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 rain.
This indicator reports on the concentration of NO2 from 2000 to 2021 and compares it to Alberta’s Ambient Air Quality Objectives (AAAQOs), which set thresholds for air pollutants to protect human and ecosystem health. This indicator also discusses management of NO2 concentrations in Alberta under the Canadian Ambient Air Quality Standards (CAAQS).
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 is partly responsible for the brownish colour of the air 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.
Methodology
Summary of key results
Last updated: April 2023
- NO2 concentrations are higher in urban areas, with Alberta’s highest concentrations in Calgary and Edmonton.
- 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.
- Despite the decreasing trend, NO2 concentrations in some urban areas approach or even exceed the CAAQS.
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 to the east of Edmonton.
Figure 1a. Annual average NO2 concentrations across Alberta for 2021
Select a circle on the map to view the 2021 concentration and the 10-year trend for a specific monitoring station.
Source: Government of Alberta
Figure 1b. Peak NO2 concentrations across Alberta for 2021
Select a circle on the map to view the 2021 concentration and the 10-year trend for a specific monitoring station.
Source: Government of Alberta
Changes over time
- Between 2000 and 2021, Alberta saw an overall decrease of 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 decrease in NO2 annual average concentrations. Annual average concentrations remained steady for Grande Prairie and Fort McMurray, potentially due to increased industrial operations and population growth that may offset improved emission technologies in these regions.
- Peak NO2 concentrations also decreased in Edmonton, Calgary and Red Deer. No trend in peak NO2 was detected for the other major population centres.
- More recently, between 2011 and 2021, NO2 concentrations increased at some monitoring stations (Fort Chipewyan in northeastern Alberta, Tamarack near Cold Lake, and Range Road 220, located east of Edmonton). NO2 concentrations at these stations are low compared to stations located in larger cities or near major industrial sources. For more information on spatial variability in NO2 concentrations, see Figures 1a and 1b.
Figure 2a. Trends in annual average NO2 concentrations over time
Chart data table
| Year | Provincial Average | 10th Percentile | 90th Percentile | Calgary | Edmonton | Fort McMurray | Grande Prairie | Lethbridge | Medicine Hat | Red Deer | CAAQS |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2000 | 12.6 | 3.6 | 25.4 | 23.4 | 21.7 | 7 | 13.5 | 17 | |||
| 2001 | 10.8 | 1.2 | 24.2 | 22.3 | 21.9 | 7.3 | 13.5 | 17 | |||
| 2002 | 10.4 | 0.9 | 24.5 | 22.4 | 22.5 | 7.1 | 13.8 | 17 | |||
| 2003 | 11.4 | 2.9 | 25.8 | 23.5 | 22.2 | 7.7 | 14.7 | 17 | |||
| 2004 | 9.8 | 3.2 | 19.9 | 20.7 | 18.9 | 7.4 | 7 | 8.2 | 12.8 | 17 | |
| 2005 | 9.5 | 4.1 | 17.5 | 20.1 | 18.4 | 7.5 | 11.7 | 6.9 | 8.3 | 13.7 | 17 |
