Canadian cities enjoy some of the cleanest air on Earth – and in recent decades it’s been getting cleaner. Yet the western provinces buck that trend: Communities in British Columbia and Alberta have recorded some of the worst air pollution levels in the country in recent years, a report from Environment and Climate Change Canada shows.
The culprit is no mystery: It’s wildfires.
Burning forests and grasslands release plumes of dense smoke. How far they travel depends on wind and weather patterns and fire intensity, but they routinely degrade air quality thousands of kilometres away. In extreme cases, Canadian air quality has been significantly impaired by fires as distant as the western United States and even Siberia.
“Wildfire smoke is the air quality issue in Canada, now and for the future,” said Michael Brauer, a professor at the University of British Columbia who studies the health effects of air pollution.
Forest fire smoke covers Edmonton in 2019.SOCIAL MEDIA/Reuters
Wildfire smoke is a noxious cocktail of gases, water vapour and particles that contains sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide, volatile organic compounds and, most importantly, fine particulate matter – tiny liquid or solid bits with diameters of less than 2.5 micrometres (µm), called PM2.5 for short.
PM2.5 concentrations are considered a good stand-in for overall air quality, and are used as a proxy for all wildfire smoke contaminants. The national standard for PM2.5 is 8.8 micrograms per cubic metre (µg/m³); in 2021 the World Health Organization halved its guideline for PM2.5, to 5 µg/m³.
More than 200 stations across the country track PM2.5 concentrations, which are expressed as annual averages (capturing chronic or prolonged exposure) as well as peak concentrations (representing acute exposures). A report published in January by Environment and Climate Change Canada observed no national trend in average concentrations, nor peak concentrations, since 2005.
Regionally, though, there are clear patterns: Southern Ontario, southern Quebec and Atlantic Canada have enjoyed decreasing peak concentrations. The opposite is happening in B.C. and the Prairies, where many cities now have elevated average PM2.5 levels, often above guidelines. (A recent report by the American Lung Association observed similar patterns in the western U.S., and identified wildfires as a “major contributing factor.”)
Dennis Herod, a physical scientist and manager of smog analysis with the federal environment department, said wildfires can send PM2.5 levels through the roof, skewing annual averages.
Ten years ago, fires in the Northwest Territories registered thousands of micrograms per cubic metre, he said. “In 2017, in the interior of British Columbia, levels were up in the hundreds and even the thousands as well.”
Canada’s air quality: Worsening in the West, but still among the best on Earth
Elevated levels of particulate matter (PM2.5) measured in Western Canada are largely attributed to wildfires. One can see the impact in 2019 data from the Canadian Urban Environmental Health Research Consortium (CANUE), which has built a database linking environmental factors to health outcomes. Generally, since the 1990s, air quality has improved in high-income countries, while the reverse is true in middle- and low-income countries, owing to rapid urbanization and economic development. “We have made really good progress on more traditional sources of air pollution” in Canada, said UBC professor Michael Brauer. “It’s not perfect, but if you take out wildfires, we’re one of the cleanest countries in the world.”
Average annual PM2.5 concentration, 2019
Micrograms per cubic metre
1
34
NUNAVUT
YUKON
NWT
9
B.C.
ALTA.
SASK.
6
1
MAN.
5
2
4
3
PM2.5
guidelines
Average annual
concentrations
Canada: 8.8
WHO: 5
7
8
U.S.
1,500 km
Houston: 11
1
Fort McKay: 7
6
Quesnel: 9
2
Regina: 4
7
Vancouver: 5.5
3
Winnipeg: 5.5
8
Yellowknife: 4
9
Calgary: 7.5
4
Edmonton: 8.2
5
16
N.L.
ONT.
QUE.
17
14
11
PEI
N.B.
15
12
N.S.
9
10
13
Sarnia: 7
Charlottetown: 8
9
14
Toronto: 7.6
Halifax: 5
10
15
Ottawa: 6
Labrador City: 2
11
16
Montreal: 7.3
12
St. John’s: 5
17
Moncton: 4
13
Air quality in 20 select world cities, 2019
Average annual PM2.5 concentration
Micrograms per cubic metre (µg/m3)
123.88
Lahore
119.77
Kabul
105
Delhi
86.48
Dhaka
52.09
Hanoi
47.26
Kuwait City
46.88
Dubai
46.35
Jakarta
37.29
Johannesburg
37.04
Beijing
35.76
Kathmandu
28.79
Tehran
25.42
Santiago
25
Seoul
23.14
Bangkok
20.48
Addis Ababa
15.51
Paris
13.74
Berlin
12.96
Rome
12.69
Bogota
Note: Values on coloured map derived from aerosol optical depth data captured by satellites. City data obtained from monitoring stations. The two sources are not necessarily consistent.
