View source for Coal tar

{{Short description|Chemical mixture}}
{{about|the substance|the book|Coal Tar: How Corrupt Politics and Corporate Greed Are Killing America's Children}}
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{{Use dmy dates|date=September 2025}}
{{Use American English|date=September 2025}}

{{Infobox drug
| drug_name         =
| INN               =
| type              =<!-- empty -->
| IUPAC_name        = 
| image             =
| alt               = 
| caption           = An old advertisement for soap containing coal tar
<!-- Clinical data -->
| synonyms          =liquor carbonis detergens (LCD)<br />liquor picis carbonis (LPC)<ref name="Berenblum_1948">{{cite journal | vauthors = Berenblum I | title = Liquor picis carbonis; a carcinogenic agent | journal = British Medical Journal | volume = 2 | issue = 4577 | pages = 601 | date = September 1948 | pmid = 18882998 | pmc = 2091540 | doi = 10.1136/bmj.2.4577.601 }}</ref>
| pronounce         =
| tradename         = Balnetar, Cutar, others
| Drugs.com         = {{Drugs.com|mtm|coal-tar-topical}}
| MedlinePlus       = 
| pregnancy_AU      = <!-- A/B1/B2/B3/C/D/X -->
| pregnancy_AU_comment = 
| pregnancy_US      = C
| pregnancy_category= 
| routes_of_administration = Topical
| legal_AU = <!-- S2, S3, S4, S5, S6, S7, S8, S9 or Unscheduled-->
| legal_AU_comment =
| legal_CA = <!-- OTC, Rx-only, Schedule I, II, III, IV, V, VI, VII, VIII -->
| legal_DE = <!-- Anlage I, II, III -->
| legal_NZ = <!-- Class A, B, C -->
| legal_UK = <!-- GSL, P, POM, CD, CD Lic, CD POM, CD No Reg POM, CD (Benz) POM, CD (Anab) POM or CD Inv POM / Class A, B, C -->
| legal_US = OTC
| legal_US_comment = /&nbsp;Rx-only
| legal_UN = <!-- N I, II, III, IV / P I, II, III, IV-->
| legal_status      = 
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| bioavailability   = 
| protein_bound     = 
| metabolism        = 
| metabolites       =
| onset             = 
| elimination_half-life = 
| duration_of_action =
| excretion         = 
<!-- Identifiers -->
| CAS_number        = 8007-45-2
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = R533ESO2EC
| class             = 
| ATCvet            = 
| ATC_prefix        = D05
| ATC_suffix        = AA
| PubChem           = 
| DrugBank          = 
| ChemSpiderID      = none
<!-- Chemical and physical data -->
| chemical_formula  = 
| molecular_weight  = 
}}
<!-- Definition and medical uses -->
'''Coal tar''' (also '''creosote''') is a thick dark liquid that is a [[by-product]] of deriving [[coke (fuel)|coke]] and [[coal gas]] from [[coal]].<ref name="cdc24">{{cite web | title = ToxFAQs for Creosote | date = 8 July 2024 | url = https://wwwn.cdc.gov/TSP/ToxFAQs/ToxFAQsDetails.aspx?faqid=65&toxid=18 | publisher = US Centers for Disease Control and Prevention | access-date = 21 September 2025 }}</ref><ref>{{cite book | vauthors = Vallee Y | title = Gas Phase Reactions in Organic Synthesis | pages = 107 | date = 1998 | publisher = CRC Press | isbn = 978-90-5699-081-7 | url = https://books.google.com/books?id=lfBC9hj9iH8C&pg=PA107 | language = en }}</ref> Coal tar has both medical and industrial uses.<ref name="cdc24" /><ref name="aad25">{{cite web | title = Psoriasis treatment: Coal tar | date = 2025 | url = https://www.aad.org/public/diseases/psoriasis/treatment/medications/coal-tar | publisher = American Association of Dermatology | access-date = 21 September 2025 }}</ref><ref name="Chat_2022">{{cite journal | vauthors = Chat VS, Kearns DG, Uppal SK, Han G, Wu JJ | title = Management of Psoriasis With Topicals: Applying the 2020 AAD-NPF Guidelines of Care to Clinical Practice | journal = Cutis | volume = 110 | issue = 2 Suppl | pages = 8–14 | date = August 2022 | pmid = 36219602 | doi = 10.12788/cutis.0573 | url = https://www.mdedge.com/dermatology/article/256943/psoriasis/management-psoriasis-topicals-applying-2020-aad-npf-guidelines }}</ref> Medicinally, it is a [[topical medication]] applied to [[Human skin|skin]] to treat [[psoriasis]] and [[seborrheic dermatitis]] ([[dandruff]]).<ref name="aad25" /><ref name="Chat_2022" /><ref name=WHO2008>{{cite book | veditors = Stuart MC, Kouimtzi M, Hill SR | title = WHO Model Formulary 2008 | pages = 306–308 | year = 2009 | isbn = 978-92-4-154765-9 | hdl = 10665/44053 | author-link = World Health Organization | publisher = World Health Organization | url = https://iris.who.int/bitstream/10665/44053/1/9789241547659_eng.pdf }}</ref>  It may be used in combination with [[ultraviolet light therapy]] in a treatment called ''[[Goeckerman therapy]]'', which is rarely used clinically, as of 2024.<ref name="Lie_2024">{{cite journal | vauthors = Lie E, Choi M, Wang SP, Eichenfield LF | title = Topical Management of Pediatric Psoriasis: A Review of New Developments and Existing Therapies | journal = Paediatric Drugs | volume = 26 | issue = 1 | pages = 9–18 | date = January 2024 | pmid = 37847480 | pmc = 10769900 | doi = 10.1007/s40272-023-00592-9 }}</ref>

