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About the indicator
Nitrogen dioxide, or NO2, is an air pollutant that can negatively affect human health and the environment. Exposure to NO2 can lead to increased risk of respiratory problems. NO2 also adversely affects ecosystems when it is deposited onto the ground, for example, through acidic deposition, commonly known as acid rain.
This indicator reports on the concentration of NO2 from 2000 to 2022 and provides information on the variation across Alberta and how concentrations have changed over time. This indicator also compares NO2 concentrations with Alberta’s Ambient Air Quality Objectives (AAAQOs), which set thresholds for air pollutants to protect human and ecosystem health.
Nitrogen dioxide facts
- Nitric oxide (NO) and NO2, collectively referred to as NOx, are gases produced during high-temperature combustion in air. Most NOx is emitted to the atmosphere as NO but is quickly converted to NO2.
- The major sources of NO2 are the emissions caused by the burning of fossil fuels used in vehicles, home heating and industrial processes. NO2 also occurs naturally in the environment due to forest fires, lightning or emissions from the soil.
- NO2 contributes to the development of other air pollutants, such as ozone, nitric acid and particulate matter. Near large cities, it contributes to smog which is visible as the brownish haze in the lower atmosphere.
- NO2 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
- NO2 concentrations have been decreasing throughout much of the province over the past 2 decades due to improved emissions control technology at sources, including personal vehicles and industry.
- Since 2005, NO2 concentrations have consistently been below the annual AAAQO across the province. Historically, exceedances of the one-hour AAAQO have occurred infrequently.
- NO2 concentrations are higher in urban areas, with Alberta’s highest concentrations in Calgary and Edmonton.
Variation across Alberta
- Alberta’s cities see higher concentrations of NO2 when compared to smaller communities, with Calgary and Edmonton showing the highest concentrations of NO2 in the province (Figures 1a and 1b).
- Higher NO2 concentrations in cities occur due to a higher number of emission sources including vehicles. Industrial sources that emit NO2 are also often located in or near urban areas.
- NO2 concentrations are also elevated near major industrial sources, such as in the mineable oil sands region and the industrial heartland northeast of Edmonton.
Figure 1a. Annual average NO2 concentrations across Alberta for 2022
Select a circle on the map to view the 2022 concentration and the 10-year trend for a specific monitoring station.
Source: Government of Alberta
Figure 1b. Peak NO2 concentrations across Alberta for 2022
Select a circle on the map to view the 2022 concentration and the 10-year trend for a specific monitoring station. Peak concentrations are calculated as the annual 98th percentile of daily maximum concentrations.
Source: Government of Alberta
Changes over time
- Between 2000 and 2022, Alberta saw an overall statistically significant decrease in annual average and peak concentrations of NO2 when averaged across all monitoring stations (Figures 2a and 2b, respectively). This trend is consistent with trends across Canada as improved technologies lowered NO2 concentrations from various emissions sources.
- Most major population centres, including Edmonton and Calgary, saw a statistically significant decrease in NO2 annual average and peak concentrations between 2000 and 2022. Annual average and peak concentrations remained steady over this period for Grande Prairie and Fort McMurray, potentially due to increased industrial operations and population growth that may offset improved emission technologies in these regions.
- More recently, between 2013 and 2022, there was a statistically significant increasing trend in NO2 concentrations at some monitoring stations (Fort Chipewyan, Fort McKay-Bertha Ganter and Fort McKay South in northeastern Alberta, Tamarack near Cold Lake, Beaverlodge near Grande Prairie, and Range Road 220, located northeast of Edmonton). However, NO2 concentrations at these stations remain low compared to stations located in larger cities. For more information on spatial variability in NO2 concentrations, see Figures 1a and 1b.
