Polychlorinated naphthalene (PCN) are the products obtained upon treatment of

naphthalene Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromati ...

with

chlorine Chlorine is a chemical element with the 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 betwee ...

. The generic

chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...

is C₁₀ H_8−(m+n) Cl_(m+n). Commercial PCNs are mixtures of up to 75 components and byproducts.van de Plassche, E.; Schwegler, A. (2002)
''Polychlorinated naphthalenes, Preliminary Risk Profile
''Ministry of VROM/DGM, Netherlands The material is an oil or a waxy solid, depending on the degree of chlorination. PCNs were once used in insulating coatings for electrical wires, as well as other applications, but their use has been largely phased out.

Chemical structure of PCN congeners

There are 75 different PCN congeners.

Production

PCNs started to be produced for high-volume uses around 1910 in both Europe and the United States.Chlorinated naphthalenes
, Chemical Assessment Report S48, 2002, National Industrial Chemicals Notification and Assessment Scheme In Europe the largest volume products were called Nibren waxes, made in Germany by

Bayer Bayer AG (, commonly pronounced ; ) is a German multinational corporation, multinational pharmaceutical and biotechnology company and one of the largest pharmaceutical companies in the world. Headquartered in Leverkusen, Bayer's areas of busi ...

. Other European PCN tradenames included Seekay (UK, from ICI), Clonacire (France), Cerifal (Italy) and Woskol (Poland). In the United States, the largest volume PCN products were called Halowax, from a New York company of the same name that was later owned by

Union Carbide Union Carbide Corporation is an American chemical corporation wholly owned subsidiary (since February 6, 2001) by Dow Chemical Company. Union Carbide produces chemicals and polymers that undergo one or more further conversions by customers befor ...

and then taken over by

Koppers Koppers is a global chemical and materials company based in Pittsburgh, Pennsylvania, United States in an art-deco 1920s skyscraper, the Koppers Tower. Structure Koppers is an integrated global producer of carbon compounds, chemicals, and trea ...

of Pittsburgh, PA, now Beazer East. Although trace amounts of PCNs may be released by natural processes such as wildfires, their industrial uses increased the apparent rates of accumulation in the environment by factors of 10,000 or more.

Safety

After about 20 years of commercial production, health hazards began to be reported in workers exposed to PCNs:

chloracne Chloracne is an acne-like eruption of blackheads, cysts, and pustules associated with exposure to certain halogenated aromatic compounds, such as chlorinated dioxins and dibenzofurans. The lesions are most frequently found on the cheeks, behind ...

, severe skin rashes and

liver disease Liver disease, or hepatic disease, is any of many diseases of the liver. If long-lasting it is termed chronic liver disease. Although the diseases differ in detail, liver diseases often have features in common. Signs and symptoms Some of the sig ...

that led to deaths of workers.Chronic exposure increases risk of liver disease. Se
Chlorinated naphthalenes exposure
Worker Notification Program,

National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...

A conference about the hazards was organized at

Harvard School of Public Health The Harvard T.H. Chan School of Public Health is the public health school of Harvard University, located in the Longwood Medical Area of Boston, Massachusetts. The school grew out of the Harvard-MIT School for Health Officers, the nation's first ...

in 1937, and several more publications dealing with PCN hazards appeared before 1940. PCNs containing three or more chlorines per molecule have typically been found more hazardous than those with fewer, but as the maximum of eight is approached, hazards appear to decrease.Chlorinated naphthalenes
International Programme on Chemical Safety CICAD, 2001, volume 34 There was a lag of about 40 years between disclosure of PCN hazards and government regulation. In the U.S. exposure to PCNs was drastically reduced after 1976, following enactment of the

Toxic Substances Control Act The Toxic Substances Control Act (TSCA) is a United States law, passed by the 94th United States Congress in 1976 and administered by the United States Environmental Protection Agency (EPA), that regulates chemicals not regulated by other U.S. ...

. Major equipment manufacturers banned PCNs in their products, and major PCN producers discontinued operations. By 1983 worldwide PCN production had almost halted except for small amounts used in testing and research. Until recent years

duPont DuPont de Nemours, Inc., commonly shortened to DuPont, is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours. The company played a major role in ...

produced a synthetic rubber,

Neoprene Neoprene (also polychloroprene) is a family of synthetic rubbers that are produced by polymerization of chloroprene.Werner Obrecht, Jean-Pierre Lambert, Michael Happ, Christiane Oppenheimer-Stix, John Dunn and Ralf Krüger "Rubber, 4. Emulsion R ...

FB, made in

Northern Ireland Northern Ireland ( ga, Tuaisceart Éireann ; sco, label= Ulster-Scots, Norlin Airlann) is a part of the United Kingdom, situated in the north-east of the island of Ireland, that is variously described as a country, province or region. Nort ...

using pentachloronaphthalene.Neoprene FB
, Material Safety Data Sheet, DuPont de Nemours & Co., 1985 Increased cancer risks have been suspected but so far not shown. Current concerns about PCNs include their release as byproducts of waste incineration.

Bioaccumulation

In 2013, the 9th meeting of the Persistent Organic Pollutants Review Committee, established under 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 organic ...

proposed di-,tri-,tetra-,penta-,hexa-, hepta- and octa-chlorinated napthalenes, for listing in Annexes A and C to that Convention.UNEP (2013)
Risk management evaluation on chlorinated naphthalenes
Report of the Persistent Organic Pollutants Review Committee on the work of its ninth meeting, Rome, 14–18 October 2013 (Addendum) While some PCNs can be broken down by sunlight and, at slow rates, by certain microorganisms, many PCNs persist in the environment. After more than 80 years of use and total production of several hundred thousand tons, PCN residues are widespread.

References

Literature

* Eva Jakobsson, Lillemor Asplund:
Polychlorinated Naphthalenes (PCNs)
', in ''The Handbook of Environmental Chemistry'', Volume 3K, 2000, p. 97–126, , {{doi, 10.1007/3-540-48915-0_5 Chloroarenes Naphthalenes Persistent organic pollutants under the Stockholm Convention