Table 1 shows the criteria used to select Track 1 substances.

Table 1

Criteria for the Selection of Substances for Track 1.
Persistence(1) Medium Half-life Air >= 2 days(2) Water >= 182 days Sediment >= 365 days Soil >= 182 days	Bioaccumulation(3)   BAF >= 5,000 or BCF >= 5,000 or log Kow >= 5.0	Toxicity(4)   CEPA-toxic or CEPA-toxic Equivalent	Predominantly anthropogenic(5) Concentration in environment largely resulting from human activity
>= greater than or equal to
1. A substance is considered persistent when the criterion is met in any one medium.
2. A substance may be considered as persistent in air if it is shown to be subject to atmospheric transport to remote regions such as the Arctic.
3. Bioaccumulation Factors (BAF) are preferred over Bioconcentration Factors (BCF); in the absence of BAF or BCF data, the octanol-water partition coefficient (log Kow) may be used.
4. A substance is considered toxic if it meets or is equivalent to the definition of "toxic" found in the Canadian Environmental Protection Act (CEPA), as determined through a systematic, risk-based assessment. CEPA states: "a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that (a) have or may have an immediate or long-term harmful effect on the environment or its biological diversity; (b) constitute or may constitute a danger to the environment on which life depends; or (c) constitute or may constitute a danger in Canada to human life or health."
5. On the basis of expert judgment, the concentration of the substance in any environmental medium is due largely to the quantities of the substance used or released as a result of human activity relative to contributions from natural sources. Elements and naturally occurring inorganic compounds are not candidates for virtual elimination from the environment.

Environmental persistence refers to the length of time a substance resides in environmental media and is usually defined in terms of half-life -- the time required for the concentration of a substance to diminish to half its original value. A persistent substance degrades very slowly in the environment and therefore has a long half-life. Physical, chemical and biological processes that degrade a substance are considered in determining its half-life; dilution or transportation to other locations or media generally are not. For a substance to be considered persistent, it must meet a criterion in at least one medium.

Bioaccumulation describes the process by which a substance accumulates in a living organism -- either from the surrounding medium or through food containing the substance. A substance's potential to bioaccumulate can be expressed by the bioaccumulation factor (BAF), the bioconcentration factor (BCF) or the octanol-water partition coefficient (Kow). The BAF and the BCF measure the concentration of a substance in a living organism relative to its concentration in the surrounding medium.

The BAF accounts for substance intake from both food and the surrounding medium, while the BCF accounts for intake from the surrounding medium only. The octanol-water partition coefficient (Kow) estimates a substance's tendency to partition from water to organic media, such as lipids present in living organisms. The partition coefficient can be used in place of the BCF or BAF when limited experimental data are available.

Persistence and bioaccumulation depend on many factors, including the intrinsic properties of a substance, conditions in the environment, and the ecosystem under consideration. Thus, a given substance is likely to have a range of persistence and bioaccumulation values. Since substances can occur under a variety of conditions in Canada, expert judgment and the weight of scientific evidence will be used in determining if the criteria have been met.

Persistence and bioaccumulation apply only to individual chemical substances and cannot be applied to groups of substances or complex mixtures or effluents. A substance that satisfies the four criteria for Track 1 and that occurs in a complex mixture or effluent can, however, be a candidate for virtual elimination. In such cases, management strategies will need to take into account that these toxic substances occur within a mixture or effluent.

A document entitled Toxic Substances Management Policy - Persistence and Bioaccumulation Criteria provides details about these criteria, including their numeric values, the process and rationale used in establishing them, and information about how they are applied.

For the purposes of this policy, a substance is considered toxic if it meets or is equivalent to the definition of "toxic" found in the Canadian Environmental Protection Act (referred to as "CEPA-toxic"). While a variety of non-regulatory instruments may be used to achieve the management objectives under the policy, the federal government has the legislative authority to develop and enforce regulatory actions leading to virtual elimination or life-cycle management for a substance that has been determined to be toxic under this definition.

A substance is "CEPA-toxic equivalent" if it satisfies the definition of "CEPA-toxic" as a result of a systematic, risk-based assessment. Such assessments can include determinations made under other federal statutes, or can incorporate appropriate elements of assessments done by or for provinces or territories, international organizations or other appropriate scientific authorities.

In an assessment of "CEPA-toxic" or "CEPA-toxic equivalent", exposure is an important element in evaluating environmental risk under the policy. Persistence and bioaccumulation can be used as qualitative surrogates for long-term exposure of environmental biota. This approach will expedite the identification of Track 1 substances.

A substance's source of release is a fundamental consideration in selecting risk management strategies. Some substances that are persistent, bioaccumulative and toxic occur naturally and can never be eliminated from the environment. A substance will be considered "predominantly anthropogenic" if its concentration in an environmental medium is largely due to human activity, rather than to natural sources or releases. A substance that is "predominantly anthropogenic" in one part of Canada might not be so in another. Therefore, it will be necessary to rely on expert judgment when determining if a substance is "predominantly anthropogenic." Special consideration will be given to whether the objective of virtual elimination is technically achievable given the substance's origin. Elements and naturally occurring inorganic compounds are not candidates for Track 1.

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