Priority Substances List Assessment Report for Hexachlorobutadiene

1.0 Introduction

The Canadian Environmental Protection Act, 1999 (CEPA 1999) requires the federal Ministes of the Environment and of Health to prepare and publish a Priority Substances List (PSL) that identifies substances, including chemical, groups of chemical, effluents and wastes, that may be harmful to the environment or constitue a danger to human health. The Act also requires both Ministers to assess these substances and determine whether they are "toxic" or are capable of becoming "toxic" as defined in Section 64 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 that

1. have or may have an immediate or long-term harmful effect on the environment or its biological diversity;
2. constitute or may constitute a danger to the environemtn on which life depends or;
3. constiture or may constitute a danger in Canada to human life or health.

Substances that are assessed as "toxic" as defined under Section 64 may be placed on Schedule 1 of the Act and considered for possible risk management measures, such as regulations, guidelines, pollution prevention plans 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. Substances on Schedule 1 that are persistent and bioaccumulative in accordance with the Persistence and Bioaccumulation Regulations of CEPA 1999, are present in the environment primarily as a result of human activity and are not naturally occurring radionuclides or naturally occurring inorganic substances must be proposed, under Subsection 77(4), for the implementation of virtual elimination under Subsection 65(3).

Based on initial screening of readily accessible information, the rationale for assessing hexachlorobutadiene (HCBD) provided by the Ministers' Expert Advisory Panel on the Second Priority Substances List (Ministers' Expert Advisory Panel, 1995) was as follows:

HCBD is used as a solvent for elastomers, as a heat transfer liquid, in transformer and hydraulic fluids, and as a wash for removing volatile organic chemicals from organic streams. HCBD has been found in refuse combustion emissions and in process effluents from various industrial sectors. HCBD is highly persistent and bioaccumulative, and appears to meet the criteria of the recently adopted federal policy on toxic substances management. It is moderately to highly toxic to aquatic organisms. HCBD is carcinogenic and genotoxic in experimental animals. Potential intakes from food, based on early studies from other countries, may be close to levels that produce effects in animal studies. An assessment of the presence of HCBD in the Canadian environment is required to evaluate its potential impact on ecosystems and human health. The Panel is of the opinion that this substance should be assessed as quickly as possible.

Descriptions of the approaches to assessment of the effects of Priority Substances on the environment and human health are available in published companion documents. The document entitled "Environmental Assessments of Priority Substances under the Canadian Environmental Protection Act. Guidance Manual Version 1.0 - March 1997" (Environment Canada, 1997a) has been published to provide guidance for conducting environmental assessments of Priority Substances in Canada. This document may be purchased from:

• Environmental Protection Publications
  Environmental Technology Advancement Directorate
  Environment Canada
  Ottawa, Ontario
  K1A 0H3

It is also available on the Commercial Chemicals Evaluation Branch web site at www.ec.gc.ca/cceb1/eng/psap.htm under the heading "Technical Guidance Manual." It should be noted that the approach outlined therein has evolved to incorporate recent developments in risk assessment methodology, which will be addressed in future releases of the guidance manual for environmental assessments of Priority Substances.

The approach to assessment of effects on human health is outlined in the following publication of the Environmental Health Directorate of Health Canada: "Canadian Environmental Protection Act - Human Health Risk Assessment for Priority Substances" (Health Canada, 1994), copies of which are available from:

• Environmental Health Centre
  Room 104
  Health Canada
  Tunney's Pasture
  Ottawa, Ontario
  K1A 0L2

or on the Environmental Health Directorate publications web site (www.hc-sc.gc.ca/ehp/ ehd/catalogue/bch.htm). The approach is also described in an article published in the Journal of Environmental Science and Health -Environmental Carcinogenesis & Ecotoxicology Reviews (Meek et al., 1994). It should be noted that the approach outlined therein has evolved to incorporate recent developments in risk assessment methodology, which are described on the Environmental Substances Division web site (www.hc-sc.gc.ca/ehp/ehd/bch/env_contaminants/psap/psap.htm) and which will be addressed in future releases of the approach paper for the assessment of effects on human health.

The search strategies employed in the identification of data relevant to assessment of potential effects on the environment (prior to November 1997) and human health (prior to December 1996 for toxicity information) are presented in Appendix A. Review articles were consulted where appropriate. However, all original studies that form the basis for determining whether HCBD is "toxic" under CEPA 1999 have been critically evaluated by staff of Environment Canada (entry and environmental exposure and effects) and Health Canada (human exposure and effects on human health).

The environmental sections of this Assessment Report were produced by K. Taylor, Environment Canada, based on a report entitled "Canadian Environmental Protection Act Environmental Assessment for Hexachlorobutadiene," which was prepared for Environment Canada under contract by P.Y. Caux and D. Moore, The Cadmus Group Inc., Ottawa, Ontario. This report was peer reviewed by:

• K. Kaiser, National Water Research Institute, Environment Canada
• P. Kauss, Ontario Ministry of Environment and Energy
• L. McCarty, L.S. McCarty Scientific Research & Consulting
  
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The health-related sections of this

Assessment Report and supporting documentation were prepared by the following staff of Health Canada:

• R. Beauchamp
• K. Hughes
• B. Idris
• M.E. Meek

Sections of the Assessment Report and supporting documentation on genotoxicity were reviewed by D. Blakey of the Environmental Health Directorate of Health Canada. Sections related to evaluation of the effects on human health were externally reviewed by staff of BIBRA International and a peer review panel convened by Toxicology Excellence in Risk Assessment (TERA), composed of:

• J. Christopher, California Environmental Protection Agency
• M. Dourson, TERA
• M. Friedman, Cytec Industries, Inc.
• M. Gargas, ChemRisk Division of MacLaren/Hart
• P. McGinnis, Syracuse Research Corporation
• E. Ohanian, U.S. Environmental Protection Agency
• J. Reid, University of Cincinnati

The health-related sections of the Assessment Report were reviewed and approved by the Health Protection Branch Risk Management meeting of Health Canada.

The entire Assessment Report was reviewed and approved by the Environment Canada/Health Canada CEPA Management Committee.

A draft of the Assessment Report was made available for a 60-day public comment period (July 1 to Augus t 30, 200 0) (Environment Canada and Health Canada, 2000). Following consideration of comments received, the Assessment Report was revised as appropriate. A summary of the comments and responses is available on the Internet at:

www.ec.gc.ca/cceb1/eng/final/index_e.html

The text of the Assessment Report has been structured to address environmental effects initially (relevant to determination of "toxic" under Paragraphs 64(a) and (b)), followed by effects on human health (relevant to determination of "toxic" under Paragraph 64(c)).

Copies of this Assessment Report are available upon request from:

• Inquiry Centre Environment Canada
  Main Floor, Place Vincent Massey
  351 St. Joseph Blvd.
  Hull, Quebec
  K1A 0H3

or on the Internet at:

www.ec.gc.ca/cceb1/eng/final/index_e.html

Unpublished supporting documentation, which presents additional information, is available upon request from:

• Commercial Chemicals Evaluation Branch
  Environment Canada
  14th Floor, Place Vincent Massey
  351 St. Joseph Blvd.
  Hull, Quebec
  K1A 0H3

or

• Environmental Health Centre
  Room 104
  Health Canada
  Tunney's Pasture
  Ottawa, Ontario
  K1A 0L2