Industrially, it is a [[railroad tie]] preservative used in the surfacing of roads.<ref name="Hornbostel_1991" /> Coal tar was listed as a known human [[carcinogen]] in the first [[National Toxicology Program#Office of the Report on Carcinogens|Report on Carcinogens]] from the U.S. Federal Government, issued in 1980,<ref name=ROC1980>{{cite book | title = First Annual Report on Carcinogens | year = 1980 | url = https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/PB84122852.xhtml | publisher = National Technical Reports Library }}</ref> and remains a cancer concern due to the presence of [[Benzene#Health effects|benzene]] in coal tar skincare products, such as [[shampoo]]s.<ref name="aad25" /><ref name="Chat_2022" /><ref name="nci">{{cite web | title = Coal tar and coal-tar pitch | date = 2025 | url = https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/coal-tar | publisher = US National Cancer Institute | access-date = 21 September 2025 }}</ref>

==History==
Coal tar was discovered circa 1665.<ref name="Hornbostel_1991">{{cite book | vauthors = Hornbostel C | title = Construction Materials: Types, Uses and Applications | pages = 864 | date = 1991 | publisher = John Wiley & Sons | isbn = 978-0-471-85145-5 | url = https://books.google.com/books?id=oaxKD0pEKxkC&pg=PA864 | language = en | url-status = live | archive-url = https://web.archive.org/web/20170918185259/https://books.google.com/books?id=oaxKD0pEKxkC&pg=PA864 | archive-date = 2017-09-18 }}</ref> Much later, it was an undesirable byproduct in the production of [[coke (fuel)|coke]] and illumination gases ("town gas").  Soon it was found that the tar could be a source of solvents.<ref>{{cite book | vauthors = Blümer GP, Collin G, Höke H | chapter = Tar and Pitch | title = Ullmann's Encyclopedia of Industrial Chemistry | date = 2011 | doi = 10.1002/14356007.a26_091.pub2 | isbn = 978-3-527-30673-2 }}</ref>  Around 1850, it was discovered that it could be used as a source of many organic compounds. Its use as a precursor to [[dye]]s engendered an entire industry.<ref name="bayereh">{{cite news | title = History The Early Years (1863–1881) | url = https://www.bayer.com/en/history/1863-1881 | access-date = 4 February 2021 | publisher = Bayer AG }}</ref> 
In 1854 [[Frederick Crace Calvert]], "an eminent English chemist," made the extraordinary statement before the Society of Arts that ere long, some valuable dyeing substances would be prepared from coal."<ref>{{cite web | title = Dyes from Coal Tar Products | date = February 20, 2024 | website = Scientific American | url = https://www.scientificamerican.com/article/dyes-from-coal-tar-products/ | access-date = July 9, 2025 }}</ref> Coal tar was used for medical purposes as early as the 1800s.<ref>{{cite book | vauthors = Sneader W | title = Drug Discovery: A History | pages = 356 | date = 2005 | publisher = John Wiley & Sons | isbn = 978-0-471-89979-2 | url = https://books.google.com/books?id=Cb6BOkj9fK4C&pg=PA356 | language = en | url-status = live | archive-url = https://web.archive.org/web/20170918185259/https://books.google.com/books?id=Cb6BOkj9fK4C&pg=PA356 | archive-date = 2017-09-18 }}</ref>

== Composition ==
Coal tar is produced through thermal destruction ([[pyrolysis]]) of [[coal]]. Its composition varies with the process and type of coal used &ndash; [[lignite]], [[bituminous coal|bituminous]] or [[anthracite]].<ref name="Roberts_2014">{{Cite book | vauthors = Roberts L | veditors = Wexler P | chapter = Coal Tar | title = Encyclopedia of Toxicology | location = Oxford | pages = 993–995 | date = 2014 | doi = 10.1016/b978-0-12-386454-3.00012-9 | publisher = Academic Press | isbn = 978-0-12-386455-0 | quote = composition of coal tar will be influenced by the process used for pyrolytic distillation as well as by the original composition of the coal ... He then demonstrated excess cancers occurring in laboratory animals when coal tar is applied to the ears and skin ... [therapeutic effect] is thought to involve decreased epidermal proliferation ... Coal tar is classified as a human carcinogen ... Both inhalation and dermal routes of exposure are considered hazardous. | edition = Third }}</ref>

Coal tar is a mixture of approximately 10,000 chemicals, of which only about 50% have been identified.<ref>{{Cite journal | vauthors = Heinz-Gerhard F | title = The Challenge in Coal Tar Chemicals | journal = Industrial & Engineering Chemistry | volume = 55 | issue = 5 | pages = 38–44 | date = May 1963 | doi = 10.1021/ie50641a006 }}</ref>{{Better source needed|reason=The source cited is over 50 years old and, as such, fails to incorporate research done in the field of chemistry in the last 50 years.|date=May 2015}} Most of the chemical compounds are [[polycyclic aromatic hydrocarbon]]:<ref>{{Cite book | title = Creosote. | location = US | date = 2002 | publisher = Agency for Toxic Substances Disease Registry, Division of Toxicology, Dept. of Health and Human Services, Public Health Service | language = en | oclc = 816079578 }}</ref><ref>{{Cite web | title = Public Health Statement for Creosote | date = September 2002 | url = https://wwwn.cdc.gov/TSP/PHS/PHS.aspx?phsid=64&toxid=18 | publisher = Agency for Toxic Substances and Disease Registry }}</ref>

