British Columbia has a network of air quality monitoring stations that measure sulphur dioxide and other air contaminants. This indicator reports on the concentration of sulphur dioxide from two reporting periods, 2021-2023 and 2022-2024. The data are reported as two metrics: an annual metric based on one year of data, and a 1-hour metric based on three consecutive years of data. These metrics are compared against the Canadian Ambient Air Quality Standards to determine achievement and to define colour-based management levels. CAAQS were established by the Canadian Council of Ministers of the Environment in 2012 as a key element of the Air Quality Management System that collaboratively and comprehensively manages air quality in Canada. The maps and figures below primarily show results from the 2022-2024 period. Detailed findings from the 2021-2023 analysis can be found in the PDF version of the indicator available here (PDF 2MB)

• Sulphur dioxide is a colourless gas with a pungent odour at higher concentrations. The largest sources of SO₂ in B.C. include the oil and gas sector, the pulp and paper sector, and metal smelters. Marine vessels and off-road diesel vehicles are also significant sources of SO₂ (Air Pollutant Emissions Inventory Report 2026).
• Sulphur dioxide can be harmful to humans and the environment. Short-term exposure to elevated SO₂ can cause difficulty breathing for asthmatics. The long-term impacts of SO₂ exposure are not well understood. Increased SO₂ in the environment can affect vegetation and aquatic ecosystems through acid rain deposition (Health Canada 2016).

The map and charts below show the levels of SO₂ at individual monitoring stations, and the assigned management levels for each of B.C.’s air zones. Each point shown on the map represents an air quality monitoring station with colours that describe the management level. The colour of each region is the management level assigned for the entire air zone, with values based on the station with the highest level of SO₂. The results shown here are based on the 2022–2024 reporting period. The four management levels and the recommended actions are: (1) green (actions for keeping clean areas clean); (2) yellow (actions for preventing air quality deterioration); (3) orange (actions for preventing Canadian Ambient Air Quality Standard exceedance); and (4) red (actions for achieving air zone Canadian Ambient Air Quality Standard). Each management level corresponds to actions that become more rigorous as the level of SO₂ approaches CAAQS. Suggested actions for each management level are outlined in the Guidance Document on Air Zone Management. More information on management levels can be found below.

While the Guidance Document outlines the types of actions that may be taken at each management level, a range of actions are implemented across British Columbia to improve air quality. These actions may include provincial programs, regulatory measures, and community-level initiatives that address local sources of air pollution and vary by region. Examples of actions include programs to reduce emissions (such as wood smoke reduction initiatives), controls on open burning, and local or regional efforts to manage air quality. Summaries of actions and activities undertaken in B.C. can be found in Air Zone Management Response reports, which describe provincial and local efforts to improve air quality in different regions.

Tip: Click or tap on an air zone or monitoring station to see details on the status of sulphur dioxide levels for the 2022-2024 reporting period.

Tip: See Table 6.1 in the Guidance Document on Air Zone Management for more information about the suggested actions for each color/management level in the map below.

• 2021‑2023: sulphur dioxide levels met the Canadian Ambient Air Quality Standards at 94 percent of assessed monitoring stations in B.C. There are two standards for SO₂: an annual standard and a 1-hour standard (see sidebar). The annual standard was met at 36 of the 36 stations (100%) for which valid data was obtained, while the 1‑hour standard was met at 34 of the 36 stations (94%) with sufficient data for analysis.
• 2022‑2024: sulphur dioxide levels met the Canadian Ambient Air Quality Standards at 94 percent of assessed monitoring stations in B.C. The annual standard was met at 37 of the 37 stations (100%) for which valid data was obtained, while the 1‑hour standard was met at 34 of the 36 stations (94%) with sufficient data for analysis.
• In both periods, sulphur dioxide levels met the annual Canadian Ambient Air Quality Standard in six of B.C.’s seven air zones, and met the 1‑hour Standard in five air zones. The Coastal, Central Interior, Georgia Strait, Northeast, and Lower Fraser Valley air zones met both the SO₂ annual and 1-hour standards. The Southern Interior air zone exceeded the 1-hour standard. Currently, there are no air monitoring stations in the Northwest air zone.