Why no pesticides are detectable in Piz Sardona

Over the past few months there has been a lot of reporting on pesticide residues in Swiss mineral water springs. We at Mineralquellen Mels AG are writing this article because something fundamental is getting lost in the discussion about ‘clean alternatives’. Whether a mineral water contains pesticides does not depend primarily on how deep the spring lies or how old the water is. It depends on what happens on the soil the rainwater seeps through. Where there are arable fields, vegetable and fruit crops and vineyards, plant protection products are applied; these crops account for the largest share of the quantity used (Agroscope↗ (new tab)). Where there are none, the most important source of input is absent.

The water of Piz Sardona seeps into the ground in the high Alps above 2,000 m above sea level, by the UNESCO World Heritage Tectonic Arena Sardona. In the infiltration area there are no arable fields, no vegetable or fruit crops and no vineyards. That is the whole difference.

What the debate of recent years shows

The reporting on residues of plant protection products in Swiss water has shaken the industry. Media reports and investigations by cantonal chemists made it clear that springs in intensively used regions, too, are not automatically protected against influences from the surface. Because a natural mineral water may not be freed of residues, springs in such regions come up against natural limits.

Chlorothalonil is a fungicide that was widely used in Switzerland from the 1970s onwards, on cereals, potatoes, vegetables and vines, among other crops. Since 1 January 2020 it may no longer be used (Eawag↗ (new tab)). Its breakdown products are persistent and continue to seep into groundwater for years. The ban applies in the field immediately; in groundwater, the values are falling only slowly: between 2020 and 2025 the share of monitoring sites with more than 0.1 micrograms per litre fell from around a third to just under a quarter (FOEN↗ (new tab)).

The hydrogeological reality shows that if the catchment area of a spring lies in an intensively used agricultural zone, that use helps determine what arrives in the water. Pollutants that seeped into the soil decades ago migrate slowly through the layers. For spring operators in such regions this is an enormous challenge, because the location of a catchment area cannot be changed after the fact.

Where the pesticides come from: the infiltration area is decisive

Mineral water begins as rain. The rain falls on an area — the catchment or infiltration area — then seeps through soil and rock and re-emerges years later as a spring. On its way down, the water can carry with it what is applied to this area: nitrate from slurry, herbicides from the maize field, fungicides from the vineyard.

That is why the location of the infiltration area matters more than any figure on the label:

• Swiss Plateau: in Switzerland, arable farming is concentrated at low altitudes; in 2024, 95 per cent of open arable land lay in the valley and hill zones (Agristat↗ (new tab)). It is also on the Swiss Plateau, which is used intensively for agriculture, that the breakdown products of chlorothalonil are most widespread in groundwater (FOEN↗ (new tab)). In early 2020 the magazine K-Tipp found breakdown products of chlorothalonil in the tap water of 13 out of 30 households in German-speaking Switzerland (K-Tipp↗ (new tab)).
• Depth offers only limited protection: a deep tapping or a long journey through the rock delays the problem; it does not eliminate it. What seeps in at the top arrives at the bottom — only later. A water in which nothing is detectable today can contain today’s residues in ten years’ time if there are arable fields, vegetable or fruit crops or vineyards in its catchment area.
• High Alps above the tree line: here there are no arable fields, no vegetable or fruit crops and no vineyards; instead there are alpine pastures, scree and rock. According to Eawag, the water research institute of the ETH Domain, groundwater with a catchment area at higher altitude and without arable farming is probably not contaminated with the breakdown products of chlorothalonil, or only slightly so (Eawag↗ (new tab)). In an evaluation of the National Groundwater Monitoring, almost no residues of plant protection products were found at monitoring sites in the Alps and Prealps whose surroundings consist of summer pastures and unproductive land (FOEN↗ (new tab)). This is not a marketing claim; it is hydrogeology.

