Coal tar

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This article is about the substance. For the book, see Coal Tar: How Corrupt Politics and Corporate Greed Are Killing America's Children.
Coal tar
Clinical data
Trade namesBalnetar, Cutar, others
Other namesliquor carbonis detergens (LCD)
liquor picis carbonis (LPC)[1]
AHFS/Drugs.comMultum Consumer Information
Routes of
administration		Topical
ATC code
Legal status
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  • US: OTC / Rx-only
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100.029.417 Edit this at Wikidata

Coal tar is a thick dark liquid which is a by-product of the production of

seborrheic dermatitis (dandruff).[5] It may be used in combination with ultraviolet light therapy.[5] Industrially it is a railroad tie preservative and used in the surfacing of roads.[6] Coal tar was listed as a known human carcinogen in the first Report on Carcinogens from the U.S. Federal Government, issued in 1980.[7]

Coal tar was discovered circa 1665 and used for medical purposes as early as the 1800s.

over the counter.[4]

Side effects include skin irritation, sun sensitivity,

allergic reactions, and skin discoloration.[5] It is unclear if use during pregnancy is safe for the baby and use during breastfeeding is not typically recommended.[11] The exact mechanism of action is unknown.[12] It is a complex mixture of phenols, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds.[2] It demonstrates antifungal, anti-inflammatory, anti-itch, and antiparasitic properties.[12]

Composition

Coal tar is produced through thermal destruction (pyrolysis) of coal. Its composition varies with the process and type of coal used – lignite, bituminous or anthracite.[13]

Coal tar is a mixture of approximately 10,000 chemicals, of which only about 50% have been identified.

better source needed] Most of the chemical compounds are polycyclic aromatic hydrocarbon:[15][16]

Others: benzene, toluene, xylenes, cumenes, coumarone, indene, benzofuran, naphthalene and methyl-naphthalenes, acenaphthene, fluorene, phenol, cresols, pyridine, picolines, phenanthracene, carbazole, quinolines, fluoranthene.[13] Many of these constituents are known carcinogens.[19][20]

Derivatives

Various

acetaminophen.[21] Paracetamol may be the only coal-tar derived analgesic still in use today.[22] Industrial phenol is now usually synthesized from crude oil rather than coal tar.[23]

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.[24]

Mechanism of action

The exact mechanism of action is unknown.[12] Coal tar is a complex mixture of phenols, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds.[2]

It is a keratolytic agent, which reduces the growth rate of skin cells and softens the skin's keratin.[25][13]

Uses

Medicinal

Coal tar is on the

over the counter.[4]

Coal tar is used in medicated

head lice.[5] It may be used in combination with ultraviolet light therapy.[5]

Coal tar may be used in two forms: crude coal tar (

petrolatum
.

Construction

Main article: Sealcoat

Coal tar was a component of the first sealed roads. In its original development by Edgar Purnell Hooley, 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 pavements, primarily in asphalt road paving, car parks and walkways.[citation needed]

Coal tar is incorporated into some parking-lot

United States of America, however several areas have banned its use in sealcoat products,[30][31][32] including the District of Columbia; the city of Austin, Texas; Dane County, Wisconsin; the state of Washington; and several municipalities in Minnesota and others.[33][34]

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.[35]

  • As a fuel.
  • In the manufacture paints of , synthetic dyes (notably tartrazine/Yellow #5), and photographic materials.[36]
  • For heating or to fire
    boilers. Like most heavy oils, it must be heated before it will flow easily.[37]
  • 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.[38][39]
  • As a main component of the
    arc furnaces. 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.[40]
  • As a feed stock for higher-value fractions, such as
    distilled
    coal tar to separate these out, leading to the discovery of many industrial chemicals.
Some British companies included:[41][42]

Safety

Side effects of coal tar products include skin irritation, sun sensitivity,

allergic reactions, and skin discoloration.[5] It is unclear if use during pregnancy is safe for the baby and use during breastfeeding is not typically recommended.[43]

According to the

FDA, coal tar concentrations between 0.5% and 5% are considered safe[45]
and effective for psoriasis.

