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Polychlorinated Naphthalenes​

Polychlorinated naphthalenes (PCNs) are a series of chemical compounds that were used previously for industrial applications such as capacitor and cable insulation, chlor-alkali production, and in the formulation of PCBs. They were also used as an engine oil additive and for the preservation of wood, paper and textiles.

PCNs have not been produced purposefully in Canada since the 1980s and are not available commercially, but they can still be unintentionally produced and emitted during metal refinements and as combustion by-products.

Though their use has largely been phased out in Canada, they are still present in some places in the environment due to their persistent nature, and have the potential for ecological damage.

In the Lake Simcoe watershed, a recent study showed that PCNs were associated with more urbanized areas.

  1. What are polychlorinated naphthalenes (PCNs)?
  2. Mobility and fate of PCNs in the environment
  3. Environmental impacts
  4. PCNs in Ontario and the Lake Simcoe watershed
  5. Actions to reduce PCNs in the environment
  6. References

What are polychlorinated naphthalenes (PCNs)?

Polychlorinated naphthalenes (PCNs) are a series of chemical compounds that are derived from the treatment of naphthalene with chlorine. PCNs were mainly produced in the form of technical mixtures, often for industrial applications such as capacitor and cable insulation, chlor-alkali production and in the formulation of PCBs (though the manufacture of PCBs has long been prohibited in Canada). They were also used as an engine oil additive and for the preservation of wood, paper and textiles. PCNs have not been produced intentionally in Canada since the 1980's (Helm et al., 2006) and are not currently available commercially [Environment Canada (EC), 2013b], but they can still be unintentionally produced during metal refinements and as combustion by-products (e.g. incineration). Trace amounts of PCNs can occur from natural processes such as wildfires.

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Mobility and fate of PCNs in the environment

Though their use has largely been phased out in Canada, some PCN compounds are still detected in the environment due to their persistent nature, with the highest levels occurring near previous point sources. However, their detection in both the Arctic and Antarctica suggest that PCNs are both persistent and subject to long range transport (EC, 2013b).  Due to their persistence and potential to bioaccumulate PCNs are listed under the Stockholm Convention as one of the new persistent organic pollutants (POPs; Stockholm Convention, 2008).

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Environmental impacts

In aquatic ecosystems PCNs can be toxic to aquatic organisms resulting in increased mortality as well as impacting various lifecycle stages.  Due to the potential for PCNs to bioaccumulate, adverse effects of PCN exposure can move up the aquatic food chain as well as to bird or mammal species that predate aquatic species (EC, 2013b).

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PCNs in Ontario and the Lake Simcoe watershed

In Ontario, PCNs were measured in sediment as part of the Southern Ontario Stream Sediment Project (SOSSP), and were reported as the sum of 22 congeners (each having differing numbers of chlorine atoms; tri to octa –chlorinated naphthalene homologue groups) (Chaudhuri et al., 2017).  Sediment samples collected in the Lake Simcoe watershed as part of this study found the highest PCN levels were associated with more urbanized areas, including in the Tannery Creek downstream of the Town of Aurora.  Comparable levels, or much higher, were found in other highly populated areas of Southern Ontario, including at sites in the GTA and near Kitchener, Windsor Brockville and Pembroke (Chaudhuri et al., 2017). Sediment quality guidelines are not currently available for PCNs in Canada.

The lowest levels in the Lake Simcoe watershed were observed in more naturalized or rural areas, such as Upper Talbot River.

PCNs have been measured in fish of the Great Lakes, with the highest concentrations occurring where sediment levels were highest (i.e., the Detroit River; Helm et al., 2006; Marvin et al., 2002). PCNs are included as a potential contaminant in the Guide to Eating Ontario Fish (2017-2018), but it was not listed in fish consumption advisories for Lake Simcoe and some of its tributaries [Ministry of Environment and Climate Change (MOECC), 2017].

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Actions to reduce PCNs in the environment

A Proposed Risk Management approach has been developed in Canada for the regulation of PCN compounds. The approach is supported by restrictions on the manufacture, use, import or sale of PCNs as outlined in the Prohibition of Certain Toxic Substances Regulations (EC, 2013b; ECCC, 2018).

The Government of Canada may regulate unintentional releases as well, with more understanding developed from ongoing monitoring studies.  Ultimately, it is proposed that PCNs be added to the Virtual Elimination List because of adverse effects in the Canadian environment (specifically persistence and bioaccumulation) as outlined under the Canadian Environmental Protection Act (CEPA; 1999; EC, 2013a). Monitoring PCNs in the environment occurs under the Chemicals Management Plan and this will aid in directing further regulatory action required for PCNs.​​

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References

Chaudhuri SR, Dyer RD, Fletcher R, Helm P, Millar M, Reiner EJ and Welsh PG. 2017. Southern Ontario Stream Sediment Project (SOSSP) summary report—Organic contaminants (Ontario Geological Survey, Open File Report 6335). Toronto, Ontario: Queen's Printer for Ontario.

Environment Canada (EC). 2013a, March 7. Virtual elimination list. Retrieved from: https://www.canada.ca/en/environment-climate-change/services/canadian-environmental-protection-act-registry/substances-list/virtual-elimination-list/updated-february-4-2009.html

EC. 2013b, June 19. Proposed risk management approach for polychlorinated naphthalenes (PCNs).  Retrieved from: https://www.ec.gc.ca/ese-ees/default.asp?lang=En&n=BB874604-1

ECCC. 2018, March 20. Prohibition of certain toxic substances regulations, 2012. Retrieved from: https://pollution-waste.canada.ca/environmental-protection-registry/regulations/view?Id=114

Helm PA, Bidleman T, Jantunen TF and Ridal J. 2000. Polychlorinated naphthalenes in Great Lakes Air: Source and ambient air profiles. Organohologen Compds. 47: 17-20.

Helm PA, Kurunthachalam K and Bidleman TF. 2006. Polychlorinated naphthalenes in the Great Lakes. In: RA Hites (Ed.), Persistent organic pollutants in the Great Lakes. The handbook of environmental chemistry, vol. 5N. Berlin, Heidelberg, Germany: Springer.

Marvin C, Alaee M, Painter S, Charlton M, Kauss P, Kolic T, MacPherson K, Takeuchi D and Reiner E. 2002. Persistent organic pollutants in Detroit River suspended sediments: Polychlorinated debenzo-p-dioxxins and dibenzofurans, dioxin-like polychlorinated biphenyl and polychlorinated naphthalenes. Chemosphere 49: 111-120.

Ministry of Environment and Climate Change (MOECC). 2017, October 26. Eating Ontario Fish (2017-2018). Retrieved from: https://www.ontario.ca/page/eating-ontario-fish-2017-18

Stockholm Convention, 2008. The new POPs under the Stockholm Convention. Retrieved from: http://chm.pops.int/TheConvention/ThePOPs/TheNewPOPs/tabid/2511/Default.aspx

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