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Health-Based Guidance Values for Substances on the Second Priority Substances List

Preface

The guidance values presented within this booklet are intended to form, in part, the basis for development of reference points against which the quality of various environmental media can be judged. They were developed on the basis of information reviewed for assessments conducted for substances on the second Priority Substances List (PSL2) under the Canadian Environmental Protection Act, 1999 (CEPA 1999). Tolerable Concentrations (TCs) provide a health-based goal against which levels of various pollutants in indoor or ambient air can be compared. Similarly, Tumorigenic Concentration₀₅s (TC₀₅s) divided by a suitable margin also provide a benchmark against which the quality of ambient or indoor air can be judged with respect to potential carcinogenicity. Tolerable Intakes (TIs) and Tumorigenic Dose05s (TD₀₅s) (the latter divided by a suitable margin) provide a reference against which amounts of contaminants ingested in, for example, drinking water or food can be compared.

The PSL2 assessments on which the guidance values presented herein are based were externally peer reviewed by identified experts. Following external review, they were approved by the Environment Canada/Health Canada CEPA Management Committee. A draft of this booklet was circulated for information and comment within Health Canada and externally reviewed by Dr. V.C. Armstrong, consultant.

These guidance values are derived solely from assessment of toxicological and epidemiological data for the ingestion and inhalation routes of exposure and take into consideration potential effects on human health only. Although dermal contact may, in some cases, also contribute significantly to total exposure to environmental contaminants, this route has not been addressed herein, due principally to limitations of the available data that serve as a basis for development of health-based guidance in this area.

It should also be emphasized that the guidance values presented herein do not take into account any considerations related to risk management, such as feasibility of attainment or costs of measurement and control. Moreover, potential for exposure by ingestion via more than one medium (e.g., drinking water and food) needs to be considered in the development of media-specific values from the TIs and TD₀₅s presented herein. A detailed discussion of the allocation of TIs or TD₀₅s as a basis for development of media-specific guidance values is included in IPCS (1994).

Every effort has been made to present information in this booklet as accurately as possible without unduly delaying its publication. However, should errors be noted or should readers wish to comment on the suitability of derived values included herein, relevant information should be submitted to the Existing Substances Division for consideration at:

Existing Substances Division
Environmental Contaminants Bureau
Safe Environments Programme
Health Canada
Environmental Health Centre
room 145
Tunney's Pasture
Postal Locator: 0801C2
Ottawa, ON K1A 0L2

Email: ExSD@hc-sc.gc.ca