Editing Butylated hydroxytoluene

{{redirect|E321|the Italian electric locomotive|FS Class E.321}}
{{Chembox
| Watchedfields  = changed
| verifiedrevid  = 443492116
| ImageFile      = 2,6-bis(1,1-dimethylethyl)-4-methylphenol.svg
| ImageSize      = 160px
| ImageAlt       = Skeletal formula of butylated hydroxytoluene
| ImageFile1     = Butylated hydroxytoluene 3D ball.png
| ImageSize1     = 180
| ImageAlt1      = Ball-and-stick model of the butylated hydroxytoluene molecule
| PIN            = 2,6-Di-''tert''-butyl-4-methylphenol
| OtherNames     = {{ubl
 | 2,6-Di-''tert''-butyl-''p''-cresol
 | 2,6-DI-tert-butyl-4-methylphenol
 | 3,5-Di-''tert''-butyl-4-hydroxytoluene
 | 2,6 ditertiary-butyl-4-methyl phenol
 | DBPC
 | BHT
 | E321
 | AO-29
 | Avox BHT
 | Antioxidant 264
 | Additin RC 7110
 | Dibutylated hydroxytoluene
 | 4-Methyl-2,6-di-tert-butyl phenol
 | 3,5-(Dimethylethyl)-4-hydroxytoluene
 }}
| Section1       = {{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 13835296
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 1P9D0Z171K
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = D02413
| InChI = 1/C15H24O/c1-10-8-11(14(2,3)4)13(16)12(9-10)15(5,6)7/h8-9,16H,1-7H3
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 34247
| PubChem = 31404
| SMILES = CC(C)(C)c1cc(C)cc(c1O)C(C)(C)C
| InChIKey = NLZUEZXRPGMBCV-UHFFFAOYAU
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 146
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C15H24O/c1-10-8-11(14(2,3)4)13(16)12(9-10)15(5,6)7/h8-9,16H,1-7H3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = NLZUEZXRPGMBCV-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 128-37-0
| EINECS = 204-881-4
| RTECS = GO7875000
  }}
| Section2       = {{Chembox Properties
| C=15 | H=24 | O=1
| MolarMassUnit = g/mol
| Appearance = White to yellow powder
| Odor = Slight, [[phenol]]ic
| Density = 1.048 g/cm<sup>3</sup>
| Solubility = 1.1{{nbsp}}mg/L (20{{nbsp}}°C)<ref>{{cite web | author = KEMI Anställd [KEMI Staff] | date = 1994 | title =  Teknisk beskrivning av ämnet—2,6-Bis(tert-butyl)-4-metylfenol 1994 [Information on substances—2,6-Bis(tert-butyl)-4-methylphenol 1994] | language = sv,en | location = Sundyberg, SE | publisher = KEMI [Swedish Chemicals Agency] | url = http://apps.kemi.se/flodessok/floden/kemamne/BHT.htm | archive-url = https://web.archive.org/web/20110811153038/http://apps.kemi.se/flodessok/floden/kemamne/BHT.htm | archive-date = 11 August 2011 | access-date = 14 March 2020 | quote =  Vattenlöslighet: 1,1 mg/L (20 °C) [Water solubility: 1.1 mg/L (20&nbsp;°C)]}}{{better source needed|date = March 2020}}<!--ANY COMPENDIUM/DATABASE NOT CITING THE SOURCE OF THE DATA PRESENTED IS NOT, FROM A PHYSICOCHEMICAL PERSPECTIVE, RELIABLE. THERE ARE MANY WAYS TO DETERMINE PHYSICAL PARAMETERS, AND NOT ALL ARE CREATED EQUAL, AS EARLY WORK ON LFER, pKa AND ClogP PREDICTION, ETC., HAVE MADE CLEAR. THIS 1.1 mg/L RAISES THE QUESTION OF HOW DETERMINED.--></ref>
| MeltingPtC = 70
| MeltingPt_ref = <ref name=inchem>{{cite web|url=http://www.inchem.org/documents/icsc/icsc/eics0841.htm|title=ICSC 0841 - BUTYLATED HYDROXYTOLUENE|website=www.inchem.org|date = March 1999}}</ref>
| BoilingPtC = 265
| BoilingPt_ref =<ref name=inchem />
| pKa = 
| VaporPressure = 0.01{{nbsp}}mmHg (20{{nbsp}}°C)<ref name=PGCH />
| LogP = 5.32<ref name="chemsrc">{{cite web|url=https://www.chemsrc.com/en/cas/128-37-0_1067745.html|title=2,6-di-tert-butyl-4-methylphenol|website=www.chemsrc.com}}</ref>
  }}
| Section7       = {{Chembox Hazards
| ExternalSDS = <ref>{{cite web |url=http://ptcl.chem.ox.ac.uk/MSDS/DI/2,6-di-t-butyl-p-cresol.html |title=Safety data for 2,6-di-tert-butyl-p-cresol |website=ptcl.chem.ox.ac.uk |access-date=17 January 2022 |archive-url=https://web.archive.org/web/20020621043339/http://ptcl.chem.ox.ac.uk/MSDS/DI/2,6-di-t-butyl-p-cresol.html |archive-date=21 June 2002 }}</ref>
| NFPA-H = 2 | NFPA-F = 1 | NFPA-R = 0 | NFPA-S =
| MainHazards = Flammable
| FlashPtC = 127
| FlashPt_ref = <ref name=inchem />
| GHSPictograms = {{GHS09}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|410}}
| PPhrases = {{P-phrases|273|391|501}}
| PEL = None<ref name=PGCH>{{PGCH|0246}}</ref>
| IDLH = N.D.<ref name=PGCH />
| REL = TWA 10{{nbsp}}mg/m<sup>3</sup><ref name=PGCH />
| LD50 = > 2,000{{nbsp}}mg/kg (dermal, rat)<ref name=GESTIS>{{GESTIS|ZVG=14260}}</ref>
  }}
| Section8       = {{Chembox Related
| OtherCompounds = [[Butylated hydroxyanisole]]
  }}
}}

