Non-polymer PFAS can build up in blood protein of animals, and is not always removed quickly. This means that predators eating PFAS-contaminated food will have higher levels in their bloodstream, and concentrations can increase up the food chain. Studies suggest that build up of PFAS is similar to those of other Persistent Organic Pollutants such as DDT.PFAS are estimated to be settling in arctic regions at rates of tens to hundreds of kilograms per year (25-850kg per year), depending on the specific PFAS chemical in question. Certain PFAS are released as gases to the environment and are blown a long way by wind and air currents in the atmosphere,. These gas PFAS will over time degrade to more persistent chemicals like PFOS and PFOA. This may be one reason why PFAS of environmental concern have been found in remote regions such as the Arctic as well as near PFAS production sitesPFAS including PFOS and PFOA have been found in air samples around Europe. The chemicals are found in small quantities, but appear in almost all samples tested. PFAS enters the atmosphere both from factories and the air inside our homes. PFAS is found in treated waste water from industrial and domestic sources and has been found in both rivers and groundwater. Conventional drinking water processes will not remove PFAS.PFAS-coated clothes that are thrown away will often end up either incinerated or in landfill. Unless incinerated at very high temperatures (>1000oC), fluorinated polymers could release more harmful PFAS during burning. PFAS of environmental concern have also been found in landfill leachate. Non-polymer PFAS are used in the production of fluorinated polymers. The manufacture of stain-resistant finishes generally releases these PFASs into the environment, both by air and water emissions. They are very hard to remove during water treatment. Workers in textiles factories are some of the population most exposed to these potentially harmful chemicals. Small quantities of PFAS will be removed during wash and wear of products containing PFAS. This includes fluorinated polymers used on stain-resistant coatings, and non-polymers that remain on clothes after production (Lassen et al. 2015).Most UK waste still ends up in landfill, and this includes PFAS-containing products. Studies have shown that the liquid coming from landfills (known as leachate) often contain non-polymer PFAS chemicals. In the USA the total quantities were estimated at 563-638 kg in 2013. To properly break down PFAS chemicals high temperature (1000oC or more) incineration is recommended. Incineration of municipal waste does not necessarily reach these temperatures (min temp. required is 850oC), and the incomplete breakdown could release non-polymer PFAS.Wash and wear of clothing that contains PFAS-based stain-resistant or water repellent finishes release PFAS to the environment. Coatings are thought to lose effectiveness after 20-30 washes. This can include non-polymer PFAS, remnant from production or as a break-down product of side-chain polymers (Lassen et al. 2015). The manufacture of stain-resistant finishes releases PFASs into the environment, both by air and water emissions. PFAS are very hard to remove during water treatment. Industrial emissions are estimated to be the biggest source of these chemicals to the environment.

Did you know?

The carbon-fluorine bond that typifies this group of chemicals is one of the strongest known to nature. Under typical soil conditions, it can take over a 1000 years for some PFAS to degrade. Once we create them, they just don’t go away. This extreme persistence is why PFAS are often known as the ‘forever chemicals’, and why what we do today has such a big effect on the state of our world tomorrow. 

Have you bought frying pans coated in Teflon? Do you look for bike oils that advertise the ingredient PTFE? Have you seen labels for PFC-free waterproofs? These are all terms used for PFAS.

You might actually know more about them than you first thought!

PFAS first came into common use in the 1950s and 1960s under the brand name Teflon. Since then their number of uses, both in industrial processing and consumer goods, has sky rocketed.

The two best known PFAS, namely PFOA and PFOS, are known to harm the environment and human health and their use is now strictly regulated. However, for every chemical that is restricted, there is another close behind to take its place. Worryingly, we currently know very little about the vast majority of PFAS chemicals. Industry simply replaces the devil we know, with the devil we don’t. Studies are already starting to show that many of these alternative PFAS could be as toxic as the ones they replace. Technically this is referred to as ‘regrettable substitution’, something that many NGO’s, including Fidra, are calling for legislative change to fix.

