View source for Coal tar

{{cs1 config|name-list-style=vanc}}
{{Short description|Chemical mixture}}
{{about|the substance|the book|
Coal Tar: How Corrupt Politics and Corporate Greed Are Killing America's Children}}
{{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=bmj>{{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      = 
<!-- Pharmacokinetic data -->
| 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''' is a thick dark liquid which is a by-product of the production of [[coke (fuel)|coke]] and [[coal gas]] from [[coal]].<ref name=CDC2002/><ref>{{cite book| vauthors = Vallee Y |title=Gas Phase Reactions in Organic Synthesis|date=1998|publisher=CRC Press|isbn=9789056990817|page=107|url=https://books.google.com/books?id=lfBC9hj9iH8C&pg=PA107|language=en}}</ref> It is a type of [[creosote]]. It has both medical and industrial uses.<ref name=CDC2002/><ref name=Ric2015/> Medicinally it is a [[topical medication]] applied to [[Human skin|skin]] to treat [[psoriasis]] and [[seborrheic dermatitis]] ([[dandruff]]).<ref name= WHO2008/> It may be used in combination with [[ultraviolet light therapy]].<ref name=WHO2008>{{cite book | title = WHO Model Formulary 2008 | year = 2009 | isbn = 9789241547659 | vauthors = ((World Health Organization)) | veditors = Stuart MC, Kouimtzi M, Hill SR | hdl = 10665/44053 | author-link = World Health Organization | publisher = World Health Organization | page = 308 }}</ref> Industrially it is a [[railroad tie]] preservative and used in the surfacing of roads.<ref name=Ho1991/> 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>

<!-- History and culture -->
Coal tar was discovered circa 1665 and used for medical purposes as early as the 1800s.<ref name=Ho1991>{{cite book| vauthors = Hornbostel C |title=Construction Materials: Types, Uses and Applications|date=1991|publisher=John Wiley & Sons|isbn=9780471851455|page=864|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><ref>{{cite book| vauthors = Sneader W |title=Drug Discovery: A History|date=2005|publisher=John Wiley & Sons|isbn=9780471899792|page=356|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> Circa 1850, the discovery that it could be used as the main raw material for the synthesis of [[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> It is on the [[WHO Model List of Essential Medicines|World Health Organization's List of Essential Medicines]].<ref name="WHO21st">{{cite book | vauthors = ((World Health Organization)) | title = World Health Organization model list of essential medicines: 21st list 2019 | year = 2019 | hdl = 10665/325771 | author-link = World Health Organization | publisher = World Health Organization | location = Geneva | id = WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO | hdl-access=free }}</ref> Coal tar is available as a [[generic medication]] and [[over the counter]].<ref name=Ric2015>{{cite book| vauthors = Hamilton R |title=Tarascon Pocket Pharmacopoeia 2015 Deluxe Lab-Coat Edition|date=2015|publisher=Jones & Bartlett Learning|isbn=9781284057560|page=X}}</ref>

<!-- side effects and mechanism -->
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 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=CDC2002>{{cite web|title=Background and Environmental Exposures to Creosote in the United States|url=https://www.atsdr.cdc.gov/toxprofiles/tp85-c2.pdf|website=cdc.gov|access-date=13 January 2017|page=19|date=September 2002|url-status=live|archive-url=https://web.archive.org/web/20170125025514/https://www.atsdr.cdc.gov/ToxProfiles/tp85-c2.pdf|archive-date=25 January 2017}}</ref> It demonstrates [[antifungal]], [[anti-inflammatory]], [[antipruritic|anti-itch]], and [[antiparasitic]] properties.<ref name=Mai2011>{{cite book| vauthors = Maibach HI |title=Evidence Based Dermatology|date=2011|publisher=PMPH-USA|isbn=9781607950394|pages=935–936|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>

== 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=":1">{{Cite book|title=Encyclopedia of Toxicology| vauthors = Roberts L |date=2014|publisher=Academic Press|isbn=9780123864550| veditors = Wexler P |location=Oxford|pages=993–995|doi=10.1016/b978-0-12-386454-3.00012-9|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.|chapter=Coal Tar|edition=Third}}</ref>