'''Butylated hydroxytoluene''' ('''BHT'''), also known as '''dibutylhydroxytoluene''', is a [[lipophilic]] [[organic compound]], chemically a derivative of [[phenol]], that is useful for its [[antioxidant]] properties.<ref>{{cite journal |vauthors=Yehye WA, Rahman NA, Ariffin A, Abd Hamid SB, Alhadi AA, Kadir FA, Yaeghoobi M | date = 28 August 2015 | title = Understanding the Chemistry Behind the Antioxidant Activities of Butylated Hydroxytoluene (BHT): A Review | journal = Eur. J. Med. Chem. | volume = 101 | pages = 295–312 | doi = 10.1016/j.ejmech.2015.06.026 | pmid = 26150290 }}</ref> BHT is widely used to prevent [[free radical]]-mediated [[oxidation]] in fluids (e.g. fuels, oils) and other materials, and the regulations overseen by the [[United States Food and Drug Administration|U.S. F.D.A.]]—which considers BHT to be "[[generally recognized as safe]]"—allow small amounts to be [[food additive|added to foods]]. Despite this, and the earlier determination by the [[National Cancer Institute]] that BHT was noncarcinogenic in an animal model, societal concerns over its broad use have been expressed. 

== Natural occurrence ==
[[Phytoplankton]], including the [[green algae]] ''[[Botryococcus braunii]]'', as well as three different [[cyanobacteria]] (''[[Cylindrospermopsis raciborskii]]'', ''[[Microcystis aeruginosa]]'' and ''[[Oscillatoria]]'' sp.) are capable of producing BHT as a [[natural product]].<ref name="BHTalgae">{{cite journal |vauthors=Babu B, Wu JT |title=Production of Natural Butylated Hydroxytoluene as an Antioxidant by Freshwater Phytoplankton |journal=Journal of Phycology |volume=44 |issue=6 |pages=1447–1454 |date=December 2008 |url= http://ntur.lib.ntu.edu.tw/bitstream/246246/162863/1/22.pdf |doi=10.1111/j.1529-8817.2008.00596.x|pmid=27039859 |bibcode=2008JPcgy..44.1447B |s2cid=26084768 }}</ref> The fruit [[lychee]] also produces BHT in its [[pericarp]].<!-- For this to appear, it needs to be clear which of the preceding sets of isolations this detail applies to: Confirmation was made via  [[gas chromatography–mass spectrometry]] analysis.--><ref>{{cite journal |last1=Jiang |first1=G |last2=Lin |first2=S |last3=Wen |first3=L |last4=Jiang |first4=Y |last5=Zhao |first5=M |last6=Chen |first6=F |last7=Prasad |first7=KN |last8=Duan |first8=X |last9=Yang |first9=B |title=Identification of a novel phenolic compound in litchi (Litchi chinensis Sonn.) pericarp and bioactivity evaluation. |journal=Food Chemistry |date=15 January 2013 |volume=136 |issue=2 |pages=563–8 |name-list-style=vanc |doi=10.1016/j.foodchem.2012.08.089 |pmid=23122098}}</ref>