| 2006 | 8.7 | 3.4 | 15.1 | 19.7 | 16.7 | 7.8 | 12.1 | 6.3 | 7.9 | 12.1 | 17 |
| 2007 | 8.5 | 3.4 | 15.7 | 19 | 16.3 | 7.9 | 12.1 | 5.8 | 11.5 | 17 | |
| 2008 | 8.3 | 3.4 | 14.9 | 17.2 | 16 | 8.3 | 10.8 | 6.4 | 7.2 | 11.4 | 17 |
| 2009 | 8.2 | 2.8 | 15.7 | 18.8 | 16.1 | 8.4 | 10.8 | 5.9 | 7.6 | 11.9 | 17 |
| 2010 | 7.9 | 2.4 | 14.9 | 17.5 | 15.1 | 8.5 | 11.3 | 7.9 | 12.1 | 17 | |
| 2011 | 6.7 | 2.1 | 12.5 | 13.6 | 14.2 | 8.7 | 9 | 5.7 | 7.3 | 11.6 | 17 |
| 2012 | 6.6 | 2.7 | 11.9 | 13.1 | 14 | 7.7 | 9.6 | 5.7 | 6.9 | 10.2 | 17 |
| 2013 | 7.1 | 2.2 | 12.1 | 14 | 14.7 | 8.1 | 10 | 5.4 | 7 | 11.7 | 17 |
| 2014 | 6.9 | 2.5 | 11.8 | 15 | 13.1 | 8.2 | 11.8 | 5.4 | 6.5 | 10.9 | 17 |
| 2015 | 6.2 | 2.2 | 10.6 | 12 | 12.8 | 6.6 | 9.7 | 6 | 6.5 | 9.4 | 17 |
| 2016 | 6 | 2.3 | 10.7 | 12.5 | 11.9 | 6.6 | 9.1 | 5.2 | 5.6 | 8 | 17 |
| 2017 | 5.8 | 1.8 | 10.6 | 12.6 | 13.1 | 6.1 | 9.8 | 5.3 | 5.8 | 8.5 | 17 |
| 2018 | 6.5 | 2.2 | 11.5 | 15.8 | 13.3 | 6.3 | 11.8 | 5.8 | 7.3 | 9.8 | 17 |
| 2019 | 6.3 | 2.1 | 10.6 | 12.9 | 12.4 | 6.5 | 11 | 5.5 | 6.8 | 9.3 | 17 |
| 2020 | 5.7 | 1.7 | 10.1 | 12.2 | 11.8 | 5.9 | 9.3 | 4.5 | 5.6 | 8.2 | 17 |
| 2021 | 5.7 | 1.8 | 9.8 | 11.8 | 11.3 | 6.1 | 9.7 | 4.8 | 5.6 | 8.3 | 17 |
The horizontal dashed lines represent the 2020 Canadian Ambient Air Quality Standards. The Canadian Ambient Air Quality Standards are provided for illustrative purposes only and not for assessing the achievement status of the standards. For information on achievement status see the Alberta Air Zones report.
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 2020 Canadian Ambient Air Quality Standard for NO2 annual average (17 ppb) for comparison. 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 5.7 ppb in 2021.
Figure 2b. Trends in peak NO2 concentrations over time
Chart data table
| Year | Provincial Average | 10th Percentile | 90th Percentile | Calgary | Edmonton | Fort McMurray | Grande Prairie | Lethbridge | Medicine Hat | Red Deer | CAAQS |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2000 | 47.9 | 25.3 | 70.5 | 66.7 | 69 | 36.5 | 53 | 60 | |||
| 2001 | 43.6 | 15.2 | 73 | 67 | 67.3 | 41 | 44 | 60 | |||
| 2002 | 43.2 | 17.8 | 82 | 74.3 | 73 | 38.5 | 48 | 60 | |||
| 2003 | 49.3 | 20.8 | 77.2 | 70 | 71.3 | 39.5 | 53 | 60 | |||
| 2004 | 45.2 | 28.6 | 64.6 | 69.3 | 63 | 41.5 | 39 | 43 | 52 | 60 | |
| 2005 | 45.4 | 26.1 | 66.5 | 67 | 64.3 | 41 | 58 | 45 | 40.8 | 53 | 60 |
| 2006 | 41.8 | 26 | 59.6 | 64.3 | 58.3 | 47 | 51.5 | 40 | 39 | 49 | 60 |
| 2007 | 42.2 | 26.8 | 60.6 | 60 | 57.3 | 39.5 | 53 | 41 | 44 | 60 | |
| 2008 | 46.7 | 27 | 77 | 71.6 | 55.7 | 40 | 54.5 | 39 | 41.5 | 47 | 60 |
| 2009 | 43.6 | 25.4 | 65.4 | 69.1 | 59 | 40.5 | 53.7 | 40 | 43.1 | 49.3 | 60 |
| 2010 | 41.1 | 23.6 | 62 | 67.8 | 55.7 | 44.5 | 51.1 | 42.1 | 46.9 | 60 | |
| 2011 | 38.5 | 19 | 54 | 62.9 | 52 | 43 | 46 | 46 | 41 | 49.4 | 60 |
| 2012 | 36.8 | 19.9 | 51.6 | 57.4 | 50.7 | 39 | 46 | 38.2 | 34.9 | 45.2 | 60 |
| 2013 | 39.1 | 21.1 | 55.4 | 57.9 | 58.6 | 45.5 | 55.4 | 37 | 35.6 | 48.7 | 60 |
| 2014 | 37.8 | 23.4 | 54.6 | 55.1 | 51.7 | 52.9 | 55 | 41.9 | 33.9 | 46.5 | 60 |