Cancer

Long-term, consistent exposure to coal tar likely increases the risk of non-melanoma skin cancers.[46] Evidence is inconclusive whether medical coal tar, which does not remain on the skin for the long periods seen in occupational exposure, causes cancer, because there is insufficient data to make a judgment.[47] While coal tar consistently causes cancer in cohorts of workers with chronic occupational exposure, animal models, and mechanistic studies,[17] the data on short-term use as medicine in humans has so far failed to show any consistently significant increase in rates of cancer.[47]

Coal tar contains many

squamous cell carcinoma.[13]

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.[13] 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.[17]

The

Group 1 carcinogens, meaning they directly cause cancer.[17][50][51] The U.S. Department of Health and Human Services lists coal tars as known human carcinogens.[52]

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.[53]

Other

Coal tar causes

increased sensitivity to sunlight,[54]
so skin treated with topical coal tar preparations should be protected from sunlight.

The residue from the

aromatic hydrocarbons, was listed on 13 January 2010 as a substance of very high concern by the European Chemicals Agency.[55]

Regulation

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

immediately dangerous to life and health.[56]

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

References

  1. PMID 18882998
    .
  2. ^ a b c d "Background and Environmental Exposures to Creosote in the United States" (PDF). cdc.gov. September 2002. p. 19. Archived (PDF) from the original on 25 January 2017. Retrieved 13 January 2017.
  3. ISBN 9789056990817
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  4. ^
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  5. ^
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    ISBN 9780471851455. Archived
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  7. ^ First Annual Report on Carcinogens. National Technical Reports Library. 1980.
  8. ISBN 9780471899792. Archived
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  9. ^ "History The Early Years (1863–1881)". Bayer AG. Retrieved 4 February 2021.
  10. ^
    hdl:10665/325771
    . WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO.
  11. ^ "Coal Tar use while Breastfeeding | Drugs.com". www.drugs.com. Archived from the original on 18 January 2017. Retrieved 13 January 2017.
  12. ^
    ISBN 9781607950394. Archived
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  13. ^
    ISBN 9780123864550
    . 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.
  14. doi:10.1021/ie50641a006
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  16. ^ "Public Health Statement for Creosote". Agency for Toxic Substances and Disease Registry. September 2002.
  17. ^ a b c d Coal-tar pitch (PDF). IARC. Archived (PDF) from the original on 21 May 2016. Retrieved 10 June 2017. 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
  18. ISBN 9780471238966
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  19. ^ "EUR-Lex - 32013R1272 - EN - EUR-Lex". eur-lex.europa.eu. Archived from the original on 2015-10-19. Retrieved 2017-06-10. ...are classified as carcinogens of category 1B in accordance with Annex VI to Regulation (EC) No 1272/2008 of the European Parliament
  20. ^ a b "COAL TAR - National Library of Medicine HSDB Database". toxnet.nlm.nih.gov. Archived from the original on 2017-05-28. Retrieved 2017-06-10.
  21. ^ Dronsfield A (1 July 2005). "Pain relief: from coal tar to paracetamol". Education in Chemistry. Vol. 42, no. 4. Royal Society of Chemistry. pp. 102–105. Archived from the original on 13 October 2017. Retrieved 14 June 2018.
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  24. ^ US EPA National Center for Environmental Assessment (15 March 2009). "Hematologic Disorders". hero.epa.gov. Retrieved 21 April 2020.