Several fungi (for example ''[[Aspergillus conicus]]'') living in olives produce BHT. [[Volatile organic compound]]s such as BHT and odor chemicals are produced by resident fungi when olives are being stored awaiting pressing.<ref>{{cite journal|title = Butylated hydroxytoluene (BHT) emitted by fungi naturally occurring in olives during their pre-processing storage for improving olive oil stability|first1= Ines|last1= Gharbi|first2= Manel|last2= Issaoui|first3=Sinda|last3= El Gharbi|first4 =Nour-Eddine |last4=Gazzeh|first5= Meriem|last5= Tekeya|first6 =Beligh|last6 = Mechri|first7= Guido|last7= Flamini|first8 =Mohamed |last8=Hammami|journal = European Journal of Lipid Science and Technology |volume = 119|issue = 11|date = 2017|page= 1600343|doi = 10.1002/ejlt.201600343}}</ref>

It has been detected in higher plants and herbivorous insects, but it is not clear whether the BHT is produced by the plant, the insect, or some other organism living in association.<ref>{{cite journal |last1=Zhao |first1=F |last2=Wang |first2=P |last3=Lucardi |first3=RD |last4=Su |first4=Z |last5=Li |first5=S |title=Natural Sources and Bioactivities of 2,4-Di-Tert-Butylphenol and Its Analogs. |journal=Toxins |date=6 January 2020 |volume=12 |issue=1 |page=35 |doi=10.3390/toxins12010035 |doi-access=free |pmid=31935944}}</ref>

== Production ==
===Industrial production===
The [[chemical synthesis]] of BHT in industry has involved the reaction of [[p-Cresol|''p''-cresol]] (4-methylphenol) with [[isobutylene]] (2-methylpropene), catalyzed by [[sulfuric acid]]:
<ref name=Ullmann>Helmut Fiege, Heinz-Werner Voges, Toshikazu Hamamoto, Sumio Umemura, Tadao Iwata, Hisaya Miki, Yasuhiro Fujita, Hans-Josef Buysch, Dorothea Garbe, Wilfried Paulus "Phenol Derivatives" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim, 2002. {{doi|10.1002/14356007.a19_313}}
Article Online Posting Date: June 15, 2000.</ref>
:CH<sub>3</sub>(C<sub>6</sub>H<sub>4</sub>)OH  +  2 CH<sub>2</sub>=C(CH<sub>3</sub>)<sub>2</sub>  →  ((CH<sub>3</sub>)<sub>3</sub>C)<sub>2</sub>CH<sub>3</sub>C<sub>6</sub>H<sub>2</sub>OH
Alternatively, BHT has been prepared from [[2,6-Di-tert-butylphenol|2,6-di-''tert''-butylphenol]] by hydroxymethylation or aminomethylation followed by [[hydrogenolysis]].{{citation needed|date = March 2020}}

