Sometimes known as Forever Chemicals, Poly- and perfluoroalkyl substances (PFAS) are a group of synthetic organic chemicals. These chemicals are used in everyday products such as cosmetics, cookware, food packaging and clothing because of their heat, oil and water-resistant qualities. They’re often also used to make firefighting foams, electronics and medical equipment. Meaning that you’ll come across these chemicals quite often in your daily life without even realising.
PFAS and Drinking Water
What are the regulations?
In March 2025, the Drinking Water Inspectorate (DWI) published updated guidance for PFAS in drinking water, requiring water companies in England and Wales to monitor for a wider range of PFAS and to update their risk assessments accordingly. They have identified actions a water company must take if a site has detections at a tier 2 level or above. A site identified as tier 2 is medium risk, with tier 3 being deemed a higher risk.
Read more about the tier criteria.
How are we responding?
At Yorkshire Water, we test for PFAS compounds as part of our routine sampling schedule at all untreated waters that directly supply a water treatment works and we test treated water for medium and higher risk sites. We also risk assess all our raw water sources and water treatment works to make sure our drinking water meets the high standards set by our regulator, the DWI.
Based on current knowledge from the DWI, the low levels of PFAS detected in some untreated water in the UK has no acute or immediate impact on human health.
We’re at the start of a five-year plan to understand and investigate potential PFAS sources for tier 2 sites. Currently there are no water treatment works at tier 3.
How will we reduce PFAS concentrations in our water?
Once the investigations have been completed, we’ll create mitigation plans to reduce PFAS concentrations in the water. Those mitigations plans are to be made by the end of the five-year period (2030) and will be in line with the DWI guidance for PFAS. During this time, PFAS concentrations will continue to be monitored.
Actions being taken to investigate the tier 2 sites to date include:
- Increased sampling frequency to understand how and if PFAS concentrations change over time
- Sub-catchment sampling upstream of abstraction points
- Catchment hazard map creation
- Liaison with local stakeholders to understand potential PFAS sources.
The information will then provide evidence for when mitigation plans are made.
PFAS concentrations are routinely monitored and so any changes to water quality will be detected and investigated accordingly whilst working closely with the DWI.
View our interactive PFAS map to understand what tier your water supply system sits in.
PFAS at our wastewater treatment works
Why is there PFAS at the wastewater treatment works?
We have a network of around 20,000 miles of underground pipes, collecting the raw sewage from the region's homes, liquid waste from industry, and rainwater that falls on roofs and roads. We operate over 600 wastewater treatment works, which are designed to treat expected sewage volumes and meet the standards set by the Environment Agency. PFAS chemicals can be seen at our wastewater treatment works because of the use of them domestically and industrially, and their presence in rainfall.
What are the regulations?
Hazardous substances in UK surface waters are controlled by Environmental Quality Standards (EQSs). Only one PFAS, Perfluorooctanesulfonic Acid (PFOS), has Environmental Quality Standards. PFOS EQSs exist for inland surface waters, transitional and coastal waters, and fish. The remaining 12,037 PFAS on the USEPA’s CompTox database have no Environmental Quality Standards, but this may change in the next few years because of the white paper from the government in response to the 2025 Independent Water Commission.
How are we responding?
Our company is involved in a major national programme to better understand and reduce PFAS in wastewater and the environment. As part of the Chemical Investigations Programme Phase 4, led by UK Water Industry Research, we’re tracing the sources of PFOS entering six of our sewer networks and will work directly with the businesses responsible for significant PFOS discharges, to reduce their impact. This monitoring is running until March 2027. We’re also monitoring PFOS and PFOA every month at five of our wastewater treatment works, contributing to a long-term national study that is showing both chemicals have been steadily decreasing in treated effluent over the last decade.
We’re expanding this monitoring to areas where we discharge into rivers, groundwater, and land, testing up to 23 different PFAS at these locations. Additional studies are underway to understand how PFAS behave in sludge, soils, and agricultural land, including large national projects sampling biosolids and modelling PFAS movement in the environment.
What research are we doing?
We're also supporting research into potential treatment solutions. These include testing how integrated constructed wetlands remove PFAS and looking at whether advanced thermal conversion technologies can destroy them. Finally, we're helping to lead a UK-wide study into whether PFAS can move from biosolids amended soil into crops, with results due in 2027.
Overall, this work forms one of the most comprehensive PFAS research efforts in the UK. We need to remember that PFAS is everywhere, even if all wastewater treatment works final effluent had zero PFAS, the reduction of PFAS in rivers would be miniscule, as a result of the multiple other sources and pathways.