Water knowledge

PFAS in water: what a laboratory analysis shows — and what it does not

PFAS occupy authorities, water utilities and laboratories. The term covers a group of synthetic chemicals that barely break down and are therefore called ‘forever chemicals’. This article sets out the context: what lies behind the abbreviation, why there is regulation, how an analysis comes about — and why ‘no traces could be detected’ means something other than ‘not present’.

Updated August 2026 · 6 min read

What are PFAS?

PFAS stands for per- and polyfluoroalkyl substances. This is not a single chemical but a large group of synthetic compounds with one thing in common: a very stable bond between carbon and fluorine. That bond makes the substances technically useful. They repel water, grease and heat, and are therefore used in industry, agriculture and consumer goods.

The same stability has earned them the nickname ‘forever chemicals’. PFAS barely degrade in the environment. Whatever has once been released stays: in the air, in soils, in bodies of water. By these routes the substances also reach drinking water and accumulate there. An input does not disappear again, it only spreads.

Why PFAS are regulated

Regulation begins with precisely this persistence. A substance that does not break down and that accumulates in the environment and in organisms behaves differently from a residue that has vanished after a few weeks. Authorities therefore work on the precautionary principle and limit inputs before every individual compound has been conclusively assessed. The EU Drinking Water Directive has had combined limit values for PFAS since 2020; Switzerland has laid down maximum levels for drinking water. Natural mineral water is additionally subject to its own food-law provisions. In both cases the version currently in force applies.

Knowledge is unevenly distributed here. For individual compounds that have long been studied, extensive data exist. For many others from the same group, the data are thin. Assessments are revised on an ongoing basis, requirements are updated, testing scopes are extended. Anyone looking into PFAS today is looking into a field in motion.

How PFAS enter the water cycle

The routes of entry lie at the surface. Industrial waste water, firefighting foams, coated textiles and papers, sewage sludge on farmland: from there the substances travel into soils and waters. Some of it passes into the atmosphere and comes down again elsewhere with the precipitation. Traces can therefore be found far away from any industrial plant.

For an underground source, two things matter above all: what happens in the catchment area above it, and how long the water is under way. Water tapped today seeped into the ground years or decades ago. It carries the signature of the period in which it entered the subsurface, not that of the present. Deep, old sources therefore respond more slowly to current inputs than shallow tappings. That is no automatic rule. Geology, catchment area and measurement remain decisive.

What ‘not detectable’ means in the laboratory

Precision is worth the effort here, because everyday language cuts many corners. A laboratory never measures ‘everything’. It looks for a defined selection of compounds, with a defined method, in a specific sample. Every method has a limit of sensitivity: below it, a signal can no longer be reliably distinguished from the noise of the measurement. That is the limit of detection.

• Which compounds were looked for: the group of substances comprises a large number of individual compounds. A method always covers a selection of them, never the entire group.
• How sensitively the measurement was made: the lower the limit of detection of a method, the smaller the quantities that become visible. It is never at zero.
• Which sample was examined: a finding applies to the material that was in the laboratory, and to the moment of measurement.
• Who did the measuring: independent laboratories work to documented, repeatable methods. That makes a result verifiable.

From this follows a distinction that is easily lost. ‘No traces could be detected’ is a statement about the measurement: what was looked for lay below the limit of detection of the method. ‘Not present’ would be a statement about reality, and that is something an analysis fundamentally cannot deliver, however sensitively it measures. A negative finding is not proof of absolute absence. It shows that nothing was visible below a certain threshold.

That is why this text keeps to the laboratory’s wording throughout: no traces could be detected. The absolute shorthand would be catchier and factually wrong. We do not use it.

What is on record for Piz Sardona

For Piz Sardona, a statement from the producer is available. Mineralquellen Mels AG reports that it had its mineral water tested for PFAS by an independent laboratory in Germany; the laboratory confirmed in writing that no traces of PFAS could be detected. On the scope of testing, the method and the limit of detection, no public information is available.

The finding should be read with corresponding restraint, in exactly the way the section above describes: what was examined lay, in the material tested, below the limit of detection of the method used. Such a result carries no more than that — and no less.

The company itself puts its water in these terms: ‘We have always been convinced that our Alpine mineral water is excellent in taste and in quality,’ says Malte Christian Mack, managing director of Mineralquellen Mels AG. The sentence reflects the producer’s view, not the result of a measurement.

What origin can contribute — and what it cannot

The water of the Castels spring in Mels seeps into the ground in an area above 2,000 m above sea level, by the UNESCO World Heritage Tectonic Arena Sardona, and then travels through layers of rock and stone for around twelve years. What is bottled today therefore reached the subsurface more than a decade ago. Origin describes the path a water takes and the time it needs for it. It does not replace a measurement and says nothing in itself about what is to be found in a sample. Where that path begins is shown on the page about the Origin.

A second point belongs to this picture. That a natural mineral water comes from an underground source protected from contamination is not a distinguishing feature of a single brand, but a condition of the entire category, set down in food law — as explained in the article on spring water and mineral water. What sets an individual spring apart is stated in its analysis. That of the Castels spring can be found on the page about our water.

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