Read on to find out where PFAS lurks in your kitchen, your shopping basket, your coat cupboard and your bike shed. Learn about the PFAS problem and the implications of growing concentrations on our environment and our health. Then find out what you can do to change the story.

Why are PFAS chemicals used on our products?

The widespread use and success of PFAS comes down to a few key characteristics that the majority of PFAS chemicals have. Understanding these will help you to start recognising where they might be found in the products you buy:

They repel water and oil

clothing with pfas
Outdoor clothing
Outdoor equipment
Outdoor equipment
Stain resistant clothing
Stain resistant clothing
Stain resistant furniture and furnishings
Stain resistant furniture & furnishings
Grease proof take-away packaging
Grease proof take-away packaging

They make things slippery

Ski and snowboard wax
Ski & snowboard wax
Non-stick cookware
Non-stick cookware
Baking paper and baking cases
Baking paper & baking cases
Bike oil
Bike oil

They are surfactants – they help liquids to mix and spread

Paints adhesives and sealants
Paints adhesives & sealants
Cleaning products
Cleaning products

The are also used for many non-consumer functions

Fire Fighting Foams
Fire Fighting Foams
Industrial processing aids
Industrial processing aids

The Science – understand the basics

PFAS is a term used to describe a whole group of chemicals which are similar in that they contain a specific molecular structure, a ‘carbon chain’, and the element, ‘fluorine’. This carbon-fluorine bond is incredibly strong, meaning the resulting PFAS is extremely difficult to break down.

Polymers are substances consisting of a molecule (known as a monomer) that is repeated many times to create a long chain. E.g. synthetic plastics, silk, rubber. Polymer chain lengths are many thousands of molecules long.A 'backbone' of a hydrocarbon (C-H) polymer, with strands of fluorinated polymers attached, that stick up like the bristles of a comb. These are used to create water- and stain-resistant coatings. Fluorinated non-polymers are used as raw materials, or sometimes an ingredient to help the process of production (a processing aid), to make fluoropolymers and fluorinated side-chain polymers. Sometimes known as C8, Perfluoro-octane-carboxylic acid (PFOA) is one of the most studied PFAS. PFOA will be restricted by 2020 under European legislation because it is known to be persistent, bioaccumulative and toxic (PBT) in the environment.This was the original ingredient of Scotchgard, a fabric protector made by 3M. The use of this chemical is restricted globally by the Stockholm Convention on Persistent Organic Pollutants, because it is widespread and known to be harmful in the environment. Polymers tend to be very stable and do not easily break down in the environment. However, under certain conditions there may be exceptions. For example, the fluorinated side-chains that are connected to the main polymer backbone can sometimes react with surrounding chemicals or oxygen, releasing short-chain PFASs into surrounding environment. Fluoropolymers may break down to smaller molecules if heated to temperatures above 350 degC.

PFAS can be split into either polymers or non-polymers. Whilst the terminology might bring back nightmares from school chemistry lessons, the concept is very simple. Poly- means ‘many’ and -mer means ‘segment’, polymers are simply molecules that are long chains made up of many segments. Non-polymers are all the rest.

In ‘Fluoropolymers’ the unit that repeats over and over is a simple carbon atom with two fluorine atoms attached; PTFE for non-stick pans is based on fluoropolymers. The slightly more complex ‘Fluorinated side-chain polymers’ are used in textile finishes to give ‘stain resistance’ and ‘water repellent’ qualities.

Fluorinated side-chain polymers start as a basic polymer ‘backbone’ (long chain of atoms), which as the name suggests, has ‘side-chains’ containing fluorine added along its length. The side-chains stick up like the bristles of a comb and act as a barrier towards oil and water. The length of the side-chains, and the nature of the polymer ‘back-bone’ are what gives each individual chemical it’s distinct qualities.