== Reactions ==
The species behaves as a synthetic [[structural analog|analog]] of [[vitamin E]], primarily acting as a terminating agent that suppresses [[autoxidation]], a process whereby unsaturated (usually) organic compounds are attacked by atmospheric oxygen.  BHT stops this [[autocatalytic]] reaction by converting peroxy radicals to hydroperoxides.  It effects this function by donating a hydrogen atom:
:RO<sub>2</sub>•  +  ArOH  →  ROOH  +  ArO•
:RO<sub>2</sub>•  +  ArO•  →  nonradical products
where R is [[alkyl]] or [[aryl]], and where ArOH is BHT or related phenolic antioxidants.  Each BHT consumes two peroxy radicals.<ref>{{cite journal | author = Burton G. W., Ingold K. U. | year = 1981 | title = Autoxidation of biological molecules. 1. Antioxidant activity of vitamin E and related chain-breaking phenolic antioxidants in vitro | journal = Journal of the American Chemical Society | volume = 103 | issue = 21| pages = 6472–6477 | doi = 10.1021/ja00411a035 | bibcode = 1981JAChS.103.6472B }}</ref><ref>{{Cite journal |last1=Fujisawa |first1=Seiichiro |last2=Kadoma |first2=Yoshinori |last3=Yokoe |first3=Ichiro |date=July 2004 |title=Radical-scavenging activity of butylated hydroxytoluene (BHT) and its metabolites |url=https://linkinghub.elsevier.com/retrieve/pii/S0009308404000349 |journal=Chemistry and Physics of Lipids |language=en |volume=130 |issue=2 |pages=189–195 |doi=10.1016/j.chemphyslip.2004.03.005|pmid=15172835 }}</ref> The electron-donating alkyl groups on the ''ortho'' and ''para'' positions of BHT increase the electron density of the phenolic hydroxyl moiety through the inductive effect and the hyperconjugation effect,<ref name=":1">{{Cite book |url=https://pubs.acs.org/doi/abs/10.1021/bk-1992-0507.ch015 |title=Phenolic Compounds in Food and Their Effects on Health II: Antioxidants and Cancer Prevention |chapter=Thermal Degradation of Phenolic Antioxidants |date=1992-10-01 |publisher=American Chemical Society |isbn=978-0-8412-2476-6 |editor-last=Huang |editor-first=Mou-Tuan |series=ACS Symposium Series |volume=507 |pages=200–218 |location=Washington, DC |language=en |doi=10.1021/bk-1992-0507.ch015 |editor-last2=Ho |editor-first2=Chi-Tang |editor-last3=Lee |editor-first3=Chang Y.}}</ref> reduce the bond dissociation energy of the phenolic hydroxyl group, and enhance its reactivity to lipid free radicals. Meanwhile, the phenoxy radical generated by BHT is stabilized due to the delocalization of unpaired electrons around the aromatic ring<ref name=":1" /><ref>{{Cite journal |last1=Shahidi |first1=Fereidoon |last2=Janitha |first2=P. K. |last3=Wanasundara |first3=P. D. |date=1992 |title=Phenolic antioxidants |url=https://www.tandfonline.com/doi/abs/10.1080/10408399209527581 |journal=Critical Reviews in Food Science and Nutrition |language=en |volume=32 |issue=1 |pages=67–103 |doi=10.1080/10408399209527581 |pmid=1290586 |issn=1040-8398}}</ref> and the steric hindrance effect of ortho ''tert''-butyl groups.<ref>{{Cite journal |last1=Breese |first1=K.D. |last2=Lamèthe |first2=J.-F. |last3=DeArmitt |first3=C. |date=2000 |title=Improving synthetic hindered phenol antioxidants: learning from vitamin E |url=https://linkinghub.elsevier.com/retrieve/pii/S014139100000094X |journal=Polymer Degradation and Stability |language=en |volume=70 |issue=1 |pages=89–96 |doi=10.1016/S0141-3910(00)00094-X}}</ref><ref>{{Cite journal |last1=Ariffin |first1=Azhar |last2=Rahman |first2=Noorsaadah Abdul |last3=Yehye |first3=Wageeh A. |last4=Alhadi |first4=Abeer A. |last5=Kadir |first5=Farkaad A. |date=2014 |title=PASS-assisted design, synthesis and antioxidant evaluation of new butylated hydroxytoluene derivatives |url=https://linkinghub.elsevier.com/retrieve/pii/S0223523414009271 |journal=European Journal of Medicinal Chemistry |language=en |volume=87 |pages=564–577 |doi=10.1016/j.ejmech.2014.10.001|pmid=25299680 }}</ref> Isobutene is one of the possible degradation products formed by BHT oxidation with computational studies suggesting that there are two possible mechanism that can lead to isobutene formation with the OH addition pathways at the C2 site of BHT more likely to result in isobutene formation than pathways of H abstracts from the ''t''-butyl group.<ref>{{Cite journal |last1=Zhou |first1=Junwei |last2=Chen |first2=Hongrui |last3=Chen |first3=Jianfa |last4=Wan |first4=Daihong |last5=Zhang |first5=Huikun |last6=Wang |first6=Rong |last7=Xie |first7=Daiqian |last8=Mao |first8=Chengli |date=2022-05-26 |title=Mechanisms and Kinetics Studies of Butylated Hydroxytoluene Degradation to Isobutene |url=https://pubs.acs.org/doi/10.1021/acs.jpca.2c01961 |journal=The Journal of Physical Chemistry A |language=en |volume=126 |issue=20 |pages=3210–3218 |doi=10.1021/acs.jpca.2c01961 |pmid=35549278 |bibcode=2022JPCA..126.3210Z |issn=1089-5639}}</ref>

