Smog and its Sources
The word smog is a combination of two words "smoke" and "fog" and dates back to 1905 when Dr. Des Vouex made reference to the smoky fog in Britain. The term ‘smog’ is used to describe a mixture of pollutants, primarily made up of ground level ozone (O3) and fine particulate matter (PM2.5). Other major precursors include sulphur dioxide (SO2), nitrogen oxides (NOx), volatile organic compounds (VOCs), carbon monoxide (CO) and ammonia (NH3). Increased levels of this mixture worsen air quality, impacting human and ecological health.
In Ontario, smog episodes were traditionally observed between May and September when nitrogen oxides and volatile organic compounds formed ground level ozone in the presence of sunlight. Such episodes tended to arise from burning gasoline and diesel in vehicles, and using fossil fuels to heat buildings, run industries and produce electricity in power plants.
The inclusion of fine particulate matter (PM2.5) to the Ontario Ministry of the Environment’s (MOE) Air Quality Index (AQI) in August 2002 enabled the monitoring and reporting of smog episodes year round. The first smog advisory issued by the MOE outside the traditional smog season was in Hamilton on October 10th, 2003 due to PM2.5. A more recent and longer lasting smog advisory was issued for several communities in Ontario and Quebec in February 2005. The advisory was in effect in the Halton-Peel region from February 4-7, 2005. Primary direct human sources of PM2.5 outside the traditional smog season are mainly due to wood heating (purchases of wood burning heating sources greatly increased in Quebec after the 1998 ice storm), motor vehicles and industrial activities.
Ontario’s highest smog levels tend to occur in the southwest and south central parts of the province, due to both local pollution sources and smog precursors generated in the United States. Weather conditions cause polluted air masses to move northeast from the United States over the Great Lakes. This allows ground level ozone precursors (NOx and VOCs) to react in the presence of sunlight, resulting in higher ground level ozone concentrations in the province. These conditions also allow for fine particles to travel northeast, increasing PM2.5 levels in Ontario.
Approximately 55 per cent of ozone and particulate matter measured in southern Ontario are due to the long-range transport of these pollutants and their precursors from the United States. In some areas along the northern shores of Lake Erie, the eastern shores of Lake Huron, and the extreme southwest parts of the province along the US border, this figure is about 90 per cent. Despite this large contribution from our neighbours, local emission problems are still present within Ontario. For example, during a smog episode in the Greater Toronto Area, approximately half of the PM2.5 emissions are from human activity in Ontario. This shows that we all need to take action to reduce smog precursors. Doing so will not only be beneficial for Ontarians but also for residents of Quebec, upper New York state, Vermont, New Hampshire, and Canada’s Maritime provinces who are the recipients of Ontario’s pollution.
Smog days for Halton-Peel since 1993
Year = No. of advisories = Total no. of smog days/duration
- 1993 = 1 advisory = 1 day
- 1994 = 2 advisories = 5 days
- 1995 = 5 advisories = 10 days
- 1996 = 2 advisories = 3 days
- 1997 = 2 advisories = 5 days
- 1998 = 3 advisories = 7 days
- 1999 = 5 advisories = 9 days
- 2000 = 3 advisories = 3 days
- 2001 = 7 advisories = 20 days
- 2002 = 9 advisories = 18 days
- 2003 = 5 advisories = 13 days (June 23, 24, 25, 26; July 1, 2, 3, 4; July 26; July 31, August 1, 20,21)
- 2004 = 6 advisories = 14 days (May 8, 9, June 13, 14, July 21, 22, August 26, 27, September 4, 5, 6, 23, 24, 25)
- 2005 = 14 advisories = 48 days (February 4, 5, 6, 7, April 19, 20, May 8, 9, 10, June 2, 3, 4, June 5, 6, June 8, 9, 10, 11, 12, 13, 14, June 24, 25, 26, June 27, 28, 29, 30, July 4, 5, July 11, 12, 13, 14, 15, July 21, August 3, 4, August 8, 9, 10, September 12, 13, 14, October 3, 4, 5, 6)
- 2006 = 5 advisories = 11 days (May 28, 29, 30, 31, June 17, 18, 19, July 17, August 1, 2, 27)
- 2007 = 11 advisories = 31 days (May 8, 9, 10, May 23, 24, 25, May 30, 31, June 1, 2, 3, June 13, 14, 15, 16, 17, 18, 19, June 25, 26, 27, July 10, 11, August 1, 2, 3, 29, September 6, 7, 19, October 5)
- 2008 = 6 advisories = 13 days (April 18, 19, 20, June 13, July 7, 8, 16, 17, 18, 19, August 22, 23, September 3)
- 2009 = 2 advisories = 4 days (May 21, August 15, 16, 17)
- 2010 = 2 advisories = 7 days (July 4, 5, 6, 7, 8, August 30, 31)
Smog Days -- Did you know?
Smog affects our health and the environment. Those most susceptible to smog include children, seniors and people with asthma, heart and lung conditions. Common health effects include eye, nose and throat irritation, coughing, wheezing and shortness of breath.
In 2005, the Ontario Medical Association estimated the health impacts associated with air pollution exposure. The estimates for Halton were 190 premature deaths, 540 hospital admissions, 2,010 emergency room visits and one million minor illness days per year resulting in an estimated $17 million in healthcare costs (not including visits to family doctors) and $13 million in lost productivity costs (as employees were too sick to go to work due to poor air).
Ozone in the upper atmosphere protects the earth from the sun's harmful ultraviolet (UV) rays. Ozone at ground level, where humans live and breathe, is toxic and irritates mucous membranes.
Ground-level ozone can seriously damage crops and forests by attacking the foliage of plants, reducing growth and crop yield.
Cars, trucks, power plants and manufacturing industries burn fossil fuels, producing nitrogen oxides (NOx). In Ontario, motor vehicles are the largest single source of NOx emissions.
One busload of passengers removes up to 40 vehicles from the road, saves 70,000 litres of fuel and avoids nine tonnes of air pollutants a year.
In the early part of the 1900s, smog was actually considered a London attraction by some. Many travelled to the city to experience a 'pea-souper' first-hand. Impressionist painter Claude Monet was inspired by smoggy conditions on the Thames for one of his most famous series.
In the Great Smog of 1952, over 4000 people died in London.