Ambient Levels of Sulphur Dioxide

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Sulphur dioxide (SO2) is a gas emitted when a fuel or raw material containing sulphur is burned or used in industrial processes, such as metal ore smelting. The major sources of SOX emissions in Canada are the combustion of fuel for electricity generation and heating, and processes in both the non-ferrous smelting and refining industry and the oil and gas industry. Sulphur dioxide emissions contribute to acid deposition and are a major precursor to fine particulate matter (PM2.5). High concentrations of SO2 can adversely affect the respiratory systems of humans and animals and can damage vegetation.

The annual average SO2 concentration indicators are based on the annual average of the SO2 daily concentrations.

National ambient levels of sulphur dioxide

In 2013, the annual average concentration of sulphur dioxide (SO2) in the air in Canada was 1.4 parts per billion (ppb), 9% lower than in 2012. The decreasing trend of 0.1 ppb per year detected from 1999 to 2013 is mainly due to the reduction in SO2 emissions in Canada, resulting from efforts to curb acid rain and ambient particulate matter and from the implementation of federal regulations on sulphur content in fuels.

Sulphur dioxide concentrations, Canada, 1999 to 2013

Line chart

Long description

The line chart shows the national annual average concentrations of sulphur dioxide in Canada from 1999 to 2013.

Data for this chart
Sulphur dioxide concentrations, Canada, 1999 to 2013
YearAnnual average concentration
(parts per billion)
19993.8
20003.8
20013.0
20022.8
20032.5
20042.3
20052.2
20062.3
20072.1
20082.0
20091.7
20101.5
20111.5
20121.5
20131.4

Download data file (Excel/CSV; 773 B)

How this indicator was calculated

Note: The national annual average SO2 concentration indicator is based on the annual average of the daily concentrations recorded at 62 monitoring stations across Canada. Monitoring stations located close to major sources may have a great impact on the measured SO2 levels.
Source: Environment and Climate Change Canada (2015) National Air Pollution Surveillance (NAPS) program.

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Regional ambient levels of sulphur dioxide

Atlantic Canada

In Atlantic Canada, the annual average concentration of sulphur dioxide (SO2) in the air in 2013 was 1.2 ppb, or 17% lower than in 2012. Emission reduction measures implemented at power plants in Atlantic Canada contributed substantially to the decreasing trend of 0.5 ppb per year detected from 1999 to 2013 for ambient SO2.

Sulphur dioxide concentrations, Atlantic Canada, 1999 to 2013

Line chart

Long description

The line chart shows the annual average concentrations of sulphur dioxide in Atlantic Canada from 1999 to 2013.

Data for this chart
Sulphur dioxide concentrations, Atlantic Canada, 1999 to 2013
YearAnnual average concentration
(parts per billion)
19996.8
20005.9
20016.7
20025.6
20035.1
20044.1
20053.6
20063.1
20073.1
20081.5
20091.1
2010no data
20111.4
20121.5
20131.2

Download data file (Excel/CSV; 857 B)

How this indicator was calculated

Note: For Atlantic Canada, the annual average SO2 concentration indicator is based on the annual average of the daily concentrations recorded at four monitoring stations. At least three stations are required to report a concentration value for a year. There is no value for 2010 because there were only two stations with reported concentrations.
Source: Environment and Climate Change Canada (2015) National Air Pollution Surveillance (NAPS) program.

Southern Quebec

In southern Quebec, the annual average concentration of sulphur dioxide (SO2) for 2013 was 1.8 ppb, 13% lower than in 2012. Emission reduction measures, implemented in southern Quebec at non-ferrous smelters and pulp and paper plants, and the closure of a petroleum refinery contributed substantially to the decreasing trend of 0.2 ppb per year detected from 1999 to 2013 for SO2.

Sulphur dioxide concentrations, southern Quebec, 1999 to 2013

Line chart

Long description

The line chart shows the annual average concentrations of sulphur dioxide in southern Quebec from 1999 to 2013.

Data for this chart
Sulphur dioxide concentrations, southern Quebec, 1999 to 2013
YearAnnual average concentration
(parts per billion)
19994.3
20004.1
20014.4
20024.0
20034.2
20043.9
20053.9
20063.3
20072.6
20082.6
20092.1
20101.9
20111.7
20122.1
20131.8

Download data file (Excel/CSV; 784 B)

How this indicator was calculated

Note: For southern Quebec, the annual average SO2 concentration indicator is based on the annual average of the daily concentrations recorded at 10 monitoring stations. Major sources located close to monitoring stations may have a great impact on the measured SO2 levels.
Source: Environment and Climate Change Canada (2015) National Air Pollution Surveillance (NAPS) program.

