Canada’s Air Pollutant Emissions Inventory Report 2025: chapter 1

Introduction

1.1 Background on the Air Pollutant Emissions Inventory

Canada’s Air Pollutant Emissions Inventory (APEI) is a comprehensive inventory of air pollutant emissions at the national, and provincial and territorial levels. The APEI is prepared and published by Environment and Climate Change Canada (ECCC) and serves many purposes, mainly by:

• contributing to tracking and quantifying air pollutants in accordance with Canada’s domestic and international reporting obligations;
• supporting the development of domestic air quality management strategies, policies and regulations;
• informing Canadians about pollutants that affect their health and the environment; and
• providing data to support air quality forecasting.

The first national inventory of air pollutant emissions in Canada was compiled in 1973, with national, provincial, and territorial estimates of emissions of carbon monoxide (CO), sulphur oxides (SO_x), nitrogen oxides (NO_x), hydrocarbons and particulate matter (PM) for the year 1970. Since then, air pollutant emissions estimates for Canada have continued to be published on a regular basis.

Today, the APEI includes emissions data for 17 air pollutants that contribute to smog, acid rain and diminished air quality, including:

• smog precursors: total particulate matter (TPM), PM less than or equal to 10 microns (PM₁₀), PM less than or equal to 2.5 microns (PM_2.5), SO_x, NO_x, volatile organic compounds (VOCs), CO and ammonia (NH₃)
• heavy metals: mercury (Hg), lead (Pb) and cadmium (Cd)
• persistent organic pollutants (POPs): dioxins and furans, four polycyclic aromatic hydrocarbon (PAHs) compounds (benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene and indeno(1,2,3-cd)pyrene), and hexachlorobenzene (HCB)

The reporting format for the APEI organizes emissions into 11 source categories that are further broken down into 73 sectors and 75 associated subsectors (Table 1–1). The APEI is compiled and published on an annual basis. The time series of annual emissions contained in this report is updated from 1990 to the most recent inventory year, to ensure the trends in emissions are based on consistent and current methodological approaches and data.

The APEI is compiled from many different data sources. Emissions data reported by individual facilities to ECCC’s National Pollutant Release Inventory (NPRI) are supplemented with well-documented, science-based estimation tools and methodologies to quantify total emissions. Together, these data sources provide a comprehensive coverage of air pollutant emissions across Canada.

Table 1–1: Air Pollutant Emissions Inventory Sector Descriptions

1.2 Reporting Requirements

The Convention on Long-range Transboundary Air Pollution (CLRTAP) endeavours to limit and, as far as possible, gradually reduce, and prevent air pollution. Since it was originally signed in 1979, the CLRTAP has been extended to a total of eight protocols, of which Canada has ratified seven. Six of these identify measures to be taken by Parties to achieve the Convention’s objectives and the seventh concerns financing. Canada is a Party to the following six protocols that identify measures under the Convention:

• the 1985 Helsinki Protocol on the Reduction of Sulphur Emissions (SO_x)
• the 1994 Oslo Protocol on Further Reduction of Sulphur Emissions (SO_x for a designated “Sulphur Oxides Management Area” [SOMA])
• the 1988 Sofia Protocol concerning the Control of Emissions of Nitrogen Oxides (NO_x)
• the 1998 Aarhus Protocol on Heavy Metals (Cd, Pb and Hg)
• the 1998 Aarhus Protocol on Persistent Organic Pollutants (including dioxins and furans, four species of PAHs, and HCB, among other POPs)
• the 1999 Gothenburg Protocol (Protocol to Abate Acidification, Eutrophication and Ground-level Ozone) and its 2012 amended version (which covers emissions of six^{Footnote 1}  pollutants: SO₂, NO_x, VOCs, NH₃, PM and black carbon)

These protocols set specific emissions reduction targets for sulphur, NO_x, Cd, Pb, Hg, dioxins and furans, PAHs, HCB, and VOCs. Parties are required to report emissions data to the United Nations Economic Commission for Europe (UNECE) each year by February 15 and submit the APEI Report by March 15. More information on the submission to the UNECE and emission reduction commitments can be found in Annex 4.

