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Sulphur dioxide (SO2) is a colourless, soluble gas that has a strong smell. It is mainly produced by the burning of fossil fuels containing sulphur, however it can also be produced by some industrial processes.
SO2 is harmful when inhaled at high concentrations and acts directly on the upper airways (nose, throat and lungs) producing a response within minutes. It is particularly harmful to people with existing respiratory problems, such as asthmatics or people suffering from lung disease. Symptoms of SO2 inhalation include wheezing, chest tightness, shortness of breath and coughing.
In Northland, the most significant industrial source of SO2 is the New Zealand Refining Company Limited, located at Marsden Point. The prevailing wind in this area frequently blows emissions from the refinery towards the Whangarei Heads, a largely rural, residential area. The Council monitors SO2 levels produced by the refinery using a continuous monitoring station based at Taurikura Bay.
In 2008-09, results from the monitoring station at Taurikura indicated that peak concentrations of SO2 from the refinery were well below the National Environmental Standard of 350 ug/m3, and also well below the current 24-hour ambient air quality standard of 120 ug/m3. These results can be seen in the graph below.