Outdoor air pollution, even at low levels, can have a substantial impact on human health, such as causing respiratory illnesses, increasing emergency department visits and hospitalizations, and resulting in premature deaths.1 In Canada, it has been estimated that 14,600 premature deaths occur each year due to air pollution.2
Between 2015 and 2018, there were no days in London where the air quality health index (AQHI) rating was high or very high risk, suggesting that outdoor air quality did not routinely pose a high risk to human health in the four-year time period. In the 10 years between 2008 and 2017, the annual average concentrations of fine particulate matter (PM2.5) and nitrogen dioxide (NO2) in London both decreased, while ground-level ozone (O3) concentrations fluctuated and generally increased.
|Air Quality Health Index||Nitrogen dioxide|
|Fine particulate matter||Ground-level ozone|
View more information about health effects of air pollution
Between 2015 and 2018, there were no days in London where the Air Quality Health Index (AQHI) was classified as high or very high. There were two occasions across the four-year time period, both in 2016, when the AQHI was rated as high risk for one to two hours, resulting in Special Air Quality Statements (SAQS) being issued for London and the surrounding area. There were no Smog and Air Health Advisories (SAHA) issued for the London region between 2015 and 2018 (data not shown).
Outdoor air quality in the London region, as measured by the AQHI, did not routinely pose a high risk to human health between 2015 and 2018.
Since 2015, the Air Quality Health Index (AQHI) has been used in Ontario to assess the quality of outdoor air and potential impacts on human health. The concentrations of three pollutants are used as indicators for outdoor air quality and are considered as part of the AQHI calculation: fine particulate matter, ground-level ozone, and nitrogen dioxide.
The AQHI scale ranges from one to 10. The higher the AQHI rating, the greater the likelihood of health impacts, with ratings of seven or higher classified as high or very high risk.3 When a high or very high risk AQHI exists, at risk individuals, such as those with heart or lung disease, are encouraged to reduce or avoid outdoor activities. Individuals in the general population are also encouraged to moderate or reschedule activities outdoors when the AQHI is rated very high risk.3
View more information about fine particulate matter.
Fine particulate matter is one of three air pollutants considered as part of the AQHI calculation. Between 2008 and 2017, the annual average concentration of fine particulate matter in London fluctuated between 7.0 and 9.1 µg/m3. Since 2013, the annual average concentration of fine particulate matter consistently decreased each year (Figure 14.1.1).
In 2013, the Canadian government established Canadian Ambient Air Quality Standards (CAAQS) for several air pollutants, including fine particulate matter. Between 2011–2013 and 2015–2017, the three-year annual average concentration of fine particulate matter in London was lower than the 2020 CAAQS target of 8.8 µg/m3 (Figure 14.1.2).
Not only has the annual average concentration of fine particulate matter in London consistently decreased between 2013 and 2017, the three-year annual average concentration observed locally was lower than the Canadian 2020 target for fine particulate matter.
Fine particulate matter consists of particles in the air that are smaller than 2.5 µg in diameter. They are a concern for human health because they are small enough to penetrate deep into the respiratory system and damage lung tissue. 2017 estimates for Ontario suggested that the majority of fine particulate matter emissions were due to residential fuel combustion (56%), followed by industrial processes (18%) and the transportation sector (13%).4
View more information about nitrogen dioxide.
Nitrogen dioxide (NO2) concentration is a factor in the calculation of AQHI. In London, the annual average concentration of nitrogen dioxide in outdoor air decreased, from 10.8 parts per billion (ppb) in 2008 to 5.8 ppb in 2017 (Figure 14.1.3).
The annual average concentration of nitrogen dioxide in London decreased in the 10-year period between 2008 and 2017.
Nitrogen dioxide in the air is often associated with combustion-related pollution, such as from traffic emissions and industry. Nitrogen dioxide contributes to the production of both fine particulate matter and ground-level ozone in the environment, both of which are components in the production of smog. In terms of effects on human health, nitrogen dioxide can contribute to lung irritation and infections.
View more information about ozone.
Ground-level ozone (O3) concentration is an outdoor air pollutant included in the AQHI calculation. Between 2008 and 2017, the annual average concentration of ground-level ozone in London fluctuated between 25.1 ppb and 28.7 ppb. In general, the annual average concentration increased across the 10-year time period (Figure 14.1.4).
The annual average concentration of ground-level ozone in London generally increased between 2008 and 2017. This is in contrast to fine particulate matter and nitrogen dioxide, which both decreased during the same time period.
Ground-level ozone is a major component of smog. Similar to other outdoor air pollutants, ground-level ozone can lead to breathing problems, as well eye irritation. Ontario estimates from 2017 indicated that transportation was a major contributor (28%) to the precursors for ground-level ozone (volatile organic compounds, VOC), as well as commercial and consumer solvent use (29%).5
Southwestern Ontario, including the London region, experiences air pollution from both local and transboundary sources. Ontario has a network of 39 air pollutant monitoring stations across the province, and one of these stations is located in London. Data collected at the London monitoring station is the basis of the air quality data reported in this topic.