Polymer backbone: A long chain of carbon & hydrogen.Reactions with other chemical groups, such as OH- in the environment, can release fluorinated side-chains to create new non-polymer PFAS.This is an organic chemical group (e.g. an alcohol, OH- group), that is more reactive than the carbon-fluorine bonds in the molecule, and allows it to attach to the polymer backbone.You could picture these as the ‘bristles’ of a comb, that stick up and create the water and oil resistant surface that resists stains. These non-polymer PFAS are just as persistent, but are more likely to be mobile, taken up by plants and animals, and therefore are of greater concern to the environment.

The polymers used to produce textile finishes are not considered to be harmful. This is because polymers are not reactive and the molecules are too large to be easily taken in by the human body (they are not bio-accessible). However, during production and as the polymer begins to break down, harmful non-polymer PFAS can be released into the environment.

The non-polymers are also based on chains of carbon atoms, usually with a chain length between 2 and 13 atoms, much shorter than those of polymers. These non-polymers can be split into a further 3 groups. The basic structure of these groups are the same, being primarily made up of carbon and fluorine in a repeating pattern, but the difference is that each group has another chemical group added (either a carboxylic acid, a sulfonic acid or an alcohol). The shorter chain means, compared to polymers, they are more mobile, reactive and more easily transferred into wildlife and humans.

Non-polymers can be either a raw ingredient or a processing aid in the manufacture of fluorinated polymers. There is also evidence that under certain conditions polymers can break down to release non-polymers (although loss through manufacture is likely to be the greater source to the environment). It is the non-polymers that we know can be very damaging to the environment and to our health. Until recently, PFOA and PFOS were the most commonly used PFASs in production of these side-chain polymers. They are the focus of the vast majority of research into PFAS so far and they are the ones that are heavily restricted or banned due to proven impacts on the environment and human health.

One last distinction, a slightly confusing but essential one as it’s key to how industry is currently dealing with new and existing regulations. The non-polymers usually contain between 2 and 13 atoms making up the ‘chain’ part of the structure.

Depending on the number of carbons, they are referred to as either ‘short-chain’ or ‘long-chain’. When people talk of ‘short-chain’ PFAS they are usually referring to non-polymers where there are 6 or less atoms making up the chain; long-chain refer to non-polymers where there are 7 to 13 atoms. Do not confuse ‘long-chain’ PFAS with polymer PFAS. PFOA and PFOS, are ‘long-chain’ PFAS with 8 atoms (sometimes known as C8 chemistry). Many manufacturers are switching to different versions with only 6 atoms in the chain i.e. C6 chemistry. Evidence is starting to show that these C6 PFAS could be just as persistent and just as toxic as the ones they replace.

Environment and Health

PFASs are found in marine animals, seabirds and predators in all parts of the world including polar bears in the remote arctic [1]. They are now ubiquitous in the environment. They have been recorded in our air [2], water [3],[4], sediment [5],[6], plants [7] and wildlife [8]. They are found in rain and snow [9], groundwater [10], tap water [11], rivers [12],[13],[14] lakes [15] and seawater [4],[16],[17].

There are no natural sources of PFASs, they are entirely man-made, however the vast number of consumer goods which utilise PFAS chemistry means they are widely lost into the environment. They can be lost from manufacturing facilities where the chemicals themselves, or the goods that use them, are made (24). They can be lost into wastewater, sewage treatment facilities don’t remove them so they can them be released alongside the treated water or in the sludge that is applied to land (30). They can be lost during use, for example a major localised source is where PFAS-containing firefighting foams are released for fire management or training (31). Wash and wear of clothing that contains PFAS-based stain-resistant or water repellent finishes is also thought to be a source to the environment though likely small compared to other pathways (32). Finally, when we dispose of goods the PFAS chemicals can be lost through landfill leachate (33).   

