Polychlorinated Dibenzodioxins and Polychlorinated Dibenzofurans - PSL1

Introduction

The new Canadian Environmental Protection Act (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 which may be harmful to the environment or constitute a danger to human health. The Act requires the federal Ministers of the Environment and of National Health and Welfare 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."

While research and information collection can be undertaken, the primary objective is to determine whether these substances are "toxic" according to the definition under the Act, in which case they are to be placed on Schedule I of the Act, which allows for the making of regulations to control any aspect of their life cycle, from the research and development stage through manufacture, use, storage, transport and ultimate disposal.

This report assesses the "toxicity" of the first substances to be evaluated: polychlorinated dibenzodioxins (dioxins) and polychlorinated dibenzofurans (furans), two related families of chemicals.¹

Dioxins and furans have been reviewed extensively by a variety of experts and organizations.² For the purpose of this assessment it is not necessary to perform a detailed review of the subject matter. Instead, this report is designed to be a general summary of the key findings of these previous reviews, and uses this information as the basis for the assessment of "toxicity".

¹ For simplicity, this report will use the terms "dioxins" and "furans" when referring to polychlorinated dibenzodioxins and polychlorinated dibenzofurans. However, when identifying a specific member of either of these families, such as 2,3,7,8-tetrachlorodibenzodioxin, the full name will be used.

² Reviews have been conducted by: Moore, 1973; Blair, 1973; IARC, 1977 Cattabeni et al., 1978; Esposito et al., 1980; Hutzinger et al., 1981; NRCC, 1981a, b, 1984; OME, 1985; Kimbrough, 1980; Kimbrough et al., 1984; FRG, 1985; U.S.EPA, 1985, 1988; WHO, 1987, 1989 (in press). Extensive compilations of papers produced at symposia include: Tucker et al., 1983; Boddington et al., 1985; Hutzinger et al., 1983, 1986; McNelis et al., 1989.