The poison and the dose – Great panic over small values?

The discussion about limit values for chemical residues in water and food is often characterised by misunderstandings and emotions. Hardly any other topic shows so clearly how much perception and science drift apart. But what do limit values really mean? In autumn 2025, the agricultural policy podcast and swiss-food.ch shed light on our approach to limit values in a series of podcasts.

Limit values are intended to protect society from excessive exposure to potentially toxic substances. Thanks to advances in analytics, even the smallest amounts of residues can now be detected. As a result, measured values and their significance are often interpreted differently. There is a fine line between honest information and alarmism or trivialisation.

It is the dose that makes the poison. This applies equally to natural and synthetic substances. Residues alone do not indicate a hazard. At the same time, ‘natural’ substances enjoy enormous trust – even if they are potentially toxic. A prime example of this is fungal toxins.

Roman Mazzotta, Country Head of Syngenta Switzerland, sums up how difficult it is to strike a balance between safety considerations and practical common sense in the Green Sofa Studio discussion format (Only available in German): "One of the most dangerous things you can do is drive a car. There are rules about keeping your distance. On the motorway, you have to keep a distance of 60 metres from the car in front. That's the “limit”. For chemicals that aren't DNA-damaging or carcinogenic, a hundredfold safety margin is added to this limit. Applied to road traffic, this would mean keeping a hundredfold distance of 6 kilometres from the car in front. On which motorway in Switzerland could you still drive with such distance rules? I am concerned with the same sense of proportion when it comes to limit values for water."

In five podcast episodes, experts from toxicology, industry, authorities and agriculture discussed what safety really means and what role limit values play in this. The highlight was a live podcast in front of an audience on 5 November at Bogen F in Zurich, with the participation of scienceindustries: Dominique Werner, Head of Chemicals Law. The focus was on how public perception, regulatory hurdles and scientific findings shape our approach to chemical residues in agriculture and our waters.