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Poly and Perfluorinated Alkyl Substances (PFAS)

Background

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals that include PFOA, PFOS and other related substances. They have been used widely for a range purposes from industrial to household products, that have had or continue to have widespread use in England and Wales. Certain PFAS compounds are known to have the potential to persist in the environment; including in water and some have shown the capability to bioaccumulate. This has raised a keen interest in better understanding their potential impact on the environment and toxicity.

Research and guidance

The Inspectorate provides general guidance on PFAS.

In March 2025, a consolidated guidance document was issued to water companies detailing the Inspectorate’s requirements regarding PFAS monitoring, risk assessment, and strategy in relation to public water supply systems.

The World Health Organization (WHO) has produced a guidance document on PFOS and PFOA in drinking water.

Research into the efficacy of various treatment types on PFAS removal has been published on the Inspectorate’s website, see link to research page. Whilst efficacy varies by type of PFAS, treatment process, and source water characteristics, the research shows that PFAS can be effectively removed from water sources using known water treatment processes. Key findings of the research:

  • Removal performances of nanofiltration and reverse osmosis membranes is typically above 90% for most PFAS.
  • Conventional GAC (Granular Activated Carbon) is effective at removing >6 carbon chain PFAS.
  • Short chain carboxylic acid PFAS were the most challenging to remove.
  • The background water matrix impacts removal, with PFAS more effectively removed from groundwater over upland water and lowland water.

Further research and data gathering on PFAS in water sources and drinking water supplies is ongoing. As we learn more our guidance will become more informed.

Various agencies have commissioned research into the toxicology of PFAS. Local authorities should consult the UK Health Security Agency (UKHSA) or Public Health Wales for more information on PFAS in water used for domestic purposes, particularly where analysis confirms their presence, as health advice will be informed by the specific substance/s found, and their concentrations. It may be necessary for local authorities to keep an open dialogue with UKHSA or Public Health Wales on PFAS.

Private water supply risk assessment

Due to the wide range of PFAS sources entering the environment, and the persistence of the substances, it is recommended that the potential for the presence of PFAS is included when conducting risk assessments of private water supply systems. This should inform the monitoring plan.

When evaluating potential sources of PFAS contamination in drinking water catchments, research has identified a diverse array of contributors, which include but are not limited to:

  • Fire stations and training sites
  • Pollution incident sites
  • Mechanics
  • Air transport sites
  • Military bases
  • Chrome plating sites
  • Carpet, leather, paper, and textile manufacturing
  • Landfill sites
  • Wastewater treatment works
  • Land spreading of sewage sludge and other solid waste.

However, detectable concentrations of PFAS have been found in water where there is no apparent connection to any of these. As such, local authorities should also consider the risk of unknown sources of PFAS in private supplies, where the potential for their presence may exist. Where they are found, due to their persistence and mobility in the environment, the potential area and number of supplies that could be affected, should be considered.

Analysis

Laboratory capability and capacity is expanding, with analytical methods being developed to enable detections of a larger range of PFAS, at ever finer concentrations.

The United Kingdom Accreditation Service (UKAS) is the organisation responsible for accrediting the analytical capabilities of laboratories.

The UKAS website lists laboratories currently accredited for PFAS analysis.

Local authorities should consult with laboratories to establish when there may opportunity for PFAS analysis. In the first instance, it is important for local authorities to understand if any of their supplies are at high risk of the presence of PFAS. High risk supplies can then be prioritised for further action which may include sampling and analysis when it is available. Sources of data and information to help inform risk assessments include the Environment Agency, and local water companies, who are undertaking sampling and analysis of various environmental waters.

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