Figure 2a. Trends in annual average NO2 concentrations from 2000 to 2022 at large population centres in Alberta
Chart data table
| Year | Provincial Average | 10th Percentile | 90th Percentile | Calgary | Edmonton | Fort McMurray | Grande Prairie | Lethbridge | Medicine Hat | Red Deer | AAAQO |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2000 | 12.6 | 3.6 | 25.4 | 23.4 | 21.7 | 7 | 13.5 | 24 | |||
| 2001 | 10.8 | 1.2 | 24.2 | 22.3 | 21.9 | 7.3 | 13.5 | 24 | |||
| 2002 | 10.4 | 0.9 | 24.5 | 22.4 | 22.5 | 7.1 | 13.8 | 24 | |||
| 2003 | 11.4 | 2.9 | 25.8 | 23.5 | 22.2 | 7.7 | 14.7 | 24 | |||
| 2004 | 9.8 | 3.2 | 19.9 | 20.7 | 18.9 | 7.4 | 7 | 8.2 | 12.8 | 24 | |
| 2005 | 9.5 | 4.1 | 17.5 | 20.1 | 18.4 | 7.5 | 11.7 | 6.9 | 8.3 | 13.7 | 24 |
| 2006 | 8.7 | 3.4 | 15.1 | 19.7 | 16.7 | 7.8 | 12.1 | 6.3 | 7.9 | 12.1 | 24 |
| 2007 | 8.5 | 3.4 | 15.7 | 19 | 16.3 | 7.9 | 12.1 | 5.8 | 11.5 | 24 | |
| 2008 | 8.3 | 3.4 | 14.9 | 17.2 | 16 | 8.3 | 10.8 | 6.4 | 7.2 | 11.4 | 24 |
| 2009 | 8.2 | 2.8 | 15.7 | 18.8 | 16.1 | 8.4 | 10.8 | 5.9 | 7.6 | 11.9 | 24 |
| 2010 | 7.9 | 2.4 | 14.9 | 17.5 | 15.1 | 8.5 | 11.3 | 7.9 | 12.1 | 24 | |
| 2011 | 6.7 | 2.1 | 12.5 | 13.6 | 14.2 | 8.7 | 9 | 5.7 | 7.3 | 11.6 | 24 |
| 2012 | 6.6 | 2.7 | 11.9 | 13.1 | 14 | 7.7 | 9.6 | 5.7 | 6.9 | 10.2 | 24 |
| 2013 | 7.1 | 2.2 | 12.1 | 14 | 14.7 | 8.1 | 10 | 5.4 | 7 | 11.7 | 24 |
| 2014 | 6.9 | 2.5 | 11.8 | 15 | 13.1 | 8.2 | 11.8 | 5.4 | 6.5 | 10.9 | 24 |
| 2015 | 6.2 | 2.2 | 10.6 | 12 | 12.8 | 6.6 | 9.7 | 6 | 6.5 | 9.4 | 24 |
| 2016 | 6 | 2.3 | 10.7 | 12.5 | 11.9 | 6.6 | 9.1 | 5.2 | 5.6 | 8 | 24 |
| 2017 | 5.8 | 1.8 | 10.6 | 12.6 | 13.1 | 6.1 | 9.8 | 5.3 | 5.8 | 8.5 | 24 |
| 2018 | 6.5 | 2.2 | 11.5 | 15.8 | 13.3 | 6.3 | 11.8 | 5.8 | 7.3 | 9.8 | 24 |
| 2019 | 6.3 | 2.1 | 10.6 | 12.9 | 12.4 | 6.5 | 11 | 5.5 | 6.8 | 9.3 | 24 |
| 2020 | 5.7 | 1.7 | 10.1 | 12.2 | 11.8 | 5.9 | 9.3 | 4.5 | 5.6 | 8.2 | 24 |
| 2021 | 5.7 | 1.8 | 9.8 | 11.8 | 11.3 | 6.1 | 9.7 | 4.8 | 5.6 | 8.3 | 24 |
| 2022 | 5.8 | 1.7 | 10.3 | 11.6 | 11.7 | 6.1 | 10.1 | 4.6 | 5.8 | 8.2 | 24 |
Select a community in the legend to toggle it on or off in the chart. 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 horizontal dashed line represents the Alberta Ambient Air Quality Objective (AAAQO) for annual average NO2.
