Perfluorohexanesulfonic acid

Last updated
Perfluorohexanesulfonic acid
Perfluorohexanesulfonic acid.svg
PFHxS 3D.png
Names
IUPAC name
1,1,2,2,3,3,4,4,5,5,6,6,6-tridecafluorohexane-1-sulfonic acid
Other names
  • PFHxS
  • Perfluorohexane sulfonate
  • Perfluorohexane sulfonic acid
  • Perfluorohexane-1-sulfonic acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.005.989 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 206-587-1
PubChem CID
UNII
  • InChI=1S/C6HF13O3S/c7-1(8,3(11,12)5(15,16)17)2(9,10)4(13,14)6(18,19)23(20,21)22/h(H,20,21,22)
    Key: QZHDEAJFRJCDMF-UHFFFAOYSA-N
  • C(C(C(C(F)(F)S(=O)(=O)O)(F)F)(F)F)(C(C(F)(F)F)(F)F)(F)F
Properties
C6HF13O3S
Molar mass 400.11 g·mol−1
Density 1.841 g·cm−3 [1]
6.2 mg/L (25 °C) [1]
log P 3.7 (estimated) [1]
Vapor pressure 0.0046 mmHg (estimated) [2]
Acidity (pKa)−3.45 [2]
Hazards
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-exclam.svg [1]
Danger
H302, H312, H314, H332
P260, P261, P264, P270, P271, P280, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P322, P330, P363, P405, P501
Pharmacology
Legal status
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Perfluorohexanesulfonic acid (PFHxS) (conjugate base perfluorohexanesulfonate) is a synthetic chemical compound. It is one of many compounds collectively known as per- and polyfluoroalkyl substances (PFASs). It is an anionic fluorosurfactant and a persistent organic pollutant with bioaccumulative properties. Although the use of products containing PFHxS and other PFASs have been banned or are being phased out in many jurisdictions, it remains ubiquitous in many environments and within the general population, and is one of the most commonly detected PFASs. [4]

Contents

Biochemical properties

PFHxS has a six carbon fluorocarbon chain that is both hydrophobic and lipophobic. Its sulfonic acid functional group imparts polarity, and allows it to interact with other polar compounds. Due to the strength of its carbon-fluorine bonds, it persists in the environment and in living organisms.

In humans, PFHxS binds to blood albumin, [5] and relatively little PFHxS is found in the liver compared to longer chain PFASs such as PFOS. [6] The half-life of PFASs in human blood generally decreases with decreasing backbone (CF2) length. However, PFHxS is an unusual exception in that its half-life is greater than both longer and shorter chain equivalents such as PFOS or PFBS. [7]

Production

PFHxS, its salts and isomers are anthropogenic chemicals that do not occur naturally. It is used as a surfactant and protective coating in applications such as aqueous firefighting foams, textile coating, metal plating and in polishing agents. [8] [9] PFHxS production is slowly being phased out since 3M stopped producing C6 fluorotelomers in 2002, but production by other companies may be ongoing. [4] Between 1958 and 2015, an estimated 120-1022 metric tonnes of PFHxS were produced. [9] PFHxS was also used as replacement for PFOS after the Stockholm Convention on persistent organic pollutants restricted the use of PFOS. [8] The exact quantity of PFHxS produced or in production is difficult to estimate, as production volumes and relevant formulation information is often not publicly available. PFHxS may also be formed as an impurity of PFOS production, or as a breakdown product of larger PFASs. [10]

Occurrence in Humans

Data from the 2003-2004 National Health and Nutrition Examination Survey in the United States found the average serum concentration of PFHxS in the general US population to be 1.9 μg/L, with the 10th and 90th percentiles being 0.7 and 8.3 μg/L, respectively. Some studies reported serum PFHxS concentrations in the United States to be gradually decreasing since at least 1999. [11] [12] Nevertheless, evidence of exposure can be detected amongst people with historic exposure. Serum concentrations of PFHxS were elevated amongst a cohort of Australian firefighters with occupational exposure to PFHxS (mean = 33 μg/L) compared to the general Australian population (mean = 3.2 μg/L), and were significantly correlated with serum PFOS concentrations. [13] As with PFOS, serum PFHxS concentrations are lower amongst women and people who reported blood donation. [13] [14]

There is limited evidence for a relationship between PFHxS exposure and various health outcomes. However, contributions from PFHxS specifically are difficult to isolate, as most studies in humans and higher order organisms investigate exposure to a complex mixture of PFASs, of which PFHxS is just one component.

