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Ozone and Fine Particulate Matter

The key contributors to smog and poor air quality in Simcoe Muskoka are ozone (O₃) and fine particulate matter (PM_2.5). Ground-level ozone is formed when pollutants from vehicle exhaust emissions react in sunlight.

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.

The average increase in ozone levels is also greater for rural than urban sites in Ontario. Levels of ozone in Dorset, near Algonquin Park, tend to be higher than levels in downtown Toronto because cities emit pollutants that then react in the sunlight during the time taken to travel to cottage country.

Throughout the year, levels of ozone and fine particulate matter in Simcoe Muskoka often exceed Ontario’s air quality criteria. These exceedances vary from year to year. In 2007, the ozone levels recorded at the Barrie air monitoring station exceeded the Ontario criteria seven times while the Dorset monitoring station recorded 34 ozone exceedances.

Fine particulate matter readings at the Barrie and Dorset air monitoring stations exceeded Ontario's criteria 7 and 2 times respectively.