Canada Gazette, Part I, Volume 157, Number 11: Order Adding a Toxic Substance to Schedule 1 to the Canadian Environmental Protection Act, 1999

March 18, 2023

Statutory authority
Canadian Environmental Protection Act, 1999

Sponsoring departments
Department of the Environment
Department of Health


(This statement is not part of the Order.)


Free cyanide and precursors of free cyanide meet the ecological criterion for a toxic substance as set out in paragraph 64(a) of the Canadian Environmental Protection Act, 1999 (CEPA or “the Act”). In accordance with subsection 90(1) of CEPA, the Minister of the Environment and the Minister of Health (the ministers) are recommending that the Governor in Council make an order adding free cyanide, cyanide salts and cyanide complexes to Schedule 1 to the Act (the List of Toxic Substances).


The Chemicals Management Plan (CMP) is a federal program that assesses and manages chemical substances and micro-organisms that may be harmful to the environment or human health. The ministers assessed cyanides in accordance with section 68 or 74 of CEPA as part of the CMP.

Free cyanide, consisting of the cyanide anion and hydrogen cyanide, is considered the moietyfootnote 1 of concern for cyanides in the ecological assessment. Free cyanide and precursors of free cyanide considered in the ecological assessment include, but are not limited to, the 10 substances in Table 1 below. Precursors to free cyanide are substances, such as cyanide salts and cyanide complexes, that contain the cyanide moiety and that can degrade to free cyanide at environmentally, industrially or physiologically relevant conditions. Based on the conclusions of the screening assessment, the ministers are proposing to add free cyanide, cyanide salts and cyanide complexes to Schedule 1 to CEPA.

Table 1: Substances assessed in the Cyanides Group
No. CAS RN table a1 note a Domestic Substances List name Common name(s)
1 74-90-8 Hydrocyanic acid Hydrogen cyanide
2 143-33-9 Sodium cyanide Sodium cyanide
3 506-61-6 Argentate(1-), bis(cyano-C)-, potassium Potassium dicyanoargentate
4 13601-19-9 Ferrate(4-), hexakis(cyano-C)-, tetrasodium, (OC-6-11) Tetrasodium ferrocyanide (Yellow prussiate of soda)
5 13746-66-2 Ferrate(3-), hexakis(cyano-C)-, tripotassium, (OC-6-11)- Tripotassium ferricyanide
6 13943-58-3 Ferrate(4-), hexakis(cyano-C)-, tetrapotassium, (OC-6-11)- Tetrapotassium ferrocyanide (Yellow prussiate of potash)
7 13967-50-5 Aurate(1-), bis(cyano-C)-, potassium Potassium dicyanoaurate
8 14038-43-8 Ferrate(4-), hexakis(cyano-C)-, iron(3+) (3:4), (OC-6-11)- Ferric ferrocyanide (Prussian blue, insoluble)
9 25869-00-5 Ferrate(4-), hexakis(cyano-C)-, ammonium iron(3+) (1:1:1), (OC-6-11)- Ferric ammonium ferrocyanide
10 25869-98-1 Ferrate(4-), hexakis(cyano-C)-, iron(3+) potassium (1:1:1), (OC-6-11)- Potassium ferric ferrocyanide
(Prussian blue, soluble or Turnbull’s blue)

Table a1 note(s)

Table a1 note a

The Chemical Abstracts Service Registry Number (CAS RN) is the property of the American Chemical Society, and any use or redistribution, except as required in supporting regulatory requirements and/or for reports to the Government of Canada when the information and the reports are required by law or administrative policy, is not permitted without the prior, written permission of the American Chemical Society.

Return to table a1 note a referrer

Description, uses, and sources of release

The physical and chemical properties of cyanides are diverse. A number of cyanides occur naturally in the environment with hydrogen cyanide and sodium cyanide being more water-soluble than complex cyanides.

