Formatted Title

PFAS Soil and Groundwater Threshold Limits in Europe: What Should We Do when PFAS Are Not Regulated?

Background/Objectives

Threshold limit values for soil and groundwater are not defined in some European countries, and PFAS specific regulatory frameworks have been elaborated. On the other hand, the diffuse presence of this persistent type of contaminants is now widely recognized, not only by the regulators and industry but also by the public, whose exposure has not been comprehensively quantified by specific epidemiological studies, nor background values in soil or groundwater have been derived in most countries. In recent years, European agencies have become increasingly aware of PFAS environmental exposure risks. In Belgium and the Netherlands, there has been, and still is, significant media attention regarding soil and groundwater contamination with PFAS. This, in turn, has created political pressure on the existing soil- and groundwater legislation. In the Netherlands and Flanders (Belgium), construction sites and ongoing groundwater remediation came to a standstill under this pressure. Exceptionally, for these countries, projects were even halted through Court Orders.  As a result, laws, procedures, and threshold values for PFAS had to be drawn up quickly to provide a modicum of legal certainty to ongoing programs. When dealing with a potentially contaminated site or during a site assessment in the context of a due diligence for a site acquisition shall we, as part of the industry, look at the presence of PFAS? No “formal” liabilities if compared to the regulatory requirements could be recognized, however how a potential impact of these constituents can be quantified? The objective of this work is to provide a 
perspective for the assessment of PFAS in the environmental matrices in the absence of specific regulations, referring, specifically,to the measures developed in Flanders ranging from the introduction of “no-regret zones and no-regret measures” and establish a temporary framework for action. 

Approach/Activities

The absence of specific threshold concentrations for at least some selected PFAS in groundwater, but mostly in soil, needs to be addressed as the public awareness for the presence of these recalcitrant compounds is now recognized as widespread in the environment. In some European countries where no regulations are yet in place, different scientifically based approaches have been adopted. To define an acceptable approach, a review of the few options that are available has been undertaken and shared with the authorities. As a first cut, threshold limit values that have been derived in some European Countries (such as, Belgium and the Netherlands), in various States of the USA, and in Australia were compared, analyzed and reviewed to understand whether the concentrations detected at a site could be within the ranges of “acceptable concentrations” as defined in some countries. To cope with the rapid pace at which new insights, ranging from toxicological, chemical to analytical, regarding PFAS are acquired, in Flanders, no-regret areas and associated no-regret measures were introduced. As soon as an elevated PFAS value, exceeding the applicable threshold value, is detected or a site is considered as “PFAS-suspected” based on its history, a radius of 100 meters is established around it and designated as the no-regret area in which, no-regret measures are declared. This comparison will only provide an indication of the need of further assessment. In fact, the knowledge of PFAS transport in the environmental matrices is still a matter of continuous development, as well as the lack of epidemiological studies that could sustain the classical toxicological approach that is usually adopted to derive threshold or site-specific values. The question of the need of time-bounded or preliminary or uncertain threshold concentrations is open, given the lack of agreement in the various threshold values that are proposed worldwide. Based on experience in recent years, in Flanders and in the Netherlands, so-called Temporary PFAS Frameworks were introduced to build in legal certainty, with respect to soil and groundwater investigation, and remediation including soil reuse. Based on a chronological evaluation, over the past 2 years (2021 to 2023), the impact of the introduction of these procedures, legislation and threshold values and the changes to these measures over time is discussed. Several confidential Flemish case studies will be evaluated to assess this specific impact, ranging from financial, public perception to legal validity. A site-specific approach may be more suitable to address PFAS concentrations, especially in soil. In fact, it is now recognized how the primary pathway of concern from soil is the potential impact on groundwater. Hence, it is crucial to derive soil threshold concentrations that may represent remediation targets, only once site-specific data have been collected and the pathway has been assessed in a robust conceptual site model. 

Results/Lessons Learned

The evaluation and discussion of the case studies identifies regulatory challenges, shortcomings and lessons learned, as well as potential future challenges remaining in place. The presented evaluation will focus on the consultancy and engineering firms’ point of view; how consultants react and support clients’ needs. The example of Flander, after the introduction of the first Temporary PFAS Framework and this evaluation can serve as starting point or inspiration for other countries coping with emerging PFAS awareness and challenges.  Based on the review of case studies developed in different countries, by different engineering/consulting firms, a few options are available to derive soil threshold concentrations: 1) site-specific leachate concentrations based on the application of Leaching Environmental Assessment Framework (LEAF), developed by the US Environmental Protection Agency (EPA). 2) site-specific pore-water concentrations collected trough the use of lysimeters. These data must be combined with site site-specific geological and geochemical parameters and used in analytical or numerical models to simulate transport from the vadose zone to groundwater. Also, based on available literature, Brusseau and Guo, 2023, “Revising the EPA dilution-attenuation soil screening model for PFAS”, a revised modelling approach could be adopted, given the unique properties and associated retention behavior of PFAS and specifically, the distribution parameter used to convert soil porewater concentrations to soil concentrations, to account for adsorption at the air-water interface. As an example of adopting site-specific approaches, in the absence of soil threshold concentrations were requested in Switzerland and Italy, and it is believed that will be useful for developing improved soil target concentrations that can be used to enhance site investigations and management for PFAS-impacted sites.