== Applications ==
BHT is listed by the [[NIH]] Hazardous Substances Data Bank under several categories in catalogues and databases, such as food additive, household product ingredient, industrial additive, personal care product/cosmetic ingredient, pesticide ingredient, plastic/rubber ingredient and medical/veterinary/research.<ref>US Dept of Health & Human Services. Household Products Database. [http://hpd.nlm.nih.gov/] {{Webarchive|url=https://web.archive.org/web/20150905052301/http://hpd.nlm.nih.gov/|date=2015-09-05}}.US EPA. InertFinder. [http://iaspub.epa.gov/apex/pesticides/f?p=175:1:]. US National Library of Medicine. Haz-Map. [http://hazmap.nlm.nih.gov/index.php] {{Webarchive|url=https://web.archive.org/web/20150905065151/http://hazmap.nlm.nih.gov/index.php|date=2015-09-05}}. US National Library of Medicine. Hazardous Substances Data Bank. [http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?HSDB].</ref>

=== Food additive ===
BHT is primarily used as an antioxidant food additive.<ref>{{Cite web|url=https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=172.115|title=CFR - Code of Federal Regulations Title 21}}</ref> In the United States, it is classified as [[generally recognized as safe]] (GRAS) based on a [[National Cancer Institute]] study from 1979 in rats and mice.<ref name=NTP>[https://ntp.niehs.nih.gov/go/tr150abs Bioassay of Butylated Hydroxytoluene (BHT) for Possible Carcinogenicity], National Cancer Institute, CARCINOGENESIS Technical Report Series No. 150, 1979, 128 pp  [[National Institutes of Health]]{{page needed|date=March 2020}}</ref><ref>{{Cite web |title=Abstract for TR-150 |url=https://ntp.niehs.nih.gov/publications/reports/tr/tr150 |access-date=2025-03-27 |website=National Toxicology Program |language=en}}</ref> It is approved for use in the U.S. by the [[Food and Drug Administration]]: For example, 21 [[Code of Federal Regulations|CFR]] §&nbsp;137.350(a)(4) allows BHT up to 0.0033% by weight in "enriched rice",<ref>{{cite web|url=https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=137.350|title=CFR - Code of Federal Regulations Title 21|website=www.accessdata.fda.gov}}</ref> while 9 CFR §&nbsp;381.147](f)(1) allows up to 0.01% in [[poultry]] "by fat content".<ref>{{Cite web |url=https://www.fda.gov/Food/FoodSafety/RetailFoodProtection/FoodCode/FoodCode2001/ucm092716.htm |title=9 CFR 3, Part 381.147 (Restrictions on the Use of Substances in Poultry Processing) |website=[[Food and Drug Administration]] |access-date=2019-12-16 |archive-url=https://web.archive.org/web/20090709085417/http://www.fda.gov/Food/FoodSafety/RetailFoodProtection/FoodCode/FoodCode2001/ucm092716.htm |archive-date=2009-07-09 }}</ref> It is permitted in the European Union under [[E number|E321]].<ref>{{cite web|title = Scientific Opinion on the re-evaluation of butylated hydroxytoluene BHT (E 321) as a food additive {{!}} European Food Safety Authority|url = http://www.efsa.europa.eu/en/efsajournal/pub/2588|website = www.efsa.europa.eu|access-date = 4 October 2015 |date = 7 March 2012}}</ref>

