Population exposure to outdoor air pollutants

Key results

In the most recent reporting period (2019 to 2021), 85% of Canadians lived in areas where outdoor concentrations of air pollutants were within the standard.

• This represents an improvement on the 64% established for the previous period (2018 to 2020), a period largely influenced by the 2018 wildfires in British Columbia (1.36 million hectares burned, the largest area on record for the province) and in the United States that caused standards to be exceeded in Alberta and British Columbia.
• This is not only an improvement on the 63% established for the first period (2005 to 2007) but also the highest proportion recorded since this reference period.^{Footnote 3} 

Percentage of Canadians living in areas where outdoor concentrations of air pollutants were at or below the 2020 Canadian Ambient Air Quality Standards, Canada, 2005 to 2021

Note: Except for the annual standards for nitrogen dioxide and sulphur dioxide, the 2020 Canadian Ambient Air Quality Standards use 3-year average concentrations. For this reason, the bar chart portrays percentage values over 3-year periods. The annual standards for nitrogen dioxide and sulphur dioxide use a single annual concentration for the 3-year reporting period. For example, for the 2019 to 2021 reporting period, the annual concentrations for 2021 were used for the annual standards for nitrogen dioxide and sulphur dioxide.
Source: Environment and Climate Change Canada (2023) Air Quality Research Division. Health Canada (2023) Air Health Effects Assessment Division.

The indicator uses a total of 7 standards^{Footnote 4}   related to 4 air pollutants (fine particulate matter [PM_2.5], ground-level ozone [O₃], nitrogen dioxide [NO₂] and sulphur dioxide [SO₂]). All 7 of these standards must be met for the population of a given area to be counted as within (less than or equal to) the standards.

During the 2019 to 2021 reporting period, Ontario and British Columbia recorded the highest number of standard exceedances, with 14 and 17, respectively. Newfoundland and Labrador, Prince Edward Island, Nova Scotia, Manitoba, the Northwest Territories, Yukon, and Nunavut had no exceedances. These results may be influenced by the number and placement of monitoring stations. For detailed information on geographical areas where exceedances were observed, please refer to Annex A. Over that period, exceedances of the 8-hour O₃ standard affected the largest proportion of the Canadian population, at 13.8%. Of the 14 communities showing exceedances of the O₃ standard, 13 communities are in southern Ontario where air quality is influenced by the flow of air pollutants from the United States.

Long term results by pollutant

• O₃ (8-hour): Between the 2005 to 2007 and 2019 to 2021 reporting periods, this was the most frequently exceeded standard. The proportion of the population living in areas where CAAQS exceedances occurred decreased significantly from 33.5% for the 2005 to 2007 reference period, to 13.8% for the 2019 to 2021 period.^{Footnote 5}   
• PM_2.5 (annual): From the 2005 to 2007 to the 2012 to 2014 reporting periods, the proportion of the population living in areas exceeding the annual standard for PM_2.5 increased steadily from 3.9% to 15.8%. A decrease was then observed down to a proportion of 0.8% for the 2019 to 2021 reporting period. This improvement can be attributed to fewer large cities, having exceedances over the latter reporting periods; for example, no exceedances were recently recorded in Montreal, Calgary, or Hamilton.
• PM_2.5 (24-hour): Between the 2005 to 2007 and 2015 to 2017 reporting periods, there has a been an overall decline in exceedances of the 24-hour standard for PM_2.5. The high proportion of population affected by exceedances in the reporting periods from 2016 to 2018 (12.2%), 2017 to 2019 (11.4%), and 2018 to 2020 (19.7%) can be attributed to the influence of smoke from large wildfires in the western United States and in British Columbia which greatly affected air quality in large communities in Alberta and British Columbia. In the most recent reporting period (2019 to 2021), this proportion fell from 19.7% to 1.0%.
• NO₂ (1-hour and annual): Between the 2005 to 2007 and 2019 to 2021 reporting periods, the proportion of the population living in areas exceeding one of the standards for NO₂ decreased from around 12% to 0.0%. Since the 2013 to 2015 reporting period, there has been only 1 exceedance of the 1-hour standard based on the methodology used in the indicator. This exceedance was in Brandon (Manitoba), which reported an exceedance of the 1-hour standard during the 2018 to 2020 period, affecting 0.14% of the Canadian population.
• SO₂ (1-hour and annual): Exceedances of the standards for SO₂ had minimal influence on the indicator. For the 2019 to 2021 reporting period, exceedance of one of the standards were recorded at 2 monitoring stations in Quebec, 1 station in Ontario, 1 station in Saskatchewan and 1 station in New Brunswick, totalling 0.45% of the Canadian population. These exceedances tend to be limited to areas near SO₂ sources. Despite its low influence on the indicator, SO₂ (specifically the 1-hour standard) remains a concern because of its health impacts on populations and the environment close to sulphur-emitting facilities.

