Population exposure to outdoor air pollutants

Key results

• In the most recent reporting period (2021 to 2023), 74% of the Canadian population lived in areas where outdoor concentrations of air pollutants were less than or equal to the standards
  • This result is the same as for the previous reporting period (2020 to 2022)
  • This result is largely due to ground-level ozone standard exceedances in southern Ontario, and to the widespread impact of the 2022 and 2023 wildfires that caused fine particulate matter standards to be exceeded, particularly in the Prairies and British Columbia^{Footnote 4} 

Percentage of the Canadian population living in areas where outdoor concentrations of air pollutants were less than or equal to the 2020 Canadian Ambient Air Quality Standards, Canada, 2005 to 2023

How this indicator was calculated

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. For nitrogen dioxide and sulphur dioxide, the annual standard is calculated using concentrations from the latest year of the reporting period. For example, the 2023 annual concentrations were used for the 2021 to 2023 reporting period.
Source: Environment and Climate Change Canada (2025) Air Quality Research Division. Health Canada (2025) Air Quality Risk Assessment Division.

The indicator uses a total of 7 standards^{Footnote 5}  related to 4 air pollutants (fine particulate matter, ground-level ozone, nitrogen dioxide, and sulphur dioxide). All 7 of these standards must be met in a given geographical area to be considered to have air pollutant concentrations that are less than or equal to the standards.

During the 2021 to 2023 reporting period, a total of 66 communities experienced exceedances of one or more standards. British Columbia, Alberta, and Ontario recorded the highest number of communities with exceedances, at 17, 16 and 15 communities, respectively. Prince Edward Island, Nova Scotia, Yukon and Nunavut had no communities with exceedances of the standards. These provincial and territorial differences may be influenced by the number and placement of monitoring stations.^{Footnote 6}  For detailed information on geographical areas where exceedances were observed, please refer to Annex B.

Over the 2021 to 2023 reporting period, exceedances of the 8-hour ozone standard affected the largest percentage of the Canadian population, at 15%. Of the 19 communities exceeding the ozone standard, 15 are in southern Ontario, where air quality is influenced by the flow of air pollutants from the United States as well as local and regional emissions from transportation and industrial sources.

Despite the unprecedented impacts of the 2023 wildfires across the country, the proportion of the population living in areas exceeding the standards for the 2021 to 2023 reporting period remained unchanged at 74% compared to the 2020 to 2022 reporting period. Although a higher number of communities were affected (66 in this period compared to 43 in the previous period), this was offset by populous urban areas such as Toronto (Ontario), as well as in cities such as Oshawa (Ontario) and Abbotsford (British Columbia) that did not exceed the 2020 CAAQS. Consequently, the proportion of the population impacted by the exceedances remained unchanged.

Long term results by pollutant

• Ground-level ozone (8-hour): Between the 2005 to 2007 and 2021 to 2023 reporting periods, exceedances of the 8-hour ozone standard affected the largest proportion of the population in most reporting years. However, the proportion of the population living in areas with CAAQS exceedances decreased significantly from 34% for the 2005 to 2007 reference period to 15% for the 2021 to 2023 period.^{Footnote 7} 
• Fine particulate matter – PM_2.5 (annual): The proportion of the population living in areas with CAAQS exceedances for annual PM_2.5 has fluctuated over time, with lower proportions between 2014-2016 and 2020-2022. For the 2021 to 2023 reporting period the proportion increased, with 14% of the population living in areas exceeding the 2020 standards, largely due to the significant influence of wildfire smoke on air quality. Exceedances during this period were recorded in major urban centres such as Hamilton and Windsor (Ontario), Regina (Saskatchewan), Edmonton and Calgary (Alberta), and Kelowna (British Columbia).
• Fine particulate matter – PM_2.5 (24-hour): Throughout the reporting periods, the proportion of exceedances of the 24-hour standard for PM_2.5 varied. The high proportion of population affected by exceedances in the reporting periods from 2016 to 2018 (13%), 2017 to 2019 (12%), and 2018 to 2020 (20%) can be attributed to the influence of smoke from large wildfires in the western United States and in northern and western Canada. The proportion of population affected by exceedances was 15% in the 2021 to 2023 period, largely due to the severe 2023 wildfire period, which affected large areas of the country. The impacts of the wildfire smoke on communities such as Regina (Saskatchewan), Calgary, Edmonton and Red Deer (Alberta), and Winnipeg (Manitoba) played a significant role in the increase in the percentage between the periods.
• Nitrogen dioxide – NO₂ (1-hour and annual): Between the 2005 to 2007 and 2021 to 2023 reporting periods, the proportion of the population living in areas exceeding one of the standards for NO₂ decreased from 13% to 0%.
• Sulphur dioxide – SO₂ (1-hour and annual): Between the 2005 to 2007 and 2021 to 2023 reporting periods, exceedances of the standards for SO₂ had minimal influence on the indicator. For the 2021 to 2023 reporting period, exceedances of the 1-hour standard were recorded for 2 communities each in Quebec and New Brunswick, and 1 community each in Ontario, Saskatchewan and British Columbia; these exceedances amounted to 0.3% of the Canadian population. An exceedance of the annual standard was also recorded in 1 community in Quebec. Despite a comparatively low influence on the overall indicator, exceedances of SO₂ standards (specifically the 1-hour standard) remains a concern in some communities near SO₂-emitting facilities because of the potential negative impacts of the pollutant on the environment and on human health.

