A study carried out by the French National Institute for Agricultural Research (INRAE) into micropollutants at the exit of wastewater treatment plants has concluded that, despite a lack of comprehensive data, their impact on the environment remains undeniable. EURACTIV France reports.
It is a challenge for treatment plants to deal with substances in wastewater, which includes pesticides, hydrocarbons, drug residues, and hormones. Due to their low concentration in water – micro or nano-grammes per litre of water – these molecules, known as “micro-pollutants”, are emitted by human activities that inevitably end up in our waterways.
According to INRAE’s study published in the journal Water Research on Monday (30 November), the minuscule concentrations of these molecules have “significant potential impacts” on aquatic ecosystems and human health.
However, the study only analysed one-third of the 286 micropollutants identified among those prioritised by the EU and those resulting from scientific studies.
“The lack of raw data and information on the effects of these substances on the aquatic environment forced us to focus on 88 molecules,” Dominique Patureau, a researcher at the environmental biotechnology laboratory at INRAE, told EURACTIV France.
Still, the study found these micropollutants had a significant effect, particularly with regard to the environmental footprint of these micropollutants which, according to the researchers, are potentially responsible for the disappearance of one aquatic species every ten years.
Among those responsible are pesticides, such as cypermethrin, a molecule present in insecticides, hormones, such as oestrogen, as well as the very widespread antibiotic “amoxicillin”.
“All these molecules are found in our waterways as a result of human activities,” said Patureau.
“Pesticides of course come from agricultural land, via the application of phytosanitary products. Hormones and drug residues come for the most part directly from what we humans – but also farm animals and even pets – consume,” the researcher added.
Simply put, we do not metabolise all the substances we ingest, a large part of which usually ends up in wastewater.
Molecules that ‘should never have been put on the market’
While some substances degrade quite well, such as the hormone estradiol, others, such as polychlorinated biphenyls (PCBs), continue to contaminate ecosystems, sometimes even after several decades.
Although PCBs are classified as toxic and carcinogenic and have been banned in France since 1987, they were found in the effluents of wastewater treatment plants.
“They are persistent substances that degrade very poorly. They should never have been put on the market,” said the scientist.
Yet, while the effects of micropollutants on aquatic environments are undeniable, those on human health are less obvious. According to the study, the potential impact on human health remains relatively low.
“After all, we are not constantly immersed in waterways like other species. Nor do we drink the water as it comes out of the sewage treatment plants,” the study writes.
However, INRAE’s researchers remain cautious, pointing again to the serious lack of data regarding the link between micropollutants released into our rivers and human health.
France is already working to reduce the pollution of its waterways. Not only has the use of phytosanitary products been banned in all public spaces since 2017, but the government has also committed to a 50% reduction in the use of plant protection products by 2025 as part of its new Ecophyto II+ plan.
Cleaning this up also comes at a price. According to the environment ministry’s micropollutant plan for 2016-2021, the cost of eliminating one kilogramme of pesticides in water to produce a drinking resource is estimated at between €60,000 and €200,000.
[Edited by Zoran Radosavljevic/ Natasha Foote]