PFAS in drinking water: what we know, and what we don't yet

PFAS stands for per- and polyfluoroalkyl substances: a family of several thousand man-made chemicals used since the 1950s in non-stick coatings, waterproof fabrics, firefighting foams, food packaging and many industrial processes. They are often called "forever chemicals" because the carbon–fluorine bond that makes them so useful also makes them extremely slow to break down in the environment, and in us.

Why they are in the news

PFAS have been found in rivers, groundwater and some public and private water supplies across the UK, usually at very low levels, with higher concentrations near airfields, fire-training grounds, landfill and certain factories. Two of the oldest and best-studied compounds, PFOS and PFOA, have been restricted internationally, but many replacements are in use and far less is known about them.

How UK regulators treat them

There is not yet a legal limit for PFAS in UK drinking water in the way there is for lead or nitrate. Instead the Drinking Water Inspectorate issues guidance to water companies that sets out tiers of action based on the concentration found, with the top tier triggered at 0.1 micrograms per litre (100 nanograms per litre) for individual PFAS. Water companies must monitor for them and act where they are found. The Private Water Supplies Regulations do not currently set a PFAS standard, so a private supply is only tested if the owner asks for it.

Regulators in the European Union and the United States have moved further and faster, and the UK position is under review. Expect it to tighten.

What the health evidence says

PFAS build up in the body over years. Studies link long-term exposure to higher cholesterol, effects on the immune system and on liver function, and, for some compounds, an increased risk of certain cancers. The levels at which these effects occur are still being worked out, which is why guidance values keep falling as the evidence improves. Nobody is suggesting a glass of water will harm you; the concern is decades of low-level intake.

What testing can and cannot tell you

• A PFAS test looks for a defined list of compounds, typically between 20 and 50 of the several thousand that exist. A result is only as broad as the list.
• The levels involved are tiny, measured in nanograms per litre, and need specialist laboratory methods and clean sampling. This is not a kitchen-tap dip test.
• A single result is a snapshot. Levels in a borehole can change with rainfall and groundwater movement.

Should you test a private supply?

It is worth considering if your source is near a current or former airfield, fire-training site, landfill, chemical works or plating works, if sewage sludge has been spread on nearby land, or if your water company has reported PFAS in the local public supply. For most rural boreholes and springs the chance of a significant result is low, but it is the one contaminant in this list that a standard test does not cover.

What can be done if PFAS are found

PFAS are not removed by boiling, softening or ordinary sediment filters. Three technologies are proven: granular activated carbon, ion-exchange resins designed for PFAS, and reverse osmosis. Each has strengths, and the right choice depends on which compounds are present, the flow needed and the rest of the water chemistry. A Pozzani engineer will design a system around the laboratory result, and a retest confirms it is working.

Where we stand

PFAS analysis is not part of our standard kits, because for most customers it would add cost without changing the answer. We can arrange it through our laboratory for supplies where there is a reason to look. If you think yours might be one, talk to us and we will tell you honestly whether a test is worth it.