Disposable food packaging (bags, plates, cups, lunch boxes, etc.) made of cellulose fibers, must exhibit resistance to hot liquids (water and fats) in order to be able to match, in terms of performance functions, the “less ecological” packaging produced from plastics, such as expanded or extruded polystyrene (EPS, XPS). Until now, those responsible for the so-called barrier properties of paper products were PFAS substances, which, as it turns out, do not decompose at all in the environment, thus making the whole product an environmental nuisance. However, it is interesting to note that packaging made of cellulose fibers containing these substances, although they have already been withdrawn and banned in many countries, are still produced in the world, sold and used in Poland, and in addition are labeled as “green”, “ecological” or even “compostable” packaging. In this article, I try to introduce you to the problems associated with the use of PFAS substances and to make you aware of the risks caused by their impact on our health and the environment. The publication also contains information on the synthesis and properties of these chemical compounds and the scope of their use in various areas of economic life. Due to the barrier function they apparently still play in packaging for the food sector, I draw attention to the side effects caused by their presence. At the same time, I propose alternatives that are safe for the environment and our health. I briefly describe the formal and legal status related to efforts to phase out the use of certain PFAS substances. The article thus provides a review of the literature, where it is easy to find explanations of such terms as, for example, ECHA, REACH, EFSA, SVHC, POPs, SUP, biodegradability, compostability and many others related to this issue.
Origins of the problem
Even the most inaccessible areas of the Earth are already contaminated with plastic today. Between 5 and 13 million tons of plastic end up in the seas and oceans each year. Over the past 50 years, global plastic production has increased more than twenty times and is projected to further double by 2035 and quadruple by 2050. Therefore, the problem is increasingly urgent. It should be noted that a significant percentage of current production is made up of single-use plastics, that is, plastics that are designed to be used once, in a short period of time (Agenda 2016).
As of May 2023, some of the guidelines of the SUP Directive (Directive on single-use plastics) took effect. Voted on in 2019, the SUP Directive, the European Union’s regulation on single-use plastics, was a watershed moment not only for users but especially for plastic packaging manufacturers. Its main goal was and still is to protect our planet by reducing the environmental impact of plastic products. The legislation deals with the imposition of administrative fines for failure to ensure the availability of packaging alternatives to plastic packaging (Kiessling et al. 2023). The directive obliges all EU countries to implement several changes, in particular, to promote alternatives to single-use plastic. In this way, so-called extended producer responsibility (EPR) systems are being implemented. Each member state is tasked with encouraging users to reach for reusable products or single-use solutions, made from raw materials other than plastic. The best alternative to plastic packaging was supposed to be, and I believe still is, paper, which is a plastic made from a natural polymer such as cellulose. However, it was given several ambitious challenges (including barrier properties), after which it could compete with plastic. As a result, packaging made from cellulose fibers, which, under the aegis of paper products, are considered biodegradable and environmentally friendly, have become increasingly fashionable on the market. Their sensational barrier properties boldly take advantage of the achievements of modern chemical technology. In one case, it is paper coated with a thin polyethylene film (e.g., beverage cups), making it a multilayer (composite) material, extremely cumbersome from the point of view of recycling. In another case, it is paper containing PFAS-type substances (e.g., catering packaging), which, like plastic, does not degrade easily. So is there any rational and truly environmentally friendly alternative for the packaging industry?
What is PFAS
PFAS, or so-called “forever chemicals,” accumulate in nature, and therefore also in the bodies of humans and animals, where they can damage the endocrine, immune, and reproductive systems. Per- and polyfluoroalkyl compounds (PFAS) are a vast group that includes thousands of synthetic chemicals that have numerous applications in various areas of economic life. All such compounds contain carbon-fluorine bonds, some of the strongest bonds found in organic chemistry. This makes them exceptionally resistant both to damage or destruction during their use and to breakdown once they cease their functional role. Most PFAS compounds easily migrate in the surrounding environment, from which they are difficult to remove or annihilate. Therefore, the biggest problem caused by PFAS compounds is contamination of groundwater, surface water and soil. Cleanup of contaminated areas is technically difficult and expensive. They can take thousands of years or longer to decompose, and the cost of treating the effects of these substances in Europe, for example, is estimated at 50-80 billion euros a year (Cordner et al. 2021). If these compounds continue to be released, the environmental pollution problem will grow.
A source of toxicity
The ability to attach halogens (i.e. fluorine, chlorine and bromine) to carbon atoms on a commercial scale has only been mastered by chemists in the last 80 years. They have accomplished something that nature does very rarely. Substitution of hydrogen atoms with fluorine atoms in the carbon chain results in fully (per-) and partially (poly-) fluorinated alkyl substances, called PFAS for short.
