Canada’s Air Pollutant Emissions Inventory Report 2025: chapter 2

2023 Emissions and Trends

This chapter describes the main sources and sectors contributing to the emissions of each pollutant and their historical trends. The descriptions of source categories and sectors are provided in Chapter 1, Table 1–1.

The contribution of each source category and sector to total emissions of air pollutants for 2023 varies by pollutant
(Table 2–1).^{Footnote 1} 

Table 2–1: Main Contributor by Source for Each Air Pollutant (2023)

Note:
a. PAH includes B(a)p, B(b)f, B(k)f, I(1 ,2,3-cd)p.

This edition of the Air Pollutant Emissions Inventory Report summarizes the most recent estimates of air pollutant emissions for 1990 to 2023, as of February 2025. The inventory indicates that emissions of 14 of the 17 reported air pollutants are decreasing compared to historical levels. Some key emission sources contributed to the downward trends since 1990, more specifically:

• In the Ore and Mineral Industries:
  • Non-Ferrous Refining and Smelting Industry contributed to the decreases in emissions of Hg, Cd, SO_x and Pb: emissions of these pollutants from this source have decreased by 99%, 97%, 95% and 93%, respectively, in part owing to the closure of outdated smelters and implementation of pollution prevention measures.
  • The Aluminium Industry contributed to the decreases in emissions of PAHs: emissions from this source have decreased by almost 100%, in part owing to process improvements and to the progressive phase-out of old Söderberg aluminium production technologies.
• In the Transport and Mobile Equipment category, Light-Duty Gasoline Trucks and Vehicles contributed to the decreases in VOC and CO emissions, and Heavy-Duty Diesel Vehicles, to decreases in emissions of NO_x: emissions of these pollutants from these sources have decreased by 91%, 79% and 65%, respectively.
  • Despite a 168% increase in total vehicle kilometres travelled (VKT) from Heavy-Duty Diesel Vehicles and a 28% increase in the total fuel consumption of Light-Duty Gasoline Trucks and Vehicles, emissions have decreased due to improved fuel economy and implemented regulations that have effectively lowered NO_x, CO and hydrocarbon emissions from engines.
• Changes in farming practices related to the production of annual agricultural crops contributed to emission decreases of PM_2.5; emissions from this source have decreased by 49%, in part owing to reductions in areas under summer fallow and the adoption of conservation tillage practices.
• Waste Incineration contributed to the decreases in emissions of HCB and dioxins and furans; emissions of these pollutants from this source have decreased by 93% and 83%, respectively, in part owing to improvements in incineration practices and technologies.

Despite significant decreases in emissions of most pollutants, emissions of 3 of the 17 reported air pollutants have increased since 1990. Some key emission sources contributed to these trends, in particular:

• Particulate matter emissions have risen gradually by 34% for total particulate matter (TPM) and 25% for particulate matter less than 10 microns (PM₁₀) since 1990. These increases are largely from dust emissions associated with transportation on unpaved roads as well as construction operations.
  • Transportation on unpaved roads has increased by approximately 77% in terms of VKT between 1990 and 2023.
  • Capital expenditures on construction, which are used to calculate construction dust emissions and reflect overall construction operations volume, have increased approximately 80% between 1990 and 2023.
• Emissions of NH₃ in 2023 were 25% higher than 1990 levels.
  • Ammonia emissions increased between 1990 and 2000 from 395 kt to 476 kt, then fluctuated between 449 kt and 498 kt.
  • This upward trend is primarily driven by increases in livestock populations in the first half of the time series in combination with continual increases in the use of inorganic nitrogen fertilizer throughout the monitoring period.

Between 2022 and 2023, 9 of the 17 pollutants have shown increases. The most significant ones are HCB (15 %), followed by TPM (5.8%), Cd (4.8 %), PM₁₀ (4.5%) and Hg (4.2%). The PM increases are due to more kilometers travelled, while the other increases are due to variations in the facility-reported data or the activity data used to estimate emissions (refer to Chapter 3 for details on inventory development). Since most of these pollutants are now showing emission levels lower than the historical ones, and emissions totals are often driven mainly by only a few facilities; a small variation in data reported from one facility can be shown as a relatively large year-to-year emission variation in percentages.

When observing long-term emission trends, large-scale events can have a significant impact on a portion of the time series analyzed and should be considered. The years 2020 and 2021 were marked by the COVID-19 pandemic. This coincides with notable observed emission decreases between 2019 and 2020 for almost all pollutants_. Impacts of the pandemic, more pronounced in 2020, are now harder to distinguish in recent years, as most air pollutants have resumed their gradual downward trend of recent decades.

Irrespective of the downward trends observed in Canadian emissions, air quality issues may still arise when emission sources are spatially concentrated.

Emissions for each pollutant by category and sector in 2023 are presented in Table 2–2. The subsequent sections 2.1 to 2.11 of this chapter identify major source contributions to total emissions over the 1990–2023 period. Emission trends analyses for 2005 to 2023 have also been included for PM_2.5, SO_x, NO_x and VOCs in relation to the emission reduction commitments as per the amended Gothenburg Protocol.^{Footnote 2}

The full-time series of national, provincial and territorial air pollutant emissions from 1990 to 2023, including emissions by subsector as well as other emissions estimated in the APEI,^{Footnote 3}  are available online on the Government of Canada Open Data Portal.^{Footnote 4}

Table 2–2: Total Air Pollutant Emissions in 2023 for Canada by Category and Sector

Notes:
Totals may not add up due to rounding.
a. PAH includes B(a)p, B(b)f, B(k)f, I(1,2,3-cd)p.
0.00 Indicates emissions were truncated due to rounding.
NA  Indicates no emissions

Note:
Refer to Annex 4.4 for more information on international marine navigation and air transportation reporting emissions.