Sulphur oxides (SOx)

Name PRTR	Sulphur oxides (SOX as SO2)
CAS no	7446-09-5 (SO2)
Molecular formula	SOX/SO2

 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.

Uses

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.



---------------------------------------------------

¹ http://www.who.int/mediacentre/factsheets/fs313/en/
² http://www.norskeutslipp.no/en/Components/Emission/Sulphur-dioxide/?ComponentType=utslipp&ComponentPageID=58&SectorID=90
³ http://prtr.ec.europa.eu/#/pollutantinfo
⁴ https://www.eea.europa.eu/publications/air-quality-in-europe-2016
⁵ http://www.naturvardsverket.se/Sa-mar-miljon/Mark/Forsurning/Det-sura-regnet-avtar/
⁶ https://www.eea.europa.eu/publications/air-quality-in-europe-2016
⁷ http://www.airclim.se/f%C3%B6rsurningens-effekter
⁸ http://www.who.int/mediacentre/factsheets/fs313/en/