BHT is used as a preservative ingredient in some foods. With this usage BHT maintains freshness or prevents spoilage; it may be used to decrease the rate at which the texture, color, or flavor of food changes.<ref>{{cite web |url=https://www.fda.gov/food/ingredientspackaginglabeling/foodadditivesingredients/ucm094211.htm#types |title=Food Additives & Ingredients > Overview of Food Ingredients, Additives & Colors |quote=Types of Ingredients: Preservatives[.] What They Do: Prevent food spoilage from [...]; maintain freshness[.] Examples of Uses: Fruit sauces and jellies, beverages, baked goods, cured meats, oils and margarines, cereals, dressings, snack foods, fruits and vegetables[.] Names Found on Product Labels: Ascorbic acid, citric acid, sodium benzoate, calcium propionate, sodium erythorbate, sodium nitrite, calcium sorbate, potassium sorbate, BHA, BHT, EDTA, tocopherols (Vitamin E)[.] |website=www.fda.gov|date=20 February 2020 }}</ref>

Some food companies have voluntarily eliminated BHT from their products or have announced that they were going to phase it out.<ref name=atl>{{cite journal|author=Hamblin, James|title=The Food Babe: Enemy of Chemicals|journal=The Atlantic|date=11 February 2015|url=https://www.theatlantic.com/health/archive/2015/02/the-food-babe-enemy-of-chemicals/385301/|access-date=12 September 2015}}</ref>

=== Antioxidant ===
BHT is also used as an antioxidant in products such as [[metalworking fluids]], [[cosmetics]], [[pharmaceuticals]], [[rubber]], [[transformer oil]]s, and [[embalming]] fluid.<ref name=":0">{{Cite journal |last1=Yehye |first1=Wageeh A. |last2=Rahman |first2=Noorsaadah Abdul |last3=Ariffin |first3=Azhar |last4=Abd Hamid |first4=Sharifah Bee |last5=Alhadi |first5=Abeer A. |last6= Kadir |first6=Farkaad A. |last7=Yaeghoobi |first7=Marzieh |date=2015-08-28 |title=Understanding the chemistry behind the antioxidant activities of butylated hydroxytoluene (BHT): a review |url= https://pubmed.ncbi.nlm.nih.gov/26150290/ |journal=European Journal of Medicinal Chemistry |volume=101 |pages=295–312 |doi=10.1016/j.ejmech.2015.06.026 |issn=1768-3254 |pmid=26150290}}</ref><ref>{{Cite web |last=PubChem |title=Butylated Hydroxytoluene |url=https://pubchem.ncbi.nlm.nih.gov/compound/31404 |access-date=2023-09-01 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref> In the [[petroleum industry]], where BHT is known as the [[List of gasoline additives|fuel additive]] [[Antioxidant#Industrial uses|AO-29]] (Innospec), it is used in [[hydraulic fluid]]s, [[turbine]] and [[gear]] oils, and [[jet fuel]]s.<ref name=":0" /><ref>{{Cite book |title=Handbook of preservatives |date=2009 |publisher=Synapse Information Resources |isbn=978-1-890595-66-1 |editor-last=Ash |editor-first=Michael |location=Endicott, NY |page=628 |editor-last2=Ash |editor-first2=Irene}}</ref> BHT is also used to prevent [[Organic peroxide|peroxide]] formation in organic [[ether]]s and other solvents and laboratory chemicals.<ref>{{Cite web|url=https://www.sigmaaldrich.com/chemistry/solvents/learning-center/stabilizer-systems.html|title=Solvents|website = Millipore Sigma}}</ref> It is added to certain [[monomers]] as a [[polymerisation inhibitor]] to facilitate their safe storage.<ref>{{Cite journal |last1=Grohmann |first1=Caio Vinícius Signorelli |last2=Sinhoreti |first2=Mário Alexandre Coelho |last3=Soares |first3=Eveline Freitas |last4=Oliveira |first4=Robson Ferraz de |last5=Souza |first5=Eduardo José de Carvalho |last6=Geraldeli |first6=Saulo |date=24 June 2022 |title=Effect of a polymerization inhibitor on the chemomechanical properties and consistency of experimental resin compo |journal=Brazilian Dental Journal |volume=33 |issue=3 |pages=92–98 |doi=10.1590/0103-6440202204242 |pmid=35766722 |pmc=9645198 }}</ref> Some additive products contain BHT as their primary ingredient, while others contain the chemical merely as a component of their formulation, sometimes alongside [[butylated hydroxyanisole]] (BHA).<ref name="sciam13">{{cite news |title=BHA and BHT: A Case for Fresh? |url=https://www.scientificamerican.com/article/bha-and-bht-a-case-for-fresh/ |publisher=Scientific American |date=19 December 2013}}</ref>

