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

Ontario has identified three air zone categories under the federal Air Quality Management System based on factors such as pollutant sources, topography, meteorological patterns, population density and other potential factors that influence ambient air concentrations.

This has resulted in six air zone areas for the province as presented in the table below.

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

• The air zone management level is determined by the designated CAAQS reporting station(s) with the highest CAAQS metric within the air zone.
• 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 framework

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

The management levels for each CAAQS pollutant are presented in the Appendix: Management Levels for CAAQS Pollutants.

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 2011 to 2020 in Ontario. This trend shows Ontario’s decrease of 19% 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.

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 2011 to 2020 in Ontario. There was no significant trend 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 annual PM_2.5 (8.8 µg/m³) is based on the annual mean averaged over three consecutive years.

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 Appendix: PM_2.5 and ozone CAAQS metric trends for designated sites across Ontario (2011-2020).

2020 results – Fine particulate matter

A summary of the 2020 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 (2020).

PM_2.5 CAAQS management levels for air zones across Ontario, 2020

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 2011 to 2020 in Ontario. This trend shows Ontario’s decrease of 9% over this 10-year period. Select another location from the drop-down menu to learn the percent change in air quality for other communities.

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.

The 10-year trends, based on the 8-hour ozone CAAQS metrics at each of the designated monitoring sites, are presented in Appendix: PM_2.5 and ozone CAAQS metric trends for designated sites across Ontario (2011-2020).

2020 results – Ground-level ozone

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 2020 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 (2020).

Ozone CAAQS effective management levels for air zones across Ontario, 2020

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 their 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 2011 to 2020 in Ontario. This trend shows Ontario’s decrease of 9% 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.

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 2011 to 2020 in Ontario. This trend shows Ontario’s decrease of 27% 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 CAAQS metrics at each of the designated monitoring sites, are presented in Appendix: NO₂ and SO₂ CAAQS metric trends for designated sites across Ontario (2011-2020).

2020 results – Nitrogen Dioxide

A summary of the 2020 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 (2020).

NO₂ CAAQS management levels for air zones across Ontario, 2020

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 2011 to 2020 in Ontario. This trend shows Ontario’s decrease of 19% 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 9 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.

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 2011 to 2020 in Ontario. This trend shows Ontario’s decrease of 47% 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 9 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 (2011-2020).

2020 results – Sulphur Dioxide

A summary of the 2020 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 (2020).

SO₂ CAAQS management levels for air zones across Ontario, 2020

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