Air Quality

Air quality in your community

Southwestern Public Health maintains partnerships with members of the community, the Ministry of Environment & Climate Change, Ministry of Health and Long Term Care and Public Health Ontario in identifying and studying air quality issues. Public Health also provides air quality education to the public, responds to complaints and advocates for healthy public policy.

The air around us is made up of nitrogen (78%), oxygen (21%) and small amounts of other gases. Both natural and human activities release gases that cause an imbalance in the air. These releases are called air pollutants.

People exposed to high enough levels of certain air pollutants may experience:

  • Irritation of the eyes, nose and throat
  • Wheezing, coughing, chest tightness and breathing difficulties
  • Worsening of existing lung and heart problems, such as asthma
  • Increased risk of heart attack 

In addition, long-term exposure to air pollution can cause cancer and damage to the immune, neurological, reproductive and respiratory systems. In extreme cases, it can even cause death. While air pollution can affect everyone’s health, infants, children and older adults are more vulnerable to the effects.

Air Quality Health Index

Ontario’s Air Quality Health Index (AQHI) is a health based scale that assesses air pollution as well as cumulative health impacts.

The AQHI provides air quality measurements and forecasts so members of the public can more easily understand what the quality of the air around them means to their health. The index ranks air quality from 1 to 10+, just like the UV index protects people from the harmful effects of too much sun. The lower the number, the lower the risk.

Click here to view the current Air Quality Health Index forecast for communities across Ontario. The Air Quality Health Index does not list forecasts for Oxford or Elgin Counties. Refer to the London or Kitchener forecast for the most accurate forecast for our area.

For a more detailed explanation of the new AQHI, watch this video from the Ministry of Environment and Climate Change.


The index is designed to help them make decisions to protect their health during episodes of increased air pollution.

When the Air Quality Health Index reading rises, people can:

  • Reduce or reschedule outdoor physical activities
  • Monitor possible symptoms, such as difficulty breathing, coughing or irritated eyes
  • Follow their doctor’s advice to manage existing conditions such as asthma
  • Do their part by taking public transit

Types of air pollutants

Carbon Monoxide (CO) is a colourless, ordourless, and tasteless gas. It is a by-product of incomplete combustion of fossil fuels. In Ontario, the main sources of CO emissions come from road vehicles and other forms of transportation. When CO is inhaled, it enters the blood stream and reduces our bloods ability to carry oxygen to our tissues and organs. Exposure to high levels of CO has been associated with impaired vision, headache, dizziness, weakness, confusion and may also lead to death.

Sulphur Dioxide (SO2) is a colourless gas, but unlike carbon monoxide, has an odour of burnt matches. In Ontario, the main source of SO2 emissions comes from utility and smelting industries. When SO2 is inhaled. it can cause severe irritation of the nose and throat and can result in various respiratory symptoms and conditions including asthma. Exposure to high concentration of SO2 can cause death.

Nitrogen Dioxide (NO2) is a reddish-brown gas with a strong, irritating odour. NO2 is a major product of all combustion and plays a big role in the production of ground-level ozone. In Ontario, the main sources of NO2 emissions come from road vehicles and other forms of transportation. When NO2 is inhaled, it can irritate the lungs and may lower the resistance to respiratory infections.

Particulate Matter (PM) is a mixture of solid and liquid particles in the air. It can come in a wide variety of sizes including PM10 and PM2.5.

  • Inhalable Particulate Matter or PM10 is 10 microns in diameter and less.
  • Respirable Particulate Matter or PM2.5 is 2.5 microns in diameter and less.

In Ontario, the major sources of PM include residential sectors, transportation sectors and industrial processes. Breathing in both PM10 and PM2.5 can cause a variety of health problems including respiratory illness. Since PM2.5 is smaller than PM10, it can travel deeper into our lungs and has the potential to cause more serious health effects. Exposure to PM2.5 has been associated with hospital admissions and premature death.

Ozone (O3) is a colourless and odourless gas that is created when emissions, containing nitrogen oxides and volatile organic compounds, react in the presence of sunlight. Ozone tends to be a problem around cities during hot summer days. When ozone is inhaled, it can irritate the respiratory tract and eyes. Exposure to high levels of ozone has been associated with various respiratory problems including chest tightness, coughing and wheezing. It has also been associated with an increase in hospital admissions and premature death.

Last Updated: June 1, 2018