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Risk assessment of chemical substances

Fact sheet series: Topics in risk assessment of substances under the Canadian Environmental Protection Act, 1999 (CEPA)

The information described on this page and each related fact sheet may change as our chemical substances assessment program, policies, and methods evolve over time.

CEPA is one of Canada's core environmental laws to protect people in Canada and the environment from the effects of pollution. In June 2023, amendments were made to CEPA that include changes to parts of the Act about the assessment of substances, such as requiring a new Plan of priorities.

Substances that are assessed under CEPA include individual chemicals, polymers, nanomaterials, and living organisms that are animate products of biotechnologya. Many substances are human-made and some are also formed through common chemical reactions that occur naturally in the environment. They have many different properties and many different uses. Some are used to make plastics flexible while others help to put out fires. Still others are present in foods and in products we use as part of our day-to-day activities, such as shampoos, floor cleaners, clothing fabrics, and children's toys.

In the same way that substances have different properties, some can also be harmful in different ways. For instance, some may harm fish, while some are linked to life-threatening diseases, such as cancer. Others may be carried long distances through the air and affect people or the environment far away.

The risks posed by a substance are determined both by its hazardous properties and by the nature of the exposure that takes place. Scientific evaluations or assessments are conducted under CEPA to determine whether there are risks resulting from exposure of people in Canada to a substance or from releases of a substance into the environment, and the specific ways people in Canada or the environment can be affected.

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The CEPA risk assessment process

Under the purview of the Minister of the Environment and the Minister of Health, scientists assess existing substances that are in commerce in Canada [substances on the Domestic Substances List (DSL)] and new substances intended to be imported into or manufactured in Canada (not yet on the DSL), to determine whether these substances are toxic or capable of becoming toxic under CEPA. Decisions are based on a scientific evaluation of the risk to the environment and to human health posed by a substance, which considers both the hazardous properties of the substance (such as toxicity to aquatic organisms or cancer-causing properties) and the nature and extent of the exposure of people in Canada and the environment to the substance. This allows the Government of Canada to determine whether a risk management instrument or action is needed, and if so, what type of control is best suited for reducing or preventing the potential harm.

The unique characteristics of substances need to be considered when making decisions about the need for risk management. For example, it may be straightforward to assess a substance that has a single use. It gets more complicated, however, for substances that have many different uses, enter the environment in different ways, or could affect humans or other organisms differently depending on the nature of the exposure.

As a result, there are various assessment approaches that may be undertaken. The most common approaches are described within the Risk Assessment Toolbox. In addition, substances that may be of concern and warrant an assessment are identified through the ongoing consideration of new information. This approach for identifying and selecting priorities for assessment serves as the basis for CEPA's new Plan of priorities.

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Approaches

Data on the amount and the rate at which a substance enters the environment, how it enters the environment, as well as its chemical properties, provide information about how the substance is or may become distributed in the environment. How long it will reside in the environment, and whether it is present at levels that may be harmful to people in Canada or the environment are also considered. All the above information is combined to assess the fate of the substance in the environment and therefore understand how exposure occurs or may occur.

Different approaches for characterizing exposure may be used depending on the information available regarding sources, uses, handling, and disposal of the substance. For human health assessments, certain parameters used in estimating exposure are standardized to ensure consistency of approach (exposure factors). Among the various sources and uses of substances that may result in exposures, everyday products and food-related uses are often considered in assessments for human health and the environment.

The potential effects of substances on human health and the environment are evaluated (hazard characterization). The most susceptible populations (such as children) or receptors (such as early life stages of fish) as well as critical effects (such as mortality, reproductive and developmental impairment, endocrine effects, and carcinogenicity) are identified. In some cases, assessments will evaluate the risk posed by a common moiety (a part of the molecule that is of potential concern). When using a moiety approach, substances containing the same moiety are grouped and assessed together. Substances may also be grouped together for assessment based on similar physical or chemical properties or uses.

In the assessment and management of substances, the Government takes into consideration subpopulations who, due to greater susceptibility or greater exposure, may be more vulnerable to experiencing adverse health effects from exposure to substances. Amendments made to CEPA in June 2023 recognize the importance of considering these subpopulations in assessment and the Government is exploring opportunities to strengthen its approach.