* polycyclic aromatic hydrocarbons (4-rings: [[chrysene]], [[fluoranthene]], [[pyrene]], [[triphenylene]], [[naphthacene]], [[benzanthracene]], 5-rings: [[picene]], [[Benzo(a)pyrene|benzo[a]pyrene]], [[Benzo(e)pyrene|benzo[e]pyrene]], [[benzofluoranthene]]s, [[perylene]], 6-rings: [[dibenzopyrenes]], dibenzofluoranthenes, [[benzoperylene]]s, 7-rings: [[coronene]])
* methylated and polymethylated derivatives, mono- and polyhydroxylated derivatives, and [[heterocyclic compound]]s.<ref name=":0" /><ref>{{Cite book | vauthors = Betts WD | editor-last1 = John Wiley & Sons, Inc | chapter = Tar and pitch | title = Kirk-Othmer Encyclopedia of Chemical Technology | location = New York | year = 1997 | doi = 10.1002/0471238961 | publisher = John Wiley & Sons, Inc. | isbn = 978-0-471-23896-6 | edition = 5th }}</ref>

Others: benzene, [[toluene]], [[xylene]]s, [[cumene]]s, [[Benzofuran|coumarone]], [[indene]], [[benzofuran]], [[naphthalene]] and [[Methylnaphthalene|methyl-naphthalenes]], [[acenaphthene]], [[fluorene]], [[phenol]], [[cresol]]s, [[pyridine]], [[picoline]]s, phenanthracene, [[carbazole]], [[quinoline]]s, [[fluoranthene]].<ref name="Roberts_2014" /> Many of these constituents are known carcinogens.<ref>{{Cite web | title = EUR-Lex - 32013R1272 - EN - EUR-Lex | url = http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32013R1272 | website = eur-lex.europa.eu | language = en | archive-url = https://web.archive.org/web/20151019180649/http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32013R1272 | archive-date = 2015-10-19 | url-status = dead | access-date = 2017-06-10 | quote = ...are classified as carcinogens of category 1B in accordance with Annex VI to Regulation (EC) No 1272/2008 of the European Parliament }}</ref><ref name="cite40d09166">{{Cite web | title = COAL TAR - National Library of Medicine HSDB Database | url = https://www.nlm.nih.gov/toxnet/index.html | website = toxnet.nlm.nih.gov | access-date = 2017-06-10 | url-status = live | archive-url = https://web.archive.org/web/20170528211224/https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb%3A%40term+%40DOCNO+5050 | archive-date = 2017-05-28 }}</ref>

===Derivatives===
Various [[phenols|phenolic]] coal tar derivatives have [[analgesic]] (pain-killer) properties. These included [[acetanilide]], [[phenacetin]], and [[paracetamol]] aka [[acetaminophen]].<ref name="Dronsfield_2005">{{cite magazine | vauthors = Dronsfield A | title = Pain relief: from coal tar to paracetamol | volume = 42 | issue = 4 | pages = 102–105 | date = 1 July 2005 | url = https://eic.rsc.org/feature/pain-relief-from-coal-tar-to-paracetamol/2020140.article | url-status = live | magazine = [[Education in Chemistry]] | publisher = [[Royal Society of Chemistry]] | archive-url = https://web.archive.org/web/20171013013607/https://eic.rsc.org/feature/pain-relief-from-coal-tar-to-paracetamol/2020140.article | archive-date = 13 October 2017 | access-date = 14 June 2018 }}</ref> Paracetamol may be the only coal-tar derived analgesic still in use today.<ref name="Brown_2005">{{cite news | vauthors = Brown T, Dronsfield A, Ellis P | title = Pain relief: from coal tar to paracetamol | date = 1 July 2005 | url = https://edu.rsc.org/feature/pain-relief-from-coal-tar-to-paracetamol/2020140.article | publisher = Royal Society of Chemistry }}</ref> Industrial [[phenol]] is now usually synthesized from crude oil rather than coal tar.<ref name="Jones_2011">{{cite journal | vauthors = Jones AW | title = Early drug discovery and the rise of pharmaceutical chemistry | journal = Drug Testing and Analysis | volume = 3 | issue = 6 | pages = 337–344 | date = June 2011 | pmid = 21698778 | doi = 10.1002/dta.301 }}</ref>

Coal tar derivatives are contra-indicated for people with the inherited red cell blood disorder [[glucose-6-phosphate dehydrogenase deficiency]] (G6PD deficiency), as they can cause oxidative stress leading to red blood cell breakdown.<ref name="US_EPA_National_Center_for_Environmental_Assessment_2009">{{cite web | vauthors = ((US EPA National Center for Environmental Assessment)) | title = Hematologic Disorders | date = 15 March 2009 | url = https://hero.epa.gov/hero/index.cfm/reference/details/reference_id/1390864 | website = hero.epa.gov | access-date = 21 April 2020 | language = en }}</ref>

