On October 4, 2024, the Government of Canada took another important step to protect public health and the environment with the introduction of the Proposed Plan of Priorities under the Canadian Environmental Protection Act, 1999 (CEPA). In line with the modernization of CEPA, which received Royal Assent through Bill S-5, the Plan focuses on the assessment and management of substances in Canada with the goal of reducing risks to human health and the environment. The plan emphasizes the importance of transparency in the management of chemical substances that are integral to daily life but may pose risks if not carefully controlled. By prioritizing substances that may pose a risk to human health or the environment, the government aims to protect vulnerable populations and ecosystems.

Public consultations on the Proposed Plan of Priorities began on October 5, 2024 and will remain open until December 4, 2024. Environment and Climate Change Canada and Health Canada are seeking input from stakeholders including Indigenous communities, provinces, territories, industry and academia. This inclusive approach will ensure that diverse perspectives are considered as the plan is finalized.

Substances Prioritized for Assessment

The Proposed Plan of Priorities identifies key substances that require assessment based on their potential hazards. These include chemicals known to be carcinogenic, mutagenic, or toxic to reproduction, as well as those that may disrupt the endocrine system. The plan also targets substances that disproportionately affect certain populations or environments due to higher exposure or susceptibility. For example, chemicals capable of long-range transport, such as those affecting the Arctic region, are prioritized because of their potential to accumulate in ecosystems far from their sources.

The prioritization process uses a weight-of-evidence approach and applies the precautionary principle when conducting assessments. This ensures that the assessment process remains rigorous, with consideration for cumulative exposures and real-world impacts on human health and the environment.

List of Prioritized Substances

As part of the CEPA modernization, the government has identified a list of substances that will be prioritized for assessment. These substances were selected based on their potential hazards, such as carcinogenicity, mutagenicity, reproductive toxicity, and endocrine disruption. The prioritized substances include:

• Dichloromethane (DCM; CAS RN 75-09-2): A solvent used in industrial applications, known for its potential to cause liver and lung damage.

• Trichloroethylene (TCE; CAS RN 79-01-6): Commonly used to degrease metal parts, it poses significant risks to human health, including cancer.

• Styrene (CAS RN 98-83-9 and 100-42-5): Found in plastics and rubber, styrene has been linked to respiratory problems and nervous system effects.

• Tetrachloroethene (PERC; CAS RN 127-18-4): Widely used in dry cleaning, PERC has been linked to cancer and nervous system damage.

• Apigenin (CAS RN 520-36-5): A naturally occurring compound in some plants, under scrutiny for its effects on human health.

• 1,3,4,6,7,8-Hexahydro-4,6,6,7,8,8-hexamethyl-cyclopenta[g]-2-benzopyran (HHCB; CAS RN 1222-05-5): A fragrance ingredient suspected of accumulating in the environment and posing ecological risks.

Additionally, certain nanoscale substances such as Nanoscale silver (nAg; CAS RN 7440-22-4) and Nanoscale zinc oxide (nZnO; CAS RN 1314-13-2) are included due to their widespread use in consumer products and concerns about their long-term environmental effects.

Supporting Risk Management and Assessment

The Proposed Plan of Priorities outlines several initiatives to support the assessment and management of risks posed by substances. These include activities aimed at enhancing scientific methodologies, such as the development of non-animal testing methods and the integration of computational models. The government is also investing in research, monitoring and surveillance efforts to stay ahead of emerging risks and evolving scientific knowledge.

Additionally, the plan encourages public engagement through regular updates, workshops, and consultation processes to ensure transparency and inclusiveness in risk management activities. This includes gathering information from stakeholders to support the prioritization and assessment of substances.

In addition to assessment, the plan includes initiatives to promote the use of alternative testing methods, to reduce the reliance on vertebrate animal testing in favor of more ethical and advanced scientific approaches.

Reducing Animal Testing

In line with global trends, the Proposed Plan of Priorities emphasizes the need to replace, reduce, or refine vertebrate animal testing. The government is committed to developing scientifically justified alternative methods that can assess the potential harm of substances without relying on animal models. This strategy will be published in June 2025, following consultation with stakeholders and experts.

Introducing the Watch List

The Proposed Watch List, another key component of the plan, will identify substances that may not meet the criteria for toxicity but still pose potential risks. This list will be a resource for manufacturers, importers and consumers to make informed choices about the substances they use. It will be continuously updated as new information becomes available to help prevent harmful substances from becoming a bigger issue in the future.

Public Involvement and Feedback

Public input is essential to the success of the Proposed Plan of Priorities. Canadians are encouraged to participate in the consultation process, which runs until December 4, 2024. The government welcomes feedback on the list of prioritized substances, as well as on broader risk management strategies. The final plan will be published by June 2025, and ongoing updates will be provided to keep stakeholders informed of new developments.

