State of the Environment Report 2007
Sulfur dioxide (SO2) is a colourless gas with a pungent, suffocating odour. It can be a significant air pollutant in WA, particularly around industrial areas such as Kalgoorlie, Kwinana and Collie. It is produced by the combustion of fuels like coal, oil and diesel fuel, and in smelting of metallic sulfide ores. The sulfur content of a fuel can be reduced by refining, so that less sulfur dioxide is emitted when the fuel is burned. Sulfur dioxide oxidises in air to sulfite (SO3) which, when dissolved in atmospheric water droplets, forms sulfuric acid and potentially acid rain. Acid rain issues have not been researched in WA as the problem has not been recorded as it has in parts of America and Europe. This process is accelerated in the presence of particulates, assisting with the condensation of water droplets (see 'Particulates'). Industry uses a similar chemical process to generate sulfuric acid.
Sulfur dioxide is a dangerous air pollutant because of its toxicity and corrosive properties. Sulfur dioxide is a strong irritant to the respiratory tract, causing breathing problems in people with sensitive airways. In addition, sulfur dioxide can corrode buildings and other infrastructure, and damage aquatic systems and vegetation, including agricultural crops.
There are standards in place for sulfur dioxide via the National Environment Protection (Ambient Air Quality) Measure (NEPM) to ensure community health is not compromised. They include:
Sulfur dioxide:
Averaging period: one hour; Maximum concentration: 0.20 ppm; Goal by 2008 (maximum exceedences): one day per year
Averaging period: one day; Maximum concentration: 0.08 ppm; Goal by 2008 (maximum exceedences): one day per year
Averaging period: one year; Maximum concentration: 0.02 ppm; Goal by 2008 (maximum exceedences): none
There is also a State policy (the Environmental Protection (Goldfields residential areas) (sulfur dioxide) Policy 2003) that specifies emissions standards for the Goldfields, including:
Sulfur dioxide:
Averaging period: one day; Maximum concentration: 0.2 ppm; Goal by 2008: the current number of allowable exceedence days is three per year. The goal is to progressively reduce the number of exceedences to meet the NEPM goal (one day per year) in 2008.
Kalgoorlie-Boulder, Kwinana and Collie are the major settlements experiencing sulfur dioxide issues. Kalgoorlie-Boulder has had a dramatic improvement in sulfur dioxide levels over the last decade (Figure A5.1), although the environment protection policy standards are occasionally exceeded. Since 1998, the NEPM goal of no more than one exceedence per year has been met. At Kwinana, sulfur dioxide emissions have not exceeded the standard since 1993 (Figure A5.2). Collie has remained below the standard since monitoring commenced in 1995, although a cautious view needs to be taken of these results because monitoring at industry sites suggested that the location may not be representative of the local airshed (Figure A5.3). Emission reductions at both Kalgoorlie and Kwinana have been achieved due to improved regulation and best practice industry technology. Sulfur dioxide is also measured at Rockingham and Wattleup, but no exceedences of the standard have been recorded at these sites.
![Figure A5.1: Ambient yearly range of sulfur dioxide levels (one-hour average) at Kalgoorlie Regional Hospital air quality monitoring station, compared with the Australian standard for exposure. [Data source: Department of Environment and Conservation.]](/site/files/images/Figure-A5.1_Large.jpg)
![Figure A5.2: Ambient yearly range of sulfur dioxide levels (one-hour average) at Hope Valley air quality monitoring station, compared with the Australian standard for exposure. [Data source: Department of Environment and Conservation.]](/site/files/images/Figure-A5.2_Large.jpg)
![Figure A5.3: Ambient yearly range of sulfur dioxide levels (one-hour average) at Collie air quality monitoring station, compared with the Australian standard for exposure. [Data source: Department of Environment and Conservation.]](/site/files/images/Figure-A5.3_Large.jpg)
Twelve exceedences of the NEPM standard for sulfur dioxide occurred between 1998 and 2004 (Table A5.1). With the exception of the Kalgoorlie Regional Hospital exceedence, most were recorded in the Kalgoorlie-Boulder area at industry sites. There were no exceedences recorded at monitoring sites in the Perth area (Figure A0.1).
