Canada’s Air Pollutant Emissions Inventory Report 2022: 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 2020, 60 t of PAHs were emitted in Canada (Table 2–13), with 84% (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 83% (50 t) of total 2020 emissions. Transportation and Mobile Equipment was the next largest source, contributing 12% (7.3 t) of PAH emissions in 2020.

From 1990 to 2020, PAH emissions decreased by 80% (234 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 2020. 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 1990-2020 time series, with a decrease in emissions of 29% (20 t) owing to a 28% reduction in wood consumption and the adoption of more efficient wood combustion equipment. Between the years 2019 and 2020, Home Firewood Burning experienced a PAH emission decrease of 8.4% (4.6 t) attributed to reduced wood consumption. PAH emissions from Transportation and Mobile Equipment have decreased across the time series owing to increasingly stringent engine and vehicle regulations.^{Footnote 8}

The most significant changes in PAH emissions from 1990 to 2020 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 29% (20 t)
  • Home Firewood Burning: decrease of 29% (20 t)
• Transportation and Mobile Equipment: decrease of 70% (17 t), with:
  • Light-Duty Gasoline Trucks and Vehicles: decrease of 69% (11 t)

Figure 2–11: Trends in Canadian polycyclic aromatic hydrocarbons emissions (1990 to 2020)

Table 2–13: National summary of annual polycyclic aromatic hydrocarbons emissions

Notes:
Totals may not add up due to rounding.
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.