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 zone management framework: management approach based on air zones delineated within a province or territory.
• regional airsheds: six regional airsheds cover all of Canada and allow for coordination and joint action in resolving issues across provincial/territorial boundaries and international borders.
• base-level industrial emissions requirements: intended to ensure that all significant industrial sources in Canada, regardless of where facilities are located, meet base-level performance standards.
• addressing mobile emission sources: builds on the existing range of federal, provincial and territorial initiatives aimed at reducing emissions from the transportation sector.

Canadian Ambient Air Quality Standards

The Canadian Council of Ministers of the Environment developed Canadian Ambient Air Quality Standards (CAAQS) as a key element of the national Air Quality Management System to drive improvement of air quality across Canada. CAAQS are non-regulatory 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 national AQMS.
• The framework provides guidance on management, monitoring and reporting actions to be implemented in an area to achieve the CAAQS as well as drive continuous improvements.
• 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
  • identify management actions to improve air quality in their air zones

Air zones – Managing air quality in Ontario

As part of its implementation of the national AQMS, 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 AQHI ambient air monitoring stations located across all of the province’s air zones as CAAQS reporting stations. 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 emission 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 state of air quality in each air zone relative to the CAAQS.
• 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 recommended 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 are recommended 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 zone 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 2023 to improve and maintain 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 in effect in 2023, which describes province-wide initiatives; (ii) Air zone area-specific actions in effect in 2023, including regulations, policies, industrial site-specific standards and technical standards; and (iii) Changes that occurred between 2023 and the publication of this report.

Information about Ontario’s air zone management planning is 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 2023.

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 2014 to 2023 in Ontario. There was no trend detected for Ontario 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 wildfires, 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 2014 to 2023 in Ontario. This trend shows a 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 annual PM_2.5 (8.8 µg/m³) is based on the annual average of the daily 24-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 wildfires, 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 wildfire smoke events in 2023 were unprecedented and caused widespread, elevated PM_2.5 concentrations across the province. Further information and analyses are provided in Wildfire smoke events in Ontario, 2023.

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 (2014-2023).

2023 results – Fine particulate matter

Two air zones did not achieve the CAAQS for PM_2.5 in 2023. Exceptional events, such as wildfire smoke, account for a significant portion of Ontario’s PM_2.5 when levels are elevated. All of Ontario’s CAAQS stations, apart from Hamilton Downtown, would have met the PM_2.5 CAAQS in 2023 if exceptional events were excluded from the calculated metric using a weight of evidence (WOE) analysis.

A summary of the 2023 CAAQS metric values for the 24-hour and annual PM_2.5 at individual CAAQS reporting stations is detailed in the Appendix: PM_2.5 and ozone CAAQS metric values for designated sites across Ontario (2023).

PM_2.5 CAAQS effective management levels for air zones across Ontario, 2023

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 2014 to 2023 in Ontario. There was no trend detected for Ontario 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 wildfires, 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 (2014-2023).

2023 results – Ground-level ozone

Three air zones did not achieve the CAAQS for ozone in 2023. Transboundary influences, from both the U.S. and beyond, account for a significant portion of Ontario’s ozone when their levels are elevated. All of Ontario’s CAAQS reporting stations would have met the ozone CAAQS in 2023 if transboundary flow days were excluded from the calculated metric using a WOE analysis.

A summary of the 2023 CAAQS metric values for 8-hour ozone at individual CAAQS reporting stations is detailed in the Appendix: PM_2.5 and ozone CAAQS metric values for designated sites across Ontario (2023).

Ozone CAAQS effective management levels for air zones across Ontario, 2023

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

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 2014 to 2023 in Ontario. This trend shows a decrease of 14% 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 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 wildfires, 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 2014 to 2023 in Ontario. This trend shows a decrease of 28% 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 annual CAAQS for NO₂ (17.0 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 CAAQS metrics at each of the designated monitoring sites, are presented in the Appendix: NO₂ and SO₂ CAAQS metric trends for designated sites across Ontario (2014-2023).

2023 results – Nitrogen dioxide

All six air zones achieved the CAAQS for NO₂ in 2023. A summary of the 2023 CAAQS metric values for the 1-hour and annual NO₂ at individual CAAQS reporting stations is detailed in the Appendix: NO₂ and SO₂ CAAQS metric values for designated sites across Ontario (2023).

NO₂ CAAQS management levels for air zones across Ontario, 2023

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 2014 to 2023 in Ontario. This trend shows a 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 7 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 wildfires, 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 2014 to 2023 in Ontario. This trend shows a decrease of 38% 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 the Appendix: NO₂ and SO₂ CAAQS metric trends for designated sites across Ontario (2014-2023).

2023 results – Sulphur dioxide

One air zone did not achieve the 1-hour CAAQS for SO₂ in 2023. A summary of the 2023 CAAQS metric values for the 1-hour and annual SO₂ at individual CAAQS reporting stations is detailed in the Appendix: NO₂ and SO₂ CAAQS metric values for designated sites across Ontario (2023).

SO₂ CAAQS management levels for air zones across Ontario, 2023

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