matthew mcclearn, john sopinski and murat yükselir/the globe and mail, source: CANUE; world health organization;
Environment and Climate Change Canada
Canada’s air quality: Worsening in the West, but still among the best on Earth
Elevated levels of particulate matter (PM2.5) measured in Western Canada are largely attributed to wildfires. One can see the impact in 2019 data from the Canadian Urban Environmental Health Research Consortium (CANUE), which has built a database linking environmental factors to health outcomes. Generally, since the 1990s, air quality has improved in high-income countries, while the reverse is true in middle- and low-income countries, owing to rapid urbanization and economic development. “We have made really good progress on more traditional sources of air pollution” in Canada, said UBC professor Michael Brauer. “It’s not perfect, but if you take out wildfires, we’re one of the cleanest countries in the world.”
Average annual PM2.5 concentration, 2019
Micrograms per cubic metre
1
34
NUNAVUT
YUKON
NWT
9
B.C.
ALTA.
SASK.
6
1
MAN.
5
2
4
3
PM2.5
guidelines
Average annual
concentrations
Canada: 8.8
WHO: 5
7
8
U.S.
1,500 km
Houston: 11
1
Fort McKay: 7
6
Quesnel: 9
2
Regina: 4
7
Vancouver: 5.5
3
Winnipeg: 5.5
8
Yellowknife: 4
9
Calgary: 7.5
4
Edmonton: 8.2
5
16
N.L.
ONT.
QUE.
17
14
11
PEI
N.B.
15
12
N.S.
9
10
13
Sarnia: 7
Charlottetown: 8
9
14
Toronto: 7.6
Halifax: 5
10
15
Ottawa: 6
Labrador City: 2
11
16
Montreal: 7.3
12
St. John’s: 5
17
Moncton: 4
13
Air quality in 20 select world cities, 2019
Average annual PM2.5 concentration
Micrograms per cubic metre (µg/m3)
123.88
Lahore
119.77
Kabul
105
Delhi
86.48
Dhaka
52.09
Hanoi
47.26
Kuwait City
46.88
Dubai
46.35
Jakarta
37.29
Johannesburg
37.04
Beijing
35.76
Kathmandu
28.79
Tehran
25.42
Santiago
25
Seoul
23.14
Bangkok
20.48
Addis Ababa
15.51
Paris
13.74
Berlin
12.96
Rome
12.69
Bogota
Note: Values on coloured map derived from aerosol optical depth data captured by satellites. City data obtained from monitoring stations. The two sources are not necessarily consistent.
matthew mcclearn, john sopinski and murat yükselir/the globe and mail, source: CANUE; world health organization; Environment and Climate Change Canada
Canada’s air quality: Worsening in the West, but still among the best on Earth
Elevated levels of particulate matter (PM2.5) measured in Western Canada are largely attributed to wildfires. One can see the impact in 2019 data from the Canadian Urban Environmental Health Research Consortium (CANUE), which has built a database linking environmental factors to health outcomes. Generally, since the 1990s, air quality has improved in high-income countries, while the reverse is true in middle- and low-income countries, owing to rapid urbanization and economic development. “We have made really good progress on more traditional sources of air pollution” in Canada, said UBC professor Michael Brauer. “It’s not perfect, but if you take out wildfires, we’re one of the cleanest countries in the world.”
Average annual PM2.5 concentration, 2019
Micrograms per cubic metre
1
34
YUKON
NWT
NUNAVUT
18
Hudson Bay
B.C.
ALTA.
SASK.
6
1
MAN.
16
5
N.L.
ONT.
QUE.
2
17
4
3
PM2.5
guidelines
Average annual
concentrations
Canada: 8.8
WHO: 5
14
7
8
11
PEI
N.B.
U.S.
15
12
N.S.