== Mechanism of action ==
The exact mechanism of action is unknown.<ref name="Mai2011" /> Coal tar is a complex mixture of [[phenols]], polycyclic aromatic hydrocarbons, and [[heterocyclic compound]]s.<ref name="cdc24" />

It is a [[keratolytic]] agent, which reduces the growth rate of skin cells and softens the skin's [[keratin]].<ref name="Roberts_2014" /><ref>{{Cite web | title = WHO Model Prescribing Information: Drugs Used in Skin Diseases: Keratoplastic and keratolytic agents: Coal tar | url = http://apps.who.int/medicinedocs/en/d/Jh2918e/26.2.html#Jh2918e.26.2 | website = apps.who.int | access-date = 2017-06-10 | quote = keratolytic agent that inhibits excessive proliferation of epidermal cells by reducing DNA synthesis and mitotic activity to normal levels | url-status = dead | archive-url = https://web.archive.org/web/20170420161122/http://apps.who.int/medicinedocs/en/d/Jh2918e/26.2.html#Jh2918e.26.2 | archive-date = 2017-04-20 }}</ref>

== Uses ==
=== Medicinal ===
Coal tar is on the [[World Health Organization's List of Essential Medicines]].<ref name="WHO2008" /> Coal tar is generally available as a [[generic medication]] [[over the counter]] for topical use, typically as a shampoo.<ref name="aad25" /><ref name="Chat_2022" />

Coal tar may be used in two forms: crude coal tar ({{langx|la|pix carbonis}}) or a coal tar solution ({{langx|la|liquor picis carbonis, LPC}}) also known as liquor carbonis detergens.<ref name="Mai2011" /><ref name="Pharmacyaus">{{cite book | vauthors = Hughes J, Donnelly R, James-Chatgilaou G | title = Clinical pharmacy : a practical approach - Society of Hospital Pharmacists of Australia | location = South Yarra | pages = 114 | date = 2001 | publisher = Macmillan Publishers Australia | isbn = 978-0-7329-8029-0 }}</ref><ref name="Paghdal_2009">{{cite journal | vauthors = Paghdal KV, Schwartz RA | title = Topical tar: back to the future | journal = Journal of the American Academy of Dermatology | volume = 61 | issue = 2 | pages = 294–302 | date = August 2009 | pmid = 19185953 | doi = 10.1016/j.jaad.2008.11.024 }}</ref>  When used as a topical medication, it is supplied in the form of coal tar solution [[United States Pharmacopeia|USP]], which consists of a [[Mass concentration (chemistry)|20% w/v]] solution of coal tar in [[ethanol|alcohol]], with an additional 5% w/v of [[polysorbate 80]]&nbsp;USP; this must then be diluted in an ointment base, such as [[petrolatum]].

Coal tar is also used as a [[Wrights Coal Tar Soap|soap]] and [[ointment]]. It demonstrates [[antifungal]], [[anti-inflammatory]], [[antipruritic|anti-itch]], and [[antiparasitic]] properties.<ref name="Mai2011" /> It may be applied topically as a treatment for dandruff and psoriasis, and to kill and repel [[head lice]].<ref name="aad25" /><ref name="Chat_2022" /><ref name="WHO2008" /><ref name="npf">{{cite web | title = Scalp psoriasis | date = 2025 | url = https://www.psoriasis.org/scalp/#treatment-management | publisher = National Psoriasis Foundation | access-date = 21 September 2025 }}</ref> It may be used in combination with [[ultraviolet light therapy]] called Goeckerman therapy.<ref name="WHO2008" /><ref name="Lie_2024" />

Although coal tar topical products have been used to treat childhood psoriasis, this is an uncommon clinical practice, with risk of cancer development existing from long-term treatment.<ref name="Lie_2024">{{cite journal | vauthors = Lie E, Choi M, Wang SP, Eichenfield LF | title = Topical Management of Pediatric Psoriasis: A Review of New Developments and Existing Therapies | journal = Paediatric Drugs | volume = 26 | issue = 1 | pages = 9–18 | date = January 2024 | pmid = 37847480 | pmc = 10769900 | doi = 10.1007/s40272-023-00592-9 }}</ref> Coal tar as a monotherapy for childhood psoriasis has not been adequately studied.<ref name="Lie_2024" />

====Adverse effects====
Possible [[adverse effect]]s of using topical coal tar to treat psoriasis include [[folliculitis]], skin irritation, [[contact dermatitis]], [[phototoxicity]], and changes in skin pigmentation and odor.<ref name="aad25" />

=== Construction ===
{{Main|Sealcoat}}

Coal tar was a component of the first sealed roads. In its original development by [[Edgar Purnell Hooley]], [[Tarmacadam|tarmac]] was tar covered with granite chips. Later the filler used was industrial [[slag]]. Today, petroleum-derived binders and sealers are more often used. These sealers are used to extend the life and reduce maintenance cost associated with [[Asphalt concrete|asphalt]] pavements, primarily in asphalt road paving, car parks and walkways.{{citation needed|date=April 2021}}