Once these chemicals enter our environment many are highly mobile, meaning they can be found far from their original source. Whilst the distribution pattern of PFASs shows highest concentrations in industrialised or urbanised areas (34), environmental transport means we also find PFASs turning up in the Arctic and in the bodies of polar bears despite no nearby sources. The important implication of this is that if we want to protect ourselves from exposure we need to cut sources worldwide, not just on our doorstep. Moving manufacturing abroad where regulations are weaker is not a solution, we need joined up global regulations to make a genuine impact.  

Some forms can be transported in the air as it circulates round the globe, it can then be deposited at sites far from its source (long-range atmospheric transport) either by settling out (dry deposition) or washed out in rain (wet deposition) (29). Even when harmful PFASs themselves aren’t present in the environment, their precursors may be. Under the right conditions chemicals that don’t themselves cause concern may break down to potentially toxic PFASs (35) 

Chemicals are generally classed as ‘of environmental concern’ if they are P-persistent, B-bioaccumulative and T-toxic (PBT). A number of PFASs have been classified as either PBTs or PB(T)s.  This means they won’t break down in the environment, will build up in the tissue or blood of animals that are exposed to them, and could cause harm to those animals. 

Once sufficient evidence has been collated to prove the above criteria they can put forward to be officially classified as persistent organic pollutants (POPs) under the Stockholm Convention. The Stockholm Convention is an international environmental treaty, signed in 2001 and effective from 2004, that aims to eliminate or restrict the production and use of POPs. PFOA has been classified as a persistent organic pollutant (POP) since 2009 and PFOS is currently on the list of chemicals under consideration 

The fluorinated side-chain polymers, the end-products used on clothing, are themselves generally not considered to be of environmental concern. The molecules are so large that they are not easily taken up by cells and if they can’t be taken up the assumption is they can’t cause direct harm. They persist in the environment, but they are ‘inert’ (unreactive). However, once they are present in the environment they can break down and the side-chains that make up the larger polymer molecule can become detached. When free of the stabilising polymer structure, these smaller non-polymers may be of environmental concern. Fluoropolymers are generally considered very stable under most environmental conditions although certain methods of incineration could theoretically lead to breakdown.  

The PFASs of environmental concern are the non-polymer fluorinated surfactants. Of these there are two groups, the Perfluorinated Carboxylic Acids (PFCAs) and the Perfluorinated Sulfonic Acids (PFSAs) used in the production of textiles. Within these groups the best known and most studied are perfluorooctanoic acid (PFOA) and perfluoroocatanesulfonic acid (PFOS), respectively. Historically these were widely used in the production of fluorinated polymers and textile finishes. However, since the wide-spread recognition of their risks and the introduction of regulations and voluntary phase-outs, many companies have reduced or eliminated their use, often substituting for short-chain varieties of the same chemical group.  

The short-chain PFASs are much less studied than their predecessors so the evidence for their environmental safety is still inconclusive. Whilst some studies have shown they are less toxic and don’t bioaccumulate to the same degree1 there is still concern amongst academic groups that some should still be considered PBTs and be classified as ‘of environmental concern’. The huge range of chemicals that fall within each group makes it extremely difficult to accurately assess the safety of each chemical individually. See below for further information.  

PFASs have been found in the blood serum of the general population, more than 99% of Americans tested had PFOS and PFOA in their blood. Whilst background levels are generally low, occupational exposure or ground-water contamination can raise levels significantly amongst local populations.  

Long-chain PFASs 

Studies have shown that some forms of PFAS can be harmful to animals. There have also been many population studies that have shown associations between PFAS exposure and various adverse effects on humans. Most focus on PFOS and PFOA in blood serum but some have a broader focus, looking at multiple PFASs. Given the cocktail of chemicals we are exposed to in our everyday life, and even specific to PFASs, the multitude of these chemicals we can be exposed to simultaneously, it is extremely difficult to isolate the specific effects of individual chemicals. Whilst the effects on humans are not well understood studies have suggested links to possible growth, learning, or behavioural problems, cancer, immune system disorders, fertility problems and obesity (12,36-38) 

The most commonly studied chemicals within the group, and the focus of regulatory actions across the EU and elsewhere, are PFOS and PFOA. Official classifications include ‘carcinogenic’ (Cat2, suspected human carcinogens), ‘reprotoxic’ (Cat 1B, presumed human reproductive toxicants), ‘Lact’ (may cause harm to breast-fed children), and ‘toxic to specific organs’ (liver) (39). The toxicity of lesser studied forms of PFAS, increasingly used as alternatives to the restricted substances, are still uncertain. 

