Air Quality Index

The Ontario Ministry of the Environment monitors air quality using the Air Quality Index (AQI) system. The AQI is an indicator of air quality based on hourly pollutant measurements of some or all of the six most common air pollutants: sulphur dioxide (SO₂), ozone (O₃), nitrogen dioxide (NO₂), total reduced sulphur compounds, carbon monoxide (CO) and fine particulate matter (PM_2.5). Air quality measurements for the Simcoe Muskoka area originate from two ambient air monitoring stations in Barrie and Dorset.

The AQI generates a number that indicates five categories for air quality: very poor, poor, moderate, good and very good. Very poor air quality (>100) may have adverse effects for a large proportion of those exposed and may cause significant damage to vegetation and property. Poor air quality (55-99) could result in adverse health effects for people with existing health conditions. Moderate air quality (32-49) may result in some adverse effects for people with health problems. Good and very good air quality (<32) results in few adverse health effects.

Ozone and fine particulate matter are the pollutants most often responsible for poor air quality (i.e. when AQI is >49) in the Simcoe Muskoka area. In 2007, results from the Barrie air monitoring station indicated that ozone was responsible for poor air quality for six hours and fine particulate matter (PM2.5) resulted in 14 hours of poor air quality. While at the Dorset station, ozone and fine particulate matter were responsible for poor air quality for 34 hours and two hours respectively. 

Air Quality Index Categories and Associated Health Effects