Regulatory status

A number of jurisdictions have guidelines or limits for the concentration of PFHxS in water, in diets, and in the environment. There are fewer regulations on PFHxS compared to PFOS and PFOA. This reflects the relative lack of epidemiological and toxicological information on the human health effects of exposure to PFHxS. [4]

PFHxS, its salts and related compounds have been recommended to be added to Annex A of the United Nations Stockholm Convention on Persistent Organic Pollutants. The decision was initially scheduled to be made in June 2021. [15] Due to the COVID-19 pandemic, the decision at the conference of parties was deferred to June 2022, where the parties agreed to list PFHxS, its salts and related compounds in Annex a without specific exemptions. [16] Upon entry into force, nations party to the convention are legally bound to take act to cease production and use of PFHxS. Several hundred salts and precursors of PFHxS fall within the scope of the restriction. [17]

Australia

Food Standards Australia New Zealand found insufficient evidence to justify a tolerable daily intake (TDI) for PFHxS specifically. Therefore the TDI level for PFOS (0.02 μg/kg) was adapted as the TDI for the sum of PFOS and PFHxS. Australia uses a drinking water guideline value of 0.07 μg/L for the sum of PFHxS and PFOS. In comparison, the drinking water guideline value for PFOA is 0.56 μg/L. [18]

Europe

A new EU drinking water directive issued in 2020 adopted PFAS limit values. The limit values are 0.1 μg/L for the sum of 20 PFASs including PFHxS, and 0.5 μg/L for the sum of all PFASs. This directive is binding for all EU member nations. It is a minimum directive, and member states can elect to adopt stricter regulations. [19]

Denmark

The Danish EPA has established a drinking water and groundwater limit value of 2 ng/L for the sum of 4 PFASs; , PFHxS, PFOS, PFOA, and perfluorononanoic acid (PFNA). [20]

Sweden

The Swedish National Food Agency recommends a drinking water limit of 0.09 μg/L for the sum of 11 PFASs (PFBS, PFHxS, PFOS, 6:2 FTSA, PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA and PFDA). If PFASs are found above this limit in drinking water, immediate action is recommended to reduce the PFAS concentration in the drinking water to as far below the action level as possible. If PFASs is found above 900 ng/L in drinking water, the advice is to avoid drinking the water or preparing food with the water until the concentration is reduced as low as possible below 90 ng/litre, and to contact the Swedish Food Agency. [19]

Republic of Korea

In 2018, a preliminary drinking water limit value of 0.48 μg/L was adopted for PFHxS. In comparison, the preliminary limit value for the sum of PFOS and PFOA is 0.07 μg/L. [4]

United States

As of 2019, there is no federal limit or guideline value for PFHxS. The United States Environmental Protection Agency (EPA) is developing toxicity values for PFHxS, as well as PFBA, PFHxA, PFNA and PFDA. [21] [22] Meanwhile, some states have adopted their own guideline values for PFHxS. For example, Minnesota recommends a guidance value of 0.027 μg/L for PFHxS, [23] and Michigan has a screening level of 0.084 μg/L for PFHxS. [4]

In 2020, Michigan adopted drinking water standards for 5 previously unregulated PFASs including PFHxS, which has a maximum contaminant level (MCL) of 51 parts per trillion (ppt) or 0.051 μg/L. [24] [25]


See also

Related Research Articles

<span class="mw-page-title-main">Cape Fear River</span> River in North Carolina, United States

The Cape Fear River is a 191.08-mile-long blackwater river in east-central North Carolina. It flows into the Atlantic Ocean near Cape Fear, from which it takes its name. The river is formed at the confluence of the Haw River and the Deep River in the town of Moncure, North Carolina. Its river basin is the largest in the state: 9,149 sq mi.

