Air indicators – Wildfire smoke

About the indicator

When wildfires burn trees and other plant material, they emit smoke, which is a complex mixture of gases and particles. The smoke is then transported over short and long distances, including across provincial and federal borders. Wildfire smoke can often impact large areas hundreds of square kilometres in size for extended periods of time (days or weeks).

Wildfire smoke is a major contributor to poor air quality and can have far-reaching impacts on both the environment and human health. The smoke generated by a wildfire contains a mixture of pollutants, including particulate matter, carbon monoxide, nitrogen oxides, and volatile organic compounds (VOCs), which can be harmful when inhaled.

This indicator provides information on wildfire prevalence (estimated area burned between 1990 and 2021) and wildfire smoke impacts on air quality (the number of days a long-term air quality monitoring station is impacted by wildfire smoke between 2015 and 2021).

Wildfire smoke facts

• Wildfire season varies across different jurisdictions. In Alberta, the official wildfire season is set provincially and runs from March 1 to October 31. Due to Alberta experiencing warmer than normal temperatures and below average precipitation, wildfire season in 2024 was declared on February 20, 2024.
• One of the primary health impacts of wildfire smoke is its effect on respiratory health. Fine particulate matter (PM_2.5) — particles that are less than 2.5 micrometers (µm) in diameter — within smoke can penetrate deep into the lungs and cause irritation making it difficult to breathe. This makes those with pre-existing medical conditions, especially underlying heart and/or lung problems, particularly vulnerable.
  • Other pollutants that are in, or created by, wildfire smoke include nitrogen dioxide (NO₂), ozone (O₃), sulphur dioxide (SO₂), and polycyclic aromatic hydrocarbons (PAHs), among others.
  • The type and concentration of pollutants in wildfire smoke depend on many factors including the distance that smoke has travelled, the type of vegetation burned and the age of the smoke.
  • Wildfire smoke can reduce visibility, irritate the eyes, cause strong odour, and can have significant impacts on outdoor activities. Smoke can also affect indoor air quality.
• Wildfires can be caused by both natural events (for example lightning) and human activity (for example campfires, fireworks, off-highway vehicles, incendiary, industrial activity).
• Recorded wildfires vary dramatically in size with some being less than 100 m² to some being over 1,000 km² (which is approximately the size of Calgary or Edmonton).
• Area burned by wildfires are increasing in some areas most likely due to increasing global temperatures and increased human activity (IPCC, 2022). This can result in an increase in poor air quality from wildfire smoke.
  • The extent of burned area in a given year is influenced by the presence of long-term drought, high winds, timing and location of precipitation, extreme weather events, among other factors.
• Wildfire smoke experienced by Albertans most often originates from fires burning in Alberta, British Columbia (B.C.), and the northwestern United States (U.S.) due to predominant wind directions.

For more information on wildfire smoke and air quality in Alberta, see the wildfire smoke information page.

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: April 2024

• The total estimated area burned by wildfires in Alberta has increased in recent decades (1990-1999: 1,494,851 ha; 2000-2009: 1,976,752 ha; 2010-2019: 4,572,708 ha) and wildfires are becoming more prevalent in spring months.
• Effects of wildfires and wildfire smoke differ across regions depending on the time of year.
• In 2021, northern regions in Alberta observed more wildfire smoke impacts in May, while southern regions observed more impacts from smoke in August.

Variation across Alberta

• In 2021, wildfire smoke from fires in B.C. and the northwestern U.S. throughout July and August, as well as smoke from wildfires in Saskatchewan in early October, affected much of the province.
• Wildfire smoke impacts on air quality vary across the province depending on the location and extent of wildfires. One of the major components of smoke that poses a risk to human health is PM_2.5. Figure 1 shows the number of days affected by wildfire smoke with elevated PM_2.5 concentrations (daily average PM_2.5 > 15 µg/m³) for select monitoring stations in the province in 2021.
  • In general, stations in southern Alberta were affected more frequently by wildfire smoke than those in northern Alberta.
  • The station most affected by wildfire smoke in 2021 was the Tomahawk station to the west of Edmonton which was impacted for a total of 36 days. A fire in close proximity to the monitoring station frequently affected air quality from May to October. Other stations in Alberta saw limited effects from this fire.
• The areas of the province that are impacted by wildfire smoke change from year to year.
  • In 2019, wildfires were burning in northern Alberta (near the communities of High Level and Slave Lake) starting in late-May, followed by wildfires in northeastern Alberta in mid-to-late July. Smoke from these wildfires primarily affected northern Alberta, but was transported throughout Alberta in late-May and early-June.
  • In 2020, smoke from wildfires burning in the northwestern U. S. travelled to Alberta, primarily affecting central and southern Alberta throughout September.

Figure 1. Number of days that a station was impacted by wildfire smoke in Alberta in 2021. Circles represent current long-term continuous air quality monitoring stations.

