=Ryabaya|first5=L. D.|last6=Zabrodskaya|first6=S. V.|s2cid=94738113}}</ref><ref>{{cite journal|author=Naumov, V. V. |date=November 2006|url=http://www.antiatom.ru/2006_12-11.php|script-title=ru:За какими корабельными реакторами будущее?|language=ru|journal= Атомная стратегия |volume= 26}}</ref>

The longer-lived isotopes of polonium, <sup>208</sup>Po and <sup>209</sup>Po, can be formed by [[Physics:Proton|proton]] or [[Physics:Deuteron|deuteron]] bombardment of bismuth using a [[Physics:Cyclotron|cyclotron]]. Other more neutron-deficient and more unstable isotopes can be formed by the irradiation of platinum with [[Chemistry:Carbon|carbon]] nuclei.<ref>{{cite journal| author = Atterling, H.| author2 = Forsling, W. |title = Light Polonium Isotopes from Carbon Ion Bombardments of Platinum |journal = Arkiv för Fysik |volume = 15| issue = 1 |pages = 81–88 |date = 1959 |osti =4238755}}</ref>

==Applications==
Polonium-based sources of alpha particles were produced in the former [[Place:Soviet Union|Soviet Union]].<ref name="rus1" /> Such sources were applied for measuring the thickness of industrial coatings via attenuation of alpha radiation.<ref>Bagnall, p. 225</ref>

Because of intense alpha radiation, a one-gram sample of <sup>210</sup>Po will spontaneously heat up to above {{convert|500|C|F}} generating about 140 watts of power. Therefore, <sup>210</sup>Po is used as an atomic heat source to power [[Physics:Radioisotope thermoelectric generator|radioisotope thermoelectric generator]]s via thermoelectric materials.<ref name="anl">{{cite web| url =http://www.ead.anl.gov/pub/doc/polonium.pdf | archive-url =https://web.archive.org/web/20070703021010/http://www.ead.anl.gov/pub/doc/polonium.pdf | archive-date =2007-07-03 |title = Polonium |publisher = Argonne National Laboratory| access-date = 2009-05-05}}</ref><ref name="nbb" /><ref name="g251">Greenwood, p. 251</ref><ref>{{cite book |url=https://books.google.com/books?id=07TEK_w3A4AC&pg=PA183 |page=183 |last=Hanslmeier |first= Arnold |title= The sun and space weather |publisher=Springer |date=2002 |isbn=978-1-4020-0684-5}}</ref> For example, <sup>210</sup>Po heat sources were used in the Lunokhod 1 (1970) and Lunokhod 2 (1973) [[Astronomy:Moon|Moon]] rovers to keep their internal components warm during the lunar nights, as well as the [[Engineering:List of Kosmos satellites (1–250)|Kosmos 84]] and 90 satellites (1965).<ref name="rus1">{{cite web |url=http://npc.sarov.ru/issues/sarovbook/section3p11.html |archive-url=https://web.archive.org/web/20070501055529/http://npc.sarov.ru/issues/sarovbook/section3p11.html |archive-date=May 1, 2007 |title=Радиоизотопные источники тепла |url-status=dead |access-date=June 1, 2016}} (in Russian). npc.sarov.ru</ref><ref>{{cite book | first = Andrew | last = Wilson | title = Solar System Log | location = London | publisher = Jane's Publishing Company Ltd | date = 1987 | page = [https://archive.org/details/solarsystemlog00andr/page/64 64] | isbn = 978-0-7106-0444-6 | url = https://archive.org/details/solarsystemlog00andr/page/64 }}</ref>

The alpha particles emitted by polonium can be converted to neutrons using beryllium oxide, at a rate of 93 neutrons per million alpha particles.<ref name="g251" /> Po-BeO mixtures are used as passive [[Physics:Neutron source|neutron source]]s with a gamma-ray-to-[[Physics:Neutron|neutron]] production ratio of 1.13 ± 0.05, lower than for [[Physics:Nuclear fission|nuclear fission]]-based neutron sources.<ref name="gtn">{{cite arXiv |last=Ritter |first=Sebastian |eprint=2111.02774 |title=Comparative Study of Gamma to Neutron Ratios of various (alpha, neutron) Neutron Sources |class=nucl-ex |date= 2021}}</ref> Examples of Po-BeO mixtures or [[Chemistry:Alloy|alloy]]s used as neutron sources are a neutron trigger or initiator for [[Engineering:Nuclear weapon|nuclear weapon]]s<ref name="nbb">{{cite book| last = Emsley| first =John |title = Nature's Building Blocks| publisher = Oxford University Press| location = New York| date = 2001| pages = 330–332| isbn = 978-0-19-850341-5}}</ref><ref>{{cite book| author = Rhodes, Richard| title = Dark Sun: The Making of the Hydrogen Bomb| publisher = Walker & Company| location = New York| date = 2002| pages = [https://archive.org/details/darksunmakingofh00rhod/page/187 187–188]| isbn = 978-0-684-80400-2| url = https://archive.org/details/darksunmakingofh00rhod/page/187}}</ref> and for inspections of oil wells. About 1500 sources of this type, with an individual activity of {{convert|1850|Ci|TBq|abbr=on}}, had been used annually in the Soviet Union.<ref>[http://www.stringer.ru/publication.mhtml?Part=50&PubID=6767 Красивая версия "самоубийства" Литвиненко вследствие криворукости] (in Russian). stringer.ru (2006-11-26).</ref>