PFASs are either absorbed orally or inhaled, absorption through skin is considered negligible (40). Most persistent organic pollutants build up in the fat tissues of animals, PFASs are different in that they do not easy bind to fats and therefore build up in proteins instead (41). They are mainly found in ‘well-perfused tissues’, these are tissues which have a good blood supply such as the liver, kidneys and spleen, they are found in testes and brains (42-44) 

Short-chain PFASs 

Evidence regarding the safety of short-chain PFASs, increasingly being used as substitutes for long-chain versions as regulations and voluntary phase-outs limit their use, is still extremely lacking. Animal experiments where the subjects are exposed just once or over a short period, have suggested the toxicity of short-chain PFASs is low. However, when exposure is repeated, or larger doses are used, there is evidence to suggest they may cause damage to the liver and kidneys. A general pattern of increasing liver toxicity has been seen as the chain length increases until approximately C9 (45). 

There is also worry regarding the potential of some short-chain PFASs to bioaccumulate, or build up in animal tissue, more than initially thought. One particular short-chain PFAS (PFBA – see below) has shown up in human tissue, including human brains, suggesting it can be more bioaccumulative in humans than some of the experimental animal studies originally concluded (44). There is still a significant volume of unanswered questions regarding how these substances build up in the body, what levels they can reach and what effects they have.   

Specific examples of better-studied short-chain PFAS are listed below:

A type of PFSA similar to PFOS, it contains 6 carbons in its chain (C6). This chemical has a half-life of up to 8.5 years in humans. This means that it takes 8.5 years for half of the chemical to be removed from the human body once it gets in, it takes another 8.5 years for the new amount to half again after that and so on. For reference, the half-life of PFOS is only 5.6 years (46). It has also been suggested to have reproductive toxicity (40) (i.e. it can interfere with normal reproduction either through fertility or development effects on the child) and behavioural disorders such as ADHD (47)

Another replacement for PFOS used by Scotchguard, it contains 4 carbons in its chain (C4). It has a chemical half-life of less than a month in humans but is still thought to persist in the environment. Studies suggest that a dose 50 times higher than the equivalent in PFOS was required to have the same effect on the liver48. Whilst some other health impacts have been noted these often occur at very high doses.  

A type of PFCA, similar to PFOA, it contains 4 carbons in its chain (C4). The half-life for human blood is thought to be approximately 3 ½ days (40). Despite its short half-life in blood, an analysis of Spanish autopsy tissues showed surprisingly high levels of PFBA (100 times higher than PFOS) in lung tissues. PFBA also showed the highest concentration of the measured PFSAs in the kidneys and was found in livers and brains (44). PFBA appears to act differently in humans compared to experimental animals so whilst some adverse effects have been detected in animals little is known about the human toxicity (40). 

Another type of PFCA, similar to PFOA, which contains 6 carbons in it chain (C6). The half-life for humans is thought to be approximately 32 days (40). Most biomonitoring studies have found concentrations of PFHxA in human blood serum to be near or below the detection limit with higher levels only really observed near industrial sources (49). Very little is known about the health impacts of PFHxA.

[1] Eggers Pedersen K, Basu N, Letcher R, Greaves AK, Sonne C, Dietz R, Styrishave B. Brain region-specific perfluoroalkylated sulfonate (PFSA) and carboxylic acid (PFCA) accumulation and neurochemical biomarker Responses in east Greenland polar Bears (Ursus maritimus). Environmental Research 2015;138:22-31.