Why we don’t say ‘pesticide-free’

Since the reports on contaminated springs, many people have been wondering whether their mineral water is ‘pesticide-free’. We deliberately say ‘not detectable’. There are three things you should know about this:

• A negative test is a snapshot. It tells you what is in the bottle today. It tells you nothing about what is seeping into the ground in the catchment area and will only arrive years from now. This applies in particular to springs whose catchment area borders on arable land.
• ‘Pesticide-free’ does not mean free of pollutants. In a 2024 test of ten mineral waters by RTS and the SRF programme ‘Kassensturz’, two laboratories found traces of unwanted substances in four products: breakdown products of pesticides in one, microplastics or the PFAS substance PFBA in the others. The laboratory did not classify any of the values as acutely dangerous (SRF↗ (new tab)). Anyone who tests only for chlorothalonil sees only chlorothalonil.
• The difference between a guide value and original purity: there is no legal maximum level for pesticides in mineral water. As an indicator of purity, the Federal Food Safety and Veterinary Office (FSVO) cites a guide value of 0.1 micrograms per litre for the sum of pesticides. The law, however, requires more: a natural mineral water must be of original purity. Trace substances of human origin, such as pesticides and their breakdown products, must not occur in it at all, nor may they be filtered out (FSVO↗ (new tab)). That is the obligation of every bottler. For us, this purity begins with the infiltration area.

A laboratory can show that the substances it looked for are below the limit of detection of its method. No analysis can prove that a substance is not present in any amount. That is why we stick to what we can back up: not detectable, according to a laboratory report that states the laboratory, date, scope of testing and limit of detection. These four details make a finding comparable, and they are worth asking for with any mineral water. What ‘not detectable’ means exactly is explained in the article on PFAS in water.

In our view, anyone who uses purity in their advertising should show where their water seeps into the ground — and be able to produce the laboratory report to go with it. We do both.

What applies to Piz Sardona

The reason no pesticides are detectable in Piz Sardona is so simple that it sounds almost banal: in the infiltration area there are no arable fields, no vegetable or fruit crops and no vineyards.

Rain and snowmelt seep into the ground in the Sardona Alps above 2,000 m above sea level, by the UNESCO World Heritage Tectonic Arena Sardona, in high-alpine terrain far above the arable farming areas. The water then travels through layers of rock and stone for around twelve years until it is tapped from the Castels spring in Mels. The whole journey is shown on the Origin page.

For Piz Sardona, the finding is: not detectable. On request, we will gladly send the full laboratory report, which states the laboratory, date, scope of testing and limit of detection; a message via the contact form is all it takes.

For a natural mineral water, this finding is not a distinction but the requirement for the entire category. What sets Piz Sardona apart is the cause: for a water whose infiltration area has no arable fields, no vegetable or fruit crops and no vineyards, ‘not detectable’ is rooted in where the water comes from.

Added to this is what distinguishes Piz Sardona in any case: a naturally alkaline pH of 8.0 and a balanced mineralisation from the Alpine rock. Like every natural mineral water, it is bottled directly at the spring, in Mels, in the canton of St. Gallen. More on this in Piz Sardona: the mountain behind the water.

What we do not promise

The high mountains are not untouched either. Livestock graze on alpine pastures in summer, and targeted treatments against individual problem plants are permitted there (Direct Payments Ordinance↗ (new tab)). Every analysis is also a snapshot. We therefore do not promise that nothing will ever be found. We promise to keep having the water tested and to send the latest laboratory report on request.

Conclusion: don’t ask about the filter. Ask about the field.

Quality begins at the origin. The discussions of recent years show that the location of the catchment area is the decisive factor in how pure a water remains in the long term. No filter technology can change the origin of a water after the fact, and filtering out residues is not permitted for a natural mineral water in any case. Anyone looking for a natural product that is as untouched as possible in the long term must therefore look away from the shelves and towards the origin of the springs.

If you are switching to a different mineral water, ask just one question: where does this water seep into the ground? If the answer is ‘in the high Alps, above 2,000 metres, without arable fields, vegetable or fruit crops and without vineyards’, the origin speaks for itself. Even so, with Piz Sardona you also get the laboratory report on request.

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