What is Smog?
Smog, a combination of the words 'smoke' and 'fog', is the brownish-yellow haze that typically hovers over urban areas on days that are hot, dry and windless. Its two main contaminants are ground level ozone (O3) and small airborne particles. Ozone forms when nitrogen oxides and volatile organic compounds (VOCs) react with sunlight. Fine airborne particles include nitrogen oxides, sulfur dioxide, particulate matter (PM), carbon monoxide, VOCs and ammonia. Smog is associated with the summertime, and although it is true that smog levels peak between May and September, smog occurs during winter, too. Because of car emissions levels of carbon monoxide, nitrogen oxides and sulfur dioxide are actually higher in the wintertime. In Ontario, 61% of nitrogen oxides originate from the transportation sector (cars, trucks, buses, etc.). 23% come from the industrial sector and 12% from coal- and oil-fired electricity generation.
Smog tends to be worse in areas that are more densely populated areas and in low-lying places where air gets trapped. In Hamilton, it is difficult for smog to disperse because the Niagara Escarpment traps it in the downtown core. Air quality in Hamilton appears to be worst in the downtown region and on the Escarpment and better in the west end of the city.
In all of Canada, the highest levels of smog occur in the Windsor-Quebec urban corridor (which includes Hamilton). They are also higher in the Fraser Valley, British Columbia, and in Atlantic Canada (particularly southern New Brunswick and southwestern Nova Scotia), where 80% of the pollution migrates from eastern North America.
Figure 1 below shows the numbers of smog advisory days and poor air quality days over the past nine years. Poor air quality days are defined as days where the AQI was greater than 49 for at least 1 hour during the day.
Figure 1: Number of Poor Air Quality Days and Smog Advisory Days in Hamilton between 1999 and 2013
Ontario's Smog Alert Program was enhanced on August 23, 2002 when PM2.5 was incorporated into the provincial Air Quality Index. Prior to this date smog advisories were issued only for exceedances in ground-level ozone levels.
Where does Smog come from?
  • Gas/diesel-powered vehicles: Emissions from cars, trucks, buses, lawn mowers, snowmobiles, all-terrain vehicles, leaf blowers, etc. are a main source of smog in Ontario. 61% of Ontario's nitrogen oxides are caused by just cars, trucks and buses.

  • Industry: Almost a quarter of the nitrogen oxides formed in the atmosphere in Ontario is due to industry and commerce.

  • Around the house: Wood-burning stoves, barbeques, air conditioners, cleaning solvents, glues, paints, lawn chemicals, perfumes, antiperspirants, nail-polish, make-up and even room fresheners all contribute quite significantly to smog-forming pollution. They are especially dangerous because they are found inside, in close contact to higher concentrations of people. Typically, around-the-house items aren't thought to be a contributor to the smog problem.

  • Construction: Road paving and construction generate a lot of dust and airborne particles that are unhealthy to breathe in and contribute to higher smog levels.

  • Transboundary: It is estimated that 55% of Ontario's pollution stems from across the border.

Smog and the Surrounding Environment
It is suggested that there is a direct link between climate change and the amount of smog in the air. Smog tends to exist in higher concentrations in places where the average temperature is higher. Both affected by emissions and pollution, it is expected that by decreasing air pollution, it would stop smog from forming and stop the temperature from rising.
Smog has an adverse effect on plants and plant life. Ozone, in particular, is very harmful to plants. It hinders their growth and shortens their lifespan by limiting the amount of CO2 and sunlight they receive and it also lowers plants' resistance to disease.
Smog and the Economy
  • Health: It is estimated that smog costs Ontario $1 billion dollars annually to cover health costs, hospital visits and absenteeism. Also, smog is related decreasing productivity in the workplace. When suffering and loss of life are taken into consideration, Ontario spends upwards of $10 billion annually on smog-related cases alone.

  • Agriculture: Smog can reduce crop yields by 15-20% and can cost Ontario up to $70 million annually due to damage to crop production.

  • Tourism: It is predicted that smoggy areas will be adversely affected by the tourism sector as smog levels increase. Smog makes places aesthetically unappealing and brings discomfort to people.

Factors Affecting Smog
  • Weather: Smog occurs on days that are hot, sunny, dry and windless. The sun reacts with the pollutants to form smog and the heat intensified the effects of smog. Wind allows smoggy air to disperse and therefore cause less harm, and rain can wash smog out from the air.

  • Seasons/Time of day: Related to the weather, summertime is hotter and sunnier than the wintertime and therefore most smog days occur between May and September. Smog is worse during the day because ozone cannot occur when it is dark out (however, particulate matter can exist equally at any time of day).

  • Geography: Smog levels are worse in urban areas and valleys than rural places and mountains, and also change depending on if the location is upwind or downwind from areas of high pollution.

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