| 2015 | 36 | 21.4 | 52.7 | 55.9 | 51.4 | 38.7 | 52.6 | 38.8 | 32.9 | 40.7 | 60 |
| 2016 | 33.8 | 18.7 | 50.1 | 54.3 | 48.1 | 36.3 | 50.2 | 36.9 | 30.3 | 39.8 | 60 |
| 2017 | 32.9 | 16.2 | 50.5 | 54.8 | 51.1 | 39.2 | 50.8 | 36.3 | 35.1 | 39.8 | 60 |
| 2018 | 36.3 | 18.9 | 54.6 | 65.2 | 54.5 | 38.6 | 59.1 | 43.5 | 42.9 | 44.5 | 60 |
| 2019 | 36.7 | 17.4 | 54.9 | 57.6 | 54 | 39.4 | 55.2 | 40.1 | 42.3 | 44 | 60 |
| 2020 | 34.6 | 16.4 | 50.7 | 56.3 | 52.6 | 37.5 | 49.5 | 34.2 | 33.4 | 40.7 | 60 |
| 2021 | 32.9 | 15.9 | 48.6 | 56.2 | 47.5 | 36.8 | 48.9 | 34 | 31.9 | 38.6 | 60 |
The horizontal dashed lines represent the 2020 Canadian Ambient Air Quality Standards. The Canadian Ambient Air Quality Standards are provided for illustrative purposes only and not for assessing the achievement status of the standards. For information on achievement status see the Alberta Air Zones report.
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. The chart also displays the 2020 Canadian Ambient Air Quality Standard for NO2 1-hour (60 ppb) for comparison. 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 32.9 ppb in 2021.
Comparison to provincial objectives
- Alberta’s Ambient Air Quality Objectives (AAAQOs) provide maximum acceptable thresholds for over 30 airborne compounds to protect human and ecosystem health. All industrial facilities must be designed and operated to remain below these thresholds. When air quality exceeds an AAAQO, the Alberta government assesses the cause and determines whether corrective action is required.
- 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 2021, there were no exceedances of the one-hour AAAQO. Historically, exceedances of the one-hour AAAQO have occurred infrequently – 0 to 3 times per year – in various locations across Alberta. The one-hour AAAQO is 159 ppb based on the protection of human health.
Comparison to national standards
- To guide management in air quality across Canada, the Canadian Ambient Air Quality Standards (CAAQS) have been developed for the following air pollutants: fine particulate matter (PM2.5), nitrogen dioxide (NO2, new since 2020), ground level ozone (O3) and sulphur dioxide (SO2).
- NO2 concentrations in Alberta approach or even exceed the CAAQS in urban areas, despite the decreasing trend in NO2 concentrations seen across Alberta.
- Annual reporting of Alberta’s air quality against the CAAQS is available in Alberta’s
Air Zone Reports.- In the first assessment of the NO2 standards (2018-2020), most regions of the province were at the Orange Level – Actions for Preventing CAAQS Exceedances, with the exception of the South Saskatchewan region where one station (Calgary Central-Inglewood) was at the Red Level – Actions for Reducing Pollutant Levels Below the CAAQS.
- Work is ongoing to manage elevated NO2 concentrations through air quality management plans. For details, see the Canadian Ambient Air Quality Standards under ‘Management plans’.
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. This 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.
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.