PFAS are synthetic chemical compounds that are used by industry and in consumer products as protective coatings for textiles and paper, in the production of semi-conductors, as components of aqueous film-forming foams (AFFF) used for firefighting, as polymer additives, in herbicide and insecticide formulations, and in cosmetics.

PFAS are a diverse class of compounds that have a hydrophobic (water repellent), fluorine-saturated carbon-chain and a hydrophilic (attracted to water) functional group, se figure 1. Their structure gives PFAS unique chemical properties, which includes being both water and fat repellent.

Resistance to chemical, biological and physical degradation processes, high potential for bioaccumulation and biomagnification and toxicity to organisms at environmentally relevant concentrations has given rise to environmental concern.

Water and fat

Figure 1. Representation of the PFAS compound, PFOS. PFAS compounds have a hydrophobic carbon-chain with multiple fluorine atoms, and a hydrophilic functional group.

 

More than 3000 different PFAS compounds have been detected, with varying number of carbon atoms and functional groups. Two of the most well-known PFAS compounds, PFOS and PFOA (shown in figure 2), have been widely researched and a number of regulatory and voluntary initiatives have been established to limit production and use.

PFOS PFOA

Figure 2. Structure of PFOS and PFOA, two of the most well-known PFAS compounds.

 

Based on their functional group, PFAS compounds can be divided into different groups, se figure 3. First generation PFAS, defined here as groups such as perfluorocarboxylic acids (PFCA), perfluorosulfonic acids (PFSA), fluorotelomer alcohols (FTOH), fluorotelomer sulphonates (FTSA), perfluorosulfonamides (PSA), and fluoroalkyl sulphonamides are widely researched and heavily regulated.

PFAS groups

Figure 3. PFAS compounds are grouped according to their functional group. The figure shows examples of groups defined as first generation PFAS, and structure of selected compounds in the PFSA group.

 

Future generation PFAS, expected to replace classical PFAS, include chemicals such as F-53B and fluorotelomer betaines. Continuous technological developments in trace analytical methods will lead to many more PFASs being identified as relevant environmental contaminants.

For more information and definitions about PFAS, see here:

http://www.environmentalrestoration.wiki/index.php?title=Perfluoroalkyl_and_Polyfluoroalkyl_Substances_(PFASs)