Air Quality in Ontario 2022 Report

Air quality highlights

• Overall, air quality in Ontario has improved over time as both ambient concentrations of common air pollutants and emissions to air have decreased. Over the last 10 years, concentrations have decreased by 28% for nitrogen dioxide, by 18% for fine particulate matter concentrations, and by 48% for sulphur dioxide concentrations on average across the province (see table below).
• In 2022, Ontario reported air quality in the low-risk category 94% of the time, based on the Air Quality Health Index (AQHI).
• Transboundary influences, from both the U.S. and beyond, account for a significant portion of Ontario’s ozone when its levels are elevated.
• Ozone and fine particulate matter, the main components of smog, remain as pollutants of concern from a regional perspective. Sulphur dioxide and benzene remain a concern at the local level in some communities.
• In 2022, there were exceedances of the provincial Ambient Air Quality Criteria and/or Canadian Ambient Air Quality Standard for ground-level ozone, fine particulate matter and sulphur dioxide in some communities.
• Decreasing trends were observed for some traffic-related pollutants including black carbon and sulphate in fine particulate matter, while others showed no trend.
• Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as wildfires, and the long-range transport of air pollutants from the United States and elsewhere. Long-term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.