Each monitoring station measures the concentration of outdoor air pollutants on an hourly basis. These readings can be summarized into an annual average concentration, which is an indicator of sustained levels of air pollutants to which the community is exposed on an ongoing basis, versus shorter-term events. This type of daily exposure is a contributor to long-term chronic respiratory illnesses in the population.
From 2008 to 2012, fine particulate matter concentration was measured using Tapered Element Oscillating Microbalance (TEOM). In 2013, the method changed to Synchronized Hybrid Ambient Real-time Particulate (SHARP). A correction factor was applied to fine particulate matter concentration measurements from 2008 to 2012 to approximate SHARP methods, so that data was comparable across the entire 10-year time period from 2008 to 2017.
Ontario Public Health Standards: Requirements for Programs, Services, and Accountability – Healthy Environments (pages 33–35)
Healthy Environments and Climate Change Guideline
Population Health Assessment and Surveillance Protocol, 2018
1. Government of Canada [Internet]. Ottawa (ON): Government of Canada; [modified 2019 Nov 4]. Health effects of air pollution; [modified 2019 Aug 6; cited 2019 Nov 4]; [about 8 screens]. Available from: https://www.canada.ca/en/health-canada/services/air-quality/health-effects-indoor-air-pollution.html
2. Health Canada. Health impacts of air pollution in Canada: estimates of morbidity and premature mortality outcomes, 2019 report [Internet]. Ottawa (ON): Health Canada; 2019 Jun [cited 2019 Nov 4]. 38 p. Available from: http://publications.gc.ca/site/eng/9.874080/publication.html
3. Air Quality Ontario [Internet]. Toronto (ON): Queen’s Printer for Ontario; c2010. What is the air quality health index?; c2010 [cited 2019 Sep 30]; [about 2 screens]. Available from: http://www.airqualityontario.com/science/aqhi_description.php
4. Ontario Ministry of the Environment, Conservation and Parks. Air quality in Ontario 2017 report [Internet]. Toronto (ON): Queen’s Printer for Ontario; 2017. Fine particulate matter; [updated 2019 Jun 19; cited 2019 Oct 29]; [about 4 screens]. Available from: https://www.ontario.ca/document/air-quality-ontario-2017-report/fine-par...
5. Ontario Ministry of the Environment, Conservation and Parks. Air quality in Ontario 2017 report [Internet]. Toronto (ON): Queen’s Printer for Ontario; 2017. Ground-level ozone; [updated 2019 Jun 19; cited 2019 Nov 13]; [about 3 screens]. Available from: https://www.ontario.ca/document/air-quality-ontario-2017-report/ground-l...
Last modified on: November 19, 2019
Air Quality Health Index (AQHI)
Since 2015, the Air Quality Health Index (AQHI) has been used in Ontario to assess the quality of outdoor air and potential impacts on human health. This index is calculated based on three air pollutants: fine particulate matter, nitrogen dioxide, and ground-level ozone. The AQHI scale is from one to 10; the higher the AQHI rating, greater is the likelihood of health impacts.
Fine particulate matter (PM2.5)
Particulate matter in the air is a “mixture of microscopic solid particles and liquid droplets suspended in air”.4 It may contain a variety of substances, including harmful aerosols, dust, smoke, and fumes. Particles of this nature that are smaller than 2.5 µg in diameter are classified as fine particulate matter (PM2.5) and are a concern for human health because they can penetrate deep into the respiratory system and damage lung tissue.
Nitrogen dioxide (NO2)
Ambient nitrogen dioxide (NO2) is derived from oxidized nitrogen oxide (NO) and is generally a marker of combustion related air pollution, including power and chemical plants and traffic emissions. Adverse health effects may come fromNO2 itself or its many secondary reaction products including ozone (O3).
Ozone (O3) is created when nitrogen oxides and volatile organic compounds combine in the presence of sunlight. High ozone occurs primarily in the summer, though over time levels of ozone are also increasing in the winter in Southern Ontario. Ozone is associated with adverse effects on respiratory symptoms and lung function.
Smog is made up of predominantly ground-level ozone and fine particulate matter. Ozone has an impact on smog levels primarily in summer whereas fine particulate matter elevates smog levels all year.
Special Air Quality Statement (SAQS)
A Special Air Quality Statement (SAQS) is issued when a high or very high risk AQHI rating is expected for one to two hours on a given day.
Smog and Air Health Advisory (SAHA)
A Smog and Air Health Advisory (SAHA) is issued when a high or very high risk AQHI rating is expected for three or more hours on a given day.