Air Quality Health Index (AQHI)

On June 24, 2015 Ontario’s Ministry of Environment, Conservation and Parks (MECP) introduced the AQHI to replace the previous Air Quality Index (AQI). Clean Air Hamilton and Hamilton Public Health Services were advocates for the development of this health-based Air Quality Index; a well-conceived health index that provides the public with useful information about current air quality conditions and provide the public with strategies they can use to reduce their exposures.

The Government of Canada has developed an Air Quality Health Index (AQHI) and has piloted this index in selected cities across Canada starting in 2008.  Daily AQHI readings for Hamilton are being piloted on Environment Canada’s website. The Government of Canada’s new AQHI is calculated in a different manner compared to the current Air Quality Index (AQI) that is reported by the Ontario Ministry of the Environment, Conservation and Parks.  The MECP’s AQI currently takes into account 6 pollutants: fine particulate matter (PM2.5,) nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), total reduced sulphur (TRS) compounds and ground-level ozone (O3).  The AQI value is calculated based only on one of these six pollutants depending on which pollutant has the highest value on its scale.   During the summer months when levels of ozone tend to be high, the hourly AQI value (which is reported by the MECP) will usually be determined by the concentration of ozone in the air.  In the spring and the fall, the AQI level is driven by levels of PM2.5.

The AQHI pilot was launched in the City of Hamilton in June 2011.  To see the AQHI for Hamilton visit:

The AQHI is calculated using a formula that combines the concentration and the relative health impacts of three pollutants: ground-level ozone (O3), particulate matter (PM2.5/PM10) and nitrogen dioxide (NO2).  According to the Government of Canada, sulphur dioxide (SO2) and carbon monoxide (CO) were removed from the formula as they were not associated with additional health risks once the three pollutants were taken into account. It makes sense to use multiple pollutant contributors in determining health effects impacts. This latter approach has been used in Clean Air Hamilton’s health studies.

Federal, provincial and municipal governments collaborated in order to develop the AQHI as a numeric tool that could be used by health professionals and the public to determine the health risks related to air quality at a given time.

Health messages are directed at two distinct populations – the “at risk” population and the general population. The “at risk” population includes individuals at increased risk due to age or a variety of conditions; these include young children, the elderly, people with existing respiratory conditions (e.g., asthma, chronic obstructive pulmonary disease (COPD), including bronchitis, emphysema and lung cancer) and people with existing cardiovascular conditions (e.g., angina, previous heart attack, congestive heart failure, arrhythmia or irregular heartbeat).  The ‘general population’ includes all other individuals who do not fall under the “at risk” population (Environment Canada, 2010).

Those in the “at risk” category are encouraged to monitor the AQHI more regularly since they are more sensitive to air pollution.  These individuals are encouraged to develop their own self-calibration points on the AQHI scale.  Most people understand how to use temperature, wind chill, UV Index and Humidex values prior to going outdoors and to make decisions based on these parameters.  The AQHI value is another factor that individuals will need to calibrate themselves to in the near future.

For more information on the Air Quality Health Index (AQHI) visit:

Hamilton Public Health Services – Air Quality, Pollution & Smog

Ontario Ministry of the Environment, Conservation and Parks – AQHI Forecasts & Observations

Environment Canada and Climate Change Canada – Air Quality Health Index