June 11, 2024

Developed by Toronto Public Health (TPH), Toronto’s 2023 Population Health Profile: Insight on the Health of Our City identifies environmental health including air pollution as an essential health indicator. Climate change poses significant health risks through environmental change, increasing extreme heat days, prolonged heat waves and more frequent wildfires. Now a global concern, wildfires affect air quality and public health far beyond their immediate areas.

More information about the Profile is available on the City’s Population Health Profile: Insight on the Health of Our City webpage.

In June 2023, for the first time, Toronto’s air quality was significantly affected by wildfire smoke, impacting vulnerable populations the most. TPH developed its first Wildfire Smoke Response Strategy which includes seasonal updates, response strategies and preparedness activities.

In May 2024, the Ministry of Health released the Wildfire Smoke and Air Quality Reference offering guidance to public health units including TPH for annual updates and incorporating lessons from 2023 when the entire province was impacted by deteriorations in air quality caused by wildfire smoke.

Purpose of Toronto Public Health’s Wildfire Smoke Strategy:

  • Prepare TPH for Wildfire Smoke Events: Outline proposed responses to Special Air Quality Statements (SAQS) and Air Quality Alerts (AQA) from Environment and Climate Change Canada (ECCC) and Ministry of the Environment, Conservation and Parks (MECP) including TPH actions and those of collaborating agencies.
  • Assign Roles: Designate roles, responsibilities and accountability within TPH (Appendix A).
  • Establish Communication: Outline clear communication pathways within TPH during wildfire smoke events.
  • Coordinate with Stakeholders: Document our points of collaboration with City divisions and community organizations.
  • Meet Protocol Requirements: Fulfill obligations under the Hazard Response Protocol, 2019, and the Ontario Public Health Standards Emergency Management Standard by conducting environmental surveillance and monitoring trends.
  • Collaborate on Exposure Reduction: Work with community partners to develop strategies to reduce exposure to health hazards and illness from poor air quality events due to wildfire smoke.

Note: The strategy is iterative and will be updated as new evidence emerges and in response to lessons learned


Outline the approach, roles and responsibilities within TPH when ECCC/MECP issues a SAQS and/or an AQA for wildfire smoke impacting air quality in Toronto.


Health Impacts of Wildfire Smoke

Wildfire smoke is a complex mixture of particulate matter and gases (CO, CO2, NOx) as well as polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). Particulate matter with particles less than 10 microns in size (PM10) can irritate the eyes and upper respiratory tract. Particles less than 2.5 microns in size (PM2.5) are of most significant health concern as they can penetrate deep into the lungs and cross into the blood, leading to various health effects. PM2.5 can constitute up to 90 per cent of the total particle mass of wildfire smoke.

Exposure to air pollutants can result in various symptoms including irritated eyes, irritated throat, runny nose and coughing. More severe symptoms include dizziness, chest pains, difficulty breathing, wheezing and heart palpitations. Individuals may also experience worsening mental health impacts such as anxiety, depression, post-traumatic stress disorder and general distress caused by natural disasters and climate change.

Those identified as being at higher risk for the negative health effects of wildfire smoke include:

  • Seniors
  • Indigenous people
  • People who smoke
  • Infants and young children
  • People living in rural and remote areas
  • Pregnant people
  • People involved in strenuous outdoor exercise
  • People who work outdoors
  • People living in situations of lower socioeconomic status, such as those with lower income, lower education, those experiencing housing insecurity and those experiencing uncertain employment
  • People with an existing illness or chronic health condition such as cancer, diabetes, or lung or heart conditions

Cleaner Air Spaces

In response to poor air quality during the 2023 wildfire season, the City is piloting Cleaner Air Spaces in six civic buildings with MERV13 filters and air conditioning: Toronto City Hall, Metro Hall, and Scarborough, East York, York, and North York Civic Centres.

These spaces will provide people who face barriers to accessing cleaner air and air filtration with places to access cleaner air during weather events with a prolonged impact on air quality. These spaces will be available until September 30.

Visit the City’s interactive Cleaner Air Spaces map for details about participating locations including a list of site amenities for all locations.

Air Quality Alert Notifications from the MECP

MECP provides a subscription service that allows users to sign up to receive email notifications to stay updated on air quality in their chosen forecast region(s).

This service alerts users to the following types of notifications:

  • Special Air Quality Statements (SAQS) are used when the AQHI is forecast to reach or has reached seven or greater for one to two hours to inform the public to be precautionary and vigilant of health risks.
  • Air Quality Advisory (AQA) for situations where the AQHI is forecast to reach or has reached 10+ and is expected to last for three or more hours.
  • Termination Notice for when the SAQS or AQA has ended due to improved air quality.
  • Both SAQS and AQAs are issued jointly by ECCC and MECP.

Air Quality Alert Notifications from ECCC using the WeatherCAN app

Another way to receive notifications is through the WeatherCAN app. Users receive push notifications for all weather alerts issued by ECCC for the phone’s location and saved locations anywhere in Canada. In addition, users can turn custom AQHI notifications on if they are available for the chosen location.

By doing this, the user will get AQHI notifications for the current conditions and the forecast. Notifications will also be sent when:

  • The current AQHI conditions or forecast have reached or exceeded the user’s custom value compared to the previous hour.
  • The current AQHI conditions have decreased below the user’s custom value in the previous hour.

Current AQHI (May 2024)

The AQHI is a tool designed to help the public make decisions to protect their health from air pollution. It measures air quality and health on a scale from one to 10+. The higher the number, the greater the health risk associated with the air quality. The AQHI guides the general population and at-risk populations.

The AQHI is a composite index calculated using concentrations of ozone, nitrogen dioxide and fine particulate matter smaller than 2.5 micrometres (PM2.5) in the air. It is meant to provide information on how these substances impact the health of people sensitive to air quality and the general population. It is measured and published by ECCC in collaboration with MECP. In addition to the observed conditions, ECCC provides forecast maximums for the AQHI.

Note: The AQHI was not specifically designed to address air pollution from wildfires.
ECCC and MECP are moving this year to another measure of air quality called AQHI+. During periods of deteriorating air quality caused by wildfire smoke, MECP and ECCC will use just the air concentration of PM2.5 to determine the AQHI rather than a formula involving PM2.5, NOX and SOX.

During these wildfire smoke events, when AQHI relies on PM2.5 exclusively, the AQHI may change more rapidly to respond to the changing significance of the deterioration in air quality.

ECCC and MECP may change their recommendations for the use of or the calculations leading to the AQHI at any time throughout the season. Should these recommendations/calculations change, TPH will adapt the Wildfire Smoke Response Strategy to align with provincial and federal recommendations and measures.

Toronto has four air monitoring stations. ECCC takes the average of these four stations’ measurements when producing the AQHI for Toronto overall.

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Toronto Public Health