According to Henri Klunge, newly elected deputy in the canton of Vaud and founder of Alcane Conseils, "the presence of this small molecule in the drinking water should remind us that our activities are not without consequences nor without risks for the environment."
1,2,4-triazole is a small cyclic molecule containing three nitrogen atoms, mainly used in the manufacture of certain medicines and pesticides. It can also result from the degradation of another product. It is then referred to as a metabolite, as in the case of chlorothalonil.
Recently detected in the drinking water of Lake Leman at concentrations exceeding legal limits, this substance raises legitimate questions. To date, however, available studies indicate that 1,2,4-triazole does not present acute toxicity at the concentrations currently measured, roughly 0.7 µg/L.
As with many chemical compounds, prolonged exposure to much higher doses could nonetheless lead to adverse effects. That is why Swiss authorities have applied the precautionary principle by setting a very strict limit of 0.1 µg/L, well below the thresholds at which health effects might be observed. This limit aims to ensure impeccable water quality for the entire population.
Several technical solutions can remove 1,2,4-triazole from water. Activated carbon, which acts like a sponge by capturing unwanted molecules, can remove part of it. Its effectiveness, however, depends on many factors, making this solution unreliable in the present case.
Reverse osmosis, a very fine filtration technique based on the use of membranes, allows for more complete removal. Its cost and complexity, however, limit its use on a large scale.
Another method, advanced oxidation, combines ultraviolet light and hydrogen peroxide to chemically break down the compound. This approach, however, requires particular expertise to avoid the formation of new pollutants.
Finally, biodegradation, which relies on the use of microorganisms to degrade the substance, remains difficult to implement for this particularly resistant compound, even more so on such a large scale.
We must indeed avoid at all costs a "cocktail effect", where the accumulation of multiple substances, even at low doses, could become problematic in the long term.
While these treatment techniques are useful, the most sustainable solution is to prevent 1,2,4-triazole from ending up in the water. In my view, companies must take responsibility and do everything possible to reduce discharges of such substances into the environment. They should notably treat their effluents to prevent these compounds from ending up in the water, even when they comply with the already strict limits set by the Swiss Confederation.
We must indeed avoid at all costs a "cocktail effect", where the accumulation of multiple substances, even at low doses, could become problematic in the long term. This notably involves improving industrial processes to limit discharges, but also implementing systems to recover residues before they leave factories.
When a substance like 1,2,4-triazole becomes problematic, the temptation is great to replace it with another. Yet history has taught us that some substitutions can prove worse than the original problem. Before replacing a compound, it is therefore essential to rigorously evaluate the available alternatives, studying their potential effects on health and the environment. This cautious approach helps avoid what specialists call "regrettable substitution".
The toxicity of a new substance may indeed only be discovered years later, the "substitute" often initially slipping under the radar. The risk is then to release into the environment a potentially problematic product for decades, without it being known. This is partly what we are observing today with substances whose presence or effects are raising new concerns, such as 1,2,4-triazole and chlorothalonil.
The presence of 1,2,4-triazole in our water currently reminds us that our activities are not without consequences or risks. We must use chemistry sparingly, remain aware of its potential long-term effects, and take responsibility for our products downstream of our activities. To achieve this, collaboration between various private and public actors is essential to preserve water quality and protect public health.
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