Changes over time

Wildfire prevalence

• Figure 2 shows the total estimated area burned (in hectares) for northwestern Canadian provinces and territories as well as western U.S. states. Due to the random occurrence of megafires (greater than 40,500 ha) that can occur for a variety of reasons, it is difficult to identify trends in the data.
  • It is not clear whether the annual total area burned in these regions has increased over the last 20 years.
• The area burned in Alberta and neighbouring provinces and territories that impact Alberta, is often greater than the area burned in western U.S. states (Figure 2). This could be due to several factors, such as differences in region total area, population, fire prevention practices, among others.
  • 2020 is notable for a small total area burned across Alberta and neighbouring Canadian provinces, attributed to many factors including substantial precipitation (CIFFC, 2020).
  • However, 2020 was a very active fire season in the western U.S. with area burned in California being the highest over the past 20 years.
• In 2023, (not shown here), wildfires burned more area in Alberta than in any previously recorded year. For more information on wildfires in Alberta see the Alberta Wildfire page.

Wildfire smoke impacts

• The number of wildfire smoke impacted days (daily average PM_2.5 > 15 µg/m³) is similar across Alberta’s large urban centres between 2015 to 2021 (Figure 3). The notable exception is the Fort McMurray air quality monitoring station in 2016 which was significantly impacted by the Horse River Wildfire (see focused study).
• The amount of time that wildfire smoke affects a monitoring station each year is highly variable and depends on several factors, including fire location, meteorology, among others.

Seasonal variation

Wildfire prevalence

• The timeline for wildfire activity varies across different regions (Figure 4), but wildfires generally begin in late spring and taper off in early fall. For Alberta, wildfire activity peaks in May and tends to decline in area burned through June, which is typically the province’s wettest month. Whereas, in B.C., wildfire activity peaks in July and August when conditions are hottest and driest.
• In the most recent decade, Alberta fires have burned more hectares in May and June than in earlier decades. British Columbia fires have remained most prevalent in July, albeit, with area burned increasing over the past 3 decades, possibly due to climate change and increased human activity.

Wildfire smoke impacts

• Figure 5 shows the total number of days that Alberta’s large urban centres were affected by wildfire smoke (daily average PM_2.5 > 15 ug/m³) by month during the 2015 to 2021 period.
  • Northern areas, like Fort McMurray and Grande Prairie, experienced the most wildfire smoke days earlier in the wildfire season (i.e., May) compared with other stations.
  • Southern areas, like Lethbridge and Medicine Hat, experienced the most wildfire smoke days later in the wildfire season (i.e., August)

Limitations of the dataset

• Only days with daily average PM_2.5 concentration greater than 15 µg/m³ were included in the identified wildfire smoke impacted days. There may be additional days with lower PM_2.5 concentrations that were impacted by wildfire smoke but not included in the results. For data showing total number of impacted days, only urban stations were included due to limited data in rural regions.
• Long-term air quality monitoring stations do not cover all regions of Alberta, therefore monitoring gaps may incorrectly suggest that wildfire smoke impacts do not occur in those areas.
• Different jurisdictions might vary in their reporting of area burned due to differences in land use, among others.
  • For example, Alberta reports area burned within the province’s Forest Protection Area, while Saskatchewan reports area burned data under the Intensive Protection Zone.
• Additionally, U.S. data from the National Interagency Fire Center is only available from 2002 onward. U.S. data beyond 2018 does not include prescribed burns (which are not expected to be significant in size).
• Wildfire burn data from the National Forestry Database (used in this indicator) are available up until 2021 as of the posting of this indicator.

Focused study

The Alberta government deploys air quality monitoring to support emergency response during wildfires. During the 2016 Horse River wildfire in Fort McMurray, air monitoring was deployed to support decisions to protect the health of emergency response personnel and the public. The report,Characterization of air quality during the 2016 Horse River wildfire, summarizes air quality data collected during the fire.

The extent of the wildfire is shown in Figure 6. Very high concentrations of PM_2.5 that exceeded health-based objectives were observed from both permanent and portable air quality monitoring equipment due to wildfire smoke. In addition to PM_2.5, concentrations of NO₂, ammonia (NH₃), SO₂, and carbon monoxide (CO) were also monitored. Median hourly NH₃ concentrations were 3 times and 22 times larger during the wildfire than during the non-wildfire impacted period at the Fort McKay-Bertha Ganter monitoring station and Fort McMurray-Patricia McInnes monitoring station, respectively. Furthermore, 13 episodes of hourly CO concentrations exceeding the health-based Alberta Ambient Air Quality Objective (AAAQO) of 13 ppm were recorded at the Fort McMurray-Athabasca Valley station, and the median hourly concentrations were 2 times higher than the non-wildfire impacted period.

This demonstrates that measurements of additional parameters provide valuable information about the composition of the smoke plume and risk to human health.

Resources

Air Monitoring

Air quality data and reports

Alberta Air Zone Reports

Ambient Air Quality Objectives (AAAQOs)

Canadian Ambient Air Quality Standards (CAAQS)

Environment and land use planning

Wildfire smoke information