Polychlorinated dibenzofurans (PCDFs) are a family of

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s with one or several of the hydrogens in the

dibenzofuran Dibenzofuran (DBF) 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 ...

structure replaced by chlorines. For example, 2,3,7,8-tetrachlorodibenzofuran (TCDF) has

chlorine Chlorine is a chemical element; it has Symbol (chemistry), 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 ...

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 subst ...

than the parent compound dibenzofuran, 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 a number of different substances. Most notably: * 1,2-Dioxin or 1,4-dioxin, two unsaturated heterocyclic 6-membered rings in which two carbon atoms have been replaced by oxygen atoms, which gives the molecular formula C4H4O2 ...

s. They are known developmental toxicants, and suspected human

carcinogen A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruse ...

s. PCDFs tend to co-occur with

polychlorinated dibenzodioxin Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of long-lived polyhalogenated compound, polyhalogenated organic compounds that are primarily anthropogenic, and contribute toxic, Persistent organic pollutant, persistent or ...

s (PCDDs). PCDFs can be formed by

pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...

or incineration at temperatures below 1200 °C of chlorine containing products, such as

PVC Polyvinyl chloride (alternatively: poly(vinyl chloride), colloquial: vinyl or polyvinyl; abbreviated: PVC) is the world's third-most widely produced synthetic polymer of plastic (after polyethylene and polypropylene). About 40 million tons o ...

PCBs Polychlorinated biphenyls (PCBs) are organochlorine compounds with the formula C12 H10−''x'' Cl''x''; they were once widely used in the manufacture of carbonless copy paper, as heat transfer fluids, and as dielectric and coolant fluids f ...

, and other

organochloride Organochlorine chemistry is concerned with the properties of organochlorine compounds, or organochlorides, organic compounds that contain one or more carbon–chlorine bonds. The chloroalkane class (alkanes with one or more hydrogens substituted ...

s, or of non-chlorine containing products in the presence of chlorine donors. Dibenzofurans are known

persistent organic pollutants Persistent organic pollutants (POPs) are organic compounds that are resistant to degradation through chemical, biological, and photolytic processes. They are toxic and adversely affect human health and the environment around the world. Becaus ...

(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 is 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.

References

Further resources

Synopsis on dioxins and PCBs

Chemical Profile: DIBENZOFURANS (CHLORINATED)

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

Congeners

Safety, toxicity, regulation

See also

References

Further resources