Pollution & air quality
Outdoor air quality
Air pollutants and your health
We are getting better at tracking air pollutants and recognizing how they affect our health. Below is a description of some common air pollutants, where they come from, and how they affect our health.
The first part of this page talks about the main ingredients in smog, and the second part talks about other kinds of air pollutants.
The main ingredients in smog, and their health effects
Smog is made up of many air pollutants. The main ones are ground-level ozone and fine particulate matter. Smog can also contain sulphur dioxide, nitrogen dioxide, total reduced sulphur, and carbon monoxide.
Ground-level ozone (O3):
The ozone found high in the earth’s atmosphere is called “good ozone” because it helps protect us from the sun's rays. But ozone at the ground level is not good for human health. Ground-level ozone is not emitted directly into the air, but forms when nitrogen oxide and volatile organic compounds (VOCs) from vehicle exhaust, factory emissions and other sources react with sunlight.
It’s called the “bad ozone” because if you breathe it in, it can cause health problems. Ground-level ozone usually peaks between noon and 6 p.m. during the summer months.
Health effects of ground-level ozone:
- worsening symptoms for people with asthma, COPD and other lung diseases, and for people with cardiovascular (heart) disease
- swollen, irritated airways
- irritation to your eyes, nose and throat
- coughing, wheezing
Over time, ozone can cause permanent lung damage.
Sources of ground-level ozone
- burning fossil fuels (gas, oil or coal) for industry and transportationconsumer products (paints, wood laminates)
- natural sources (plants, trees, lightning)
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Fine particulate matter (PM)
Fine particulate matter is a broad name given to particles of liquids and solids that pollute the air. These particles come in different sizes and are made of different things.
PM 2.5 is particulate matter that is very small (2.5 microns or less – that’s about the width of human hair). PM 2.5 can be breathed deeply into your lungs and will stay there, causing health problems. PM 2.5 can stay in the air longer and travel farther than larger particles.
Health effects of fine particulate matter:
- coughing or sneezing
- irritation in your eyes, throat, and lungs
- wheezing and breathing problems in people with asthma, COPD, and other lung diseases
- cardiovascular health problems, including heart attacks in people with certain pre-existing heart diseases
Sources of fine particulate matter:
- vehicle exhaust
- road dust from paved and unpaved roads
- wood stoves, fireplaces, and oher kinds of wood burning
- forest fires
Sulphur dioxide (SO2)
Sulphur dioxide is a colourless gas that smells like burnt matches. It is one of the main ingredients in acid rain. Sulphur dioxide, combines with volatile organic chemicals (VOCs) and sunlight, creates ground-level ozone, the main ingredient in smog.
Health effects of SO2:
- irritation in your nose and throat
- breathing problems
- new cases of lung disease
- worsening symptoms in people with asthma, COPD, and other long-term lung diseases
- worsening cardiovascular (heart) disease
- changes in the lung's natural defences
Sources of SO2:
- fossil fuels burned in petroleum refineries
- pulp and paper mills
- steel mills
- electricity generating plants, including coal-fired power plants
- non-iron ore smelters
- diesel vehicles
- volcanoes and hot springs
Nitrogen Oxides (NOx)
Nitrogen oxide is a reddish-brown gas that smells foul.
Health effects of NOx:
- can lower your resistance to lung infections
- can cause shortness of breath and irritate the upper airways, especially in people with lung disease, such as asthma and chronic obstructive pulmonary disorder (COPD)
Sources of NOx:
- burning fossil fuels in motor vehicles, homes, and industries
- oil, gas, and coal-fired power plants
- metal production
- forest fires, lightning and decaying vegetation
Total reduced sulphur compounds (TRS)
Total reduced sulphur compounds are mixtures of gases that smell like rotten eggs. The main ingredients in total reduced sulphur compounds (TRS) are hydrogen sulphide (H2S), methyl mercaptan (CH3S-H), dimethyl sulphide (CH3-S-CH3) and dimethyl disulphide (CH3-S-S-CH3).
Health effects of TRS:
Sources of TRS:
- the steel industry
- pulp and paper mills
- sewage treatment facilities
Carbon monoxide (CO)
Carbon monoxide is an odourless, tasteless, colourless gas. At high levels, carbon monoxide is poisonous.
Health effects of carbon monoxide:
- shortness of breath
- slower reflexes and reduced perception
- at high levels: seizures, unconsciousness, coma, respiratory failure and death.
Sources of carbon monoxide:
- burning fossil fuels in vehicles
- metal production
- emissions from heating devices (gas heaters, etc.)
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Other air pollutants and their health effects
Volatile Organic Compounds (VOCs)
Volatile organic compounds are gases in the vapours of gasoline, solvents, oil-based paint. In the presence of sunlight and warm temperatures, VOCs react with nitrogen oxides to form ground-level ozone, the main ingredient in smog.
Health effects of VOCs:
- eye, nose and throat irritation
- loss of coordination
- can worsen lung, heart and other existing health problems when they combined with nitrogen oxide to form ground-level ozone
Sources of VOCs
- burning gasoline
- upstream oil and gas production
- residential wood burning
- evaporation of liquid fuels and solvents
- new carpets and furniture
Polycyclic aromatic hydrocarbons (PAHs)
These are a group of approximately 10,000 compounds. Most PAHs are from incomplete burning of carbon-containing materials like oil, wood, garbage or coal. PAHs may be attached to dust or ash.
Health effects of PAHs:
- lung irritation
- contact with skin may cause redness, blistering, and peeling
- Some PAHs have caused cancer in laboratory animals when they breathed air containing them (lung cancer), ingested them in food (stomach cancer), or had them applied to their skin (skin cancer)1.
Sources of PAHs:
- automobile and other exhausts
- fireplaces and woodstoves
- cigarette smoke
- coal and oil-fired power plants
- waste incinerators
- steel and asphalt production
- aluminum smelting
- carbon black production
- wood preservation
- forest and brush fires
- volcanic eruptions
- decaying organic matter
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