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1 Drivers and Pressures: Why Are PFAS in Soil and Groundwater of Concern?

Reports of findings of perfluorinated and polyfluorinated chemicals (PFAS) in groundwater and soil are increasing worldwide. Knowledge about PFAS in soil is of increasing concern, as PFAS can be transferred from soil to groundwater or from soil into crops. Insufficient and incomplete knowledge and understanding of the fate and behaviour of PFAS, their physical-chemical properties, persistence, accumulation and other effects in environmental compartments, in humans and the retrieval from material flows and cycles have favoured developments that have led to an aggravation of the problem. For example, lack of understanding but also carelessness lead to imprudence in product development and user behaviour. This favoured an increasing input of PFAS into the environment as well as the generation of problematic wastes.

The substance group of PFAS represents a challenge for environmental protection. The extraordinary scale, significant limitations of technical approaches, economic burdens to solve the problems additionally require a comprehensive strategy driven by knowledge and excellence and based on state-of-the-art research. This article addresses the current state of knowledge, management and policy issues regarding PFAS in soil and groundwater.

1.1 What Are PFAS and What Are They Used For?

Fluorochemistry is present within our daily lives, however, most people are not aware of it. The range of uses for PFAS is wide. PFAS give products outstanding properties; dirt and water repellence combined with high stability against heat, chemicals, UV-radiation. The applications are diverse and range from finished textiles, carpets, grease-repellent food packaging, to paints and impregnation of wood and tiles. Certain PFAS are used as emulsifiers in fluoropolymer production, such as polytetrafluoroethylene (PTFE), traces of PFAS can still be present in the final products. Fluoropolymers are used in various products to reduce either frictional drag (e.g. as coatings in automobiles and aircraft, in printing inks, waxes and lubricants) or adhesion (e.g. in cookware). PTFE is also widely used as a waterproof and breathable membrane i.e. in weather protective clothing.Footnote 1

The abbreviation PFAS stands for a still increasing group of more than 5000 man-made chemicals.Footnote 2 The unique properties of PFAS are based on their common structural feature: a perfluorinated or polyfluorinated carbon chain. The atomic bond between carbon and fluorine is one of the strongest known in chemistry. A lot of energy is needed to break this bond. PFAS can only be mineralized at very high temperatures. This also means that PFAS are not broken down under natural environmental conditions. Although the non-fluorinated molecule moiety of polyfluorinated substances (so called precursors) can be degraded, the fluorinated moiety remains persistent. Neither biotic processes (e.g. bacteria) nor abiotic processes (water, air, light) can completely destroy these molecules and so they remain in the environment for a very long time.Footnote 3

1.2 PFAS Are Distributed in the Environment Through Various Sources

PFAS are emitted into the environment during their entire life cycle, i.e. from the production of the chemicals, through their use phase, to the disposal of related waste (see Fig. 1). Point sources of PFAS include facilities where PFAS are produced and used. These can be, for example, chemical companies but also textile finishing industry, paper manufacturers, leather processing industry, electroplating plants, manufacturers and users of fire extinguishing agents, manufacturers of electronics and electrical engineering.Footnote 4 Landfills can also be a source of the chemicals. PFASs here can escape into the air or may be washed out with the leachate. Incineration plants may emit PFAS into the environment. Municipal and industrial wastewater treatment plants are among the most important point sources of PFAS in the environment. The pollutants are introduced into wastewater, for example, by washing textiles that have been treated with PFAS. The persistent perfluorinated chemicals are not degraded during the treatment stages in the wastewater treatment plant. PFAS are carried into surface water, but also adsorb to particles and accumulate in sewage sludge. If sewage sludge is applied to the soil in agriculture, e.g. as fertilizer, the soil is contaminated with PFAS. Increased PFAS levels in soil and groundwater are caused by the use of PFAS containing fire extinguishing foams. These so-called film-forming foams are used especially for extinguishing burning liquids (so-called AFFF foams).Footnote 5

Fig. 1
A diagram of P F A S pathways that originate from factories, intermingle with household products, and travel through various mediums into our food chain, affecting human health.