Polonium was also part of brushes or more complex tools that eliminate static charges in photographic plates, textile mills, paper rolls, sheet plastics, and on substrates (such as automotive) prior to the application of coatings.<ref name="BoiceCohen2014">{{cite journal |last1=Boice |first1=John D. |last2=Cohen |first2=Sarah S. |last3=Mumma |first3=Michael T. |last4=Ellis |first4=Elizabeth Dupree |last5=Cragle |first5=Donna L. |last6=Eckerman |first6=Keith F. |last7=Wallace |first7=Philip W. |last8=Chadda |first8=Bandana |last9=Sonderman |first9=Jennifer S. |last10=Wiggs |first10=Laurie D. |last11=Richter |first11=Bonnie S. |last12=Leggett |first12=Richard W. |title=Mortality Among Mound Workers Exposed to Polonium-210 and Other Sources of Radiation, 1944–1979 |journal=Radiation Research |volume=181 |issue=2 |date=2014 |pages=208–28 |doi=10.1667/RR13395.1 |pmid=24527690 |display-authors=2|bibcode=2014RadR..181..208B |osti=1286690 |s2cid=7350371 }}</ref> Alpha particles emitted by polonium ionize air molecules that neutralize charges on the nearby surfaces.<ref>{{cite web|url=http://www.thermo.com/eThermo/CMA/PDFs/Articles/articlesFile_16929.pdf |title=Static Control for Electronic Balance Systems |access-date=2009-05-05 |url-status=dead |archive-url=https://web.archive.org/web/20131110213624/http://www.thermo.com/eThermo/CMA/PDFs/Articles/articlesFile_16929.pdf |archive-date=November 10, 2013 }}</ref><ref>{{cite news| url =http://news.bbc.co.uk/1/hi/england/1868414.stm |title =BBC News : College breaches radioactive regulations| access-date = 2009-05-05|date=2002-03-12}}</ref> Some anti-static brushes contain up to {{convert|500|uCi|MBq|sigfig=1}} of <sup>210</sup>Po as a source of charged particles for neutralizing static electricity.<ref>{{cite web |url = http://www.amstat.com/solutions/staticmaster.html |title = Staticmaster Ionizing Brushes |publisher = AMSTAT Industries |access-date = 2009-05-05 |archive-date = 2009-09-26 |archive-url = https://web.archive.org/web/20090926032436/http://www.amstat.com/solutions/staticmaster.html |url-status = dead }}</ref> In the US, devices with no more than {{convert|500|µCi|MBq|abbr=on}} of (sealed) <sup>210</sup>Po per unit can be bought in any amount under a "general license",<ref>{{cite web| url = https://www.nrc.gov/reading-rm/doc-collections/cfr/part031/full-text.html| title = General domestic licenses for byproduct material| access-date = 2009-05-05}}</ref> which means that a buyer need not be registered by any authorities. Polonium needs to be replaced in these devices nearly every year because of its short half-life; it is also highly radioactive and therefore has been mostly replaced by less dangerous [[Physics:Beta decay|beta particle]] sources.<ref name="anl" />

Tiny amounts of <sup>210</sup>Po are sometimes used in the laboratory and for teaching purposes—typically of the order of {{convert|4|-|40|kBq|µCi|abbr=on}}, in the form of sealed sources, with the polonium deposited on a substrate or in a resin or polymer matrix—are often exempt from licensing by the NRC and similar authorities as they are not considered hazardous. Small amounts of <sup>210</sup>Po are manufactured for sale to the public in the United States as "needle sources" for laboratory experimentation, and they are retailed by scientific supply companies. The polonium is a layer of plating which in turn is plated with a material such as gold, which allows the alpha radiation (used in experiments such as cloud chambers) to pass while preventing the polonium from being released and presenting a toxic hazard.{{citation needed|date=February 2023}}

Polonium [[Physics:Spark plug|spark plug]]s were marketed by Firestone from 1940 to 1953. While the amount of radiation from the plugs was minuscule and not a threat to the consumer, the benefits of such plugs quickly diminished after approximately a month because of polonium's short half-life and because buildup on the conductors would block the radiation that improved engine performance. (The premise behind the polonium spark plug, as well as Alfred Matthew Hubbard's prototype [[Chemistry:Radium|radium]] plug that preceded it, was that the radiation would improve ionization of the fuel in the cylinder and thus allow the motor to fire more quickly and efficiently.)<ref>{{cite web|url=https://www.orau.org/health-physics-museum/collection/consumer/miscellaneous/spark-plugs.html|title=Radioactive spark plugs|publisher=Oak Ridge Associated Universities|date=January 20, 1999|access-date=October 7, 2021}}</ref><ref>{{cite web|url=http://www.utoledo.edu/nsm/ic/elements/polonium.html|first=Cassandra|last=Pittman|title=Polonium|work=The Instrumentation Center|publisher=University of Toledo|date=February 3, 2017|access-date=August 23, 2018}}</ref>

==Biology and toxicity==

===Overview===
Polonium can be hazardous and has no biological role.<ref name="nbb" /> By mass, polonium-210 is around 250,000 times more toxic than [[Chemistry:Hydrogen cyanide|hydrogen cyanide]] (the {{LD50}} for <sup>210</sup>Po is less than 1 [[Microgram|microgram]] for an average adult (see below) compared with about 250 milligrams for hydrogen cyanide<ref>{{cite web| url = http://physchem.ox.ac.uk/MSDS/HY/hydrogen_cyanide.html | archive-url = https://archive.today/20020211054154/http://physchem.ox.ac.uk/MSDS/HY/hydrogen_cyanide.html | url-status = dead | archive-date = 2002-02-11 |title =Safety data for hydrogen cyanide|work= Physical & Theoretical Chemistry Lab, Oxford University}}</ref>). The main hazard is its intense radioactivity (as an alpha emitter), which makes it difficult to handle safely. Even in [[Microgram|microgram]] amounts, handling <sup>210</sup>Po is extremely dangerous, requiring specialized equipment (a negative pressure alpha glove box equipped with high-performance filters), adequate monitoring, and strict handling procedures to avoid any contamination. Alpha particles emitted by polonium will damage organic tissue easily if polonium is ingested, inhaled, or absorbed, although they do not penetrate the epidermis and hence are not hazardous as long as the alpha particles remain outside the body. Wearing chemically resistant and intact gloves is a mandatory precaution to avoid transcutaneous [[Physics:Diffusion|diffusion]] of polonium directly through the [[Biology:Skin|skin]]. Polonium delivered in concentrated [[Chemistry:Nitric acid|nitric acid]] can easily diffuse through inadequate gloves (e.g., latex gloves) or the acid may damage the gloves.<ref>Bagnall, pp. 202–6</ref>

Polonium does not have toxic chemical properties.<ref>{{Cite web|url=https://www.medicalnewstoday.com/articles/58088.php|title=Polonium-210: Effects, symptoms, and diagnosis|website=Medical News Today|date=28 July 2017}}</ref>

