Forever (PFAS) chemicals in UK drinking water: Should I be concerned

The short answer is yes.

PFAS (“forever chemicals”) are present in some UK drinking-water sources, but the current evidence suggests that for people on a regulated public supply, the risk from drinking water is generally low. The situation is worth monitoring rather than panicking about.

What are PFAS?

PFAS are a very large family of synthetic chemicals—more than 5,000 substances—that have been used in products such as waterproof clothing, food packaging, non-stick materials, cosmetics, industrial processes and firefighting foams. They are persistent, which is why they are often called “forever chemicals.”

Some PFAS, particularly PFOA and PFOS, have been associated with adverse health effects at sufficiently high or prolonged exposure. However, there isn't enough toxicological information for many of the thousands of PFAS compounds.

How much is getting into UK drinking water?

This is where the UK data is quite reassuring.

The Drinking Water Inspectorate (DWI) has introduced a precautionary framework:

DWI PFAS Concentration thresholds

• Tier 1 <0.01 µg/L

• Tier 2 0.01–<0.1 µg/L

• Tier 3 ≥0.1 µg/L

The DWI's guidance value for the sum of 48 named PFAS is 0.1 µg/L (100 ng/L). It isn't currently a statutory drinking-water limit in England and Wales; it is a precautionary regulatory guidance level.

In 2025, water companies carried out more than 666,000 individual PFAS analyses across England and Wales. Only two treated-water samples were reported at Tier 3. Both were from the same treatment works in England.

There is an important distinction here: PFAS are more frequently found in raw water than in water reaching consumers' taps. Water companies can use treatment, blending or alternative sources to reduce concentrations.

What about Wales?

The picture is particularly interesting in Wales.

During 2025, the DWI reports no Tier 2 or Tier 3 samples in Welsh drinking water, although PFAS were detected at lower Tier 1 concentrations. There were 49 positive samples in Wales, according to the DWI's 2025 report.

That means that, based on the latest published monitoring, PFAS in regulated Welsh public drinking water appears to be a relatively low-level issue.

There is more uncertainty around private water supplies, particularly where groundwater may be affected by historical industrial activity or other local sources.

Should you personally be concerned?

Public mains water — relatively low concern

• If you're connected to a regulated public water supply, I wouldn't regard PFAS as a reason to stop drinking tap water. The DWI says that the low concentrations detected in some untreated sources do not present an acute or immediate health impact, and water companies are required to manage identified risks.

Private water supply — more reason to investigate

• If your drinking water comes from a private borehole, well or spring, the situation is different. Localised PFAS contamination can occur, and private supplies don't have the same large-scale treatment and monitoring arrangements as public supplies. The DWI specifically recommends investigation where PFAS are detected above its guidance levels.

Long-term exposure — worth taking seriously

• PFAS aren't something I'd dismiss simply because current concentrations are generally low. They are persistent, some accumulate in the body, and scientific understanding of the thousands of individual compounds remains incomplete. That's why the DWI uses a precautionary approach and expects water companies to reduce concentrations where appropriate.

One important point

“PFAS detected” doesn't automatically mean “dangerous drinking water.”

Detection limits have become extremely sensitive. Finding a PFAS molecule at a few nanograms per litre is very different from finding concentrations approaching or exceeding the DWI's 100 ng/L guidance value.

The bigger UK environmental concern is arguably what happens in the catchment before water reaches the treatment works. PFAS can enter rivers and groundwater from industrial sites, firefighting foams, landfill, wastewater and other sources, where they can persist for very long periods.