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Pentachlorobenzene - PSL1

1.0 Introduction

The Canadian Environmental Protection Act (CEPA) requires the federal Ministers of the Environment and of Health to prepare and publish a Priority Substances List that identifies substances, including chemicals, groups of chemicals, effluents and wastes that may be harmful to the environment or constitute a danger to human health. The Act also requires both Ministers to assess these substances and determine whether they are "toxic" as defined in section 11 of the Act which states:

"... a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions

1. having or that may have an immediate or long-term harmful effect on the environment;
2. constituting or that may constitute a danger to the environment on which human life depends; or
3. constituting or that may constitute a danger in Canada to human life or health."

Substances assessed as "toxic" according to section 11 may be placed on Schedule I of the Act, and considered for possible development of regulations, guidelines or codes of practice to control any aspect of their life cycle, from the research and development stage through manufacture, use, storage, transport and ultimate disposal.

The assessment of whether pentachlorobenzene is "toxic", as defined under CEPA, was based on the determination of whether it enters or is likely to enter the Canadian environment in a concentration or quantities or under conditions that could lead to exposure of humans or other biota at levels that could cause adverse effects.

The assessment of whether pentachlorobenzene is "toxic" to human health under CEPA, is based principally on documentation prepared by staff of Health Canada for the International Programme on Chemical Safety (IPCS). Between 1984 and 1987, original data relevant to the assessment of risks to health associated with exposure to the chlorinated benzenes (excluding hexachlorobenzene) were reviewed by staff of Health Canada in the preparation of a draft IPCS Environmental Health Criteria Document (EHC). The current assessment has been updated and expanded to emphasize data most relevant to the assessment of the risks associated with exposure to pentachlorobenzene in the general environment in Canada.

In preparation of the IPCS document, a wide variety of scientific databases were searched to update information provided in earlier contractors' reports including an annotated bibliography on the chlorobenzenes (excluding hexachlorobenzene) by Peter Strahlendorf (1978) and a criteria document on chlorobenzenes (including hexachlorobenzene) by Michael Holliday and Associates (1984a; 1984b). Additional information was identified during peer review of the draft Environmental Health Criteria Document by IPCS focal points and a task group of experts which met in June 1990. More recently, in February 1991, a search was conducted of ENVIROLINE, Chemical Abstracts, Pollution Abstracts, Environmental Bibliography, IRIS, MEDLINE, and BIOSIS databases to identify recent data relevant to assessment in particular of the risks to the population of Canada. Data relevant to assessment of whether pentachlorobenzene is "toxic" to human health obtained after completion of these sections of this report (March 1992) were not considered for inclusion.

Information considered relevant to the assessment of whether pentachlorobenzene is "toxic" to the environment was identified from on-line searches completed in November 1990 of ASFA, BIOSIS, CAB Abstracts, Chemical Abstracts, CESARS, CIS, ENVIROLINE, Hazardous Substances, and IRPTC databases. A summary of information on the environmental toxicity, fate and levels of pentachlorobenzene in the Canadian environment, prepared under contract by Diane Koniecki (November 1991) was also consulted in the preparation of this report. In formation received after March 1993 was not included in the environmental sections of this report.

Although review articles were consulted where considered appropriate, original studies that form the basis for the determination of "toxic" under CEPA were critically evaluated by staff of Health Canada (human exposure and effects on human health) and Environment Canada (entry and environmental exposure and effects). The following officials contributed to preparation of the report:

A.M. Bobra (Environment Canada)
D. Boersma (Environment Canada)
L. Brownlee (Environment Canada)
M Giddings (Health Canada)
R. Gomes (Health Canada)
K.M. Lloyd (Environment Canada)
M.E. Meek (Health Canada)

B. Idris and R.G. Liteplo of Health Canada also contributed to the consolidation of the Assessment Report.

In this report, a synopsis that will appear in the Canada Gazette is presented. A summary of the technical information that is critical to the assessment, and which is presented in greater detail in unpublished Supporting Documentation, is presented in Section 2.0. The assessment of whether pentachlorobenzene is "toxic", as defined under CEPA, is presented in Section 3.0.

As part of the review and approvals process established by Environment Canada, the environmental sections of this Assessment Report were reviewed by the following: B. Oliver (Zenon Environmental Laboratories); M. Rankin (Dow Chemical Canada Inc.); and H. Rogers (Department of Fisheries and Oceans, Institute of Ocean Sciences). Sections related to the effects on human health were approved by the Standards and Guidelines Rulings Committee of the Bureau of Chemical Hazards of Health Canada. The entire Assessment Report was reviewed and approved by Environment Canada and Health Canada's CEPA Management Committee.

Copies of this Assessment Report and the unpublished Supporting Documentation are available upon request from the following: