Canada’s Air Pollutant Emissions Inventory Report 2025: annex 3

Recalculations

Emission recalculation is an essential practice in the maintenance of up-to-date and consistent trends in air pollutant emissions. The Air Pollutant Emissions Inventory (APEI) is continuously updated with improved estimation methodologies, activity data and more recent and appropriate emission factors. As new information and data become available, previous estimates are updated and recalculated to ensure a consistent and comparable trend in emissions. Circumstances that warrant a change or refinement of data and/or methods include the:

• incorporation of updates to activity data including changes to data sources;
• refinements of methodologies and emission factors;
• reallocation of sources to different categories (which affects subtotals);
• inclusion of categories previously not estimated (which improves inventory completeness); and
• correction of errors detected by quality control procedures.

Resubmissions of facility-reported data previously reported to the National Pollutant Release Inventory (NPRI) can also result in revised historical estimates. Generally, these recalculations by facilities are completed for only a few years in their historical emissions.

In contrast, new activity data are incorporated into the in-house estimates as they become available, and these updates are reflected in the trends on an ongoing basis. Table 3–1 in Chapter 3 shows which sources are estimated using facility reported data and/or in-house methods. Updated trends, based on updated facility-reported data and in-house estimates, are published on a yearly basis. For example, the calculation of emissions from commercial, residential, agricultural and construction fuel combustion sources rely on the latest fuel use quantities from the Statistics Canada annual publication Report on Energy Supply and Demand in Canada (RESD) (Statistics Canada, n.d.).

A3.1 Recalculations in this Air Pollutant Emissions Inventory Edition

The following pollutants were not significantly recalculated (net emissions change <2%) between the 2024 and 2025 editions of the APEI with negligible impacts on the time series trend lines:

• particulate matter less than or equal to 2.5 microns in diameter (PM_2.5)
• sulphur oxides (SO_x)
• carbon monoxide (CO)
• ammonia (NH₃)
• lead (Pb)
• cadmium (Cd)
• mercury (Hg)
• hexachlorobenzene (HCB)

The following pollutants had notable recalculations between the 2024 and 2025 editions of the APEI (in order of recalculation importance):

• polycyclic aromatic hydrocarbons (PAHs), comprised by the sum of the following pollutants:
  • benzo(a)pyrene (B(a)p)
  • benzo(b)fluoranthene (B(b)f)
  • benzo(k)fluoranthene (B(k)f)
  • indeno(1,2,3-cd)pyrene (I(-cd)p)
• nitrogen oxides (NO_x)
• dioxins and furans (D/F)
• particulate matter less than or equal to 10 microns in diameter (PM₁₀)
• total particulate matter (TPM)
• volatile organic compound (VOCs)

These recalculations are presented in Figure A3–1 to Figure A3–6, all at the national level.

Recalculations to PAHs emissions (Figure A3–1) are primarily attributed to incorporating a new emission factor from a Canadian residential wood combustion study. This study better reflects significant advancements made in stove designs and control strategies over the last several years, as well as Canadian practices in firewood burning. The new study is available online on the Government of Canada Open Data Portal^{Footnote 1} .

Figure A3–1 Recalculations to Polycyclic Aromatic Hydrocarbons (PAHs)

Recalculations to NO_x and dioxins and furans emissions (Figure A3–2 and Figure A3–3 respectively) are mainly attributed to new data received to determine emissions from the Domestic Marine Navigation, Fishing and Military sector. Dioxins and furans emissions recalculations are also attributed to changes in activity data used to calculate landfill emissions. Specifically, a reduction in the amount of landfill gas flared resulted in a decrease in dioxins and furans emissions from landfills.

Figure A3–2 Recalculations to Nitrogen Oxides (NO_x)

Figure A3–3 Recalculations to Dioxins and Furans

Recalculations to PM₁₀ and TPM emissions (Figure A3–4 and Figure A3–5 respectively) are largely attributed to changes in the Dust category. The main contributor for this category being the change in activity data (traffic counts) used as input to the road dust model. Another contributor is the incorporation of a new emission factor from a Canadian study to calculate emissions from the residential wood combustion sector (see PAHs recalculations section for more details).

Figure A3–4 Recalculations to Particulate Matter less than or equal to 10 Microns in Diameter (PM₁₀)

Figure A3–5 Recalculations to Total Particulate Matter (TPM)

Recalculations to VOCs (Figure A3–6) are primarily attributed to incorporating a new emission factor from a Canadian study to calculate emissions from the residential wood combustion sector (see PAHs recalculations section for more details) as well as the refinement of the activity data used to determine the contribution of general solvent use.

Figure A3–6 Recalculations to Volatile Organic Compounds (VOCs)

Refer to Annex 2 and Canada’s Air Pollutant Emissions Inventory Methodology Document available on the Government of Canada Open Data Portal^{Footnote 2}  for additional information on methodologies.

A3.2 Considerations for Future Editions of this Inventory

Further refinements and recalculations to the emission estimates are anticipated for subsequent editions of the APEI. An example of a suggested planned improvement is the refinement of the road Dust traffic-distribution model to include a variable (evolving) road network and, provincial and territorial specific total kilometers driven. This improvement is anticipated resulting in significant downward revisions to unpaved road dust particulate matter emission estimates by approximately 70% for the 2026 APEI.

Please contact apei-iepa@ec.gc.ca for more information on any methodological update or recalculations.

References

Statistics Canada. No date. Report on energy supply and demand in Canada (Annual), Catalogue No. 57 003 X.