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. https://www.ncbi.nlm.nih.gov/pubmed/17554424 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.

The Science

Per- or poly-fluorinated alkyl substances (PFAS) are a group of over 4,700 industrial chemicals, they all share a similar molecular structure, a ‘carbon chain’, and the element, ‘fluorine’. This carbon-fluorine bond is incredibly strong, which makes PFAS extremely difficult to break down.

Types of PFAS

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.

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.

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 this chain length, 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.

 

types of pfas diagram

PFAS is not a chemical, but a term used to describe a whole group of chemicals which have a similar molecular structure, or ‘carbon chain’, and a specific element, ‘fluorine’. There are more than 3000 types of PFAS commercially available on the world market today.

Polymer PFAS are used on our non-stick pans and clothing

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.

 

Structure of PFAS based polymer finishes diagram

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.

Are all PFAS harmful?

Not all PFAS are made equal. The very large polymer PFAS, e.g. PTFE or fluroinated side-chain polymers used as textile treatments, are often considered to be too big to be taken up by our bodies, and therefore unlikely to cause us any harm.

However, harmful non-polymer forms of PFAS are used in the production of PFAS polymers. These harmful forms can also be created as the polymers breakdown. Until recently, PFOA and PFOS were the most commonly used PFAS in production of these 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. These are sometimes referred to as C8 PFAS, based on their chain length. In light of both voluntary initiatives and legal restrictions, there has been an increase in the use of ‘C6’ PFAS, some of which are themselves now under restriction or being considered for restrictions.

Whilst acknowledging that there may be PFAS that are not directly harmful to humans or the environment, to ensure truly sustainable use, the full chemical life-cycle of any product needs to be understood. Additionally, a lack of evidence of harm does not constitute, and should not be considered as, evidence of safety.

POPFREE

We are excited to be participating in POPFREE, an international, multi-stakeholder research project with the goal to find alternatives to PFAS chemistry in many different consumer products.

The 3-year project began in December 2017 and is organised by a Swedish research consortium, with participants from across Scandinavia, Europe and the world.

The aim of the project is to link up retailer and industry knowledge with state of the art research labs, analysing PFAS-free alternatives by looking at specific requirements of different products. For example, what characteristics are we looking for in stain-resistant school uniforms, compared to stain-resistance in ambulance jackets? As well as looking at textile coatings, the project will examine fire-fighting foams, paper coatings, ski waxes and other consumer products. The project will include careful analysis of any PFAS-free alternatives, to assess environmental impact and ensure PFAS coatings are replaced with safe alternatives.

Our role in the project will be to provide links between POPFREE and UK retailers, carry out consumer surveys and help to share results with industry and the public.