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More thorough treatise of all groups with similar actions and binding to aryl hydrocarbon receptor is given in
Dioxins and dioxin-like compounds Dioxins and dioxin-like compounds (DLCs) are a group of chemical compounds that are persistent organic pollutants (POPs) in the environment. They are mostly by-products of burning or various industrial processes - or, in case of dioxin-like PCBs ...
. Polychlorinated dibenzofurans (PCDFs) are a family of
organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
s with one or several of the hydrogens in the
dibenzofuran Dibenzofuran is a heterocyclic organic compound with the chemical structure shown at right. It is an aromatic compound that has two benzene rings fused to a central furan ring. All the numbered carbon atoms have a hydrogen atom bonded to each of t ...
structure replaced by chlorines. For example, 2,3,7,8-tetrachlorodibenzofuran (TCDF) has
chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
atoms substituted for each of the hydrogens on the number 2, 3, 7, and 8 carbons (see structure in the upper left corner of the second image). Polychlorinated dibenzofurans with chlorines at least in positions 2,3,7 and 8 are much more
toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a sub ...
than the parent compound dibenzofurane, with properties and chemical structures similar to
polychlorinated dibenzodioxins Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of long-lived polyhalogenated organic compounds that are primarily anthropogenic, and contribute toxic, persistent organic pollution in the environment. They are commonly ...
. These groups together are often inaccurately called
dioxin Dioxin may refer to: * 1,2-Dioxin or 1,4-Dioxin, two unsaturated heterocyclic 6-membered rings where two carbon atoms have been replaced by oxygen atoms, giving the molecular formula C4H4O2 * Dibenzo-1,4-dioxin, the parent compound also known ...
s. They are known developmental toxicants, and suspected human
carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive sub ...
s. PCDFs tend to co-occur with polychlorinated dibenzodioxins (PCDDs). PCDFs can be formed by
pyrolysis The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements '' ...
or incineration at temperatures below 1200 °C of chlorine containing products, such as PVC,
PCBs Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act in 1979 and internationally by t ...
, and other
organochloride An organochloride, organochlorine compound, chlorocarbon, or chlorinated hydrocarbon is an organic compound containing at least one covalently bonded atom of chlorine. The chloroalkane class (alkanes with one or more hydrogens substituted by chlo ...
s, or of non-chlorine containing products in the presence of chlorine donors. Dibenzofurans are known
persistent organic pollutants Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversel ...
(POP), classified among the ''dirty dozen'' in the
Stockholm Convention on Persistent Organic Pollutants Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed on 22 May 2001 in Stockholm and effective from 17 May 2004, that aims to eliminate or restrict the production and use of persistent organi ...
.


Congeners


Safety, toxicity, regulation

Occupational exposure to PCDFs may occur through inhalation and contact with the skin, although intake even in workers at waste incineration plants are not particularly high. For general population the most important source is food of animal origin like with other dioxin-like compounds.Tuomisto J (2019). Dioxins and dioxin-like compounds: toxicity in humans and animals, sources, and behaviour in the environment. WikiJournal of Medicine 6 (1): 8. doi:10.15347/wjm/2019.008. ISSN 2002-4436.Congener-Specific Levels of Dioxins and Dibenzofurans in U.S. Food and Estimated Daily Dioxin Toxic Equivalent Intake. The National Institute of Environmental Health Sciences (NIEHS). The most relevant congener is 2,3,4,7,8-pentachlorodibenzofuran (2,3,4,7,8-PCDF) which is more toxic and based on relative toxicity more prevalent than other PCDFs.


See also

*
Dioxins and dioxin-like compounds Dioxins and dioxin-like compounds (DLCs) are a group of chemical compounds that are persistent organic pollutants (POPs) in the environment. They are mostly by-products of burning or various industrial processes - or, in case of dioxin-like PCBs ...
*
Polychlorinated biphenyl Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act of 1976, Toxic Substances Contro ...


References

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Further resources


Synopsis on dioxins and PCBs

Chemical Profile: DIBENZOFURANS (CHLORINATED)


Chloroarenes Incineration Immunotoxins Dibenzofurans Persistent organic pollutants under the Convention on Long-Range Transboundary Air Pollution Persistent organic pollutants under the Stockholm Convention