New Polychlorinated Naphthalenes (PCNs)

PCNs are a group of 75 chlorinated naphthalenes, which are structurally similar to PCBs. Until the 1970s, PCNs were high-volume chemicals commercially produced as mixtures of several congeners marketed as Halowax, Nibren, and other commercial trade names. Total global production of PCNs was estimated at 150,000 metric tonnes until production ceased in Europe and North America in the 1980s. PCNs were mainly used as wood preservatives, paint and engine oil additives, cable insulation, and as a component in capacitors.

As would be expected from their commercial use, PCNs are very stable compounds that persist for long periods in the environment. With their fused diaromatic structure and mixed chlorination, PCNs are planar compounds which may exhibit characteristics similar to 2,3,7,8-tetrachlorodibenzo-p-dioxin and other “dioxin-like” compounds, including high chemical and thermal stability, bioaccumulation in fatty tissues, and toxicological effects in some congeners. As with many other dioxin-like compounds, their toxicity comes from the ability to bind to and activate the aryl hydrocarbon receptor (AhR).

In May 2011 the Stockholm Treaty committee members listed PCNs as chemicals they are considering for inclusion in a future revision of the treaty due to the harmful persistent organic pollutant (POP) properties and risks related to the possible continuing production, use, and release of PCNs to the environment.¹

Unlike many other dioxin-like compounds, very little information is available about occurrence and exposure to PCNs, especially for individual congeners. While several studies have looked at Halowax and other “technical” products, very little analysis has been done for congener-specific information. One of the difficulties with analysis of PCNs has been a dearth of analytical standards. After industrial usage decreased in the 1970s it appeared the PCN issue may fade away, but renewed testing, and the application for inclusion in the Stockholm Convention, has brought this group of compounds back to the forefront of environmental, food, and exposure analysis. While years ago only a small number of truly qualified individual congener standards were commercially available, CIL has recently developed many new standards, both unlabeled and ¹³C-labeled, to assist with developing methodologies and investigation of these revitalized compounds. Utilizing a combination of GC-MS and ¹H NMR testing protocols, CIL has incorporated quality practices to increase confidence in chemical identification, chemical purity, and identification of impurities which previously hindered older standards.

CIL is pleased to introduce many new individual PCN standards to enable improved analyses of a broader range of target PCN analytes. CIL has also formulated PCN mixtures designed for exposure analysis and other environmental analytical applications.

Polychlorinated Naphthalenes

References

1. Simon-Delso, N.; Amaral-Rogers, V.; Belzunces, L.P.; et al. 2014. Systemic insecticides (neonicotinoids and fipronil): trends, uses, mode of action and metabolites. Environ Sci Pollut Res Int, 22(1), 5-34. PMID: 25233913
2. Bloomquist, J.R. 2003. Chloride channels as tools for developing selective insecticides. Arch Insect Biochem Physiol, 54(4), 145-156. PMID: 14635176
3. Fipronil. May 1996. New Pesticide Fact Sheet. US EPA Office of Prevention, Pesticides and Toxic Substances. Read more.