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About the indicator
Ground-level ozone, or O3, is an air pollutant that can negatively affect human health and the environment. O3 is not emitted directly into the atmosphere by humans, but forms through chemical reactions with precursor gases in the presence of heat and sunlight. Precursor gases, such as nitrogen dioxide (NO2) and volatile organic compounds (VOCs), are emitted by human activities in urban and industrial centres and by natural sources such as wildfires. Vegetation is another major source of natural VOCs.
This indicator reports on the concentration of O3 from 2000 to 2022 and provides information on the variation across Alberta and how concentrations have changed over time. This indicator also compares O3 concentrations with Alberta's Ambient Air Quality Objectives (AAAQOs), which set thresholds for air pollutants to protect human and ecosystem health.
Ozone facts
- O3 is found both in the lower and upper atmosphere of the Earth. In the lower atmosphere and at ground-level, exposure to O3 is harmful to humans as it irritates the respiratory system. In the upper atmosphere, O3 occurs naturally and protects the Earth from the sun’s harmful ultraviolet radiation.
- Higher levels of O3 can be transported to the ground from the ozone-rich upper atmosphere under certain weather conditions.
- O3 is a major component of smog which is a mixture of gases and particles emitted into the air by human activities. Smog negatively affects human health and forms haze which reduces visibility.
- O3 is part of the Air Quality Health Index (AQHI) that reports on health risks associated with local air quality across Alberta in real-time.
Methods
For information on how the results in this indicator were calculated and for references, see: Condition of the Environment Report – Air Component
Summary of key results
Last updated: August 2024
- Over the past 2 decades, O3 concentrations have remained steady and no statistically significant trend was observed provincially and in large population centres.
- O3 concentrations in Alberta are strongly influenced by natural atmospheric fluctuations with high levels of background O3 in the spring. These natural fluctuations are driven by several factors, such as seasonal patterns in meteorology and long-range transport of ozone precursor gases.
- Human activities also contribute to elevated concentrations of O3, particularly during summer smog episodes.
Variation across Alberta
- Peak O3 concentrations vary across the province (Figure 1).
- Elevated O3 concentrations can be observed near major population centres due to summer smog episodes and in areas of the province affected by wildfire smoke.
- Elevated O3 concentrations are common in regions such as the foothills that are at higher elevations and have increased forest cover (which results in higher natural VOC emissions).
- Many factors influence the variation in O3 concentration across Alberta, including meteorological conditions that influence O3 formation and transport (for example, solar radiation and wind speed), concentration of O3 precursors (VOCs, NO2), among others.
Figure 1. Peak O3 concentrations across Alberta for 2022
Select a circle on the map to view the 2022 concentration for a specific monitoring station. Peak concentrations are calculated as the annual 4th highest daily maximum of rolling 8-hour concentrations.
Source: Government of Alberta
Changes over time
- From 2000 to 2022, no significant trend over time was observed for annual peak concentrations of O3 averaged across all long-term air monitoring stations in Alberta or for Alberta’s major population centres (Figure 2).
- Variability between years is driven by varying background levels of O3 that occur naturally, as well as the extent of summer smog episodes and wildfire smoke events.
- In 2016, high O3 concentrations in Fort McMurray were caused by smoke from the Horse River wildfire that entered the community and had major impacts on air quality.
Figure 2. Trends in annual peak O3 concentrations from 2000 to 2022 at large population centres
Chart data table
| Year | Provincial Average | 10th Percentile | 90th Percentile | Calgary | Edmonton | Fort McMurray | Grande Prairie | Lethbridge | Medicine Hat | Red Deer |
|---|---|---|---|---|---|---|---|---|---|---|
| 2000 | 58.1 | 46.8 | 66.2 | 54.2 | 57.3 | 48.5 | 59.4 | |||
| 2001 | 58.9 | 49.5 | 66.5 | 54.6 | 57.5 | 51.7 | 57.9 | |||
| 2002 | 62 | 51.9 | 69.5 | 58.3 | 67.1 | 54.8 | 67 | |||
| 2003 | 60.7 | 53.1 | 67.9 | 56.3 | 60.4 | 54.7 | 63.9 | |||
| 2004 | 56.2 | 48.8 | 61.1 | 53 | 56.2 | 49.1 | 56.4 | 59.5 | 61.3 | 55.3 |
| 2005 | 54.5 | 50.2 | 60.9 | 48.6 | 50.9 | 52.9 | 51.3 | 57.1 | 53.6 | 55.4 |
| 2006 | 60.1 | 53 | 67.1 | 54.2 | 57.6 | 56.5 | 53 | 62.6 | 60.9 | 60.3 |
| 2007 | 58.9 | 52.2 | 65.1 | 55.5 | 60.2 | 52.7 | 51.5 | 60.4 | 64.1 | 61.8 |
| 2008 | 60.1 | 54.1 | 66.7 | 53.7 | 58.5 | 52 | 59.5 | 55.9 | 57.1 | 59.5 |
| 2009 | 59.4 | 52.4 | 64.9 | 58.1 | 58.7 | 51.2 | 55.5 | 58.1 | 60.4 | 58.3 |