Coal tar is a mixture of approximately 10,000 chemicals, of which only about 50% have been identified.<ref>{{Cite journal|date=May 1963|doi=10.1021/ie50641a006| vauthors = Heinz-Gerhard F |title=The Challenge in Coal Tar Chemicals|journal=Industrial & Engineering Chemistry|volume = 55|issue=5|pages=38–44}}</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 |url=http://worldcat.org/oclc/816079578 |title=Creosote. |date=2002 |publisher=Agency for Toxic Substances Disease Registry, Division of Toxicology, Dept. of Health and Human Services, Public Health Service |location=US |language=en |oclc=816079578}}</ref><ref>{{Cite web |date=September 2002 |title=Public Health Statement for Creosote |url=https://wwwn.cdc.gov/TSP/PHS/PHS.aspx?phsid=64&toxid=18 |publisher=Agency for Toxic Substances and Disease Registry}}</ref>

* [[polycyclic aromatic hydrocarbon]]s (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|title=Kirk-Othmer Encyclopedia of Chemical Technology| vauthors = Betts WD | editor-last1 = John Wiley & Sons, Inc |publisher=John Wiley & Sons, Inc. |year=1997|isbn=9780471238966|edition=5th|location=New York|chapter=Tar and pitch|doi=10.1002/0471238961 }}</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=":1" /> Many of these constituents are known carcinogens.<ref>{{Cite web|url=http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32013R1272|title=EUR-Lex - 32013R1272 - EN - EUR-Lex|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=":2">{{Cite web|url=https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+5050|title=COAL TAR - National Library of Medicine HSDB Database|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="para">{{cite magazine | vauthors = Dronsfield A |date=1 July 2005 |title=Pain relief: from coal tar to paracetamol |url=https://eic.rsc.org/feature/pain-relief-from-coal-tar-to-paracetamol/2020140.article |volume=42 |issue=4 |pages=102–105 |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="rscbde05">{{cite news | vauthors = Brown T, Dronsfield A, Ellis P |title=Pain relief: from coal tar to paracetamol |url=https://edu.rsc.org/feature/pain-relief-from-coal-tar-to-paracetamol/2020140.article |publisher=Royal Society of Chemistry |date=1 July 2005}}</ref> Industrial [[phenol]] is now usually synthesized from crude oil rather than coal tar.<ref name="jones11">{{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 = 337–44 | 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=epahema>{{cite web | author = US EPA National Center for Environmental Assessment |title=Hematologic Disorders |url=https://hero.epa.gov/hero/index.cfm/reference/details/reference_id/1390864 |website=hero.epa.gov |access-date=21 April 2020 |language=en |date=15 March 2009}}</ref>

== Mechanism of action ==
The exact mechanism of action is unknown.<ref name="Mai2011" /> Coal tar is a complex mixture of [[phenols]], [[polycyclic aromatic hydrocarbon]]s (PAHs), and [[heterocyclic compound]]s.<ref name="CDC2002" />

It is a [[keratolytic]] agent, which reduces the growth rate of skin cells and softens the skin's [[keratin]].<ref>{{Cite web|url=http://apps.who.int/medicinedocs/en/d/Jh2918e/26.2.html#Jh2918e.26.2|title=WHO Model Prescribing Information: Drugs Used in Skin Diseases: Keratoplastic and keratolytic agents: Coal tar|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><ref name=":1" />

== Uses ==
=== Medicinal ===
Coal tar is on the [[World Health Organization's List of Essential Medicines]], the most effective and safe medicines needed in a [[health system]].<ref name="WHO21st"/> Coal tar is generally available as a [[generic medication]] and [[over the counter]].<ref name="Ric2015" />

Coal tar is used in medicated [[shampoo]], [[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="WHO2008"/> It may be used in combination with [[ultraviolet light therapy]].<ref name="WHO2008" />

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 (LCD).<ref name="Mai2011"/><ref name="Pharmacyaus">{{cite book|title=Clinical pharmacy : a practical approach - Society of Hospital Pharmacists of Australia| vauthors = Hughes J, Donnelly R, James-Chatgilaou G |date=2001|publisher=Macmillan Publishers Australia|isbn=9780732980290|location=South Yarra|page=114}}</ref><ref name="paghdal">{{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> Named brands include Denorex, Balnetar, Psoriasin, Tegrin, T/Gel, and Neutar. When used in the extemporaneous preparation of topical medications, it is supplied in the form of coal tar topical 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]].

