Air is the ocean we breathe. Air supplies us with oxygen which is essential
for our bodies to live. Air is 99.9% nitrogen, oxygen, water vapor and inert
gases. Human activities can release substances into the air, some of which can
cause problems for humans, plants, and animals.
Smog is a type of large-scale outdoor pollution. It is caused by chemical
reactions between pollutants derived from different sources, primarily
automobile exhaust and industrial emissions. Cities are often centers of these
types of activities, and many suffer from the effects of smog, especially during
the warm months of the year. Additional information about smog and its effects
are available from
Environment Canada and the Air
Quality Management District (AQMD) in southern California.
For each city, the exact causes of pollution may be different. Depending on the
geographical location, temperature, wind and weather factors, pollution is
dispersed differently. However, sometimes this does not happen and the pollution
can build up to dangerous levels. A temperature inversion occurs when air close
to the earth is cooler than the air above it. Under these conditions the
pollution cannot rise and be dispersed. Cities surrounded by mountains also
experience trapping of pollution. Inversion can happen in any season. Winter
inversions are likely to cause particulate and carbon monoxide pollution. Summer
inversions are more likely to create smog.