PFAS are found in products such as non-stick frying pans, cosmetics, creams, textiles and food packaging. They have entered our waterbodies, drinking water and rainwater, and as such they are unavoidable. Our experts explain what they are, why they are so pervasive, and why there is increasing concern over their proliferation.
What are PFAS/PFOS?
Per- and polyfluorinated alkyl substances (PFAS) are a large and incredibly persistent group of chemicals (totalling more than 4,700 substances). Persistent means that they degrade slowly in the environment, and they are therefore often referred to as “forever chemicals”. Manmade and widely used, they have accumulated over time in the environment – and in our bodies. You may also see the acronym PFOS (Perfluorooctanesulfonic acid) when reading about forever chemicals – this is a member of the PFAS group, that has carbon chain containing eight carbon atoms.
Why are PFAS/PFOS so persistent?
PFAS are so persistent due to the presence of a carbon-fluorine bond, one of the strongest bonds occurring in nature – the large difference in electronegativity between fluorine and carbon creates an attractive force between them. As a result, it is incredibly hard to break down PFAS.
PFAS also have multiple fluorine atoms attached to an alkyl chain (a chain containing only carbon and hydrogen atoms).
The number of carbon atoms in the alkyl chain is also important, as the length of the alkyl chain influences how the particular substance interacts with the environment and its bioaccumulation properties.
In this case, the solubility of PFAS goes down as carbon-chain length increases – so PFAS are more likely to accumulate in the environment due to the carbon chain. Shorter compounds would be more likely to dissolve in water and will be more mobile in the environment.
Longer-chain compounds have been shown to attach better to soils and have a preference towards organic carbon, meaning that longer-chain PFAS accumulate easily in soil.
Why is there concern around PFAS?
Studies have shown links between PFAS exposure and a wide range of human health concerns.
Blood samples were collected from almost 70,000 people whose drinking water had been contaminated with PFOA in Utah (United States), and the subsequent testing demonstrated links between PFOA exposure and reproductive health issues, autoimmune disease, thyroid disease and certain cancers. PFOA stands for perfluorooctanoic acid and is within the PFAS group.
Following this, a peer-reviewed scientific journal, Environment International, published a review article on the “Evolution of evidence on PFOA and health following the assessments of the C8 Science Panel” and found evidence consistent with many of the findings.
In the EU, official classifications for some PFOS include ‘carcinogenic’, ‘reprotoxic’ (toxic to the human reproductive system) and ‘toxic to specific organs’, for example, the liver.
Closer to home, the production and use of PFAS in products has resulted in the contamination of drinking water supplies in several European countries. In some highly polluted areas, concentrations of PFOS and PFAS in drinking water were above the limit value for individual PFAS proposed in the 2018 recast of the EU Drinking Water Directive (EC, 2017).
PFAS/PFOS in the UK
In England, a BBC study found that PFAS levels exceeded European safety levels in almost half of the samples taken. However, none within the study exceeded current safety standards applying to England and Wales – as these are more relaxed, which is concerning some experts on the topic.
And although these limits are more relaxed, they were still breached outside the study, as it was found that an aquifer supplying the homes of 1000 people had four times the Drinking Water Inspectorate’s limit of PFOS, according to the Guardian. A UK water company recently admitted that it removed a supply containing four times the regulatory limit of perfluorooctane sulphonate (PFOS), which was being blended with other supplies to provide water to the homes of customers the summer of 2021.
According to the EU Commission, because of the large number of PFAS chemicals, a substance-by-substance assessment and management approach is not enough to effectively prevent risk to the environment and human health. Though the levels for the most prevalent, studied and regulated PFAS and PFOS are decreasing, levels of new, lesser-studied PFAS are increasing.
This is part of our series on emerging pollutants – including microplastics.