About the indicator

What the indicator measures

This indicator tracks the percentage of the Canadian population living in areas where concentrations of outdoor air pollutants from all sources were less than or equal to the 2020 CAAQS. The indicator uses the following 2020 standards (see Table 1 for more details).

• fine particulate matter (PM_2.5): 24-hour and annual
• ground-level ozone (O₃): 8-hour
• nitrogen dioxide (NO₂): 1-hour and annual
• sulphur dioxide (SO₂): 1-hour and annual

Why this indicator is important

Canadians are exposed to air pollutants on a daily basis and this exposure can result in adverse health effects. Exposure to some air pollutants, even at low levels, has been linked to increased heart and respiratory problems, leading to increased hospitalization, emergency room visits and premature death. The Government of Canada estimates that each year 42 premature deaths per 100 000 Canadians can be linked to air pollution for a total of 15 300 premature deaths per year. The total economic valuation of the health impacts attributable to air pollution in Canada is $120 billion per year (based on 2016 currency).^{Footnote 6} Footnote

Ground-level O₃ and PM_2.5 are key components of smog and two of the most widespread air pollutants. Exposure to O₃ and PM_2.5can cause adverse health effects even at low levels. Exposure to O₃ can cause throat irritation, coughing, shortness of breath and aggravation of existing conditions such as asthma. Over time, exposure to O₃ may lead to development of asthma, reduced lung function and other lung conditions. Exposure to PM_2.5 can lead to onset or development of respiratory and cardiovascular adverse effects, such as asthma attacks, chronic bronchitis, heart attacks and may lead to the development of lung cancer.

Exposure to SO₂ and NO₂ can irritate the lungs, reduce lung function, and aggravate respiratory conditions especially in people with asthma. Long-term exposure to NO₂ may lead to the development of allergies and asthma. PM_2.5, O₃ and NO₂ are all known to cause adverse health effects at low concentrations.

Most CAAQS pollutants (PM_2.5, O₃, and NO₂) are considered to be non-threshold pollutants. This means that adverse health effects occur even at low concentrations.^{Footnote 6}   A larger proportion of the Canadian population meeting the CAAQS is generally associated with lower overall levels of pollution exposure. Nevertheless, this proportion of the population is not considered to be "safe" from the adverse impacts of air pollution, but only at reduced health risk compared to populations exposed to higher concentrations of air pollution.

Besides their direct effects on human health, these pollutants also have adverse environmental impacts. NO₂ contributes to the formation of O₃ and PM_2.5 and has major impacts on acid deposition ("acid rain") and eutrophication (excessive nutrients in a body of water leading to algal blooms and low oxygen that impact the aquatic system). Similarly, SO₂ is also a major contributor to acid deposition and contributes to formation of PM_2.5. PM_2.5 can damage vegetation and structures and contributes to haze and reduced visibility. Ozone can also impact vegetation, decrease the productivity of some crops, and may contribute to forest decline. It can also damage synthetic materials and textiles, cause cracks in rubber, accelerate fading of dyes and speed deterioration of some paints and coatings.

Improved air quality reduces heart attacks, hospital visits, allergy, and child asthma attacks, and prevents lost school and work days. Cleaner air can also reduce damage to crops, forests, surface waters and infrastructure such as buildings and bridges.^{Footnote 7} 

Consult the Air pollution: drivers and impacts web page for information on the impacts of air pollution on human health, the economy and the environment.

Related initiatives

This indicator tracks progress on the 2022 to 2026 Federal Sustainable Development Strategy, supporting the target: Increase the percentage of the population across Canada living in areas where air pollutant concentrations are less than or equal to the Canadian Ambient Air Quality Standards from 60%^{Footnote 8}    in 2005 to 85% in 2030. The most recent data available shows that, between the 2005 to 2007 and the 2019 to 2021 reporting periods, the percentage of Canadians living in areas where outdoor concentrations of air pollutants were less than or equal to the 2020 Canadian Ambient Air Quality Standards increased from 63% to 85%.