The Department of the Environment and the Department of Health (the departments) issued a mandatory survey under section 71 of CEPAfootnote 2 encompassing the substances listed in Table 1 (reporting year 2011). Information reported by industry for 2011 indicated these substances were not intentionally manufactured for commercial purposes in Canada, though 1 000 to 10 000 tonnes of hydrogen cyanide were incidentally manufactured. Incidental manufacturing of cyanides occurs in certain sectors where high temperature and high pressure processes are used, for example, during iron and steel manufacturing in coke ovens, in blast furnaces in integrated mills and during aluminum smelting. Industry also reported imports of cyanides in the 2011 survey of 10 000 to 50 000 tonnes. Sodium cyanide represented the vast majority of the total quantity of imports according to responses received. Data obtained from the Canada Border Services Agency for years 2012 and 2013 indicated that over 30 000 tonnes of sodium cyanide were imported in each year.

Information reported by industry for 2011 indicated that uses of hydrogen cyanide and sodium cyanide in Canada are limited to industrial applications, including extraction of gold from ore/mining applications, oil and gas extraction and as solid separation agents.footnote 3 Metal-cyanide complexes (substances 3 through 10 in Table 1) were reported to be used in industrial applications and in products available to consumers, including corrosion inhibitors and anti-scaling agents, dyes, oil and natural gas extraction, paints and coatings, personal care products and solid separation agents. Ferrocyanide salts (i.e. tetrasodium ferrocyanide and its decahydrate, tetrapotassium ferrocyanide and ferric ferrocyanide), of which tetrasodium ferrocyanide is predominant, are used in road salts in Canada as anticaking agents. In addition, tetrasodium ferrocyanide and tetrapotassium ferrocyanide are approved food additives with limited permitted uses.

The environmental fatefootnote 4 of free cyanide and precursors of free cyanide is complex. It depends jointly on the type of cyanide in question and the environmental conditions that influence their partitioning between various environmental media. Cyanide salts and cyanide complexes have the potential to release free cyanide under certain environmental conditions and processes. Free cyanide and precursors of free cyanide are released to the environment (primarily to air and water) from several industrial sectors, but the main sources of release addressed in the screening assessment are from the metal mining, iron and steel manufacturing and road salt sectors, which release these substances to the environment in effluent, or runoff.

Current risk management activities


The Canadian Water Quality Guidelines, developed by the Canadian Council of Ministers of the Environment, set recommended maximum values of free cyanide in fresh water to protect aquatic life. Schedule 4 of the Metal and Diamond Mining Effluent Regulations (MDMER) prescribes a maximum authorized monthly mean concentration of total cyanide in effluent from a mine’s final discharge point. The Environmental Code of Practice for Metal Mines supports the MDMER and includes recommendations for the management of cyanides and refers to the International Cyanide Management Code developed by the United Nations.

The departments also developed the Code of Practice for the Environmental Management of Road Salts, which indirectly controls the release of ferrocyanides used in road salts (substances 4, 6, and 8 in Table 1) to the environment through best management practices included in individual salt management plans. In addition, the Department of the Environment published the Environmental Code of Practice for Integrated Steel Mills and lists performance standards for atmospheric emissions, water and wastewater, wastes, and environmental management practices for new integrated steel mills. The province of Ontario also has its own individual Environmental Compliance Approvals, which replaced Ontario Regulation 214/95, entitled Effluent Monitoring and Effluent Limits — Iron and Steel Manufacturing Sector (Government of Ontario, 1995), and monitor and control the quality of effluent discharged from iron and steel plants in Ontario.


In metal mining, the use of a process called “heap leaching,” which uses cyanides in facilities and surface operations, has been restricted in certain jurisdictions in the United States (Montana and Colorado), as well as in some countries, including Germany and the Czech Republic. A European Union Directive has set out limits for cyanide in tailing ponds and limits for discharge waste from mines containing cyanide. The United Nations also developed the International Cyanide Management Code for the Manufacture, Transport, and Use of Cyanide in the Production of Gold, which is a voluntary program for gold and silver mining companies. The program focuses on the safe management of cyanides and requires that companies that adopt the code have their operations audited so they can be certified.

Summary of the screening assessment

A screening assessment of cyanides was conducted to determine whether these substances meet one or more of the criteria for a toxic substance as set out in section 64 of CEPA (i.e. to determine if the substances could pose a risk to the environment or human health in Canada).

