Integrated Framework for the Health-Related Components of Categorization of the Domestic Substances List Under CEPA 1999: Questions & Answers

What is a "sentinel product" in the complex exposure tool? How is exposure through multiple products taken into account?

A sentinel product is a specific type of consumer product with a defined composition and use that yields the highest exposure of an individual for one of its component substances compared with other consumer products containing that substance.

The exposure to multiple products can be accounted for by appropriate summation of the exposures from individual sentinel products.

How are impacts of exposures to multiple chemicals being taken into account in priority setting and assessment?

All substances on the DSL have been visually grouped by structure to identify similar subsets. To the extent possible, then, substances are grouped for consideration by the complex tools.

However, categorization is an initial prioritization phase intended to identify the substances on the DSL of highest priority for further assessment. As a result, it does not include comprehensive consideration of potential combined effects from multiple chemical exposures. If data are available that would indicate patterns of use consistent with multiple chemical exposures and the potential for additive, synergistic or antagonistic toxic effects, these data would be considered for substances prioritized for more detailed screening and PSL assessments.

How are potentially sensitive subgroups (e.g., children, women of child-bearing age) accounted for in the proposed integrated framework?

Variations in potential exposure and hazard for different subgroups of the population are taken into account by both the simple and complex exposure and hazard tools.

For SimET, the extent of this consideration is limited to potential variations by age group accounted for in the expert ranked use codes. The use codes provide an indication of whether or not consumer exposure is expected, where variations in use pattern among age groups are likely to be greatest. For ComET and all health assessments for existing substances under CEPA 1999, quantitative estimates of exposure are developed for six different age groups of the population, including infants and children.

SimHaz identifies substances as priorities for further consideration on the basis of several health endpoints, including those relevant to children and women of child-bearing age. These include the potential for developmental toxicity (i.e., toxic effects on the developing embryo, fetus or infant) or reproductive effects (i.e., toxic effects on reproductive systems of women and men) based on the results of studies in laboratory animals or human populations. SimHaz identifies substances based on classifications of "known to cause developmental toxicity or impair fertility," "regarded as if they cause developmental toxicity or impair fertility in humans" or "cause concern for humans owing to possible developmental toxic effects or effects on fertility."

The endpoints included in ComHaz and all health assessments for existing substances under CEPA 1999 address an inclusive range of effects with potential health impacts for the Canadian public, including potentially sensitive subgroups. For instance, the developmental toxicity endpoint in ComHaz includes available studies of toxic effects on the developing embryo, fetus and infant, and the reproductive toxicity endpoint includes a consideration of studies of toxic effects of substances on reproductive systems of women and men.

How will the order of screening assessments for substances remaining as priorities following the categorization deadline be determined? What are the expected timelines for completion of screening assessments on various priorities?

Substances prioritized for screening health assessments based on DSL categorization will be prioritized both by group and within each group. For example, those that are designated GPE and high hazard (HH) are the highest priorities for early completion of screening assessments. Within each of the prioritized groups (e.g., GPE/HH, IPE/HH, LPE/HH, GPE/IPE, P or B but not ITeco), each of the substances is ranked in order of its potential for exposure. Additional information on potential exposure and dose-response for critical endpoints in the highest-priority groups is currently being collected to additionally refine the order of health-based priorities for screening assessment.

The robust complex exposure and hazard tools and the several models of screening assessment that vary depending upon the priority of the substance and complexity of the issues addressed ensure efficient screening beyond 2006. Projections of time frames for completion of assessments within each of the prioritized groups are currently being developed, based on increasing experience in application of the complex tools.  

Has assessment work been completed on the approximately 1200 substances from the health draft maximal list now considered as either high or moderate health priorities for further action?

No, these substances have been prioritized for further action on the basis of potential risk (exposure and effect), hazard and exposure considerations. This health-related categorization, while risk based and believed to identify true health-based priorities, is not synonymous with human health risk assessments conducted under CEPA 1999. For example, the substances in the high health priorities for action group have not yet been critically assessed in regards to any potential risks to human health. Rather, they have been prioritized for further action (i.e., assessment) on the basis of the risk-based considerations of exposure and hazard. Assessment enables additional quantification of risk from more fully characterized sources.

What are the next steps for the approximately 700 substances from the health draft maximal list that are now considered to not require further work for human health at this time?

This group of substances includes those that have been assessed and/or managed under the 1988 Canadian Environmental Protection Act or CEPA 1999 (that is, listed on PSL1 or PSL2 or Schedule 1 or 3 of the Act); low-hazard compounds (determined by application of low-hazard components of SimHaz and ComHaz) and low-concern polymers; and "deprioritized" substances reflecting changes to their designation as PBITeco. Health Canada will track these substances for any new information that might warrant subsequent action (e.g., assessment).

How are data gaps addressed in priority setting for categorization?

(See also response to question on reliability of predictive hazard tools.)

SimET relies solely on the information submitted for all substances in the compilation of the DSL. For ComET, data gaps for physical-chemical properties (i.e., those for which empirical data are not identified based on extensive searching of public sources) are addressed by provision of information by industry or other stakeholders and/or the use of predictive tools or read-across data. For use patterns and release estimates, standard conservative scenarios are used in the absence of data. If gaps cannot be satisfactorily filled based on standard scenarios or predictive tools, the substances will be retained as priorities for additional consideration and move forward to screening assessments, at which time data can be requested or generated.

For ComHaz, in the absence of empirical toxicological data, predictive tools (including QSAR models; a SAR expert system and/or consideration of chemical structures of concern; and data on toxicity of analogues or surrogates) are taken into consideration, based on confidence in their output and weight-of-evidence considerations (such as consistency and biological plausibility). If gaps cannot be satisfactorily addressed based on consistent and confident output of predictive tools, the substances will be retained as priorities for additional consideration and move forward to screening assessments, at which time data can be requested or generated.

The application of the exposure and hazard tools is instrumental in identifying critical areas of data generation to address subsequent stages of prioritization and/or assessment

Is there a minimum data set for making categorization decisions? Are substances set aside if no relevant information is identified? Are data (e.g., environmental monitoring and biomonitoring data) being generated to support categorization efforts?

For the most part, as delineated under CEPA 1999, categorization is based on available data. The methodology (i.e., simple and complex tools) developed to meet the mandate ensures optimum utilization of existing data. The tools also identify priorities for data generation in screening. The minimum data set appropriate for screening assessment is considered to be that outlined in the Organisation for Economic Co-operation and Development's High Production Volume Chemicals Programme Screening Information Data Set.