Air Quality in Ontario 2019 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, fine particulate matter concentrations have decreased by 20%, nitrogen dioxide concentrations by 22%, and sulphur dioxide concentrations by 63% on average across the province (see table below).
• In 2019, Ontario reported air quality in the low risk category 94.5% of the time, based on the Air Quality Health Index (AQHI).
• Ozone and fine particulate matter, the main components of smog, remain as pollutants of concern, however the maximum measured concentrations of ozone continue to decrease indicating reduced emissions in Ontario and the United States.
• In 2019, there were exceedances of the provincial Ambient Air Quality Criteria and/or Canadian Ambient Air Quality Standard for ground-level ozone, fine particulate matter, sulphur dioxide and benzene in some communities.
• Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as forest fires, and the long-range transport of air pollutants from the United States and elsewhere.