Science approach document - Ecological risk classification of organic substances version 2.0 (ERC2)

Official title: Science approach document - ecological risk classification of organic substances version 2.0 (ERC2)

Environment and Climate Change Canada

March 2022

Cat. No.: En84-287/2022E-PDF

ISBN 978-0-660-42124-7


In 2016, Environment and Climate Change Canada (ECCC) developed and published a 21st-century science approach to re-prioritizing 640 organic chemicals from the third phase of the Chemicals Management Plan (CMP). Known as the Ecological Risk Classification of organic substances (ERC) approach, this first version of ERC (ERC1) was applied to organic substances that met criteria for further risk assessment following the Government of Canada’s categorization of the Domestic Substances List (DSL) in 2006, performed under the Canadian Environmental Protection Act, 1999 (CEPA). 

Since then, ECCC has refined its approach for the ERC, which led to the creation of this second version (ERC2). This Science Approach Document presents the ERC2 approach and the results of its application to approximately 12,200 organic substances from the DSL that did not meet criteria for further risk assessment following the 2006 categorization exercise. The ERC2 approach builds on ERC1 and refines key areas of uncertainty previously identified in ERC1 through better integration and transparency of weight of evidence concepts, expansion of the toxicological and exposure “space” used for hazard and exposure, increased consideration of model domain of applicability, updates to the decision logic governing classification rules based on new tools and lessons learned from ERC1 and the restructure of these rules, an increased focus on long-term developmental and reproductive toxicity and neurotoxicity, and the introduction of confidence and severity scoring for exposure, hazard and risk classification outcomes.

ERC2 is considered a high-throughput integrated approach to testing assessment (IATA)  method, as it uses many sources of “alternative data” (also known as new approach methodologies or NAM) such as in silico, in chemico, and in vitro data to complement traditional in vivo sources and to provide evidence for risk classification. The ERC2 approach gathers multiple lines of evidence in chemical profiles for hazard (toxicity) and exposure. The evidence is compared to logic rules established for hazard, exposure and risk classification to determine future assessment activities are merited. The details for all classification rules in ERC2 are provided in appendices of the science approach document, while the core science behind ERC2, contained in profile descriptors, is provided in the main body of the document. Each ERC2 classification is also associated with a confidence and severity score. The confidence score is a measure of the consensus of data and data availability. The severity score is a measure of hazard, exposure or risk scale and is used as a means of weighting various classification outcomes in ERC2 when considering possible future assessment activities.

Examples of risk assessment outcomes and targeted assessment activities (e.g., identification of endocrine active substances, potential for cumulative assessment, and regrettable alternatives) are provided to demonstrate how results from the ERC2 approach may be applied by ECCC for future work planning. Risk classification, confidence and severity results for ~12,200 substances on the DSL are contained in a Microsoft Excel® spreadsheet as a supporting document to this Science Approach Document.  

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