Editing Boron (section)

==Biological role==
{{see also|Boron deficiency (plant disorder)}}
Boron is an essential plant [[nutrient]], required primarily for maintaining the integrity of cell walls. However, high soil concentrations of greater than 1.0&nbsp;[[parts per million|ppm]] lead to marginal and tip necrosis in leaves as well as poor overall growth performance. Levels as low as 0.8&nbsp;ppm produce these same symptoms in plants that are particularly sensitive to boron in the soil. Nearly all plants, even those somewhat tolerant of soil boron, will show at least some symptoms of boron toxicity when soil boron content is greater than 1.8&nbsp;ppm. When this content exceeds 2.0&nbsp;ppm, few plants will perform well and some may not survive.<ref>{{Cite news|url = http://info.ag.uidaho.edu/Resources/PDFs/CIS1085.pdf|archive-url = https://web.archive.org/web/20091001005107/http://info.ag.uidaho.edu/Resources/PDFs/CIS1085.pdf|archive-date = 1 October 2009| publisher = University of Idaho| title = Essential Plant Micronutrients. Boron in Idaho| first = R. L.|last = Mahler| access-date= 5 May 2009}}</ref><ref>{{cite web|title = Functions of Boron in Plant Nutrition|url = http://www.borax.com/agriculture/files/an203.pdf|archive-url = https://web.archive.org/web/20090320175602/http://www.borax.com/agriculture/files/an203.pdf|archive-date = 20 March 2009|publisher = U.S. Borax Inc. }}</ref><ref>{{Cite journal|title = Functions of Boron in Plant Nutrition|first1 = Dale G.|last1 = Blevins|journal = Annual Review of Plant Physiology and Plant Molecular Biology|volume = 49|pages = 481–500|date = 1998|doi = 10.1146/annurev.arplant.49.1.481|pmid = 15012243|last2 = Lukaszewski|first2 = K. M.}}</ref>

Some boron-containing [[antibiotic]]s exist in nature.<ref>{{cite journal|title = The tartrolons, new boron-containing antibiotics from a myxobacterium, ''Sorangium cellulosum''|journal = The Journal of Antibiotics|volume = 48|issue = 1|pages = 26–30|pmid = 7532644|vauthors = Irschik H, Schummer D, Gerth K, Höfle G, Reichenbach H|year = 1995|doi = 10.7164/antibiotics.48.26|url = https://www.jstage.jst.go.jp/article/antibiotics1968/48/1/48_1_26/_pdf|doi-access = free|access-date = 28 August 2019|archive-date = 10 May 2020|archive-url = https://web.archive.org/web/20200510223356/https://www.jstage.jst.go.jp/article/antibiotics1968/48/1/48_1_26/_pdf|url-status = live}}</ref> The first one found was [[boromycin]], isolated from [[streptomyces]] in the 1960s.<ref>{{Cite journal|last1=Hütter|first1=R.|last2=Keller-Schien|first2=W.|last3=Knüsel|first3=F.|last4=Prelog|first4=V.|last5=Rodgers Jr.|first5=G. C.|last6=Suter|first6=P.|last7=Vogel|first7=G.|last8=Voser|first8=W.|last9=Zähner|first9=H.|title=Stoffwechselprodukte von Mikroorganismen. 57. Mitteilung. Boromycin|date=1967|journal=[[Helvetica Chimica Acta]]|volume=50|issue=6|pages=1533–1539|doi=10.1002/hlca.19670500612|pmid=6081908}}</ref><ref>{{Cite journal | last1 = Dunitz | first1 = J. D. | last2 = Hawley | first2 = D. M. | last3 = Miklos | first3 = D. | last4 = White | first4 = D. N. J. | last5 = Berlin | first5 = Y. | last6 = Marusić | first6 = R. | last7 = Prelog | first7 = V. | doi = 10.1002/hlca.19710540624 | title = Structure of boromycin | journal = Helvetica Chimica Acta | volume = 54 | issue = 6 | pages = 1709–1713 | date = 1971 | pmid = 5131791 }}</ref> Others are [[tartrolon]]s, a group of antibiotics discovered in the 1990s from culture broth of the [[Myxobacteria|myxobacterium]] ''[[Sorangium cellulosum]]''.<ref name="wiley199419940310">{{cite journal |last1=Schummer |first1=Dietmar |last2=Irschik |first2=Herbert |last3=Reichenbach |first3=Hans |last4=Höfle |first4=Gerhard |date=11 March 1994 |title=Antibiotics from gliding bacteria, LVII. Tartrolons: New boron-containing macrodiolides fromSorangium cellulosum |url=https://onlinelibrary.wiley.com/doi/10.1002/jlac.199419940310 |journal=Liebigs Annalen der Chemie |language=de |volume=1994 |issue=3 |pages=283–289 |doi=10.1002/jlac.199419940310 |url-access=subscription |access-date=19 October 2023 |archive-date=8 March 2024 |archive-url=https://web.archive.org/web/20240308023527/https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/jlac.199419940310 |url-status=live }}</ref>

