National Air Quality Management System

The national Air Quality Management System (AQMS) is a collaborative approach for reducing air pollution in Canada. It consists of several elements:

• Canadian Ambient Air Quality Standards (non-regulatory health and environmental-based air quality objectives intended to drive improvements where needed)
• air zones (management areas delineated within a province or territory)
• regional airsheds - transboundary air pollution (broad geographic areas that encompass a number of air zones and may cross provincial/territorial and international boundaries)
• base-level industrial emissions requirements
• mobile emission sources (transportation)

Canadian Ambient Air Quality Standards

The Canadian Council of Ministers of the Environment have developed Canadian Ambient Air Quality Standards (CAAQS) as a key element of the Air Quality Management System to drive improvement of air quality across Canada. CAAQS are non-regulatory health and environmentally based ambient air objectives that are used to assess general air quality and reflect desirable concentrations of contaminants in air from all sources. CAAQS have been developed for fine particulate matter, ozone, nitrogen dioxide and sulphur dioxide.

Source: Canadian Council of Ministers of the Environment

Air zone management framework

• The air zone management framework (AZMF) is a place-based approach to managing air quality under the AQMS.
• The framework provides guidance on management, monitoring and reporting actions to be implemented in an area to achieve the CAAQS.
• Under the AQMS, each jurisdiction is required to:
  • delineate Air Zones to cover their entire jurisdiction
  • publicly report on monitored levels of the CAAQS pollutants in their Air Zones
  • develop management plans outlining actions to improve air quality in their Air Zones

Air zones – Managing air quality in Ontario

As part of its implementation of the federal Air Quality Management System, Ontario has identified six geographic air zones falling into one of three air zone categories. These air zone designations are based on factors such as pollutant sources, topography, meteorological patterns, population density and other factors that potentially influence ambient air concentrations.

Ontario has designated 27 Air Quality Health Index ambient air monitoring stations located across the province as CAAQS reporting stations for each of the identified air zones in the province. These 27 designated stations report for each of the CAAQS parameters, except for SO₂ which only has 9 CAAQS reporting stations. Designated sites normally refer to communities with populations greater than 100,000 and/or communities with large industrial sources.

CAAQS reporting stations in Ontario air zone categories and areas

This map presents the locations of the designated CAAQS reporting stations within the air zone areas of each air zone category in Ontario

Air zone management levels and objectives

• Four “management levels” provide general guidance on the nature of the management, monitoring and reporting actions to be implemented in an Air Zone.
• The four management levels are identified by specific colours: red, orange, yellow and green, each corresponding to a contaminant concentration range that is specific to each CAAQS.
• Each management level is associated with a suite of actions that become progressively more stringent as air pollution concentrations approach or exceed the CAAQS.
• The air zone management level is determined by the designated CAAQS reporting station(s) with the highest CAAQS metric within the air zone.

The air zone management framework

Progressively more rigorous actions as air pollutant concentrations approach or exceed the CAAQS.

The numeric concentration ranges for each management level for each CAAQS pollutant are presented in the Appendix: Management Levels for CAAQS Pollutants.

Air zone management

Taking action within each air zone area to reduce emissions, provide information on air quality conditions and report publicly on these actions is an important part of the air management framework. Ontario’s approach to air zone management is to combine a province-wide framework of regulations and programs to protect air quality across Ontario with enhanced activities within specific air zone areas as appropriate.

An inventory of the actions Ontario was taking in 2021 to improve and maintain the air quality across Ontario is presented in the Appendix: Air Quality Management Actions by Air Zone Area. This inventory provides an overview of measures likely to have an impact on the four CAAQS pollutants (PM_2.5, ozone, NO₂ and SO₂), or their precursors.

This inventory is organized into three sections: (i) Ontario air quality management actions across all air zone areas which describes province-wide initiatives; (ii) Air zone area-specific actions, including regulations, policies, industrial site-specific standards and technical standards; and (iii) Changes that occurred between 2021 and the publication of this report.

Information about Ontario’s air zone management planning are presented in the Appendix: Ontario Air Quality Management Actions by Air Zone, Ontario Air Quality Management Actions Across All Air Zones, and Changes in Air Quality Management Actions since 2021.

