Air Quality Health Index (AQHI)

The Air Quality Health Index, or AQHI, is a scale that shows the health risks associated with outdoor air quality. It provides a number and related health risk category to help you understand the potential impacts of air pollution on your health.

Click here for more information from Environment and Climate Change Canada.

In Canada, the AQHI is calculated using three air pollutants: ground-level ozone (O₃), fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂). These pollutants are known to have harmful effects on lung and heart health as well as other health impacts.

The national AQHI calculation is enhanced in Alberta to better account for rapidly changing air quality and to include additional pollutants. In our province, hourly pollutant levels for fine particulate matter, sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide, hydrogen sulphide, and total reduced sulphur are compared against Alberta’s Ambient Air Quality Objectives (AAQOs) (or OHS Guidelines for H₂S/TRS). If it is higher, the AQHI value is replaced with the appropriate high or very high risk value (seven or greater).

Learn more about the AQHI calculation in Alberta here.

AQHI levels are predicated by using data sources, including real-time air quality measurements from monitoring stations, meteorological data, and computer models. These data help predict pollution and weather conditions, allowing the calculation of the AQHI for the upcoming hours or next three days.

Click here to learn more about AQHI forecasting.

Current AQHI values are updated hourly, reflecting the most recent air quality data from monitoring stations. Real-time updates are important during quickly changing air quality conditions or during air pollution events like wildfires.

The AQHI is usually reported as a three-hour average to provide a more complete and real-time picture of current air quality. This approach involves averaging air pollutant concentrations over the past three hours to reflect the recent changes in pollution levels and their potential health impacts. In the event where there is an “exceedance” (one pollutant is measuring at a level above acceptable limits), the AQHI is calculated using the most recent hour of data only, until the exceedance passes.

Sometimes, using this three-hour average means there is a delay for the AQHI to “catch up” to current conditions. For example, if smoke moves in or out of a region it may take several hours for the AQHI value to reflect this change in air quality.

Some communities may have an AQHI value without having local air monitoring stations by using data from nearby monitoring sites in neighbouring cities or regions. These stations provide real-time data on air quality, and communities that do not have their own monitoring stations can use this data to estimate air quality within their boundaries. Local factors such as terrain, land cover, and population are used to define boundaries.Unfortunately, air quality data is not available in all areas of Canada, and by using these forecast regions, we can provide AQHI information to more communities and rural areas.

While this approach can provide valuable insights into air quality, it is not as accurate as data directly collected from local monitoring stations. It is important for communities to recognize the limits of such estimates and, where possible, support Airsheds such as Alberta Capital Airshed in setting up more air monitoring stations. To help get air quality information from areas without air monitoring stations, Alberta Capital Airshed partners with communities and individuals to install low-cost portable sensors that monitor for fine particulate matter.

Refer to our Live Data Map to see all the monitoring we operate in the region.

While the data used to calculate the AQHI comes from ACA’s monitoring network, the AQHI can vary between different websites or mobile apps due to differences in calculations and data processing algorithms, leading to slightly different AQHI values.

For example: AQHI on websites or apps from Environment Canada and Climate Change, Alberta Government, and ACA is calculated using the past three hours of data from continuous monitoring stations measuring fine particulate matter, ozone, and nitrogen dioxide. While AQHI requires the three core pollutants, some websites use the term Air Quality Health Index when reporting on air quality using the single parameter of fine particulate matter, and for alternate averaging times. The data used in these calculations comes from an array of microsensors (including some in use by the ACA).

Despite these variations, the AQHI is a valuable tool to raise awareness about air quality and its potential health impacts and is useful for helping Canadians make decision related to air quality.

AQHI and AQI are similar in their purpose to communicate air quality information. However, they differ in the pollutants included, the numerical scale used, and the health risk categories. AQI in the United States, for example, includes additional pollutants like carbon monoxide (CO) and sulphur dioxide (SO2). It also uses a scale from 0-500, with an AQI <50 indicating good air quality, and 300+ indicating hazardous air quality.

Click here for more information on AQI.

The AQHI only shows outdoor air quality. Indoor air quality can be very different from outdoor conditions due to factors like building ventilation, indoor activities, and pollutant sources. Separate indoor air quality assessments are needed to understand indoor pollution levels.

Real-time AQHI data is available through websites, mobile apps, and in some public places. Here are some places you can find AQHI data:

• ACA displays AQHI in our Airshed on our home page.
• Government of Canada (and the WeatherCAN App) provide AQHI data for many communities across Canada
• Government of Alberta shares the AQHI by station across Alberta

The AQHI health risk categories range from low (1-3) to very high (10+). Each category represents the level of health risk associated with the current air quality. Low risk means that most people can engage in outdoor activities without major health concerns. Very high risk indicates that even healthy individuals may feel unwell from exposure to air quality conditions.

Click here for more information on how to apply AQHI health messages.

By checking the AQHI regularly, you can stay informed about current air quality conditions in your area. If the AQHI indicates higher risk, you may consider reducing outdoor activities, especially if you or your family members belong to sensitive groups like children, older adults, or individuals with pre-existing lung or heart conditions. Following local air quality advisories and taking measures can help protect your health.

Click here for more information on how to use the Air Quality Health Index.

During poor air quality days, certain groups are most at risk, including children, older adults, pregnant women, individuals with pre-existing lung or heart conditions (e.g., asthma, chronic obstructive pulmonary disease – COPD), and those with weakened immune systems. In addition, people participating in sports or strenuous work outdoors breathe more deeply and rapidly, allowing more air pollution to enter their lungs. Vulnerable populations are more likely to feel unwell due to their increased sensitivity to air pollution. These individuals should take extra precautions, such as limiting outdoor activities, staying indoors, and following advice from local health experts during periods of poor air quality.

On days when air pollution levels are high, even healthy people may notice symptoms. It is important to listen to your body and take actions to reduce your exposure to air pollution if you notice symptoms.

Click here to learn about the impact of air pollutants on human health and what you can do to reduce your exposure.

A “Special Air Quality Statement” is an advisory issued by the Government of Alberta and/or Environment and Climate Change Canada to inform the public about specific air quality conditions that may not be adequately represented by the Air Quality Health Index (AQHI). It is typically issued when there are temporary, localized, or unusual air quality concerns, such as elevated levels of a specific pollutant or an event like wildfires or temperature inversions. In order for the AQHI to reflect high-risk conditions, the AQHI air monitoring stations MUST be measuring elevated concentrations. For example, wildfire smoke can be highly localized or moving in and out of an area, and may not be measured by the AQHI station. It may also take several hours for the AQHI value to reflect a change in air quality, due to the way the AQHI is calculated. In this case, a SAQS can provide information to the public on the air quality event.

It’s important to pay attention to Special Air Quality Statements, even if the AQHI indicates a low risk. SAQSs are issued to provide specific guidance based on unique circumstances. Follow any advice or recommendations provided in the statement, which may include reducing outdoor activities, taking precautions, or staying informed about changes in air quality.