  25. ^ "WHO Model Prescribing Information: Drugs Used in Skin Diseases: Keratoplastic and keratolytic agents: Coal tar". apps.who.int. Archived from the original on 2017-04-20. Retrieved 2017-06-10. keratolytic agent that inhibits excessive proliferation of epidermal cells by reducing DNA synthesis and mitotic activity to normal levels
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  28. ^ a b Mahler BJ, Van Metre PC (2 February 2011). "Coal-Tar-Based Pavement Sealcoat, Polycyclic Aromatic Hydrocarbons (PAHs), and Environmental Health". U.S. Geological Survey Fact Sheet. Archived from the original on 2013-03-28. Retrieved 8 March 2013.
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  30. ^ "City of Austin Ordinance 20051117-070" (PDF). 17 November 2005. Archived (PDF) from the original on 2013-05-31. Retrieved 8 March 2013.
  31. ^ "District Bans Coal-Tar Pavement Products". 26 June 2009. Archived from the original on 2012-12-26. Retrieved 8 March 2013.
  32. ^ "Ordinance 80 : Establishing Regulations on Coal Tar Sealcoat Products Application and Sale" (PDF). Dane County Office of Lakes and Watersheds. 1 July 2007. Archived (PDF) from the original on 2011-08-24. Retrieved 8 March 2013.
  33. ^ "Coal Tar Free America – Bans". Archived from the original on 2014-10-06. Retrieved 8 March 2013.
  34. ^ Mahler BJ (14 April 2011). Causes of Increasing Concentrations of Polycyclic Aromatic Hydrocarbons (PAHs) in U.S. Lakes (PDF). PAHs Increasing in Urban U.S. Lakes. Environmental and Energy Study Institute. Archived from the original (PDF) on 5 October 2011. Retrieved 8 March 2013.
  35. ^ "Coal Tar Oil | OEC".
  36. ^ Hathaway AW (2011). Remediation of Former Manufactured Gas Plants and Other Coal-Tar Sites. Taylor & Francis Group.
  37. ISBN 978-0-85709-802-3
    . 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.
  38. ^ "CDC - Immediately Dangerous to Life or Health Concentrations (IDLH): Coal tar pitch volatiles - NIOSH Publications and Products". www.cdc.gov. 2018-11-02. Retrieved 2021-10-05.
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  42. ^ Smith M. "GANSG – Coal Tar Distillers". Igg.org.uk. Archived from the original on 2013-06-19. Retrieved 8 March 2013.
  43. ^ "Coal Tar use while Breastfeeding". Drugs.com. 2 June 2023. Archived from the original on 26 September 2023.
  44. ^ "The battle to save coal tar in California". 3 December 2001. Archived from the original on 2002-10-29. Retrieved 8 March 2013.
  45. ^ FDA (1 April 2015). "Drug Products for the Control of Dandruff, Seborrheic Dermatitis, and Psoriasis". Archived from the original on September 18, 2015. Retrieved 26 February 2016.
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  50. ^ IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. (2012). "Chemical Agents and Related Occupations.". Coal-Tar Pitch. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Lyon (FR): International Agency for Research on Cancer.
  51. ISBN 9789283214113. Archived
    (PDF) from the original on 2016-03-15. Evidence for carcinogenicity to humans (sufficient)
  52. ^ "Report on Carcinogens, Fourteenth Edition: Coal Tars and Coal-Tar Pitches" (PDF). National Toxicology Program, Department of Health and Human Services. Archived (PDF) from the original on 2017-02-01. Retrieved 2017-06-10.
  53. ^ Quirmbach C (7 February 2017). "Milwaukee Common Council Bans Coal Tar Sealants". Wisconsin Public Radio.
  54. ^ "Sun-Sensitive Drugs (Photosensitivity to Drugs)". MedicineNet. WebMD. 2008-08-22. p. 5. Archived from the original on 2013-03-17. Retrieved 8 March 2013.
  55. ^ "Candidate List of substances of very high concern for Authorisation". echa.europa.eu/home. nd. Retrieved 27 October 2021.
  56. ^ "CDC – NIOSH Pocket Guide to Chemical Hazards – Coal tar pitch volatiles". www.cdc.gov. Archived from the original on 2015-12-08. Retrieved 2015-11-27.

External links

Look up coal tar in Wiktionary, the free dictionary.
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