It has been reported that some microbes can [[Biology:Methylation|methylate]] polonium by the action of [[Chemistry:Methylcobalamin|methylcobalamin]].<ref>{{cite journal |last1= Momoshima | first1 =N.|last2= Song | first2 = L. X.|last3= Osaki | first3 =S.|last4=Maeda | first4 =Y.| title = Formation and emission of volatile polonium compound by microbial activity and polonium methylation with methylcobalamin | journal =Environ Sci Technol | date =2001 | volume =35 | issue = 15 | pages = 2956–2960 | doi = 10.1021/es001730| pmid =11478248| bibcode =2001EnST...35.2956M}}</ref><ref>
{{cite journal|last1= Momoshima | first1 =N.|last2= Song | first2 = L. X.|last3= Osaki | first3 =S.|last4=Maeda | first4 =Y.| title = Biologically induced Po emission from fresh water | journal =J Environ Radioact| date = 2002 | volume = 63| issue = 2| pages= 187–197 | doi =10.1016/S0265-931X(02)00028-0| pmid =12363270}}</ref> This is similar to the way in which [[Chemistry:Mercury (element)|mercury]], [[Chemistry:Selenium|selenium]], and [[Chemistry:Tellurium|tellurium]] are methylated in living things to create organometallic compounds. Studies investigating the metabolism of polonium-210 in rats have shown that only 0.002 to 0.009% of polonium-210 ingested is excreted as volatile polonium-210.<ref>{{cite journal |display-authors=4 |last1=Li |first1=Chunsheng |last2=Sadi |first2=Baki |last3=Wyatt |first3=Heather |last4=Bugden |first4=Michelle |last5=Priest |first5=Nicholas |last6=Wilkinson |first6=Diana |last7=Kramer |first7=Gary H. |date=2010 |title=Metabolism of <sup>210</sup>Po in rats: volatile <sup>210</sup>Po in excreta |journal=Radiation Protection Dosimetry |volume=140 |issue=2 |pages=158–162 |doi=10.1093/rpd/ncq047 |pmid=20159915}}</ref>

===Acute effects===
The [[Chemistry:Median lethal dose|median lethal dose]] (LD<sub>50</sub>) for acute radiation exposure is about 4.5&nbsp;[[Physics:Sievert|Sv]].<ref name="pnl">{{cite web| url = http://www.pnl.gov/main/publications/external/technical_reports/PNNL-14424.pdf |title =Health Impacts from Acute Radiation Exposure| access-date = 2009-05-05|work=Pacific Northwest National Laboratory}}</ref> The [[Physics:Committed effective dose equivalent (CEDE)|committed effective dose equivalent]] <sup>210</sup>Po is 0.51&nbsp;µSv/[[Becquerel|Bq]] if ingested, and 2.5&nbsp;µSv/Bq if inhaled.<ref name="nsds">{{cite web| url = http://hpschapters.org/northcarolina/NSDS/210PoPDF.pdf |title =Nuclide Safety Data Sheet: Polonium–210| access-date = 2009-05-05|work=hpschapters.org}}</ref> A fatal 4.5&nbsp;Sv dose can be caused by ingesting {{convert|8.8|MBq|µCi|abbr=on}}, about 50&nbsp;nanograms (ng), or inhaling {{convert|1.8|MBq|µCi|abbr=on}}, about 10&nbsp;ng. One gram of <sup>210</sup>Po could thus in theory poison 20&nbsp;million&nbsp;people, of whom 10&nbsp;million would die. The actual toxicity of <sup>210</sup>Po is lower than these estimates because radiation exposure that is spread out over several weeks (the [[Biology:Biological half-life|biological half-life]] of polonium in humans is 30&nbsp;to 50&nbsp;days<ref>{{cite journal| osti =7162390 |title =Effective half-life of polonium in the human|author=Naimark, D.H.|date=1949-01-04|journal=Technical Report MLM-272/XAB, Mound Lab., Miamisburg, OH}}</ref>) is somewhat less damaging than an instantaneous dose. It has been estimated that a [[Chemistry:Median lethal dose|median lethal dose]] of <sup>210</sup>Po is {{convert|15|MBq|mCi}}, or 0.089&nbsp;micrograms (μg), still an extremely small amount.<ref name="nuclearweaponsarchive">{{cite web| url =http://nuclearweaponarchive.org/News/PoloniumPoison.html |title =Polonium Poisoning|author=Carey Sublette|date=2006-12-14| access-date = 2009-05-05}}</ref><ref>{{cite journal| display-authors = 4| last1 = Harrison |first1=J. |title =Polonium-210 as a poison| date = 2007 |journal = J. Radiol. Prot.| pmid = 17341802 |volume = 27| issue = 1 | doi = 10.1088/0952-4746/27/1/001| quote = The conclusion is reached that 0.1–0.3&nbsp;GBq or more absorbed to blood of an adult male is likely to be fatal within 1 month. This corresponds to ingestion of 1–3&nbsp;GBq or more, assuming 10% absorption to blood |bibcode = 2007JRP....27...17H| pages = 17–40| last2 = Leggett| first2 = Rich| last3 = Lloyd| first3 = David| last4 = Phipps| first4 = Alan| last5 = Scott| first5 = Bobby| s2cid = 27764788 }}</ref> For comparison, one grain of [[Chemistry:Salt|table salt]] is about 0.06&nbsp;mg = 60&nbsp;μg.<ref>{{cite web|url=http://www.physlink.com/Education/AskExperts/ae342.cfm|title=Approximately how many atoms are in a grain of salt?|author=Yasar Safkan|website=PhysLink.com: Physics & Astronomy}}</ref>