Under section 64 of CEPA, a substance is considered toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that

The departments collected and considered information from multiple sources (e.g. literature reviews, internal and external database searches, modelling, data from mandatory surveys issued under section 71 of CEPA and, where warranted, data from targeted follow-ups with stakeholders) to inform the screening assessment conclusion. The ecological and human health portions of the screening assessment have undergone external peer review and been the subject of consultation with academics and other relevant stakeholders.

The screening assessment concluded that free cyanide and precursors of free cyanide meet the ecological criterion for a toxic substance as set out in paragraph 64(a) of CEPA and, therefore, constitute a risk to the environment in Canada. Below are summaries of the ecological and human health assessments.

Summary of the ecological assessment

Free cyanide, consisting of the cyanide anion and hydrogen cyanide, is generally more hazardous than cyanide complexes and is considered the moiety of concern for cyanides for the ecological assessment. Hydrogen cyanide disrupts energy metabolism in organisms and it is highly toxic to aquatic organisms, adversely affecting their growth, reproduction and survival. Acute and chronic toxicity data for hydrogen cyanide were identified from several studies across multiple species of algae, aquatic plants, amphibians, protozoa, invertebrates and fish. The predicted no-effect concentration (PNEC) for free cyanide in fresh water was derived using chronic toxicity endpoints for 12 aquatic species. Data on the ecotoxicity of free cyanide in soil are limited and restricted to plants and invertebrates. The ecological assessment identified no studies on the ecotoxicity of cyanides in sediment, but it is expected that exposure from sediment is relatively minor compared to the exposure from water; therefore, the ecological assessment focused on effects related to organisms in the water column. Overall, the screening assessment found that cyanides have the potential to cause adverse effects in aquatic organisms.

The ecological exposure assessment focused on potential releases of cyanides to the environment from metal mining, iron and steel manufacturing, and application of cyanide-containing road salt, three sectors in which large quantities of cyanides are used or produced and may be released into the aquatic environment through effluent, or runoff (in the case of road salt application). To determine if activities in these sectors may pose an ecological risk, risk quotients were calculated as the ratio between the predicted environmental concentrations (PECs) and PNECs for cyanides in aquatic environments. When PEC values are greater than PNEC values, it is indicative of a potential for ecological harm in the exposure scenario in question. The screening assessment estimated PECs for the three sectors using measured or model-estimated concentrations of cyanide in the aquatic environment. Based on the risk quotient analyses and consideration of additional lines of evidence (such as information on fate, persistence, toxicity and sources of cyanide exposure), the screening assessment concluded that concentrations of cyanides in the environment resulting from activities in the three sectors may cause harm to aquatic organisms.

The screening assessment concluded that free cyanide and precursors of free cyanide meet the ecological criterion for a toxic substance as set out in paragraph 64(a) of CEPA, but do not meet the criterion set out in paragraph 64(b). The screening assessment also determined that free cyanide and precursors of free cyanide meet the persistence criteria but not the bioaccumulation criteria as set out in the Persistence and Bioaccumulation Regulations.

Summary of the human health assessment

For the human health assessment, potential exposures to free/simple cyanides (first 2 substances in Table 1) and certain metal-cyanides from the environment (for example hydrogen cyanide in air), food, and the use of products were considered.

Based upon a comparison of levels to which Canadians can be exposed to the free/simple cyanides subgroup and levels associated with health effects, it was determined that the risk to human health for these 2 substances is considered to be low.

As a result of this assessment, the risk to human health is also considered to be low for the remaining 8 metal-cyanide complexes (single-iron, multi-iron, and gold- or silver- cyanide complexes). Exposures were either not expected or negligible, or adverse health effects were not expected for these 8 substances (substances 3 through 10 in Table 1).

The screening assessment concluded that the 10 substances assessed in the Cyanide Group do not meet the human health criterion for a toxic substance set out in paragraph 64(c) of CEPA.


The objective of the proposed Order Adding a Toxic Substance to Schedule 1 to the Canadian Environmental Protection Act, 1999 (the proposed Order) is to add free cyanide, cyanide salts and cyanide complexes to Schedule 1 to CEPA, which would enable the ministers to propose risk management measures for a toxic substance under CEPA to manage potential environmental risks associated with these substances.


