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The Canadian Environmental Protection Act, 1999 (CEPA 1999) provides the legislated framework for the identification and control of existing substances and management of those considered to pose a risk to human health and/or the environment.
CEPA 1999 required systematic consideration of approximately 22 400 existing substances within a prescribed (seven-year) time frame (by September 14, 2006) to set priorities for health risk assessment. This progressive mandate involved consideration of both exposure and hazard, was precedent setting internationally, and was technically demanding.
The priority-setting tools and assessment products that have been developed to meet this mandate set the stage for efficient health assessment for potential risk management of much greater numbers of existing substances than ever before, while maintaining scientific integrity and transparency.
These tools and products draw upon considerable prior program experience in the development of methodology for and completion of in-depth, detailed human health risk assessments on about 70 "Priority Substances," most of which were published in the peer-reviewed scientific literature and/or served as the basis for international assessments.
Throughout the development of novel tools and assessment products to systematically set priorities for further work from among all existing substances, external experts were engaged in various stages of peer input, consultation, and review. The potential for conflict of interest was carefully considered and managed in such reviews.
Industrial stakeholders and representatives of the non-governmental environmental community were continuously informed during the development of tools and products for the health-related stream of categorization and screening. Formal written feedback was solicited through posting of proposals for public comment.
Categorization of the DSL under Section 73 of CEPA 1999 required Health Canada to identify substances that should be considered further for the screening assessment of risks to human health and the environment, on the basis that:
A simple exposure tool (SimET) was developed to identify substances on the DSL considered to represent GPE. This approach was based on three lines of evidence: 1) quantity in commerce in Canada; 2) number of companies involved in commercial activities in Canada; and 3) the consideration by experts of the potential for human exposure based on various use codes. The proposed approach was released for public comment in November 2003 and also enabled designation of substances as presenting an Intermediate (IPE) or Lowest Potential for Exposure (LPE), based on criteria for quantity and nature of use.
A series of simple (SimHaz) and complex hazard tools (ComHaz) as well as a complex exposure tool (ComET) were also developed (Figure 2), to be implemented within an integrated framework for the health-related components of DSL categorization.
Tools for Health-Related Components of DSL Categorization
Hazard [High (H) or Low (L)]
This approach, which took into consideration both exposure and hazard, resulted in the identification of substances that represented the highest priorities for action from a human health perspective. It also offered a number of advantages and exceeded the requirements of categorization, by:
Implementation of this framework and associated tools has application well beyond simply identifying substances for assessment. These tools enable the efficient prioritization and subsequent screening health assessment of any substance considered by the program. Health priorities from categorization have been prioritized by group, based on whether they are exposure, hazard, or risk based, and within groups, based on consideration of their relative potential for exposure. Continued application of the complex tools following the release of the results of categorization will contribute to screening assessment for prioritized compounds.
The simple exposure and hazard tools were applied to the entire DSL (see Figure 3), leading to the draft "maximal list" of health priorities (Figure 4). The potential for persistence or bioaccumulation to additionally contribute to exposure for certain subsets of substances -- namely, those that are organic -- was also taken into account.
This health draft maximal list, released in October 2004, was composed of approximately 1900 substances grouped according to their high, moderate, or low likelihood of being considered further in DSL categorization and screening assessment. This list identified the maximum numbers and names of substances for inclusion on the list of substances requiring further assessment in 2006 in a close to final form.
This list was released at that time in an effort to reduce uncertainty for stakeholders regarding the likelihood of substances to remain on the list in September 2006 and to permit sufficient time and opportunity for interested parties to submit specified data in focused areas for consideration in subsequent refinement of the list.
The proposed integrated framework for the health-related components of DSL categorization was released for public comment in June 2005.
Following release of the health draft maximal list, a number of activities were undertaken, aimed at:
A summary of the key milestones associated with the health-related components of DSL categorization is presented in Figure 5.
A schematic outlining the principal results of the health-related components of DSL categorization is presented in Figure 6. These results are presented in an accompanying document (see Results of the Health-Related Components of Categorization of the Domestic Substances List under CEPA 1999).
Approximately 1150 substances from the draft maximal list of health priorities are now being considered as either high or moderate health priorities for further action. Substances have been prioritized for further action on the basis of potential risk (exposure and effect), hazard, and exposure considerations.
The high health priorities for action group2 is composed of all substances on the DSL identified as posing a high health hazard, based on a weight of evidence determination by the simple hazard tool (SimHaz). Within this group, there are:
The moderate health priorities for action group4 is composed of substances (n = ~630)5 included on the basis of exposure considerations -- that is, substances that are either GPE or IPE and persistent or bioaccumulative.
Substances included in the high and moderate health priorities for action groups have also been delineated according to whether:
About 40% of the substances on the draft maximal list of health priorities (n = ~760) are considered to no longer require further work for human health at this time.6 This group of substances includes:
Substances in subsets of this third group will be tracked for any new information that might warrant subsequent action (e.g., assessment).
Following development of the maximal list, some additional substances7 were prioritized for consideration on the basis of updates to weight-of-evidence hazard determinations in the simple hazard tool (SimHaz) or as a result of changes to determinations of persistence and/or bioaccumulation. Next steps for these substances will be considered post-September 2006.
These groups of substances account fully for all of the substances on the draft maximal list of health priorities.
In addition to these lists of substances representing the health-related results of DSL categorization, in September 2006, the finalized integrated framework on the health-related components of DSL categorization will also be released. A summary table of comments received in response to the call for public comment on the integrated framework and the Health Canada response to these comments, as well as lists of questions and answers related to the health-related categorization of the DSL, will also be issued.
The health-related categorization of the DSL will not necessarily cease on September 14, 2006. It is envisaged that the DSL will be reviewed on an annual basis to determine if any additions to the list should be considered as priorities for further screening health assessment, based on the simple and complex exposure and hazard tools.
An action plan has been developed to deal with the substances in the high and moderate health priorities for action groups (see Figure 7).
Depending upon the group, the focus of the initial efforts will be on assessment and/or management:
In the assessment and management phases, priorities will be health and/or environment led. This results from variations in priorities for human health versus the environment arising from DSL categorization, which offers gains in efficiencies through designation of a "lead department" for identified health and environmental priorities, respectively.
The simple and complex exposure and hazard tools developed for DSL categorization provide a risk-based framework that is relevant to prioritization of substances from any other "feeders" for screening health assessment. Such "tools-based decision-making" will be used to identify non-priorities for screening health assessment.
The conduct of screening health assessments for much larger numbers of substances permits profiling across data sets, leading to development of "right-sized" risk management.
For substances clearly posing low exposure potential and low hazard to human health, sufficient assessment documentation will be provided to fully and credibly support conclusions that a substance is not a priority for screening health assessment or does not pose a risk to human health.
The transparency for the tools-based assessments is supported by the robustness of the documentation associated with development of the methodology for the various tools, which lends itself to less substance-specific assessment documentation.
Work planning for screening health assessment will also take into account the priorities for assessment based upon the environment-related results from DSL categorization.
6 See table entitled "Substances Not Requiring Further Work for Human Health at This Time" in Results of the Health-Related Components of Categorization of the Domestic Substances List under CEPA 1999.