===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.<ref name="pnl" /> The general population is exposed to small amounts of polonium as a [[Chemistry:Radon|radon]] daughter in indoor air; the isotopes <sup>214</sup>Po and <sup>218</sup>Po are thought to cause the majority<ref>{{cite book| title = Health Risks of Radon and Other Internally Deposited Alpha-Emitters: BEIR IV|isbn=978-0-309-03789-1|page =5|publisher=National Academy Press|date=1988}}</ref> of the estimated 15,000–22,000 lung cancer deaths in the US every year that have been attributed to indoor radon.<ref>{{cite book| url =http://newton.nap.edu/html/beir6/ | archive-url =https://web.archive.org/web/20060919054314/http://newton.nap.edu/html/beir6/ | archive-date =2006-09-19 |title = Health Effects of Exposure to Indoor Radon| publisher=National Academy Press|place=Washington|date=1999}}</ref> Tobacco smoking causes additional exposure to polonium.<ref>{{cite web| url =https://www.straightdope.com/21343841/does-smoking-organically-grown-tobacco-lower-the-chance-of-lung-cancer |title =The Straight Dope: Does smoking organically grown tobacco lower the chance of lung cancer?| access-date = 2020-10-11|date =2007-09-28}}</ref>

===Regulatory exposure limits and handling===
The maximum allowable body burden for ingested <sup>210</sup>Po is only {{convert|1.1|kBq|nCi|abbr=on}}, which is equivalent to a particle massing only 6.8 picograms. The maximum permissible workplace concentration of airborne <sup>210</sup>Po is about 10&nbsp;Bq/m<sup>3</sup> ({{val|3|e=-10}}&nbsp;µCi/cm<sup>3</sup>).<ref>{{cite web |url = https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/appb/Polonium-210.html |title = Nuclear Regulatory Commission limits for <sup>210</sup>Po| date = 2008-12-12 |access-date = 2009-01-12 |publisher = U.S. NRC}}</ref> The target organs for polonium in humans are the [[Biology:Spleen|spleen]] and [[Biology:Liver|liver]].<ref>{{cite web | url =http://www.pilgrimwatch.org/health1.html | title =PilgrimWatch – Pilgrim Nuclear – Health Impact | access-date =2009-05-05 | archive-url =https://web.archive.org/web/20090105192000/http://www.pilgrimwatch.org/health1.html | archive-date =2009-01-05 | url-status =dead }}</ref> As the spleen (150&nbsp;g) and the liver (1.3 to 3&nbsp;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 [[Chemistry:Caesium|caesium]] or [[Physics:Tritium|tritium]] (as T<sub>2</sub>O).{{citation needed|date=February 2023}}

<sup>210</sup>Po is widely used in industry, and readily available with little regulation or restriction.{{citation needed|date=January 2015}}<ref>{{Cite journal|last1=Bastian|first1=R.K.|last2=Bachmaier|first2=J.T.|last3=Schmidt|first3=D.W.|last4=Salomon|first4=S.N.|last5=Jones|first5=A.|last6=Chiu|first6=W.A.|last7=Setlow|first7=L.W.|last8=Wolbarst|first8=A.W.|last9=Yu|first9=C.|date=2004-01-01|title=Radioactive Materials in Biosolids: National Survey, Dose Modeling & POTW Guidance|journal=Proceedings of the Water Environment Federation|volume=2004|issue=1|pages=777–803|doi=10.2175/193864704784343063}}</ref> In the US, a tracking system run by the Nuclear Regulatory Commission was implemented in 2007 to register purchases of more than {{convert|16|Ci}} of polonium-210 (enough to make up 5,000 lethal doses). The IAEA "is said to be considering tighter regulations&nbsp;... There is talk that it might tighten the polonium reporting requirement by a factor of 10, to {{convert|1.6|Ci}}."<ref name="Zimmerman">{{cite news |url=https://www.nytimes.com/2006/12/19/opinion/19zimmerman.html |title=The Smoky Bomb Threat |access-date=2006-12-19 |newspaper=The New York Times |first=Peter D. |last=Zimmerman|date=2006-12-19}}</ref> As of 2013, this is still the only alpha emitting byproduct material available, as a NRC Exempt Quantity, which may be held without a radioactive material license.{{citation needed|date=September 2013}}

Polonium and its compounds must be handled with caution inside special alpha glove boxes, equipped with [[Physics:HEPA|HEPA]] filters and continuously maintained under depression to prevent the radioactive materials from leaking out. Gloves made of [[Chemistry:Natural rubber|natural rubber]] ([[Chemistry:Latex|latex]]) do not properly withstand chemical attacks, a.o. by concentrated [[Chemistry:Nitric acid|nitric acid]] {{nowrap|(e.g., 6 M {{chem2|HNO3}})}} commonly used to keep polonium in [[Chemistry:Solution|solution]] while minimizing its [[Physics:Sorption|sorption]] onto glass. They do not provide sufficient protection against the contamination from polonium ([[Physics:Diffusion|diffusion]] of <sup>210</sup>Po solution through the intact latex membrane, or worse, direct contact through tiny holes and cracks produced when the latex begins to suffer degradation by acids or UV from ambient light); additional surgical gloves are necessary (inside the glovebox to protect the main gloves when handling strong acids and bases, and also from outside to protect the operator hands against <sup>210</sup>Po contamination from diffusion, or direct contact through glove defects). Chemically more resistant, and also denser, [[Chemistry:Neoprene|neoprene]] and butyl gloves shield alpha particles emitted by polonium better than natural rubber.<ref>Bagnall, p. 204.</ref> The use of natural rubber gloves is not recommended for handling <sup>210</sup>Po solutions.

===Cases of poisoning===
Despite the element's highly hazardous properties, circumstances in which polonium poisoning can occur are rare. Its extreme scarcity in nature, the short half-lives of all its isotopes, the specialised facilities and equipment needed to obtain any significant quantity, and safety precautions against laboratory accidents all make harmful exposure events unlikely. As such, only a handful of cases of radiation poisoning specifically attributable to polonium exposure have been confirmed.{{citation needed|date=February 2023}}

