What is air quality

Air quality describes the state of the air around us. Good air quality means clean, unpolluted air.

Poor air quality happens when pollutants reach concentrations that are of concern to human health and/or the environment.

Poor air quality comes from a number of factors, including emissions from various natural and man-made sources (e.g. forest fires, vehicles, power plants, industrial processes and residences), and is influenced by atmospheric and weather conditions.

Air pollution and your health

Clean air is critical for human health and the health of the environment.

Air pollution can:

  • make it harder to breathe
  • irritate your lungs and airways
  • worsen chronic diseases such as heart disease, chronic bronchitis, emphysema and asthma

Each person reacts differently to air pollution. Children, seniors and those with diabetes, heart or lung disease are most sensitive to the effects of air pollution.

Negative health effects can increase as air pollution worsens. Symptoms can increase if you are exposed to air pollution for a long time or breathe in a lot of it.

Monitoring air quality

Ontario maintains and operates a network of 38 ambient (outside) air monitoring stations across the province that collect data and report on key pollutants that are indicators of overall air quality.

Ambient air monitoring stations are established in communities across Ontario so the data we gather represents the exposure of the general population. However, some neighbourhoods that are located near local sources, such as industrial facilities, might have higher concentrations of pollutants than what our monitoring stations measure.

The Air Quality Health Index (AQHI) provides the relative risk of a mixture of common air pollutants that are known to harm human health.

Visit airqualityontario.com to find:

  • pollutant concentrations (reported hourly, 24 hours a day, 7 days a week)
  • the Air Quality Health Index (reported hourly, 24 hours a day, 7 days a week)
  • air quality forecasts
  • information on what to do when a Special Air Quality Statement or Air Quality Advisory is issued

We also publish an annual air quality report that provides information about the state of air quality provincewide and examines 10-year trends for key pollutants.

Status of our air quality

Our air quality has improved significantly over the past 10 years.

Since 2013, levels of smog-causing pollutants in the air have declined significantly, Ontario experienced a:

  • 48% decrease in sulphur dioxide
  • 28% decrease in nitrogen dioxide
  • 18% decrease in fine particulate matter

In 2022:

  • Ontario’s air was reported in the low-risk category for 94% of the year
  • there were no smog advisories issued

For more information, read the 2022 Air Quality Report.

Reducing greenhouse gas emissions

Ontario has taken many steps to improve air quality. We were one of the first places in the world to eliminate coal as a fuel to generate electricity.

We are working with industries to help them cut their greenhouse gas (GHG) emissions by reducing and phasing out the use of coal in their operations.

In 2022, the province announced support for two Ontario steel facilities to replace their use of coal. This will result in significant GHG emission reductions—about 3 million tonnes a year per facility. That’s about the same as taking almost 2 million more cars off our roads.

Greening Ontario’s steel sector:

  • will significantly improve local air quality by reducing toxic pollutants such as benzo[a]pyrene, benzene and sulphur dioxide
  • represents a significant step in the fight against climate change

Progress since 2022

  • Continued to implement a strategy to address industrial emissions. This includes enhanced oversight of industrial facilities such as enhanced inspections, reactive incident response, monitoring and communication with local stakeholders.
  • Introduced a new regulation that sets emission limits that will significantly reduce emissions of sulphur dioxide from petroleum facilities in Sarnia by the end of 2028. The regulation will also result in reduced sulphur dioxide emissions from other petroleum facilities in Mississauga and Nanticoke.
  • Completed the Sarnia Area Environment Health Project (SAEHP) which assessed the risk of air pollution in the Sarnia area.
  • Developed short-term health benchmarks for benzene, a contaminant associated with elevated health risks in north Aamjiwnaang First Nation Reserve and south Sarnia.
  • Implemented the enhanced emissions testing program for commercial trucks and buses to further reduce pollutants in our air. This program was integrated with the Ministry of Transportation’s annual safety Motor Vehicle Inspection Station program in 2022.
  • Enhanced our ambient Air Quality Health Index and roadside air monitoring networks by modernizing the fine particulate matter (PM2.5) air monitoring network with the latest technology.
  • Deployed new technology to the ministry’s downtown Hamilton AQHI air monitoring station to better understand industrial and traffic related air pollution.
  • Worked with the federal government, the state of Michigan, and the United States Environmental Protection Agency to better understand ozone formation and transport in our shared airshed.
  • Continued reporting on ambient and roadside air quality that confirms Ontario’s actions to reduce airborne pollutants are working and that regional air quality has been steadily improving in Ontario for many common air pollutants over the past 10 years.

Air quality reports