Toxic substances list: polychlorinated naphthalenes (PCNs)

Chlorinated naphthalenes are industrial chemicals that have not been in commercial use in Canada for more than twenty years, but may be produced unintentionally as a by-product of various industrial processes involving chlorine, especially in the presence of heat. There are 75 possible chlorinated naphthalenes, which are divided into eight groups based on the number of chlorine atoms in the molecule (referred to with prefixes mono- to octa-).

Chlorinated naphthalenes were likely never manufactured in Canada but were previously imported from foreign manufacturers for industrial uses including cable insulation, capacitors, gauge and heat exchange fluids, instrument seals and solvents.

Environment Canada has conducted a science-based evaluation of Chlorinated Naphthalenes called a screening assessment. Ecological screening assessments address the potential for harm to the environment. The final screening assessment report, published on July 2, 2011, concluded that chlorinated naphthalenes with 2 to 8 chlorine atoms (herein referred to as Polychlorinated Naphthalenes or PCNs) are entering or may be entering the environment in a quantity or a concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity. Furthermore, the available data regarding these substances’ persistence and bioaccumulation potential indicate that they satisfy the criteria outlined in the Persistence and Bioaccumulation Regulations, under the Canadian Environmental Protection Act 1999, and meet all other criteria to implement virtual elimination. However, it is proposed that mono-chlorinated naphthalene is not entering the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to the environment.

The Risk Management Approach for PCNs, published on July 2, 2011, outlines the proposed risk management actions. Proposed in the Risk Management Approach are prohibitions on the manufacture, use, sale, offer for sale or import of PCNs and products containing them. It is proposed that these restrictions would be achieved by adding PCNs to the Prohibition of Certain Toxic Substances Regulations.

On January 2, 2013, the Prohibition of Certain Toxic Substances Regulations, 2012 were published in the Canada Gazette, Part II, including controls for PCNs.

For more information on this substance, please visit the Chemical Substances website.

CAS (Chemical Abstracts Service) registry number: 70776-03-3

Risk assessment

Risk management

Click on the following link to view strategies and actions recommended to manage risks associated with the substance:

Risk management tools

Tools developed to manage risks associated with the substance:


Consultation (past and present) on the substance:


Chemicals Management Division
Environment and Climate Change Canada
Gatineau, QC K1A 0H3


Substances Management Information Line:
Telephone: 1-800-567-1999 (in Canada) or 819-938-3232
Fax: 819-938-3231


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