In addition, the indicator contributes to the Sustainable Development Goals of the 2030 Agenda for Sustainable Development. It is linked to Goal 11, Sustainable Cities and Communities and Target 11.6, "By 2030, reduce the adverse per capita environmental impact of cities, including by paying special attention to air quality and municipal and other waste management."

Related indicators

The Air health trends indicator provides an overview of the public health impacts attributable to outdoor air pollution in Canada.

The Air quality indicators track ambient concentrations of PM_2.5, O₃, SO₂, NO₂ and VOCs at the national and regional level and at local monitoring stations.

The Human exposure to harmful substances indicators track the concentrations of 4 substances (mercury, lead, cadmium and bisphenol A) in Canadians.

The Air pollutant emissions indicators track emissions from human activities of 6 key air pollutants: sulphur oxides (SO_X), nitrogen oxides (NO_X), volatile organic compounds (VOC), ammonia (NH₃), carbon monoxide (CO) and fine particulate matter (PM_2.5). Black carbon, which is a component of PM_2.5, is also reported. For each air pollutant, data are provided at the national, provincial/territorial and facility level and by major sources.

Data sources and methods

Data sources

The indicator is calculated from air pollutant concentration data and population statistics.

The air pollutant concentration data are taken from Environment and Climate Change Canada's Canada-wide Air Quality Database. The population data were retrieved from Statistics Canada's demographic statistics.

Methods

The indicator is calculated by comparing the spatially averaged pollutant concentration for each geographical area with the respective 2020 Canadian Ambient Air Quality Standards (CAAQS, the standards). The total population of all geographical areas where the average concentrations for all pollutants are less than or equal to the respective standards are compared to the national population.

Caveats and limitations

From 2005 to 2021, approximately 63.5% of the population lived in areas covered by selected air quality monitoring stations that meet the data completeness criteria. Refer to Annex B for a list of geographical areas used in the indicator. The indicator assumes that the remainder of the population lives in areas where outdoor concentrations of ozone, fine particulate matter, sulphur dioxide and nitrogen dioxide are at or below their 2020 standards.^{Footnote 10}

Populations in northern regions of the country have less air quality monitoring coverage, as monitoring stations tend to be situated near urban areas with a higher population density.

Due to unpredictable variability in extreme weather events such as wildfires, results may fluctuate significantly from one reporting period to another.

Resources

References

National Forestry Database (2023) Forest area burned and number of forest fires. Retrieved on September 22, 2023.

Canadian Council of Ministers of the Environment (2012) Guidance document on achievement determination for Canadian Ambient Air Quality Standards for fine particulate matter and ozone (PDF; 264 kB). Retrieved on September 22, 2023.

Canadian Council of Ministers of the Environment (2014) Air Quality Management System. Retrieved on September 22, 2023.

Canadian Council of Ministers of the Environment (2017) State of the Air. Retrieved on September 22, 2023.

Canadian Council of Ministers of the Environment (2019) Guidance document on air zone management (PDF; 225 kB). Retrieved on September 22, 2023.

Canadian Council of Ministers of the Environment (2020) Guidance document on achievement determination for Canadian Ambient Air Quality Standards for nitrogen dioxide (PDF; 616 kB). Retrieved on September 22, 2023.

Canadian Council of Ministers of the Environment (2020) Guidance document on achievement determination for Canadian Ambient Air Quality Standards for sulphur dioxide (PDF; 586 kB). Retrieved on September 22, 2023.

Environment and Climate Change Canada (2020) National Air Pollution Surveillance Program. Retrieved on September 22, 2023.

Government of Canada (2023) Outdoor air pollution and health. Retrieved on September 22, 2023.

Related information

Air pollution: drivers and impacts

Canadian Smog Science Assessment Highlights and Key Messages

Smog: causes and effects

Annex A. Geographical areas used to calculate the indicator

Annex B. Geographical areas with exceedances from the standars for the 2019-2021 reporting period

Annex A. Geographical areas used to calculate the indicator

Annex B. Geographical areas with exceedances from the standards for the 2019-2021 reporting period