PFAS pathways in soil and groundwater; source Umweltbundesamt 2020a

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1.3 Properties & Behaviour of PFAS in the Environment

Fate and behaviour of PFAS in the environment is different compared with other substances known to be problematic (such as dioxins, heavy metals or polychlorinated biphenyls (PCB)). Footnote 6

Due to the large number of substances, individual PFAS have very different properties. Some are water-soluble, others adsorptive, still others gaseous. Once the chemicals enter the environment, they enrich in different environmental media and remain there for a very long time. Especially the fully fluorinated compounds (perfluorinated) are resistant against transformation under environmental conditions and metabolism in plants, animals and humans. PFAS are therefore called forever chemicals. Footnote 7

For decades, the persistence of PFAS has been seen as unproblematic, because with the standard test protocols, PFAS were found to be non-toxic. In recent years, it has become apparent that this original assessment was wrong. Because of the numerous applications, the chemicals are ubiquitously present in the environment, today. As they are so persistent and cannot be degraded under environmental conditions, they accumulate steadily in the environment. They are found in water, sediment, air and soil, biota, even in remote areas such as the Arctic.Footnote 8 Some PFAS are bio-accumulative and enrich along the food chain.Footnote 9 Thus, PFAS are found in top predators even in human blood of the general population.Footnote 10 Other PFAS accumulate less in humans, they are more mobile and can therefore contaminate ground and fresh water more quickly and are taken up into plants. Their toxicity is estimated to be lower, partly because of the lower accumulation potential in the body.Footnote 11 However, human- as well as eco-toxicological basis data are still developing and might change existing risk assumptions and legal value setting. So, the more science is learning about these substances, the more scientists become aware of their effects. It is therefore time to address these substances and take actions at a global level to protect humans and the environment from even higher pollutant loads.

1.4 PFAS Levels in Humans May Be Linked to PFAS in Soil

Humans take up PFAS mainly via food but also via inhalation of dust and air; thus, mainly from the environment.Footnote 12 More and more studies show how problematic PFAS are for humans. Today we know that some PFAS have extremely long half-lives in human blood and are toxic.Footnote 13 There is even evidence that high PFAS blood levels reduce vaccine efficacy in children.Footnote 14 This may be of special concern in view of the Covid-19 pandemic.

A study on human blood samples stored in the German specimen bank analysed a spectrum of 37 PFAS and found two prominent PFAS (perfluorooctanoate—PFOA and perfluorooctanoic sulphate—PFOS) in every sample of the 2009–2019 dataset. The results of this study indicate a decrease in human exposure to known PFAS in Germany over the last three decades.Footnote 15 However, an official German human biomonitoring study on blood of children and adolescents came to the result that still one fifth of the participants in this study had concentrations of PFOA in their blood that were above the so-called Human-Bio-Monitoring values (HBM-I) level. This level is defined in such a way that if it is exceeded, harmful effects cannot be ruled out with sufficient certainty.Footnote 16

Because of the known effects on human health, human intake of PFAS must be reduced. Therefore, many countries have applied guidance values or threshold values for drinking water.Footnote 17 The European Food Safety Agency (EFSA) has derived tolerable weekly intake rates (TWI) firstly in 2008 for PFOS and PFOA. In 2018 EFSA updated its assessment and published drastically lower values in 2018. Recently, the EFSA Panel on Contaminants in the Food Chain (CONTAM) decided to include epidemiologic data in its assessment resulting in a TWI of 4.4 ng/kg body weight for the sum of four PFAS in 2020 (Table 1).Footnote 18

Table 1 Tolerable weekly intakes of PFAS determined by the European Food Safety Authority (EFSA)18
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The outcome of EFSA’s latest assessment is the driver for a number of other regulations to tighten values, e.g. in the EU Drinking Water Directive, where PFAS are now to be considered. The new EU Drinking Water Directive (EU 2020/2184) includes limits for total PFAS of 0.5 μg/L and the sum of 20 PFAS of most concern of 0.1 μg/L. The new directive entered into force on 12th January 2021, with EU Member States having a 2-year transitional period to develop national laws, by 12th January 2023.

