Pollution is everywhere. In the soil, in the air and also in the water. New research work has just shown it: out of 258 rivers analyzed in a hundred countries on five continents, all showed pollution from drugs.
These are the results, published on February 14 in the journal “Proceedings of the National Academy of Sciences”, of a vast international study, directed by the University of York (United Kingdom), which reveal, among other things, that rivers in previously unstudied geographic areas – South America, South Asia and sub-Saharan Africa – are the most polluted.
The pharmaceutical footprint of 471.4 million individuals
When you take a drug for treatment, its residues end up in wastewater and all or part of it in rivers with a potentially negative impact on fish, crustaceans, flora… All the rivers analyzed represent the pharmaceutical footprint of 471.4 million people.
To make a global inventory, 61 of the most commonly used drugs (antibiotics, painkillers, anti-inflammatories, antidepressants, etc.) were searched for in 258 rivers, from large rivers such as the Amazon or the Mekong, to small streams. In France, samples were taken in the Seine, in the Saint-Martin canal, in the Ardières, in the Saint-Didier stream or that of Vernay (Rhône department). Sampling and analysis followed an identical protocol for all samples. The study began in 2018.
The socio-economic factor
Four years later, what are its results? If all the rivers are contaminated by drug residues, the researchers realized that the degree of pollution of the rivers is correlated to the socio-economic conditions of the country. The most contaminated sites are in low-income countries: people now have access to medicines, but there is no domestic wastewater treatment system. Some of these countries also concentrate drug manufacturing plants. This is the case in Pakistan, where the concentrations of medicinal substances are very high, on average 70.8 µg/L with a measured maximum of 189 µg/L.
One issue of sustainable development is access to clean water for all. An achievement in rich countries, an objective to be achieved in lower-income countries which have not (yet) implemented it.
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“Molecules can combine and create toxicity”
3 questions to… Jeanne Garric, research director emeritus at Inrae (the national research institute for agriculture, food and the environment)
How to quantify this pollution on the fauna and flora?
In the laboratory, we have been able to demonstrate the effects of a drug or a few drugs together on different species. For example, they can modify the growth and disrupt the reproduction of fish. In the field, we are rarely faced with drug pollution alone, except when leaving drug factories. In some Asian countries, such as India, the study of rivers near this type of plant, where drug concentrations are very high, has confirmed the biological effects. Antibiotics target bacteria in the environment, antidepressants impact certain molluscs, and algal communities are disrupted by other drugs. That said, substances from veterinary medicine are often overlooked. Some animals receive a lot of drugs, which are released into the environment without going through the treatment plant.
Are drugs the main cause of water pollution?
No, far from it because the concentrations and effects of pharmaceutical substances on the environment are not the most worrying. There are much more toxic pollutions. Our main concern is pesticides, which are more active and more dangerous, but also biocides, disinfectants, present in certain household and industrial waste. Fertilizers lead to eutrophication (multiplication of algae). There are also concerns about metal discharges into rivers. The difficulty is to identify the mechanisms by which all these pollutants act on biodiversity. Alone, a molecule may seem harmless, but the reality is more subtle. The effects can add up, causing toxicity. For example, the beta-blockers used in cardiology all act on the same type of receptor, so that when there are several beta-blockers in the water, their effects are added. An animal that has a similar receptor on its cells will experience an effect from the addition of these pollutants. In other cases, there is a synergy: an innocuous molecule can make the membrane of a cell more permeable, allowing the entry into the cell of another pollutant present in the water…
What about water regulations?
In Europe, there is a framework directive which sets the concentrations not to be exceeded for certain substances. Some drugs are monitored, but not all because, given their effects and their concentrations in the media, they are not individually dangerous substances. However, we must be concerned about the phenomenon of antibiotic resistance: antibiotics released into nature will select resistant bacteria. Imagine that resistance genes appear in Africa because of antibiotics in the water and a lack of wastewater treatment, there is no reason for them not to reach Europe. This is why the issue of water pollution cannot be limited to a local phenomenon. This study makes it possible to recall the notion of “planetary limit”: how long can we continue to live like this and throw all these pollutants into the water? I also plead for the establishment of an IPCC on pollution, like that on the climate.
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