<span class="mw-page-title-main">Perfluorooctanoic acid</span> Perfluorinated carboxylic acid

Perfluorooctanoic acid is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes and as a material feedstock. PFOA is considered a surfactant, or fluorosurfactant, due to its chemical structure, which consists of a perfluorinated, n-heptyl "tail group" and a carboxylate "head group". The head group can be described as hydrophilic while the fluorocarbon tail is both hydrophobic and lipophobic.

<span class="mw-page-title-main">Perfluorooctanesulfonic acid</span> Fluorosurfactant and persistent organic pollutant

Perfluorooctanesulfonic acid (PFOS) is a chemical compound having an eight-carbon fluorocarbon chain and a sulfonic acid functional group and thus a perfluorosulfonic acid. It is an anthropogenic (man-made) fluorosurfactant, now regarded as a global pollutant. PFOS was the key ingredient in Scotchgard, a fabric protector made by 3M, and related stain repellents. The acronym "PFOS" refers to the parent sulfonic acid and to various salts of perfluorooctanesulfonate. These are all colorless or white, water-soluble solids. Although of low acute toxicity, PFOS has attracted much attention for its pervasiveness and environmental impact. It was added to Annex B of the Stockholm Convention on Persistent Organic Pollutants in May 2009.

<span class="mw-page-title-main">Persistent organic pollutant</span> Organic compounds that are resistant to environmental degradation

Persistent organic pollutants (POPs) are organic compounds that are resistant to degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released.

<span class="mw-page-title-main">Tomalley</span> Lobster or crab organs eaten as a delicacy

Tomalley, crab fat, or lobster paste is the soft, green substance found in the body cavity of lobsters, that fulfills the functions of both the liver and the pancreas. Tomalley corresponds to the hepatopancreas in other arthropods. It is considered a delicacy, and may be eaten alone but is often added to sauces for flavour and as a thickening agent. The term lobster paste or lobster pâté can also be used to indicate a mixture of tomalley and lobster roe. Lobster bisque, lobster stock, and lobster consommé are made using lobster bodies (heads), often including tomalley.

<span class="mw-page-title-main">Microwave popcorn</span> Type of convenience food

Microwave popcorn is a convenience food consisting of unpopped popcorn in an enhanced, sealed paper bag intended to be heated in a microwave oven. In addition to the dried corn, the bags typically contain cooking oil with sufficient saturated fat to solidify at room temperature, one or more seasonings, and natural or artificial flavorings or both. With the many different flavors, there are many different providers.

<span class="mw-page-title-main">Environmental toxicology</span>

Environmental toxicology is a multidisciplinary field of science concerned with the study of the harmful effects of various chemical, biological and physical agents on living organisms. Ecotoxicology is a subdiscipline of environmental toxicology concerned with studying the harmful effects of toxicants at the population and ecosystem levels.

Perfluorononanoic acid, or PFNA, is a synthetic perfluorinated carboxylic acid and fluorosurfactant that is also an environmental contaminant found in people and wildlife along with PFOS and PFOA.

<span class="mw-page-title-main">Per- and polyfluoroalkyl substances</span> Class of perfluorinated chemical compounds

Per- and polyfluoroalkyl substances (PFAS or PFASs) are a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. An early definition, from 2011, required that they contain at least one perfluoroalkyl moiety, –CnF2n+1–. Beginning in 2021, the Organisation for Economic Co-operation and Development (OECD) expanded their terminology, stating that "PFASs are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e. with a few noted exceptions, any chemical with at least a perfluorinated methyl group (–CF3) or a perfluorinated methylene group (–CF2–) is a PFAS."