In 2013, chemist and synthetic biologist [[Steven A. Benner|Steve Benner]] suggested that the conditions on [[Mars]] three billion years ago were much more favorable to the stability of [[RNA]] and formation of oxygen-containing{{refn | group = note | The [[Atmosphere of earth|earth's atmosphere]] and [[paleoceanography|prehistoric oceans]] three billion years ago had [[Great oxidation event|much lower]] oxygen levels than Earth's modern climate.<ref name="Lyons 307–315">{{Cite journal |last1=Lyons |first1=Timothy W. |last2=Reinhard |first2= Christopher T. |last3= Planavsky |first3= Noah J. |date=February 2014 |title=The rise of oxygen in Earth's early ocean and atmosphere |journal=Nature |volume=506 |issue=7488 |pages=307–315 |doi= 10.1038/nature13068 |pmid=24553238 |bibcode=2014Natur.506..307L |s2cid=4443958 }}</ref><ref>{{cite journal |last1=Catling |first1=DC |last2=Zahnle |first2=KJ |title=The Archean atmosphere. |journal=Science Advances |date=February 2020 |volume=6 |issue=9 |pages=eaax1420 |doi=10.1126/sciadv.aax1420 |pmid=32133393 |pmc=7043912 |bibcode=2020SciA....6.1420C }}</ref>}} boron and [[Molybdenum#Biological role|molybdenum]] catalysts found in life. According to Benner's theory, primitive life, which is widely believed to have [[RNA world|originated from RNA]],<ref name="Neveu et al">{{cite journal | vauthors = Neveu M, Kim HJ, Benner SA | title = The "strong" RNA world hypothesis: fifty years old | journal = Astrobiology | volume = 13 | issue = 4 | pages = 391–403 | date = April 2013 | pmid = 23551238 | doi = 10.1089/ast.2012.0868 | quote = [The RNA world's existence] has broad support within the community today. | bibcode = 2013AsBio..13..391N }}</ref><ref>{{cite journal | vauthors = Copley SD, Smith E, Morowitz HJ | title = The origin of the RNA world: co-evolution of genes and metabolism | journal = Bioorganic Chemistry | volume = 35 | issue = 6 | pages = 430–443 | date = December 2007 | pmid = 17897696 | doi = 10.1016/j.bioorg.2007.08.001}}</ref> first formed on Mars before [[Panspermia|migrating to Earth]].<ref name="mars">{{cite news|url=https://www.newscientist.com/article/dn24120-primordial-broth-of-life-was-a-dry-martian-cupasoup.html|title=Primordial broth of life was a dry Martian cup-a-soup|work=New Scientist|date=29 August 2013|access-date=29 August 2013|archive-date=24 April 2015|archive-url=https://web.archive.org/web/20150424181341/http://www.newscientist.com/article/dn24120-primordial-broth-of-life-was-a-dry-martian-cupasoup.html|url-status=live}}</ref>