=== 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 commonly 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 | url = http://pubs.usgs.gov/fs/2011/3010/| title = Coal-Tar-Based Pavement Sealcoat, Polycyclic Aromatic Hydrocarbons (PAHs), and Environmental Health| publisher = U.S. Geological Survey Fact Sheet| date = 2 February 2011| 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=lakes>{{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 = 334–44 | date = December 2010 | pmid = 21112613 | doi = 10.1016/j.scitotenv.2010.08.014 | bibcode = 2010ScTEn.409..334V }}</ref> shows it is used throughout the [[United States of America]], however several areas have banned its use in sealcoat products,<ref name=austin>{{cite web| url = http://www.austintexas.gov/sites/default/files/files/Watershed/coaltar_ordinance.pdf| title = City of Austin Ordinance 20051117-070| date = 17 November 2005| 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| url = http://newsroom.dc.gov/show.aspx/agency/ddoe/section/2/release/17479| date = 26 June 2009| 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| publisher = Dane County Office of Lakes and Watersheds| url = http://pdf.countyofdane.com/ordinances/ORD080.pdf| title = Ordinance 80 : Establishing Regulations on Coal Tar Sealcoat Products Application and Sale| date = 1 July 2007| 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; the city of 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 = http://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="EESI">{{cite conference| 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| title = Causes of Increasing Concentrations of Polycyclic Aromatic Hydrocarbons (PAHs) in U.S. Lakes| vauthors = Mahler BJ | publisher = Environmental and Energy Study Institute| date = 14 April 2011| 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 an application for tar, such as roofing. The total value of the trade in coal tar is around US$20 billion each year.<ref>{{cite web | url=https://oec.world/en/profile/hs/coal-tar-oil | title=Coal Tar Oil &#124; OEC }}</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 | chapter = Coal gasification processes for synthetic liquid fuel production | veditors = Luque R, Speight JG | title = Gasification for Synthetic Fuel Production | series = Woodhead Publishing Series in Energy |date=2015 |pages=201–220 (212) | publisher = Woodhead | isbn = 978-0-85709-802-3 |doi=10.1016/B978-0-85709-802-3.00009-6 | 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|date=2018-11-02|title=CDC - Immediately Dangerous to Life or Health Concentrations (IDLH): Coal tar pitch volatiles - NIOSH Publications and Products|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|date=2015|publisher=Elsevier Science|isbn=978-0-12-800501-9|location=Amsterdam|page=60|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 |date= June 2013 |title=The use of thermomechanical analysis to characterise Söderberg electrode paste raw materials |journal=Minerals Engineering |language=en |volume=46-47 |pages=167–176 |doi=10.1016/j.mineng.2013.04.016 |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]]

== Safety ==
Side effects of coal tar products 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 use during [[breastfeeding]] is not typically recommended.<ref>{{cite web|url=https://www.drugs.com/breastfeeding/coal-tar.html|title=Coal Tar use while Breastfeeding |website= Drugs.com|date = 2 June 2023 |archive-url= https://web.archive.org/web/20230926083525/https://www.drugs.com/breastfeeding/coal-tar.html |archive-date=26 September 2023|url-status=live}}</ref>

According to the [[National Psoriasis Foundation]], coal tar is a valuable, safe and inexpensive treatment option for millions of people with [[psoriasis]] and other scalp or skin conditions.<ref name=coalcal>{{cite web| url = http://www.psoriasis.org/news/stories/2001/20011202_coalcala.php| title = The battle to save coal tar in California| date = 3 December 2001| archive-url = https://web.archive.org/web/20021029132630/http://www.psoriasis.org/coaltar.advocacy.htm| archive-date = 2002-10-29| access-date = 8 March 2013| url-status = dead}}</ref> According to the [[FDA]], coal tar concentrations between 0.5% and 5% are considered safe<ref>{{cite web| url = https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?cfrpart=358&showfr=1&subpartnode=21:5.0.1.1.30.8| title = Drug Products for the Control of Dandruff, Seborrheic Dermatitis, and Psoriasis| author = FDA| date = 1 April 2015| access-date = 26 February 2016| url-status = live| archive-url = https://web.archive.org/web/20150918184253/http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=358&showFR=1&subpartNode=21%3A5.0.1.1.30.8| archive-date = September 18, 2015}}</ref> and effective for psoriasis.