Fluorotelomer alcohols, or FTOHs, are fluorotelomers with an alcohol functional group. They are volatile precursors to perfluorinated carboxylic acids, such as PFOA and PFNA, and other compounds.

<span class="mw-page-title-main">Perfluorobutanesulfonic acid</span> Chemical compound

Perfluorobutanesulfonic acid (PFBS) is a PFAS chemical compound having a four-carbon fluorocarbon chain and a sulfonic acid functional group. It is stable and unreactive because of the strength of carbon–fluorine bonds. It can occur in the form of a colorless liquid or a corrosive solid. Its conjugate base is perfluorobutanesulfonate which functions as the hydrophobe in fluorosurfactants.

Fluorotelomers are fluorocarbon-based oligomers, or telomers, synthesized by telomerization. Some fluorotelomers and fluorotelomer-based compounds are a source of environmentally persistent perfluorinated carboxylic acids such as PFOA and PFNA, while others are under extended investigation.

<span class="mw-page-title-main">Perfluorinated compound</span>

A perfluorinated compound (PFC) or perfluoro compound is an organofluorine compound lacking C-H bonds. Many perfluorinated compounds have properties that are quite different from their C-H containing analogues. Common functional groups in PFCs are OH, CO2H, chlorine, O, and SO3H. Electrofluorination is the predominant method for their production. Due to their chemical stability, some of these perfluorinated compounds bioaccumulate.

<span class="mw-page-title-main">Perfluorooctanesulfonamide</span> Chemical compound

Perfluorooctanesulfonamide (PFOSA) is a synthetic organofluorine compound. It is a fluorocarbon derivative and a perfluorinated compound, having an eight-carbon chain and a terminal sulfonamide functional group. PFOSA, a persistent organic pollutant, was an ingredient in 3M's former Scotchgard formulation from 1956 until 2003, and the compound was used to repel grease and water in food packaging along with other consumer applications. It breaks down to form perfluorooctane sulfonate (PFOS). The perfluorooctanesulfonyl fluoride-based chemistry that was used to make sulfonamides like PFOSA was phased out by 3M in the United States (US) during 2000–2002 but it has grown in China by other producers.

<span class="mw-page-title-main">Perfluorooctanesulfonyl fluoride</span> Chemical compound

Perfluorooctanesulfonyl fluoride (POSF) is a synthetic perfluorinated compound with a sulfonyl fluoride functional group. It is used to make perfluorooctanesulfonic acid (PFOS) and PFOS-based compounds. These compounds have a variety of industrial and consumer uses, but POSF-derived substances ultimately degrade to form PFOS.

<span class="mw-page-title-main">Oral-B Glide</span> Dental floss brand

Oral-B Glide is a PTFE (Teflon) dental floss manufactured by W. L. Gore and Associates exclusively for Procter & Gamble.

<span class="mw-page-title-main">Biological aspects of fluorine</span>

Fluorine may interact with biological systems in the form of fluorine-containing compounds. Though elemental fluorine (F2) is very rare in everyday life, fluorine-containing compounds such as fluorite occur naturally as minerals. Naturally occurring organofluorine compounds are extremely rare. Man-made fluoride compounds are common and are used in medicines, pesticides, and materials. Twenty percent of all commercialized pharmaceuticals contain fluorine, including Lipitor and Prozac. In many contexts, fluorine-containing compounds are harmless or even beneficial to living organisms; in others, they are toxic.

<span class="mw-page-title-main">Water contamination in Lawrence and Morgan Counties, Alabama</span>

Water contamination in Lawrence and Morgan Counties, Alabama, revolves around the presence of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in the water supply. After the US Environmental Protection Agency (EPA) released new health advisories in March 2016, there was concern over health risks of the levels of PFOA and PFOS present. The responses of different government officials, agencies, and companies raise questions as to whether or not there was any environmental injustice involved.

GenX is a Chemours trademark name for a synthetic, short-chain organofluorine chemical compound, the ammonium salt of hexafluoropropylene oxide dimer acid (HFPO-DA). It can also be used more informally to refer to the group of related fluorochemicals that are used to produce GenX. DuPont began the commercial development of GenX in 2009 as a replacement for perfluorooctanoic acid.