The proposed Order would add free cyanide, cyanide salts and cyanide complexes to Schedule 1 to CEPA (the List of Toxic Substances).

Regulatory development


On February 10, 2018, the ministers published a Notice with a summary of the draft screening assessment of free cyanide and precursors of free cyanide (which included a link to the complete draft screening assessment) in the Canada Gazette, Part I, for a 60-day public comment period. The Notice also informed about the publication of the risk management scope for free cyanide and precursors of free cyanide to initiate discussions with stakeholders on the development of risk management options, following their addition to Schedule 1 to CEPA. During this period, 10 submissions were received on the draft screening assessment and risk management scope. A table summarizing the complete set of comments received and the response to these comments is available on the (Chemical substances) website.

Some comments from industry indicated that stakeholders agreed with the screening assessment’s conclusion that there is a risk of harm to the environment from cyanides, including free cyanides and precursors of free cyanide. Others did not oppose the listing, but disagreed with the scientific approaches considered in the screening assessment. Two submissions from industry indicated concern that the conclusion about toxicity would also apply to multi-metal cyanide complexes (also considered precursors of free cyanide) used in pigments. Government officials did not determine the use of pigments containing multi-metal cyanide complexes to be a source of concern for the environment. Risk management of these substances is therefore not currently proposed. One comment from industry also requested an exclusion from the Schedule 1 listing for tetrasodium ferrocyanide, since it is completely consumed during the production of copper ferrocyanide. Government officials responded that, while this use of the substance was not identified as an ecological concern, there are other uses of the substance (e.g. in road salts) that could release free cyanides into the environment.

Stakeholders provided new information and comments on the methodology used in the screening assessment, and raised concern about risk quotient calculations comparing total cyanide concentrations to the PNEC based on free cyanide. Stakeholders also raised concern that concentrations of cyanides found near mining facilities may have been influenced by other sources (e.g. forest fires, road salts), which was not taken into consideration. Concern was also raised regarding the statistical approach used to address analytical measurements below the method detection limit (i.e. non-detects).

In response, the departments updated the screening assessment where applicable, such as adding text related to the consideration of total cyanide concentrations for exposure and risk characterization. Government officials also provided additional references supporting the photodissociation of components of total cyanide, to further address stakeholder comments regarding the use of total cyanide concentrations in the ecological exposure assessment. Text was added regarding the potential influence of ambient concentrations of cyanide in the metal mining sector and figures and text were updated with respect to non-detect measurements. These comments were considered in the development of the final screening assessment, but did not change the conclusion that free cyanide and precursors of free cyanide meet the criterion set out in paragraph 64(a) of CEPA.

Other comments received pertained to the management of the ecological risk posed by free cyanide and precursors of free cyanide. The Department of the Environment considered these comments during the development of the risk management approach for free cyanide and precursors of free cyanide. Comments derived from public, partner and stakeholder consultations will continue to be considered during the development of any risk management instrument associated with the substance.

The departments informed the provincial and territorial governments about all publications by letter to the CEPA National Advisory Committee (CEPA NAC)footnote 5 and provided them with an opportunity to comment. No comments were received from CEPA NAC.

Modern treaty obligations and Indigenous engagement and consultation

An assessment of modern treaty implications conducted in accordance with the Cabinet Directive on the Federal Approach to Modern Treaty Implementation concluded that orders adding substances to Schedule 1 to CEPA do not introduce any new regulatory requirements, and, therefore, do not result in any impact on modern treaty rights or obligations. As a result, specific engagement and consultations with Indigenous Peoples were not undertaken. However, the prepublication comment period is an opportunity for Indigenous Peoples to provide feedback on the proposed Order, which is open to all Canadians.

