Climate Change and Public Health Factsheets

Climate change, air contaminants, and your health

Nothing could be more fundamental to your health than the quality of the air you breathe. In Canada, air pollution and aeroallergens have significant implications for health. Health impacts include lung disease, heart disease and lung cancer.

It is now well-established by researchers that climate change could result in a deterioration of several aspects of air quality, including:

  • an increase in air pollution levels—pollutants such as ozone and particles of different sizes (particulate matter, or PM),
  • more frequent or severe air pollution and heat episodes—which together, have an even greater impact
  • increased emissions from the natural environment—such as from fires and dust.
  • Increase in aeroallergen levels—substances in the air, like pollen, that can cause allergic reactions

Who is at risk?

Air quality is most likely to cause health problems in vulnerable groups, such as:

  • older adults
  • children
  • pregnant women
  • people with chronic diseases (e.g. asthma, chronic lung disease, heart disease and diabetes)
  • people of lower socio-economic status—living conditions may expose them to higher levels of pollution and they may not be able to avoid exposure during extreme heat/pollution episodes.

Air pollution

Ground-level ozone

Ground-level ozone, a major component of smog, is created when gases in the environment react in the presence of heat and sunlight.

Researchers predict that, because ground-level ozone and weather are so closely linked, climate change will cause higher average ozone concentrations, more frequent peak ozone periods and longer summers which can increase summer ozone periods.

Health effects

Short-term exposure to ground-level ozone, over hours, days or weeks, can result in:

  • respiratory symptoms such as cough or throat irritation
  • reduced lung capacity;
  • worsening of lung conditions, resulting in emergency room visits, admission to hospital or even death.

Long-term exposure to ground-level ozone, over years or decades, can cause death from breathing problems.

Particulate matter

Particulate matter is a mixture of tiny particles of different sizes which enter the air from a variety of natural and man-made sources, including dust, fires, vehicles and industry. The impact of climate change on particulate matter is less well understood than ozone. It is known that rain can reduce particulate matter from the air. As precipitation patterns are harder to predict there is uncertainty on how climate change will impact particulate matter in Canada and therefore more research is needed. However, research has shown that climate change could increase frequency and intensity of forest fires, which would result in an increase in particulate matter.

Health effects

Short-term exposure to particulate matter can result in:

  • respiratory symptoms such as cough or throat irritation
  • reduced lung capacity;
  • worsening of heart and lung conditions, resulting in emergency room visits, admission to hospital or even death.

Long-term exposure to particulate matter can result in:

  • reduced lung capacity;
  • more cases of lung disease , such as asthma and chronic obstructive pulmonary disease (COPD);
  • more premature births and low birth weight babies;
  • impaired lung development in children; and
  • death from lung and heart disease as well as lung cancer.

Combined effects of heat and air pollution

Extreme heat can impact health by causing, for example, heat stroke, but when heat is combined with air pollution, the negative health effects are compounded:

  • People breathe more quickly when it's hot and therefore breathe in more air that can be polluted.
  • Extreme heat also changes the body's ability to handle toxins. For example, during the very warm summer in Europe in 2003, heat and air pollution caused 35,000 excess deaths, mostly among the elderly.
    • In the Netherlands more than a third of deaths were caused by ozone exposure.
    • In England and Wales, 20-40% of deaths were due to air pollution.
  • Large cities may experience higher temperatures due to the built environment (e.g. roads, buildings) which trap the heat, also known as heat-island effect.


Aeroallergens are pollen and spores in the air that cause allergic responses.

Research suggests that climate change will increase allergens in the air and related allergic diseases as warmer weather and milder winters can result in increased pollen production in plants. More frequent thunderstorms may also put more pollen into the air. Furthermore, higher carbon dioxide levels, due to climate change, can increase plant growth and pollen production.

A longer pollen season could mean:

  • higher pollen levels ;
  • longer allergy seasons ; and
  • greater exposure to aeroallergens.

Health effects

Aeroallergens cause allergic responses—most often allergic rhinitis (e.g. hay fever), asthma and eczema. Exposure to higher concentrations of aeroallergens may cause more severe allergies. In Canada nearly 50% of children suffer from hay fever and over 20% have been diagnosed with asthma.

Indoor Air Quality

As people spend approximately 90% of their time indoors, the quality of the indoor environment is an important consideration for health. Indoor environments can be contaminated by chemical and  organic pollutants that migrate from outdoors or that result from gas stoves and other indoor sources, such as building materials, pets, radon, and environmental tobacco smoke.

With climate change, any changes in the outdoor levels of pollutants or allergens could affect indoor levels. Extreme weather conditions associated with climate change may lead to risks of infiltration of water into indoor spaces (flooding) and associated growth of mold or bacteria.

Flooding may cause building materials to breakdown and lead to off-gassing of chemicals.

In addition, any measures implemented in buildings or homes to reduce energy use in buildings, such as lowering ventilation rates may cause higher exposures to pollutants emitted from indoor sources.

There is a need to be aware of the potential health risks related to climate change and the indoor environment, especially for vulnerable populations such as children, elderly and those with compromised immune systems.

For more information about how to reduce levels of indoor contaminants please visit the Health Canada Indoor Air Quality website.

What you can do

You can lower your exposure to air pollution when you:

  • Avoid exercise when outdoor air quality is poor or consider exercising indoors—because active people take in more air when they are active they may inhale more pollutants from the air.
  • Avoid highly polluted areas where possible—try to minimize exposure to areas with higher air pollution, such as high-traffic areas.
  • Be aware of potential hazards in your indoor environment and try to reduce exposures.
  • Consider using HEPA filters— to remove particles from indoor air — For example, one community affected by forest fires lowered indoor smoke pollution by 65% using HEPA filters.
  • Talk to your family doctor or health care professional if you have concerns about your health or health of a family member.

You can monitor outdoor air quality

  • The Air Quality Health Index from Health Canada and Environment Canada has real-time air quality ratings and forecasts. It gives health messages based on air quality monitoring. It is available in cities across Canada where air quality monitors are found.
  • People can use current Air Quality Health Index readings and forecasts to plan their outdoor activities for periods when health risks are lower.

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