Source: Government of Alberta
Source: Government of Alberta
Accessible chart description
Line chart showing the change over time in annual average NO2 concentrations for large urban centres in Alberta, the provincial average, and the 10th and 90th percentile of all NO2 monitoring stations in the province. The chart also displays the Alberta Ambient Air Quality Objective for annual average NO2 (24 ppb). Provincial average NO2 annual average concentrations and several large urban centres' concentrations (Calgary, Edmonton, Lethbridge, Medicine Hat, and Red Deer) have decreased since 2000. The Provincial Average of annual average NO2 concentrations was 12.6 ppb in 2000 and 5.8 ppb in 2022.
Figure 2b. Trends in peak NO2 concentrations from 2000 to 2022 at large population centres in Alberta
Chart data table
| Year | Provincial Average | 10th Percentile | 90th Percentile | Calgary | Edmonton | Fort McMurray | Grande Prairie | Lethbridge | Medicine Hat | Red Deer |
|---|---|---|---|---|---|---|---|---|---|---|
| 2000 | 47.9 | 25.3 | 70.5 | 66.7 | 69 | 36.5 | 53 | |||
| 2001 | 43.6 | 15.2 | 73 | 67 | 67.3 | 41 | 44 | |||
| 2002 | 43.2 | 17.8 | 82 | 74.3 | 73 | 38.5 | 48 | |||
| 2003 | 49.3 | 20.8 | 77.2 | 70 | 71.3 | 39.5 | 53 | |||
| 2004 | 45.2 | 28.6 | 64.6 | 69.3 | 63 | 41.5 | 39 | 43 | 52 | |
| 2005 | 45.4 | 26.1 | 66.5 | 67 | 64.3 | 41 | 58 | 45 | 40.8 | 53 |
| 2006 | 41.8 | 26 | 59.6 | 64.3 | 58.3 | 47 | 51.5 | 40 | 39 | 49 |
| 2007 | 42.2 | 26.8 | 60.6 | 60 | 57.3 | 39.5 | 53 | 41 | 44 | |
| 2008 | 46.7 | 27 | 77 | 71.6 | 55.7 | 40 | 54.5 | 39 | 41.5 | 47 |
| 2009 | 43.6 | 25.4 | 65.4 | 69.1 | 59 | 40.5 | 53.7 | 40 | 43.1 | 49.3 |
| 2010 | 41.1 | 23.6 | 62 | 67.8 | 55.7 | 44.5 | 51.1 | 42.1 | 46.9 | |
| 2011 | 38.5 | 19 | 54 | 62.9 | 52 | 43 | 46 | 46 | 41 | 49.4 |
| 2012 | 36.8 | 19.9 | 51.6 | 57.4 | 50.7 | 39 | 46 | 38.2 | 34.9 | 45.2 |
| 2013 | 39.1 | 21.1 | 55.4 | 57.9 | 58.6 | 45.5 | 55.4 | 37 | 35.6 | 48.7 |
| 2014 | 37.8 | 23.4 | 54.6 | 55.1 | 51.7 | 52.9 | 55 | 41.9 | 33.9 | 46.5 |
| 2015 | 36 | 21.4 | 52.7 | 55.9 | 51.4 | 38.7 | 52.6 | 38.8 | 32.9 | 40.7 |
| 2016 | 33.8 | 18.7 | 50.1 | 54.3 | 48.1 | 36.3 | 50.2 | 36.9 | 30.3 | 39.8 |
| 2017 | 32.9 | 16.2 | 50.5 | 54.8 | 51.1 | 39.2 | 50.8 | 36.3 | 35.1 | 39.8 |
| 2018 | 36.3 | 18.9 | 54.6 | 65.2 | 54.5 | 38.6 | 59.1 | 43.5 | 42.9 | 44.5 |
| 2019 | 36.7 | 17.4 | 54.9 | 57.6 | 54 | 39.4 | 55.2 | 40.1 | 42.3 | 44 |
| 2020 | 34.6 | 16.4 | 50.7 | 56.3 | 52.6 | 37.5 | 49.5 | 34.2 | 33.4 | 40.7 |
| 2021 | 32.9 | 15.9 | 48.6 | 56.2 | 47.5 | 36.8 | 48.9 | 34 | 31.9 | 38.6 |
| 2022 | 35.3 | 16.6 | 51.2 | 54.6 | 51.8 | 39.5 | 56.2 | 37.6 | 36.5 | 42.9 |
Select a community in the legend to toggle it on or off in the chart. Peak concentrations are calculated as the annual 98th percentile of daily maximum 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.
