The Canadian Environmental Protection Act (CEPA) provides for the protection of the environment and of the health of Canadians from toxic substances and other pollutants. The legislation was enacted in 1988. It provided for actions on toxics that focused on the assessment, management and clean up of existing pollution. It has had a positive impact on how Canada deals with environmental challenges and has made possible many environmental achievements.

Provisions in CEPA called for a review of the Act after 5 years. The review focused on new expectations of Canadians and developments in environmental law and scientific knowledge since 1988. The new CEPA (CEPA 1999) has been modernized and strengthened by making pollution prevention the cornerstone of national efforts to reduce toxic substances in the environment. It shifts the focus from cleaning up environmental problems to preventing them in the first place. CEPA 1999 received Royal Assent on September 14, 1999, and was promulgated on March 31, 2000.

The revised legislation requires the government to assess more substances more quickly, and sets firm deadlines for action to control toxic substances. Several new mandates have been introduced in CEPA 1999 which proposes a more efficient process of identifying, screening, assessing and managing toxic substances, one of which is the Categorization and Screening of the Domestic Substances List (DSL).