Air Quality

On this page you can learn about outdoor air quality and smog and indoor air quality.

Outdoor air quality and smog

Click here for the Region of Waterloo Outdoor Air Quality Info Booklet.

Air pollution

Air pollution is made up of gases, liquids, and particles that can be harmful to humans and the environment. Pollutants come from a wide range of sources, including vehicle exhaust, industrial processes, energy generation, home and building heating, wood burning (learn more about the health effects of wood smoke here), and construction dust.

Most of the air pollution that we live with on a day-to-day basis is created by transportation and industry, through the production of vehicle exhaust and industrial emissions.

Although transboundary air pollution (pollution that travels across geographical borders) is responsible for a lot of Ontario's smog, a significant amount is generated locally.

Several of these sources of air pollution also generate greenhouse gases that contribute to climate change.


Smog, the grey-brown haze that sometimes accompanies hot days, is a term used to describe a harmful mixture of air pollutants. It is usually formed by a combination of ground level ozone and small particles, as well as gases, road and construction dust, sunlight, and heat.

Health effects

The impact of air pollution and smog on health will vary depending on factors such as:

  • The concentration of pollutants
  • The frequency and duration of exposure
  • A person's age and general health status

Peaks in air pollution can:

  • Lead to coughing and wheezing, and make it harder to breathe
  • Irritate the eyes, nose and throat
  • Aggravate existing lung and heart conditions, such as asthma, chronic bronchitis, emphysema and angina

People with heart and lung problems, older adults, and children are at higher risk of health effects. These may also occur in healthy people, particularly those who work and exercise outdoors. This is because when people do strenuous work or physical exercise, they inhale air deeper into the lungs and mostly through the mouth (instead of using he filtering function of the nose).

How to reduce your risk from smog

To protect yourself from the potential adverse health effects of smog:

  • You need to be aware of when air quality is poor and take action to reduce your exposure to it.
  • Plan ahead by checking the local air quality forecast or the daily Air Quality Health Index (AQHI) reading, especially when smog days are more likely to occur from April to September.
  • Tailor your activities accordingly.

If there is a Special Air Quality Statement or Smog and Air Health Advisory


  • Avoid or reduce strenuous physical outdoor activities, especially during the late afternoon - reschedule or relocate activities to an indoor, cool environment if possible
  • Avoid or reduce exercising (e.g. cycling or jogging) near areas of heavy traffic, especially during rush hour
  • Reduce your activity level if you begin to cough and wheeze, feel chest tightness, and/or have trouble breathing
  • Stay indoors in a cool environment if possible
  • Call your doctor or go to the nearest hospital if you experience significant breathing problems
  • Check up regularly on neighbours, friends, and older family members, especially those who have health issues or live alone

People with respiratory problems, asthma, and heart disease:

Remain indoors in a cool environment, avoid strenuous outdoor activity, and seek immediate attention if symptoms get worse. Also talk to your doctor about additional ways to protect your health when smog levels are high. 


Indoor air quality

Working, playing, eating, and sleeping; most of us spend 90 per cent of our time indoors. Since healthy lungs thrive on unpolluted air, keeping the air clean in your home is important for good health. This is particularly true for people with allergies or a lung disease such as asthma, bronchitis or emphysema.

Sources of indoor air pollution

Inadequate ventilation can increase indoor pollutants by not bringing in enough outdoor air to dilute emissions from indoor sources and by not carrying indoor air pollutants out of the home.

Many pollutants found in the home result from our own actions. Tobacco smoke is a major contributor to indoor air pollution. Other sources include hair sprays, cleaning products, paints and solvents.

Storing chemicals such as gasoline, pesticides and chemicals used in hobbies or crafts can also affect the air quality in your home as they release gases or particles into the air.

High temperature and humidity levels may increase the concentration of some pollutants and the resulting discomfort.

Indoor air hazards you should know about

  • Mould (moisture and biological contaminants, mildew and dust mites)
  • Carbon Monoxide (and other combustion products)
  • Formaldehyde
  • Radon
  • Household products and furnishings
  • Chemicals to get rid of household pests
  • Clothes brought home from a dry cleaner
  • Asbestos
  • Lead
  • Particulates
  • Environmental tobacco smoke
  • Remodelling byproducts

Health effects of poor indoor air quality

  • Dizziness
  • Nausea
  • Allergic reaction
  • Eye and skin irritation
  • Respiratory tract irritation

If you experience any of these symptoms, note whether they disappear when you are away from home, or improve when you increase indoor ventilation. Pay attention to the time and place the symptoms occur: they may be triggered by something inside your home.

Reducing air pollution in your home

Eliminate, then ventilate. The most effective way to control indoor air pollutants is to eliminate possible sources from your home. Improve the ventilation by opening a window and bringing cleaner air inside.

If eliminating and ventilating are not sufficient, consider purchasing an air purifier or air cleaner. These small appliances can be purchased at most hardware and home-building stores. Be sure to look for one which is HEPA-certified.

Other things you can do:

  • Do not allow smoking in the home.
  • Ensure that furnaces, water heaters and fireplaces are checked regularly.
  • Do not store chemicals in the home.
  • Choose natural products that do not emit polluting gases.
  • Keep temperature and humidity at proper levels.

Note: If you suspect that hazardous building materials were used in your home, such as asbestos, formaldehyde, lead-based paint, etc., do not attempt to remove or disturb them yourself. Refer to Health Canada's website for guidance on dealing with hazardous household products.