Ambient Levels of Ground-Level Ozone
- National ambient levels of ground-level ozone
- Regional ambient levels of ground-level ozone
- Ambient levels of ground-level ozone at monitoring stations
- Related indicators and other information
National ambient levels of ground-level ozone
Ozone (O3) in the upper atmosphere (10 to 50 km above the earth’s surface) protects the earth from the sun’s harmful ultraviolet radiation. In the lower part of the atmosphere (at ground level), O3 is harmful to human health. It can induce breathing problems, reduce lung function and aggravate asthma and other lung diseases. O3 is one of two major components of smog, the other being fine particulate matter (P2.5). O3 can damage vegetation and materials such as rubber. O3 is not directly emitted but formed in the atmosphere when precursor gases such as nitrogen oxides (NOx) and volatile organic compounds (VOC) react in sunlight.
In 2010, the average concentration of ground-level O3 in the outdoor ambient air was 38.2 parts per billion (ppb) in Canada, about 3% higher than the previous year. The increase is mainly due to 2010 being a warmer and drier year than 2009 and to transboundary pollution from the United States. A rising trend was detected from 1990 to 2010, representing a concentration increase of 10% over that period.
Ground-level ozone concentrations, Canada, 1990 to 2010
Note: The national ground-level O3 indicator is based on the population-weighted annual average of the 8-hour daily maximum concentrations recorded at 91 monitoring stations across Canada during the warm season (April 1 to September 30). A trend line is reported only when a statistical trend is detected at the 90% confidence level.
Source: Environment Canada (2012) The National Air Pollution Surveillance (NAPS) program; the Canadian Air and Precipitation Monitoring Network (CAPMoN); and Statistics Canada (2012) 2011 Census of Population.
Regional ambient levels of ground-level ozone
Atlantic Canada
In Atlantic Canada in 2010, the average concentration of ground-level ozone (O3) in ambient air was 33.8 parts per billion (ppb), 5% higher than in 2009. No significant increasing or decreasing trend was detected between 1990 and 2010.
Ground-level ozone concentrations, Atlantic Canada, 1990 to 2010
Note: The ground-level ozone (O3) indicator is based on the population-weighted annual average of the 8-hour daily maximum concentrations recorded at 7 monitoring stations across Atlantic Canada during the warm season (April 1 to September 30). A trend line is displayed and a trend reported only when a statistical trend is detected at the 90% confidence level.
Source: Environment Canada (2012) The National Air Pollution Surveillance (NAPS) program; the Canadian Air and Precipitation Monitoring Network (CAPMoN); and Statistics Canada (2012) 2011 Census of Population.
Southern Quebec
In southern Quebec, the average concentration of ground-level ozone (O3) in the air for 2010 was 36.8 parts per billion (ppb), 8% higher than in 2009. No significant increasing or decreasing trend was detected between 1990 and 2010.
Ground-level ozone concentrations, southern Quebec, 1990 to 2010
Note: The ground-level ozone (O3) indicator is based on the population-weighted annual average of the 8-hour daily maximum concentrations recorded at 25 monitoring stations across southern Quebec during the warm season (April 1 to September 30). A trend line is reported only when a statistical trend is detected at the 90% confidence level.
Source: Environment Canada (2012) The National Air Pollution Surveillance (NAPS) program; the Canadian Air and Precipitation Monitoring Network (CAPMoN); and Statistics Canada (2012) 2011 Census of Population.
Southern Ontario
In southern Ontario, the average concentration of ground-level ozone (O3) in ambient air for 2010 was 43.2 parts per billion, or 6% higher than in 2009. A rising trend was detected from 1990 to 2010, representing a concentration increase of 11% over that period.
Ground-level ozone concentrations, southern Ontario, 1990 to 2010
Note: The ground-level ozone (O3) indicator is based on the population-weighted annual average of the 8-hour daily maximum concentrations recorded at 31 monitoring stations across southern Ontario during the warm season (April 1 to September 30). A trend line is reported only when a statistical trend is detected at the 90% confidence level.
Source: Environment Canada (2012) The National Air Pollution Surveillance (NAPS) program; the Canadian Air and Precipitation Monitoring Network (CAPMoN); and Statistics Canada (2012) 2011 Census of Population.
Prairies and northern Ontario
In the Prairies and northern Ontario, the average concentration of ground-level ozone (O3) in ambient air was 36.2 parts per billion, or 6% lower than in 2009. A rising trend was detected from 1990 to 2010, representing a concentration increase of 11% over that period.
Ground-level ozone concentrations, Prairies and northern Ontario, 1990 to 2010
Note: The ground-level ozone (O3) indicator is based on the population-weighted annual average of the 8-hour daily maximum concentrations recorded at 13 monitoring stations across the Prairies and northern Ontario during the warm season (April 1 to September 30). A trend line is reported only when a statistical trend is detected at the 90% confidence level.
Source: Environment Canada (2011) The National Air Pollution Surveillance (NAPS) program; the Canadian Air and Precipitation Monitoring Network (CAPMoN); and Statistics Canada (2011) 2011 Census of Population.
British Columbia
In British Columbia, the average concentration of ground-level ozone (O3) in ambient air was 30.3 parts per billion in 2010, or 5% lower than in 2009. A rising trend was detected from 1990 to 2010, representing a concentration increase of 6% over that period.
Ground-level ozone concentrations, British Columbia, 1990 to 2010
Note: The ground-level ozone (O3) indicator is based on the population-weighted annual average of the 8-hour daily maximum concentrations recorded at 15 monitoring stations across British Columbia during the warm season (April 1 to September 30). A trend line is reported only when a statistical trend is detected at the 90% confidence level.
Source: Environment Canada (2012) The National Air Pollution Surveillance (NAPS) program; the Canadian Air and Precipitation Monitoring Network (CAPMoN); and Statistics Canada (2012) 2011 Census of Population.
Ambient levels of ground-level ozone at monitoring stations
The National Air Pollution Surveillance (NAPS) program provides detailed information on air pollutant concentrations from monitoring stations across Canada. Canadian Environmental Sustainability Indicators (CESI) provide access to this indicator through an online interactive map. With the CESI interactive map, you can drill down to local areas and obtain details on O3 concentrations at specific monitoring stations.
Related indicators
- Ambient Levels of Fine Particulate Matter
- Ambient Levels of Sulphur Dioxide
- Ambient Levels of Nitrogen Dioxide
- Ambient Levels of Volatile Organic Compounds
- International Comparison: Urban Air Quality
Other information
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