The Government of Canada remains committed to promoting environmental justice and ensuring that all Canadians have access to a healthy environment. The modernization of CEPA and the introduction of the Proposed Plan of Priorities represent significant steps forward in the responsible management of substances and the protection future generations.

For more information on the Proposed Plan of Priorities and how to participate in the consultation process, visit the CEPA Registry on the Government of Canada website.

A recent study by Health Canada introduced a new metric called Cumulative Health Risk from Exposure Load (CHREL), which provides insight into the cumulative health risks posed by multiple chemical exposures. This metric is based on data from the Canadian Health Measures Survey (CHMS) and uses Human Biomonitoring Health-Based Guidance Values (HB2GVs) as thresholds to evaluate the potential health risks from chemical exposures in a population. The findings suggest that a significant portion of the Canadian population may be exposed to chemicals at levels potentially above the HB2GVs, raising concerns about cumulative health risks.

Understanding CHREL: A New Approach to Chemical Exposure

CHREL builds on the concept of Exposure Load (EL), which identifies how many chemicals an individual is exposed to at levels above a certain threshold. CHREL takes this further by integrating HB2GVs, which are exposure thresholds derived from toxicological studies, to evaluate the health risks of chemical mixtures.

By applying HB2GVs, the CHREL metric indicates the number of chemicals detected in an individual that exceeds the health-protective guidance values. The study focused on 18 chemicals measured in CHMS cycles 3 and 4 (2012–2013 and 2014–2015), including mercury, benzene, acrylamide and triclosan. These chemicals have been linked to adverse health effects on the liver, nervous system, and cancer risk.

Key Findings: Chemical Exposures in Canada

The CHREL analysis revealed that more than half of the Canadian population had a CHRELTOTAL score of 1 or higher, indicating exposure to one or more chemicals at levels above the health-based thresholds. Certain subgroups were found to be at higher risk:

• Males had significantly higher CHREL scores compared than females.

• Smokers had notably higher CHREL scores than non-smokers, indicating increased exposure to harmful chemicals.

• Younger age groups (12–19 years) had lower CHREL scores compared to older age groups, especially those aged 40–59.

Small segments of the population also showed higher CHRELLIVER and CHRELNERV scores, which assess risks to the liver and nervous system, respectively. For cancer risk, the study introduced CHRELCANC, based on six chemicals linked to cancer endpoints. Most of the population had an estimated CHRELCANC score of 3, indicating potential exposure to multiple chemicals above negligible cancer risk levels.

Chemicals Driving Health Risks

The study identified several key chemicals that contribute significantly to health risks in the Canadian population:

• Inorganic arsenic was the leading contributor to elevated CHREL scores in the population.

• Mercury, acrylamide, benzene and xylenes were also notable contributors to the overall chemical burden.

• For smokers, the most critical chemicals were inorganic arsenic, benzene, and cadmium, which drove the higher CHREL scores in this group.

Public Health and Policy Implications

The CHREL metric provides a novel way to assess the cumulative health risks of chemical exposures in a population. This information can help guide risk management and regulatory decisions by identifying chemicals that pose the greatest threats to public health. For instance, reducing exposure to inorganic arsenic and other high-risk chemicals could have a significant impact on reducing overall health risks.

The findings underscore the importance of continued biomonitoring efforts, as well as research on how chemical exposures interact to affect human health. Additionally, the study highlights the need for targeted interventions to reduce chemical exposures in vulnerable subpopulations, such as smokers and the elderly.

Limitations and Future Research

While CHREL provides valuable insights, the study has several limitations. The metric relies on available data for a limited number of chemicals, and further research is needed to expand the range of chemicals analyzed. Additionally, the HB2GVs used in the analysis may vary depending on the methods used to derive them, and more work is needed to standardize these values across different chemicals.

Moreover, CHREL does not indicate the level of exposure for each chemical, only whether the exposure exceeds the health-based threshold. As research on chemical interactions and cumulative risk advances, future updates to the CHREL methodology may provide even more refined insights into population-level chemical exposures.

Conclusion: A Step Toward Better Chemical Risk Management

CHREL represents a significant step forward in understanding the cumulative health risks posed by multiple chemical exposures. By integrating biomonitoring data with health-based guidance values, CHREL provides a clearer picture of the chemical exposures of the Canadian population. This metric can serve as a valuable tool for public health officials, researchers, and policy makers to assess and manage the risks associated with chemical exposures, ultimately contributing to improved health outcomes and stronger environmental protection.

The full study can be found here.