Map of Simcoe Muskoka


Ozone and Fine Particulate Matter

The key contributors to smog and poor air quality in Simcoe Muskoka are ozone (O3) and fine particulate matter (PM2.5).


Ground-level ozone is formed when pollutants from vehicle exhaust emissions react in sunlight. Ozone can accumulate in suburban and rural areas (like Simcoe Muskoka) because the pollutants originating from urban areas react in the sunlight during the time taken to travel out of the cities. Ozone irritates the respiratory tract and eyes. Exposure to ozone in sensitive people can result in chest tightness, coughing and wheezing. Children who are active outdoors during the summer, when ozone levels are highest, are particularly at risk. Individuals with pre‐existing respiratory disorders, such as asthma and chronic obstructive pulmonary disease (COPD), are also at risk.

According to the 2015 Air Quality Report in Ontario, overall provincial ozone annual means have increased by three per cent from 2005 to 2015; however, ozone summer means have decreased by four per cent over the same period.

In Barrie, between 2003 and 2016, the ozone summer mean concentrations have remained relatively stable; whereas, the winter mean ozone concentrations have increased by an average of 0.9% (0.2%, 1.5%) per year which was statistically significant. In Dorset during the same time period, summer ozone concentrations have decreased by 1.9% (0.9%, 2.6%) per year, which was statistically significant; however, winter ozone concentrations in Dorset have remained unchanged over this fourteen-year time period.



Throughout the year, levels of ozone in Simcoe Muskoka occasionally exceed Ontario’s air quality criteria. These exceedances vary from year to year. There have not been any ozone exceedances observed at either the Barrie or Dorset stations since 2012. In 2012, the ozone levels recorded at the Barrie air monitoring station exceeded the Ontario criteria of 80 parts-per-billion (ppb) on six separate days for a total of 16 hours. While in Dorset in 2012, only two hours (both on separate days) exceeded the Ontario criteria for ozone.


Fine Particulate Matter (PM2.5)

Fine particulate matter (PM2.5) exceedances occur when the daily average readings are greater than the Ontario criteria (30 μg/m3). PM2.5 exceedances have been rare at both the Barrie and Dorset air monitoring stations over the past eight years, with just two occurrences in Barrie since 2007 (one in 2009 and one in 2015). Between 2003 and 2007, there were an average of 6 PM2.5 exceedances in Barrie and 3 in Dorset each year.