May 22,



What is smog?

Smog most often occurs on hot and humid days between May and September, although it can occur any time of year.  Ground level ozone and fine particulate matter are the key components of smog.

Ground level ozone – formed when gases in the environment react in the presence of sunlight.

Fine particulate matter – a mixture of solid particles and liquid droplets coming from many sources such as:

  • factory emissions;
  • windblown dust;
  • vehicle exhaust; and
  • oil and gas emissions from homes.

Where does smog come from?

Today’s cars release approximately 95% fewer emissions than cars 30 years ago, yet the transportation sector accounts for almost one third of Canada’s gas emissions.

Smog comes from a variety of sources including:

  • gasoline and diesel vehicles,  and lawn/garden equipment;
  • coal-fired power plants;
  • pesticides;
  • oil based paints, solvents and cleaners;
  • barbecues;
  • road paving and construction; and
  • pollutants from metal refineries and battery manufacturing.

Who is affected by smog?

Smog affects everyone’s health, however some people are more sensitive to the effects of air pollution than others.

Smog is especially harmful to:

  • seniors;
  • children;
  • persons with heart and Lung conditions, asthma and allergies; and
  • people who work or exercise outdoors.

Last modified on May 14, 2012