Air Pollution:

Air Pollution is a broad issue, but Environment Canada has distilled the issue down to three separate pollutants: Smog, Acid Rain and Indoor Air Pollution. Several factors, including our land use patterns and behaviours, and the transboundary movement of air pollutants across distances (eg. From the US to Canada), influence the rate at which Canadian skies are exposed to pollutants.(i)

A. Smog:
According to Environment Canada, Smog refers to a noxious mixture of gases and particles that most commonly appears as a haze in the air. There are two primary pollutants in smog: ground-level ozone (O3) and particulate matter (PM). Quite often smog is associated with Canada’s hot summer months, however, it is a year-round problem. Winter smog differs slightly from the summer smog we have come to expect in the months of July and August in that it is a direct result of particulate matter contributions rather than ground-level ozone.(ii)

• Ground-Level Ozone (O3):
A gas that forms just above the earth’s surface. It is produced when two primary pollutants, or reactive organic substances including nitorgen oxides (NOx) and volatile organic compounds (VOCs), react in the presence of sunlight and stagnant air. This, in turn, qualifies (O3) as a secondary pollutant.(iii)

• Particulate Matter (PM):
Consists of airborne particles in solid or liquid form. PM is emitted at the emissions source in particle form. For example, the smokestacks of an electrical power plant, or a recently tilled field subject to wind erosion.

• Nitrogen Oxides (NOx):
About 95 per cent of Nitrogen Oxide comes from human activity – the burnng of coal, gasoline and oil in vehicles, homes, industries and powerplants.(iv) (NOx) is comprised of two gases: Nitrogen monoxide (NO) and Nitrogen Dioxide (NO2), and is produced by the breakdown of Nitrogen gas (N2). However, extremely high temperatures need to be applied during this process. The most common means of breaking this strong bond (triple) between both Nitrogen atoms is the combustion process in a car engine. Vehicles operate at a high enough temperature to break the Nitrogen bond and, as a direct result, (NOx) is released into the atmosphere in the form of exhaust.

• Volatile Organic Compunds:
Carbon-containing gases and vapours such as gasoline fumes and solvents. Many individual VOCs are known or suspected of having direct toxic effects on humans, ranging from carcinogenesis to neurotoxicity.(v)

• Nuetrotoxixity:
Described as a change in the structure and function of one’s nervous system following the exposure to a chemical agent. Neurotoxic chemicals and heavy and organic metals attack the immune system. They slowly destroy the central nervous system (CNS), and the peripheral nervous system (PNS) by targeting organs such as the liver, brain, kidneys, etc.(vi)



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Sources of NOx, Source: Green Ontario
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Sources of VOCs, Source: Green Ontario

















• Issues:
According to Health Canada, approximately 5,900 premature deaths occur annually as a direct result of air pollution and it continues to be a major health risk. Air pollution is linked to illnesses such as asthma, heart disease and respiratory disease.

B. Acid Rain:
Acid deposition is a general term that takes into consideration more than just acid rain. It is primarily the result of emissions of sulphur dioxide (SO2) and nitrogen oxides (NOx) that can be transformed into dry or moist secondary pollutants such as sulphuric acid (H2SO4), ammonium nitrate (NH4NO3) and nitric acid (HNO3) as they are emitted into the atmospohere over distances of hundreds, and even thousands, of kilometres.(vii)



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Acid Rain Cyle, Source: HowStuffWorks
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SO2 emissions in Canada and the Uniteed States, Source: Environment Canada




















• Issues:
Although Canada has met its domestic and international commitments on acid rain sensitive ecosystems in almost 800,000 square kilometers in southeastern Canada – an area the size of France and the United Kingdom combined – will receive harmful levels of acid rain. As a result, an estimated 95,000 lakes in southeastern Canada will remain acidified.(viii) Not only are Canada’s lakes susceptible to the harsh side-effects to acid rain, visible effects to Canada’s forests are now becoming more recognizable. There is evidence of increased defoliation, tree mortality, and nutrient losses in forest soils. Preliminary modeling shows that annual forest growth in eastern Canada is estimated to decrease by 10% when critical loads* are exceeded.(ix)

Finally, on a more human level, SO2 emissions also transform in the air into tiny sulphate particles that penetrate deep into the human lung. Recent evidence shows that sulphate particles are associated with increased premature mortality, emergency room visits, asthma symptom days, bronchitis, and other respiratory diseases. Any SO2 emission reductions achieved to combat acid rain will also result in lower levels of these particulates.(x)

*Critical Loads: The “critical load” is a measure of how much pollution an ecosystem can tolerate, in other words, the threshold above which pollutant load harms the environment.(xi)



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Air Pollution Health Effects Pyramid, Source: Environment Canada


The air pollution health effects pyramid is a diagrammatic presentation of the relationship between the severity and frequency of health effects, with the mildest and most common effects at the bottom of the pyramid, e.g., symptoms, and the least common but more severe at the top of the pyramid, e.g., premature mortality. The pyramid demonstrates that as severity decreases, the number of people affected increases.(xii)

C. Indoor Air Pollution:
Sources of indoor air pollutants can be broken down into two simple categories: Biological and Chemical.

  • Bioligical Pollutants: Living organisms (i.e. bacteria, dust mites and mold)
  • Chemical Pollutants: Gases and particles that come from combustion appliances, tobacco smoke, household and personal care products, various building materials and outdoor air.(xiii)

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Indoor Air Pollution, Source: U.S. Environmental Protection Agency


Regulations: Municipal, Provincial and Federal

1. Canadian Environmental Protection Act (CEPA)
2. Canada-Wide Standards (CWS)
3. National Ambient Air Quality Objectives (NAAQOs)
4. CEPA-National Advisory Committee (NAC)

Works Cited:

All information, if otherwise stated, is provided by Environment Canada.