Editing Bromine (section)

==Biological role and toxicity==
{{main|Vanadium bromoperoxidase|Eosinophil peroxidase|Bromism}}

A 2014 study suggests that bromine (in the form of bromide ion) is a necessary cofactor in the biosynthesis of [[collagen IV]], making the element [[essential element|essential]] to [[basement membrane]] architecture and tissue development in animals.<ref name="pmid24906154">{{Cite journal| display-authors = 5| author = McCall AS| author2 = Cummings CF| author3 = Bhave G| author4 = Vanacore R| author5 = Page-McCaw A| author6 = Hudson BG|title = Bromine Is an Essential Trace Element for Assembly of Collagen IV Scaffolds in Tissue Development and Architecture|journal = Cell|volume = 157|issue = 6|pages = 1380–92|date = 2014|pmid = 24906154|doi=10.1016/j.cell.2014.05.009| pmc=4144415}}</ref> Nevertheless, no clear deprivation symptoms or syndromes have been documented in mammals.<ref name="Nielsen2000">{{cite book|last1=Nielsen|first1=Forrest H.|title=Clinical Nutrition of the Essential Trace Elements and Minerals |chapter=Possibly Essential Trace Elements|year=2000|pages= 11–36|chapter-url=https://archive.org/details/clinicalnutritio0000unse_l0q5/page/11|doi=10.1007/978-1-59259-040-7_2|isbn=978-1-61737-090-8}}</ref> In other biological functions, bromine may be non-essential but still beneficial when it takes the place of chlorine. For example, in the presence of hydrogen peroxide, [[H2O2|H{{sub|2}}O{{sub|2}}]], formed by the [[eosinophil]], and either chloride, iodide, thiocyanate, or bromide ions, [[eosinophil peroxidase]] provides a potent mechanism by which eosinophils kill multicellular [[parasitism|parasites]] (such as the nematode worms involved in [[filariasis]]) and some [[bacteria]] (such as [[tuberculosis]] bacteria). Eosinophil peroxidase is a [[haloperoxidase]] that preferentially uses bromide over chloride for this purpose, generating [[hypobromite]] ([[hypobromous acid]]), although the use of chloride is possible.<ref name="pmid2538427">{{Cite journal| author = Mayeno AN| author2 = Curran AJ| author3 = Roberts RL| author4 = Foote CS|title = Eosinophils preferentially use bromide to generate halogenating agents|journal = J. Biol. Chem.|volume = 264|issue = 10|pages = 5660–8|date = 1989| doi = 10.1016/S0021-9258(18)83599-2|pmid = 2538427|doi-access = free}}</ref>

[[File:2-Octyl 4-bromo-3-oxobutanoate.svg|thumb|right|upright=1.2|Octan-2-yl 4-bromo-3-oxobutanoate, an organobromine compound found in mammalian cerebrospinal fluid]]

α-Haloesters are generally thought of as highly reactive and consequently toxic intermediates in organic synthesis. Nevertheless, mammals, including humans, cats, and rats, appear to biosynthesize traces of an α-bromoester, 2-octyl 4-bromo-3-oxobutanoate, which is found in their [[cerebrospinal fluid]] and appears to play a yet unclarified role in inducing REM sleep.<ref name="Gribble99" /> Neutrophil myeloperoxidase can use H{{sub|2}}O{{sub|2}} and Br{{sup|−}} to brominate deoxycytidine, which could result in DNA mutations.<ref name="pmid11096071">{{Cite journal| author = Henderson JP| author2 = Byun J| author3 = Williams MV| author4 = Mueller DM|title = Production of brominating intermediates by myeloperoxidase.|journal = J. Biol. Chem.|volume = 276|issue = 11|pages = 7867–75|date = 2001|pmid =11096071| doi = 10.1074/jbc.M005379200|doi-access = free}}</ref> Marine organisms are the main source of organobromine compounds, and it is in these organisms that bromine is more firmly shown to be essential. More than 1600 such organobromine compounds were identified by 1999. The most abundant is [[methyl bromide]] (CH{{sub|3}}Br), of which an estimated 56,000 tonnes is produced by marine algae each year.<ref name="Gribble99">{{Cite journal|title = The diversity of naturally occurring organobromine compounds|author = Gribble, Gordon W. |journal = Chemical Society Reviews| volume = 28|pages = 335–346|date = 1999|doi = 10.1039/a900201d|issue = 5}}</ref> The essential oil of the Hawaiian alga ''[[Asparagopsis taxiformis]]'' consists of 80% [[bromoform]].<ref>{{Cite journal|title = Volatile halogen compounds in the alga Asparagopsis taxiformis (Rhodophyta)|first = B. Jay|last = Burreson|author2= Moore, Richard E.|author3= Roller, Peter P.|journal = [[Journal of Agricultural and Food Chemistry]]|date = 1976|volume = 24|pages = 856–861|doi = 10.1021/jf60206a040|issue = 4| bibcode=1976JAFC...24..856B }}</ref> Most of such organobromine compounds in the sea are made by the action of a unique algal enzyme, [[vanadium bromoperoxidase]].<ref>{{Cite journal|journal = Natural Product Reports|date = 2004|volume = 21|issue = 1|pmid = 15039842|doi = 10.1039/b302337k|title = The role of vanadium bromoperoxidase in the biosynthesis of halogenated marine natural products|first = Alison|last = Butler|author2=Carter-Franklin, Jayme N.|s2cid = 19115256|pages = 180–8}}</ref>