Ambient sulfur dioxide levels around Kalgoorlie have fallen following the installation of scrubbing equipment at the largest industrial source (metal smelters), and are expected to be successfully controlled into the future. However, National Pollutant Inventory estimates of emissions of sulfur dioxide across the State have generally been increasing (Figure A5.4) since 1999-2000 (emissions data prior to this are unreliable). However, it should be noted that many more companies and facilities reported their emissions in later years than did in earlier years, which may account for the overall increase (186 facilities from 30 industry sources in 1999-2000 compared to 279 facilities from 40 industry sources in 2005-06) (Department of the Environment and Water Resources, 2007).
Although there has been a very significant improvement in SO2 levels around Kwinana, vigilance needs to be maintained because health effects can be seen at concentrations less than NEPM levels. There are now considerable pressures due to expansion of existing industries, the lack of available land for more industry and the construction of new homes in the buffer zone.
The levels of sulfur dioxide at Collie are under comparatively less pressure from emissions, but future construction of coal-fired power stations is likely to result in it becoming more of an air quality issue.
![Figure A5.4: Estimated sulfur dioxide emissions in Western Australia from various sources. [Data source: Department of the Environment and Water Resources - National Pollutant Inventory sulfur dioxide Western Australia [ver. 2007].]](/site/files/images/Figure-A5.4_Large.jpg)
The Air Quality in Perth: 1992-2002 study (Department of Environmental Protection, 2003) found ambient sulfur dioxide levels were negligible in the Perth airshed, and had decreased from industrial sources. The gradual shift in energy sources from coal to natural gas, tighter sulfur dioxide controls and installation of sulfur recovery units at Kwinana industries are thought to have contributed to the emission decrease for Perth (Department of Environmental Protection, 2003).
Environmental protection policies: were established to provide regulatory standards and limits for sulfur dioxide levels for Kwinana (December 1999) and Kalgoorlie (March 2003). It should be noted that although both Kalgoorlie and Kwinana have policies in place, they have a different purpose in each location. The focus in Kwinana is controlling industrial emissions, while at Kalgoorlie it has been to limit emissions when meteorological conditions are likely to affect the local community. There has been concern about short periods of exposure to high levels of sulfur dioxide, and a review is underway to assess the practicability of introducing a 10-minute standard: currently the shortest averaging period is one hour (National Environment Protection Council, 2004b).
Environmental Protection (Diesel and Petrol) Regulations 1999: were introduced as a way to improve fuel quality, and therefore emissions, from existing vehicles. The regulations aim to phase out leaded petrol, limit emissions of evaporative hydrocarbons from vehicles, reduce sulfur content of petrol and diesel to improve performance of three-way catalytic converters, and other initiatives to reduce environmental impacts.
National Pollutant Inventory: The National Environment Protection (National Pollutant Inventory) Measure defines substances for which companies and governments need to report emissions. This provided the framework for the development and establishment of an internet database designed to provide publicly available information on the types and amounts of certain chemicals being emitted to the air, land, and water (Environment Protection and Heritage Council, 2006).
The most common health symptoms resulting from inhalation of sulfur dioxide are coughing, wheezing and shortness of breath. Some people experience a burning sensation in their airways. Asthmatics are most sensitive to sulfur dioxide, usually suffering a sharp short-term decrease in lung function, but repeated exposure does not seem to worsen symptoms (Department of Environmental Protection, 2000a). In addition to human health consequences, sulfur dioxide can cause corrosive damage to buildings and other infrastructure, aquatic systems and vegetation, including crops (Department of Environment, 2003a). Australian studies indicate that crop yields can be affected by prolonged exposure to 0.05 ppm and greater concentrations, while trees suffer leaf damage at 0.08 ppm (Department of Environmental Protection, 2000a). Sulfur dioxide is known to go into solution and form acid rain in parts of Europe, Asia and America, but this has not been researched in WA.
2.17 Implement the Perth Air Quality Management Plan and other sulfur dioxide regulations and policies: significant progress has been made with lowering emissions in problem areas, but further work is still required.
2.18 Develop and implement an air quality management plan for regional areas where significant sources of sulfur dioxide emissions exist or are planned.