1,500 km
9
10
13
Houston: 11
Edmonton: 8.2
Sarnia: 7
Moncton: 4
St. John’s: 5
1
5
9
13
17
Quesnel: 9
Fort McKay: 7
Toronto: 7.6
Charlottetown: 8
Yellowknife: 4
2
6
10
14
18
Vancouver: 5.5
Regina: 4
Ottawa: 6
Halifax: 5
3
7
11
15
Calgary: 7.5
Winnipeg: 5.5
Montreal: 7.3
Labrador City: 2
4
8
12
16
Air quality in 20 select world cities, 2019
Average annual PM2.5 concentration Micrograms per cubic metre (µg/m3)
123.88
35.76
Lahore
Kathmandu
119.77
28.79
Kabul
Tehran
105
25.42
Delhi
Santiago
86.48
25
Dhaka
Seoul
52.09
23.14
Hanoi
Bangkok
47.26
20.48
Kuwait City
Addis Ababa
46.88
15.51
Dubai
Paris
46.35
13.74
Jakarta
Berlin
37.29
12.96
Johannesburg
Rome
37.04
12.69
Beijing
Bogota
Note: Values on coloured map derived from aerosol optical depth data captured by satellites. City data obtained from monitoring stations. The two sources are not necessarily consistent.
matthew mcclearn, john sopinski and murat yükselir/the globe and mail, source: CANUE; world health organization; Environment and Climate Change Canada
Canada’s air quality: Worsening in the West, but still among the best on Earth
Elevated levels of particulate matter (PM2.5) measured in Western Canada are largely attributed to wildfires. One can see the impact in 2019 data from the Canadian Urban Environmental Health Research Consortium (CANUE), which has built a database linking environmental factors to health outcomes. Generally, since the 1990s, air quality has improved in high-income countries, while the reverse is true in middle- and low-income countries, owing to rapid urbanization and economic development. “We have made really good progress on more traditional sources of air pollution” in Canada, said UBC professor Michael Brauer. “It’s not perfect, but if you take out wildfires, we’re one of the cleanest countries in the world.”
Average annual PM2.5 concentration, 2019
Micrograms per cubic metre
1
34
YUKON
NWT
NUNAVUT
18
Hudson Bay
B.C.
ALTA.
SASK.
6
1
MAN.
16
5
N.L.
ONT.
QUE.
2
17
4
3
PM2.5
guidelines
Average annual
concentrations
Canada: 8.8
WHO: 5
14
7
8
11
PEI
N.B.
U.S.
15
12
N.S.
1,500 km
9
10
13
Houston: 11
Edmonton: 8.2
Sarnia: 7
Moncton: 4
St. John’s: 5
1
5
9
13
17
Quesnel: 9
Fort McKay: 7
Toronto: 7.6
Charlottetown: 8
Yellowknife: 4
2
6
10
14
18
Vancouver: 5.5
Regina: 4
Ottawa: 6
Halifax: 5
3
7
11
15
Calgary: 7.5
Winnipeg: 5.5
Montreal: 7.3
Labrador City: 2
4
8
12
16
Air quality in 20 select world cities, 2019
Average annual PM2.5 concentration Micrograms per cubic metre (µg/m3)
123.88
35.76
Lahore
Kathmandu
119.77
28.79
Kabul
Tehran
105
25.42
Delhi
Santiago
86.48
25
Dhaka
Seoul
52.09
23.14
Hanoi
Bangkok
47.26
20.48
Kuwait City
Addis Ababa
46.88
15.51
Dubai
Paris
46.35
13.74
Jakarta
Berlin
37.29
12.96
Johannesburg
Rome
37.04
12.69
Beijing
Bogota
Note: Values on coloured map derived from aerosol optical depth data captured by satellites. City data obtained from monitoring stations. The two sources are not necessarily consistent.
matthew mcclearn, john sopinski and murat yükselir/the globe and mail, source: CANUE; world health organization; Environment and Climate Change Canada
Canada’s air quality: Worsening in the West, but still among the best on Earth
Elevated levels of particulate matter (PM2.5) measured in Western Canada are largely attributed to wildfires. One can see the impact in 2019 data from the Canadian Urban Environmental Health Research Consortium (CANUE), which has built a database linking environmental factors to health outcomes. Generally, since the 1990s, air quality has improved in high-income countries, while the reverse is true in middle- and low-income countries, owing to rapid urbanization and economic development. “We have made really good progress on more traditional sources of air pollution” in Canada, said UBC professor Michael Brauer. “It’s not perfect, but if you take out wildfires, we’re one of the cleanest countries in the world.”
Average annual PM2.5 concentration, 2019
Micrograms per cubic metre
1
34
YUKON
NWT
NUNAVUT
18
Hudson Bay
B.C.
ALTA.
SASK.
6
1
MAN.
16
5
N.L.
ONT.
QUE.
2
17
4
3
PM2.5
guidelines
Average annual
concentrations
Canada: 8.8
WHO: 5
14
7
8
11
PEI
N.B.
