PFAS 'Forever Chemicals' in UK Tap Water

What are PFAS?

PFAS — per- and polyfluoroalkyl substances — are a family of over 12,000 synthetic chemicals that have been used in manufacturing since the 1940s. You'll find them in non-stick cookware coatings, waterproof clothing, stain-resistant fabrics, fast food packaging, and firefighting foam. They're also used in semiconductor manufacturing, aviation, and dozens of other industrial processes.

They're called 'forever chemicals' because the carbon-fluorine bond at their core is one of the strongest bonds in chemistry. PFAS do not break down naturally — not in soil, not in water, not in the human body. They accumulate in the environment and in living tissue over time. PFAS have now been detected in human blood, breast milk, and tissue samples on every continent, including in people with no known direct exposure.

Health effects of PFAS

The health science on PFAS is still evolving, but the evidence base is substantial and growing. The best-studied compounds — PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate) — have the clearest risk profiles. Key findings include:

• Thyroid disruption: PFAS interfere with thyroid hormone synthesis and transport. Studies link PFAS exposure to hypothyroidism, elevated TSH, and reduced free T4 — particularly in women and children.
• Reduced fertility: Multiple studies associate PFAS with reduced sperm count, altered female reproductive hormones, and increased time-to-pregnancy.
• Oestrogen and testosterone interference: Several PFAS compounds act as endocrine disruptors, binding to hormone receptors and altering signalling pathways.
• Cancer risk: PFOA was classified as a Group 1 carcinogen by the WHO's International Agency for Research on Cancer (IARC) in 2023 — meaning it is definitively carcinogenic to humans, based on evidence for kidney and testicular cancer. PFOS is classified as Group 2A (probably carcinogenic).
• Immune system effects: High PFAS exposure is associated with reduced vaccine antibody response in children, suggesting immune suppression at elevated levels.
• Developmental effects: Prenatal and early childhood PFAS exposure is linked to reduced birth weight, altered immune development, and metabolic effects in infants.

It's important to note that most of this research is at levels higher than those typically found in UK treated drinking water. However, because PFAS accumulate in the body over a lifetime, even low-level chronic exposure contributes to body burden — which is why regulators globally are tightening limits.

PFAS regulation in the UK

The Drinking Water Inspectorate (DWI) operates a three-tier monitoring system for PFAS in treated drinking water:

• Tier 1: Below 0.01 µg/L total PFAS — no action required
• Tier 2: 0.01–0.1 µg/L — investigation and risk assessment required
• Tier 3: Above 0.1 µg/L — immediate investigation and treatment action required

No UK water company has exceeded the Tier 3 level in treated drinking water in 2024. The 14 active improvement notices relate to the detection of PFAS in source water (before treatment) and in some treated water samples at Tier 2 levels — triggering a mandatory programme of investigation and, where necessary, additional treatment installation.

For context, the US EPA introduced a maximum contaminant level of 4 parts per trillion (0.004 µg/L) for PFOA and PFOS individually in 2024 — significantly tighter than the current UK Tier 3 threshold of 100 parts per trillion (0.1 µg/L) for total PFAS. UK regulations are expected to be tightened in coming years.

Which water companies have active PFAS notices?

The following 14 water companies have active DWI PFAS improvement notices, requiring investigation and treatment action by 2031:

Companies without active PFAS notices: Bristol Water, Cambridge Water, Essex & Suffolk Water, SES Water, Hafren Dyfrdwy, Scottish Water.

Does this mean my water is unsafe?

No. All treated UK drinking water is currently within the DWI's guideline values, and no supply has exceeded the Tier 3 action level. The improvement notices are a precautionary regulatory mechanism — they require water companies to identify PFAS sources in their catchments and put treatment in place before levels reach action thresholds.

That said, PFAS are a legitimate long-term concern for several reasons: they accumulate in the body over decades; global regulatory limits are tightening; and some PFAS compounds are confirmed carcinogens at high exposure levels. A precautionary approach — particularly for pregnant women, infants, and those with thyroid or hormonal conditions — is reasonable and is increasingly recommended by health scientists.

PFAS hotspot areas

PFAS contamination in drinking water sources is concentrated around specific land uses where PFAS-containing products have been used historically:

• Airports: Aqueous Film Forming Foam (AFFF), used in aviation fire suppression, contains some of the highest concentrations of PFOA and PFOS ever measured. Groundwater near Heathrow, Gatwick, Luton, Manchester, and other major airports is subject to particularly close monitoring.
• Military bases: AFFF has been used at RAF and Army bases for decades. Groundwater near Lakenheath (Suffolk), Mildenhall, Lyneham (Wiltshire), and Catterick (North Yorkshire) has required investigation.
• Industrial sites: Chemical manufacturing, semiconductor fabs, and textile processing facilities have historically discharged PFAS to local water courses.
• Fire training areas: Sites used for fire-fighting training with foam — including local authority training centres — are PFAS point sources.

What removes PFAS from tap water?

Not all filters are equal when it comes to PFAS:

• Standard activated carbon filter jugs (e.g. Brita): Provide limited and inconsistent PFAS removal. Not suitable for reliable PFAS reduction. Do not rely on a standard filter jug for PFAS removal.
• High-specification activated carbon block filters (NSF/ANSI 53 certified for PFAS): Can achieve significant PFAS reduction when certified specifically for this purpose. Check the NSF certification database before buying.
• Reverse osmosis (RO) systems (NSF/ANSI 58 certified): The gold standard for PFAS removal, achieving 90–99% removal of PFOA, PFOS, and most studied PFAS compounds. Under-sink RO systems (£150–£400 installed) or countertop RO dispensers are the most practical household options.

For households with identified PFAS concerns — near airports, military sites, or in areas with active DWI Tier 2 investigations — a reverse osmosis system is the recommended approach.