Basic chemistry

Smog Effects Definition Meaning Causes

Causes and effects of smog

How does smog affect our health?

Smog causes and effects
Smog causes and effects

The term smog refers to a toxic mixture of gases and particles that can often be observed in the air as a haze. It is associated with several adverse effects on health and the environment.

The two main pollutants that make up smog are tropospheric ozone and particulate matter. High smog densities are often associated with the summer season due to the presence of sunlight and high temperatures. However, smog is an issue that occurs all year, winter smog (because of the contribution of particles instead of ozone) is a serious concern when stagnant air accumulates pollutants from heating wood and the use of vehicles.

Health –

Smog is known to contribute to thousands of premature deaths nationwide each year, as well as more frequent hospitalizations and medical consultations, and hundreds of thousands of lost days at work and at school.

Environmental problems associated with smog include deterioration of plants and structures, and problems of visibility and haze (mainly attributable to fine particles).

Reducing the effects of air pollution on the health of Canadians and their environment is one of the key commitments made by the Government of Canada. Smog and your health
Smog can cause damage to your heart and lungs – even if you can not see it or smell it in the air around you.

When we hear the word “smog,” most of us think of this chemical “soup” that is often seen over urban areas in the form of a brownish-yellow haze. However, smog is not always visible. It is actually a mixture of air pollutants including gases and particles that are too small to see. Although smog is often produced in large cities, its concentration can be just as high, if not more, in suburban and rural communities.

We must protect our health from damage that may be caused by smog.

Possible effects on health:

Since smog is a mixture of air pollutants, its impact on your health depends on a number of factors, including:

levels and types of pollutants in the air
your age and your general health
meteorological factors
the duration of the exhibition
where you live
Smog can irritate the eyes, nose, and throat, or it can make heart or lung problems more serious. It can also lead to premature death.

People at risk are those who suffer from heart and lung problems. Many of these problems are common in older adults and make them more susceptible to the negative effects of air pollution.

Children may be more sensitive to the effects of this type of pollution because their breathing apparatus is still developing and they generally have an active lifestyle. Even healthy young adults breathe less well on days when the air is more polluted.

The health effects of ground-level and particulate matter (PM) ozone are also of concern. Some studies suggest that long-term exposure to PM may increase the risk of premature death and possibly lung cancer.

Ozone studies indicate that even after entering the lungs, ozone can continue to cause damage, even if you are feeling well. That’s why the federal government, including Health Canada, is working to reduce the risks to your health. The areas of particular concern for ozone in Canada are:

Windsor-Quebec corridor (Ontario and Quebec)
The Lower Fraser Valley (British Columbia)
South Atlantic Region
Types and sources of air pollution
Scientists who study smog are more concerned with the following types of air pollution:

Type: Particulate matter ( PM ).

This is the name given to microscopic particles that pollute the atmosphere. Their size and chemical composition vary.

Industrial emissions and vehicle emissions, road dust, agriculture, construction, and wood combustion.
Type: Ozone at ground level.

This gas results from a chemical reaction that occurs when certain pollutants combine with sunlight. Ground-level ozone should not be confused with the sky’s ozone layer, which protects us from ultraviolet rays.


Ground-level ozone comes mainly from the burning of fossil fuels used for transportation and industry. Since ground-level ozone formation is dependent on solar radiation, ozone levels are highest during the summer, with peaks occurring between 12:00 and 18:00.
We are mainly concerned with the following pollutants:

Type: Sulfur dioxide


Comes from coal-fired power plants and foundries other than those that process iron ore.

Type: Carbon monoxide


Primarily from the combustion of carbon fuels ( eg motor vehicle exhaust).
Reduce your risks
Here’s how you can reduce your exposure to smog and its potential effects on your health:

Read about the Air Quality Health Index (AQHI) index in your community, especially in the smog season (April to September) and choose your activities accordingly;
When the level of smog is high, avoid exhausting outdoor exercise, especially in the afternoon, when ground-level ozone reaches its maximum, and choose indoor activities;
Avoid exercising near areas with heavy traffic, especially during peak hours; and
If you have heart or lung disease, follow your doctor’s advice on what to do when the level of smog is high.
To help reduce overall smog levels in the air:

If possible, use public transit instead of your vehicle, and work on foot or by bicycle when the smog level is not too high;
Replace petrol-powered vehicles and machinery with other means. For example, use a rowboat or sailboat rather than a motorboat – or a manual mower rather than a gas lawnmower;
Consider energy efficiency when buying a vehicle. Maintain it regularly and correctly;
Minimize your energy consumption at home. Learn about alternative energy resources;
Do not burn leaves, branches or other garden waste;
Consider being part of a citizens’ committee to promote your right to breathe cleaner air in your community; and
Spend time talking to your kids about the importance of a sustainable lifestyle.
The role of Health Canada
Health Canada’s research on the effects of smog on health has been instrumental in developing national air quality standards for particulate matter and ground-level ozone. These standards are an important step in reducing the effects of smog on your health.

Health Canada will continue to study the short- and long-term effects of exposure to pollutants that produce smog. These studies will result in additional standards and guidelines to protect Canadians from the harmful effects of smog.

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