The link between drinking water limits and soil protection is obvious. The lower the PFAS content in the soil, the less groundwater is contaminated. The lower the PFAS levels in groundwater, the less costly it is to provide clean drinking water from groundwater resources. The link between PFAS levels in food and soil protection is also evident. The lower the PFAS contamination in agricultural soils, the lower the uptake in plants and animals and the lower the amounts in human food. Moreover, using PFAS polluted groundwater for irrigation will again pollute soil as well as food and feed.

2 State and Dimension of PFAS Contamination in Germany and Europe

2.1 PFAS in Soil & Groundwater

Nowadays it seems PFAS can be found everywhere, at most places in low concentrations, but there are also hotspots with very high concentrations in soil or water. Data of the German specimen bank show that concentrations of the regulated substances are decreasing in environmental samples. The situation is, however, different for unregulated substances. Here we see increasing concentrations in some samples such as in terrestrial organisms and plants. But having in mind the large group of compounds, it is impossible to monitor all PFAS—thus the dark figure is probably remarkable higher.Footnote 19 But even if the levels are decreasing in certain environmental media, the substances do not disappear. They are only shifted to other compartments. Researchers are still debating the global PFAS sink—it might be marine sediments and (marine) predators.

The first PFAS case in Germany was already reported in 2006. In the Moehne reservoir in North Rhine-Westphalia, which serves as a drinking water reservoir, exceptionally high PFOA and PFOS concentrations were measured. The people who were unknowingly supplied with PFAS-contaminated drinking water, presumably for years, showed elevated PFAS levels in their blood. This was investigated in long-term studies and thus first results on long-term behaviour and effects of PFAS in humans were derived. In further studies, anglers who consumed PFAS-polluted fish from Lake Moehne were also included in the investigations. The reason for the PFAS-pollution is most probably the (illegal) application of contaminated organic waste mixtures and soil improvers on agricultural land.Footnote 20 The subsequent intensive discussion of the topic showed that the causes of contamination of soil and water with PFAS are diverse throughout Germany and that the cases are numerous. For example, one of the cases is in Bavaria, where PFOA was detected in soil, groundwater and surface water samples from a 230 km2 area near an industrial area with fluoropolymer manufacturers and users.Footnote 21 In Baden-Wuerttemberg, Germany, a water supplier detected PFAS contamination in drinking water in 2013, which it voluntarily tested for PFAS. Subsequent investigations revealed that soils and groundwater in the regions of Rastatt, Baden-Baden and Mannheim were contaminated with PFAS. It is suspected that the PFAS contamination was caused by mixtures of paper sludge and compost applied to agricultural land over several years. In the region of central and northern Baden, a mosaic of areas totalling 1200 hectares is contaminated with PFAS, in some cases significantly. The contaminated land comprises 12% of the arable land within the area.Footnote 22

Nationwide, however, many PFAS contaminations of soil and groundwater are mainly related to the use of fluorine-containing firefighting foams during firefighting operations and exercises, and to the use of PFAS-containing process materials in industrial plants, e.g. in electroplating, textile finishing. Duesseldorf Airport is mentioned here as representative of almost all airports. The groundwater contamination at Duesseldorf Airport also led to the contamination of a surrounding lake with PFAS, the use of which is therefore prohibited by the authorities. The lengthy remediation process will continue to incur high costs in the future. In other cases, well closures followed, so that irrigation of private gardens was no longer possible.Footnote 23

Today we know there are a number of PFAS contaminated sites within Germany and most probably in every other country as well. An unpublished query of the German Laender Authorities about the PFAS contaminated sites yielded the following result: In 2019 about 1635 sites were under suspicion to be contaminated with PFAS, even about 685 sites were under investigation, 76 in remediation and 11 sites are remediated. And these numbers are a restricted of so far 8 from 16 Federal States only. These figures are often not the results of a systematic approach due to the fact that PFAS analytics is not yet fully integrated into standard field measurements.

Targeted investigations have mostly concentrated on point-sources inputs on areas suspected of being contaminated (airports including military sites, major fires using PFAS-containing fire extinguishing foams, disposal of contaminated sewage sludge) and have continuously improved the data situation for such cases. Nevertheless, this will always remain case specific information, which at best allows a quantitative, but not a qualitative and area-specific statement. To overcome this, a better and more comprehensive monitoring approach is required. Competent authorities see a massive gap of research referring to site investigation, especially in, regulated analytical methods and values, transfer-factors soil-(animal)-plants/crops, assessment criteria and remediation and management approaches.

