Per and polyfluoroalkylated substances, “Pfas” for intimates, “eternal pollutants” for the general public. These chemicals, toxic and persistent, do not degrade well in the environment, and are present everywhere, from our toilet paper to the organism of a polar bear living in Greenland.
Recently, they have been detected in cardboard straws, which since the publication of a report on August 24 have gone from being a miracle solution to reducing disposable plastic to a major environmental and health hazard. Because if they have been detected there in very small doses, they accumulate in the environment as well as in organisms. Endowed with non-stick properties, resistant to high heat and waterproofing, these polluting compounds have indeed been produced and used massively since the 1950s.
Repelling water and grease, they are thus present in a multitude of consumer products, from frying pans to gore tex clothing, including fire extinguishers. And are found, at the end of the chain, in the organisms, the waters, the soils, the rain and the air of the major part of the planet, at variable rates.
As public authorities, alerted by researchers and NGOs, become aware of the problem, their presence appears more and more massive. A map of the World, and seventeen other media, attests to the contamination of much of Europe; and the data, incomplete for lack of sufficient monitoring, are certainly underestimated.
Because if scientists have been aware of the issue since the 2000s, this family of synthetic chemical compounds remains poorly understood. They would thus be between 4,000 and 12,000 to be part of it, with different levels of toxicity. The two best known, due to their persistence in the environment, are Pfoa (perfluorooctanoic acid) and Pfos (perfluorooctane sulfonate), which are subject to specific regulations.
“Pfas have in common that they contain at least one carbon atom on which two or three fluorine atoms are grafted,” explains CNRS environmental chemist Pierre Labadie. This single bond is the strongest in organic chemistry. The graft with fluorine reinforces the carbon-carbon bonds of the carbon chain, and these two components will confer a very strong chemical and thermal stability, an undeniable advantage for the industry, but a problem for the environment, because they are not do not degrade there. Once introduced, they stay there and accumulate. »
The problem ? In addition to permanently contaminating ecosystems, Pfas would be responsible – studies, like legislation, are still fragmentary – of cancers, cardiovascular problems, increased cholesterol levels, acting as endocrine disruptors, and decreased fertility and immune response to vaccines.
According to Le Monde, nearly 17,000 sites in Europe are contaminated. Pfoa and Pfos, the largest contributors to impregnation levels, were quantified in France at 100% in both children and adults, according to a study published in 2019 by Public Health France.
“For Pfos, for example, an emblematic compound of the family, there are no known degradation mechanisms in the environment, develops Pierre Labadie. In any case, it takes more than decades. It must be said that the half-life time, necessary to eliminate half of a dose of Pfas ingested today, can be several years, in the environment as in the human body. »
If depollution processes exist, at a minimum, they are “unrealistic” on a large scale, due to their cost and the quantity of Pfas already present in the environment. Molecule washing and immobilization processes can nevertheless be considered to decontaminate some of the most affected “hotspots”. But this remains a precarious solution.
“It amounts to leaching soil with water to displace the problem and then treating the contaminated water, or using oxidation processes on soil and groundwater, lists Pierre Labadie. But there are no low-cost processes that can be used widely. We are rather managing on a case-by-case basis and implementing these processes locally, in the face of an environmental or health issue, when a water table is affected, for example. »
Hence the importance, according to the researcher, of opting for “global regulation”, which applies to the family of chemical compounds as a whole rather than on a case-by-case basis. “Reducing at source is a key step. We should ban, or at least very strongly limit uses to the most essential, especially medical ones, ”suggests Pierre Labadie. A first proposal for a European-wide ban, brought by the European Chemicals Agency at the request of Nordic countries, and supported by France, could see the light of day in 2025.
Until then, it is also important to further develop mechanisms for monitoring Pfas pollution levels, and to protect the most exposed populations. “We must develop monitoring actions to estimate the levels to better document and inform the contamination, assesses Pierre Labadie. We have drinking water gaps, and we should study the fate and impact of these compounds once emitted, to understand what happens when they are in the environment, and to consider depollution actions by favoring the most relevant areas. »