U.S.
15
12
N.S.
1,500 km
9
10
13
Regina: 4
Moncton: 4
Toronto: 7.6
Labrador City: 2
7
10
13
16
Calgary: 7.5
4
Houston: 11
1
Ottawa: 6
St. John’s: 5
Charlottetown: 8
11
14
17
Winnipeg: 5.5
8
Edmonton: 8.2
5
Quesnel: 9
2
Sarnia: 7
Halifax: 5
Montreal: 7.3
Yellowknife: 4
9
15
18
12
Fort McKay: 7
6
Vancouver: 5.5
3
Air quality in 20 select world cities, 2019
Average annual PM2.5 concentration Micrograms per cubic metre (µg/m3)
123.88
35.76
Lahore
Kathmandu
119.77
28.79
Kabul
Tehran
105
25.42
Delhi
Santiago
86.48
25
Dhaka
Seoul
52.09
23.14
Hanoi
Bangkok
47.26
20.48
Kuwait City
Addis Ababa
46.88
15.51
Dubai
Paris
46.35
13.74
Jakarta
Berlin
37.29
12.96
Johannesburg
Rome
37.04
12.69
Beijing
Bogota
Note: Values on coloured map derived from aerosol optical depth data captured by satellites. City data obtained from monitoring stations. The two sources are not necessarily consistent.
matthew mcclearn, john sopinski and murat yükselir/the globe and mail, source: CANUE; world health organization; Environment and Climate Change Canada
A wildfire can blanket distant cities and towns in smoke that smells not unlike a wood fireplace. The fine particles within can penetrate deep into a person’s lungs and bloodstream. Chronic exposure is known to promote certain diseases and shorten life. The effects of wildfire smoke are worse for children, seniors, people working or exercising outdoors, and people with certain chronic health issues, including lung or heart conditions.
Do the relatively mild differences in average PM2.5 readings between Canadian cities matter? Prof. Brauer said they do. Epidemiological research has shown that modest increases even from the lowest PM2.5 levels lead to increased mortality and other health consequences.
“When levels go up today compared to yesterday, we just see more people dying,” he said. “We’ve known this for air pollution and PM2.5 for decades now, but we now also have really strong evidence for wildfires.
“And we also see that filtering down into other measures of health: more emergency room visits, more hospitalizations.”
Canada’s wildfire outlook is not encouraging, largely owing to climate change: Warm temperatures dry out landscapes, making them more prone to burn. According to the World Resources Institute, which tracks wildfires, boreal forests in high-latitude regions are losing more tree cover, likely because these areas are warming more quickly than other parts of the planet. That’s resulting in more numerous and severe fires, and it’s also extending fire seasons.
Cyclists enjoy a clear day along the Bow River in Calgary.Todd Korol/Todd Korol/The Globe and Mail
A 2016 study of 561 wildfire-prone counties in the western U.S. estimated that, as climate change progresses, by mid-century the average wildfire-specific PM2.5 levels in those areas will increase 160 per cent from levels in the early 2000s. The researchers coined the term ”smoke waves” to describe more than two consecutive days with high levels of PM2.5 caused by wildfires.
“All the climate projections suggest this is going to get worse. Not forever, but we’re looking at a 50-year time frame, if not longer,” Prof. Brauer said.
But while there may be little Canadians can do to reduce wildfire risk in the immediate future, experts say that air quality should not be anyone’s leading health concern. Physical activity, diet, smoking and alcohol consumption all have much greater consequences. And the healthier you are, the less impact wildfire smoke is likely to have.
Trees in the boreal forest near a residential neighbourhood of Fort McMurray recover in 2017 after the wildfires there.ROBYN BECK/AFP/Getty Images
“For the vast majority of people, these events will be reasonably well tolerated,” said Chris Carlsten, a professor at UBC with expertise in respiratory medicine and air pollution.
Many options exist for mitigating the effects of wildfire smoke on health. Environment Canada and Health Canada jointly publish the Air Quality Health Index, which provides simple, up-to-date air quality indicators, along with guidance on when to reduce or avoid outdoor activities. If you must go outdoors into smoke-affected air, the American Lung Association recommends wearing a well-fitting N95 mask. Indoors, some HVAC systems have recirculation settings that can help keep smoke out of homes, and HEPA filters can further improve air quality.
“It’s about knowing your personal health and your experience with past fire events, and to have a plan that builds on that experience when the next one comes,” Prof. Carlsten said.