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Canadian Environmental Sustainability Indicators: Highlights

Air quality

What is the issue?

Ground-level ozone, a key component of smog, has significant negative effects on human health, on the natural environment, and consequently, on economic performance.

What is happening?

The national seasonal average concentration of ozone increased 16% from 1990 to 2003. Most monitoring stations are located in urban areas in Southern Canada.

The highest seasonal average ozone concentrations in 2003 were all recorded at stations in Southern Ontario; concentrations in this region had also grown the fastest since 1990.

National seasonal average ground-level ozone concentration, Canada, 1990 to 2003

Figure: National seasonal average ground-level ozone concentration, Canada, 1990 to 2003

Notes: Results are weighted by population. Both the linear regression and yearly means are shown. Based on 79 monitoring stations.

Sources: Environment Canada, National Air Pollution Surveillance Network Database; Statistics Canada, Environment Accounts and Statistics Division.

What does it mean?

Ground-level ozone has been linked to human health effects ranging from minor respiratory problems to emergency room visits and hospitalizations. Related economic effects include absenteeism, lower labour force participation and increased health care costs. Children, the elderly and those with pre-existing health conditions are most sensitive to high ozone levels.

Why is it happening?

Ozone is formed by chemical reactions involving nitrogen oxides and volatile organic compounds in the presence of sunlight. Most nitrogen oxides come from human activities such as burning fossil fuels in motor vehicles, homes, industries and power plants. Canadians contribute to volatile organic compounds in the air primarily by producing oil and gas, by driving off-road vehicles as well as light-duty motor vehicles and trucks, and by burning wood in stoves, furnaces and fireplaces in their homes. Evaporation of gasoline and other liquid fuels and solvents also adds volatile organic compounds to the air. Ozone levels are affected not only by local activities but also by weather conditions and the movement of pollutants from other regions and countries.

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Date modified: 2005-12-14	Important Notices