====20th century====
In response to concerns about the risks of occupational polonium exposure, quantities of <sup>210</sup>Po were administered to five human volunteers at the University of Rochester from 1944 to 1947, in order to study its biological behaviour. These studies were funded by the [[Physics:Manhattan Project|Manhattan Project]] and the AEC. Four men and a woman participated, all suffering from terminal cancers, and ranged in age from their early thirties to early forties; all were chosen because experimenters wanted subjects who had not been exposed to polonium either through work or accident.<ref name="Rochester">{{cite journal |last1=Moss |first1=William |last2=Eckhardt |first2=Roger |date=1995 |title=The human plutonium injection experiments |url=https://fas.org/sgp/othergov/doe/lanl/pubs/00326640.pdf |journal=Los Alamos Science |volume=23 |pages=177–233}}</ref> <sup>210</sup>Po was injected into four hospitalised patients, and orally given to a fifth. None of the administered doses (all ranging from 0.17 to 0.30 μ[[Physics:Curie (unit)|Ci]] kg<sup>−1</sup>) approached fatal quantities.<ref>{{cite book |last=Fink |first=Robert |date=1950 |title=Biological studies with polonium, radium, and plutonium |publisher=McGraw-Hill |series=National Nuclear Energy Series |volume=VI-3 |isbn=5-86656-114-X |language=ru}}</ref><ref name="Rochester" />

The first documented death directly resulting from polonium poisoning occurred in the [[Place:Soviet Union|Soviet Union]], on 10 July 1954.<ref name="Gasteva">{{cite book |last=Gasteva |first=G. N. |date=2001 |editor-last=Ilʹin |editor-first=L. A. |title=Radiacionnaja medicina: rukovodstvo dlja vračej-issledovatelej i organizatorov zdravooxranenija, Tom 2 (Radiacionnye poraženija čeloveka) |trans-title=Radiation medicine: a guide for medical researchers and healthcare managers, Volume 2 (Radiation damage to humans) |publisher=IzdAT |pages=99–107 |chapter=Ostraja lučevaja boleznʹ ot postuplenija v organizm polonija |trans-chapter=Acute radiation sickness by ingestion of polonium into the body |isbn=5-86656-114-X |language=ru}}</ref><ref>{{cite journal |last1=Harrison |first1=John |last2=Leggett |first2=Rich |last3=Lloyd |first3=David |last4=Phipps |first4=Alan |last5=Scott |first5=Bobby |date=2 March 2007 |title=Polonium-210 as a poison |journal=Journal of Radiological Protection |volume=27 |issue=1 |pages=17–40 |doi=10.1088/0952-4746/27/1/001|pmid=17341802 |bibcode=2007JRP....27...17H |s2cid=27764788 }}</ref> An unidentified 41-year-old man presented for medical treatment on 29 June, with severe vomiting and fever; the previous day, he had been working for five hours in an area in which, unknown to him, a capsule containing <sup>210</sup>Po had depressurised and begun to disperse in aerosol form. Over this period, his total intake of airborne <sup>210</sup>Po was estimated at 0.11 GBq (almost 25 times the estimated LD<sub>50</sub> by inhalation of 4.5 MBq). Despite treatment, his condition continued to worsen and he died 13 days after the exposure event.<ref name="Gasteva" />

It has also been suggested that [[Biography:Irène Joliot-Curie|Irène Joliot-Curie]]'s 1956 death from leukaemia was owed to the radiation effects of polonium. She was accidentally exposed in 1946 when a sealed capsule of the element exploded on her laboratory bench.<ref>{{cite news|url=http://www.news.com.au/dailytelegraph/story/0,22049,20863878-5001031,00.html |title=Innocent chemical a killer |publisher=The Daily Telegraph (Australia) |date=2006-12-04 |access-date=2009-05-05 |first=Jeremy |last=Manier |url-status=dead |archive-url=https://web.archive.org/web/20090106013604/http://www.news.com.au/dailytelegraph/story/0,22049,20863878-5001031,00.html |archive-date=January 6, 2009 }}</ref>

As well, several deaths in Israel during 1957–1969 have been alleged to have resulted from <sup>210</sup>Po exposure.<ref>{{cite book|last = Karpin|first = Michael|title = The bomb in the basement: How Israel went nuclear and what that means for the world|publisher = Simon and Schuster|date = 2006|isbn = 978-0-7432-6594-2|url = https://archive.org/details/bombinbasementho00karp}}</ref> A leak was discovered at a Weizmann Institute laboratory in 1957. Traces of <sup>210</sup>Po were found on the hands of Professor Dror Sadeh, a physicist who researched radioactive materials. Medical tests indicated no harm, but the tests did not include bone marrow. Sadeh, one of his students, and two colleagues died from various [[Medicine:Cancer|cancer]]s over the subsequent few years. The issue was investigated secretly, but there was never any formal admission of a connection between the leak and the deaths.<ref name='LA Times 2007-01-01'>{{cite news |first=Thomas |last=Maugh |author2=Karen Kaplan |title=A restless killer radiates intrigue |date=2007-01-01|url =http://articles.latimes.com/2007/jan/01/science/sci-polonium1 |work =Los Angeles Times |access-date = 2008-09-17}}</ref>

The Church Rock uranium mill spill is reported to have released [[Physics:Polonium-210|polonium-210]]. The report states animals had higher concentrations of lead-210, polonium-210 and radium-226 than the tissues from control animals.<ref name="Millard1983">{{cite web | author= Jere Millard, Bruce Gallaher, David Baggett, Steven Gary | date=September 1983 | title=The Church Rock uranium mill tailings spill a health and environmental assessment, page 32 | url=https://semspub.epa.gov/work/06/1000720.pdf | access-date=2024-01-30}}</ref>

