The purpose of the List was to define what was 'New to Canada' and it has been amended from time to time and currently contains approximately 23,000 substances. CEPA 1999 mandates that all substances on the DSL must be categorized within 7 years after the new CEPA received Royal Assent which occurred September 14, 1999. The proposed operational approach for both departments is represented in Figure 1 . Persistence and Bioaccumulation Regulations have been developed under the leadership of the Chemicals Control Division and came into force March 31, 2000.
Persistence is based on a consideration of all environmental media.
A substance is considered persistent if its transformation half-life satisfies the criterion in any one medium. A substance is considered as bioaccumulative if any of the bioaccumulation criteria in Table I are satisfied. The definition and interpretation of inherently toxic to non-human organisms is currently under development. Environment Canada has a proposed working definition which is subject to broader consultation before adoption. If a substance does not meet these criteria, then no further action is required for this substance under the categorization and screening Program.