Coal tar is incorporated into some parking-lot [[sealcoat]] products used to protect the structural integrity of the underlying pavement.<ref name="fs20113010">{{cite web | vauthors = Mahler BJ, Van Metre PC | title = Coal-Tar-Based Pavement Sealcoat, Polycyclic Aromatic Hydrocarbons (PAHs), and Environmental Health | date = 2 February 2011 | url = https://pubs.usgs.gov/fs/2011/3010/ | publisher = U.S. Geological Survey Fact Sheet | access-date = 8 March 2013 | url-status = live | archive-url = https://web.archive.org/web/20130328042236/http://pubs.usgs.gov/fs/2011/3010/ | archive-date = 2013-03-28 }}</ref> Sealcoat products that are coal-tar based typically contain 20 to 35 percent coal-tar pitch.<ref name="fs20113010" /> Research<ref name="Van_Metre_2010">{{cite journal | vauthors = Van Metre PC, Mahler BJ | title = Contribution of PAHs from coal-tar pavement sealcoat and other sources to 40 U.S. lakes | journal = The Science of the Total Environment | volume = 409 | issue = 2 | pages = 334–344 | date = December 2010 | pmid = 21112613 | doi = 10.1016/j.scitotenv.2010.08.014 | bibcode = 2010ScTEn.409..334V }}</ref> shows that it is used throughout the [[United States of America]], but several areas have banned its use in sealcoat products,<ref name="austin">{{cite web | title = City of Austin Ordinance 20051117-070 | date = 17 November 2005 | url = http://www.austintexas.gov/sites/default/files/files/Watershed/coaltar_ordinance.pdf | access-date = 8 March 2013 | url-status = live | archive-url = https://web.archive.org/web/20130531014726/http://austintexas.gov/sites/default/files/files/Watershed/coaltar_ordinance.pdf | archive-date = 2013-05-31 }}</ref><ref name="dc">{{cite web | title = District Bans Coal-Tar Pavement Products | date = 26 June 2009 | url = http://newsroom.dc.gov/show.aspx/agency/ddoe/section/2/release/17479 | access-date = 8 March 2013 | url-status = live | archive-url = https://web.archive.org/web/20121226213006/http://newsroom.dc.gov/show.aspx/agency/ddoe/section/2/release/17479 | archive-date = 2012-12-26 }}</ref><ref name="dane">{{cite web | title = Ordinance 80 : Establishing Regulations on Coal Tar Sealcoat Products Application and Sale | date = 1 July 2007 | publisher = Dane County Office of Lakes and Watersheds | url = http://pdf.countyofdane.com/ordinances/ORD080.pdf | access-date = 8 March 2013 | url-status = live | archive-url = https://web.archive.org/web/20110824044232/http://pdf.countyofdane.com/ordinances/ORD080.pdf | archive-date = 2011-08-24 }}</ref> including the District of Columbia; Austin, Texas; Dane County, Wisconsin; the state of Washington; and several municipalities in Minnesota and others.<ref>{{cite web | title = Coal Tar Free America&nbsp;– Bans | url = https://coaltarfreeamerica.blogspot.com/p/bans.html | access-date = 8 March 2013 | url-status = live | archive-url = https://web.archive.org/web/20141006095421/http://coaltarfreeamerica.blogspot.com/p/bans.html | archive-date = 2014-10-06 }}</ref><ref name="Mahler_2011">{{cite conference | vauthors = Mahler BJ | title = Causes of Increasing Concentrations of Polycyclic Aromatic Hydrocarbons (PAHs) in U.S. Lakes | date = 14 April 2011 | conference-url = http://www.eesi.org/pahs-increasing-urban-us-lakes-14-apr-2011 | conference = PAHs Increasing in Urban U.S. Lakes | url = http://files.eesi.org/mahler_041411.pdf | publisher = Environmental and Energy Study Institute | access-date = 8 March 2013 | url-status = dead | archive-url = https://web.archive.org/web/20111005105420/http://files.eesi.org/mahler_041411.pdf | archive-date = 5 October 2011 }}</ref>

