UK legal limit: 0.1 µg/L (sum of PFAS). Find out what pfas is, its health effects, and how to check and reduce it in your tap water.
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PFAS — per- and polyfluoroalkyl substances — are a group of over 12,000 synthetic chemicals that have been used in industry and consumer products since the 1940s. They are found in non-stick cookware (PTFE), waterproof clothing, food packaging, firefighting foam, and hundreds of other applications. In the UK, PFAS have been detected in tap water supplies served by 14 of the 21 water companies currently under active DWI (Drinking Water Inspectorate) improvement notices.
The reason PFAS are called "forever chemicals" is straightforward: they contain carbon-fluorine bonds that are among the strongest in all of chemistry. This makes them extraordinarily resistant to biological and environmental breakdown. Once they enter the water cycle — from industrial discharge, landfill leachate, or agricultural use of PFAS-containing sewage sludge — they persist almost indefinitely.
PFAS are endocrine disruptors — they interfere with hormone signalling in the body. Research published in peer-reviewed journals has linked long-term PFAS exposure to disruption of thyroid hormone function (PFAS compete with thyroid hormone for binding proteins), suppression of the immune system (reduced vaccine response has been documented in children), increased risk of certain cancers (kidney, testicular) at high exposure levels, and effects on reproductive hormones including oestrogen and testosterone.
Crucially, most of the health evidence relates to occupational or high environmental exposure — typically far above the levels found in UK tap water. The DWI's current advisory limit for the sum of all PFAS is 0.1 µg/L, set conservatively. Most UK water companies report PFAS well below this level, though the presence of active improvement notices indicates ongoing monitoring and treatment investment is required.
As of March 2026, the following 14 water companies hold active DWI PFAS improvement programmes: Thames Water, United Utilities, Severn Trent, Yorkshire Water, Southern Water, South West Water, Anglian Water, Affinity Water, Essex & Suffolk Water, South Staffordshire Water, Cambridge Water, Portsmouth Water, Northumbrian Water, and Welsh Water. These notices require companies to investigate sources, install treatment, and reduce PFAS concentrations — they do not mean current water is unsafe.
Standard activated carbon jug filters (Brita, etc.) do NOT reliably remove PFAS. Granular activated carbon (GAC) can partially reduce some PFAS but is not certified for full removal. The only filter technology certified for PFAS removal to NSF/ANSI 58 standard is reverse osmosis (RO). A quality RO system certified to NSF/ANSI 58 will remove 95–99% of PFAS from tap water. Look for the NSF mark on the product or certificate — not all RO systems are certified for PFAS specifically.
The DWI's position is that tap water under improvement notice remains safe to drink under current guidelines. The improvement notices are precautionary — triggered by the detection of PFAS above investigation thresholds, not necessarily above health-based limits. However, for households with infants, pregnant women, or immunocompromised individuals, installing an NSF/ANSI 58-certified RO filter provides additional reassurance. Enter your postcode below to check your water company's current PFAS status.
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PFAS (per- and polyfluoroalkyl substances) are synthetic chemicals used in non-stick cookware, waterproof clothing, food packaging, and firefighting foam. They are called 'forever chemicals' because the carbon-fluorine bond resists all natural breakdown, meaning they persist in the environment indefinitely.
14 of 21 UK water companies hold active DWI PFAS improvement notices as of March 2026. Enter your postcode to check your water company's status. PFAS are present at very low levels — most zones remain within DWI advisory limits.
Most health concerns relate to high occupational or environmental exposure. UK tap water levels are very low. However, PFAS are endocrine disruptors and accumulate in the body. The precautionary approach is to use a certified RO filter if you have concerns.
No. Standard activated carbon jug filters (Brita, ZeroWater) do not reliably remove PFAS. Only reverse osmosis (RO) systems certified to NSF/ANSI 58 are certified for PFAS removal.
Only reverse osmosis (RO) filters certified to NSF/ANSI 58 are proven to remove PFAS. Look for the NSF certification mark on the product. AquaTru and Waterdrop G3 are among the RO systems certified for PFAS removal.
As of March 2026: Thames Water, United Utilities, Severn Trent, Yorkshire Water, Southern Water, South West Water, Anglian Water, Affinity Water, Essex & Suffolk Water, South Staffordshire Water, Cambridge Water, Portsmouth Water, Northumbrian Water, and Welsh Water. Check the DWI website for the latest register.