Pollution Issues

Air pollution is a broad term applied to any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere. Examples include particulate matter and ground-level ozone.

Air pollutants fall into four main categories: criteria air contaminants, persistent organic pollutants, heavy metals and toxics. Individual pollutants differ from one another in their chemical composition, reactions with other chemicals, sources, persistence, ability to travel through the atmosphere, and impacts.

This section contains information air pollutants, their sources, and how they affect human health and the natural environment.

Often we do not think of air pollution as separate pollutants, but as the broader issues that these pollutants are a part of, including:

These issues are influenced by several factors including our land use patterns and behaviours, as well as the transboundary movement of air pollutants across long distances, such as from the United States.

Climate change and stratospheric ozone depletion are related issues of concern.


Smog compromises the quality of our air. It can be seen as a yellow-brown haze along a city skyline or as a thick pollutant-rich fog enveloping our daily activities and natural landscapes. When the pollutants and conditions for producing smog come together in the right way (or perhaps the wrong way), the result can be quite severe, leading to many human health and environmental concerns.

Acid Precipitation (Acid Rain)

Acid precipitation, or acid rain, continues to be a major concern for our natural and built environments, especially in the eastern regions of Canada (i.e. the Windsor to Quebec City corridor). Its impacts can be as subtle as lowered vegetation growth and productivity, to as dramatic as significant losses in forest cover and aquatic life. Many of our limestone buildings and statues are particularly vulnerable to the effects of acid rain.

Indoor Air Pollution

Air pollution is not only an outdoor problem. The air indoors, at home and in your workplace can also be polluted, and in some cases be more polluted than outside. Many types of indoor air pollution exist, such as mould, smoke, and carbon monoxide. Indoor air quality is particularly important since, on average, Canadians spend most of their time indoors.

Land Use

The design of cities and our roadways, and the location of our places of work and home and other aspects of land use all influence how much we need our motor vehicles to get around. The concern is that this dependency secures or increases transportation's role as one of the major sources of air pollution.

At the same time, forests, prairies and other natural features are lost in order to make way for our roads, cities and industrial activities, which can reduce the ability of the environment to naturally filter out many air pollutants, or even maintain healthy populations.

Transboundary Movement of Air Pollutants

Air pollution does not respect political boundaries, whether provincial or national. Winds can transport pollutants long distances away from their source, adding to the levels of air pollution that are generated locally, and greatly increasing the intensity of our air quality concerns.

Recognizing the need for collaboration and partnership, Canada and the United States have entered into an agreement to monitor and mediate sources of transboundary air pollutants.

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