After the findings were made public, the cantons of Geneva, Vaud and Valais concluded that the triazole measured in Lake Geneva poses no health risk. This was reported by Blick Romandie, among others, citing a toxicological assessment by the Swiss Centre for Applied Human Toxicology (SCAHT).

The concentrations in drinking water – around 0.7 micrograms per litre – are more than 400 times below the level at which health effects can no longer be ruled out.

In other words: ‘An adult would have to drink more than 900 litres of water a day to reach the theoretical threshold at which a health effect can no longer be ruled out,’ the report states. The water from Lake Geneva can therefore be drunk without hesitation. The authorities merely recommend continuing to monitor the concentrations regularly and pushing ahead with technical improvements in water treatment.

However, unlike the French health authority ANSES, which considers 51 micrograms per litre to be safe for 1,2,4-triazole on human and ecotoxicological grounds, its Swiss counterpart, the Federal Food Safety and Veterinary Office (BLV), insists on compliance with the purely precautionary limit of 0.1 micrograms per litre.

Industry reacts quickly – but the immediate solution is not sustainable

According to analyses, the measured traces of 1,2,4-triazole also originate from the Monthey chemical site, where Syngenta also operates production facilities and uses the substance as a raw material. The company emphasises that it is taking the situation very seriously. As a short-term measure, contaminated wastewater is to be thermally treated (incinerated) until a permanent solution is implemented at the source. Several technical processes, such as activated carbon filtration and liquid-liquid extraction, are also currently being tested. This is because 1,2,4-triazole cannot currently be removed by any municipal wastewater treatment plant. However, there is a lack of transparency as to whether any values have been measured at these and other plants around Lake Geneva, and if so, what they are. There is also uncertainty about the diffuse pathways of entry, as 1,2,4-triazole is found in a wide variety of applications and is very likely to be formed in nature (see box below).

However, only by investigating these sources of pollution can the measured values in Lake Geneva be reduced. Measures taken by industry alone will not improve the situation. And they must be sustainable in the medium and long term in the broader sense, i.e. technically feasible and economically viable (as required by environmental law), ecologically sound and socially acceptable in terms of preserving jobs in the region. The immediate measures taken in response to political pressure are not sustainable – neither in terms of climate protection nor for financial reasons.

Between safety concerns and common sense

One thing is clear: the debate surrounding limits for chemical residues in water and food is often characterised by fears and emotions that are deliberately or unwittingly provoked. To strike a balance between safety concerns and practical common sense, it often helps to draw a clear comparison with more familiar situations in life, as Roman Mazzotta, Country Head of Syngenta Switzerland, does: "One of the most dangerous things you can do is drive a car. There are rules about keeping your distance. On the motorway, the distance to the next car must be 60 metres. That is the “limit value”. For chemical substances that are neither DNA-damaging nor carcinogenic, a hundredfold safety margin is applied to this limit value. Applied to car traffic, this would mean maintaining a hundredfold distance of 6 kilometres to the next car. 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."

The precautionary principle can undermine sensible action and have enormous cost implications. Precisely because analytics are making ever smaller residues visible, it is essential to classify the measurement results scientifically. Not every residue is necessarily a problem – and not every officially ordered ‘remediation’ of a drinking water catchment is financially sensible and toxicologically appropriate. This is demonstrated by this current case – as well as by the ‘chlorothalonil case’, which is still pending in court.