| 2010 | 58.7 | 52.3 | 64.7 | 53.8 | 57.6 | 57 | 54 | 54.9 | 56.9 | 52.6 |
| 2011 | 61.3 | 55.6 | 66.5 | 55.3 | 59.7 | 62.6 | 58.1 | 60.5 | 55.5 | 54.3 |
| 2012 | 56.9 | 50.8 | 62.4 | 53.5 | 54 | 55.5 | 53.4 | 63.3 | 61.6 | 58.6 |
| 2013 | 58.5 | 52.8 | 65.4 | 59.2 | 56.7 | 53.1 | 53.9 | 56.4 | 56.1 | 56.8 |
| 2014 | 54.6 | 49.7 | 59.1 | 53.5 | 50.4 | 52.8 | 50.6 | 56 | 55.6 | 49.6 |
| 2015 | 61.5 | 55.1 | 66.5 | 61.7 | 57.3 | 53.6 | 63.7 | 61.3 | 62.9 | 63.3 |
| 2016 | 59.2 | 53.5 | 61.7 | 58.9 | 57.7 | 92.4 | 55.6 | 56.6 | 56.4 | 53.5 |
| 2017 | 56.6 | 53.3 | 61.4 | 57.2 | 55.7 | 57.4 | 55.4 | 60.1 | 61.8 | 55 |
| 2018 | 62.7 | 56.5 | 67.4 | 65.9 | 64.5 | 61.1 | 56.3 | 63.3 | 67.3 | 66.4 |
| 2019 | 60.3 | 55.8 | 65.4 | 57.7 | 62.3 | 55.5 | 55.9 | 57 | 66.3 | 58.2 |
| 2020 | 53 | 50.2 | 57.1 | 51.9 | 51.7 | 50.7 | 51.8 | 52.9 | 53.4 | 52.6 |
| 2021 | 58.7 | 53.3 | 63.8 | 63.4 | 60.8 | 53.8 | 55.9 | 63.9 | 69.7 | 59.9 |
| 2022 | 52.8 | 47.9 | 56.6 | 57.5 | 52.7 | 46.7 | 56.5 | 53.9 | 56.7 | 53.1 |
Select a community in the legend to toggle it on or off in the chart. Peak concentrations are calculated as the annual 4th highest daily maximum of rolling 8-hour concentrations. The 10th percentile is the value below which 10% of the data may be found. The 90th percentile is the value below which 90% of the data may be found. The high O3 concentrations observed in 2016 in Fort McMurray were due to smoke from the Horse River wildfire.
Source: Government of Alberta
Source: Government of Alberta
Table description
Line chart showing the change over time in peak O3 concentrations for large urban centres in Alberta, the provincial average, and the 10th and 90th percentile of all O3 monitoring stations in the province. The highest peak concentration was measured in Fort McMurray in 2016 with a value of 92.4 ppb due to smoke from the Horse River Wildfire.
- More recently, between 2013 and 2022, 6 out of 24 stations meeting data completeness criteria saw statistically significant increasing trends in O3 concentrations. Two of these stations are community stations in the Capital Region (Edmonton East and Fort Saskatchewan), two are regional monitoring stations in west central Alberta (Breton and Genesee), and the remaining two are community stations in Fort McMurray. All other O3 monitoring stations in the province had no statistically significant trend over this period.
- A combination of factors is likely contributing to the increasing trends in O3 observed at some monitoring stations. In recent years, there has been a number of summertime smog episodes due to hot and humid weather conditions and substantial wildfire smoke episodes have contributed to elevated O3 concentrations. In addition, the change in concentrations of nitrogen oxides over time may also play a role as nitrogen oxides can both increase and decrease O3 concentration, depending on the level of air pollution and meteorology.
Seasonal variation
- The highest O3 concentrations typically occur between March and August because of high natural background O3 levels during spring and summer smog episodes (Figure 3).
Figure 3. Monthly variation in O3 for 2022, shown using bar plots of the median monthly value across all long-term air monitoring stations. Whiskers extend from the top of the bar to the maximum monthly value across all stations.
Source: Government of Alberta
Comparison to provincial objectives
- Alberta's Ambient Air Quality Objectives provide thresholds for over 30 airborne compounds to protect human and ecosystem health. The AAAQOs are used in the design of industrial facilities and to establish emissions requirements. The Alberta government tracks AAAQO exceedances and assesses the need for management action.
- In 2022, there were 2 exceedances of the one-hour daily maximum AAAQO for O3 related to summer smog in mid-August. The AAAQO for O3 is 76 ppb for one-hour daily maximum periods based on the protection of human health.
- Over the previous 5 years (2017 to 2021), the number of AAAQO exceedances ranged from 2 exceedances in 2020 to 29 exceedances in 2021. The high number in 2021 was due to wildfire smoke and summer smog episodes that year.
Air quality reporting and resources
- Alberta reports annually on the status of air quality for existing regional air quality management frameworks (AQMFs) as well as the Canadian Ambient Air Quality Standards (CAAQS).
- O3 is one of the pollutants reported on through the South Saskatchewan Region (SSR) AQMF as well as the CAAQS.
- The most recent assessment results are available in Alberta’s Air Zone Reports.
- Published reports and scientific papers on air quality in Alberta are available via the Air Indicators landing page under ‘Related Publications’.
- Alberta also provides air quality data and information to the public through the near real-time AQHI website and provides access to quality assured data via Alberta’s Air Data Warehouse.
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