The Air Quality Health Index (AQHI)

The AQHI was developed and implemented by Health Canada with the assistance of Environment and Climate Change Canada and all provinces. It derives a value based on the cumulative health effects of three pollutants – NO2, PM2.5 and ozone. The AQHI provides real-time air quality information using a scale of one through 10 or greater, with lower numbers representing better air quality, as depicted in Figure 22. Index values between one and three are considered low risk, four to six are moderate risk, seven to 10 are high risk and greater than 10 are very high risk. Table 2 outlines the health messages associated with the AQHI. The Ministry’s air quality website provides index values and corresponding categories and health messages.

Figure 22: AQHI Scale

Quality Health Index scale which ranges from one to 10 plus.

Source: Environment and Climate Change Canada.

 

 

Table 2: Air Quality Health Index categories and health messages

 

 

Health riskAir Quality Health IndexHealth messages - At risk population footnote 1Health messages - General population
Low1-3Enjoy your usual outdoor activities.Ideal air quality for outdoor activities.
Moderate4-6Consider reducing or rescheduling strenuous activities outdoors if you are experiencing symptoms.No need to modify your usual activities unless you experience symptoms such as coughing and throat irritation.
High7-10Reduce or reschedule strenuous activities outdoors. Children and the elderly should also take it easy.Consider reducing or rescheduling strenuous activities outdoors if you experience symptoms such as coughing and throat irritation.
Very highAbove 10Avoid strenuous activities outdoors. Children and the elderly should also avoid outdoor physical exertion.Reduce or reschedule strenuous activities outdoors, especially if you experience symptoms such as coughing and throat irritation.

Source: Environment and Climate Change Canada

The AQHI also takes into account exceedances of Ontario’s AAQC for common air pollutants: 200 ppb for NO2, 80 ppb for ozone, 250 ppb for SO2, 30 ppm for CO, and 27 ppb for TRS compounds. If an hourly air pollutant concentration exceeds Ontario’s AAQC, then the AQHI is reported with the appropriate high risk value (AQHI of 7 or greater) to reflect the exceedance.

Based on the AQHI categories, in 2017, Ontario reported low risk air quality 94.6% of the time, moderate risk 5.4% of the time, and high risk 0.01% of the time. No very high risk hours were reported. Table A20 of the Appendix provides the percentage distribution of hourly AQHI readings for each of the 39 monitoring sites by AQHI value and the number of high risk AQHI days.

Access to air quality information

Near real-time and historic pollutant concentration data and AQHI values are available to the public (24 hours per day, 7 days a week) from across the province on the Ministry’s air quality web site. The public can also access AQHI values via an Interactive Voice Response (IVR) system (to access a recording, call 1-800-387-7768, or in Toronto, call 416-246-0411). The Ministry’s web site also provides air quality forecasts throughout the day, based on regional meteorological conditions and current pollution levels in Ontario and bordering American states.

Air quality alerts

Ontario maintains a two-level air quality alert system in partnership with Environment and Climate Change Canada.

The first level is a Special Air Quality Statement (SAQS), which informs the public of the potential for degrading air quality and is issued if an AQHI of 7 or greater is expected to last for 1 or 2 hours (short-term, transient event). A SAQS is also issued for areas where forest fire smoke is expected to cause deteriorating air quality. The SAQS serves as a notification for Ontarians, especially those at risk, at the potential for degrading air quality and to adjust their activities if adverse health effects are observed.

The second level is a Smog and Air Health Advisory (SAHA), which informs the public of the potential for degrading air quality and is issued if an AQHI of 7 or greater is expected to be persistent and continue for 3 hours or more.

Air quality alerts are issued via the Ministry of the Environment, Conservation and Parks’ air quality web site, Environment and Climate Change Canada’s web site, and through email air quality alert notifications. To subscribe for air quality alert notifications, please visit the Ministry web site.

Ontario did not issue a SAHA in 2017, however, there were seven SAQS issued for regions across the province. Three SAQS were issued for parts of northwestern Ontario due to forest fire smoke originating from Manitoba and/or Saskatchewan. Three SAQS were issued as a result of elevated ozone concentrations in southern Ontario, and the remaining SAQS was issued for the City of Hamilton due to the cumulative effects of ozone, PM2.5 and NO2. Table A21 of the Appendix summarizes the number of air quality alerts issued for Ontario in 2017.


Footnotes

  • footnote[1] Back to paragraph People with heart or breathing problems are at greater risk. Follow your doctor’s usual advice about exercising and managing your condition.