Canada's Air

AQMS was built on a foundation of collaboration, accountability and transparency. Industry, non-governmental and Indigenous organizations worked with governments to develop AQMS, they continue to monitor implementation of AQMS and participate in its ongoing development and improvement, including actions to address mobile sources.

Monitoring and public reporting are critical to transparency, accountability and the effective implementation of the system. Provinces and territories, with assistance from the federal government, are responsible for monitoring air pollutants in their air zones and for reporting to their constituents about air quality and actions taken to implement AQMS. Provinces and territories will produce annual air zone reports that include information on achievement of the CAAQS, air quality issues and trends, and the air management level in each air zone.

Canadian Ambient Air Quality Standards (CAAQS) are developed as a key element of the Air Quality Management System to drive improvement of air quality across Canada. CAAQS have been developed for nitrogen dioxide (NO₂), sulphur dioxide (SO₂), fine particulate matter (PM_2.5) and ozone (O₃). Ongoing reviews of the CAAQS help ensure they reflect the latest scientific information. The CAAQS are established as air quality objectives under the Canadian Environmental Protection Act, 1999.

To assist with air quality management, provinces and territories have defined smaller geographic areas called air zones that divide their jurisdiction and that have unique air quality characteristics. These characteristics may include pollutant sources, topography, meteorological patterns, population density and other potential factors that influence ambient air concentrations.

Base-level Industrial Emissions Requirements (BLIERs) are intended to ensure that all significant industrial sources in Canada, regardless of where facilities are located, meet a good base-level of performance. BLIERs are quantitative or qualitative emissions requirements proposed for new and existing major industrial sectors and some equipment types. BLIERs are focused on nitrogen oxides (NO_x), sulphur dioxide (SO₂), volatile organic compounds (VOCs) and particulate matter (PM).

Six regional airsheds cover all of Canada and allow for coordination and joint action in resolving issues involving the movement of air pollutants across provincial/territorial boundaries and international borders. These airsheds were developed taking larger scale issues, such as the movement of large air masses, typical long-term meteorological conditions, topography and air zone boundaries into consideration.

AQMS includes work to address emissions from mobile sources. The work builds on the existing range of federal, provincial and territorial initiatives aimed at reducing emissions from the transportation sector.

Particulate matter (PM), a major component of smog, consists of airborne particles in solid or liquid form. PM may be classified as primary or secondary, depending on the process that led to its formation. Primary PM is emitted directly into the atmosphere from a source, such as a smokestack or exhaust pipe, or from wind-blown soils or vehicle traffic on a dirt road. Secondary PM is formed in the atmosphere through a series of chemical and physical reactions involving gases such as sulphur oxides (SO_x) and nitrogen oxides (NO_x). PM exists in various sizes and the particles of most concern for human health are those with a diameter of less than 2.5 micrometres (PM_2.5).

Ground-level ozone (O₃), is a colourless, odourless and highly irritating gas that forms close to the Earth’s surface. O₃ is a major component of smog. In contrast to “primary” pollutants which are emitted directly into the atmosphere from a source, O₃ is considered a “secondary” pollutant because it is formed through complex chemical reactions between nitrogen oxides (NO_x) and volatile organic compounds (VOCs) in the presence of sunlight. While O₃ at ground-level is a significant environmental and health concern, approximately 10 to 40 kilometres above the Earth's surface, there is a beneficial layer of stratospheric ozone which shields the earth from harmful ultraviolet radiation. Ozone is also a short-lived climate pollutant and also contributes to climate change.

Nitrogen dioxide (NO₂) belongs to the oxides of nitrogen group of compounds (NO_x) that are formed primarily through the burning of fossil fuels. While transportation sources represent over half of all emissions, energy production and industrial processes also emit significant amounts of NO_x, mainly as Nitric Oxide (NO) and Nitrogen dioxide (NO₂). NO₂ at higher concentrations has a strong, harsh odour and can typically be seen over large cities as a brownish haze. Once formed, NO₂ can combine with water molecules in the air to form compounds like nitric acid and nitrous acid. Ultimately, these compounds fall to earth through precipitation (such as rain, snow and fog) where they contribute to the acidification and eutrophication of ecosystems.

Sulphur dioxide (SO₂) is a colourless gas that smells like burnt matches. It belongs to a group of sulphur-containing gases called sulphur oxides (SO_x). SO₂ is emitted when fossil fuels or raw materials containing sulphur are burned or used in an industrial process like metal ore smelting or electric power generation. It can also be produced in large quantities during extraction and processing of fossil fuels. SO₂ contributes to the formation of PM_2.5 and smog, and when combined with water molecules in the air, it can form compounds like sulfuric acid, which eventually falls to earth as acid rain, snow and fog.

Volatile organic compounds (VOCs) are organic chemicals that easily turn to vapour under normal atmospheric conditions. When VOCs are exposed to sunlight, complex chemical reactions occur with NO_x that lead to the production of O₃ and fine particulate matter (PM_2.5), two key components of smog. Smog is known to have adverse effects on human health and the environment. VOCs cover a wide range of chemicals including fumes from oil-based paint, household cleaning products, solvents and gasoline, as well as from some natural sources. Across Canada, the main human-related sources are related to the extraction of oil and gas, the use of paints and solvents, transportation, and home firewood burning.

Air emissions refer to the release of pollutants into the atmosphere from a source. A “source” can include industrial facilities, various types of transportation, home heating appliances and much more. Air emissions also come from natural sources, like forest fires and volcanoes. The quantity of emissions released from human activities vary depending on a number of factors, such as: changes in industrial output and processes, fuel types, pollutant reduction technologies and the economy.

