Air pollution describes a collection of airborne pollutants that contribute to our air quality. The term “pollutants” recognizes that these substances are undesirable because of their impact on human health, the environment and the economy.

These air pollutants are all very different. They differ in their chemical composition, reaction properties, emission sources, how long they last in the environment before breaking down, their ability to move long or short distances, and their eventual impacts.

However, they also share a number of similarities, and so can be grouped into four general categories:

Criteria Air Contaminants and related pollutants are cause to air issues such as smog and acid rain. They are produced in varying quantities by a number of sources, including the burning of fossil fuels.

Persistent Organic Pollutants are a collection of pollutants that can last in the environment for long periods of time and are capable of travelling great distances. Similar to heavy metals, POPs are of particular concern because they can enter the food supply, bioaccumulate in body tissues, and have significant impacts on human health and the environment, even in low concentrations.

Heavy metals are basic metal elements such as mercury and lead. This group of pollutants can be transported by the air and enter our water and food supply. Although trace amounts of some metals are needed by our body, heavy metals are poisonous in low concentrations and can bioaccumulate in body tissues.

Toxic Pollutants form a broad category of pollutants that are poisonous or toxic to human health and the environment. Although this category has some overlap with the other types of air pollutants presented here (CAC, HM, POPs etc), it also includes many more pollutants that have been determined to be toxic.

The Canadian Environmental Protection Act, 1999 (CEPA 1999; schedule 1) provides a list of pollutants of concern that are subject to legislative control and management. CEPA 1999 has also legislated that these pollutants be reported to the National Pollutant Release Inventory (NPRI).