Ambient Levels of Sulphur Dioxide

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Sulphur dioxide (SO2) belongs to a group of sulphur-containing gases called sulphur oxides (SOX). Representing most of the SOX released from human activities, SO2 is 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 sulphur oxide 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. 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 hourly SO2 concentrations.

National ambient levels of sulphur dioxide

In 2014, the national annual average concentration of SO2 was 1.3 parts per billion (ppb), a level similar to 2013.

Since 2000, a decreasing trend of 0.13 ppb per year has been detected. This trend was mainly due to reductions in sulphur oxide emissions in Canada and the United States, resulting from efforts to curb acid rain and ambient particulate matter. Efforts included the implementation of federal regulations on sulphur content in fuels.

Sulphur dioxide concentrations, Canada, 2000 to 2014

Line chart of the national annual average concentrations of sulphur dioxide - Long description below

Long description

The line chart shows the national annual average concentrations of sulphur dioxide from 2000 to 2014. A decreasing trend was detected over this period.

Data for this chart
Sulphur dioxide concentrations, Canada, 2000 to 2014
YearAnnual average concentration (parts per billion)
20003.8
20012.9
20022.8
20032.5
20042.3
20052.2
20062.2
20072.2
20082.0
20091.7
20101.5
20111.5
20121.4
20131.3
20141.3
Annual trend-0.13

Download data file (Excel/CSV; 838 B)

How this indicator was calculated

Note: The national annual average sulphur dioxide concentration indicator is based on the hourly concentrations recorded at 63 monitoring stations across Canada. The location of monitoring stations near emission sources may affect measured sulphur dioxide levels.
Source: Environment and Climate Change Canada (2016) National Air Pollution Surveillance Program.

Regional ambient levels of sulphur dioxide

In 2014, the annual average concentrations of SO2 in the air varied by region from 0.8 ppb in the Prairies and northern Ontario region to 2.4 ppb in southern Ontario. Concentrations of SO2 in 2014 were lower than in 2013 for Atlantic Canada and British Colombia, and higher or similar in the other three regions.

Since 2000, decreasing trends in SO2 concentrations were observed for all regions of Canada. Decreasing trends of 0.44 ppb and 0.25 ppb per year were detected for Atlantic Canada and the southern Quebec regions, respectively. Southern Ontario had a decreasing trend of 0.24 ppb per year, while decreasing trends of 0.07 ppb and 0.04 ppb per year were observed for the Prairies and northern Ontario region and British Columbia, respectively.

Regional sulphur dioxide concentrations, 2000 to 2014

Line chart of the annual regional average concentrations of sulphur dioxide - Long description below

Long description

The line chart shows the annual average concentrations of sulphur dioxide from 2000 to 2014 for five regions in Canada: Atlantic Canada, southern Quebec, southern Ontario, Prairies and northern Ontario, and British Columbia. Since 2000, decreasing trends were observed for all regions.

Data for this chart
Regional sulphur dioxide concentrations, 2000 to 2014
YearAtlantic Canada annual average concentration (parts per billion)Southern Quebec annual average concentration (parts per billion)Southern Ontario annual average concentration (parts per billion)Prairies and northern Ontario annual average concentration (parts per billion)British Columbia annual average concentration (parts per billion)
20005.94.55.61.42.5
20016.74.45.61.11.8
20025.74.35.21.61.9
20035.14.43.61.51.8
20044.24.13.61.51.7
20053.64.13.81.41.4
20063.13.43.31.42.0
20073.02.63.61.81.7
20081.52.63.11.42.0
20091.11.82.31.21.9
20100.81.62.10.91.7
20111.11.62.70.71.5
20121.81.82.20.61.6
20131.41.72.20.71.4
20141.11.72.40.81.3
Annual trend-0.44-0.25-0.24-0.07-0.04

Download data file (Excel/CSV; 1.49 KB)

How this indicator was calculated

Note: The annual average sulphur dioxide concentration indicator is based on the hourly concentrations recorded at 4 monitoring stations in Atlantic Canada, 8 in southern Quebec, 10 in southern Ontario, 18 in the Prairies and northern Ontario and 22 in British Columbia. The location of monitoring stations near emission sources may affect measured sulphur dioxide levels.
Source: Environment and Climate Change Canada (2016) National Air Pollution Surveillance Program.

Ambient levels of sulphur dioxide at monitoring stations

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

Related indicators

Other information

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