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Canada - Final Regulatory Action
Pentachlorobenzene CAS number:
Date circular:

Chemical name: Benzene, pentachloro-

Final regulatory action has been taken for the category: Industrial

Final regulatory action: The chemical is Severely Restricted

Use or uses prohibited by the final regulatory action:

The Regulations prohibit the manufacture, use, sale, offer for sale or import of QCB, with the exception listed below

Use or uses that remain allowed:

The Regulations do not apply to any use of QCB with any chlorobiphenyls that have the molecular formula C12H(10-n)Cln in which "n" is greater than 2.

The final regulatory action was based on a risk or hazard evaluation: Yes

Summary of the final regulatory action:

The Prohibition of Certain Toxic Substances Regulations, 2005 prohibit the manufacture, use, sale, offer for sale and import of toxic substances listed in Schedules 1 and 2 to the Regulations. QCB is found in Schedule 2, which lists substances that are subject to prohibitions related to concentration or use.

The reasons for the final regulatory action were relevant to: Environment

Summary of known hazards and risks to the environment:

QCB appeared on the first Priority Substances List (PSL1) of the original Canadian Environmental Protection Act (CEPA). PSL1 was published in the Canada Gazette, Part I, on February 11, 1989. Assessments were performed to determine whether these chlorobenzenes (CBzs) should be considered toxic as defined under CEPA, and were completed in 1993. Section 11 of CEPA defined toxic as follows: For the purposes of this Part, a substance is toxic if it is entering or may enter the environment in a quantity, concentration or under conditions
a)having or that may have an immediate or long-term effect on the environment;
b)constituting or that may constitute a danger to the environment on which human life depends; or
c)constituting or that may constitute a danger in Canada to human life or health.
It was concluded at that time that these substances do not constitute a danger either to the environment on which human life depends or to human life or health, and, therefore, they were not found to be toxic under Paragraph 11(b) or 11(c) of CEPA.
Additionally, during the period over which the original assessments were conducted, it was determined that concentrations of QCB present in Canadian air and surface waters were not likely to cause adverse effects on aquatic biota or wildlife. There was, however, a lack of acceptable data on the effects of these CBzs on benthic and soil-dwelling organisms and on concentrations of CBzs in Canadian soils. Therefore, it was not possible to determine whether environmental harm was occurring due to accumulations of these substances in sediment and soil.
The lack of data led to the conclusion that there was insufficient information available on sediments and soils to determine whether these substances should be considered toxic under Paragraph 11(a) of CEPA. CEPA was subsequently revised in 1999. Paragraph 64(a) of CEPA 1999 expands the definition of toxic from the original Paragraph 11(a) to include effects on biodiversity. CEPA 1999 places more emphasis on pollution prevention, gives consideration to the precautionary principle and requires special treatment of persistent and bioaccumulative substances. Substances that are shown to be both persistent and bioaccumulative, therefore, are assessed using a more conservative approach than is used for other substances.
As a result of the publication of the PSL Assessment Reports for the CBzs, additional studies were designed and funded. Concentrations of QCB were determined in sediments near point sources (i.e., outfalls from sewage treatment plants and textile manufacturing plants) in Atlantic Canada. Laboratory studies included toxicity testing to determine effects of exposure to sediments from point source locations.
A literature search for new data on the CBz substances of interest was performed in 1995 and repeated in 1999. The National Pollutant Release Inventory (NPRI) and Accelerated Reduction/Elimination of Toxics databases supported by Environment Canada were also reviewed for CBz data.
The focus of the follow up report was the determination of whether accumulations of specific CBzs in aquatic sediments or soils would harm exposed benthic or soil-dwelling organisms.
QCB was identified in sediments from lakes in both temperate regions and northern Canadian environments. The detection of the QCB in northern lake sediments in the absence of nearby sources indicated that these residues are a result of long-range atmospheric transport, and therefore, meet the criteria for persistence in air.
Mean half-lives in soil were estimated to be approximately 2 years for QCB, therefore, likely to persist in soils under aerobic conditions.
On the basis of the available information, it was concluded that QCB is persistent in soil, sediment and in air, according to the criteria stipulated in the Persistence and Bioaccumulation Regulations of CEPA 1999.
Bioaccumulation factors (BAFs) of 810 and 20 000 were reported for QCB in mussel (Mytilis edulis) and rainbow trout, respectively, although the BAF determined for earthworms (Eisenia andrei) was much higher (401 000). The log Kow estimates for QCB was 5.0. QCB is also a bioaccumulative substance according to the criteria stipulated in the Persistence and Bioaccumulation Regulations of CEPA 1999.
It was concluded that concentrations of QCB in Canadian soil are unlikely to be causing harm to populations of soil-dwelling organisms. However, it was possible that concentrations of QCB in sediment from the St. Clair River near Sarnia may have been harming benthic organisms.
Based on available data, QCB was found to be entering the environment in a quantity or concentration or under conditions that had or may have had an immediate or long-term harmful effect on the environment or its biological diversity and that QCB is considered toxic, as defined under Paragraph 64(a) of CEPA 1999.

Expected effect of the final regulatory action in relation to the environment:

QCB is persistent, bioaccumulative, predominantly anthropogenic and is considered toxic under CEPA 1999, and as such, meet the criteria for Track I substances under Canada's Toxic Substances Management Policy. Therefore the Canadian federal government proposed that QCB be subjected to virtual elimination provisions of CEPA 1999. The prohibition on manufacture, use, sale, offer for sale, or import of QCB, will work towards the objective of virtual elimination.

Date of entry into force of the final regulatory action: 09/02/2007