Polycyclic aromatic hydrocarbons (PAHs)

PAH, Polycykliska aromatiska kolväten

 The group polycyclic aromatic hydrocarbons (PAH) consists of several hundred substances. PAH compounds contain at least two benzene rings bound together. PAH is the largest group of carcinogenic substances that we currently know of.¹

Uses

PAHs are present in for example fossil fuels and oil products. Coal tar contains high levels of PAHs.² The majority of the PAHs are used in different blends, such as different types of coal and tar products. Some specific PAHs can be used in manufacturing industry, such as anthracene, which is used as a synthetic raw material.³

Sources and transportation pathways

PAHs are formed unintentionally during combustion. They are also present in fossil fuels and enter the environment during incomplete combustion in for example coke ovens and motor vehicles as well as through cigarette smoke and small-scale wood burning. PAHs are also emitted to the environment during forest fires and volcanic activity. One important transportation pathway is by air. Emissions to water occur from wastewater treatment plants. In water, PAHs tend to bind to particles and sediment.⁴ Industrial operations such as production and processing of metals, paper and wood product processing and operations within the energy sector are important sources of PAHs.⁵

Spillage of products containing PAHs, for example fuel oil or fossil fuels, can lead to its presence in soil and water. Tyres containing high-aromatic oils (HA oils) contribute to the presence of PAHs in the environments through tyre wear as well as the recycling of tyres for manufacturing of rubber granulate that is used in artificial grass fields.⁵

Effects on environment and health

PAHs are fat-soluble, often stable and in some cases bioaccumulative. Because of their stability, they are not easily degraded and can therefore travel long distances before they degrade. PAHs can be very persistent in water sediment, causing high exposure for aquatic organisms. Many PAHs are, or are expected to be, carcinogenic.⁷

International agreements and regulations

Polycyclic aromatic hydrocarbons are regulated by the UN Convention on Long-Range Transboundary Air Pollution (CLRTAP) and the EU Water Framework Directive (2000/60/EC). The presence of PAHs in products is for example regulated by the EU REACH regulation (EC 1907/2006). The UN Protocol on PRTRs and the EU E-PRTR regulation regulate how data on PAH emissions is made available.

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¹  https://www.kemi.se/prio-start/kemikalier-i-praktiken/kemikaliegrupper/polycykliska-aromatiska-kolvaten-pah
² http://www.asfaltskolan.se/res/PDF/stenkolstjraiasfalt_skllgesrapport0305.pdf
³ https://www.prevent.se/globalassets/global/regelbanken/eu/kandidatforteckningen_jan_2017.pdf
⁴ https://toxnet.nlm.nih.gov/
⁵ http://utslappisiffror.naturvardsverket.se/Sok/
⁶ https://www.kemi.se/prio-start/kemikalier-i-praktiken/kemikaliegrupper/polycykliska-aromatiska-kolvaten-pah
⁷ https://www.kemi.se/prio-start/kemikalier-i-praktiken/kemikaliegrupper/polycykliska-aromatiska-kolvaten-pah