Air quality is important for human and environmental health. Natural events such as forest fires, as well as factors such as vehicle pollution, industry and urbanization can all affect air quality. Air quality also varies with the seasons.

Air pollutants have short-term and long-term effects. They can make it difficult to breathe, irritate airways and lungs and worsen chronic and pre-existing heart and lung conditions.

In Canada, provincial and federal governments use a variety of tools to monitor, regulate and maintain our air quality. The Air Quality Health Index (AQHI) and the Canadian Ambient Air Quality Standards (CAAQS) are two of the tools used to assess air quality in Alberta.

The AQHI converts hourly measurements of fine particulate matter, ozone and nitrogen dioxide in the air to a number from 1 to 10, with a higher number indicating a greater health risk. The AQHI informs the public about current or predicted air quality conditions so they can make decisions regarding their activities in the event of changes to air quality. The AQHI is designed as a communication tool, and is not used by environmental managers to monitor and measure long-term trends in air quality or to assign management actions.

On the other hand, the CAAQS assessment calculates metrics for a three-year period and excludes exceptional events that cannot be directly controlled by management actions, such as smoke from forest fires. The CAAQS are used to manage pollutant levels based on their potential risk to human health and the environment. There are currently CAAQS metrics for ozone and particulate matter and CAAQS metrics for nitrogen dioxide and sulphur dioxide are under development. Environmental managers use the CAAQS to manage air quality as it is affected by factors such as industrialization and urbanization.

In September 2015, the Government of Alberta reported on the findings of the 2011 to 2013 CAAQS assessment. The assessment found that, for the period from 2011 to 2013, within the Red Deer Air Zone, ambient air quality standards for particulate matter were exceeded. During the same 2011 to 2013 period, AQHI measurements in Red Deer were only ever “high risk” for 0.1% of the time, “moderate risk” for 13.2% of the time and “low risk” for 86.7% of the time.

Therefore, at a first glance, the CAAQS and AQHI metrics appear to disagree about the severity of air quality issues in Red Deer. It is tempting to draw broad conclusions about the effectiveness of these metrics. Is the AQHI telling us that air quality is fine after all and that the CAAQS assessment is flawed? Or is the AQHI failing the residents in Red Deer by missing days with poor air quality?

The answer to both of these questions is “no.” The CAAQS and the AQHI cannot be compared directly because they are very different metrics with very different intended uses.

The CAAQS assessment is used to determine where in the province pollutant levels must be managed. The CAAQS do not indicate whether health or environmental effects have occurred, but act to give regulators a heads up so that preventative management actions can be taken before effects are measured. The exceedance of the CAAQS in Red Deer shows that the levels of particulate matter could potentially have a long-term negative effect on human health and the environment, and that the Government of Alberta and stakeholders must undertake management actions to improve air quality in the area. In order to address this, Alberta Environment and Parks is leading a scientific investigation and management response to address particulate matter in the Red Deer area.

The AQHI, on the other hand, is a communication tool used to inform the public about current and forecasted air quality only. In Red Deer, the AQHI indicates that on an hourly basis the cumulative impact of particulate matter, ozone and nitrogen dioxide should not pose an immediate health risk to the general population. The AQHI does not measure long-term effects of air quality on health and is meant for individuals to use to day-by-day to plan outdoor activity based on their own symptoms. AQHI measurements in the “moderate risk” category 13% of the time in Red Deer could mean that at-risk or sensitive individuals take should precautions to safeguard their health.

Therefore, although at first glance they appear to “disagree,” the CAAQS and the AQHI metrics both served their intended purposes in Red Deer between 2011 and 2013.