===In human health===
It is thought that boron plays several essential roles in animals, including humans, but the exact physiological role is poorly understood.<ref>{{cite web|url=http://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/bor_0040.shtml |title=Boron |access-date=18 September 2008 |publisher=PDRhealth |archive-url=https://web.archive.org/web/20071011101928/http://pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/bor_0040.shtml |archive-date=11 October 2007}}</ref><ref name="utrace">{{Cite journal |title=Ultratrace elements in nutrition: Current knowledge and speculation| first=Forrest H. |last=Nielsen |journal=The Journal of Trace Elements in Experimental Medicine |volume=11| issue=2–3 |pages=251–274| doi=10.1002/(SICI)1520-670X(1998)11:2/3<251::AID-JTRA15>3.0.CO;2-Q |date=1998}}</ref> [[Boron deficiency (medicine)|Boron deficiency]] has only been clearly established in [[livestock]];<ref>{{Cite journal |last1=Abdelnour |first1=Sameh A. |last2=Abd El-Hack |first2=Mohamed E. |last3=Swelum |first3=Ayman A. |last4=Perillo |first4=Antonella |last5=Losacco |first5=Caterina |date=December 2018 |title=The vital roles of boron in animal health and production: A comprehensive review |journal=Journal of Trace Elements in Medicine and Biology |volume=50 |pages=296–304 |doi=10.1016/j.jtemb.2018.07.018 |pmid=30262295 |bibcode=2018JTEMB..50..296A |issn=0946-672X}}</ref><ref>{{Cite journal |last1=Sobiech |first1=Przemysław |last2=Żarczyńska |first2=Katarzyna |last3=Milewska |first3=Wanda |last4=Kabu |first4=Mustafa |last5=Uyarlar |first5=Cangir Uyarlar |date=2015-04-01 |title=The role of boron in animal health |journal=Journal of Elementology |volume=20 |issue=2 |doi=10.5601/jelem.2014.19.3.706 |issn=1644-2296}}</ref> in humans, boron deficiency may affect [[bone mineral density]], though it has been noted that additional research on the effects of bone health is necessary.<ref>{{Cite web |date=June 9, 2022 |title=Boron |url=https://ods.od.nih.gov/factsheets/Boron-HealthProfessional/ |access-date=2024-09-03 |website=[[Office of Dietary Supplements]] |language=en}}</ref>

Boron is not classified as an essential human nutrient because research has not established a clear biological function for it.<ref name="pmid31639188">{{cite journal |vauthors=Nielsen FH, Eckhert CD |title=Boron |journal=Adv Nutr |volume=11 |issue=2 |pages=461–462 |date=March 2020 |pmid=31639188 |pmc=7442337 |doi=10.1093/advances/nmz110 |url=}}</ref><ref name="bhp">{{Cite web |title=Office of Dietary Supplements - Boron |website=ods.od.nih.gov |url=https://ods.od.nih.gov/factsheets/Boron-HealthProfessional/ |access-date=19 October 2023|archive-date=21 October 2023|archive-url=https://web.archive.org/web/20231021052152/https://ods.od.nih.gov/factsheets/Boron-HealthProfessional/|url-status=live}}</ref> The U.S. [[Food and Nutrition Board]] (FNB) found the existing data insufficient to derive a [[Recommended Dietary Allowance]] (RDA), [[Adequate Intake]] (AI), or [[Estimated Average Requirement]] (EAR) for boron and the U.S. [[Food and Drug Administration]] (FDA) has not established a daily value for boron for food and dietary supplement labeling purposes.<ref name="pmid31639188" /><ref name="bhp" /> While low boron status can be detrimental to health, probably increasing the risk of [[osteoporosis]], poor immune function, and cognitive decline, high boron levels are associated with cell damage and toxicity.<ref name="pmid29546541">{{cite journal |vauthors=Khaliq H, Juming Z, Ke-Mei P |date=November 2018 |title=The Physiological Role of Boron on Health |url= |journal=Biol Trace Elem Res |volume=186 |issue=1 |pages=31–51 |doi=10.1007/s12011-018-1284-3 |pmid=29546541 |bibcode=2018BTER..186...31K |s2cid=255445828}}</ref>

Still, studies suggest that boron may exert beneficial effects on reproduction and development, [[calcium metabolism]], [[Ossification|bone formation]], brain function, [[insulin]] and energy substrate metabolism, immunity, and [[steroid]] [[hormone]] (including [[estrogen]]) and [[vitamin D]] function, among other functions.<ref name="pmid26770156">{{cite journal |vauthors=Pizzorno L |title=Nothing Boring About Boron |journal=Integr Med (Encinitas) |volume=14 |issue=4 |pages=35–48 |date=August 2015 |pmid=26770156 |pmc=4712861}}</ref><ref name="bhp" /> A small human trial published in 1987 reported on postmenopausal women first made boron deficient and then repleted with 3&nbsp;mg/day. Boron supplementation markedly reduced urinary calcium excretion and elevated the serum concentrations of 17 beta-estradiol and testosterone.<ref>{{cite journal |vauthors=Nielsen FH, Hunt CD, Mullen LM, Hunt JR |year=1987 |title=Effect of dietary boron on mineral, estrogen, and testosterone metabolism in postmenopausal women |journal=FASEB J. |volume=1 |issue=5 |pages=394–7 |doi=10.1096/fasebj.1.5.3678698 |pmid=3678698 |s2cid=93497977 |doi-access=free}}</ref> Environmental boron appears to be [[inversely correlated]] with [[arthritis]].<ref>{{Kirk-Othmer |title=Boron, Elemental|doi=10.1002/0471238961.0215181510011419.a01.pub3|pp=4-5|last1=Jansen|first1=LH|display-authors=etal}}</ref>