This timeline of events related to per- and polyfluoroalkyl substances (PFASs) includes events related to the discovery, development, manufacture, marketing, uses, concerns, litigation, regulation, and legislation, involving the human-made PFASs. The timeline focuses on some perfluorinated compounds, particularly perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) and on the companies that manufactured and marketed them, mainly DuPont and 3M. An example of PFAS is the fluorinated polymer polytetrafluoroethylene (PTFE), which has been produced and marketed by DuPont under its trademark Teflon. GenX chemicals and perfluorobutanesulfonic acid (PFBS) are organofluorine chemicals used as a replacement for PFOA and PFOS.

References

  1. 1 2 3 4 "Perfluorohexanesulfonic acid". Pubchem. National Library of MEdicine. Retrieved 22 May 2021.
  2. 1 2 Wang, Zhanyun; MacLeod, Matthew; Cousins, Ian T.; Scheringer, Martin; Hungerbühler, Konrad (2011). "Using COSMOtherm to predict physicochemical properties of poly- and perfluorinated alkyl substances (PFASs)". Environmental Chemistry. 8 (4): 389. doi: 10.1071/EN10143 . ISSN   1448-2517.
  3. ↑ An Act To Stop Perfluoroalkyl and Polyfluoroalkyl Substances Pollution. 130th Maine Legislature, April 15, 2021
  4. 1 2 3 4 5 Stockholm Convention on Persistent Organic Pollutants (1 October 2019). Risk management evaluation on perfluorohexane sulfonic acid (PFHxS), its salts and PFHxS-related compounds (addendum) (Report). United Nations Environment Programme. Retrieved 23 May 2021.
  5. ↑ Forsthuber M, Kaiser AM, Granitzer S, Hassl I, Hengstschläger M, Stangl H; et al. (2020). "Albumin is the major carrier protein for PFOS, PFOA, PFHxS, PFNA and PFDA in human plasma". Environ Int. 137: 105324. doi: 10.1016/j.envint.2019.105324 . PMID   32109724.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ↑ Kärrman A, Domingo JL, Llebaria X, Nadal M, Bigas E, van Bavel B; et al. (2010). "Biomonitoring perfluorinated compounds in Catalonia, Spain: concentrations and trends in human liver and milk samples". Environ Sci Pollut Res Int. 17 (3): 750–8. doi:10.1007/s11356-009-0178-5. PMID   19458971. S2CID   12628985.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ↑ Li Y, Fletcher T, Mucs D, Scott K, Lindh CH, Tallving P; et al. (2018). "Half-lives of PFOS, PFHxS and PFOA after end of exposure to contaminated drinking water". Occup Environ Med. 75 (1): 46–51. doi:10.1136/oemed-2017-104651. PMC   5749314 . PMID   29133598.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. 1 2 Wang, Zhanyun; Cousins, Ian T.; Scheringer, Martin; Hungerbühler, Konrad (2013). "Fluorinated alternatives to long-chain perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkane sulfonic acids (PFSAs) and their potential precursors". Environment International. 60: 242–248. doi:10.1016/j.envint.2013.08.021. ISSN   0160-4120. PMID   24660230.
  9. 1 2 Boucher, Justin M.; Cousins, Ian T.; Scheringer, Martin; Hungerbühler, Konrad; Wang, Zhanyun (2018). "Toward a Comprehensive Global Emission Inventory of C4–C10 Perfluoroalkanesulfonic Acids (PFSAs) and Related Precursors: Focus on the Life Cycle of C6- and C10-Based Products". Environmental Science & Technology Letters. 6 (1): 1–7. doi:10.1021/acs.estlett.8b00531. hdl: 20.500.11850/308867 . ISSN   2328-8930. S2CID   135460867.
