Air Quality in Ontario 2018 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 11%, nitrogen dioxide concentrations by 21%, and sulphur dioxide concentrations by 59% on average across the province (see table below).
• In 2018, Ontario reported air quality in the low risk category 92.9% 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 continues to decrease indicating reduced emissions in Ontario and the United States.
• In 2018, 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 at some locations.
• 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.