Polychlorinated naphthalenes

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General structural formula of PCN

Polychlorinated naphthalenes ( PCN ) are chlorinated hydrocarbons produced by the chlorination of naphthalenes . In 2015 they were included in Annexes A and C of the Stockholm Convention .

nomenclature

Structural formula of 2,3,6,7-tetrachloronaphthalene

The 75 isomeric PCNs are referred to in technology and toxicology with the abbreviation PCN-X , where X can stand for a number between 1 and 75. So called PCN-48 or PCN 48 the substance 2,3,6,7-tetrachloronaphthalene . Mixtures of PCN are often determined by stringing together the isomers they contain: PCN-33/34/37 , PCN 28/43 or PCN-38/40 .

properties

The general formula is C 10 H 8− (m + n) Cl m + n , where m + n can be at most 8. As with dioxins and polychlorinated biphenyls (PCB), various congeners of PCN exist . Of the 75 theoretically possible congeners with one to eight chlorine atoms, 67 were used in technical PCN products. Almost all products contained a mixture of different isomers.

use

PCN have an insecticidal and fungicidal effect and were therefore used in wood preservatives . On ships, they were used as an additive for waterproof metal paints. They were also used as substitutes for polychlorinated biphenyls in synthetic resins and sealing compounds, as flame retardants and as plasticizers . PCN were also used in smoke ammunition earlier. The possible consequences of emissions of PCN and similar substances from smoke ammunition into the environment is described in a document from the Swiss Army that was kept under lock and key for a long time : The ammunition used in smoke-drenching exercises during the Second World War led to the forced slaughter of 15,000 cattle due to severe symptoms of poisoning.

The estimated global production of PCN was 150,000 tons by 1998, with production in most countries having been severely restricted since 1970. In the countries of the UNECE ( United Nations Economic Commission for Europe ), production was completely stopped by the 1980s at the latest.

In 2015, PCNs were included in the Stockholm Convention as long-lived organic pollutants : under Annex A for the worldwide elimination of deliberate production and under Annex C for the worldwide minimization of the release as an undesirable by-product.

toxicity

Like other chlorinated hydrocarbons ( e.g. pentachlorophenol , polychlorinated dibenzodioxins and dibenzofurans ), PCNs can cause chlorine acne. Direct skin contact with chlorinated naphthalenes or their dust sublimates results in typical skin changes, nervousness, weight loss and anemia ; hepatic dystrophy is also possible with inhalation . To denote the consequences of the poisoning, the name Perna disease was coined in 1918, derived from perchloronaphthalene .

Tests with pigs, cows, rats and sheep showed that the toxicity increases with the number of chlorine atoms. Mono-, di- and trichlorinated compounds showed little or no toxicity, tetra- and higher-chlorinated naphthalenes, even in lower doses, led to systemic diseases up to and including death of the animals.

literature

Individual evidence

  1. ↑ Countries move forward on important issues for sustainable management of chemicals and waste: “[…] four new listings (three under the Stockholm and one under the Rotterdam Conventions - polychlorinated napthalenes, hexachlorobutadiene, and pentachlorophenol and its salts and esters; and methamidophos respectively ) ” , 2015.
  2. ↑ EEC human Toxome Project: Polychlorinated naphthalenes (PCNs) .
  3. ↑ Bogdal, Kohler, Schmid et al. a .: Polychlorinated naphthalenes: congener specific analysis and source identification in a dated sediment core from Lake Thun, Switzerland . In: Organohalogen Compounds , 68, pp. 300-303.
  4. ↑ Flame protection with unknown consequences . Empa press release , October 2, 2006.
  5. ↑ K. Lundgren: Properties and Analysis of Dioxin-Like Compounds in Marine Samples from Sweden. PhD thesis . University of Ottawa , 2003, urn : nbn: se: umu: diva-24 , full text (PDF, 900 kB).
  6. ^ A b UN Stockholm Convention .
  7. ↑ Perna disease. In: Roche Lexicon Medicine. 5th edition. Urban & Fischer, 2003, ISBN 3-437-15150-9 , p. 1436 (full text) .
  8. ↑ Ludwig Teleky: The pernary disease. In: Klinische Wochenschrift , April 30, 1927, p. 845. doi: 10.1007 / BF01728520 .
  9. ↑ E. Plassche, A. Schwegler: Polychlorinated naphthalenes, Preliminary Risk Profile . ( Memento from January 5, 2016 in the Internet Archive ) (PDF) Ministry of VROM / DGM, Netherlands 2002.