Ecological Categorization Decisions
of Organic Substances

Environment Canada has collected and reviewed information in existing databases from around the world, on the 11,317 organic substances on the Domestic Substances List (DSL) that need to be categorized.

The ecological categorization decisions are based on experimental data and modelled data (if experimental data were not available to Environment Canada), e.g. Quantitative Structure Activity Relationships (QSARs).

Environment Canada selects pivotal values from available experimental data, selecting the most conservative value and evaluating the reliability of that data. Should Environment Canada deem a study as unreliable (not robust), the process is repeated until either an acceptable study is found, or the available studies are exhausted. If no robust experimental data are available then QSARs predictions are used.

Categorization results for organic substances are available in the spreadsheet entitled Decisions for Ecological Categorization of Substances on DSL (Organics). A summary of the results is presented in Table 1.

Table 1 – Ecological Categorization Decisions – Organics

Environment Canada has collected experimental data on persistence, bioaccumulation and inherent toxicity to non-human organisms from many large comprehensive data sources as well as some smaller sources.

These literature and database searches have demonstrated an overall lack of quality experimental data for many organic substances. For instance, for the organic substances being categorized, initial data searches identified:

• experimental bioaccumulation data for only 410 substances, and only one-quarter of this data was of acceptable quality
• experimental persistence data for only 850 substances, and one-third of this data was of acceptable quality
• experimental data of inherent toxicity to non-human organisms for only 1051 substances. Three-quarters of this data were of acceptable quality.

Where Environment Canada lacked quality experimental data, Quantitative Structure Activity Relationships (QSARs), which are computer models that generate predictions for an endpoint based on a database of experimental data, have been used to fill the data gaps. Environment Canada’s approach to using QSARs is described in the Guidance Manual for the Categorization of Organic and Inorganic Substances on Canada’s Domestic Substances List.

Environment Canada prefers to base its decisions on experimental data rather than modelled data, when experimental data is available. As such, Environment Canada encouraged interested parties to provide relevant experimental study information by September 2005, on the persistence, bioaccumulation, and inherent toxicity to non-human organisms for the organic substances on the DSL to help improve its decisions. Environment Canada has reviewed this information and has considered it following the data preference/selection process described previously and detailed in the Guidance Manual.

To ensure that decisions are based on sound science, Environment Canada has developed an approach for assessing the reliability of experimental studies. In order to assess these in a consistent manner, robust study forms are filled out to summarize and evaluate the relevant information about the study conditions and methods used.

All of the information received, either the entire proposal or the robust study summaries of the data submitted, are available on CD. To obtain a copy of the CD, please send a request to the following address: ESB.DSE@ec.gc.ca.

Disclaimer: Although care has been taken to ensure that the information found on this website accurately reflects the requirements prescribed in the Canadian Environmental Protection Act (1999), you are advised that, should any inconsistencies be found, the legal documents, printed in the Canada Gazette, will prevail.