Ambient Levels of Sulphur Dioxide

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 SO2 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. SO2 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.

National ambient levels of sulphur dioxide

In 2012, the annual average concentration of sulphur dioxide (SO2) in outdoor air was 1.8 parts per billion (ppb) in Canada, 1% higher than in 2011. A declining trend was detected from 1998 to 2012, representing a concentration decrease of 67% (or an average decrease of 4.8% per year) over that period. The decrease observed for this indicator is mainly due to the reduction in SO2 emissions in Canada, resulting from efforts to curb acid rain and ambient particulate matter, and federal regulations on sulphur content in fuels.

Sulphur dioxide concentrations, Canada, 1998 to 2012

Sulphur dioxide concentrations, Canada, 1998 to 2012

Long Description

The line chart shows the average concentration of sulphur dioxide in the air in Canada from 1998 to 2012. In 2012, the annual average concentration of sulphur dioxide in outdoor air was 1.8 parts per billion in Canada, 1 percent higher than in 2011. A declining trend was detected from 1998 to 2012, representing a concentration decrease of 67 percent (or an average decrease of 4.8 percent per year) over that period.

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How this indicator was calculated

Note: The national SO2 indicator is based on the annual average of the daily concentrations recorded at 50 monitoring stations across Canada. Monitoring stations located close to major sources may have a great impact on the measured SO2 levels. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

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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 2012 was 1.8 parts per billion (ppb), or 24% higher than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 100% (or an average decrease of 7.1% per year) over that period. Emission reduction measures implemented at power plants in Atlantic Canada contributed substantially to this reduction of SO2 in the air.

Sulphur dioxide concentrations, Atlantic Canada, 1998 to 2012

Sulphur dioxide concentrations, Atlantic Canada, 1998 to 2012

Long Description

The line chart shows the average concentration of sulphur dioxide in the air in Atlantic Canada from 1998 to 2012. In 2012, the annual average concentration of sulphur dioxide in the air was 1.8 parts per billion, or 24 percent higher than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 100 percent (or an average decrease of 7.1 percent per year) over that period.

View data for this chart
How this indicator was calculated

Note: For Atlantic Canada, the SO2 indicator is based on the annual average of the daily concentrations recorded at four monitoring stations. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level. 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 concentrations.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

Southern Quebec

In southern Quebec, the annual average concentration of sulphur dioxide (SO2) in outdoor air for 2012 was 2.1 parts per billion (ppb), 25% higher than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 66% (or an average decrease of 4.7% per year) over that period. Emission reduction measures, implemented in southern Quebec at non-ferrous smelters and pulp and paper plants, contributed substantially to this reduction of SO2 in the air.

Sulphur dioxide concentrations, southern Quebec, 1998 to 2012

Sulphur dioxide concentrations, Southern Quebec, 1998 to 2012

Long Description

The line chart shows the average concentration of sulphur dioxide in the air in southern Quebec from 1998 to 2012. In 2012, the annual average concentration of sulphur dioxide in outdoor air was 2.1 parts per billion, 25 percent higher than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 66 percent (or an average decrease of 4.7 percent per year) over that period.

View data for this chart
How this indicator was calculated

Note: For southern Quebec, the SO2 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. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

Southern Ontario

In southern Ontario, the annual average concentration of sulphur dioxide (SO2) in outdoor air for 2012 was 2.2 parts per billion (ppb), or 20% lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 70% (or an average decrease of 5.0% per year) over that period. Emission reduction measures implemented for power plants and for the non-ferrous refining and smelting industry contributed substantially to this reduction of SO2 in the air.

Sulphur dioxide concentrations, southern Ontario, 1998 to 2012

Sulphur dioxide concentrations, Southern Ontario, 1998 to 2012

Long Description

The line chart shows the average concentration of sulphur dioxide in the air in southern Ontario from 1998 to 2012. In 2012, the annual average concentration of sulphur dioxide in outdoor air was 2.2 parts per billion, or 20 percent lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 70 percent (or an average decrease of 5.0 percent per year) over that period.

View data for this chart
How this indicator was calculated

Note:  For southern Ontario, the SO2 indicator is based on the annual average of the daily concentrations recorded at 12 monitoring stations. Major sources located close to monitoring stations may have a great impact on the measured SO2 levels. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

Prairies and northern Ontario

In the Prairies and northern Ontario, the annual average concentration of sulphur dioxide (SO2) in outdoor air for 2012 was 0.6 parts per billion (ppb), or 14% lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 68% (or an average decrease of 4.8% per year) over that period. Emission reduction measures implemented at power plants and oil and gas facilities contributed substantially to this reduction of SO2 in the air. More recently the closure of the Flin Flon smelter also contributed to the decrease.

Sulphur dioxide concentrations, Prairies and northern Ontario, 1998 to 2012

Sulphur dioxide concentrations, Prairies, 1998 to 2012

Long Description

The line chart shows the average concentration of sulphur dioxide in the air in the Prairies and northern Ontario from 1998 to 2012. In 2012, the annual average concentration of sulphur dioxide in outdoor air was 0.6 parts per billion, or 14 percent lower than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 68 percent (or an average decrease of 4.8 percent per year) over that period.

View data for this chart
How this indicator was calculated

Note: For the Prairies and northern Ontario, the SO2 indicator is based on the annual average of the daily concentrations recorded at six monitoring stations. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

British Columbia

In British Columbia, the annual average concentration of sulphur dioxide (SO2) in outdoor air for 2012 was 1.7 parts per billion (ppb), or 4% higher than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 27% (or an average decrease of 1.9% per year) over that period. Emission reduction measures implemented on sulphur content in fuels and reduced emissions in the petroleum products industry contributed to this reduction of SO2 in the air.

Sulphur dioxide concentrations, British Columbia, 1998 to 2012

Sulphur dioxide concentrations, British Columbia, 1998 to 2012

Long Description

The line chart shows the average concentration of sulphur dioxide in the air in British Columbia from 1998 to 2012. In 2012, the annual average concentration of sulphur dioxide in outdoor air was 1.7 parts per billion, or 4 percent higher than in 2011. A declining trend was detected from 1998 to 2012, representing a decrease of 27 percent (or an average decrease of 1.9 percent per year) over that period.

View data for this chart
How this indicator was calculated

Note: For British Columbia, the SO2 indicator is based on the annual average of the daily concentrations recorded at 17 monitoring stations. A trend line is displayed and a trend is reported only when a statistically significant trend is detected at the 95% confidence level.
Source: Environment Canada (2014) National Air Pollution Surveillance program (NAPS).

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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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