=== Industry ===
In modern times, coal tar is mostly traded as fuel and as an application for tar, such as roofing. The total value of the trade in coal tar is around US$20 billion per year (2023).<ref>{{cite web | title = Coal Tar Oil &#124; OEC | url = https://oec.world/en/profile/hs/coal-tar-oil }}</ref>
* Historically as a chemical feedstock for dyes.<ref>scientific american article/dyes-from-coal-tar-products/ June 1858</ref>
* As a fuel.
* In the manufacture of paints, synthetic dyes (notably [[tartrazine]]/Yellow #5), and photographic materials.<ref>{{cite book | vauthors = Hathaway AW | title = Remediation of Former Manufactured Gas Plants and Other Coal-Tar Sites | date = 2011 | publisher = Taylor & Francis Group }}</ref>
* For heating or to fire [[boilers]]. Like most heavy oils, it must be heated before it will flow easily.<ref>{{cite book | vauthors = Speight JG | veditors = Luque R, Speight JG | chapter = Coal gasification processes for synthetic liquid fuel production | title = Gasification for Synthetic Fuel Production | pages = 201–220 (212) | date = 2015 | doi = 10.1016/B978-0-85709-802-3.00009-6 | series = Woodhead Publishing Series in Energy | publisher = Woodhead | isbn = 978-0-85709-802-3 | quote = 9.5.1 Coal tar chemicals: Coal tar is a black or dark brown liquid or a high-viscosity semi-solid that is one of the by-products formed when coal is carbonized. Coal tars are complex and variable mixtures of polycyclic aromatic hydrocarbons (PAHs), phenols, and heterocyclic compounds. Because of its flammable composition, coal tar is often used for fire boilers in order to create heat. They must be heated before any heavy oil flows easily. }}</ref>
* As a source of [[carbon black]].<ref>{{cite web | title = Market Study: Carbon Black | url = http://www.ceresana.com/en/market-studies/chemicals/carbon-black/ | access-date = 2013-04-26 | publisher = Ceresana }}</ref>
* As a binder in manufacturing [[graphite]]; a considerable portion of the materials in "green blocks" is coke oven volatiles (COV). During the baking process of the green blocks as a part of commercial graphite production, most of the coal tar binders are vaporised and are generally burned in an incinerator to prevent release into the atmosphere, as COV and coal tar can be injurious to health.<ref>{{Cite web | title = CDC - Immediately Dangerous to Life or Health Concentrations (IDLH): Coal tar pitch volatiles - NIOSH Publications and Products | date = 2018-11-02 | url = https://www.cdc.gov/niosh/idlh/65996932.html | access-date = 2021-10-05 | website = www.cdc.gov | language = en-us }}</ref><ref>{{Cite book | vauthors = Speight JG | title = Asphalt materials science and technology | location = Amsterdam | pages = 60 | date = 2015 | publisher = Elsevier Science | isbn = 978-0-12-800501-9 | oclc = 922698102 }}</ref>
* As a main component of the electrode paste used in electric [[arc furnace]]s. Coal tar pitch act as the binder for solid filler that can be either coke or calcined anthracite, forming electrode paste, also widely known as Söderberg electrode paste.<ref>{{Cite journal | vauthors = Beukes JP, Roos H, Shoko L, Van Zyl PG, Neomagus HW, Strydom CA, Dawson NF | title = The use of thermomechanical analysis to characterise Söderberg electrode paste raw materials | journal = Minerals Engineering | volume = 46-47 | pages = 167–176 | date = June 2013 | doi = 10.1016/j.mineng.2013.04.016 | language = en | issn = 0892-6875 | doi-access = free | bibcode = 2013MiEng..46..167B }}</ref>
* As a feed stock for higher-value fractions, such as [[naphtha]], [[creosote]] and [[Pitch (resin)|pitch]]. In the [[coal gas]] era, companies [[distill]]ed coal tar to separate these out, leading to the discovery of many industrial chemicals.
Some British companies included:<ref>{{Cite journal| vauthors = Ronalds BF |date=2019|title=Bonnington Chemical Works (1822-1878): Pioneer Coal Tar Company|journal=International Journal for the History of Engineering & Technology|volume=89|issue=1–2|pages=73–91|doi=10.1080/17581206.2020.1787807|s2cid=221115202}}</ref><ref>{{cite web | vauthors = Smith M |url= http://www.igg.org.uk/gansg/12-linind/tardis.htm |title=GANSG&nbsp;– Coal Tar Distillers |publisher=Igg.org.uk |access-date=8 March 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130619153801/http://www.igg.org.uk/gansg/12-linind/tardis.htm |archive-date=2013-06-19 }}</ref>

** [[Bonnington Chemical Works]]
** British Tar Products
** Lancashire Tar Distillers
** Midland Tar Distillers
** [[Newton, Chambers & Company]] (owners of Izal brand disinfectant)
** [[Samuel Sadler|Sadlers Chemicals]]
===Chemicals from coal tar===
At one time, coal tar was a major source of organic compounds. This application has almost disappeared with the growth of the [[petrochemical industry]]. Coal tar is produced by thermolysis of coal, usually with the objective of obtaining [[Coke (fuel)|coke]], which is heavily used in the production of iron and [[steel]]. The tar is further processed, generating the following fractions of chemical interest: a mixture of benzene, toluene and xylenes ([[BTX (chemistry)|"BTX"]], phenolics, and polycyclic aromatics, especially [[naphthalene]].<ref>{{cite journal | vauthors = Granda M, Blanco C, Alvarez P, Patrick JW, Menéndez R | title = Chemicals from Coal Coking | journal = Chemical Reviews | volume = 114 | issue = 3 | pages = 1608–1636 | date = 2014 | pmid = 24080106 | doi = 10.1021/cr400256y | hdl = 10261/202957 | hdl-access = free }}</ref>

== Safety ==
Side effects include skin irritation, sun sensitivity, [[allergic reactions]], and skin discoloration.<ref name="WHO2008" /> It is unclear if use during [[pregnancy]] is safe for the baby and its use during [[breastfeeding]] is not typically recommended.<ref>{{cite web | title = Coal Tar use while Breastfeeding {{!}} Drugs.com|url=https://www.drugs.com/breastfeeding/coal-tar.html|website=www.drugs.com|access-date=13 January 2017|url-status=live|archive-url=https://web.archive.org/web/20170118034352/https://www.drugs.com/breastfeeding/coal-tar.html|archive-date=18 January 2017}}</ref> The exact mechanism of action is unknown.<ref name="Mai2011" /> It is a complex mixture of [[phenols]], [[polycyclic aromatic hydrocarbon]]s (PAHs), and [[heterocyclic compound]]s.<ref name="cdc24" /> It demonstrates [[antifungal]], [[anti-inflammatory]], [[antipruritic|anti-itch]], and [[antiparasitic]] properties.<ref name=Mai2011>{{cite book | vauthors = Maibach HI | title = Evidence Based Dermatology | pages = 935–936 | date = 2011 | publisher = PMPH-USA | isbn = 978-1-60795-039-4 | url = https://books.google.com/books?id=V2L1MAoGHVkC&pg=PA935 | language = en | url-status = live | archive-url = https://web.archive.org/web/20170918185259/https://books.google.com/books?id=V2L1MAoGHVkC&pg=PA935 | archive-date = 2017-09-18 }}</ref>

