It’s not just a problem for large industrial cities. Learn more about smog and how to protect yourself.

What is smog?

Smog is a mixture of air pollutants, including gases and particles that are too small to be seen. Smog can also contain other harmful components such as nitrogen oxides, volatile organic compounds, sulphur dioxide and carbon monoxide.

Smog often appears as a brownish-yellow haze over cities and the levels can be high in rural and suburban areas. As the colour of smog is determined by the suspended particles which compose it, smog is sometimes colourless.

Since smog is a mixture of many air pollutants, adverse health effects depend on a number of factors including the types and levels of pollutants in the air, the duration of exposure, the age and general state of health of exposed individuals, and the weather conditions. The air pollutants of most concern to human health are ground-level ozone and particulate matter (PM).

What are the potential health effects of smog?

Smog can irritate your eyes, nose, and throat, and can cause wheezing, coughing, and breathing difficulties. Smog may adversely effects the lungs and heart, and has been linked to increased respiratory and cardiovascular hospitalizations. It can aggravate pre-existing heart and lung conditions, such as asthma, emphysema and bronchitis, and in some cases can result in premature death.

Studies show that ozone continues to cause lung damage even when the acute symptoms disappear, and that repeated exposure can result in permanent damage to the lining of the lungs. Studies also suggest that long-term regular exposure to particulate matter can increase the risk of early death and perhaps lung cancer.

Who is at greater risk?

Smog can affect anyone’s health, even healthy adults can breathe less well on days when the air is heavily polluted. Some people are more sensitive to the effects of air pollution than others and may experience adverse health effects at lower levels of air pollution. For example:

How can you protect yourself from the health risks of smog?

To protect yourself from potential adverse health effects of smog you need to be aware of smog levels and take actions to reduce exposure to it. Check the Air Quality Index (AQI) in your community. The air quality index for communities across Ontario is reported daily in newspapers and on the radio, TV, and the Ministry of the Environment and Climate Changes’ website.

If a smog advisory is issued in your community:

Sign up to get smog alerts emailed to you:

How can you reduce smog levels in your community?

To help reduce overall smog levels in your community, consider buying a fuel-efficient vehicle, using public transportation instead of a car whenever possible, and reducing energy consumption in your home.

For more information:

If you would like to speak to a public health inspector about smog, you can submit your question or complaint electronically or call 705.522.9200, ext. 464 (toll-free 1.866.522.9200).

This item was last modified on August 16, 2019