Xylenes

Xylener, Xylener, summa isomerer

 Xylene is an aromatic hydrocarbon that belongs to the group volatile organic compounds (VOC). There are three different isomers of xylene; ortho-, meta-, and para-xylene. Xylene, as a blend of isomers, is a very flammable liquid that is colourless and has a sweetish odour. Xylenes have low water solubility.¹

Uses

The primary use for xylenes is in motor fuels, as xylene is a component of gasoline. The different isomers are used in production of other chemicals in for example plastic industry and are reactants in synthesis of specialty chemicals such as vitamins, pharmaceuticals and aromas. The blend of xylene isomers is used as solvent in several products demanding high solubility and a relatively high evaporation rate, such as paints, degreasing agents, adhesives, sealants and car care products.² Other products containing xylene are anti-freeze products and biocides, for example disinfectants and products for pest control.³

Sources and transportation pathways

Xylenes are present in petroleum, natural gas and coal tar. Xylene is also naturally occurring in some plants and is emitted from corn, alfalfa and cereal silage.⁴ VOCs are emitted to air during incomplete combustion and by evaporation. In the past, the transport sector has been an important contributor to national emissions of VOCs, but as a result of effective measures (e.g. the introduction of catalysts) emissions from this sector have decreased substantially. Today, the most important source is evaporation from solvents within the sector product use.⁵, ⁶

The large point sources that contribute the most to national emissions of xylene to air are facilities within the energy sector, chemical industry and metal processing.⁷

The substance may be emitted during the use of products containing xylene.⁸

Xylene is emitted to the environment by air. If emitted to water or land, xylene evaporates to air where it is degraded. In soil, it may also be degraded by microorganisms.⁹

Effects on environment and health

Xylene is flammable and harmful if inhaled and by skin contact. The substance is not expected to accumulate in the environment.¹⁰

As a VOC, xylene can be involved in the formation of ground-level ozone. Ground-level ozone may damage vegetation and during episodes of elevated VOC levels, it may cause irritation of the respiratory tract in humans.

International agreements and regulations

As a VOC, xylene is indirectly 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) and the EU Industrial Emissions Directive (2010/75/EU).

The UN Protocol on PRTRs and the EU E-PRTR regulation regulate how data on xylene emissions is made available.

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¹  https://rib.msb.se/
² https://webapps.kemi.se/flodesanalyser/AmnesInfo.aspx?amne=xylen
³ https://echa.europa.eu/
⁴ https://toxnet.nlm.nih.gov/
⁵ http://envs.au.dk/en/knowledge/air/emissions/air-pollutants/nmvoc/
⁶ http://www.naturvardsverket.se/Sa-mar-miljon/Statistik-A-O/Flyktiga-organiska-amnen-utslapp-till-luft/
⁷ http://utslappisiffror.naturvardsverket.se/Sok/
⁸ https://toxnet.nlm.nih.gov/
⁹ https://toxnet.nlm.nih.gov/
¹⁰ https://echa.europa.eu/