What are PFAS?
- Depending on the definition of “PFAS” – also known as per- and polyfluoroalkyl substances – between 4700 and 9000 substances may be labelled as PFAS. Not all PFAS are in commercial use. OECD definition of PFAS (version July 2021): “PFASs are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e. with a few noted exceptions, any chemical with at least a perfluorinated methyl group (–CF3) or a perfluorinated methylene group (–CF2–) is a PFAS.”1 This definition includes about 9000 PFAS substances with a large variety of properties, including gases, polymers and liquids, as well as hazard profiles. The OECD finds within this grouping approach 24 subcategories.
- ECHA and the 5 competent authorities’ (Netherlands, Germany, Denmark, Sweden, Norway) propose the following definition of PFAS: “PFAS are defined as substances that contain at least one fully fluorinated methyl (CF3-) or methylene (-CF2-) carbon atom (without any H/Cl/Br/I atom attached to it).” This includes about 9000 substances and is similar to the 2021 OECD definition.
- An early and widely recognised technical definition of PFAS is provided by Buck et al. (2011), who defined PFAS as, “highly fluorinated aliphatic substances that contain one or more carbon (C) atoms on which all the hydrogen (H) substituents (present in the nonfluorinated analogues from which they are notionally derived) have been replaced by fluorine (F) atoms, in such a manner that they contain the perfluoroalkyl moiety CnF2n+1 –.”
- PFAS can be divided into sub-groups such as fluoropolymers and F-gases. Find out more about fluoropolymers here and F-Gases here.
What makes one PFAS different from another?
Where the common denominator amongst all substances clustered together as PFAS, is their carbon-fluorine bond, the number of carbon or fluorine atoms may differ in each one of them. Depending for instance on the quantities of one of these atoms over another, the degree of persistence, mobility and toxicity of each individual PFAS may differ.
FPP4EU is currently doing research into over 20 types of PFAS to demonstrate how they differ.
What are the concerns around PFAS?
PFAS are a large group of molecules and not all have the same properties. Some of the main concerns of regulators are:
- Persistence: Due to their carbon-fluorine bonds PFAS resist degradation when used and also in the environment. One of their main properties is durability when exposed to chemicals, high-temperatures or abrasion. Durability may also lead to persistence in the environment.
- Mobility: Some PFAS are easily transported in the environment for long distances and have been detected in groundwater, surface water and soil.
- Toxicity: Some PFAS have also been detected in the human body causing negative side-effects to our health.
Do all PFAS create the same concerns to humans and the environment?
Some PFAS, such as PFOA and PFOS, have shown to cause concerns for human health and the environment, and these have been regulated. But not all PFAS are the same and many may be used safely with the right measures to control emissions during production, use and end-of-life phases.
Are PFAS persistent?
The strong carbon-fluorine bond makes PFAS substances persistent. This stability is often needed to enable the durability that is requested from them in their use. Highly stable molecules are, by definition, more likely to be persistent in the environment. This, however, does not mean that all PFAS either show the same level of persistence, e.g. PFOA, or break down into persistent PFAS.
Are PFAS mobile?
Some PFAS will be mobile, others will not. Generally, high molecular weight PFAS (e.g. fluoropolymers) do not represent an issue in terms of mobility, whereas low molecular weight PFAS (such as PFOA or PFOS) have a higher potential to be mobile.
A chemical is considered “mobile” when it may enter the water cycle because it does not bind to solids such as sand or activated carbon. This means the chemical is soluble in water. For this reason, it can penetrate natural barriers (e.g. rivers and lakes) their removal by artificial filters may be more difficult than for other less soluble substances. There is no simple rule and no agreed definition of mobility under REACH. Fate and transport of PFAS continues to be studied.
Are PFAS toxic?
Some, but not all PFAS are (eco)toxic. To determine whether a substance is toxic, the current REACH regulation applies the following criteria:
• “the long-term no-observed effect concentration (NOEC) or EC10 for marine or freshwater organisms is less than 0.01 mg/l;
• the substance meets the criteria for classification as carcinogenic (category 1A or 1B), germ cell mutagenic (category 1A or 1B), or toxic for reproduction (category 1A, 1B, or 2) according to Regulation EC No 1272/2008;
• there is other evidence of chronic toxicity, as identified by the substance meeting the criteria for classification: specific target organ toxicity after repeated exposure (STOT RE category 1 or 2) according to Regulation EC No 1272/2008.”
What are PFAS used for?
Beyond well-known applications like carpet protectant and non-stick cookware, PFAS are used in industrial applications where their characteristics – durability, thermal and chemical stability, fire resistance, water and oil repellence – are indispensable. PFAS are used in many key EU industry sectors, such as aerospace and defense, transport, textiles, construction, electronics, and health. Our applications section on the website gives a more comprehensive overview.
What makes PFAS ideal for the applications that they are used in?
While some PFAS substances, such as PFOA and PFOS, have raised concerns for human health and the environment and have been regulated accordingly, not all PFAS are the same: many may be used safely with the right measures to control emissions during production, use and end-of-life phases.
The common denominator amongst all substances clustered together as PFAS, is their carbon-fluorine bond. This bond results in a combination of desirable and unique chemical and physical properties. For instance, durability, thermal and chemical stability, fire resistance, water and oil repellence. These properties make some groups of PFAS irreplaceable in applications where harsh conditions are experienced, and where longevity is needed. Such characteristics are critical for use in important product applications across many industries.
Other types of chemicals, which lack the strong carbon-fluorine bond, may not bring the combination of functionalities and therefore may perform less effectively. A detailed life cycle assessment would be needed to evaluate the potential impact of any replacement substance on the environment. While some alternative materials might match selected properties of PFAS substances, it is the combination of properties present in PFAS-based materials that makes them so ideal for many applications.
How are PFAS regulated in Europe?
PFAS as a group, are facing a restriction in the EU under REACH from January 2023 onwards. There is no clarity yet on what this restriction will exactly entail. More here.