What is air pollution?

Air pollution is made up of tiny particles and chemicals in the air that pose major hazards to both our health and the environment. Although numerous air pollutants have been associated with significant excess morbidity and mortality such as nitrogen oxide, ozone, and carbon monoxide, it is the effects of particulate matter (PM2.5) that has the strongest link with health outcomes. These are fine particles and droplets in the air that are 2.5 microns or less in width, around 3% of the diameter of a human hair. These particles present real health hazards as they are small enough to travel deep into the respiratory tract and into the lungs.

What causes air pollution?

There are various causes of air pollution. Outdoor and indoor sources both contribute to the growing amount of harmful particles and chemicals in the air, and this will continue to worsen unless limits are put on the practices that cause the pollution. A major outdoor source of  air pollution are exhaust emissions from cars, trucks, buses, construction vehicles and other motorized vehicles and machinery. The burning of fossil fuels and wood fires, along with oil and coal fires are also contributors to the pollution that exists in urban environments every day.

Natural occurrences are much more unavoidable, but also act as a source of pollution. Forest fires and natural gases that react with chemicals from sources such as power plants can sometimes pollute air many miles away from the original source due to winds and weather conditions at the time of reaction. Therefore, cities that don’t necessarily have high amounts of air pollution can still suffer the effects as a result of these chemicals and particles travelling to them from neighbouring areas.

Indoor sources of air pollution include tobacco smoke, cooking fumes, candles, oil lamps, indoor fireplaces and wood-burners, and fuel burning heaters.

If you live in an area that has particularly bad air pollution, you will notice that the air sometimes seems foggy and there is reduced visibility.  You may even be able to smell or taste the pollution.  This is caused by smog, and is a good indicator of whether or not the air pollution is worse than usual. Stagnant air and winds can both add to the amount of pollution. Stagnant air holds the air pollution in place and does not allow for new, fresher air to clear out the smog. Winds coming in to the city may bring in smog and pollution from neighbouring areas.

Most of the time, air pollution is invisible so you never know how much particulate matter you are exposed to and what harm it is doing to your body. However, there are ways to reduce your exposure to these harmful pollutants with some lifestyle adjustments,

How can I reduce my exposure to air pollution?

You can go indoors. This seems fairly simple because it is. While there are still harmful particulates indoors, most of the time you will be exposed to less inside than if you were breathing in the smoggy air outside.


  • Limit physical activity in high PM2.5 conditions. When there is a high percentage of pollutants in the air, cutting down on strenuous activity will reduce the amount of pollutants you breathe in. Physical activity will tire you out and your body will require more oxygen to function, by lessening physical activity, your body will be breathing in less air and therefore less PM2.5 particulates.


  • Change your route.  Studies have shown that exposure can be reduced by up to 50% simply by taking a side or back street.


  • Wear a mask. If the air pollution is very high, you might want to wear a face mask to cover your mouth and nose. A good mask should filter out most harmful particulates.


  • Open windows. This may seem counter-intuitive but sometimes the air pollution indoors can be worse than outdoors.  Allowing air-flow by opening windows will reduce the concentration of PM2.5.


Sometimes you cannot help the city you live in, air pollution or not. You can however be aware of the causes and health implications that occur due to high air pollution. Monitoring the level of air pollution, particularly PM2.5 particulates, identifying when the levels present high risks, and being aware of practices that can reduce your exposure will help you understand and lessen the negative effects on your health.