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Air Quality 

Air quality is a measure of the cleanliness of the air we breathe.  Nearly everything we do and every product we buy creates some form of pollution.  Some of this pollution gets into the air in the form of gases or particles.  One of the main problems with air pollution is deciding when it occurs.  For example, when is the exhaust from cars and trucks causing too much pollution?

In Alberta, governments, industries, and citizens work together to set standards which limit the amount and types of pollution allowed into the air.  Standards allow us to control emissions.  By measuring the amount of certain pollutants in the air, we can obtain a measure of air quality.

Life on Earth exists within a narrow band called the biosphere.  The biosphere is only about 15 kilometres in depth.  There are three parts to the biosphere; the lithosphere (rock and soil), the hydrosphere (water) and the atmosphere (air).  The atmosphere extends outwards from the earth's surface for several hundred kilometres and is made up of four layers.

Atmosphere DiagramThe first layer, called the troposphere, is where all our weather takes place and is the only layer of the atmosphere to support life.  The troposphere has a range of about 8 to 12 kilometres in depth.  Human activities can cause changes to the quality of this layer and to the stratosphere, the atmosphere's second layer.  In the troposphere, the air we breathe is a complex mixture of gases.  It is 78 percent nitrogen, 20 percent oxygen, 0.9 percent argon, 0.03 percent carbon dioxide with traces of other gases.  Water vapour is also present in varying amounts depending on your location.  In addition, there are several other gases and particles that are the result of human activities.  The quality of our air we experience is related to the composition of the gases and particles that make up our atmosphere.

Air pollution from natural sources has been a feature of the earth for millions of years.  Many scientists believe the extinction of the dinosaurs was caused by a large asteroid which hit the earth.  The cloud of dust caused by the collision was so thick that the earth cooled and the dinosaurs could not survive in the changed environment.  Volcanic smoke and dust, sand and dust storms, and wild fires are all sources of "natural" air pollution.  In fact, air borne particulates from volcanic eruptions have shown strong correlation with climate variability.

Early humans have also contributed to air pollution by setting fires to drive game or to clear land.  Poorly designed fireplaces in dwellings with inadequate ventilation created smoky indoor environments.  The early industrial cities of Europe and North America were probably the most polluted environments created by man.  Most power and household heating came from coal fires.  The thick black smoke from these fires hung over the cities and blackened exposed surfaces with soot.  Other pollutants like sulphur dioxide and oxides of nitrogen were also present.  By the 1950s people were beginning to realize that pollution was affecting their health and the health of plants and animals.

Today, many visible effects of air pollution have been eliminated in North America.  Cleaner fuels such as natural gas are being used and manufacturing processes reduce their emissions by being more efficient in their use of energy and raw materials.  Many smokestacks have dust collectors or scrubbers to reduce harmful emissions.  Not all pollutants can be removed completely, but the smokestack giving off thick black smoke is nearly a thing of the past, at least in North America.

Reprinted from Focus On Air Quality  (1993) with permission of Alberta Environment.

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