Source: Government of Alberta
Source: Government of Alberta
Accessible chart description
Line chart showing the change over time in peak NO2 concentrations for large urban centres in Alberta, the provincial average, and the 10th and 90th percentile of all NO2 monitoring stations in the province. Provincial average NO2 peak concentrations and several large urban centres' concentrations (Calgary, Edmonton, and Red Deer) have decreased since 2000. The Provincial Average of peak NO2 concentrations was 47.9 ppb in 2000 and 35.3 ppb in 2022.
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.
- Since 2005, NO2 concentrations have consistently been below the annual AAAQO for all stations across the province (Figure 2a). The annual objective for NO2 is 24 parts per billion (ppb) based on the protection of ecosystems.
- In 2022, there were no exceedances of the one-hour AAAQO for NO2. Historically, exceedances of the one-hour AAAQO for NO2 have occurred infrequently – 0 to 3 times per year – in various locations across Alberta. The one-hour AAAQO for NO2 is 159 ppb based on the protection of human health.
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).
- NO2 is one of the pollutants reported on through the South Saskatchewan Region (SSR) AQMF and Lower Athabasca Region (LAR) 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.
Focused study
On March 16, 2020, Alberta declared a public health emergency and enacted measures to reduce the spread of COVID-19. Measures included the closure of schools and daycares, the restriction of gatherings and mandated physical distancing. A study was undertaken to see if there was a temporary decrease in the concentration of air pollutants due to reduced road traffic in Alberta’s urban centres as a result of these measures.
- Between March 16 and April 24, 2020, concentrations of NO2 in the air in Alberta’s 2 largest cities, Calgary and Edmonton, were at least 14% lower than in previous years (Figure 3).
- Decreases in NO2 concentrations were also observed in satellite data for urban areas in Alberta.
- Decreased NO2 concentrations coincided with 8 to 41% decreases in road traffic, which is a major emission source of this pollutant in cities.
For further details, visit:
Figure 3. Mean NO2 concentrations in select urban centres across Alberta
Chart data table
| Location | 2015 - 2019 | 2020 |
|---|---|---|
| Edson | 6.26 | 5.02 |
| Hinton | 8.33 | 5.56 |
| Cold Lake | 3.14 | 3.4 |
| Medicine Hat | 5.72 | 5.5 |
| Grande Prairie | 9.6 | 8.46 |
| Fort McMurray | 5.08 | 6.14 |
| Lethbridge | 5.62 | 4.92 |
| Fort Saskatchewan | 6.88 | 6.08 |
| Red Deer Riverside | 8.35 | 7.38 |
| Red Deer Lancaster | 6.89 | 6.77 |
| Edmonton East | 12.22 | 10.52 |
| Edmonton Central | 16.93 | 13.75 |
| Calgary SE | 13.13 | 9.91 |
| Calgary Inglewood | 14.74 | 11.37 |
Data include sample period between March 16 and April 24, 2020 (excluding weekends and holidays) and the same time-period in previous years (2015-2019).
Change in mean NO2 observed in Medicine Hat was not statistically significant.
Source: Government of Alberta
Source: Government of Alberta
Accessible chart description
Bar chart showing mean NO2 concentrations for the period between March 16 to April 24, 2020 and the same time period in previous years (2015 to 2019) for monitoring stations in select urban centres in Alberta.
Stations near downtown Calgary and Edmonton saw mean NO2 concentrations decrease by approximately 3 ppb. In Alberta’s smaller urban centres concentrations of NO2 are normally lower and most centres saw a decrease of 1 ppb or less.
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