The exact mechanism by which boron exerts its physiological effects is not fully understood, but may involve interactions with [[adenosine monophosphate]] (ADP) and [[S-Adenosyl methionine|''S''-adenosyl methionine]] (SAM-e), two compounds involved in important cellular functions. Furthermore, boron appears to inhibit cyclic [[Adenosine diphosphate ribose|ADP-ribose]], thereby affecting the release of calcium ions from the [[endoplasmic reticulum]] and affecting various biological processes.<ref name="pmid29546541" /> Some studies suggest that boron may reduce levels of [[inflammatory biomarker]]s.<ref name="pmid26770156" />  [[Congenital endothelial dystrophy type 2]], a rare form of [[corneal dystrophy (human)|corneal dystrophy]], is linked to mutations in [[SLC4A11]] gene that encodes a transporter reportedly regulating the intracellular concentration of boron.<ref>{{Cite journal |author=Vithana, En |author2=Morgan, P |author3=Sundaresan, P |author4=Ebenezer, Nd |author5=Tan, Dt |author6=Mohamed, Md |author7=Anand, S |author8=Khine, Ko |author9=Venkataraman, D |author10=Yong, Vh |author11=Salto-Tellez, M |author12=Venkatraman, A |author13=Guo, K |author14=Hemadevi, B |author15=Srinivasan, M |date=July 2006 |title=Mutations in sodium-borate cotransporter SLC4A11 cause recessive congenital hereditary endothelial dystrophy (CHED2) |journal=Nature Genetics |volume=38 |issue=7 |pages=755–7 |doi=10.1038/ng1824 |issn=1061-4036 |pmid=16767101 |s2cid=11112294 |author16=Prajna, V |author17=Khine, M |author18=Casey, Jr. |author19=Inglehearn, Cf |author20=Aung, T}}</ref>

In humans, boron is usually consumed with food that contains boron, such as fruits, [[Leaf vegetable|leafy vegetables]], and [[Nut (fruit)|nuts]].<ref name="pmid31639188"/> Foods that are particularly rich in boron include [[avocado]]s, dried fruits such as [[raisin]]s, [[peanut]]s, [[pecan]]s, [[prune]] juice, [[grape]] juice, [[wine]] and [[chocolate]] powder.<ref name="pmid26770156"/><ref name="pmid31639188"/> According to 2-day food records from the respondents to the [[National Health and Nutrition Examination Survey|Third National Health and Nutrition Examination Survey]] (NHANES III), adult dietary intake was recorded at 0.9 to 1.4&nbsp;mg/day.<ref name="nationalacademies">Boron. IN: [https://www.nap.edu/read/10026/chapter/15 Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Copper] {{Webarchive|url=https://web.archive.org/web/20170922174144/https://www.nap.edu/read/10026/chapter/15 |date=22 September 2017 }}. National Academy Press. 2001, pp. 510–521.</ref>

===Health issues and toxicity===
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Elemental boron, [[boron trioxide|boron oxide]], [[boric acid]], borates, and many [[organoboron chemistry|organoboron compounds]] are relatively nontoxic to humans and animals (with toxicity similar to that of table salt). The [[median lethal dose|LD<sub>50</sub>]] (dose at which there is 50% mortality) for animals is about 6&nbsp;g per kg of body weight. Substances with an LD<sub>50</sub> above 2&nbsp;g/kg are considered nontoxic. An intake of 4&nbsp;g/day of boric acid was reported without incident, but more than this is considered toxic in more than a few doses. Intakes of more than 0.5&nbsp;grams per day for 50 days cause minor digestive and other problems suggestive of toxicity.<ref>{{cite journal|doi=10.1023/A:1004276311956|date=1997|last1=Nielsen|first1=Forrest H.|journal=Plant and Soil|volume=193|issue=2|pages=199–208|title=Boron in human and animal nutrition|bibcode=1997PlSoi.193..199N |s2cid=12163109|url=https://naldc-legacy.nal.usda.gov/naldc/download.xhtml?id=45215&content=PDF|access-date=29 April 2018|archive-date=12 March 2020|archive-url=https://web.archive.org/web/20200312091734/https://naldc-legacy.nal.usda.gov/naldc/download.xhtml?id=45215&content=PDF|url-status=live}}</ref>

