Toxic substances list: Polychlorinated terphenyls

Polychlorinated terphenyls (PCTs) are yellow resins with characteristics similar to those of Polychlorinated Biphenyls (PCBs), such as extremely high resistance to thermal breakdown, heat stability and non-flammability, making them useful for industrial purposes. PCTs have been used as PCB substitutes and both in closed systems, such as electric transformers, and open-ended applications, such as lubricating and cutting oils.

PCT production occurred over the same period as PCB production, although production quantities of PCBs were 15-20 times those of PCTs. Between 1955-1980, total global production of PCTs is estimated to have reached 60 000 metric tonnes. PCTs have never been produced in Canada but were imported and used commercially. Total import quantities remain unknown. Documented historical uses of PCTs in Canada were as pressure-sensitive adhesive for weatherstrip backing, as plasticizers for urethanes, and in paints. By 1976, commercial use of more than 1 kg of either PCTs or PCBs was required to be reported under the former Environmental Contaminants Act. Three companies replied to the reporting notice, indicating that all uses of PCTs were terminated in the mid-1970s.

For information on Canada's international engagement on this substance, please visit:

CAS (Chemical Abstracts Service) registry number: 61788-33-8

Note: There is more than one CAS number that applies to this group of substances.

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Substances Management Information Line
Chemicals Management Plan
Gatineau, QC K1A 0H3

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


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