About air quality

Air quality is defined as the state of the air around us.

Air pollution is a broad term applied to any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere.

Air quality relates to the concentration of air pollutants in the air we breathe and/or have an impact on the environment. In other words, what is the quality of the air we breathe? Air pollution can harm the environment and/or the health of Canadians. Elderly persons, young children and persons with respiratory illness are the most likely to be impacted by poor air quality.

The primary air pollutants monitored and studied are referred to as Criteria Air Contaminants. Air pollutants defined as criteria air contaminants are sulphur dioxide (SO2), nitrogen oxides (NOx), volatile organic compounds (VOCs), particulate matter (PM), carbon monoxide (CO), gaseous ammonia (NH3) and ground level ozone (O3). Ozone and particulate matter are the most concerning because they cause negative health effects at any concentration. Ozone and particulate matter are by-products of chemical reactions between the other primary air pollutants. Particulate matter is also released directly to the air.

Air quality is impacted by emissions from natural sources, industry, transportation, and cross border movement. Industrial and construction activities contribute to SO2 and PM emissions. Transportation activities contribute to NOx and VOC emissions. Movement of air pollution from outside of Canada can lead to elevated levels of certain pollutants within the country.

Additional types of air pollutants of concern include:

  • Persistent Organic Pollutants (POPs) such as certain pesticides, polychlorinated biphenyls (PCBs), and certain flame retardants containing bromine, are organic compounds which remain in the environment for long periods of time and are capable of travelling long distances. POPs are concerning because they can enter the food supply, bioaccumulate and have significant human health and environmental impacts.
  • Heavy Metals such as mercury, cadmium and lead also have significant adverse impacts on human health.  The Arctic region, including the Canadian Arctic, is a major receptor of some heavy metals released from sources in other regions of the world. Particulate matter in smog is often a carrier of heavy metals.
  • Toxic substances include a wide range of pollutants such as benzene and polycyclic aromatic hydrocarbons, which are identified under the Canadian Environmental Protection Act 1999 and can contribute to air quality issues.
  • Short-Lived Climate Pollutants, including black carbon, tropospheric ozone and ground-level ozone, which have a short atmospheric lifetime and impact both air quality and climate change. 

Why is air quality important?

According to the World Health Organization, air pollution is one of the most significant global human health risks. In Canada, over 3 million citizens suffer from respiratory illness. Furthermore, as of November 2015, over 30% of Canadians lived in communities where outdoor levels of ozone exceeded newly established ambient air standards. Local air pollutant levels are affected by factors like emissions sources, weather conditions, and topography.

Ecosystem health is negatively impacted by air pollution as well. Soil, forest and water ecosystems have a threshold above which acid deposition and pollution loads harm the environment. The health and productivity of some crops may be harmed by ground-level ozone. Heavy metal pollutants, such as mercury, impact wildlife health by adversely affecting habitat and food quality.

There are air pollutants that while having a negative impact on human health and ecosystems, also contribute to climate change. Short-lived climate pollutants are among these pollutants having environmental and socioeconomic effects. 

Looking forward

While progress towards better air quality has been made, there are still ongoing issues. For example, higher ozone levels persist in the Great Lakes and the eastern parts of Canada, levels of acidic deposition (“acid rain”) continue to exceed the ecosystem’s ability to cope in some parts of Canada, and particulate matter emissions are increasing due to construction and road traffic.

At Environment and Climate Change Canada, we work to inform the public on the state of their air quality. Our scientists carry out comprehensive research, modelling and monitoring activities. These activities:

The aim of ECCC air quality science and research is to identify, track and understand air quality and related emerging issues in support of cleaner air and healthier communities for the benefit of Canadians.

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