Module: Air pollution
Which pollutants have fallen, and who emits more than their share?
Air pollutants damage health and ecosystems locally, which makes them a cleaner test of environmental policy than greenhouse gases. Some have fallen dramatically since 1990; one has risen; and the burden is spread unevenly across provinces.
- Sulphur oxides since 1990
- −81%
- Acid-rain controls and coal closures
- Ammonia since 1990
- +28%
- Mostly agriculture
- Alberta’s share of NOx
- 42%
- 12% of the population
- National PM2.5, 2023
- 9.5µg/m³
- Standard 8.8; Prairies 16.1
Four decades of change
Air pollutant emissions, change since 1990
Percentage change from the 1990 level. Pick a pollutant to bring it forward; the others stay for comparison.
Emissions are not exposure
Fine particulate matter by region
Annual average PM2.5 (µg/m³) against the 2020 Canadian Ambient Air Quality Standard. The 2023 spike was wildfire smoke.
In absolute terms
Sulphur and nitrogen oxides, kilotonnes
National totals for selected years. SOx is the main precursor of acid rain.
Exercises
Which pollutant has increased since 1990, and by how much? Which has fallen the most?
Check your reasoning
Ammonia (NH₃) is the only one above its 1990 level, at +28%. Sulphur oxides fell the most, −81%.
Compute each province’s ‘pollution-to-population ratio’ for NOx (emission share ÷ population share). Which three provinces are highest? What industries might explain them?
Show a hint
Use the table view, then divide the NOx column by the population column.
Check your reasoning
Nunavut, the Northwest Territories and Alberta rank highest: Nunavut and the Northwest Territories rely on diesel generation and mining with tiny populations; Alberta hosts oil and gas extraction and processing. A ratio above 1 means more than a per-capita share.
Wildfire smoke raised PM2.5 far above the standard in 2023. Is wildfire smoke an externality? Who could be held responsible, and what policy tools apply?
Check your reasoning
Partly. Natural ignition is not an externality, but climate change (driven by global emissions) raises fire risk, and land management choices affect fuel loads. Responses are mostly adaptation: forecasting, clean-air shelters, filtration, and forest fuel management, because the source cannot be priced directly.
Emission shares are provincial. Why is that too coarse to study environmental justice? Describe how you would use NPRI facility locations and census data to do better.
Check your reasoning
Exposure is local: two neighbourhoods in one province can differ greatly. A better design geocodes NPRI facility releases, buffers them (for example 5 km), joins to census dissemination areas, and compares income, Indigenous identity or visible-minority shares inside versus outside the buffers — the spatial join workflow from Chapter 7 of the course text.