=== Cancer ===
Long-term, consistent exposure to coal tar likely increases the risk of non-melanoma [[skin cancer]]s.<ref>{{cite journal | vauthors = Moustafa GA, Xanthopoulou E, Riza E, Linos A | title = Skin disease after occupational dermal exposure to coal tar: a review of the scientific literature | journal = International Journal of Dermatology | volume = 54 | issue = 8 | pages = 868–879 | date = August 2015 | pmid = 26183242 | doi = 10.1111/ijd.12903 | s2cid = 205189697 | doi-access = free }}</ref> Evidence is inconclusive as to whether medical coal tar, which does not remain on the skin for the long periods seen in occupational [[Exposure assessment#Exposure|exposure]], causes cancer, because there is insufficient data to make a judgment.<ref name="Roelofzen_2010">{{cite journal | vauthors = Roelofzen JH, Aben KK, Oldenhof UT, Coenraads PJ, Alkemade HA, van de Kerkhof PC, van der Valk PG, Kiemeney LA | title = No increased risk of cancer after coal tar treatment in patients with psoriasis or eczema | journal = The Journal of Investigative Dermatology | volume = 130 | issue = 4 | pages = 953–961 | date = April 2010 | pmid = 20016499 | doi = 10.1038/jid.2009.389 | doi-access = free }}</ref> While coal tar consistently causes cancer in cohorts of workers with chronic occupational exposure, animal models, and mechanistic studies,<ref name=":0" /> the data on short-term use as medicine in humans has so far failed to show any consistently significant increase in rates of cancer.<ref name="Roelofzen_2010" />

Coal tar contains many [[polycyclic aromatic hydrocarbons]], and it is believed that their metabolites bind to DNA, damaging it.<ref name="cite40d09166" /> The PAHs found in coal tar and air pollution induce [[immunosenescence]] and cytotoxicity in epidermal cells.<ref>{{cite journal | vauthors = Pan TL, Wang PW, Aljuffali IA, Huang CT, Lee CW, Fang JY | title = The impact of urban particulate pollution on skin barrier function and the subsequent drug absorption | journal = Journal of Dermatological Science | volume = 78 | issue = 1 | pages = 51–60 | date = April 2015 | pmid = 25680853 | doi = 10.1016/j.jdermsci.2015.01.011 | language = English }}</ref><ref>{{cite journal | vauthors = Qiao Y, Li Q, Du HY, Wang QW, Huang Y, Liu W | title = Airborne polycyclic aromatic hydrocarbons trigger human skin cells aging through aryl hydrocarbon receptor | journal = Biochemical and Biophysical Research Communications | volume = 488 | issue = 3 | pages = 445–452 | date = July 2017 | pmid = 28526404 | doi = 10.1016/j.bbrc.2017.04.160 | bibcode = 2017BBRC..488..445Q }}</ref> It is possible that the skin can repair itself from this damage after short-term exposure to PAHs but not after long-term exposure.<ref name="Roelofzen_2010" /> Long-term skin exposure to these compounds can produce "[[tar warts]]", which can progress to [[squamous cell carcinoma]].<ref name="Roberts_2014" />

Coal tar was one of the first chemical substances proven to cause cancer from occupational exposure, during research in 1775 on the cause of [[chimney sweeps' carcinoma]].<ref name="Roberts_2014" /> Modern studies have shown that working with coal tar pitch, such as during the paving of roads or when working on roofs, increases the risk of cancer.<ref name=":0">{{cite book | title = Coal-tar pitch | url = https://monographs.iarc.fr/ENG/Monographs/vol100F/mono100F-17.pdf | publisher = IARC | archive-url = https://web.archive.org/web/20160521101818/http://monographs.iarc.fr/ENG/Monographs/vol100F/mono100F-17.pdf | archive-date = 21 May 2016 | url-status = live | access-date = 10 June 2017 | quote = it was concluded that there is sufficient evidence in humans for the carcinogenicity of occupational exposures during paving and roofing with coal tar pitch. ... Six coal-tar pitches and three extracts of coal-tar pitches all produced skin tumours, including carcinomas, when applied to the skin of mice }}</ref>