Canadian Ambient Air Quality Standard achievement

10-year trends – Fine particulate matter

10-year trend of 24-hour PM_2.5 CAAQS metrics in Ontario

This is a line graph showing the trend of the 24-hour fine particulate matter Canadian Ambient Air Quality Standard metrics from 2012 to 2021 in Ontario. This trend shows Ontario’s decrease of 17% over this 10-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

• The Ontario 10-year trend is based on data from 26 ambient air monitoring stations.
• The CAAQS for 24h PM_2.5 (27 µg/m³) is based on the 98^th percentile measurement annually, averaged over three consecutive years.
• Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as forest fires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

10-year trend of annual PM_2.5 CAAQS metrics in Ontario

This is a line graph showing the trend of the annual fine particulate matter Canadian Ambient Air Quality Standard metrics from 2012 to 2021 in Ontario. This trend shows Ontario’s decrease of 18% over this 10-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

• The Ontario 10-year trend is based on data from 26 ambient air monitoring stations.
• The CAAQS for annual PM_2.5 (8.8 µg/m³) is based on the annual mean averaged over three consecutive years.
• Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as forest fires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

The 10-year trends, based on the 24-hour and annual PM_2.5 CAAQS metrics at each of the designated monitoring sites, are presented in the Appendix: PM_2.5 and ozone CAAQS metric trends for designated sites across Ontario (2012-2021).

2021 results – Fine particulate matter

Summary of PM_2.5 CAAQS metrics for 2021

Averaging time	Range in CAAQS metrics Low	Range in CAAQS metrics High	Number of sites with CAAQS exceedances
PM2.5 24-hour	14 µg/m3 at Sault Ste. Marie	21 µg/m3 at Hamilton Downtown and Toronto Downtown	0
PM2.5 annual	5.0 µg/m3 at Sault Ste. Marie	8.6 µg/m3 at Hamilton Downtown	0

A summary of the 2021 CAAQS metric values for the 24-hour and annual PM_2.5 at individual CAAQS reporting stations is in the Appendix: PM_2.5 and ozone CAAQS metric values for designated sites across Ontario (2021).

PM_2.5 CAAQS management levels for air zones across Ontario, 2021

The PM_2.5 CAAQS metrics associated with the management levels are presented in the Appendix: Management levels for PM_2.5.

10-year trends – Ground-level ozone

10-year trend of 8-hour O₃ CAAQS metrics in Ontario

This is a line graph showing the trend of the 8-hour ozone Canadian Ambient Air Quality Standard metrics from 2012 to 2021 in Ontario. This trend shows Ontario’s decrease of 10% over this 10-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

• The Ontario 10-year trend is based on data from 26 ambient air monitoring stations.
• The CAAQS for ozone (62 ppb) is based on the consecutive three-year average of the annual 4^th highest daily maximum eight-hour running average.
• Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as forest fires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

The 10-year trends, based on the 8-hour ozone CAAQS metrics at each of the designated monitoring sites, are presented in the Appendix: PM_2.5 and ozone CAAQS metric trends for designated sites across Ontario (2012-2021).

2021 results – Ground-level ozone

Summary of ozone CAAQS metrics for 2021

Averaging time	Low range	High range	Number of sites with CAAQS exceedances
Ozone 8-hour	51 ppb at Thunder Bay	70 ppb at Sarnia	15

Transboundary influences, from both the U.S. and beyond, account for a significant portion of Ontario’s ozone when their levels are elevated. Ontario’s CAAQS reporting stations would have met the ozone CAAQS if transboundary flow days were excluded from the calculated metric using a weight of evidence (WOE) analysis.

A summary of the 2021 CAAQS metric values for 8-hour ozone at individual CAAQS reporting stations is in the Appendix: PM_2.5 and ozone CAAQS metric values for designated sites across Ontario (2021).

Ozone CAAQS effective management levels for air zones across Ontario, 2021

The ozone CAAQS metrics associated with the management levels are presented in the Appendix: Management levels for ozone.

Weight of Evidence analysis

Transboundary influences, from both the U.S. and beyond, account for a significant portion of Ontario’s ozone when levels are elevated. A Weight of Evidence (WOE) analysis demonstrates the influence of transboundary flow on days with elevated ozone concentrations and confirms that Ontario’s CAAQS reporting stations would have met the ozone CAAQS if transboundary flow days were excluded from the calculated metric.

The WOE approach consists of performing, evaluating, and documenting a series of technical analyses that collectively support the conclusion that exceedances of the CAAQS on a given day were influenced by transboundary flows or exceptional events. These analyses may include assessing the meteorological conditions (airflow, wind speed and direction, temperature, stability, etc.) and pollutant concentrations in Ontario and upwind locations.

