Glossary

Air pollution: The degradation of air quality by contaminants to the point that they may injure health, property, plant or animal life, or prevent the use and enjoyment of the outdoors.
Air Quality Advisories: (See Smog Advisories)
Air Quality Index (AQI): Provides information on the adverse effects of the more common air pollutants. It is designed to identify the worst effects that may result from the mixture of pollutants currently being measured and to describe the prevailing air quality.
Airborne particles: (See Particulate matter)
Ambient air: Outdoor air.
Atmosphere: The envelope of air which surrounds the earth and is bound to it by gravity.
Carbon monoxide: (chemical formula : CO) A colourless, odourless, poisonous gas produced when carbon-containing substances such as coal, oil, gasoline, wood, or natural gas do not burn completely.
Coarse particles: Category of particulate matter with particles having a diameter of between 10 and 2.5 micro-metres, referred to as PM₁₀.
Contaminant: Unwanted chemicals and other materials in the air.

Dispersion: The process of reducing high concentrations of air pollutants through atmospheric motion.
Emission: A discharge or release of pollutants into the air, such as from a smokestack or automobile engine.
Environment: The combination of all external conditions and influences relating to the life, development, and survival of all living things.
Fine particles: Category of particulate matter with particles having a diameter of less than 2.5 micrometres, referred to as PM_2.5.
Ground-level ozone: Ozone is produced at ground level when some of the chemical components of vehicle exhaust and industrial emissions react with sunlight. At ground level, ozone is a powerful and irritating pollutant. In fact, it is the main component of smog. (See also Ozone, Stratospheric ozone).
Haze: The term haze is used when pollutants, fine dust or salt particles or moisture in the air reduce visibility. Haze usually has a yellow or bluish tinge.
Health Advisory: Issued in some regions along with Smog Advisories, recommending that people with certain health considerations consult their physicians.
Hydrocarbons: Compounds found in fossil fuels, glues, paints, and solvents that can react with other pollutants to cause smog. (Also referred to as Volatile Organic Compounds (VOC’s)).
Inversion: See Temperature Inversion
Long-range transport: The movement of pollutants with the wind from one region to another.
Nitrogen oxides: (designated NO_x) Gases that form when nitrogen and oxygen in the atmosphere are burned with fossil fuels at high temperatures.
Ozone: (chemical formula : O₃) Ozone is a pungent-smelling, slightly bluish gas which is a close chemical cousin to oxygen. About 90 percent of the earth’s ozone is located in a natural layer high above the surface of the globe in a region of the atmosphere called the stratosphere (see Stratospheric ozone). Ironically, while high-level ozone is beneficial to the environment, ground-level ozone is not (see Ground-level ozone).
Particulate matter: ParticulateMatter (PM) is made up of very tiny solid or liquid particles that are small enough to remain suspended in the air. These include dust, smoke, fumes, spray and mist.
Photochemical process: The chemical changes resulting in smog brought about by the energy of the sun acting on air pollutants, such as nitrogen oxides and volatile organic compounds.
Pollution: Impurities in air, water and land that create an unclean environment.
Precursor pollutants: Pollutants which then react chemically in the atmosphere to form other pollutants such as ground level ozone and fine particulate matter. Key precursors include oxides of nitrogen (forming ozone and particulate matter); volatile organic compounds (forming ozone and particulate matter); and ammonia (forming particulate matter).
Secondary pollutant: An air pollutant formed in the atmosphere from other pollutants instead of being emitted directly by a source.
Smog: A combination of particulate matter, ground-level ozone and other chemical pollutants which can reduce visibility and have other harmful effects.
Smog Advisory: Alerts citizens when ground-level ozone concentrations are expected to exceed the national standard (poor category).
Smog Forecast: A prediction of expected levels of ground-level ozone issued by Environment Canada or other local or regional governmental departments.
Smoke: The gaseous products and small carbon particles resulting from incomplete combustion.
Stratosphere: The layer of air that extends from about 11 to 50 kilometres above the earth’s surface.
Stratospheric folding: The earth's atmosphere is composed of well identified layers. The two layers closest to the earth's surface are the troposphere and the stratosphere. From time to time, parcels of air from the Stratosphere (15 to 40 kilometres above the earth's surface) will sink down into the troposphere ( surface to 15 kilometres above the surface). This process is known as Stratosphere - Troposphere Exchange (STE). Occasionally, in relatively unpolluted areas of Canada, locally high levels of ozone occur at the surface. This is frequently due to stratospheric folding.
Stratospheric ozone: The natural layer of the earth’s ozone located in the stratosphere. Here, it protects the earth and all that lies within it from the harmful effects of the sun’s ultraviolet radiation by absorbing much of it. (See also Ozone, Ground-level ozone).
Temperature inversion: In the troposphere, temperatures usually decrease the higher you go. With an inversion, the temperature increases with altitude.
Toxic: Something that can be poisonous or deadly if eaten, touched or inhaled in large enough amounts.
Troposphere: Layer of air closest to the earth. It ranges from 6 to 7 kilometres above the surface at the poles to 20 kilometres in the tropics.
Volatile organic compounds (VOC): Contaminants that can help form ozone near the ground and can be harmful to health. (see also Hydrocarbons).