=== 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 = 868–79 | date = August 2015 | pmid = 26183242 | doi = 10.1111/ijd.12903 | s2cid = 205189697 | doi-access = free }}</ref> Evidence is inconclusive 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=Ro2010>{{cite journal | vauthors = Roelofzen JH, Aben KK, Oldenhof UT, Coenraads PJ, Alkemade HA, van de Kerkhof PC, van der Valk PG, Kiemeney LA | display-authors = 6 | 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 = 953–61 | 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=Ro2010/>

Coal tar contains many [[polycyclic aromatic hydrocarbons]], and it is believed that their metabolites bind to DNA, damaging it.<ref name=":2" /> 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 | language = English | 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 }}</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 }}</ref> It's possible that the skin can repair itself from this damage after short-term exposure to PAHs but not after long-term exposure.<ref name="Ro2010" /> Long-term skin exposure to these compounds can produce "[[tar warts]]", which can progress to [[squamous cell carcinoma]].<ref name=":1" />

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=":1" /> 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|url=https://monographs.iarc.fr/ENG/Monographs/vol100F/mono100F-17.pdf|title=Coal-tar pitch|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 | author = IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. | chapter = Chemical Agents and Related Occupations. | location = Lyon (FR) | publisher = International Agency for Research on Cancer | date = 2012 | series = IARC Monographs on the Evaluation of Carcinogenic Risks to Humans | issue = 100F | title = Coal-Tar Pitch | chapter-url = https://www.ncbi.nlm.nih.gov/books/NBK304423/ }}</ref><ref>{{Cite book|chapter-url=https://monographs.iarc.fr/ENG/Monographs/suppl7/Suppl7-58.pdf|title=IARC MONOGRAPHS SUPPLEMENT 7|publisher=IARC|pages=175|chapter=COAL-TARS (Group I)|date=1987 |isbn=9789283214113|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|url=https://ntp.niehs.nih.gov/ntp/roc/content/profiles/coaltars.pdf|title=Report on Carcinogens, Fourteenth Edition: Coal Tars and Coal-Tar Pitches|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 |url=https://www.wiscontext.org/milwaukee-common-council-bans-coal-tar-sealants |publisher=Wisconsin Public Radio |date=7 February 2017}}</ref>

=== Other ===
Coal tar causes [[sun poisoning|increased sensitivity to sunlight]],<ref name="medicinenet">{{cite web |title= Sun-Sensitive Drugs (Photosensitivity to Drugs) |url= http://www.medicinenet.com/sun-sensitive_drugs_photosensitivity_to_drugs/page5.htm |date= 2008-08-22 |page= 5 |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
 | url = https://echa.europa.eu/candidate-list-table/-/dislist/details/0b0236e1807d8743
 |website=echa.europa.eu/home
 | date = nd
 | access-date = 27 October 2021}}</ref>

=== Regulation ===
Exposure to coal tar pitch volatiles can occur in the workplace by breathing, skin contact, or eye contact. The [[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 [[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>

When used as a medication in the United States, coal tar preparations are considered [[over-the-counter drug]] pharmaceuticals and are subject to regulation by the [[Food and Drug Administration]] (FDA).

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

== References ==
{{Reflist}}

== External links ==
{{Wiktionary}}

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

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

{{Authority control}}

[[Category:Antipsoriatics]]
[[Category:Coal]]
[[Category:IARC Group 1 carcinogens]]
[[Category:Materials]]
[[Category:World Health Organization essential medicines]]
[[Category:Wikipedia medicine articles ready to translate]]
[[Category:Drugs with unknown mechanisms of action]]