Sulfur dioxide (SO2)

SO2, Svaveldioxid


Sulphur oxides (SOX as SO2)

CAS no

7446-09-5 (SO2)

Molecular formula


 Sulphur dioxide is a colourless gas with a sharp odour1. Sulphur oxides dissolve easily in water and form sulphuric acid, which is an acidic solution.


Sulphur dioxide is used within industry for example as bleach, disinfectant and preservation of food2.  Sulphur trioxide is used in production of sulfuric acid3.

Sources and transportation pathways

Sulphur oxides are emitted to the atmosphere both from natural and anthropogenic sources. The largest natural source on a global scale is volcanic activity4. Emissions of SO2 from anthropogenic sources occur during combustion of sulphur-containing fuels (e.g. coal and fuel oil)5, and during industrial processes using sulphur-containing raw material and additives. The largest sources of sulphur dioxide in Sweden are, in decreasing order, processing industry (e.g. pulp and paper and metal industry), production of electricity and district heating, and heating of buildings.

Effects on environment and health

Sulphur dioxide has an acidifying effect on the environment. Acidification harms plants and animals, both on land and in water6. When the ground turns acidic, vital nutrients are leached from the soil, which eventually may result in reduced forest growth. Furthermore, metals are released in the ground that can harm decomposing organisms in the ground as well as birds and mammals higher up in the food chain, including humans7.

Sulphur dioxide may affect the respiratory tract and lung function, as well as cause eye irritation. Hospital visits as a result of heart decease as well as the number of deaths increase on days with higher SO2 concentrations in the air8.

International agreements and regulations

Sulphur oxides are regulated by the UN Convention on Long-range Transboundary Air Pollution (CLRTAP) and the UN Framework Convention on Climate Change (UNFCCC) as well as by the EU National Emissions Ceilings Directive (2001/81/EC), the EU Air Quality Directive (2008/50/EC) and the EU Industrial Emissions Directive (2010/75/EU). The UN Protocol on PRTRs and the EU E-PRTR regulation regulate how data on sulphur oxide emissions is made available.