The copper and zinc-lead ores found in our region contain sulphur. When these ores are processed, sulphur dioxide is released.
Sulphur dioxide is a colourless gas with a sharp odour that may irritate the eyes, nose, throat, airways and to a lesser extent, the skin.
What are the impacts of sulphur dioxide?
High concentrations of sulphur dioxide can result in temporary breathing impairment for asthmatics who are sensitive to sulphur dioxide and are concurrently active enough outdoors to increase breathing rate and depth when exposure occurs. An important fact is not all exercising asthmatics are sulphur dioxide responsive at any given concentration.
For individuals who are responsive, short-term exposures to elevated sulphur dioxide levels during moderate activity may result in breathing difficulties that could be accompanied by symptoms such as wheezing, chest tightness or shortness of breath. These effects are very similar to those that occur with other environmental factors that might trigger asthma symptoms. The effects quickly abate usually within an hour when exposure to sulphur dioxide stops and/ or physical activity decreases. Sulphur dioxide shows no evidence of cumulative or long-term effects. The bronchoconstriction is prevented or ameliorated with medication inhalers commonly used by asthmatics.
Healthy people are not significantly affected until concentrations become quite high, approximately 14,000µg/m³. There is no observed effect level for these people between 2,800µg/m³ and 5,700µg/m³. Thus non-asthmatics are much less affected by sulphur dioxide than are exercising asthmatics who are sulphur dioxide responders.
If you are concerned about the health impacts of sulphur dioxide, consult a medical professional.
Air quality standards for sulphur dioxide
A series of clinical
studies conducted worldwide found exercising asthmatics demonstrated no observable impairment to respiratory function when exposed to sulphur dioxide concentrations of 0.20 parts per million.
This is why the National Environment Protection Measures (NEPM) for Ambient Air Quality, agreed between the Federal and State Governments, stipulates the maximum sulphur dioxide concentration for a one-hour period is 0.20 parts per million; the equivalent of 570 micrograms per cubic metre of air.
This approach works in two ways. Firstly, it ensures concentrations are kept at a level where even the most vulnerable members of the public are unlikely to experience any adverse impacts from sulphur dioxide exposure.
Secondly, reducing the average exposure period to one hour means short-term peaks of sulphur dioxide that could cause irritation must be managed very quickly to maintain operations within the NEPM limit, which minimises the potential for impacts to the community.
In addition to measuring short-term hourly sulphur dioxide concentrations, the Environmental Protection (Air) Policy 2008 also stipulates limits for concentrations averaged over a daily and yearly period. This allows government and industry to manage both the short-term peaks in exposure, as well as minimise emission levels over longer periods.
In line with Queensland's environmental legislation, we are committed to operating within the limits stipulated by our Queensland Government approved Environmental Authority (EA).
Under our EA, we are required to manage operational emissions to ensure sulphur dioxide concentrations in Mount Isa stay below an hourly average of 570 micrograms per cubic metre of air 98% of the time.
For more information, refer to the
Australian Government's National Environmental Health Monograph for sulphur dioxide.