10-year trends – Nitrogen dioxide

10-year trend of 1-hour NO₂ CAAQS metrics in Ontario

This is a line graph showing the trend of the 1-hour nitrogen dioxide Canadian Ambient Air Quality Standard metrics from 2012 to 2021 in Ontario. This trend shows Ontario’s decrease of 10% over this 10-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

• The Ontario 10-year trend is based on data from 25 ambient air monitoring stations.
• The CAAQS for 1-hour NO₂ (60 ppb) is based on the 98^th percentile of the daily maximum 1-hour average concentrations, averaged over three consecutive years.
• Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as forest fires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

10-year trend of annual NO₂ CAAQS metrics in Ontario

This is a line graph showing the trend of the annual nitrogen dioxide Canadian Ambient Air Quality Standard metrics from 2012 to 2021 in Ontario. This trend shows Ontario’s decrease of 25% over this 10-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

• The Ontario 10-year trend is based on data from 26 ambient air monitoring stations.
• The CAAQS for annual NO₂ (17 ppb) is based on the average over a single calendar year of all 1-hour average NO₂ concentrations.

The 10-year trends, based on the 1-hour and annual NO₂ CAAQSmetrics at each of the designated monitoring sites, are presented in Appendix: NO₂ and SO₂ CAAQS Metric Trends for Designated Sites Across Ontario (2012-2021).

2021 results – Nitrogen Dioxide

Summary of NO₂ CAAQS metrics for 2021

Averaging time	Range in CAAQS metrics Low	Range in CAAQS metrics High	Number of sites with CAAQS exceedances
NO2 1-hour	22 ppb at Oshawa	51 ppb at Toronto Downtown	0
NO2 annual	3.3 ppb at Oshawa	12.9 ppb at Toronto West	0

A summary of the 2021 CAAQS metric values for the 1-hour and annual NO₂ at individual CAAQS reporting stations is in the Appendix: NO₂ and SO₂ CAAQS Metric Values for Designated Sites Across Ontario (2021).

NO₂ CAAQS management levels for air zones across Ontario, 2021

The NO₂ CAAQS metrics associated with the management levels are presented in the Appendix: Management levels for NO₂.

10-year trends – Sulphur dioxide

10-year trend of 1-hour SO₂ CAAQS metrics in Ontario

This is a line graph showing the trend of the 1-hour sulphur dioxide Canadian Ambient Air Quality Standard metrics from 2012 to 2021 in Ontario. This trend shows Ontario’s decrease of 37% over this 10-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

• The Ontario 10-year trend is based on data from 8 ambient air monitoring stations.
• The CAAQS for 1-hour SO₂ (70 ppb) is based on the annual 99^th percentile of the SO₂ daily maximum 1-hour average concentrations, averaged over three consecutive years.
• Air quality in Ontario can vary from year to year due to a variety of factors including pollutant emissions, weather, natural events such as forest fires, and the long-range transport of air pollutants from the United States and elsewhere. Long term trends are thus a better reflection of any improvements or a deterioration in air quality over time versus year over year changes.

10-year trend of annual SO₂ CAAQS metrics in Ontario

This is a line graph showing the trend of the annual sulphur dioxide Canadian Ambient Air Quality Standard metrics from 2012 to 2021 in Ontario. This trend shows Ontario’s decrease of 43% over this 10-year period. To view the data for a specific location, please select the 'Stations' radio button and use the drop-down menu.

Note:

• The Ontario 10-year trend is based on data from 8 ambient air monitoring stations.
• The CAAQS for annual SO₂ (5.0 ppb) is based on the average over a single calendar year of all 1-hour average SO₂ concentrations.

The 10-year trends, based on the 1-hour and annual SO₂ CAAQS metrics at each of the designated monitoring sites, are presented in Appendix: NO₂ and SO₂ CAAQS Metric Trends for Designated Sites Across Ontario (2012-2021).

2021 results – Sulphur dioxide

Summary of SO₂ CAAQS metrics for 2021

Averaging time	Range in CAAQS metrics Low	Range in CAAQS metrics High	Number of sites with CAAQS exceedances
SO2 1-hour	2 ppb at Ottawa Downtown	82 ppb at Hamilton Downtown	1
SO2 annual	0.2 ppb at Toronto West, Toronto North and Ottawa Downtown	3.8 ppb at Hamilton Downtown	0

A summary of the 2021 CAAQS metric values for the 1-hour and annual  SO₂ at individual CAAQS reporting stations is in the Appendix: NO₂ and SO₂ CAAQS Metric Values for Designated Sites Across Ontario (2021).

SO₂ CAAQS management levels for air zones across Ontario, 2021

The SO₂ CAAQS metrics associated with the management levels are presented in the Appendix: Management levels for SO₂.