Toxic substances list: pentachlorobenzene (QCB)

Pentachlorobenzene (QCB) is not currently produced or used in its pure form in Canada, and currently there is no domestic commercial demand for this substance. QCB is present as an impurity in several pesticides (herbicides and fungicides) currently in use in Canada. QCB is also contained as an impurity in pentachlorophenol, one of the main wood treatment pesticides that are used in Canada, also regulated under the Pest Control Products Act. In North America, the main use  for pentachlorophenol is for pressure or thermal treatment of utility poles,

QCBs may also be generated when organic compounds are burned or exposed to a large source of energy in the presence of a chlorine source. Through this mechanism, they may be formed and released to the environment as a result of waste incineration and barrel burning of household waste. Formerly, they could be found in dielectric fluids used to top up polychlorinated biphenyl (PCB) transformers and in dyestuff carriers. These applications have either been discontinued (dye carriers) or are being phased out (dielectric fluids). A possible source of release may include dielectric PCB material still in use.

CAS (Chemical Abstracts Service) registry number: 608-93-5

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

Risk assessment


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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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