Perfluorinated compounds are characterized by full substitution in the hydrophobic carbon chain of hydrogen atoms with fluorine atoms. This group includes carboxyl derivatives (e.g. perfluorooctanoic acid), sulfonates (e.g. perfluorooctanesulfonate), sulfonamides (e.g. perfluorooctane sulfonamide), as well as esters, salts and fluorides. Their surfactant properties increase as the amount of carbon-fluorine bonds increases, which makes them widely used, including as household chemicals (e.g., impregnants for leather, carpets, fabrics, etc.). The process of synthesizing these compounds is carried out using hydrofluoric acid and a carbon compound and a high-voltage electric current. In this way, a bond of very high strength is formed. After certain modifications, these compounds can be polymerized, thus obtaining Teflon coatings resistant to heat and solvents. On the other hand, modifications involving the attachment of a polar group (e.g., phosphate, sulfate or carboxylic acid) at the end of the carbon chain produce surfactants with incredible properties.
As mentioned earlier, the C-F bond is the strongest bond in organic chemistry and almost never occurs naturally in nature. Therefore, natural degradation processes (e.g. UV exposure) or biodegradation (e.g. enzymatic decomposition caused by microorganisms), cannot cope with the breakdown of these chemical bonds.
One could say that since nature didn’t create such bonds itself, it now doesn’t know how to break them apart. The halogenated carbon skeleton is very stable and persists in the environment for an unspecified, but very long period of time (Vierke et al. 2012). Compounds that are lipophilic, i.e. have an affinity for oil or fat, as opposed to water, lead to their retention in living organisms. It is their ability to bioaccumulate, their persistence and their effects that cause cancer or other damage to internal organs (Buck 2020; Hu et al. 2019; Sunderland et al. 2019) that have made chlorinated, brominated and fluorinated carbon compounds the most toxic and polluting group of chemicals found in the planet’s environment (Ackerman and McRobert 2020; Chambers, Hopkins, and Richards 2021; Starling et al. 2014). The same group of hazardous substances includes DDT (dichlorodiphenyltrichloroethane), PCBs (polychlorinated biphenyls), chlorofluorocarbons, dioxins and furans, among others. Thus, the binding of halogen and carbon atoms made it possible to create new molecules with interesting and useful properties, but, as it later turned out, properties were highly harmful to human and animal health.
Applications of PFAS
There are many groups of PFAS-type substances, covering a total of more than 4,700 different compounds (Buck 2020). PFAS compounds exist as gases, liquids, or high molecular weight solid polymers. Hence, among other things, their wide range of physical and chemical properties, as well as their widespread use in many areas of economic life. One of their most important properties is their high stability under conditions of intense heat exposure. The most desirable feature, however, from a practical point of view, is their ability to simultaneously repel oil and water, evenly distribute firefighting foams and make fabrics resistant to various types of contamination (Glüge et al. 2020). Major industries that use PFAS include aerospace, defense, automotive, medical and packaging.
Of the many examples of PFAS applications, the one that has attracted the most attention in recent years is the food packaging industry, which has direct contact with food (e.g., burger wrapping papers, bakery contact papers, pizza box liners, take-out containers of the molded catering packaging type, etc.). In this case, PFASs act as surfactants. These substances are used to coat the surface of packaging or are added directly to the pulp during the manufacture of packaging (Schaider et al. 2017; Seltenrich 2020; Semple et al. 2022).
Risks of using PFAS
Scientists and government agencies around the world, such as the European Chemicals Agency (ECHA), the Community agency responsible for implementing the REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) Regulation, and the European Food Safety Authority (EFSA), were the first to recognize the harmful effects of PFAS substances on human health and the environment. Large-scale studies have shown that food papers (coated or impregnated with PFAS compounds) contribute an average of 250 ng PFAS/day to the average consumer’s unintentional intake (Tittlemier et al. 2007). Most PFASs permanently accumulate in the environment, resulting in an ever-increasing threat of their toxic effects on living organisms. As long as PFAS continue to be released into the environment, humans and other species will be exposed to increasing concentrations of these compounds (Abunada, Alazaiza, and Bashir 2020; Ahrens and Bundschuh 2014; Evich et al. 2022; Ghisi, Vamerali, and Manzetti 2019, 2019; Kurwadkar et al. 2022; Manojkumar et al. 2023; Sima and Jaffé 2021; Spyrakis and Dragani 2023; Teunen et al. 2021, 2021; Wang et al. 2020; Zhang et al. 2023). Even if PFAS emissions could be stopped in the near future, they will continue to be present in the environment and in the bodies of humans and animals for generations to come. Some PFAS are known to accumulate in the bodies of humans, animals and plants, causing unpleasant health effects. Some of these chemicals have been identified as extremely toxic to fetal development. Others cause cancer, and still others disrupt the human endocrine system (Hu et al. 2019; Manojkumar et al. 2023; Schaider et al. 2017; Seltenrich 2020; Starling et al. 2014; Sunderland et al. 2019; Susmann et al. 2019).