Ambient air concentrations refer to the amount of pollutants in a defined volume of air. These are usually expressed in parts per billion by volume (ppb) for gases and in micrograms per meter cubed for particulate matter. Ambient air quality reporting only considers outdoor air, with air monitoring stations located mostly in, or near, large communities where exposure takes place. Ambient air concentrations reflect and respond to changes in the quantity of emissions released and to changes in meteorology (wind speed, wind direction, temperature, precipitation, etc.).

Health Effects - Short-term exposure to PM_2.5 can cause serious heart and lung outcomes like heart attacks, heart failure, stroke, and asthma attacks, as well as premature death. It can also result in hospital visits for cardiovascular and respiratory problems. Long-term exposure to PM_2.5 can cause premature death, and likely causes lung cancer and heart and lung diseases. There is limited evidence that long-term exposure to PM_2.5 may also cause neurological and developmental outcomes. Any level of exposure to PM_2.5 poses a risk to population health. Children, older adults, smokers, and people with underlying cardiovascular and respiratory disease (e.g., asthma) are at greater risk.

Environmental Effects - The impacts of PM_2.5 on the environment can vary depending on its chemical make-up. For instance, PM_2.5 often contains acidifying components that can cause changes to soil and water chemistry and may contain heavy metals or other toxic substances. These components can adversely impact animals and vegetation, leading to species and habitat loss. Other components in PM_2.5 may have a neutralizing effect on acidity. Deposition of PM_2.5 on leaves can reduce photosynthesis rates, decrease agricultural crop yields, and may change the absorption rate of other chemicals such as SO₂. PM_2.5 can stain and damage stone and other materials, impacting buildings, statues, and monuments. PM_2.5 also contributes to reduced visibility, which affects cities, airports, and wilderness areas, and can negatively impact tourism and the economy.

Health Effects - Short-term exposure to O₃ causes a range of respiratory symptoms and likely causes premature death. Some respiratory symptoms, like shortness of breath, airway injury, and reduced lung function, can result in hospital visits. There is limited evidence that short term O₃ exposure may also cause adverse cardiovascular outcomes, and that long-term exposure may cause changes in lung function in children, asthma development, respiratory mortality, and structural changes in the lungs. Any level of exposure to O₃ poses a risk to population health. Children, older adults, and people with underlying respiratory disease (e.g., asthma) are at greater risk.

Environmental Effects - O₃ is absorbed directly by plants through pores in their leaves. Once inside the plant, ozone can damage leaves, reduce photosynthesis rates, impair reproduction and decrease agricultural crop yields. This can reduce the variety of plants in an ecosystem and may contribute to forest decline in some parts of Canada. O₃ exposure is also known to degrade plastics. While mostly known for its adverse effects on health and the environment, O₃ is also a greenhouse gas that contributes to climate change.

Health Effects - Short-term exposure to NO₂ can cause adverse respiratory effects including reduced lung function, increased symptoms, and airway inflammation. It exacerbates respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD) and likely causes premature death. Long-term exposure to NO₂ likely causes adverse respiratory effects, and there is limited evidence that it may also cause cardiovascular, reproductive, and developmental effects as well as cancer and premature death. Any level of exposure to NO₂ poses a risk to population health. Children, older adults and people with underlying respiratory conditions (e.g., asthma and COPD) are at greater risk.

Environmental Effects - Direct exposure to NO₂, through absorption by leaves, can lead to lesions and dead tissue in plants, and to altered plant growth and yield. NO₂ (and other nitrogen oxides) may also react to produce other chemicals that impact the environment. These reactions include those with water and oxygen to form acid rain, which negatively affects soil and water. Other reactions produce an overabundance of nitrogen-based nutrients that adversely affect an ecosystem, such as through overgrowth of algae and plants in water bodies. NO₂ also contributes to the formation of PM_2.5 and O₃ and to reduced visibility, which affects cities, airports, and wilderness areas, and can negatively impact tourism and the economy.

Health Effects - Short-term exposure to SO₂ affects respiratory health, resulting in reduced lung function, increased respiratory symptoms, and airway inflammation. Effects can include increased hospital visits for respiratory causes. There is limited evidence that short-term exposure may also cause premature mortality, particularly in older adults. Children and people with underlying respiratory disease (e.g., asthma) are at a greater risk.

Environmental Effects - Direct exposure to SO₂, through absorption by leaves, can harm plants by interfering with photosynthesis and energy metabolism, and can cause decreased plant growth and yield. SO₂ may also react in the atmosphere or on surfaces to create sulphuric acid. Within the atmosphere, this quickly forms particulate sulphate (a component of PM_2.5). The deposition of SO₂ onto surfaces, through dry deposition or acid rain, may result in surface acidification, which can damage materials and structures, including objects of cultural importance like statues and monuments.

Health Effects - The health effects of individual VOCs depend on the chemical, and the level and duration of exposure. While some VOCs give off distinctive odours at higher levels, some are odourless. Many VOCs have little effect on health at levels typically measured outdoors. The health effects of individual VOCs can include irritation (eye, nose and throat), headaches, nausea, dizziness, fatigue, breathing problems and neurological effects. Long-term exposure to some VOCs, like benzene, can increase the risk of developing cancer. Children, older adults, pregnant people, and people with underlying health conditions (e.g., asthma or bronchitis) are at greater risk.

Environmental Effects - VOCs contribute to the formation of PM_2.5 and O₃, which are the main components of smog. Emitted as volatile gases, these chemicals react within the atmosphere that can result in the formation of organic aerosol (a component of PM_2.5). Reactions of VOCs may also result in the formation of highly reactive chemicals, which may alter the concentration of NO₂ and increase the formation of O₃.