The water flowing from our taps remains extremely monitored. However, pesticide residues and a host of perennial pollutants – PFAS (1) – still go under the radar, and fuel a flood of questions about their effects on health. New example to date, trifluoroacetic acid (TFA) was found in the water of 24 French municipalities out of 30 studied, exceeding, in 20 municipalities, the future reference standard in Europe, according to a survey carried out by the ‘UFC-Que Choisir and the NGO Générations futures.
Can we hope to protect ourselves against these pollutants thanks to filters sold commercially? Concerning TFA, the answer is clear: “There is no miracle solution to offer to consumers, the filters are not effective”, underlines Pauline Cervan, toxicologist at Générations futures. TFA is, in fact, “less well retained” than other PFAS by water decontamination techniques, both those based on activated carbons and those based on membrane filtration, specifies Julie Mendret, researcher. at the University of Montpellier. The reason? TFA is a “short-chain PFAS”, which contains fewer carbon atoms and is therefore “very small, very mobile”.
Filter jugs with very variable efficiency
Concerning other PFAS and pesticides, manufacturers of jugs equipped with activated carbon filters promise to reduce “some”. Their effectiveness on PFAS was evaluated in an American study (2) published in 2020. It concluded that “73% of contaminants” were eliminated but that the results vary considerably. Some scientists confirm that the effectiveness of activated carbon filters, in general, depends on the size of these eternal pollutants: the longer their chain of atoms, the more likely they are to be trapped.
Another solution is to connect a “reverse osmosis system” to its water supply, under the sink. The principle of this system is to pass the water through several filters, then, under pressure, to pass it through an osmotic membrane in order to eliminate impurities. The American scientific study, cited above, estimated that this type of filtering makes it possible to reduce PFAS levels, “by 94% or more in water”. Reverse osmosis units are nevertheless criticized by the fact that several liters of water are required to produce just one. Its initial cost of several hundred euros and that of consumables is also a hindrance.
-1. Pronounce it “Pifasse”. These are substances present in pesticides, refrigerant gases, non-stick pan coatings, fire-fighting foams or cosmetics, and particularly in the waste from the factories that produce them.
2. From Duke University and North Carolina State University.
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