James Bay Sulphur Dioxide Monitoring Program - Health Risk Guide

Sulphur Dioxide Monitoring

The purpose of this guide is to help the public understand what increased sulphur dioxide (SO2) levels may mean for their health.

How to use this guide:

  1. Check the actual hourly SO2 concentration reported on the Ministry of Environment's BCAirQuality.ca website. (Click on the dot for Victoria/Saanich on the map then choose Victoria James Bay.)
  2. Refer to the table below to see if you should modify your outdoor activities.

Note: The Sulphur Dioxide Health Risk Guide does not replace specific advice provided to individuals by their health care professionals.

Protecting Your Health from Sulphur Dioxide

Sulphur Dioxide Concentration






0 - 35 ppb
(0 to ~90 µg/m3)

Air quality is satisfactory, SO2 concentrations pose little or no risk

Enjoy your usual outdoor activities. Follow Dr's advice for exercise regime and condition management.

No need to modify usual outdoor activities.


36 - 75 ppb
(~90 to ~ 200 µg/m3)

There may be a moderate health risk for a very small number of people who are unusually sensitive to SO2.

A small number of persons with asthma who are very sensitive to SO2 may experience symptoms. Follow Dr's advice for managing condition. No need to modify usual outdoor activities.

76 - 185 ppb
Unhealthy for
Sensitive Groups

(~200 to ~ 480 µg/m3)

Members of sensitive groups may experience health effects. The general public is not likely to be affected.

Increasing likelihood of respiratory symptoms such as chest tightness and breathing discomfort in people with asthma. People with asthma should consider limiting outdoor exertion or reschedule when SO2 concentrations are lower. Follow Dr's advice for managing condition.

No need to modify usual outdoor activities unless you experience symptoms of cough or wheeze when exercising. 

more than 185 ppb

(Higher than ~ 480 µg/m3)

Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.

Children, the elderly, asthmatics and people with heart and lung disease should limit exertion outdoors or reschedule when SO2 concentrations are lower. Follow Dr's advice for managing condition. At elevated SO2 concentrations, chest tightness and wheezing can occur, even with very brief exposures (minutes) in healthy people without asthma. Reschedule outdoor activity when SO2 levels are lower.

ppb = parts per billion
*At risk populations include exercising asthmatics. At higher concentrations, children, the elderly and people with chronic heart and lung conditions may experience symptoms of shortness of breath and chest tightness.


What is sulphur dioxide?

Sulphur dioxide (SO2) is a colourless gas produced when fuels containing sulphur are burned.

Along with other pollutants, SO2 is a recognized constituent of acid rain. Indoor SO2 levels routinely fail to reach levels observed outdoors as SO2 quickly binds with indoor surfaces.

What are the health effects of sulphur dioxide?

In the human body, the air passages in the lungs can constrict or tighten when SO2 is inhaled and comes into contact with the moist lining of the breathing tubes. Breathing difficulties and tightening in the chest can be especially bad for people with lung disease.

Short-term peak exposures to elevated SO2 are of special concern. In an asthmatic, especially during vigorous exercise such as jogging or hard physical labour, asthma may worsen. SO2 can also cause the eyes and throat to sting.

Why is sulphur dioxide being measured?

Air quality monitoring within Victoria's Inner Harbour has found that relatively high, short-term peaks of SO2 may occur in association with the cruise ships at Ogden Point. The Health Risk Guide was developed to support an SO2 monitoring program funded by the Ministry of Environment and the Greater Victoria Harbour Authority to address these findings.

SO2 concentrations in outdoor air at the monitoring location can change rapidly depending on the wind speed, wind direction and the number of cruise ships arriving, berthing and departing. The concentration of SO2 measured in the Inner Harbour is reported as an hourly average. However, there is a one hour time lag in reporting, and this should be considered in planning activities if one has a medical condition affected by SO2.

In August 2012, marine vessels, including cruise ships, were required to use lower sulphur fuel when approaching, docking and departing Ogden Port. This initiative has lowered the SO2 concentrations in outdoor air. In January 2015 further fuel restrictions have been implemented. 

For additional information on this please refer to The International Maritime Organization (IMO) – sulphur oxides regulation


James Bay Sulphur Dioxide Levels 2012 
James Bay Sulphur Dioxide Levels 2011
Health Assessment of Air Quality in James Bay 
2009 James Bay Air Quality Study - Phase III (2009) 
James Bay Air Quality Study Phase II (Feb 2009) Report on the Results of CALPUFF Air Quality Dispersion Modeling 2007 
James Bay Air Quality Study Phase I (Feb 2008) Report on the Results of Field Monitoring 2007 

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