Risk assessment of chemical substances


Substances, such as chemicals, polymers, and products of biotechnology, have many different properties and many different uses. Some are used to make plastics flexible. Some help to put out fires quickly and efficiently. Some are products of common chemical reactions that occur naturally in the environment. Still others form as part of our day-to-day activities, such as driving a car.

In the same way that substances have different uses, some can also be harmful in different ways. For instance, some may harm plants, while some may cause very serious illnesses in people, 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 by its hazardous properties and how or where exposure takes place. Scientific evaluations, or risk assessments are conducted under the Canadian Environmental Protection Act, 1999 (CEPA 1999) to determine whether there are risks resulting from exposure of people or releases into the environment, and the specific ways people or the environment can be affected.

The CEPA 1999 Risk Assessment Process

The Minister of Health and the Minister of Environment and Climate Change conduct risk assessments of substances present in Canada (existing substances) or proposed for introduction to the Canadian market (new substances) to determine whether these substances present or may present a risk to the environment or to human health. Decisions are based on a scientific evaluation of the risk posed by a substance, which considers both the hazardous properties of the substance (such as cancer-causing properties or toxicity to aquatic organisms) and the potential for exposure of the population or the environment to the substance. This allows the Government of Canada to identify whether or not a control is needed, and if so, what type of control is best suited for avoiding, reducing or preventing the potential harm.

Each substance is unique and some are more complex than others. The unique characteristics of substances need to be considered when making decisions about the need for control or elimination. For example, it might be very easy to assess a substance that has a single use. It gets more complicated, though, for substances that have many different uses, enter the environment in many different ways, and may affect humans or non-human organisms differently depending on how they are encountered in the environment.

Therefore, the nature and scope of a risk assessment may vary depending on the section of CEPA 1999 under which it is mandated and the complexity of the issues involved. As a result, there are various types of risk assessment documents that may be produced, such as those developed as part of the Risk Assessment Toolbox.

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Principles and Approaches

In conducting a risk assessment, a weight of evidence approach and precaution are applied. All relevant information is considered across multiple lines of evidence, along with uncertainties.

Information on how much of a substance may enter the environment as well as its chemical properties provides key evidence about how the substance may distribute in the environment, how long it will remain in the environment, and whether it can harm humans or the environment through exposure. How humans or the environment may be exposed to the substance is evaluated. Different approaches for characterizing exposure may be used depending on the information available regarding sources, uses, handling and disposal of the substance.

The potential effects of the substance on humans 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 impairment, and carcinogenicity) are identified. A combination of qualitative and quantitative approaches may be used to characterize the overall risk of a substance. Data generated through laboratory or field testing, modelling approaches and data from other substances that are structurally and/or functionally similar to the substance being assessed are all used, as appropriate. The results inform both ecological and human health assessments.

Approaches used to carry out risk assessments are similar to those used by other regulatory jurisdictions. Evolving science and new tools and approaches are considered to efficiently and consistently produce technically sound assessments. The results of international assessments on substances will also be used to inform CEPA risk assessments.

The Risk Assessment Process for Existing Substances

An essential first step in risk assessment is the collection of information on each substance or substance group. Information-gathering encompasses 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 national or international agencies. Information is also generated by government researchers or stakeholders carrying out studies, testing and monitoring of substances. 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.

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

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The Risk Assessment Process for New Substances

New substances undergo ecological and human health risk assessments before entering the Canadian marketplace. This process begins with a pre-import or pre-manufacture notification of the substance. This means that any person 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 as described above, in considering the principles and assessment components but with some key differences. See the New Substances Program for more information.

CEPA 1999 Conclusions

For the purposes of section 64 in Part 5 of CEPA 1999, a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that:

  • a) have or may have an immediate or long-term harmful effect on the environment or its biological diversity;
  • b) constitute or may constitute a danger to the environment on which life depends; or
  • c) constitute or may constitute a danger in Canada to human life or health.

A conclusion is made for a substance or group of substances considering the relevant information available and recognizing uncertainties. Maintaining transparency is key to a credible assessment process. Therefore, uncertainties as well as the approaches or assumptions made in dealing with those uncertainties are explicitly noted in the assessment report and are considered in coming to a conclusion.

If a substance is determined to be toxic or capable of becoming toxic as defined in section 64 of CEPA 1999, then risk management measures are considered to reduce, eliminate or prevent risks identified. Follow up activities may be undertaken for those substances recognized for their potential effects of concern.

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