Contamination from PFAS (Per- and Polyfluoroalkyl Substances) is now causing significant impacts and delays for brownfield regeneration projects. Jake Hurst and Simon Rawlinson examine how robust, risk-based management of PFAS can help developers to bring forward sites even as regulations are toughened up.
PFAS have been causing growing concern and gaining increasing attention from the public, media and regulators for many years. The persistence and mobility of PFAS in the environment has resulted in widespread diffuse contamination as well as contaminating sensitive drinking water supplies across the globe. The scale and potential impacts of PFAS in the environment are huge and still emerging with some commentators describing PFAS as the new asbestos.
While certain sectors have been assessing PFAS for many years, PFAS discharges and historic land contamination are now areas facing increasing scrutiny. As a result, mainstream development sites are now experiencing significant challenges with examples of developers being told to re-run site investigations as well as insurers shying away from insuring projects, potentially leaving sellers with stranded assets and retained liability.
Unique Properties Make Unique Problems
The properties which make PFAS so useful such as resistance to degradation, mobility and surface activity are often the same properties which have resulted in the widespread presence of PFAS and the associated difficulties with its management. Their persistence means there can be shallow soil contamination present decades after original use and their mobility means there can be extensive groundwater contamination, found at significant distances from the site and point source release.
Sites where fluorosurfactant firefighting foams may have been used for training, incident response and spray testing at locations such as airports, military bases and petrochemical and industrial sites which store bulk flammable liquids.
Sites which may have manufactured or used PFAS. PFAS have been used by nearly every industrial sector at some point, so should be considered across a wide range of sites. High risk sites include fluoropolymer manufacturing, ‘non-stick’ coatings for textiles, carpets, paper products as well as metal plating, and electronics.
PFAS are also prevalent in wastes and end up in landfills and landfill leachates as well as wastewater treatment works (WWTWs) where in many cases, they are poorly removed. As a result, PFAS have been identified in WWTW discharges and biosolids which may be applied to land as fertiliser.
Evolving PFAS Regulations
Regulations and guideline values for PFAS continue to evolve globally with a trend towards regulating a larger range of PFAS compounds and groups of compounds to even lower acceptable limits. In the UK, regulatory drivers affecting brownfield redevelopment typically come from the drinking water guidelines and surface water standards which are used to inform compliance criteria for site assessment and remediation. Soil Screening Levels (SSLs) are currently available for PFOS and PFOA but don’t reflect risks to human health or water resources. More detailed Category 4 Screening Levels (C4SLs) for PFAS are currently under development.
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Recent global developments in PFAS regulations include the US EPA introducing a Significant New Use rule preventing companies from the manufacture or processing of 329 PFAS without a complete EPA review and risk determination (January 2024). In addition, the US National Primary Drinking Water Regulation (NPDWR) (April 2024) now restricts six PFAS, including PFOS and PFOA. In the European Union (EU), the proposed broad restriction on all PFAS currently under review with the European Chemicals Agency (ECHA), is likely to be enforced in EU Member States in 2025 and the EU Chemicals Strategy for Sustainability towards a Toxic free Environment aims to ban all PFAS except for essential uses.
Concerns have been raised regarding uncertainties in PFAS toxicology and as the scientific understanding and regulations regarding PFAS evolve, any future changes could have major impacts on both the UK drinking water sector and at sensitive brownfield sites.
PFAS Assessment and Management Approaches
It is important to incorporate the latest understanding, tools and guidance on PFAS within our existing approaches to make sure we robustly conceptualise sites and take a risk based, pragmatic approach to the implementation of site management. This involves looking outside the site boundary to establish background levels in order to place any PFAS detections in context. Clients and their representatives need to understand how PFAS might have been used previously and where the source areas might be located. Every site is unique and has its own history which must be investigated. The PFAS problem goes well beyond airports and fire training areas.
