1. Home  
  2. Health  
  3. Advice and prevention  
  4. Health and environment  
  5. The health effects of air pollution

The health effects of air pollution


When air quality is poor or when a smog warning (yellowish fog comprising gas and particles) is in effect, it means that there is a high amount of pollutants in the air.

The main outdoor air pollutants are:

  • Fine particles (PM2.5), which are tiny particles that can penetrate deeply into the respiratory system
  • Ozone (O3)
  • Sulphur dioxide (SO2)
  • Nitrogen dioxide (NO2)
  • Carbon monoxide (CO)

Among other sources, these pollutants come from:

  • Motor vehicles
  • Factories
  • Heating systems (oil, propane, wood, etc.)
  • Forest fires

Air pollutants can affect the entire population’s health. Some people, however, are more sensitive than others to pollutants and more likely to experience adverse effects.


People who breathe polluted air can develop a variety of symptoms. These vary according to each person’s sensitivity to air pollution. The main short-term symptoms are:

  • Eye irritation
  • Wheezing or difficulty breathing
  • Irritation and inflammation of the respiratory tract (coughing)
  • Shortness of breath, especially during physical activity
  • Aggravation of existing asthma, heart and lung conditions

The severity of these symptoms depends on a person’s health and the level of pollution to which he or she is exposed. The improper use of certain medications can make symptoms of pollution worse.

It is important to note that symptoms can be the result of factors other than air pollution. These other factors include:

When to consult

You should consult a doctor as soon as possible if you have any of the following symptoms:

  • Chest tightness
  • Pain when breathing deeply
  • Difficulty breathing despite not having engaged in physical activity

If you have questions regarding your health, call Info-Santé 811.


People who breathe polluted air regularly over several years can develop certain health problems:

  • Chronic lung diseases, such as chronic bronchitis
  • Cardiovascular diseases, meaning the heart and blood vessels disorders
  • Lung cancer

Breathing polluted air can also worsen symptoms for people already suffering from chronic illnesses, especially respiratory or cardiac diseases. In rare cases, this can lead to hospitalization or premature death.

Risk factors

The risks of experiencing discomfort due to air pollution increase:

  • When outdoor air quality is poor
  • When a smog warning is in effect
  • When the heat is oppressive
  • During strenuous physical activity or long outings, when people breathe a large amount of air

People at risk

Some people are more at risk of showing symptoms if exposed to poor quality air or smog:

  • People with respiratory problems, such as:
    • Asthma
    • Emphysema
    • Chronic bronchitis
    • Other chronic obstructive pulmonary disease, etc.
  • People with heart disease, such as angina
  • People who have had a heart attack
  • People with a chronic illness, such as diabetes
  • Pregnant women
  • Babies and children younger than 5 years of age
  • Seniors
  • People who do intense outdoor exercise or who work outdoors regularly. These people can breathe a large quantity of polluted air

Protection and prevention

Get into the habit of verifying the air quality in your region. When it is poor or a smog warning is in effect, you can take certain precautions. Read Preventing the health effects of air pollution, which offers information on how to ensure your well-being and that of your loved ones.

Last update: June 4, 2024


Was the information on this page useful to you?
General notice

You have questions or require additional information?

Please contact Services Québec