Percentage of the Canadian population living in areas where outdoor concentrations of air pollutants were exceeding the 2020 Canadian Ambient Air Quality Standards by pollutant, Canada, 2005 to 2023

How this indicator was calculated

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 chart portrays percentage values over 3-year periods. For nitrogen dioxide and sulphur dioxide, the annual standard is calculated using concentrations from the latest year of the reporting period. For example, the 2023 annual concentrations were used for the 2021 to 2023 reporting period.

Source: Environment and Climate Change Canada (2025) Air Quality Research Division. Health Canada (2025) Air Quality Risk Assessment Division.

The population can be exposed to concentrations exceeding the 2020 CAAQS for multiple air pollutants at the same time. Of the 66 communities experiencing CAAQS exceedances in the 2021 to 2023 reporting period, 31 exceeded more than 1 standard. These communities were located in Northwest Territories (1), Quebec (2), Ontario (2), Saskatchewan (5), Alberta (10), and British Columbia (11). Therefore, summing up the percentages of population for all pollutants for a given reporting period may differ from the results provided in the first figure.

About the indicator

What the indicator measures

This indicator tracks the percentage of the population living in Canadian regions where concentrations of outdoor air pollutants from all sources were less than or equal to the 2020 Canadian Ambient Air Quality Standards (CAAQS, the standards).^{Footnote 3}  The indicator uses the following 2020 CAAQS (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

Human health impacts

Canadians are exposed to air pollutants on a daily basis, and this exposure is associated with acute and chronic adverse health effects. Exposure to some air pollutants, even at low levels, has been linked to increased heart and respiratory problems, leading to more hospitalizations, emergency room visits, and premature deaths. The Government of Canada estimates that, in 2018, air pollution was responsible for 47 premature deaths per 100,000 Canadians, with a total of 17,400 premature deaths per year.^{Footnote 8}

Most CAAQS pollutants (PM_2.5, ozone, and NO₂) are considered to be non-threshold pollutants. This means that they have no known safe levels of exposure and can cause adverse health effects even at low concentrations.^{Footnote 8}  As such, while the larger proportion of the Canadian population meeting the CAAQS is expected to experience lower health risks compared with populations exposed to higher concentrations, some level of risk still remains. Health risk increases incrementally with exposure, even at low levels, and may also be influenced by other factors such as underlying health conditions. 

Exposure to PM_2.5 can negatively impact the heart and lungs and can lead to health issues such as asthma symptoms, chronic bronchitis, heart disease, and may contribute to the development of lung cancer.

Exposure to ozone can cause throat irritation, coughing, shortness of breath, and reduced lung function and can aggravate existing conditions such as asthma. Over time, exposure to ozone may lead to development of asthma, reduced lung function, and other lung conditions.

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 contribute to the development of allergies and asthma.

Improved air quality reduces rates of cardiac events in adults, allergies, and asthma exacerbation in children, thus reducing hospital visits and loss of school and work days.^{Footnote 8}

Environmental impacts

All of the CAAQS pollutants also have adverse environmental impacts. NO₂ contributes to the formation of ground-level ozone and PM_2.5. NO₂ also contributes to acid deposition ("acid rain") and eutrophication (excessive nutrients in a body of water leading to algal blooms and low oxygen that impact the water habitat). Similarly, SO₂ is a major contributor to acid deposition and contributes to the formation of PM_2.5 and smog. Direct exposure to SO₂ can also harm plants, potentially decreasing their growth and yields. Ground-level ozone and PM_2.5 are key components of smog, which can also contribute to reduced visibility. When deposited into the environment, PM_2.5 can also damage vegetation and human-made structures. Ground-level 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.

