Status of Ground-Level Ozone in B.C. (2018-2020)
British Columbia operates a network of air monitoring stations that measure ground-level ozone and other air pollutants. This indicator reports on the concentration of ground-level ozone from 2018-2020 and compares it to the Canadian Ambient Air Quality Standard established by the Canadian Council of Ministers of the Environment.
- Ground-level ozone is an air pollutant. While ozone in the Earth’s atmosphere occurs naturally, additional ozone at the ground level is a pollutant. It forms through chemical reactions involving nitrogen oxides and volatile organic compounds in the presence of sunlight.
- Ground-level ozone can be harmful to humans. Exposure to ground-level ozone (hereafter ozone) can reduce lung function and cause inflammation of airways, which can increase respiratory symptoms and aggravate asthma1. These effects are linked to more emergency room visits, hospitalizations, and absenteeism, and higher health care costs2.
The map below summarises the assigned management levels for ozone in B.C.'s air zones, as well as the levels of the pollutant at individual monitoring stations. It features stations with sufficient data to report for the 2018-2020 reporting period.
Tip: Click or tap on an air zone or monitoring station to see details on the status of ozone levels for the 2018-2020 reporting period.
Ground-Level Ozone: Canadian Ambient Air Quality Standard
Ozone levels are calculated using a statistical form called the ozone metric. The Canadian Ambient Air Quality Standard for ozone is 62 parts per billion (ppb).
The ozone standard is achieved when ozone metrics are ≤62 ppb.
- Ozone levels met the Canadian Ambient Air Quality Standard at 45 of the 45 B.C. ozone monitoring stations. Ozone levels (see box below) from the 45 stations ranged from 38 to 58 parts per billion (ppb). Ozone levels were ≤ 50 ppb at 25 reporting stations (56%). No station reported ozone levels > 62 ppb.
- Ozone levels met the Canadian Ambient Air Quality Standard in six of B.C.’s seven air zones. The ozone level for an air zone is the highest ozone level reported from monitoring stations within the air zone. Currently, there are no air monitoring stations in the Northwest Air Zone.
- Ozone levels are used to set management levels for each air zone. Four management levels (green, yellow, orange, and red) are each associated with a suite of actions that become more rigorous as ozone levels approach the Canadian Ambient Air Quality Standard.
What is an Air Zone?
British Columbia is divided into seven air zones. These are areas with similar air quality characteristics, issues, and/or trends.
More about the Canadian Ambient Air Quality Standard for Ozone:
- The statistical form of the Canadian Ambient Air Quality Standard ozone metric is the 3-year average of the annual 4th-highest daily maximum 8-hour rolling average concentration.
- The ozone metric for an air zone is the highest ozone metric reported from monitoring stations within the air zone.
- Criteria for data completeness and sufficiency of the ozone metric are described in the Guidance Document on Achievement Determination: Canadian Ambient Air Quality Standards for Fine Particulate Matter and Ozone (2012).
- Air quality monitoring stations with at least two years of valid data from 2018-2020 were included in this indicator. Visit Current Air Quality Data for a complete list of currently active air quality monitoring stations across B.C.
Canada-wide Air Quality Management System
The Air Quality Management System is Canada's approach for protecting air quality. Under the Air Quality Management System, provinces and territories monitor, report and manage local air quality within air zones, with the goal of continuously improving air quality and keeping pollutants below the Canadian Ambient Air Quality Standards.
- There are seven air zones in British Columbia: Coastal, Georgia Strait, Lower Fraser Valley, Southern Interior, Central Interior, Northeast and Northwest.
- The Air Zone Management Framework defines management levels based on the highest ozone level reported from monitoring stations within the air zone. The four management levels 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). Actions for each management level are detailed in the Guidance Document on Air Zone Management (2019) (PDF). Air zone management levels are preferentially based on stations with 3 complete years of data.
- The Lower Fraser Valley was assigned to an orange management level; the Central Interior, Southern Interior, Georgia Strait, and Northeast air zones were assigned to a yellow management level; and the Coastal air zone was assigned to a green management level. Currently, there are no air monitoring stations in the Northwest air zone.
More about the Air Quality Management System management levels:
- There are cases when an air zone does not achieve a given Canadian Ambient Air Quality Standard because of sources over which jurisdictions have little or no control over, such as those from transboundary flows and exceptional events, like wildfires.
- Before assigning management levels, jurisdictions have the option to adjust their air zone metric values by removing external influences. These arrangements aim to ensure that jurisdictions are responsible for managing only the emissions they can control.
- Wildfire influences were determined for 8 monitoring sites in B.C. on a total of 9 days for the 2018-2020 reporting period. The daily concentrations for these days were removed from the calculations of management levels, but this resulted in no changes in management levels for ground-level ozone.
The methods used to develop this indicatorincluding procedures, data requirements, and calculation of the ozone metricare detailed in the Guidance Document on Achievement Determination: Canadian Ambient Air Quality Standards for Fine Particulate Matter and Ozone (2012) published by the Canadian Council of Ministers of the Environment.
R package and code: We have developed an R package to facilitate the calculation of air quality metrics according to the Canadian Ambient Air Quality Standards. Download the 'rcaaqs' package from GitHub. The source code for repeating the analysis presented on this page is also available on GitHub.
References and Other Useful Links
- Read individual Air Zone reports on the achievement of the Canadian Ambient Air Quality Standards for ground-level ozone and fine particulate matter in B.C.
- Learn more about the implementation of the Air Quality Management System in British Columbia
- Access B.C.'s real-time data on air pollutants and find locations of all provincial air monitoring stations in B.C.
- BC Lung Association's BC State of the Air Reports
- Canadian Environmental Sustainability Indicators: Air Indicators
- 1United States Environmental Protection Agency. February 2013. Integrated Science Assessment of Ozone and Related Photochemical Oxidants (600/R-10/076F)
- 2Willey, J., N. Gilbert, and N. Lyrette. 2004. Human health effects of ozone: Update in support of the Canada-wide standards for particulate matter and ozone (Revised version). Working paper prepared for Canadian Council of Ministers of the Environment. Health Canada. Ottawa, Ontario.
*By accessing these datasets, you agree to the licence associated with each file, as indicated in parentheses below.
- Indicator Summary Data: BC Ground-Level Ozone Canadian Ambient Air Quality Standards 2018-2020 (Licence: Open Government Licence - British Columbia)
- B.C. Ground-level Ozone Hourly Data & Air Monitoring Station Locations (Licence: Open Government Licence - British Columbia)
- B.C. Air Zones (Licence: Open Government Licence - British Columbia)
Updated August 2022
Suggested Citation: Environmental Reporting BC. 2022. Status of Ground-Level Ozone in B.C. (2018-2020). State of Environment Reporting, Ministry of Environment and Climate Change Strategy, British Columbia, Canada.