The [[International Agency for Research on Cancer]] lists coal tars as [[List of IARC Group 1 carcinogens|Group 1]] [[carcinogen]]s, meaning they directly cause cancer.<ref name=":0" /><ref>{{cite book | vauthors = ((IARC Working Group on the Evaluation of Carcinogenic Risks to Humans.)) | chapter = Chemical Agents and Related Occupations. | title = Coal-Tar Pitch | location = Lyon (FR) | issue = 100F | date = 2012 | publisher = International Agency for Research on Cancer | series = IARC Monographs on the Evaluation of Carcinogenic Risks to Humans | chapter-url = https://www.ncbi.nlm.nih.gov/books/NBK304423/ }}</ref><ref>{{Cite book | chapter = COAL-TARS (Group I) | title = IARC MONOGRAPHS SUPPLEMENT 7 | pages = 175 | date = 1987 | chapter-url = https://monographs.iarc.fr/ENG/Monographs/suppl7/Suppl7-58.pdf | publisher = IARC | isbn = 978-92-832-1411-3 | quote = Evidence for carcinogenicity to humans (sufficient) | url-status = live | archive-url = https://web.archive.org/web/20160315151519/http://monographs.iarc.fr/ENG/Monographs/suppl7/Suppl7-58.pdf | archive-date = 2016-03-15 }}</ref> The U.S. Department of Health and Human Services lists coal tars as known human carcinogens.<ref>{{Cite web | title = Report on Carcinogens, Fourteenth Edition: Coal Tars and Coal-Tar Pitches | url = https://ntp.niehs.nih.gov/sites/default/files/ntp/roc/content/profiles/coaltars.pdf | website = National Toxicology Program, Department of Health and Human Services | language = en-us | access-date = 2017-06-10 | url-status = live | archive-url = https://web.archive.org/web/20170201002821/https://ntp.niehs.nih.gov/ntp/roc/content/profiles/coaltars.pdf | archive-date = 2017-02-01 }}</ref>

In response to public health concerns regarding the carcinogenicity of PAHs some municipalities, such as the city of Milwaukee, have banned the use of common coal tar-based road and driveway sealants, citing concerns of elevated PAH content in groundwater.<ref>{{cite news | vauthors = Quirmbach C | title = Milwaukee Common Council Bans Coal Tar Sealants | date = 7 February 2017 | url = https://www.wiscontext.org/milwaukee-common-council-bans-coal-tar-sealants | publisher = Wisconsin Public Radio }}</ref>

=== Other ===
Coal tar causes [[sun poisoning|increased sensitivity to sunlight]],<ref name="medicinenet">{{cite web | title = Sun-Sensitive Drugs (Photosensitivity to Drugs) | pages = 5 | date = 2008-08-22 | url = http://www.medicinenet.com/sun-sensitive_drugs_photosensitivity_to_drugs/page5.htm | work = MedicineNet | publisher = [[WebMD]] | access-date = 8 March 2013 | url-status = live | archive-url = https://web.archive.org/web/20130317004507/http://www.medicinenet.com/sun-sensitive_drugs_photosensitivity_to_drugs/page5.htm | archive-date = 2013-03-17 }}</ref> so skin treated with topical coal tar preparations should be protected from sunlight.

The residue from the [[distillation]] of high-temperature coal tar, primarily a complex mixture of three or more membered condensed ring [[aromatic hydrocarbon]]s, was listed on 13 January 2010 as a [[substance of very high concern]] by the [[European Chemicals Agency]].<ref>{{cite web | title = Candidate List of substances of very high concern for Authorisation | date = nd | url = https://echa.europa.eu/candidate-list-table/-/dislist/details/0b0236e1807d8743 | website = echa.europa.eu/home | access-date = 27 October 2021 }}</ref>

=== Regulation ===
The U.S. [[Occupational Safety and Health Administration]] (OSHA) has set the [[permissible exposure limit]]) to 0.2&nbsp;mg/m<sup>3</sup> [[benzene]]-soluble fraction over an 8-hour workday. The U.S. [[National Institute for Occupational Safety and Health]] (NIOSH) has set a [[recommended exposure limit]] (REL) of 0.1&nbsp;mg/m<sup>3</sup> [[cyclohexane]]-extractable fraction over an 8-hour workday. At levels of 80&nbsp;mg/m<sup>3</sup>, coal tar pitch volatiles are [[IDLH|immediately dangerous to life and health]].<ref>{{Cite web | title = CDC&nbsp;– NIOSH Pocket Guide to Chemical Hazards&nbsp;– Coal tar pitch volatiles | url = https://www.cdc.gov/niosh/npg/npgd0145.html | website = cdc.gov | access-date = 2015-11-27 | url-status = live | archive-url = https://web.archive.org/web/20151208120356/http://www.cdc.gov/niosh/npg/npgd0145.html | archive-date = 2015-12-08 }}</ref>

== See also ==
*[[Coal oil]]
*[[Wood tar]]

== References ==
{{Reflist}}

== External links ==
{{Wiktionary}}

* {{cite web | title = Coal Tar Pitch Volatiles | date = 22 March 2012 | url = http://www.osha.gov/SLTC/coaltarpitchvolatiles/index.html | publisher = Occupational Safety & Health Administration | access-date = 8 March 2013 }}
* {{cite web | title = NIOSH Pocket Guide to Chemical Hazards&nbsp;– Coal Tar Pitch Volatiles | date = 11 April 2011 | url = https://www.cdc.gov/niosh/npg/npgd0145.html | publisher = Centers for Disease Control and Prevention | access-date = 13 September 2013 }}
* {{Cite journal | vauthors = Engelhaupt E | title = Parking lots create sticky pollution problem | journal = Environmental Science and Technology | volume = 43 | issue = 1 | pages = 3 | date = 19 November 2008 | doi = 10.1021/es803118b | bibcode = 2009EnST...43....3E | doi-access = free }}
* {{cite EB1911 | vauthors = Lunge G | volume = 6 | pages = 595–599 | wstitle = Coal-Tar | author-link = Georg Lunge }}

{{Coal}}
{{Antipsoriatics}}
{{portal bar|Medicine}}

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