Air quality is a local and regional issue affected by human activities, weather, and topography. The quality of the air we breathe affects our health. It also affects Canada's wildlife habitat and agricultural and forest yields. One important type of air pollution is smog, which mostly consists of ground-level ozone and microscopic airborne particles, known as particulate matter (PM). Ground-level ozone and over half of PM are produced through the reaction of other pollutants in the air, called precursor gases. Nitrogen oxides (NOX) and volatile organic compounds (VOC) are two of the key precursor gases. Precursor gases come from human activities, such as burning fossil fuels in motor vehicles, smelters, homes, thermal power plants and other industries and the evaporation of solvents, as well as natural sources.
The emissions of NOX and VOC have remained relatively constant for the past 15 years. More work needs to be done to reduce emissions of these gases from all human sources.
Precursor gases can adversely affect human health directly and indirectly through the creation of smog-forming ground level ozone and PM. At high levels, NOX can impair lung function and irritate the respiratory system. NOX also contributes to the formation of acid rain. Some VOC are carcinogenic. Many of the same sources that emit NOX and VOC emissions are also responsible for toxic and greenhouse gas emissions.
PM is measured in three categories: particles less than 2.5 micrometres (PM2,5), particles less than 10 micrometres (PM10), and total particles. Of the three, PM2.5 is the most dangerous to human health because it is inhaled the most deeply into the lungs.
Most PM2.5 emissions come from burning fuels for:
Road dust and agriculture also contribute significantly.
The ambient concentrations of ground-level ozone have not changed significantly. Eastern Canada experiences higher levels of ground-level ozone than Western Canada. Considerable variation in air pollution trends is observed among cities. Weather conditions have a strong influence on the year to year variations in ozone with higher concentrations under hotter conditions.
Smog can irritate the eyes, nose and throat and cause coughing and wheezing. Poor air quality can also aggravate heart and lung diseases. Children, the elderly, and people with respiratory diseases are particularly at risk. However, poor air quality affects everyone.
As part of the Clean Air Strategy, in 2001 the Government of Canada committed $120 million toward new measures that accelerate action on clean air. These new measures are detailed in the Ozone Annex to the 1999 Canada/US Air Quality Agreement. The focus is on promoting cleaner vehicles and fuels, reducing emissions from industry, and improving pollutant monitoring and reporting. In cooperation with the provinces and territories, the Government of Canada has endorsed Canada-wide standards for PM2.5, ground-level ozone, and other air pollutants.
Although there have been improvements in the levels of airborne pollutants, many parts of Canada continue to experience poor air quality.
Sources:
1. Environment Canada. 2002. Criteria Air Contaminants Division,
Pollution Data Branch. Updated NOx and VOC data will be available
in 2003.
2. Environment Canada. 1999. “1995 Criteria Air Contaminant
Emissions for Canada (tonnes)”. Available from
http://www.ec.gc.ca/pdb/ape/ape_tables/canada95_e.cfm.
3. Environment Canada. 2002. National Air Pollution Surveillance
Network. Adapted by the Environmental Technology Centre.
4. Environment Canada. 2002. National Air Pollution Surveillance
Network. Adapted by the Environmental Technology Centre.
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