[2] Barber JL, Berger U, Chaemfa C, Huber S, Jahnke A, Temme C, Jones KC. Analysis of per- and polyfluorinated alkyl substances in air samples from Northwest Europe. J Environ Monit 2007;9(6):530-41.

[3] Ahrens L, Gerwinski W, Theobald N, Ebinghaus R. Sources of polyfluoroalkyl compounds in the North Sea, Baltic Sea and Norwegian Sea: Evidence from their spatial distribution in surface water. Marine Pollution Bulletin 2010;60(2):255-260.

[4] Yamashita N, Kannan K, Taniyasu S, Horii Y, Petrick G, Gamo T. A global survey of perfluorinated acids in oceans. Marine Pollution Bulletin 2005;51(8):658-668.

[5] Ahrens L, Felizeter S, Ebinghaus R. Spatial distribution of polyfluoroalkyl compounds in seawater of the German Bight. Chemosphere 2009;76(2):179-184.

[6] Zushi Y, Tamada M, Kanai Y, Masunaga S. Time trends of perfluorinated compounds from the sediment core of Tokyo Bay, Japan (1950s-2004). Environ Pollut 2010;158(3):756-63.

[7] Muller CE, De Silva AO, Small J, Williamson M, Wang X, Morris A, Katz S, Gamberg M, Muir DC. Biomagnification of perfluorinated compounds in a remote terrestrial food chain: Lichen-Caribou-wolf. Environ Sci Technol 2011;45(20):8665-73.

[8] Magali Houde, ‡, Jonathan W. Martin, Robert J. Letcher, Keith R. Solomon a, Derek C. G. Muir*, ‡. Biological Monitoring of Polyfluoroalkyl Substances:  A Review. 2006.

[9] Kim S-K, Kannan K. Perfluorinated Acids in Air, Rain, Snow, Surface Runoff, and Lakes: Relative Importance of Pathways to Contamination of Urban Lakes. 2007.

[10] Melissa M. Schultz, Douglas F. Barofsky a, Jennifer A. Field*, ‡. Quantitative Determination of Fluorotelomer Sulfonates in Groundwater by LC MS/MS. 2004.

[11] Ericson I, Domingo JL, Nadal M, Bigas E, Llebaria X, van Bavel B, Lindstrom G. Levels of perfluorinated chemicals in municipal drinking water from Catalonia, Spain: public health implications. Arch Environ Contam Toxicol 2009;57(4):631-8.

[12] Hansen KJ, Johnson HO, Eldridge JS, Butenhoff JL, Dick LA. Quantitative characterization of trace levels of PFOS and PFOA in the Tennessee River. Environ Sci Technol 2002;36(8):1681-5.

[13] Michael S. McLachlan, Katrin E. Holmström, Margot Reth a, Berger U. Riverine Discharge of Perfluorinated Carboxylates from the European Continent. 2007.

[14] Möller A, Ahrens L, Surm R, Westerveld J, van der Wielen F, Ebinghaus R, de Voogt P. Distribution and sources of polyfluoroalkyl substances (PFAS) in the River Rhine watershed. Environmental Pollution 2010;158(10):3243-3250.

[15] Bryan Boulanger, John Vargo, Jerald L. Schnoor a, Keri C. Hornbuckle*. Detection of Perfluorooctane Surfactants in Great Lakes Water. 2004.

[16] Nobuyoshi Yamashita, Kurunthachalam Kannan, ‡, Sachi Taniyasu, Yuichi Horii, Tsuyoshi Okazawa, Gert Petrick a, Gamo‖ T. Analysis of Perfluorinated Acids at Parts-Per-Quadrillion Levels in Seawater Using Liquid Chromatography-Tandem Mass Spectrometry. 2004.

[17] Yeung LWY, Dassuncao C, Mabury S, Sunderland EM, Zhang X, Lohmann R. Vertical Profiles, Sources, and Transport of PFASs in the Arctic Ocean. Environ Sci Technol 2017;51(12):6735-6744.