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