What are PFAS?

They are used in various industrial sectors: firefighting, air-conditioning systems, agriculture and everyday products such as textiles and household goods. PFAS do not occur naturally.

⁠PFAS⁠ degrade very slowly and therefore persist in the environment for a very long time. Some PFAS accumulate in the environment and in organisms and are also harmful to human health. Their widespread use is leading to the global distribution of these substances of concern.

These organic compounds consist of carbon chains of varying lengths, in which the hydrogen atoms are either completely (perfluorinated) or partially (polyfluorinated) replaced by fluorine atoms. Perfluorinated carboxylic and sulphonic acids, as well as their precursor compounds, are the most commonly used. Precursor compounds are polyfluorinated substances that are degraded into these persistent perfluorinated substances.

Due to their differing chemical properties, PFAS are classified as long-chain and short-chain PFAS. Short-chain PFAS include perfluorinated carboxylic acids and their precursor compounds with fewer than seven carbon atoms, as well as perfluorinated sulphonic acids and their precursor compounds with fewer than six carbon atoms. Long-chain PFAS are persistent and accumulate particularly in organisms along food chains. In contrast, although short-chain PFAS are also extremely persistent, they are significantly more mobile and therefore spread more rapidly through the water cycle.

Among the short-chain PFAS, trifluoroacetate (TFA) plays a special role (see also TFA background paper and final report of a TFA expert assessment on spatial analysis). TFA is the anion of the perfluorinated carboxylic acid with the shortest carbon chain (trifluoroacetic acid). It serves as a basic chemical and is also used as an end product of the degradation of fluorinated substances – such as pesticides, refrigerants, medicines or industrial processes. TFA is extremely stable and does not degrade in the environment. It enters our environment in various ways: via seepage from farmland into groundwater, via industrial effluent into our rivers, and via fluorinated gases – such as those from air-conditioning systems – into our atmosphere, from where it is washed back down as rain. Due to its high water solubility, TFA spreads rapidly throughout the water cycle. There are currently no practical methods for removing TFA from the environment – the result is a steady build-up. TFA is ubiquitous – whether in the sea, rivers, lakes and groundwater, or even in food and tap water (see also: Persistent substance found everywhere).