Monitoring data on groundwater contamination across Europe stated that PFAS are widely detected in European groundwater above limits of quantification (Voluntary “Groundwater Watch List” (GWWL) Group of WFD CIS Working Group Groundwater 2020). However, European Member States usually analyse PFAS only when there is a suspected case. The EU network “Common Forum of Contaminates Sites” initiated a data collection in 2020 in which some EU Member States participated. It became clear that there is still no comprehensive and complete overview of PFAS incidents in soil and groundwater. The Common Forum also highlighted lacks of specific analytical and detection methods and methodological bases for the investigation, the assessment and for site-specific decisions in case of pollution.Footnote 24 The effectiveness of available remediation technologies is very limited. the improvement of the knowledge base and exchange of experiences will make it possible to deal more efficiently with contaminated sites caused by newly emerging pollutants.

First studies on background contamination in soil have been published recently, indicating that PFAS are ubiquitously present in soil.Footnote 25 Unfortunately, the substance group or certain individual representatives of PFAS are not yet part of the standard analytic routines in relevant environmental media and transfer pathways. So, analytical investigation and their actual validity as well as applied monitoring schemes are not able to detect and investigate the diversity of individual substances in the substance group of PFAS systematically.

2.2 Conditions for Risk Assessment/Uncertainties

PFAS in the environment or soil mostly originate from emissions of previously unregulated PFAS. However, there are also many documented incidents of accidental releases. To track such releases, it is important to distinguish between low-level background contamination and legally relevant incidents. PFAS background levels are caused exclusively by anthropogenic substances and activities. It cannot be ruled out that PFAS used in the recent past may also currently result in airborne emissions into the soil, which would lead to a sustained increase in background levels. Moreover, an increase in background levels might reach a risk level for potential receptors with comprehensive consequences for any management option with regard to excavated soils and their disposal or re-use. An associated increase in groundwater concentration will lead to restrictions in further use (e.g. drinking water purposes and irrigation.)

In order to clarify these assumptions a suitable investigation approach and standardised analytical methods are required and should be harmonised. These processes should be investigated and, if necessary, continuously monitored.

Most laboratories can only analyse a small part of the large group of PFAS. A German standard protocol lists 13 PFAS that can be analysed in water and soil samples. Some laboratories are able to analyse a spectrum of up to 40 PFAS. Nevertheless, a large number of substances remain undetected. The problem is that most PFAS are difficult to detect. One possibility is to use sum parameters or a so-called Total Oxidizable Precursor Assay.Footnote 26 Here, the unknown polyfluorinated substances (precursors) are degraded under harsh conditions in the laboratory to the perfluorinated PFAS, which can then be analysed using standard methods. However, not all PFASs are detectable with this method, but a much better understanding of the dimension of PFAS contamination in soil or water is gained. Other sum parameters such as extractable organic fluorine (EOF) or absorbable organic fluorine (AOF). May also be used to gather the dimension of a PFAS pollution in soil or groundwater.Footnote 27 In summary, PFAS analysis is expensive and laborious and cannot be performed by every laboratory. Thus, pressure also arises from a high degree of uncertainty, which comes in particular from a lack of analytical procedures and the consequent incomplete results of site investigations and monitoring data for PFAS. If non-detectable PFAS keep widely unconsidered by analyses, uncertainty remains on what dimension and influence just this part of the PFAS spectrum will have in its harmful effects on humans and the environment.

A detailed understanding of fate and transport of PFAS in the environment is essential to assess the risks occurring from contamination and to develop reliable conceptual site models. Such derivations are also complicated because a large number of different PFAS are present. Data to predict transport and fate are not available for most PFAS and for investigated ones a wide range of physical-chemical properties have been shown.