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We must move away from the mindset of only looking for individual PFAS. The problem is similar to petrol or diesel contamination where we are dealing with complex mixtures. PFAS mixtures typically contain ‘precursor’ PFAS that are not detected by routine analysis methods, and these precursors can ‘biotransform’ over time into toxic and regulated PFAS. This hidden and unregulated PFAS mass can be greater than the amount of individual and regulated PFAS, so is crucial to understand the true magnitude and longevity of the source.
Further challenges that the risk based PFAS management approaches must address include:
The sheer volume of potential PFAS sources and widespread detections in the environment, particularly as these detections may be above quality standards. The ‘end points’ for a site remediation should be set within the wider context of the site, including relevant background concentrations that should not require management.
The concentration requirements set out in PFAS standards and guidance are often very low and as PFAS do not biodegrade, even more detailed, site-specific assessment of PFAS fate and transport still result in very low thresholds to remediate or manage.
Data on the physical and chemical properties of certain PFAS is either limited or absent altogether. Further studies to assess PFAS toxicity, which underpins current standards, are needed.
PFAS are present within construction materials which also need to be assessed and managed to support appropriate reuse, waste circularity and disposal.
PFAS Remediation
Remediation of PFAS in soils and waters can be more challenging than for traditional contaminants for several reasons, however, cost effective and sustainable technologies are available and are being increasing deployed and optimised. Widespread impacts and low treatment criteria require approaches that target source areas and first concentrate the PFAS and then destroy this PFAS, often employing multiple technologies in ‘treatment trains’ to address the range of PFAS that are likely to be present.
Further challenges that the risk based PFAS management approaches must address include:
Remediation of PFAS in soils and waters can be more challenging than for traditional contaminants for several reasons, however, cost effective and sustainable technologies are available and are being increasing deployed and optimised. Widespread impacts and low treatment criteria require approaches that target source areas and first concentrate the PFAS and then destroy this PFAS, often employing multiple technologies in ‘treatment trains’ to address the range of PFAS that are likely to be present.
Treatments have to address a number of challenges including:
PFAS do not biodegrade and so bioremediation approaches which are used widely for other organic contaminants are not suitable.
Landfill leachate is often not effectively tested or treated for PFAS potentially resulting in emissions to the environment and liability concerns.
PFAS require high temperatures to volatilise or destroy the contamination. This makes thermal approaches very costly and generally less sustainable.
The range of PFAS and diverse properties presents unique challenges. For example, shorter chain PFAS are less readily removed by Granular Activated Carbon (GAC) or other approaches relying on hydrophobic sorption. Precursor PFAS are often less well studied.
Novel destructive techniques, such as Super Critical Water Oxidation (SCWO) and sonolysis are currently less established but are being deployed and optimised at field scale..
PFAS are present within construction materials which also need to be assessed and managed to support appropriate reuse, waste circularity and disposal..
Increasing awareness and regulatory requirements around PFAS across the brownfield sector can cause additional costs and delays if not foreseen. While PFAS can be effectively managed through the UK’s existing contaminated land management frameworks, the approach taken needs to reflect new challenges and complexity that PFAS bring – in particular, the need to work within a context of widespread background levels of PFAS in the environment. PFAS need to be considered at a greater range of sites and during the initial stages of a project, ensuring a robust characterisation of the types of PFAS that are potentially present is obtained.
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The UK’s regulatory landscape is changing rapidly and there is a need to look ahead and learn from global best practice to anticipate and manage potential future liabilities. There is also a clamour for more guidance and suitable screening levels to provide confidence to stakeholders managing and insuring brownfield sites.
However, while the challenges of PFAS to the sector are real and many projects are facing hurdles, the UK brownfield sector is adaptive and has a track record in managing complex, novel contaminants. There are already site assessment approaches and remediation techniques that are suitable for PFAS, and there is a huge amount of innovation taking place. Responding to the PFAS challenge at brownfield sites is a journey that requires collaboration between industry, regulators and all stakeholders to manage PFAS effectively but also to target efforts pragmatically alongside wider restrictions on the use of PFAS.
