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| Last Updated:: 03/04/2015

Air Pollution

Air is a precious resource that most of us take for granted. Air supplies us with oxygen, which is essential for our bodies to live. Without it, we would die within minutes.


Pure air is a mixture of several gases that are invisible and odourless. It consists of about 78% nitrogen, 21% oxygen, and less than 1% of argon, carbon dioxide, and other gases — as well as varying amounts of water vapour. Adults breathe in about 10-20 cubic metres of air every day. That’s about 20,000 breaths. Children breathe almost twice that amount because they are smaller, and their respiratory systems are still maturing.


The term “air quality” means the state of the air around us. Good air quality refers to clean, clear, unpolluted air. Clean air is essential to maintaining the delicate balance of life on this planet — not just for humans, but wildlife, vegetation, water and soil. Poor air quality is a result of a number of factors, including emissions from various sources, both natural and “human-caused.” Poor air quality occurs when pollutants reach high enough concentrations to endanger human health and/or the environment. Our everyday choices, such as driving cars and burning wood, can have a significant impact on air quality.


Ambient Air Quality

Ambient air quality refers to the quality of outdoor air in our surrounding environment. It is typically measured near ground level, away from direct sources of pollution.


Indoor Quality

Air pollution isn't only an outdoor problem. The air in enclosed spaces, such as home, schools or workplaces, can also be polluted, from pollutants that have seeped in from the outdoors and pollutants emitted from indoor sources. In fact, some kinds of air pollution can be worse indoors than outdoors, such as tobacco smoke, mould, and chemicals released from synthetic fabrics, furnishings and household products. Indoor air quality is important, since Canadians spend about 90 percent of their time inside.


How Air Quality is Degraded

Air quality is degraded when unwanted chemicals or other materials are released into the air in large enough amounts to harm the health of people, plants and animals, and our environment. This is called “air pollution,” and the harmful substances are called “air pollutants.” The quality of the air depends on the amount of pollutants, the rate at which they are released from various sources, and how quickly the pollutants disperse (or, conversely, how long they are trapped in an area).


Many air pollutants occur as gases or vapours, but some are very tiny solid particles, such as dust, smoke or soot. Some are emitted from natural sources, such as volcanoes, while many others come from human activity.

 Air (Prevention and control of Pollution) Act 1981

Annual Report 2012-13 Pollution Control Board

Air pollution can affect indoor air quality, as well. Indoor air pollutants include cigarette smoke, mould, dust mites, pet dander, formaldehyde, volatile organic compounds (VOCs) and radon gas. (See Indoor Air Quality.)


If air pollutants are in an area with good airflow, they will mix with the air and quickly disperse. However, when pollutants are trapped in an area, pollutant concentrations can increase rapidly.  This can happen when weather conditions (e.g., light winds and a temperature inversion aloft), and/or terrain features (e.g., mountains) limit the transport of pollutants away from an area. The outcome is air pollution — or “poor” air quality, as defined by Canadian environmental standards. For more information on how air becomes polluted, see Factors Affecting Air Quality and What are Pollutants and Emissions?