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.
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.
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