Air indicators – Fine particulate matter

About the indicator

Fine particulate matter, or PM_2.5, is an air pollutant that can be harmful to human health. PM_2.5 consists of very small particles 2.5 micrometres or less in diameter. Exposure to these small particles can cause serious health problems including lung and heart disease.

This indicator reports on the concentration of PM_2.5 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 ongoing management of PM_2.5 concentrations in Alberta under the Canadian Ambient Air Quality Standards (CAAQS).

Fine particulate matter facts

• PM_2.5 is emitted into the atmosphere from human activities and natural emission sources such as wildfire smoke. Some PM_2.5 is emitted directly into the atmosphere, for example through dust or smoke. PM_2.5 also forms through chemical reactions in the atmosphere involving other gases, such as nitrogen dioxide, sulphur dioxide and volatile organic compounds.
• Human caused sources of PM_2.5 include using fossil fuels for vehicles, home heating, power plants, and industrial processes. Other sources include home wood burning, brush pile burning, road dust, and construction operations, among others.
• In Alberta, the highest concentrations of PM_2.5 are typically caused by wildfire smoke and winter smog. Smog is a mixture of gases and particles emitted into the air by human activities. Smog negatively affects human health and forms haze that reduces visibility.
• PM_2.5 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

• Condition of the Environment Report – Air Component

Summary of key results

Last updated: April 2023

• The highest concentrations of PM_2.5 in Alberta are caused by wildfire smoke and can reach concentrations that exceed the AAAQO, which is based on the protection of human health. The location and severity of smoke varies year-to-year depending primarily on wildfire intensity and activity.
• Human activities also significantly contribute to PM_2.5 concentrations, primarily during winter smog episodes. Alberta is taking action to manage PM_2.5 levels associated with human activities under the CAAQS.

Variation across Alberta

• Annual average and peak concentrations of PM_2.5 vary across Alberta (Figures 1a and 1b, respectively) and are driven primarily by wildfire smoke and winter smog.
  • PM_2.5 concentrations are highest in large population centres and near industrial emissions sources. Stations located outside of these areas (for example in regional locations and smaller communities) have lower PM_2.5 concentrations.
  • PM_2.5 concentrations are also highest in areas more affected by wildfire smoke.
• Wildfire smoke affects different parts of the province each year. The location of wildfires and the wind patterns that transport smoke determine which regions are affected. For more information on how wildfire smoke affects air quality in Alberta, see: Wildfire Smoke: Impacts on Air Quality in Alberta.
  • In 2021, wildfire smoke from fires burning in British Columbia and the northwestern United States throughout the months of July and August, as well as smoke from wildfires in Saskatchewan in early October, affected much of the province.

Figure 1a. Annual average PM_2.5 concentrations across Alberta for 2021

Figure 1b. Peak PM_2.5 concentrations across Alberta for 2021

Changes over time

• The difference in PM_2.5 concentrations between years is largely driven by the extent of wildfire smoke and the frequency and severity of winter smog episodes (Figures 2a and 2b).
• In 2021, provincial average concentrations of PM_2.5 were similar to other years over the past decade (for example, 2011 to 2015 annual averages; 2015 and 2016 peak values).
  • Annual average and peak PM_2.5 concentrations were higher in 2021 compared to 2020, when there was reduced wildfire activity in Alberta and limited impact from wildfires in surrounding jurisdictions.
  • Actions taken in response to COVID-19 may have also affected PM_2.5 due to changes in emissions of air pollutants from sources such as vehicle traffic.
• Trends over time for PM_2.5 cannot be tested statistically because of changes in monitoring equipment (see limitations section below).

​Seasonal variation

• Higher concentrations of PM_2.5 occur during periods affected by wildfire smoke (Figure 3).
• Elevated concentrations also occur during winter smog episodes caused by human emissions from November to March. Winter smog has a smaller effect on PM_2.5 concentrations compared to wildfire smoke, which is why smog contributions are not as apparent in Figure 3 as those from wildfires.
  • Winter smog typically occurs during temperature inversions, when cold air along with pollutants are trapped at ground level preventing dispersion of pollutants into the atmosphere.
• PM_2.5 concentrations can also be elevated at other times of year due to summer smog episodes, high wind dust events and other local causes.

Figure 3. Seasonal variation in monthly average PM_2.5 for 2018 to 2021, 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. Major wildfire episodes are indicated for each year.

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.
• Exceedances of the 24-hour AAAQO for PM_2.5 are mainly caused by wildfire smoke and winter smog episodes (Figure 4). In 2021, there were 473 exceedances of the 24-hour AAAQO for PM_2.5 in various locations across Alberta. Some air monitoring stations experienced up to 19 days of exceedances. The AAAQO for PM_2.5 is 29 µg/m³ for 24-hour periods based on the protection of human health.

Comparison to national standards

• To guide management of air quality across Canada, the Canadian Ambient Air Quality Standards (CAAQS) have been developed for the following air pollutants: fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), ground level ozone (O₃) and sulphur dioxide (SO₂).
• Analyses against the CAAQS specifically assess human-caused air quality issues that can be controlled through management actions while events outside the control of jurisdictions, such as wildfire smoke, are not included.
• PM_2.5 levels approach the CAAQS in several regions of the province, primarily due to winter smog caused by human emissions.
• Annual reporting of Alberta’s air quality against the CAAQS is available in Alberta's
  Air Zone Reports.
  • For the 2018-2020 reporting period, 4 areas of the province were at the Orange Level – Actions for Preventing CAAQS Exceedances. The remaining two areas of the province (the Peace Region and Red Deer Region) were at the Yellow Level – Actions for Preventing Air Quality Deterioration.
  • Work is ongoing to prevent exceedances of CAAQS through air quality management plans. For details, see the Canadian Ambient Air Quality Standards under ‘Management plans’.

Limitations of the dataset

• Between 2010 and 2017, older equipment at Alberta’s monitoring stations was replaced with new monitoring equipment for PM_2.5. These new instruments measure an additional portion (semi-volatile) of the PM_2.5 mass not captured by older instruments.
• As older monitoring equipment used between 2000 and 2017 likely underreported concentrations of PM_2.5 under some conditions, after 2010, the increase in PM_2.5 concentrations may be a result of changes in monitoring equipment. Concentrations measured with the new monitors may not be directly comparable with measurements from years in which older instruments were used.

Focused study

In response to an exceedance of the national Canadian Ambient Air Quality Standards (CAAQS) in the Red Deer area in the 2011-2013 assessment, a focused study was initiated to measure PM_2.5 composition and precursor gases at 3 monitoring stations between 2017 and 2019. The objective of the study was to assess PM_2.5 regional and local sources and inform management actions to improve air quality.

Key findings include:

• Elevated PM_2.5 concentrations were regional scale events, with similar and correlated concentrations observed at two stations in Red Deer, and at a site located 9.4 km upwind.
• When wildfire-impacted samples are removed, PM_2.5 concentrations are largest in the spring, and are dominated by the sulphate and nitrate factors (74%) (Figure 5).
• The sulphate factor is consistent with a regional source, which could include the coal-fired power plants and the smaller upstream oil and gas operations in the area. The elevated nitrate factors appeared to be affected by local emissions sources, which could include both urban and industrial sources, and promoted by meteorological conditions.
• Reducing oxides of nitrogen could help to manage PM_2.5 concentrations in the region.

Resources

• Air quality data and reports
• Air Monitoring
• Alberta Air Zone Reports
• Ambient Air Quality Objectives (AAAQOs)
• Canadian Ambient Air Quality Standards (CAAQS) 
• Environment and land use planning