Precursors into perfluorinated and persistent PFAS (e.g. PFOA and PFOS) under environmental conditions has to be considered in risk assessments, model predictions and conceptual site models. To date, there is insufficient knowledge to safely predict actual risks, hazards and impacts PFAS. In consequence may be, an under- or overestimation of occurring risks, legal value setting might be inadequate as well as the criteria of related mitigation and remediation measures.

3 Responses

3.1 Regulation of Import, Manufacturing and Use of PFAS Within the EU

Over the past 20 years scientists have outlined how PFAS behave in the environment, how they accumulate, what effects they show in humans and the environment, and how they enter the environment. As a result, some measures have been taken to reduce PFAS emissions into the environment.Footnote 28

At international level, one representative of the group-PFOS- was identified as a persistent organic pollutant (POP) and added to the list of the world’s most harmful substances in 2009 (the Stockholm Convention) und thus most uses are banned at international level.Footnote 29 In 2019 another substance followed—PFOA—known as C8 or perfluorooctanoic acid. PFHxS—perfluorohexanoic sulfonate—a third PFAS has already been identified to fulfil the criteria to be a POP and has been added to Annex A of the Stockholm Convention in 2022. The substances listed in the Stockholm Convention are banned because they are persistent, bioaccumulative and toxic and can be transported over long distances and reach remote areas. The EU regulates substances listed under the Stockholm Convention via the EU regulation on persistent organic pollutants (REGULATION (EU) 2019/1021). The EU further restricted manufacturing, use and import of some other PFAS (Table 2). Additionally, some PFAS have been identified as substances of very high concern and have been added to the so-called Candidate List for authorization. The properties of concern that are the basis for regulation are stated in Table 2 below. However, most PFAS are still unregulated. Scientists have stated the need for immediate action.Footnote 30 The European Chemicals Agency (ECHA) has proposed a restriction proposal for firefighting foams containing PFAS. The EU Commission’s decision is foreseen in the course of 2023. Moreover, within the EU the ban of the whole group of PFAS was prepared by Germany, Denmark, Netherlands, Norway, and Sweden and a restriction proposal was submitted to the European Chemicals Agency (ECHA) in January 2023. The restriction proposal aims to reduce emissions into the environment and make products and processes safer for people. The proposal includes all uses except those identified as essential. As a next step the scientific committees for risk assessment and socioeconomic assessment will prepare opinions. The adopted opinions will be sent to the European Commission for the final decision on the potential restriction.

Table 2 Regulation of PFAS within the EU; European Chemicals Regulation (REACH)
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Many specific research and regulatory issues there is also the need for a comprehensive strategy for emerging pollutants. The European Commission therefore launched a non-toxic environment ambition and a PFAS-Action Plan.

However, environmental policy is often a response to negative or even irreversible effects that have already occurred. A general change is needed in order to strengthen precautionary principles. Therefore, a management approach for emerging pollutants is meaningful and a comprehensive PFAS strategy might be used as blue print.

Finally, the detection of PFAS in soil or groundwater results in authorities having to decide how to deal with the situation. Whether remediation is possible, the soil must be excavated and disposed of, or whether the entire area may have to be closed to certain uses.

3.2 Dealing with PFAS Contaminated Soil & Groundwater in Germany

Until recently, in Germany there were no legal binding values available for PFAS in soil. The Federal States that were already confronted with PFAS contamination in soil and groundwater had already developed their own rules for dealing with the damage. However, these were different, so that there were various solutions on how to deal with excavated soil containing PFAS, for example. This resulted, among other things, in PFAS-containing excavated soil not being accepted by some landfills and being able to be disposed of in other Federal States without any requirements. Thus, it was necessary to have common recommendations for the uniform nationwide assessment of soil and water contamination and for the disposal of soil material containing PFAS. The harmonised guidance is an agreement of certain committees, such as the committee for preventive soil protection, the committee on contaminated sites, and the committee for waste disposal. The recommendations have recently been published and can now be used until the ful set of legal regulations is available.Footnote 31

In Germany the greatest attention is paid to groundwater protection regarding PFAS. In 2017, so called insignificance thresholds values were derived for PFAS in groundwater.Footnote 32 The insignificance threshold values for PFAS are based on human toxicological impacts and on the provisions of the German Drinking Water Ordinance. These insignificance thresholds are also used for the assessment of soil or soil material. For this purpose, soil eluates are prepared and analysed for PFAS. The 2021 revision of the German Federal Soil Protection and Contaminated Sites Ordinance includes the insignificance threshold values as trigger values for the soil-groundwater pathway. However, the latest results of the EFSA assessment have not yet been considered in the derivation of the significant threshold values. It needs to be clarified whether this makes sense, as it might lead to extremely low levels that are hardly measurable.

