Talk:Polychlorinated naphthalene

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This article was created to document the uses and hazards of polychlorinated naphthalenes (PCNs). They have sometimes been lost in the waves of controversy over polychlorinated biphenyls (PCBs), although the PCNs entered industrial use somewhat earlier than PCBs and in some forms can be more hazardous. As compared to many other halogenated hydrocarbons PCNs were relatively easy to make, and that is probably why they were introduced early. By the 1950s industrial users were finding more effective products for many applications, although I do remember metal-cutting lubricants using them as late as the mid-1970s. It is fortunate that the more hazardous PCNs are solids at room temperature and do not usually disperse in the environment as readily as the liquid PCBs.

Regulation of PCNs is a topic that could benefit from additions to the article. Although PCNs were rapidly removed from U.S. industry, that development mostly occurred because of voluntary decisions by individual companies. U.S. regulations for PCNs are fairly general and weak. Japanese regulations, by contrast, although developed somewhat later, are more explicit and strict. European regulations are in between and focus more on waste handling than on industrial practice. (Quite possibly none of these regulations are being observed in Ukraine and perhaps elsewhere.) So far I have not been able to discover the status of PCN regulation in India, China, Malaysia or Indonesia, which are potentially important producers and consumers of PCNs.

Craig Bolon 16:20, 21 January 2006 (UTC)

Illustrating the continuing industry concerns with further regulating PCNs, even as waste, see the letter sent December 7, 2005, on behalf of the World Chlorine Council (WCC) to the United Nations Task Force on Persistent Organic Pollutants. Background for this letter is documented recognition of "dioxin-like potential" of PCNs coupled with long persistence of many PCN cogeners in the environment. Arguments advanced on behalf of the WCC trade association, contending that PCNs should not be further regulated, are that (1) there is little "in vivo" evidence of harm by PCNs to people, (2) most waste disposal of PCN products has already occurred, (3) peak rates of PCN release to the environment occurred around the 1940s, and (4) PCN residues are "extraordinarily low" and have been rapidly declining. The last of these arguments is countered by evidence in (Horii et al. 2004, see article) indicating that (1) peak residues occurred in the mid-1980s, (2) only moderate reductions in residue concentrations have occurred since, and (3) current PCN residue levels are more than 1,000 times those prior to the twentieth century. There is a substantial trend of work exploring toxicity of different PCNs, including (Puzyn & Falandysz 2004) cited in the article. Former PCN producers and industrial users evidently hope to avoid liability for products produced years ago.

Craig Bolon 19:52, 21 January 2006 (UTC)
 * It would be surprising if industry were deeply concerned about PCNs since they have not been produced for more than 30 years. The reviews on the topic are often speculative with much discussion on potential problems, even though these things look nasty.  The number of publications peaked in 2012.  A recent overview is http://dx.doi.org/10.1016/j.envint.2017.02.015, "Polychlorinated naphthalenes (PCNs) in food and humans".--Smokefoot (talk) 17:42, 3 November 2017 (UTC)