[[Boric acid]] is more toxic to insects than to mammals, and is routinely used as an insecticide.<ref name="Klotz 1994 1534–1536">{{Cite journal|title = Oral toxicity of boric acid and other boron compounds to immature cat fleas (Siphonaptera: Pulicidae)|first1 = J. H.|last1 = Klotz|journal = J. Econ. Entomol.|volume = 87|issue = 6|pages = 1534–1536|date = 1994|pmid = 7836612 |last2 = Moss |first2 = J. I. |last3 = Zhao |first3 = R. |last4 = Davis Jr. |first4 = L. R. |last5 = Patterson |first5 = R. S.|doi = 10.1093/jee/87.6.1534}}</ref> However, it has been used in [[Neutron capture therapy of cancer|neutron capture therapy]] alongside other boron compounds such as [[sodium borocaptate]] and [[boronophenylalanine]] with reported low toxicity levels.<ref>{{Cite journal |last1=Hughes |first1=Andrea Monti |last2=Hu |first2=Naonori |date=August 2023 |title=Optimizing Boron Neutron Capture Therapy (BNCT) to Treat Cancer: An Updated Review on the Latest Developments on Boron Compounds and Strategies |journal=Cancers |language=en |volume=15 |issue=16 |page=4091 |doi=10.3390/cancers15164091 |pmc=10452654 |pmid=37627119 |doi-access=free}}</ref>

The [[boranes]] (boron hydrogen compounds) and similar gaseous compounds are quite poisonous. As usual, boron is not an element that is intrinsically poisonous, but the toxicity of these compounds depends on structure (for another example of this phenomenon, see [[phosphine]]).<ref name="borates" /><ref name="boron" /> The boranes are also highly flammable and require special care when handling, some combinations of boranes and other compounds are highly explosive. Sodium borohydride presents a fire hazard owing to its reducing nature and the liberation of hydrogen on contact with acid. Boron halides are corrosive.<ref>{{cite web|url = http://www.inchem.org/documents/ehc/ehc/ehc204.htm|title = Environmental Health Criteria 204: Boron|date = 1998|publisher = the [[International Programme on Chemical Safety|IPCS]]|access-date = 5 May 2009|archive-date = 3 April 2019|archive-url = https://web.archive.org/web/20190403043829/http://www.inchem.org/documents/ehc/ehc/ehc204.htm|url-status = live}}</ref>

[[File:Boron toxicity (2313046082).jpg|thumb|left|Boron toxicity in rose leaves.]]
Boron is necessary for plant growth, but an excess of boron is toxic to plants, and occurs particularly in acidic soil.<ref name="Boron (B) and Chlorine (Cl) for Citrus Trees">{{cite web |last1=Zekri |first1=Mongi |last2=Obreza |first2=Tom |title=Boron (B) and Chlorine (Cl) for Citrus Trees |url=https://edis.ifas.ufl.edu/pdffiles/SS/SS61900.pdf |website=IFAS Extension |publisher=University of Florida |access-date=30 June 2017 |archive-date=9 September 2016 |archive-url=https://web.archive.org/web/20160909071409/http://edis.ifas.ufl.edu/pdffiles/SS/SS61900.pdf |url-status=live}}</ref><ref name="PeverillSparrow1999">{{cite book |author1=K. I. Peverill |author2=L. A. Sparrow |author3=Douglas J. Reuter |title=Soil Analysis: An Interpretation Manual |url=https://books.google.com/books?id=pWR1vUWbEhEC&pg=PA309 |year=1999 |publisher=Csiro Publishing |isbn=978-0-643-06376-1 |pages=309–311 |access-date=30 June 2017 |archive-date=12 March 2020 |archive-url=https://web.archive.org/web/20200312192335/https://books.google.com/books?id=pWR1vUWbEhEC&pg=PA309 |url-status=live}}</ref> It presents as a yellowing from the tip inwards of the oldest leaves and black spots in barley leaves, but it can be confused with other stresses such as magnesium deficiency in other plants.<ref name="Reynolds2001">{{cite book |author=M. P. Reynolds |title=Application of Physiology in Wheat Breeding |url=https://books.google.com/books?id=PJ1a3yfTgg4C&pg=PA225 |year=2001 |publisher=CIMMYT |isbn=978-970-648-077-4 |page=225 |access-date=30 June 2017 |archive-date=10 March 2020 |archive-url=https://web.archive.org/web/20200310194730/https://books.google.com/books?id=PJ1a3yfTgg4C&pg=PA225 |url-status=live}}</ref>