Southern Ontario

In southern Ontario, the annual average concentration of sulphur dioxide (SO2) for 2013 was 2.2 ppb, the same level as in 2012. Emission reduction measures implemented at power plants, notably the continued phasing-out of coal power generation, and in the non-ferrous refining and smelting industry contributed substantially to the decreasing trend of 0.3 ppb per year detected from 1999 to 2013 in SO2.

Sulphur dioxide concentrations, southern Ontario, 1999 to 2013

Line chart

Long description

The line chart shows the annual average concentrations of sulphur dioxide in southern Ontario from 1999 to 2013.

Data for this chart
Sulphur dioxide concentrations, southern Ontario, 1999 to 2013
YearAnnual average concentration
(parts per billion)
19996.0
20005.6
20015.7
20025.2
20034.1
20043.6
20053.8
20063.7
20073.6
20083.1
20092.3
20102.1
20112.7
20122.2
20132.2

Download data file (Excel/CSV; 786 B)

How this indicator was calculated

Note: For southern Ontario, the annual average SO2 concentration indicator is based on the annual average of the daily concentrations recorded at 11 monitoring stations. Major sources located close to monitoring stations may have a great impact on the measured SO2 levels.
Source: Environment and Climate Change Canada (2015) National Air Pollution Surveillance (NAPS) program.

Prairies and northern Ontario

In the Prairies and northern Ontario, the annual average concentration of sulphur dioxide (SO2) in the air was 0.7 ppb in 2013, or 5% higher than in 2012. Emission reduction measures implemented at power plants and oil and gas facilities contributed substantially to a decreasing trend of 0.05 ppb per year detected from 1999 to 2013.

Sulphur dioxide concentrations, Prairies and northern Ontario, 1999 to 2013

Line chart

Long description

The line chart shows the annual average concentrations of sulphur dioxide in the Prairies and northern Ontario from 1999 to 2013.

Data for this chart
Sulphur dioxide concentrations, Prairies and northern Ontario, 1999 to 2013
YearAnnual average concentration
(parts per billion)
19991.3
20001.4
20011.1
20021.2
20031.1
20041.2
20051.0
20061.0
20071.0
20080.9
20090.9
20100.8
20110.6
20120.6
20130.7

Download data file (Excel/CSV; 709 B)

How this indicator was calculated

Note: For the Prairies and northern Ontario, the annual average SO2 concentration indicator is based on the annual average of the daily concentrations recorded at 17 monitoring stations.
Source: Environment and Climate Change Canada (2015) National Air Pollution Surveillance (NAPS) program.

British Columbia

In British Columbia, the annual average concentration of sulphur dioxide (SO2) for 2013 was 1.6 ppb, or 5% lower than in 2012. Emission reduction measures implemented on sulphur content in fuels and reduced emissions in the petroleum products industry contributed to the decreasing trend of 0.04 ppb per year detected from 1999 to 2013 in SO2.

Sulphur dioxide concentrations, British Columbia, 1999 to 2013

Line chart

Long description

The line chart shows the annual average concentrations of sulphur dioxide in British Columbia from 1999 to 2013.

Data for this chart
Sulphur dioxide concentrations, British Columbia, 1999 to 2013
YearAnnual average concentration
(parts per billion)
19992.3
20002.5
20012.0
20021.9
20031.8
20041.8
20051.5
20062.1
20071.8
20082.1
20092.2
20101.8
20111.6
20121.7
20131.6

Download data file (Excel/CSV; 683 B)

How this indicator was calculated

Note: For British Columbia, the annual average SO2 concentration indicator is based on the annual average of the daily concentrations recorded at 20 monitoring stations.
Source: Environment and Climate Change Canada (2015) National Air Pollution Surveillance (NAPS) program.

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Ambient levels of sulphur dioxide at monitoring stations

The National Air Pollution Surveillance (NAPS) program measures air pollutant concentrations at monitoring stations across Canada. The Canadian Environmental Sustainability Indicators (CESI) provide this information through an interactive indicator map. With the CESI interactive map, you can drill down to sulphur dioxide (SO2) concentrations at specific monitoring stations.

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Other information

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