Benzene - PSL1

1.0 Introduction

The Canadian Environmental Protection Act (CEPA) requires the Minister of the Environment and the Minister of National Health and Welfare 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 that are assessed to be "toxic" according to Section 11 may be placed on Schedule I of the Act. Consideration can then be given to developing regulations, guidelines, or codes of practice to control any aspect of these substances' life cycle, from the research and development stage through manufacture, use, storage, transport, and ultimate disposal.

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

Data relevant to the assessment of the entry, environmental exposure, and environmental effects of benzene were identified in review documents. Information was also identified by searching commercial and government databases and indices from 1989 to 1991. These databases and indices included: AQUAREF, BIOSIS Previews, Chemical Evaluation Search and Retrieval System (CESARS), Chemical Abstracts, Chemical Hazards Response Information System (CHRIS), Cooperative Documents Project (CODOC), Enviroline, Environmental Bibliography, FATERATE, Federal Register, Hazardous Substances Data Bank (HSDB), Integrated Risk Information System (IRIS), International Register of Potentially Toxic Chemicals (IRPTC), MICROLOG, National Technical Information Service (NTIS), Pollution Abstracts, Registry of Toxic Effects of Chemical Substances (RTECS), SOLUB, TOXLINE, and TOXLIT. Additional relevant information was obtained from the United States Environmental Protection Agency (U.S. EPA) and from industrial sources including representatives of the Canadian Petroleum Products Institute (CPPI). Although much of the research on benzene has been conducted outside Canada, available Canadian data on sources, use patterns, fate, and effects of benzene on the Canadian environment have been emphasized.

In addition to consulting review articles to identify data relevant to the estimation of exposure of the general human population to benzene and its effects on human health, computer literature searches were conducted biweekly from May 1990 to October 1991 on the MEDLINE, TOXLINE, and the NTIS databases. A search was also conducted on HSDB, RTECS, IRIS, Chemical Carcinogenesis Research Information System (CCRIS), TOXLINE, TOXLIT, and EMBASE in September 1991, to identify literature published after 1987 (date of previous extensive search).

Review articles consulted in the preparation of this report included those prepared by the Agency for Toxic Substances and Disease Registry (1989); National Institute of Public Health and Environmental Hygiene (1988); Occupational Safety and Health Administration (1987); Florida Petroleum Council (1986); U.S. EPA (1980); Austin et al. (1988); and Marcus (1987). Background documents prepared under contract, which were considered in the preparation of this report, included a multi-media exposure assessment of benzene for Canadian populations (Holliday and Park, 1989) and a data summary of concentrations of benzene in environmental media, human tissues, and terrestrial and aquatic organisms (Concord Scientific Corporation, 1990). Primary data included in reviews, which were not considered critical to the assessment of "toxic" to human health, were not evaluated.

Data relevant to the assessment of whether benzene is "toxic" to human health obtained after the completion of the sections of this report related to human health (i.e., October 1991) were not considered for inclusion. Similarly, data relevant to the assessment of whether benzene is "toxic" to the environment obtained after May 1992 have not been incorporated.

Although review articles were consulted where appropriate, all original studies that form the basis for determining whether benzene is "toxic" under CEPA have been critically evaluated by the following staff of Environment Canada (entry, and environmental exposure and effects) and Health and Welfare (human exposure and effects on human health):

Environment Canada

A. Bobra
B. Braune
L. Brownlee
D. Caldbick
R. Chénier
M. Hanlon

Health and Welfare Canada

K. Hughes
M. E. Meek

Quantitative estimates of carcinogenic potency were provided by D. Krewski and S. Bartlett of Health and Welfare Canada.

In this report, an overview of findings concerning benzene that will appear in the Canada Gazette is presented. A summary of technical information that is critical to the assessment is presented in Section 2.0. This information is presented in greater detail in a Supporting Document which is available upon request. The assessment of whether benzene is "toxic" under CEPA is presented in Section 3.0. The effects of photochemical reaction products of benzene are not addressed in this assessment but are considered in the Federal/Provincial Management Plan for nitrogen oxides and volatile organic compounds (CCME, 1990).

Sections of the Supporting Document relevant to human exposure and effects were reviewed by B.H. Thorpe (Ontario Ministry of the Environment), E.J. Williams (Shell Canada Ltd.), D. Johnson and F. Ratpan (NOVA Corporation of Alberta), R.J. Keefe (Imperial Oil Ltd.), and E. Vernot (American Petroleum Institute). Following peer review by P. Enterline (University of Pittsburgh) and R. Irons (University of Colorado) of sections of the draft Assessment Report and Supporting Document relevant to the assessment of effects on human health, they were approved by the Standards and Guidelines Rulings Committee of the Bureau of Chemical Hazards of Health and Welfare Canada. Environmental components of the Supporting Document were reviewed by representatives of the Canadian Petroleum Products Institute and by W.Y. Shiu and K.C. Ma (University of Toronto). The final Assessment Report was reviewed and approved by the Environment Canada/Health and Welfare Canada CEPA Management Committee.

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