How is AQHI Reporting Enhanced in Alberta?

The AQHI value is calculated by using a formula which combines the readings of three specific pollutants – fine particulate matter, ozone and nitrogen dioxide. Because of Alberta's energy based economy, other pollutants monitored in the province are also considered when reporting the AQHI. These pollutants include sulphur dioxide, hydrogen sulphide, total reduced sulphur and carbon monoxide. Additionally, special community-based messaging for odour or visibility is an added feature to the AQHI reported in Alberta.

How has the AQHI value been modified for Alberta?
The national AQHI is based on three-hour average air pollutant concentrations and therefore is not responsive to rapidly changing air quality conditions that occur in Alberta. An example of this situation is when wild fire smoke transported into populated communities changes air quality from “Low” risk to “High” risk in a matter of minutes.

  
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To remedy this issue, the AQHI number presented in Alberta considers hourly comparisons of individual pollutant concentrations to Alberta’s Ambient Air Quality Objectives (AAQOs). If hourly air pollutant concentrations are higher than Alberta’s AAQOs, then the AQHI value is replaced with the appropriate “High” or “Very High” risk value. This adjustment is relevant for particulate matter, ozone, nitrogen dioxide, sulphur dioxide and carbon monoxide. In addition, Alberta’s AQHI includes special community-based messaging when pollutant concentrations exceed specific thresholds for odour and visibility.

If the following pollutant thresholds are exceeded when the AQHI is “Low” or “Moderate” risk (6 or less), then the AQHI is replaced with the appropriate “High” or “Very High” risk value (7 or greater):

  • 80 micrograms per cubic metre for fine particulate matter
  • 82 parts per billion for ozone
  • 159 parts per billion for nitrogen dioxide
  • 172 parts per billion for sulphur dioxide
  • 13 parts per million for carbon monoxide
  • 1 part per million for hydrogen sulphide and total reduce sulphur

What messaging is provided for odour and visibility?
Alberta’s AQHI includes special messaging when odour or visibility events are occurring in a community. Special community level messaging is provided in cases when concentrations of specific pollutants are higher than specified odour or visibility thresholds and the AQHI is rated as “Low” or “Moderate” risk. In these cases, you may detect an odour or visibly notice air pollution however levels are low enough not to cause a health issue for the general population. This messaging will be used for particulate matter, sulphur dioxide, hydrogen sulphide and total reduced sulphur. An example of this special messaging is indicated below.

While you may detect an odour or change in visibility or clarity, enjoy your outdoor activities unless you experience symptoms.

The following air pollutant thresholds will be used for the special messaging mentioned above:

  • 25 micrograms per cubic metre for fine particulate matter (based on visibility)
  • 100 parts per billion for sulphur dioxide (based on odour)
  • 10 parts per billion for hydrogen sulphide or total reduced sulphur (based on odour)