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By Annika Segelhorst and Elmira Aliakbari
Canada’s Air Quality, 1970-2023
- This study analyzes data from Environment Canada on emissions and ambient (outdoor) concentrations of five major air pollutants critical to human health: ground-level ozone (O3), nitrogen dioxide (NO2), fine particulate matter (PM2.5), sulphur dioxide (SO2), and carbon monoxide (CO).
- Trends for these pollutants are evaluated against existing national clean-air objectives. The study also analyzes sectoral contributions to air pollutant emissions and uses the Canadian Air Quality Health Index (AQHI) to evaluate cumulative air-quality trends since 2000.
- The data suggest that air quality in Canada has improved over the past five decades, with significant decreases in the ambient concentration of ground-level ozone, nitrogen dioxide, sulphur dioxide, and carbon monoxide.
- In 2023, the concentration of ground-level ozone was nearly 27% lower than in 1976, and ozone concentrations have consistently remained below the strictest air quality standards since 2008. Compared with 1976, sulphur-dioxide concentrations were 94% lower in 2023 and nitrogen-dioxide concentrations were 80% lower. Similarly, ambient concentrations of carbon monoxide fell by 88% between 1974 and 2023.
- Statistical analysis shows that national average ambient concentrations of fine particulate matter have had no detectable national trend since 2000 but have generally remained below national health guideline levels.
- The analysis of AQHI shows that baseline air quality improved between 2000 and 2023. The average of daily maximum AQHI values declined steadily and Canadians experienced more days where air quality was in the low-risk category. Despite this general improvement, episodes of poor air quality continued to occur, varying in frequency and severity from year to year.
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