Developing an Approach to Groundwater DQRA for PFAS

Per- and poly-fluoroalkyl substances (PFAS) are a broad group of synthetic fluorinated chemicals which are persistent in the environment. Some are bio-accumulative and toxic, and/or highly mobile. PFAS are used in a wide variety of consumer products and industrial applications because of their unique chemical and physical properties, including oil, water and stain repellence, temperature and chemical resistance, and surfactant properties.

PFAS are widespread within the water environment because of the direct and indirect pathways into groundwater and surface water from various applications and activities.

The need for a consistent approach to assessing the risk of PFAS compounds to groundwater receptors is growing substantially due to increasing year on year attention to PFAS as an emerging contaminant, from the public, media, regulators, and industry. It is becoming more vital that we, as regulators, and industry, are able to understand the risks associated with PFAS and can provide robust and consistent regulation in this emerging field.

Detailed Quantitative Risk Assessments (DQRAs) are an important tool used to assist our understanding of the potential risks posed to receptors from PFAS. The National Groundwater Team at the Environment Agency has identified that as DQRAs with a PFAS focus are being undertaken more frequently by industry, there is a need to provide a consistent approach to our review process.

This project will be completed in two parts as follows:

1. Undertake a literature review of UK and international resources to identify evidence-backed robust physio-chemical data sources for the 16 PFAS identified as hazardous substances in the JAGDAG 2025 list of hazardous substances and non-hazardous pollutants (Table 1 - shown below) that could be used as inputs into a DQRA.
2. Produce a summary table of appropriate physio-chemical data and data sources for the 16 PFAS.

Table 1

Substance: CAS Number

Hexafluoropropylene Oxide Dimer Acid (HFPO-DA or GEN-X) : 13252-13-6

Perfluorobutane Sulfonate (PFBS): 375-73-5

Perfluorodecane Sulfonic Acid (PFDS): 335-77-3

Perfluorodecanoic Acid (PFDA): 335-76-2

Perfluorododecanoic Acid (PFdoDA): 307-55-1

Perfluoroheptane Sulfonic Acid (PFHpS): 357-92-8

Perfluorohexane Sulfonate (PFHxS): 108427-53-8

Perfluorohexanoic Acid (PFHxA): 307-24-4

Perfluorooctane Sulfonate (PFOS): 1763-23-1

Perfluorononane Sulfonic Acid (PFNS): 68259-12-1

Perfluorononanoic Acid (PFNA): 357-95-1

Perfluorooctanoic Acid (PFOA): 335-67-1

Perfluoropentane Sulfonic Acid (PFPeS): 2706-91-4

Perfluorotetradecanoic Acid (PFTetraDA): 72629-94-8

Perfluorotridecanoic Acid (PFTriDA): 376-06-7

Perfluoroundecanoic Acid (PFUnDA):2058-94-8

List taken from the 2025 updated JAGTAG table of confirmed hazardous substances: www.wfduk.org/sites/default/files/… ↗ 04 14 Confirmed hazardous substances list.pdf

The literature review and summary table will be completed over a four-month timeline, using the Environment Agency's Literature Review Guidance document, which provides guidance as to how literature reviews should be completed to align with Environment Agency requirements.