For the deposition of soils so far, no binding rules are available. Thus, the guidance sets recommendations, which levels in the materials are tolerable for unrestricted open emplacement, restricted open emplacement in areas with elevated PFAS concentrations, and restricted emplacement in technical structures with defined safety measures.

Sewage sludge used as soil fertilizer must not exceed 100 μg/kg total PFOS plus PFOA in Germany. Where the concentration exceeds 50 μg/kg this must be indicated on the label. The limit value introduced in 2008, however needs to be updated, as it represents the knowledge from that time, e.g. the fact that the precursors contained in the sewage sludge are disregarded. Today especially having in mind the low EFSA values, it seems careless to allow such high PFAS levels to be applied to soil. The application of sewage sludge might result in the insignificance threshold value in groundwater being exceeded, subsequently. As mentioned before, in Germany some large areas of agricultural land are polluted with PFAS. Thus, solutions had to be found by local authorities to deal with the situation. The land has been polluted with mainly those PFAS were neither regulations nor guidance was available regarding human health. Therefore, authorities implemented a so-called pre-harvest monitoring to ensure that highly contaminated food and feed do not reach the market. A number of studies have been carried out to find out which plants readily take up PFAS and which plants are suitable for cultivation on polluted soils.

3.3 Measures: Remediation and Management

Once soil is contaminated with PFAS , e.g. through the use of sewage sludge or firefighting foams containing PFAS, it can take years for PFAS to leach into the groundwater. Some PFAS are extremely mobile and are hardly retained by the soil. Therefore, they are very rapidly translocated from the soil to the underlying water phase. Thus, competent authorities need science-based support in selecting, evaluating, and decision-making about appropriate and proportionate remediation solutions and management approaches. This includes consideration of the legal framework in order to be able to order flanking measures without discretionary error as competent authority. Furthermore, advantages and disadvantages of the different approaches, technical and legal requirements, but also their sustainability are important criteria to find a suitable remediation option. PFAS contaminated sites represent enormous challenges for the management of contaminated soils and groundwater. Thus, to support competent authorities in decision making a handbook containing a toolbox as a working aid was developed with the support of experts from Germany and Switzerland.Footnote 33 The working aid describes the PFAS-specific fundamentals that are essential and relevant for subsequent remediation decisions. This includes, in particular, the impact pathways and receptors, the designation of competent authorities and affected legal areas, as well as information on sampling, lead parameters and precursors.

Further, the handbook is focusing on the remediation of PFAS point sources. This is not fundamentally different from the remediation of conventional pollutants that has been practiced for over 30 years. However, PFAS exhibit some peculiarities that make it advisable to explain them specifically. Additionally, the handbook contains special features of remediation management and options for action are presented i.e. cases where waste legislation need to be considered. Also the current situation in the context of the circular economy in Germany is described and administrative and technical recommendations and assistance are given followed by recommendations for public participation accompanying remediation measures. The handbook moreover contains detailed information of currently applied assessment methods and remediation procedures are presented.

In case soil and/or groundwater remediation is required, the options to ensure destruction of PFAS are indeed cost driving. Destructive PFAS technologies often require treatment times of several hours which make them unsuitable for continuous treatment of pumped contaminated groundwater. They may, however, be used to decontaminate concentrates which arise e.g. after sorbent desorption. The moderate to high solubility of some PFAS and their low sorption capacity to soil are the reasons why PFAS cause long contaminant plumes in the aquifer. So far, such extended aquifer contaminations cannot be remediated cost-effectively with in-situ technologies. Besides pump-and-treat, barrier technologies like Permeable Reactive Barrier (PRBs) are feasible. These systems use reactive materials for adsorption like Granular Activated Carbon (GAC). In addition, there are foam fractionation systems in groundwater circulation wells, which concentrate PFAS dissolved in the groundwater into a foam.

