Archived: Air Pollutant Emission Inventory report: chapter 2.11

2.11 Polycyclic Aromatic Hydrocarbons (PAHs)

The APEI reports emissions of four 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(1,2,3-cd)p). The analysis presented here is based on the aggregate total of all four substances. In 2015, 110 t of PAHs were emitted in Canada (Table 2-13), with 95% (104 t) attributed to commercial/residential/institutional sources. This is almost entirely due to home firewood burning, which contributed 92% (102 t) of total PAH emissions. The ore and mineral industries contributed almost all the remaining 5% (6 t) of PAH emissions in 2015, notably the aluminium industry with just over 4% (5 t).

From 1990 to 2015, emissions of PAHs decreased by 67% (226 t) (Figure 2-11). This trend is primarily due to emission reductions in the aluminium industry and iron and steel industries. The aluminium industry experienced a large drop in PAH emissions from 2001 to 2010 due to the implementation of new production technologies, such as the introduction of pre-baked electrodes to replace continuous casting electrodes. It experienced additional decreases between 2014 and 2015, related to the replacement of old smelting equipment with a modern smelter at the facility which historically contributed the largest share of PAH emissions.

PAH emissions from iron and steel industries experienced a large drop earlier in the time series, from 1993 to 2006, and remained quite small and constant from 2006 to 2015. Reductions in this sector are a result of effective emission controls on coke ovens and electric arc furnaces.

Home firewood burning dominates PAH emissions throughout the trend. However, this source experienced a more modest 25% (35 t) emission decrease from 1990 to 2015. This can be attributed to a reduction in the use of wood as heating fuel and to the increased use of newer technologies in fireplace inserts, furnaces and stoves that limit the emission of both wood smoke and, as a result, PAHs by improving combustion efficiency.

The most significant changes in PAH emissions from 1990 to 2015 include:

• Ore and mineral industries source emissions: decrease of 97% (184 t)
  • Aluminium industry: decrease of 96% (104 t)
  • Iron and steel industries: decrease of  99% (79 t)
• Commercial/residential/institutional emissions: decrease of 28% (42 t)
  • Home firewood burning: decrease of 25% (35 t)

Notes:

Totals may not add up due to rounding.

- denotes no emissions.