Per- and polyfluorinated alkyl substances (PFAS) are a group of synthetic chemical compounds where the hydrogen atoms have been largely or completely replaced by fluorine. Human-manufactured, they do not occur in nature, but are ubiquitous globally in a wide variety of applications due to their water and dirt-resistant qualities which means that they resist degradation when used and when present in the environment. These uses include in the oil and gas industries, for coating products, and as a component in cosmetics, pesticides and pharmaceuticals.
There are at least 4 700 substances considered to be PFAS1, but the two most well-known are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). In recent years PFOA and PFOS use has been restricted globally, leading to the development of replacement substances which have similar properties.
The chemical stability of PFAS, a result of the strength of bonds of carbon and fluorine in the compounds, means that they barely degrade under natural conditions and, even when partial degradation occurs, residues persist for periods of time so long — from decades to centuries or even longer — that they have been referred to as ’forever chemicals‘. They are also highly mobile in water, and can accumulate in soil. The European Chemical Agency considers them substances of very high concern, and proposed a restriction on around 10 000 such substances in February 2023. Additionally, the European Food Safety Authority (EFSA) ruled on PFAS in 2020, establishing a tolerable weekly dose of 4.4 nanogram per kilogram body weight for four particularly prominent substances.
In a major review of evidence on PFAS to date, researchers in Germany highlighted the logic behind such policy moves. They noted research demonstrating harm to aquatic animals, amphibians and insects even at small concentrations, as well as significant accumulation within the bodies of organisms and in food webs. Further, they highlighted studies suggesting the toxic effects of PFAS on humans, particularly on the liver, kidney, thyroid and immune system, even at low doses. These toxic effects are thought to negatively impact a range of human functions including metabolism, respiration and cognition. They also provide evidence suggesting that human uptake of PFAS through food and drinking water often reaches and exceeds the EFSA-prescribed limit2.
The effects of PFAS may be multiplied by human exposure to other harmful substances, say the researchers, with more stringent risk assessments needed for these mixtures – something acknowledged in the EU’s Chemicals Strategy for Sustainability. They also call for improved monitoring on direct releases of the chemicals, with further developments in the analytical models needed for such work.
To conclude the review, the researchers published a 13-point list of reasons for a complete phase-out of PFAS, and the development of fluorine-free alternatives. They summarised both the immediate risks and potential legacies of continued use of the substances, as well as a number of knowledge gaps around potential risks that they suggest means that anything short of the suggested phase-out is inadequate.
Among the summarised findings, they noted that the move to new compounds with shorter molecular chains is not sufficient to prevent lasting risks as, although they are less harmful in aquatic environments, they are more mobile in soil and groundwater, leading to greater accumulation in plant tissues. Ultra-short-chain PFAs are often not included in analytical measurements, meaning that the toxicological and ecotoxicological properties of these substances have only been sparsely investigated, and suggesting that the relevance of these compounds has so far been underestimated. Among these compounds, trifluoroacetic acid (TFA) has a special status because TFA is a classic ’forever chemical’. Due to diffuse emissions – for example from the release of the vehicle refrigerant R1234yf, or the thermal decomposition of fluoropolymers such as polytetrafluoroethylene (PTFE, often used in non-stick cookware) – the concentrations of TFA in the environment are constantly increasing.
The authors point to the need for effective remediation of PFAS-contaminated sites, and purification of affected soils and waters. However, they point to inadequacy of current measures, and an urgent need for further research, while also suggesting that legal avenues must be created to ensure that PFAS producers and polluters, and not the general public, pay for such efforts. Disposal of waste contaminated with PFAS also requires improvement, they note, as there is conflicting data on the conditions necessary for methods such as incineration to completely destroy the harmful fluorochemicals3.
The worldwide threat posed by PFAS means that bans on individual molecules and reduced risks are not enough, they conclude. Legislation will not prove sufficient either, without a simultaneous effort by industry to come up with fluorine-free alternatives for the many applications where PFAS are currently used.
- OECD (2018) Toward a new comprehensive global database of per- and polyfluoroalkyl substances (PFASs): summary report on updating the OECD 2007 list of per- and polyfluoroalkyl substances (PFASs). Series on risk management no. 39. ENV/JM/MONO(2018) 7: 24.
- Göckener, B., Weber, T., Rüdel, H., Bücking, M. and Kolossa-Gehring, M. (2020) Human biomonitoring of per- and polyfluoroalkyl substances in German blood plasma samples from 1982 to 2019. Environ Int 145:106123. Available from: https://doi.org/10.1016/j.envint.2020.106123 [Accessed 20 September 2023].
- US EPA (2020) Interim guidance on the destruction and disposal of perfluoroalkyl and polyfluoroalkyl substances and materials containing perfluoroalkyl and polyfluoroalkyl substances (EPA-HQ-OLEM-2020-0527-0002). Available from: https://www.epa.gov/system/files/documents/2021-11/epa-hq-olem-2020-0527-0002_content.pdf [Accessed 20 September 2023].
Brunn, H., Arnold, G., Körner, W., Rippen, G., Steinhäuser, K.G. and Valentin, I. (2023) PFAS: forever chemicals—persistent, bioaccumulative and mobile. Reviewing the status and the need for their phase out and remediation of contaminated sites. Environmental Sciences Europe 35 (1): 1–50. Available from: https://doi.org/10.1186/s12302-023-00721-8
To cite this article/service:
“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by the Science Communication Unit, The University of the West of England, Bristol.
Notes on content:
The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.
- Publication date
- 19 October 2023
- Directorate-General for Environment