Within case related proportionality considerations decontamination methods will be excluded in many cases due to enormous costs. In-situ-soil flushing, barrier technologies or in the simplest way only point of use or end of pipe decontamination (e.g. within drinking water facilities) could make a difference to this overarching decontamination measures. Further, containment, immobilisation, safety and protection measures offer alternatives, but they are in many cases also not equivalent because they do not eliminate the problem in a sustainable manner. They are often associated with considerable follow-up costs and re-use restrictions for affected sites. Mostly, due to existing limitations in source removal for PFAS, landfilling is seen as “easy alternative”. If excavated soil with remaining PFAS contamination leaves the site interfaces with waste legislation are of relevance. The regulations of a circular economy in Europe are consistently focussed to the goal of avoiding waste or keeping waste within material cycles. PFAS-contaminated soils, which, as shown, cannot be cleaned and for which there are currently no possibilities for subsequent use, increase the mass flow balance without an actual recycling option. Without reliable values for excavated materials, there will be a growing uncertainty for of landfill operators, an increasing deficit on landfill capacities and a decreasing acceptance to landfill PFAS-contaminated materials.

4 Conclusions

This article attempts to illustrate the complex challenges caused by PFAS for man and the environment. A better PFAS-understanding has led to considerable political pressure and a need for action in the national, European and international environment and has addressed numerous legal, scientific and engineering needs.

In the European Union manufacture, use and import of chemicals is controlled via REACH, the European chemicals regulation. Some PFAS have already been identified as substances of very high concern and for some PFAS the manufacture, use, and import are restricted with derogations. However, still a number of uses are allowed, emissions of PFAS into the environment still occur. There are no legal binding requirements for industry emissions into air or waste water—those are urgently needed to efficiently reduce PFAS emissions into the environment. On the other hand, the thresholds for PFAS in drinking water and food are at such a low level, that environmental concentrations are often already above those levels. The article focusses mainly on the PFAS contamination of soil and groundwater in Germany, however, similar cases will most probably exist in many countries. Thus, awareness rising and monitoring is essential to address PFAS contamination.

Therefore, a crucial need for environmental monitoring and environmental law and enforcement requirements for the protection of the affected environmental media need to be addressed. The central pillars are the extension and scope of analytical methods to overcome the uncertainty for non-detectable PFAS. With the accelerated increase in knowledge in the human and ecotoxicological assessment of PFAS exposure and the associated tightening of tolerable limits, a comprehensive reassessment of the state of the environment is necessary. In the result this should reveal numerous regulatory developments and action requirements and demands their immediate implementation. This article presents the enforcement-relevant working aids and guidelines, which are intended to help harmonize enforcement in the Federal States and create methodological foundations for this.

A strategy change is necessary in order to pursue more promising approaches through improved soil monitoring and related data. The German Environment Agency is currently working on the determination of PFAS-background levels in soil. These will be used to derive further measures to assess PFAS levels in soil and groundwater with the aim to protect humans and the environment from PFAS exposure but also to be able to reuse soil. As a first step significance thresholds for groundwater have been derived for some PFAS. They have been included in the amended German soil ordinance. However, these significance thresholds still have to be adapted with regard to new toxicological findings of EFSA.

In the meantime, the currently available media-related assessment bases have been made available in PFAS working aids. The primary purpose is to assist competent authorities in their evaluation of PFAS inputs into water bodies and soil. In addition, the work aid provides summary basics on the substance group of PFASs, on possible remediation and management options, and on the currently available engineering options.

The EU has an ambitious sustainability plan—the European Green Deal. PFAS have been incorporated within the Zero Pollution Ambition and the goal of a non-toxic environment. Nevertheless, and to put it briefly—the best way forward is a PFAS group restriction, e.g. under REACH connected with strict regulation of industrial emissions for the remaining uses. Advocating for concerted international cooperation and successful EU-networking is crucial. Otherwise, we cannot narrow existing gaps between the development and release of new chemical substances and mixtures and successful approaches to protecting environmental media like soils and groundwater.