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By Annika Segelhorst and Elmira Aliakbari
Take a deep breath and savour the freshness of spring without fear. Canada’s air quality significantly improved over the past half century.
Levels of major air pollutants have fallen dramatically since the 1970s, and today, most communities in Canada enjoy good air quality for the vast majority of each year. Earth Day is a great time to track and celebrate the impressive strides we’ve made towards achieving better air quality.
Yet despite this measured reality, recent public perception of air quality has trended sharply negative. According to a 2023 Abacus poll, 68 per cent of Canadians are worried about outdoor air quality, an 18 point increase from 2021, even though we have long-term evidence that air quality is generally improving. Some of these recent perceptions likely stem from the 2023 and 2025 wildfire seasons. These short-lived but severe events have become part of the public’s collective memory, shaping how air quality is perceived in Canada. But trends in major air pollutants over multiple decades show a more encouraging story.
Consider ground-level ozone—a pollutant that forms when vehicle exhaust and industrial emissions react in sunlight. Ozone levels were nearly 27 per cent lower in 2023 than in 1976, and national average levels have consistently been below Canada’s strictest air quality standards since 2008.
Average outdoor levels of other pollutants have also sharply declined. Nitrogen dioxide, an air pollutant that forms when fuel is burned, is down 80 per cent since 1976. And since 2004, levels of nitrogen dioxide have consistently remained below the most stringent national air-quality guideline.
Sulphur dioxide, produced by burning sulphur-containing fuels and metal ore, is another tremendous success story. Sulphur dioxide levels are down 94 per cent since 1976 and have remained consistently below the air quality standard since 2001. Similarly, carbon monoxide, a toxic air pollutant released by burning fuel, is down 88 per cent since 1974.
Even fine particle pollution, the main culprit of poor air quality during major wildfires, has a better track record than many might expect. Since the early 2000s, when consistent national measurements became available, annual average measurements of fine particle pollution have been stable and have generally remained below national air-quality guideline levels.
The Air Quality Health Index (AQHI) offers another way to evaluate trends in air quality. Developed by Health Canada, the AQHI combines measurements of three pollutants (nitrogen dioxide, sulphur dioxide and fine particle pollution) into a single score reflecting overall health risk. Some may be familiar with AQHI’s 1-10+ scale, as daily forecasts are often reported alongside weather forecasts.
Since 2000, the portion of days across Canada that had daily scores in the “low-risk” category, meaning air quality is ideal for outdoor activities for most people, increased from 69.9 per cent to 85.5 per cent of days in 2023. Averaged across all Canadian communities, the highest daily AQHI score, representing the worst air quality during a 24-hour period, fell by 9.6 per cent.
Of course, some challenges remain, both natural and manmade. Periodic smoke from wildfires continues to pose risks for many Canadians, especially people with underlying respiratory conditions. Certain communities located near industrial hubs still contend with higher-than-ideal levels of air pollutants. Yet overall, Canada has achieved dramatic improvements in air quality compared to national health guidelines and performs well compared to other countries—a study from last year found that Canada ranked 8th best for air quality among 31 high-income countries.
The strides that Canada has taken towards cleaner air over the past half-century represent one of the most important environmental success stories in Canada’s history. Behind every data point is a person who is breathing more easily, a child with asthma playing outside, a city-dweller enjoying a smog-free vista, an elderly couple enjoying a neighbourhood walk with fresh air. On Earth Day, it’s worth stepping back and recognizing Canada’s progress towards cleaner air, an accomplishment experienced by millions of Canadians. So breathe easy and enjoy the warmer days ahead.
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