Rapid screening of substances of lower ecological concern: uncertainties and further activities

Uncertainties and Further Activities

It is recognized that conclusions resulting from use of rapid screening have associated uncertainties, as the approach makes use only of data that is relatively easy to obtain. However, it is believed that the number of false negative conclusions will be low, due to the use of a wide range of filters (relating to both use quantity and ecological hazard concerns identified for a substance), as well as the use of different conservative exposure scenarios. The high fraction of these lower concern substances that have been identified by rapid screening as requiring further assessment (30%) is a reflection of the conservative basis of the approach.

Values for physical/chemical and hazard properties derived during categorization of the DSL were used as input for the RAIDAR modelling work. As is recognized in documentation associated with categorization, there are uncertainties in these values, in particular with those that have been estimated using different modelling approaches. Extreme values that were estimated by models were replaced by limiting values of physical/chemical properties or alternatively derived toxicity values, prior to using them as input for RAIDAR modelling as part of rapid screening (CEMC, 2007a). A supplementary document (Environment Canada, 2007d) further discusses some of these factors in the context of rapid screening.

Additionally, rapid screening is based in part on consideration of use and volume data that were submitted when the DSL was first created 20 years ago. Information sources consulted at step 3 of rapid screening were used to verify whether assumptions regarding current quantities in commerce were appropriate. As announced by the Government of Canada in December 2006, new requirements will be coming into place for the updating of this information. Conclusions from this rapid screening assessment will be revisited as new information on quantities and uses become available.

In the meantime, it is important to recognize that the Government of Canada can identify substances for assessment based on a number of different considerations. Substances may be subject to assessment whether or not they meet categorization criteria, and whether or not the Existing Substances Program has previously concluded that the substance did not meet criteria in section 64 of CEPA 1999.

Substances for which it is proposed, based on the outcome of the rapid screening approach and other considerations, that they do not meet the criteria in section 64 of CEPA 1999 remain subject to re-assessment if information is identified that indicates that further evaluation of the substance is warranted. Examples of the types of information that may trigger further evaluation of a substance include:

  • Evidence of higher quantities in commerce. Since the rapid screening approach is driven in part by use quantity information, updated information to suggest that higher quantities of a substance are now in use could indicate that a substance should be subject to further evaluation.
  • Evidence of higher releases. The exposure scenarios used assumptions that are expected to be conservative for most substances. Updated information indicating that the assumed conditions are not protective for a particular substance owing to its routine handling and use could indicate that a substance should be the subject of further evaluation.
  • Evidence of ecological exposure. Monitoring data demonstrating the detectable presence of a substance in environmental media could indicate that a substance should be the subject of further evaluation.
  • Evidence of other possible ecological risk. Information that was not considered in the rapid screening approach, but that could be of significance in establishing an ecological risk from a substance, could trigger further evaluation of the substance.
  • Evidence that a substance is a PBiT. Since PBiTs are not candidates for the rapid screening approach, any information to suggest that the substance is PBiT could trigger further evaluation of the substance.
  • Identification as part of a category undergoing assessment. If the substance is part of a group that is prioritized for a category assessment at some time in the future, the substance may be subject to this further evaluation.

Information of these types may be identified from a number of different sources, including:

  • direct submission of information by stakeholders;
  • research, monitoring and DSL update activities taking place under the Chemicals Management Plan;
  • other assessment or regulatory activities in Canada or in foreign or international forum.
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