====21st century====
The cause of the 2006 death of Alexander Litvinenko, a former Russian FSB agent who had defected to the United Kingdom in 2001, was identified to be poisoning with a lethal dose of <sup>210</sup>Po;<ref>{{cite news |title=The mystery of Litvinenko's death |url=http://news.bbc.co.uk/1/hi/uk/6180432.stm |date=2006-11-24 |work=BBC News |first=Tom |last=Geoghegan}}</ref><ref name="bbc">{{cite news| url =http://news.bbc.co.uk/1/hi/uk/6698545.stm |title = UK requests Lugovoi extradition| access-date = 2009-05-05|work=BBC News|date=2007-05-28}}</ref> it was subsequently determined that the <sup>210</sup>Po had probably been deliberately administered to him by two Russian ex-security agents, Andrey Lugovoy and Dmitry Kovtun.<ref>{{cite web|url=https://www.litvinenkoinquiry.org/report|publisher=The Litvinenko Inquiry|title=Report|access-date=21 January 2016}}</ref><ref>{{cite news|last1=Addley|first1=Esther|last2=Harding|first2=Luke|title=Litvinenko 'probably murdered on personal orders of Putin'|url=https://www.theguardian.com/world/2016/jan/21/alexander-litvinenko-was-probably-murdered-on-personal-orders-of-putin|access-date=21 January 2016|work=The Guardian|date=21 January 2016}}</ref> As such, Litvinenko's death was the first (and, to date, only) confirmed instance in which polonium's extreme toxicity has been used with malicious intent.<ref>{{cite news |first=Steve |last=Boggan |title=Who else was poisoned by polonium? |work={{wipe|The Guardian}} |date=5 June 2007 |url=https://www.theguardian.com/world/2007/jun/05/russia.science |access-date=28 August 2021}}</ref><ref name="PoAlJazeera">{{cite news |first=David |last=Poort |title=Polonium: a silent killer |work=Al Jazeera News |date=6 November 2013 |url=https://www.aljazeera.com/news/2013/11/6/polonium-a-silent-killer |access-date=28 August 2021}}</ref><ref>{{cite journal |last1=Froidevaux |first1=Pascal |last2=Bochud |first2=François |last3=Baechler |first3=Sébastien |last4=Castella |first4=Vincent |last5=Augsburger |first5=Marc |last6=Bailat |first6=Claude |last7=Michaud |first7=Katarzyna |last8=Straub |first8=Marietta |last9=Pecchia |first9=Marco |last10=Jenk |first10=Theo M. |last11=Uldin |first11=Tanya |last12=Mangin |first12=Patrice |date=February 2016 |title=²¹⁰Po poisoning as possible cause of death: forensic investigations and toxicological analysis of the remains of Yasser Arafat |journal=Forensic Science International |volume=259 |pages=1–9 |doi=10.1016/j.forsciint.2015.09.019 |pmid=26707208 |s2cid=207751390 |doi-access=free }}</ref>

In 2011, an allegation surfaced that the death of [[Place:State of Palestine|Palestinian]] leader [[Biography:Yasser Arafat|Yasser Arafat]], who died on 11 November 2004 of uncertain causes, also resulted from deliberate polonium poisoning,<ref>{{cite news|date=17 January 2011|title=الأخبار – ضابط فلسطيني: خصوم عرفات قتلوه عربي|publisher=Al Jazeera|url=http://www.aljazeera.net/news/pages/676ce5b7-f085-45d4-9c97-5c7a32864c06|url-status=dead|access-date=2021-06-05|archive-url=https://web.archive.org/web/20120704225411/http://www.aljazeera.net/news/pages/676ce5b7-f085-45d4-9c97-5c7a32864c06|archive-date=2012-07-04}}</ref><ref>{{cite episode |title=George Galloway and Alex Goldfarb on Litvinenko inquiry |url=https://www.youtube.com/watch?v=H0om8ii5XVs&t=113 | archive-url=https://ghostarchive.org/varchive/youtube/20211030/H0om8ii5XVs| archive-date=2021-10-30|series=Newsnight |network=BBC |date=21 January 2016 |time=1:53 |access-date=28 March 2018}}{{cbignore}}</ref> and in July 2012, concentrations of <sup>210</sup>Po many times more than normal were detected in Arafat's clothes and personal belongings by the Institut de Radiophysique in Lausanne, Switzerland.<ref>{{Cite journal | last1 = Froidevaux | first1 = P. | last2 = Baechler | first2 = S. B. | last3 = Bailat | first3 = C. J. | last4 = Castella | first4 = V. | last5 = Augsburger | first5 = M. | last6 = Michaud | first6 = K. | last7 = Mangin | first7 = P. | last8 = Bochud | first8 = F. O. O. | doi = 10.1016/S0140-6736(13)61834-6 | title = Improving forensic investigation for polonium poisoning | journal = The Lancet | volume = 382 | issue = 9900 | pages = 1308 | year = 2013 | pmid = 24120205| s2cid = 32134286}}</ref><ref name="BartReuters">Bart, Katharina (2012-07-03). [https://www.reuters.com/article/us-palestinians-arafat-idUSBRE8621CL20120703 Swiss institute finds polonium in Arafat's effects] {{Webarchive|url=https://web.archive.org/web/20151007125548/http://www.reuters.com/article/2012/07/03/us-palestinians-arafat-idUSBRE8621CL20120703 |date=2015-10-07 }}. Reuters.</ref> Even though Arafat's symptoms were acute gastroenteritis with diarrhoea and vomiting,<ref>{{cite news |last1=Paul Taylor |title=Palestinian leader Yasser Arafat was murdered with polonium: widow |url=https://www.nbcnews.com/news/world/palestinian-leader-yasser-arafat-was-murdered-polonium-widow-flna8C11542188 |work=NBC News |agency=Reuters |date=Nov 7, 2013}}</ref> the institute's spokesman said that despite the tests the symptoms described in Arafat's medical reports were not consistent with <sup>210</sup>Po poisoning, and conclusions could not be drawn.<ref name="BartReuters" /> In 2013 the team found levels of polonium in Arafat's ribs and pelvis 18 to 36 times the average,<ref name=AJ_Swiss_study>{{Cite web|last2=Silverstein|first1=David | last1=Poort| first2=Ken |title=Swiss study: Polonium found in Arafat's bones|url=https://www.aljazeera.com/news/2013/11/7/swiss-study-polonium-found-in-arafats-bones|access-date=12 February 2023 |publisher=www.aljazeera.com| date = 6 November 2013 |language=en}}</ref><ref name=Reuters_Arafat_poisoned>{{Cite news|title=Swiss Team: Arafat Poisoned to Death With Polonium |language=en|work=Haaretz|url=https://www.haaretz.com/2013-11-06/ty-article/swiss-team-arafat-poisoned-with-polonium/0000017f-e386-d7b2-a77f-e3876db50000 | date= 6 November 2013 |access-date=12 February 2023}}</ref> even though by this point in time the amount had diminished by a factor of 2 million.<ref name=LT24.05.14>{{in lang|fr}} Luis Lema, [https://www.letemps.ch/monde/yasser-arafat-valse-isotopes "Yasser Arafat, la valse des isotopes"], ''Le Temps'', Saturday 24 May 2014, p. 3.</ref> Forensic scientist Dave Barclay stated, "In my opinion, it is absolutely certain that the cause of his illness was polonium poisoning. ... What we have got is the smoking gun - the thing that caused his illness and was given to him with malice."<ref>{{cite news |last1=Paul Taylor |title=Palestinian leader Yasser Arafat was murdered with polonium: widow |url=https://www.nbcnews.com/news/world/palestinian-leader-yasser-arafat-was-murdered-polonium-widow-flna8C11542188 |work=NBC News |agency=Reuters |date=Nov 7, 2013}}</ref><ref name=AJ_Swiss_study/> Subsequently French and Russian teams claimed that the elevated <sup>210</sup>Po levels were not the result of deliberate poisoning, and did not cause Arafat's death.<ref name="autogenerated1">Isachenkov, Vadim (2013-12-27) [https://web.archive.org/web/20131230234655/http://www.wtop.com/220/3531404/Russia-Arafats-death-not-caused-by-radiation Russia: Arafat's death not caused by radiation]. Associated Press.</ref><ref>{{cite news|date=3 December 2013|title=Arafat did not die of poisoning, French tests conclude|publisher={{wipe|Reuters}}|url=https://www.reuters.com/article/us-palestinians-arafat-idUKBRE9B20DI20131203|access-date=1 September 2021}}</ref>

