Canada’s Air Pollutant Emissions Inventory Report 2024: chapter 2.11

2.11 Polycyclic Aromatic Hydrocarbons

The APEI reports emissions of four polycyclic aromatic hydrocarbons (PAHs): benzo(a)pyrene (B(a)p), benzo(b)fluoranthene (B(b)f), benzo(k)fluoranthene (B(k)f) and indeno(1,2,3-cd)pyrene (I(cd)p). The analysis presented here is based on the aggregate total of all four substances. In 2022, 55 t of PAHs were emitted in Canada (Table 2–13), with 92% (50 t) attributed to Commercial/Residential/Institutional sources. This is almost entirely due to Home Firewood Burning, this sector being the largest contributor to PAH emissions since 2004, with 92% (50 t) of 2022 total emissions. Transportation and Mobile Equipment was the next largest source, contributing 3.9% (2.2 t) of PAH emissions in 2022.

From 1990 to 2022, PAH emissions decreased by 81% (227 t) (Figure 2–11), primarily owing to emission reductions in the Aluminium Industry and Iron and Steel Industry sectors of almost 100% each (109 t and 79 t, respectively). Emissions from Aluminium Industry experienced a large drop in PAH emissions from 2008 to 2016 owing to process improvements and the progressive phase-out of old Söderberg aluminium production technologies (ECCC, 2014). Emissions of these four types of PAHs from Iron and Steel Industry dropped significantly earlier in the time series, from 1993 to 2006, and emissions remained small through 2022. Reductions here are a result of effective emission controls on coke ovens and coke by-product plants (EC, 2001).

Within Commercial/Residential/Institutional sources, Home Firewood Burning contributed to the downward trend across the 1990-2022 time-series. Emissions increased from 1990 to 1997, fluctuated until 2014 and have since then constantly decreased, resulting in an overall decrease in emissions of 28% (20 t). This decrease is owed to a 32% reduction in wood consumption and the adoption of more efficient wood combustion equipment. PAH emissions from Transportation and Mobile Equipment have decreased across the time series owing to increasingly stringent engine and vehicle regulations.^{Footnote 10}

The most significant changes in PAH emissions from 1990 to 2022 include:

• Ore and Mineral Industries: decrease of almost 100% (188 t), with:
  • Aluminium Industry: decrease of almost 100% (109 t)
  • Iron and Steel Industry: decrease of almost 100% (79 t)
• Commercial/Residential/Institutional sources: decrease of 28% (20 t)
  • Home Firewood Burning: decrease of 28% (20 t)
• Transportation and Mobile Equipment: decrease of 82% (10 t), with:
  • Light-Duty Gasoline Trucks and Vehicles: decrease of 83% (7.0 t)

 Figure 2–11: Trends in Canadian Polycyclic Aromatic Hydrocarbons Emissions (1990 to 2022)

Notes:
Totals may not add up due to rounding.
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.
—   Indicates no emissions

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