  10. ↑ Jiang W, Zhang Y, Yang L, Chu X, Zhu L (2015). "Perfluoroalkyl acids (PFAAs) with isomer analysis in the commercial PFOS and PFOA products in China". Chemosphere. 127: 180–7. Bibcode:2015Chmsp.127..180J. doi:10.1016/j.chemosphere.2015.01.049. PMID   25703780.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  11. ↑ Olsen GW, Mair DC, Lange CC, Harrington LM, Church TR, Goldberg CL; et al. (2017). "Per- and polyfluoroalkyl substances (PFAS) in American Red Cross adult blood donors, 2000-2015". Environ Res. 157: 87–95. Bibcode:2017ER....157...87O. doi: 10.1016/j.envres.2017.05.013 . PMID   28528142.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  12. ↑ Calafat AM, Wong LY, Kuklenyik Z, Reidy JA, Needham LL (2007). "Polyfluoroalkyl chemicals in the U.S. population: data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004 and comparisons with NHANES 1999-2000". Environ Health Perspect. 115 (11): 1596–602. doi:10.1289/ehp.10598. PMC   2072821 . PMID   18007991.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  13. 1 2 Rotander A, Toms LM, Aylward L, Kay M, Mueller JF (2015). "Elevated levels of PFOS and PFHxS in firefighters exposed to aqueous film forming foam (AFFF)". Environ Int. 82: 28–34. doi:10.1016/j.envint.2015.05.005. PMID   26001497.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  14. ↑ Yeung LW, So MK, Jiang G, Taniyasu S, Yamashita N, Song M; et al. (2006). "Perfluorooctanesulfonate and related fluorochemicals in human blood samples from China". Environ Sci Technol. 40 (3): 715–20. Bibcode:2006EnST...40..715Y. doi:10.1021/es052067y. PMID   16509308.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  15. ↑ "Big Year for chemicals & waste continues as UN experts take steps to recommend eliminating UV-328 (a toxic plastic additive)" (Press release). Geneva, Switzerland: Secretariat of the Basel, Rotterdam and Stockholm Conventions. 16 January 2021. Retrieved 2021-05-23.
  16. ↑ "Report of main proceedings for 9 June 2022". IISD Earth Negotiations Bulletin. Retrieved 2022-06-12.
  17. ↑ "PFAS and Fluorinated Compounds in PubChem Tree". PubChem Classification Browser. NCBI . Retrieved 2022-10-21. → Regulatory PFAS collections → PFHxS and related substances → [Annex A] PFHxS plus its salts and PFHxS-related compounds as defined in Annex A of the Stockholm Convention
  18. ↑ National Health and Medical Research Council (March 2021). Australian Drinking Water Guidelines (2011) – Updated March 2021 (Report). National Health and Medical Research Council.
  19. 1 2 Swedish Food Agency (5 February 2021). "PFAS in drinking water and self-caught fish - risk management". Swedish Food Agency. Retrieved 23 May 2021.
  20. ↑ "Skærpede krav til PFAS-stoffer i drikkevand". mst.dk (in Danish). Retrieved 2023-01-30.
  21. ↑ United States Environmental Protection Agency (February 2019). EPA's Per- and Polyfluoroalkyl Substances (PFAS) Action Plan (PDF) (Report). United States Environmental Protection Agency. Retrieved 23 May 2021.
  22. ↑ "Perfluorohexanesulfonic Acid (PFHxS)". Integrated Risk Information System. United States Environmental Protection Agency. Retrieved 22 May 2021.
  23. ↑ Minnesota Department of Health (April 2019). PFHxS and groundwater (PDF) (Report). Minnesota Department of Health. Retrieved 23 May 2021.
  24. ↑ Matheny, Keith (3 August 2020). "Michigan's drinking water standards for these chemicals now among toughest in nation". Detroit Free Press. Archived from the original on 31 January 2022. Retrieved 31 March 2022.
  25. ↑ "New state drinking water standards pave way for expansion of Michigan's PFAS clean-up efforts". Michigan.gov. 3 August 2020. Archived from the original on 3 January 2022. Retrieved 5 April 2022.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.