Economic impacts

Air pollution also has significant impacts on the economy. Health Canada estimates that the total economic cost of exposure to air pollution in Canada in 2018 was $146 billion (based on 2020 currency) when all health impacts were combined.^{Footnote 8}  Globally, it was estimated that the cost of PM_2.5 ambient air pollution on health is $6.43 trillion, equivalent to 4.8 percent of global gross domestic product.^{Footnote 9}  This was due to effects such as strain on the healthcare system, decreases in productivity (for example, from lost work days), as well as pollution damages in key economic sectors. Poor air quality also has economic consequences for agriculture and forests. For example, the impacts of ozone on agriculture costs Canadian farmers millions of dollars in lost production each year. Reduced visibility due to air pollution also impacts well-being and the associated socio-economic cost was estimated to be $438 million in 2015.^{Footnote 10}

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 11}  in 2005 to 85% in 2030". The most recent data available shows that, between the baseline reporting period (2005 to 2007) and the current reporting period (2021 to 2023), 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 74%.

In addition, the indicator contributes to the Sustainable Development Goals of the 2030 Agenda for Sustainable Development. It is linked to Goal 3, Good Health and Well-being and Target 3.9, "By 2030, substantially reduce the number of deaths and illnesses from hazardous chemicals and air, water and soil pollution and contamination" and 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 change in health risk over time associated with short-term exposure to air pollution in Canada.

The Air quality indicators track ambient concentrations of PM_2.5, O₃, SO₂, NO₂, and volatile organic compounds (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 (VOCs), 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 data on concentrations of air pollutants and population statistics.

The air pollutant concentration data were 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 average 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. For geographical areas where there is no monitoring station, it is assumed that the concentrations are less than or equal to the 2020 standards.

Caveats and limitations

From 2021 to 2023, approximately 65% of the population lived in areas covered by selected air quality monitoring stations that meet the data completeness criteria. This percentage has remained relatively stable, increasing from approximately 60% to 65% of the population over the reporting period of 2005 to 2023. Refer to Annex A for a list of geographical areas used in the calculation of 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 less than or equal to their 2020 standards. This assumption results in an overestimation of populations being exposed to concentration below the 2020 standards. Furthermore, ground-level ozone concentrations are generally higher outside urban cores, where there may not be NAPS monitoring. For example, for a region such as Southwestern Ontario, it is likely that the entire region would be above the 2020 standards for ozone. Note that for SO₂, there is less coverage, with only 7 to 8% of the population living in areas within 2 km of a station monitoring SO₂ concentrations. The rest of the Canadian population was assumed to be exposed to SO₂ concentrations below the CAAQS.

Populations in rural and northern regions of the country have relatively less coverage, as monitoring stations tend to be situated near urban areas with high population density. This difference in spatial coverage is becoming increasingly important to consider with smoke affecting rural and northern communities in recent wildfire seasons. As these areas are typically not densely populated, the impact on the percentage of population experiencing exceedances may be small; however, the impacts on affected communities could be significant.

Each annual update includes one additional year of air pollution data, and the indicator presents the calculated result for the most recent 3-year period. Previous results are not recalculated and therefore do not capture any subsequent updates to historical data.

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

Resources

References

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 November 4, 2025.

Canadian Council of Ministers of the Environment (2014) Air Quality Management System. Retrieved on November 4, 2025.

Canadian Council of Ministers of the Environment (2019) Guidance document on air zone management (PDF; 225 kB). Retrieved on November 4, 2025.

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 November 4, 2025.

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 November 4, 2025.

Canadian Council of Ministers of the Environment (2025) State of the Air. Retrieved on November 4, 2025.

Environment and Climate Change Canada (2020) National Air Pollution Surveillance Program. Retrieved on November 4, 2025.

Government of Canada (2023) Outdoor air pollution and health. Retrieved on November 4, 2025.

Health Canada (2016) Human health risk assessment for ambient nitrogen dioxide. Retrieved on November 4, 2025.

Health Canada (2016) Human health risk assessment for sulphur dioxide : analysis of ambient exposure to and health effects of sulphur dioxide in the Canadian population. Retrieved on November 4, 2025.

Health Canada (2022) Canadian health science assessment for fine particulate matter (PM_2.5). Retrieved on November 4, 2025.

Related information

Canadian Smog Science Assessment Highlights and Key Messages

Smog: causes and effects

Alternative format

Download the alternative format of the Population exposure to outdoor air pollutants indicator (PDF; 800 kB).

Annex A. Geographical areas used to calculate the indicator

Annex B. Geographical areas with exceedances from the standars for the 2020-2023 reporting period

Annex A. Geographical areas used to calculate the indicator

Annex B. Geographical areas with exceedances from the standards for the 2020-2022 reporting period