It has also been suspected that Russian businessman Roman Tsepov was killed with polonium. He had symptoms similar to Aleksander Litvinenko.<ref name=timesonline>{{Cite news|url=https://www.thetimes.co.uk/article/the-putin-bodyguard-riddle-687f9vcdmzf|title=The Putin bodyguard riddle|date=3 December 2006|newspaper=The Sunday Times}}</ref>

===Treatment===
It has been suggested that [[Unsolved:Chelation therapy|chelation agents]], such as British anti-Lewisite ([[Chemistry:Dimercaprol|dimercaprol]]), can be used to decontaminate humans.<ref>{{cite web| url = https://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/ucm071944.pdf |title = Guidance for Industry. Internal Radioactive Contamination — Development of Decorporation Agents| access-date = 2009-07-07|work=US Food and Drug Administration}}</ref> In one experiment, rats were given a fatal dose of 1.45&nbsp;MBq/kg (8.7&nbsp;ng/kg) of <sup>210</sup>Po;
all untreated rats were dead after 44 days, but 90% of the rats treated with the chelation agent
HOEtTTC remained alive for five months.<ref>{{cite journal
|display-authors = 4
|author = Rencováa J.
|author2 = Svoboda V.
|author3 = Holuša R.
|author4 = Volf V.
|author5 = Jones M. M.
|author6 = Singh P. K.
|title = Reduction of subacute lethal radiotoxicity of polonium-210 in rats by chelating agents
|journal = International Journal of Radiation Biology
|volume = 72
|issue = 3
|pages = 341–8
|date = 1997
|doi = 10.1080/095530097143338
|pmid = 9298114
}}</ref>

===Detection in biological specimens===
Polonium-210 may be quantified in biological specimens by alpha particle spectrometry to confirm a diagnosis of poisoning in hospitalized patients or to provide evidence in a medicolegal death investigation. The baseline urinary excretion of polonium-210 in healthy persons due to routine exposure to environmental sources is normally in a range of 5–15 mBq/day. Levels in excess of 30 mBq/day are suggestive of excessive exposure to the radionuclide.<ref>Baselt, R. [http://www.biomedicalpublications.com/dt10.pdf ''Disposition of Toxic Drugs and Chemicals in Man''] {{Webarchive|url=https://web.archive.org/web/20130616021325/http://www.biomedicalpublications.com/dt10.pdf |date=2013-06-16 }}, 10th edition, Biomedical Publications, Seal Beach, CA.</ref>

===Occurrence in humans and the biosphere===
Polonium-210 is widespread in the [[Biology:Biosphere|biosphere]], including in human tissues, because of its position in the uranium-238 decay chain. Natural [[Physics:Uranium-238|uranium-238]] in the [[Earth:Earth's crust|Earth's crust]] decays through a series of solid radioactive intermediates including [[Physics:Radium-226|radium-226]] to the radioactive noble gas [[Physics:Radon-222|radon-222]], some of which, during its 3.8-day half-life, diffuses into the atmosphere. There it decays through several more steps to polonium-210, much of which, during its 138-day half-life, is washed back down to the Earth's surface, thus entering the biosphere, before finally decaying to stable [[Physics:Lead-206|lead-206]].<ref>{{cite journal|doi =10.1038/187211a0|pmid =13852349|title =Lead-210 and Polonium-210 in Grass|date =1960|last1 =Hill|first1 = C. R.|journal =Nature|volume =187|issue =4733|pages =211–212|bibcode = 1960Natur.187..211H|s2cid =4261294}}</ref><ref>{{cite journal|last = Hill|first = C. R.| date =1963|title = Natural occurrence of unsupported radium-F (Po-210) in tissue|journal = Health Physics|volume = 9|pages = 952–953|pmid = 14061910}}</ref><ref>{{cite journal|doi = 10.1007/BF00398136 |title = Polonium-210 and lead-210 in marine food chains|date = 1979|last1 = Heyraud|first1 = M.|last2 = Cherry|first2 = R. D.|journal = Marine Biology |volume = 52 |issue = 3 |pages = 227–236|s2cid = 58921750}}</ref>

