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3,3'-Dichlorobenzidine - PSL1

1.0 Introduction

CEPA requires the Ministers of the Environment and 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 interpreted 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 the List of Toxic Substances (Schedule I of the Act). Consideration can then be given to developing guidelines, codes of practice or regulations 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 3,3'-dichlorobenzidine is "toxic", as interpreted 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 to levels that could cause harmful effects.

Data relevant to the assessment of whether 3,3'-dichlorobenzidine is "toxic" under CEPA were identified through evaluation of existing review documents (ATSDR, 1989; U.S. EPA, 1980; 1988; IARC, 1982), as well as an unpublished review of the environmental behaviour and health effects of this substance prepared under contract by Cambridge Environ-mental Inc. (Croy and DeVoto, 1990), supplemented with information from published reference texts and literature identified through on-line searches of various databases (HSDB, RTECS, IRIS, CCRIS, TOXLINE, TOXLIT, ENVIROLINE, CHEMICAL ABSTRACTS, BIOLOGICAL ABSTRACTS, ELIAS, AQUAREF, MICROLOG, CODOC). Information was also obtained from the CEPA Domestic Substances List, a CEPA subsection 16(1) Notice and from Statistics Canada. In addition, a number of provincial authorities were requested to provide any available information on the levels of 3,3' -dichlorobenzidine in the drinking water in their provinces. Data relevant to the assessment of the effects of 3,3'-dichlorobenzidine on the environment and human health obtained after April, 1992 and October, 1992, respectively, were not considered for inclusion.

Review articles were consulted where appropriate; however, all original studies that form the basis for determining whether 3,3'-dichlorobenzidine is "toxic" under CEPA have been critically evaluated by the following staff of Health and Welfare Canada (human exposure and effects on human health) and Environment Canada (entry and environmental exposure and effects):

R.G. Liteplo (Health and Welfare Canada)
R.J. Maguire (Environment Canada)
M.E. Meek (Health and Welfare Canada)

Quantitative estimates of carcinogenic potency were provided by M. Walker of Health and Welfare Canada.

A summary of technical information critical to the assessment, and which is presented in greater detail in an unpublished Supporting Document, is presented in Section 2. The assessment of whether 3,3'-dichlorobenzidine is "toxic" is presented in Section 3.

The environmental sections of this report were reviewed by Drs. C.M. Auer and W.H. Farland of the U.S. Environmental Protection Agency. Sections related to the assessment of effects on human health were approved by the Standards and Guidelines Rulings Committee of the Bureau of Chemical Hazards of Health and Welfare Canada. The entire Assessment Report was reviewed and approved by the Environment Canada/Health and Welfare Canada CEPA Management Committee.

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