=== Cosmetics ===
The European Union restricts the use of BHT in mouthwash to 0.001% concentration, in toothpaste to 0.01% concentration, and to 0.8% in other cosmetics.<ref>{{cite web |last1=Slavova |first1=Siana |title=New restrictions for Butylated Hydroxytoluene (BHT) and Acid Yellow 3 apply as of July 2023 |url=https://www.obelis.net/news/new-restrictions-bht-acid-yellow-3-cosmetic-products/ |website=Obelis Group |language=en |date=23 June 2023}}</ref>

== Health effects ==
Like many closely related [[phenol antioxidant]]s, BHT has low acute toxicity<ref name=GESTIS/> (e.g., the [[desmethyl]] analog of BHT, [[2,6-di-tert-butylphenol]], has an {{LD50}} of >9&nbsp;g/kg<ref name=Ullmann />). The [[US Food and Drug Administration]] classifies BHT as [[generally recognized as safe]] (GRAS) food preservative when used in an approved manner.<ref>{{cite web|url=https://www.accessdata.fda.gov/scripts/fdcc/?set=SCOGS|title=SCOGS (Select Committee on GRAS Substances)|work=FDA.gov}}</ref><ref>{{cite web|url=https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm?fr=172.115|title=CFR—Code of Federal Regulations Title 21|work=FDA.gov}}</ref> In 1979, the [[National Cancer Institute]] determined that BHT was noncarcinogenic in a [[mouse model]].<ref name=NTP />

The [[World Health Organization]] discussed a possible link between BHT and cancer risk in a 1986 report concluding there is limited evidence for carcinogenicity from animal studies.<ref name="WHOReport1986">{{cite report |url=https://monographs.iarc.fr/ENG/Monographs/vol1-42/mono40.pdf |title=Butylated hydroxytoluene (BHT) |date=1986 |publisher=World Health Organization: International Agency For Research On Cancer |volume=40 |page=191 |pages= |archive-url=https://web.archive.org/web/20150905203436/http://monographs.iarc.fr/ENG/Monographs/vol1-42/mono40.pdf |archive-date=5 September 2015 |url-status=live}}{{page needed|date=March 2020}}</ref> Primary research studies in the 1970s–1990s reported both potential for increased risk and potential for decreased risk in the area of oncology.<ref name=":2">{{Cite journal |date=2002 |title=Final Report on the Safety Assessment of BHT |url=https://journals.sagepub.com/doi/10.1080/10915810290096513 |journal=International Journal of Toxicology |language=en |volume=21 |issue=2_suppl |pages=19–94 |doi=10.1080/10915810290096513 |issn=1091-5818}}</ref> A review report published in 2002 noted that BHT has shown anticarcinogenic effects, no effect, or tumor promoting effects depending on animal species and target organ considered.<ref name=":2" /> Because of this uncertainty, the [[Center for Science in the Public Interest]] puts BHT in its "caution" column and recommends avoiding it.<ref name="ucb">{{cite web |date=February 1, 2011 |title=Two Preservatives to Avoid? |url=http://www.berkeleywellness.com/healthy-eating/food-safety/article/two-preservatives-avoid |access-date=12 September 2015 |website=Berkeley Wellness |publisher=University of California Berkeley}}</ref>

== References ==
{{reflist}}

== External links ==
* [https://www.thoughtco.com/bha-and-bht-food-preservatives-607393 Chemistry of BHA and BHT Food Preservatives]
* [https://www.cdc.gov/niosh/npg/npgd0246.html CDC – NIOSH Pocket Guide to Chemical Hazards]

{{Motor fuel}}
{{Antioxidants}}

[[Category:Natural phenols]]
[[Category:Antioxidants]]
[[Category:Alkylphenols]]
[[Category:Fuel antioxidants]]
[[Category:Food antioxidants]]
[[Category:Tert-butyl compounds]]
[[Category:E-number additives]]