As early as the 1920s, French biologist Antoine Lacassagne, using polonium provided by his colleague [[Biography:Marie Curie|Marie Curie]], showed that the element has a specific pattern of uptake in rabbit tissues, with high concentrations, particularly in [[Biology:Liver|liver]], kidney, and testes.<ref>Lacassagne, A. & Lattes, J. (1924) ''Bulletin d'Histologie Appliquée à la Physiologie et à la Pathologie'', '''1''', 279.</ref> More recent evidence suggests that this behavior results from polonium substituting for its congener sulfur, also in group 16 of the periodic table, in sulfur-containing amino-acids or related molecules<ref>{{cite journal|jstor = 3577929|pages = 379–382|last1 = Vasken Aposhian|first1 = H.|last2 = Bruce|first2 = D. C.|title = Binding of Polonium-210 to Liver Metallothionein|volume = 126|issue = 3 |journal = Radiation Research |date = 1991 |doi = 10.2307/3577929 |pmid = 2034794|bibcode = 1991RadR..126..379A}}</ref> and that similar patterns of distribution occur in human tissues.<ref>{{cite journal |pmid = 5867584 |date = 1965 |last1 = Hill|first1 = C. R.|title = Polonium-210 in man|volume = 208|issue = 5009|pages = 423–8|journal = Nature |doi = 10.1038/208423a0|bibcode = 1965Natur.208..423H|s2cid = 4215661 }}</ref> Polonium is indeed an element naturally present in all humans, contributing appreciably to natural background dose, with wide geographical and cultural variations, and particularly high levels in arctic residents, for example.<ref>{{cite journal|doi = 10.1126/science.152.3726.1261 |title = Polonium-210 Content of Human Tissues in Relation to Dietary Habit|date = 1966|last1 = Hill|first1 = C. R.|journal = Science |volume = 152|issue = 3726|pages = 1261–2|pmid = 5949242 |bibcode = 1966Sci...152.1261H|s2cid = 33510717}}</ref>

===Tobacco===
[[Physics:Polonium-210|Polonium-210]] in tobacco contributes to many of the cases of lung cancer worldwide. Most of this polonium is derived from [[Physics:Lead-210|lead-210]] deposited on tobacco leaves from the atmosphere; the lead-210 is a product of [[Physics:Radon-222|radon-222]] gas, much of which appears to originate from the decay of [[Physics:Radium-226|radium-226]] from fertilizers applied to the tobacco soils.<ref name="Muggli08" /><ref name="Martell1974">{{cite journal|last1=Martell|first1=E. A.|title=Radioactivity of tobacco trichomes and insoluble cigarette smoke particles|journal=Nature|date=1974|volume=249|issue=5454|pages=214–217|doi=10.1038/249215a0|pmid=4833238|bibcode=1974Natur.249..215M|s2cid=4281866}}</ref><ref name="Martell1975">{{cite journal|last1=Martell|first1=E. A.|title=Tobacco 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 smokers|journal=American Scientist|date=1975|volume=63|issue=4|pages=404–412|jstor=27845575|bibcode = 1975AmSci..63..404M |pmid=1137236}}</ref><ref>{{cite journal|journal=Journal of the Royal Society of Medicine|volume= 101|issue= 3|pages= 156–7|title= The big idea: polonium, radon and cigarettes|doi=10.1258/jrsm.2007.070021 |pmid= 18344474|pmc= 2270238|year= 2008|last1= Tidd|first1= M. J.}}</ref><ref>Birnbauer, William (2008-09-07) [http://www.theage.com.au/national/big-tobacco-covered-up-radiation-danger-20080906-4b54.html?page=-1 "Big Tobacco covered up radiation danger"]. ''The Age'', Melbourne, Australia</ref>

The presence of polonium in tobacco smoke has been known since the early 1960s.<ref>{{cite journal| author = Radford EP Jr| author2 = Hunt VR |title = Polonium 210: a volatile radioelement in cigarettes |journal = Science| date =1964| volume = 143| issue = 3603 | doi = 10.1126/science.143.3603.247| pmid=14078362| bibcode=1964Sci...143..247R| pages = 247–9| s2cid = 23455633 }}</ref><ref>{{cite journal| author = Kelley TF| title = Polonium 210 content of mainstream cigarette smoke| journal = Science| date =1965| volume =149| issue = 3683| pages = 537–538| doi = 10.1126/science.149.3683.537 | pmid = 14325152|bibcode = 1965Sci...149..537K| s2cid = 22567612}}</ref> Some of the world's biggest tobacco firms researched ways to remove the substance—to no avail—over a 40-year period. The results were never published.<ref name="Muggli08" />

===Food===
Polonium is found in the food chain, especially in seafood.<ref>{{cite journal|display-authors = 4|author = Ota, Tomoko|author2 = Sanada, Tetsuya|author3 = Kashiwara, Yoko|author4 = Morimoto, Takao|author5 = Sato, Kaneaki|name-list-style = amp|journal = Japanese Journal of Health Physics|date = 2009|volume = 44|title = Evaluation for Committed Effective Dose Due to Dietary Foods by the Intake for Japanese Adults|url = http://ci.nii.ac.jp/naid/110007226760|doi = 10.5453/jhps.44.80|pages = 80–88|doi-access = free}}</ref><ref>{{cite journal|author = Smith-Briggs, JL|author2 = Bradley, EJ|journal =Science of the Total Environment |date=1984 |volume=35 |title=Measurement of natural radionuclides in U.K. diet |pmid=6729447 |issue=3 |pages=431–40|doi = 10.1016/0048-9697(84)90015-9|bibcode=1984ScTEn..35..431S}}</ref>

==See also==
* Polonium halo
* Poisoning of Alexander Litvinenko

==References==
{{Reflist|30em}}

==Bibliography==
* {{cite book |title=Advances in Inorganic Chemistry and Radiochemistry |chapter=The Chemistry of Polonium |ref=Bagnall|last1=Bagnall |first1=K. W. |date=1962 |publisher=[[Company:Academic Press|Academic Press]] |location=New York |isbn=978-0-12-023604-6|doi=10.1016/S0065-2792(08)60268-X|pages=197–226 |access-date=June 14, 2012 |chapter-url=https://books.google.com/books?id=8qePsa3V8GQC&pg=PA212|volume=4}}
* {{cite book|ref=Greenwood|author=Greenwood, Norman N.|author2=Earnshaw, Alan |date=1997|title= Chemistry of the Elements|edition= 2nd|publisher= Butterworth–Heinemann|isbn=978-0080379418}}

==External links==
{{Commons|Polonium}}
* [http://www.periodicvideos.com/videos/084.htm Polonium] at ''The Periodic Table of Videos'' (University of Nottingham)

{{Periodic table (navbox)}}


[[Category:Chemical elements]]
[[Category:Chalcogens]]
[[Category:Post-transition metals]]
[[Category:Element toxicology]]
[[Category:IARC Group 1 carcinogens]]
[[Category:Chemical elements predicted by Dmitri Mendeleev]]

{{Sourceattribution|Polonium}}