Polychlorinated biphenyl

"PCBs" redirects here. For other uses, see PCB (disambiguation).
Polychlorinated biphenyl

Chemical structure of PCBs. The possible positions of chlorine atoms on the benzene rings are denoted by numbers assigned to the carbon atoms.
Identifiers
ECHA InfoCard 100.014.226 Edit this at Wikidata
UN number UN 2315
Properties
C12H10−xClx
Molar mass Variable
Appearance Light yellow or colorless, thick, oily liquids[1]
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
2
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
PCB warning label on a power transformer known to contain PCBs

Polychlorinated biphenyls (PCBs) are organochlorine compounds with the formula C12H10−xClx; they were once widely used in the manufacture of carbonless copy paper, as heat transfer fluids, and as dielectric and coolant fluids for electrical equipment.[2] They are highly toxic and carcinogenic chemical compounds, formerly used in industrial and consumer electronic products, whose production was banned internationally by the Stockholm Convention on Persistent Organic Pollutants in 2001.

Because of their longevity, PCBs are still widely in use, even though their manufacture has declined drastically since the 1960s, when a host of problems were identified.[3] With the discovery of PCBs' environmental toxicity, and classification as persistent organic pollutants, their production was banned for most uses by United States federal law on January 1, 1978.

The International Agency for Research on Cancer (IARC) rendered PCBs as definite carcinogens in humans. According to the U.S. Environmental Protection Agency (EPA), PCBs cause cancer in animals and are probable human carcinogens.[4] Moreover, because of their use as a coolant in electric transformers, PCBs still persist in built environments.[5][6]

Some PCBs share a structural similarity and toxic mode of action with dioxins.[7] Other toxic effects such as endocrine disruption (notably blocking of thyroid system functioning) and neurotoxicity are known.[8] The bromine analogues of PCBs are polybrominated biphenyls (PBBs), which have analogous applications and environmental concerns.

An estimated 1.2 million tons have been produced globally.[9] Though the US EPA enforced the federal ban as of 1978, PCBs continued to create health problems in later years through their continued presence in soil and sediment, and from products which were made before 1979.[10] In 1988, Japanese scientists Tanabe et al. estimated 370,000 tons were in the environment globally, and 780,000 tons were present in products, landfills, and dumps or kept in storage.[9]

  1. ^ "Hazardous Substance Fact Sheet" (PDF). New Jersey Department of Health.
  2. ^ Rossberg M, Lendle W, Pfleiderer G, et al. (2006). "Chlorinated Hydrocarbons". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a06_233.pub2. ISBN 3527306730.
  3. ^ Robertson LW, Hansen LG, eds. (2004). PCBs: Recent advances in environmental toxicology and health effects. Lexington, KY: University Press of Kentucky. p. 11. ISBN 978-0813122267.
  4. ^ "Health Effects of PCBs". Washington, D.C.: U.S. Environmental Protection Agency (EPA). 2016-09-15.
  5. ^ Current intelligence bulletin 45 – polychlorinated biphenyls (PCB's): potential health hazards from electrical equipment fires or failures (with reference package) (Report). 2020-09-29. doi:10.26616/NIOSHPUB86111.
  6. ^ "Identification, Management, and Proper Disposal of PCB-Containing Electrical Equipment used in Mines" (PDF). Environmental Protection Agency. Archived (PDF) from the original on 2022-01-10.
  7. ^ "Dioxins and PCBs". European Food Safety Authority. Retrieved 13 October 2015.
  8. ^ Boas M, Feldt-Rasmussen U, Skakkebaek NE, Main KM (May 2006). "Environmental chemicals and thyroid function". European Journal of Endocrinology. 154 (5): 599–611. doi:10.1530/eje.1.02128. PMID 16645005.
  9. ^ a b Gupta RC (2011). "41 Polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans". Reproductive and Developmental Toxicology. London: Academic Press. ISBN 978-0-12-382033-4. OCLC 717387050.
  10. ^ Cite error: The named reference healthafter was invoked but never defined (see the help page).