Instrument choice

When a substance meets one or more of the criteria for a toxic substance as set out in section 64 of CEPA, the ministers shall propose one of the following options under subsection 77(2) of CEPA:

When proposing option (c), the ministers shall recommend the implementation of virtual elimination if the substance was assessed under section 74 of CEPA and, as set out in subsection 77(4) of CEPA, if the ministers are satisfied that

The implementation of virtual elimination does not apply to free cyanide and precursors of free cyanide, as some of the substances are naturally occurring inorganic substances and were found to be persistent, but not bioaccumulative. Based on the available evidence, the ministers determined that it is not appropriate to manage the potential ecological risks associated with the substance by taking no further actions or adding free cyanide and precursors of free cyanide to the Priority Substances List [option (a) or option (b)]. Therefore, the ministers are recommending that free cyanide, cyanide salts and cyanide complexes be added to Schedule 1 to CEPA [option (c)]. An order is the only available instrument to implement this recommendation.

Regulatory analysis

Benefits and costs

The addition of free cyanide, cyanide salts and cyanide complexes to Schedule 1 to CEPA would not on its own impose any regulatory requirements on businesses and therefore, would not result in any incremental compliance costs for stakeholders or enforcement costs for the Government of Canada. The proposed Order would grant the ministers the authority to develop risk management instruments under CEPA for these substances. The Government of Canada would consult stakeholders on any future risk management instruments before implementation and would consider their potential impacts.footnote 8

Small business lens

Analysis under the small business lens concluded that the proposed Order would not impact Canadian small businesses, as it would not impose any administrative or compliance costs on businesses.

One-for-one rule

The one-for-one rule does not apply, as the proposed Order would not result in a change in administrative burden imposed on businesses.

Regulatory cooperation and alignment

Canada cooperates with other international organizations and regulatory agencies for the management of chemicals (e.g. the United States Environmental Protection Agency, the European Chemicals Agency and the Organisation for Economic Cooperation and Development). While the proposed Order would not on its own relate to any international agreements or obligations, it would enable the ministers to propose risk management measures that may align with actions undertaken by other jurisdictions.

Strategic environmental assessment

In accordance with the Cabinet Directive on the Environmental Assessment of Policy, Plan and Program Proposals, a strategic environmental assessment was completed for the CMP, inclusive of orders adding substances to Schedule 1 to CEPA. The assessment concluded that the CMP is expected to have a positive effect on the environment and human health.

Gender-based analysis plus

No gender-based analysis plus (GBA+) impacts have been identified for the proposed Order.

Implementation, compliance and enforcement, and service standards

As no specific risk management measures are recommended as part of the proposed Order, developing an implementation plan and a compliance and enforcement strategy, as well as establishing service standards, are not necessary at this time.


Thomas Kruidenier
Acting Executive Director
Program Development and Engagement Division
Environment and Climate Change Canada
Gatineau, Quebec
K1A 0H3
Substances Management Information Line:
1‑800‑567‑1999 (toll-free in Canada)
819‑938‑3232 (outside of Canada)

Andrew Beck
Risk Management Bureau
Health Canada
Ottawa, Ontario
K1A 0K9
Telephone: 613‑266‑3591


Notice is given, pursuant to subsection 332(1)footnote a of the Canadian Environmental Protection Act, 1999 footnote b, that the Governor in Council, on the recommendation of the Minister of the Environment and the Minister of Health proposes to make the annexed Order Adding a Toxic Substance to Schedule 1 to the Canadian Environmental Protection Act, 1999 under subsection 90(1) of that Act.

Any person may, within 60 days after the date of publication of this notice, file with the Minister of the Environment comments with respect to the proposed Order or a notice of objection requesting that a board of review be established under section 333 of that Act and stating the reasons for the objection. Persons filing comments are strongly encouraged to use the online commenting feature that is available on the Canada Gazette website. Persons filing comments by any other means, and persons filing a notice of objection, should cite the Canada Gazette, Part I, and the date of publication of this notice, and send the comments or notice of objection to the Executive Director, Program Development and Engagement Division, Department of the Environment, Gatineau, Quebec K1A 0H3 (email:

A person who provides information to the Minister may submit with the information a request for confidentiality under section 313 of that Act.

Ottawa, March 9, 2023

Wendy Nixon
Assistant Clerk of the Privy Council

Order Adding a Toxic Substance to Schedule 1 to the Canadian Environmental Protection Act, 1999


1 Schedule 1 to the Canadian Environmental Protection Act, 1999 footnote b is amended by adding the following in numerical order:

Coming into Force

2 This Order comes into force on the day on which it is registered.

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