The bromide anion is not very toxic: a normal daily intake is 2 to 8&nbsp;milligrams.<ref name="Nielsen2000" /> However, high levels of bromide chronically impair the membrane of neurons, which progressively impairs neuronal transmission, leading to toxicity, known as [[bromism]]. Bromide has an [[elimination half-life]] of 9 to 12 days, which can lead to excessive accumulation. Doses of 0.5 to 1&nbsp;gram per day of bromide can lead to bromism. Historically, the therapeutic dose of bromide is about 3 to 5&nbsp;grams of bromide, thus explaining why chronic toxicity (bromism) was once so common. While significant and sometimes serious disturbances occur to neurologic, psychiatric, dermatological, and gastrointestinal functions, death from bromism is rare.<ref name="pdo2003">{{cite book |last1=Olson |first1=Kent R. |title=Poisoning & drug overdose |url=https://books.google.com/books?id=vuec3nTovyUC |edition=4th |date=1 November 2003 |publisher=Appleton & Lange |isbn=978-0-8385-8172-8 |pages=140–141 |access-date=5 November 2016 |archive-date=24 December 2016 |archive-url=https://web.archive.org/web/20161224042040/https://books.google.com/books?id=vuec3nTovyUC |url-status=live }}</ref> Bromism is caused by a neurotoxic effect on the brain which results in [[somnolence]], [[psychosis]], [[seizures]] and [[delirium]].<ref>{{cite book |last1=Galanter |first1=Marc |last2=Kleber |first2=Herbert D. |title=The American Psychiatric Publishing Textbook of Substance Abuse Treatment |url=https://books.google.com/books?id=6wdJgejlQzYC |edition=4th |date=1 July 2008 |publisher=American Psychiatric Publishing Inc |location=United States of America |isbn=978-1-58562-276-4 |page=217 |access-date=5 November 2016 |archive-date=27 April 2021 |archive-url=https://web.archive.org/web/20210427154856/https://books.google.com/books?id=6wdJgejlQzYC |url-status=live }}</ref>

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Elemental bromine (Br{{sub|2}}) is toxic and causes [[chemical burns]] on human flesh. Inhaling bromine gas results in similar irritation of the respiratory tract, causing coughing, choking, shortness of breath, and death if inhaled in large enough amounts. Chronic exposure may lead to frequent bronchial infections and a general deterioration of health. As a strong oxidising agent, bromine is incompatible with most organic and inorganic compounds.<ref name="msds">{{cite web |url=https://www.sciencelab.com/msds.php?msdsId=9927659 |title=Material Safety Data Sheet: Bromine MSDS |author=Science Lab.com |website=sciencelab.com |access-date=27 October 2016 |archive-url=https://web.archive.org/web/20171115230355/https://www.sciencelab.com/msds.php?msdsId=9927659 |archive-date=15 November 2017 |url-status=dead }}</ref> Caution is required when transporting bromine; it is commonly carried in steel tanks lined with lead, supported by strong metal frames.<ref name="Greenwood798" /> The [[Occupational Safety and Health Administration]] (OSHA) of the [[United States]] has set a [[permissible exposure limit]] (PEL) for bromine at a time-weighted average (TWA) of 0.1&nbsp;ppm. The [[National Institute for Occupational Safety and Health]] (NIOSH) has set a [[recommended exposure limit]] (REL) of TWA 0.1&nbsp;ppm and a short-term limit of 0.3&nbsp;ppm. The exposure to bromine [[immediately dangerous to life and health]] (IDLH) is 3&nbsp;ppm.<ref>{{PGCH|0064}}</ref> Bromine is classified as an [[List of extremely hazardous substances|extremely hazardous substance]] in the United States as defined in Section 302 of the U.S. [[Emergency Planning and Community Right-to-Know Act]] (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.<ref name="gov-right-know">{{Cite journal  | title = 40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities | url = https://edocket.access.gpo.gov/cfr_2008/julqtr/pdf/40cfr355AppA.pdf | edition = 1 July 2008 | access-date = 29 October 2011 | archive-url = https://web.archive.org/web/20120225051612/https://edocket.access.gpo.gov/cfr_2008/julqtr/pdf/40cfr355AppA.pdf | archive-date = 25 February 2012 | url-status = dead |journal =[[Federal Register]] | publisher = [[United States Government Publishing Office|Government Printing Office]] }}</ref>