Overview of the Existing Substances Program: chapter 4

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4. Risk assessment

Substances identified as priorities for risk assessments undergo a process which compares the effects of substances on humans or the environment to the potential for exposure.

4.1 Scope of risk assessments

Even though substances are identified and prioritized for assessment using a range of approaches, assessments conducted under the Existing Substances Program fall under one of the following mandates:

  • Priority Substances List Assessments: Section 76 of the Canadian Environmental Protection Act, 1999 (CEPA) requires the Ministers of Environment and Health to establish a Priority Substances List (PSL) that identifies substances to be assessed on a priority basis.
  • Screening Assessments: Section 74 of CEPA requires the Ministers of Environment and Health to conduct screening assessments of substances that have been identified through the categorization exercise.
  • Reviews of decisions of other jurisdictions: Section 75 of CEPA requires the Ministers to review decisions of other jurisdictions specifically prohibiting or substantially restricting substances.
  • Other assessments: Section 68 of CEPA provides further general provisions for assessing, and for making recommendations with respect to substances, including measures to control their presence in the environment.

In this regulatory context, assessments are conducted to determine if a substance meets the criteria set out under section 64 of CEPA - that is, whether or not a substance

"... is entering or may enter the environment in a quantity or concentration or under conditions that

  1. have or may have an immediate or long-term harmful effect on the environment or its biological diversity;
  2. constitute or may constitute a danger to the environment on which life depends; or
  3. constitute or may constitute a danger in Canada to human life or health."

Determining whether a substance meets the criteria set out under section 64 is therefore a function of its release into the environment, the resulting concentrations in environmental media and/or the potential for exposure in humans, and its inherent toxicity. Risk assessments are objective and science based, and not influenced by socio-economic considerations.

Based upon screening assessment findings, Ministers of Environment and Health may propose one of the following measures:

  • taking no further action at this time under CEPA
  • adding the substance to the PSL for further assessment
  • recommending addition of the substance to Schedule 1 of CEPA, and development of risk management instruments and, where appropriate, implementation of virtual elimination

4.2 Principles and approaches

Timely delivery of a credible assessment outcome is determined both by the administrative procedures that are followed and by the robustness of the science that forms the basis of the assessment. The Existing Substances Program will apply a number of principles and approaches that have been derived from overarching guidelines and policies, such as those previously mentioned [particularly the Science Advice for Government Effectiveness (SAGE) and the Precautionary Principle]:

  • Predictability: In order to foster consistency and predictability of the assessment process, the approaches taken to identify and analyze information and to characterize entry, exposure, effects and risks will be documented in publicly available guidance documents.
  • Innovation: Approaches to risk assessment are constantly changing as science evolves. In addition, risk assessors may often face situations where assessments must be conducted for substances for which there is limited information relating to their properties, release, exposure or effects. The Existing Substances Program will use the latest tools and approaches, potentially in conjunction with domestic or international partners, to produce faster, more efficient, and technically solid assessments.
  • Openness and inclusiveness: A key to achieving timely and credible assessment outcomes is stakeholder engagement. Ongoing consultations with interested parties at specific stages in the assessment process will demonstrate the Program's commitment to openness and inclusiveness. Furthermore, publicly available documents describe various aspects of the Program, including its policies, processes, and the technical approaches used in conducting assessments.
  • Information management: In order to conduct rigorous assessments, the Existing Substances Program requires a wide range of substance-specific data including chemical and physical properties, quantities manufactured, quantities used and imported in Canada, its movement and persistence in the environment, effects on humans, effects on animals and plants, concentrations in the environment, and the results of long-term and short-term exposure to the chemical substance. The Existing Substances Program collects this information in a variety of ways, including literature searches and modelling exercises, and may generate this information by conducting or supporting research and, testing and conducting surveys. Also, stakeholders are expected to participate actively in providing the program with input at the outset of an assessment. All information will be rigorously analysed in order to ensure that the information used in the assessment is scientifically sound.
  • Use of sound science: Approaches used by the Existing Substances Program to carry out risk assessments will be consistent with those used in regulatory assessments internationally. Methods presented in technical guidance documents are thoroughly reviewed and discussed. In assessing specific substances, external expertise will be sought, when appropriate, in conducting the assessments. In addition, draft assessments will be subjected to an external science review step, involving appropriate experts from government, academia, industry, or non-governmental organizations, notably targeting input on critical technical issues. Peer review may include multiple steps depending on the issues at hand.
  • Transparency: Maintaining transparency is a key to credible assessment and management of the risks of substances. The Existing Substances Program recognizes that clear communication of uncertainties is an important part of achieving transparency. To satisfy the need for transparency, as well as to support sound assessment and risk management decisions, uncertainties as well as the approaches or assumptions made in dealing with those uncertainties will be recognized explicitly in any assessment.
  • Use of a weight-of-evidence approach and precautionary principle: Section 76.1 of CEPA states that when conducting and interpreting the results of an assessment, a weight-of-evidence approach and the precautionary principle shall be applied. Under the Existing Substances Program, a weight-of-evidence approach and the precautionary principle will be used throughout the risk assessment and management process. Precaution in an assessment will usually be manifested through conservative assumptions or by considering the thoroughness, consistency, concordance, plausibility and other factors affecting the robustness of independent experimental observations.
  • Accountability: The Existing Substances Program recognizes that assessment activities may require engagement from various stakeholders. However, the Program retains ultimate accountability for timely delivery of its publicly stated assessment objectives, and its performance will be measured on that basis.

4.3 Conducting risk assessments

Risk assessments are conducted to determine whether or not a substance may cause harm to the environment and/or to human health, considering both the inherent properties of a substance (i.e. characterization of a substance's hazard), and the potential for human or environmental exposure to the substance in Canada.

Assessment of substances involves reviewing and characterizing information collected, and integrating this information on exposure and effects by considering the weight of evidence to reach a conclusion regarding the potential for risk to humans or the environment.

The scope of a particular assessment may vary according to the complexity of the issues involved. The Existing Substances Program uses all scientifically robust information available at the time of the assessment to make conclusions on risk using a weight-of-evidence approach.

Detailed information on the various aspects of the assessment process, including technical guidance on methods used to conduct assessments, may be found in Existing Substances Program guidance documents.

4.4 Concluding on assessments

Every assessment, no matter how detailed and comprehensive, includes elements of uncertainty. Uncertainty may influence the estimation of the magnitude and likelihood of risk, and could impact the conclusion reached by an assessment. Therefore, a critical element in developing credible assessment conclusions is the identification and open communication of uncertainties and the measures that were taken to account for them. This includes identifying individual sources of uncertainty and considering their cumulative impact on the confidence in the assessment conclusion.

In some cases, lack of information precludes refinement of assessment scenarios, resulting in conclusions that are based on conservative default assumptions. In such cases, stakeholders are given the opportunity to provide information to reduce uncertainties. When such information is not provided, decisions on whether or not to take preventive or control actions can only be made by balancing the potential for risk and magnitude of impacts with knowledge of uncertainties.

When several lines of evidence point in the same direction (e.g. suggest potential risks), certainty in the overall conclusion of the assessment is increased. A weight-of-evidence approach can also facilitate making conclusions in the face of conflicting information.

The weight of evidence comprises the information necessary to reach a conclusion. Decisions are therefore made as soon as the necessary scientifically defendable information, which varies between assessments, is collected.

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