A combination of qualitative and quantitative approaches may be used to characterize the overall risk of a substance. This includes data generated through laboratory or field testing, and modelling approaches, as examples. The results inform both ecological and human health assessments.

New approach methods (NAMs) are used in assessments and include any technology, methodology, approach or a combination of these that can be used to replace, reduce or refine animal testing and allow for more rapid or effective prioritization and/or assessment of chemicals. In Canada, the Government develops and uses NAMs to support risk assessment, including for screening, prioritizing, grouping, and informing decisions in both the existing and new substances programs under CEPA.

Examples of the use of NAMs in both human health and ecological assessment activities are provided and described in science approach documents (SciADs). For human health, the bioactivity exposure ratio SciAD describes a high-throughput computational approach for chemical prioritization and screening level assessment. On the environmental side, the Ecological Risk Classification of Organic Substances version 2.0 (ERC2) approach is an example of an innovative science approach for prioritizing substances and classifying risks.

A common issue in the assessment of substances is a lack of available experimental data. In the absence of experimental data on a substance, other approaches (for example, NAMs) may be used to address data needs, such as the use of computational modelling and read-across. For read-across, data from substances that have a similar structure and physical-chemical properties to the substance being assessed are used to address gaps in toxicity data.

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The risk assessment process for existing substances

An essential first step in assessment is the collection of information on each substance or substance group. A range of information is considered in an assessment, including chemical properties, quantities manufactured in or imported into Canada, releases to and concentrations in the environment, environmental fate and behaviour, hazards, and nature of exposure. Information is gathered from a wide variety of published and unpublished sources. These include literature and database searches, information submitted by stakeholders through voluntary or mandatory surveys, and previous reviews or assessments of substances conducted by other national or international agencies. Information is also generated by government researchers or stakeholders carrying out studies, testing, or monitoring of substances. For example, biomonitoring surveys on humans provide data on the levels of a substance in a person's blood or urine that characterize exposure to a given substance.

Throughout the assessment process, expert and stakeholder engagement is an important component. Assessments undergo external peer review or consultation involving experts from government, academia, industry, and non-governmental organizations, to obtain expert input on critical technical issues. As well, draft assessments are subject to a 60-day public comment period. While all comments are taken into consideration, the final content and conclusions of assessments remain the responsibility of Health Canada and Environment and Climate Change Canada.

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The risk assessment process for new substances

Prior to a substance being imported or manufactured in Canada, the new substance must undergo an ecological and human health risk assessment. This process begins with a pre-import or pre-manufacture notification of the substance. This means that any company or individual intending to import or manufacture a new substance in Canada is required to submit a package containing all information prescribed in the New Substances Notification Regulations.

In general, the risk assessments of new substances are conducted similarly to those for existing substances. Ecological and human health risk assessments are conducted based on information provided in the notification package and any other information that is available to the New Substances program to determine whether the substance is toxic or capable of becoming toxic. These assessments are required to be completed within the assessment period prescribed in the New Substances Notification Regulations. See the New Substances program for more information, including on assessments of new living organisms.

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Risk conclusions under CEPA

For the purposes of section 64 in Part 5 of CEPA, a substance is toxic if it 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

A determination of whether or not a substance or group of substances meet these criteria takes into consideration the relevant information available such as its hazard (effects) and its potential exposure to the environment and humans as well as any uncertainties. Maintaining transparency is key to a credible assessment process. Therefore, care is taken to ensure uncertainties are captured and communicated in the assessment.

In conducting a risk assessment, a weight of evidence approach and precaution are applied. Key information across multiple lines of evidence is taken into consideration, along with uncertainties when concluding the risk assessment. In order to estimate the likelihood of effects or potential for risk, a comparison of levels of exposure to humans or ecological organisms to levels that are known to cause adverse effects is conducted. These are referred to as margins of exposure (MOEs) or risk quotients (RQs) and are used in risk assessments of substances.

Approaches used to carry out assessments are similar to those used by other regulatory jurisdictions. The results of international assessments on substances are used to inform CEPA assessments.

If a substance is determined to be toxic or capable of becoming toxic as defined in section 64 of CEPA, then risk management instruments are considered to prevent or control risks identified. Follow-up activities may be undertaken for those substances recognized for their potential effects of concern.

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