As part of its implementation of the modernized Canadian Environmental Protection Act, 1999 (CEPA), on August 17, 2024, Health Canada published a Canada Gazette notice announcing the availability of its Science Approach Document — Chemical Screening and Prioritization: Health Canada’s Automated Workflow for Prioritization (HAWPr). The science approach document (SciAD) describes the scientific approach that Canada applied to more than 25,000 chemicals on the Domestic Substances List (DSL) to prioritize their risk to human health based on their inherent hazard properties, current use in products, and quantities in commerce. Canada developed HAWPr to collect, organize, and process chemical data more efficiently to expand on the methods used to identify risk assessment priorities under CEPA. According to the Canada Gazette notice, the SciAD presents the key elements of the HAWPr, including:

• The information sources where data are collected;
• Predictive modeling approach for data-poor chemicals;
• The human health hazards considered and the criteria for determining if a substance has a hazard indicator;
• Substance use patterns and volume considerations used in a weight-of-evidence evaluation to determine exposure potential;
• The integration of hazard and exposure information for risk-based prioritization;
• Validation of the workflow by comparing prioritization decisions against known hazardous substances and those with known human exposure;
• Proposed outcomes for substances on the DSL; and
• Limitations and uncertainties of the tool.

The notice states that “SciAD demonstrates that the HAWPr is a robust tool that will improve how substances are prioritized for assessment work under CEPA in order to continue to protect the health of people living in Canada.” Preliminary results for the use of the HAWPr on the DSL substances are available as a supporting document to this approach. Canada is providing a public consultation on the SciAD in advance of using this information in prioritization activities to allow the public to comment and provide additional information on the approach and its application to the DSL. Comments are due October 16, 2024.