REACH regulations and restrictions
As a result of research performed mainly between 2019 and 2023, a number of compounds in the PFAS group have been identified as substances of very high concern and, as a result, have been placed on the SVHC (Substances of Very High Concern) list. SVHCs were identified based on their persistence, mobility and toxicity, which were found to pose a threat to human health and wildlife. It turned out that drinking water was the most at risk of contamination by PFAS. The substances were also found to be of serious concern, comparable to carcinogens, mutagens and reproductive toxicants, denoted by the acronym CMR (cancerogenic, mutagenic or toxic to reproduction). Based on studies performed under ECHA’s supervision, these compounds have been classified as persistent, bioaccumulative and toxic, designated by the acronym PBT (persistent, bioaccumulative and toxic), and as very persistent and very bioaccumulative, designated vPvB (very persistent and very bioaccumulative), due to their extreme persistence.
The EU’s chemical strategy for sustainable development today puts PFAS policy in the spotlight. The European Commission is committed to phasing out all PFAS, allowing their use only when they are proven to be irreplaceable and necessary for society.
Biodegradability and compostability
According to the definition, biodegradation is a process in which a material breaks down and is decomposed by microorganisms (e.g., bacteria, fungi, algae) into naturally occurring substances, such as CO2, water and biomass, leaving no harmful compounds behind. Biodegradation can occur in an oxygen-rich environment (aerobic biodegradation) or in an oxygen-poor environment (anaerobic biodegradation). Biodegradable packaging, therefore, is that which is biodegradable to the degree and time specified by the EN-13432 standard. It is, therefore difficult to imagine, for example, paper packaging containing PFAS substances, which would show biodegradability. Biodegradability is determined by 90% conversion of the carbon contained in the test material to carbon dioxide within 180 days (Song et al. 2009; Zakowska 2009). Composting, on the other hand, is a method of producing a valuable organic fertilizer – compost. Organic waste is transformed during composting by a variety of microorganisms into simple compounds that can enrich the soil for growing crops. Compostable products decompose into water, carbon dioxide and nutrient-rich fertilizer. This process is usually carried out under controlled conditions (e.g., industrial composting plants). It follows, therefore, that the two terms – biodegradability and compostability – should not be used interchangeably. Compostable products must be biodegradable. However, biodegradable products are not necessarily compostable at all. For example, PFAS-coated paper will contaminate the resulting compost with C-F compounds. As the cellulose fibers decompose, the PFAS compounds will enter the compost, then the soil, from where they will be absorbed by crops and finally end up in the organisms of livestock consuming the crops. It’s not hard to guess that this is one of the ways toxic compounds can be deposited in human bodies (Brändli et al. 2007; D’eon and Mabury 2011; Lee et al. 2021).
PFAS-free packaging – XyloMatrix
The proposed ban on single-use plastics should be complemented by a requirement that paper products be certified as “compostable and PFAS-free.” Such certification would, for food contact products, guarantee products that are safe for our health. There are already effective alternative coatings for food contact packaging materials. Coatings made of starch, chitosan, alginates, micro- and nanofibrillated cellulose, and gelatin are an increasingly popular solution. They provide adequate oil barrier properties, but exhibit relatively poor moisture resistance without appropriate chemical modification. Plant proteins, including soy, wheat gluten and corn zein, have been tested as coatings for paper creations (Mazela, Tomkowiak, and Jones 2022). Sealing agents, such as alkyl ketene dimers, alkenylsuccinic anhydride and rosin, improve moisture resistance, but in turn are poor barriers to oils and fats. The difficulty in finding a viable replacement for PFAS agents that is cost-effective, fully biodegradable and environmentally safe underscores the need for further research to improve barrier properties and process economics in food packaging products (Glenn et al. 2021; Hannah n.d.; Song et al. 2009).
In September 2023, Przedsiębiorstwo Wielobranżowe sp. z o.o. in Michorzewo launched Poland’s first production of packaging for direct food contact using the thermoformed cellulose fibers (molded fibers) method. The technology is doubly pioneering, as the packaging has high barrier properties against hot liquids (water and oil) without the use of PFAS-type chemicals (Mazela et al. 2023). The concept of achieving barrier properties without the use of environmentally burdensome chemicals was developed in cooperation with BIM Kemi Sweden AB and is still being developed. The company is open to cooperation, not only in selling safe disposable packaging, but also with scientific and research institutions and the socio-economic environment interested in promoting truly green solutions for the packaging industry.
Banning single-use plastic packaging solves one problem, but at the same time generates new problems. Disposable plastic food containers are being replaced by paper packaging and cardboard. These, in turn, are often coated with toxic substances in order to get the right properties to compete with plastics. About half of these food-grade paper creations are coated with per- and polyfluorinated alkyl substances (PFAS), which give these products resistance to water and oil. Unfortunately, as we already know, these substances are toxic to the environment, as they bioaccumulate in living organisms, causing disease entities in them. The threat to human health comes mainly from their ability to migrate from the packaging into the food we eat. To make matters worse, during composting, PFAS substances accumulate in the soil, from which they are in turn absorbed by plants. Most likely, many paper products labeled as compostable are not at all, due to the presence of environmentally harmful substances in them.
In the face of emerging new challenges, it is worth noting the initiatives taken by small companies, often of a startup nature, which are taking bold steps toward developing technologies that are safe for human health, ecological and environmentally friendly.
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