In addition, Canada collects and publishes data on emissions of NH₃, CO and three categories of PM (TPM, PM₁₀ and PM_2.5) and voluntarily reports the emissions of these five substances, along with the 12 substances for which there are protocols, to the UNECE annually. Canada has ratified the 1984 Geneva Protocol on Long-Term Financing of the Cooperative Programme for Monitoring and Evaluation of the Long-Range Transmission of Air Pollutants in Europe.

Canada and the United States work jointly to address shared concerns regarding transboundary air pollution. Under the Canada-U.S. Air Quality Agreement, Canada monitors and reports emissions of SO₂, NO_x and VOCs other than methane.

In keeping with international reporting requirements, Canada’s emissions of air pollutants from aircrafts at cruising altitudes, as well as emissions from international marine navigation are presented separately from other sources of emissions in this report and are excluded from Canada’s national total emissions (see Annex 4 for more information).

1.3 Canada’s Air Emissions Regulations and Non-Regulatory Measures

Downward trends in emissions of air pollutants reflect the ongoing implementation of a wide range of regulatory and non-regulatory instruments that aim to reduce or eliminate pollutants in order to improve and maintain air quality in Canada. Regulations under the Canadian Environmental Protection Act, 1999 (CEPA 1999) related to the 17 APEI pollutants include, but are not limited to, the following:

• Benzene in Gasoline Regulations
• Contaminated Fuel Regulations
• Export of Substances on the Export Control List Regulations
• Gasoline and Gasoline Blend Dispensing Flow Rate Regulations
• Gasoline Regulations
• Marine Spark-Ignition Engine, Vessel and Off-Road Recreational Vehicle Emission Regulations
• Multi-Sector Air Pollutants Regulations
• Off-Road Compression-Ignition (Mobile and Stationary) and Large SparciteIgnition Engine Emission Regulations
• Off-Road Small Spark-Ignition Engine Emission Regulations
• On-Road Vehicle and Engine Emission Regulations
• Products Containing Mercury Regulations
• Pulp and Paper Mill Effluent Chlorinated Dioxins and Furans Regulations
• Renewable Fuels Regulations
• Secondary Lead Smelter Release Regulations
• Sulphur in Diesel Fuel Regulations
• Sulphur in Gasoline Regulations
• Volatile Organic Compound (VOC) Concentration Limits for Architectural Coatings Regulations
• Volatile Organic Compound (VOC) Concentration Limits for Automotive Refinishing Products Regulations
• Volatile Organic Compound Concentration Limits for Certain Products Regulations

A number of greenhouse gas regulations are also expected to achieve significant co-benefit reductions in air pollutants, including Canada’s Reduction of Carbon Dioxide Emissions from Coal-fired Generation of Electricity Regulations and Regulations Respecting Reduction in the Release of Methane and Certain Volatile Organic Compounds (Upstream Oil and Gas Sector).

Non-regulatory instruments include guidelines for new stationary combustion turbines, codes of practice, performance agreements, and/or pollution prevention planning notices for various sectors. These instruments address emissions from a number of sectors including aluminium, iron, steel and ilmenite, iron ore pellets, potash, base-metals smelting and refining, and pulp and paper.

Additionally, there is an International Maritime Organization (IMO) limit, known as “IMO 2020,”^{Footnote 2}   that came into force in 2020. This regulation restricts the amount of sulphur in the fuel oil used by ships travelling outside of specified Emission Control Areas (ECAs).^{Footnote 3}  This  limit was implemented under an amendment to the Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL). A set of guidelines for the implementation of the MARPOL regulation was developed by the IMO. In 2024, further amendments^{Footnote 4}  were made to Annex VI to designate the Canadian Arctic Waters as an ECA. These amendments, which will take effect on March 1, 2026, place more stringent NO_x, SO_x, and PM emission limits on ships operating in this region.

All regulations and non-regulatory instruments administered under CEPA 1999 are available on the environmental registry^{Footnote 5}  and on the Department of Justice’s online consolidation of federal acts and regulations.^{Footnote 6}