Podcast. How the water we drink affects our health

She is vital. Indispensable for the regulation of the climate, for the development of life on Earth, for the maintenance of ecosystems and populations, for agriculture. It seems to be inexhaustible and yet… according to the UN, almost half of the world’s population lives in areas where water may be lacking for at least one month a year. A share that could almost double by 2050. And drinking water is seeing its quality decline all over the world, a phenomenon accentuated by climate change. How to allow everyone to drink to their thirst? What impact does water have on our health? Elements of answers in episode 3 of “The Knowledge Factory, Season 2”, a podcast from World produced in partnership with theEspace Mendès France in Poitiers.

At the microphone of journalist Joséfa Lopez, Agathe Euzen, head of the CNRS Water Unit and deputy director of the CNRS Institute of Ecology and Environment (INEE), Massamba Diouf, professor of public health, specialist in dental surgery and the impact of water on dental fluorosis in the Ferlo region, Senegal, and Jérôme Labanowski, CNRS researcher in the E-Bicom team, specialist water contaminants.

What issues are related to water?

Agatha Euzen : Water is vital. If one does not drink for three days, the question of the duration of life arises. And this is valid for all living things – humans, plants, animals. On the other hand, water is ubiquitous on Earth. The share of fresh water is minimal, but it is enough to satisfy our different needs. The questions that arise are therefore first of all that of the distribution of water, then that of the evolution of the dynamics of the populations who will take this resource. Population growth, coastal development, urban densification and climate change have an impact on the availability of the resource, but also on the anthropogenic pressures that will impact its quality. All of this makes us very vulnerable. These issues are therefore part of a global and systemic approach to the Earth and require multidisciplinary work.

Jerome Labanowski : Water is both a source of federation for people, but also a source of many conflicts. This is why taking an interest in water is tantamount to taking an interest in man.

Massamba Diouf: In Africa, as elsewhere, water is a public health priority because it has an impact on human health. It is therefore necessary to take care of its quality in order to avoid diseases.

Water is a common good. What relationship do human beings have with it?

AE : We realize the value of water when we no longer have access to it. In France, you turn on the tap, it comes, and you don’t even try to find out where it goes when it’s been soiled. On the other hand, when we turn on the tap and the water no longer comes out, or when it comes out with a particular color, we become aware of its value. The question arises differently when you have to schedule your day according to the time you hope to have water at the tap. It arises in another way when you have to spend half an hour, an hour to get to the well, to the borehole, in order to satisfy human needs and sometimes primarily the needs of animals. Knowing that it is not because we have access to water that it is necessarily of good quality.

Africa is a continent of paradoxes: it has 17 rivers, 160 lakes, many countries are bordered by seas and oceans, and yet many countries lack water. And the quality of this water can lead to illnesses.

MD : In Africa, and particularly in Senegal, water reserves are sufficient, but exploiting them requires a lot of resources. If the exploitation were done correctly, we could satisfy 75%, or even more, of the needs of the populations.

J.L. : Regarding diseases, there are diarrheal diseases related to water quality and those related to stagnant water that allows the proliferation of mosquitoes. Producing or generating good quality water is also necessary to prevent the development of pathologies such as fluorosis – a pathology that affects tooth enamel – or even bone cancer.

Drug residues in water can also have health consequences.

J.L. : Drugs, but also residues of hygiene products or cosmetic products, are found in aquatic environments since they pass through wastewater systems into rivers. The problem with these molecules is that they are active on living organisms. For example, we often talk about the feminization of fish because of the contraceptive pill. We also often find remains of paracetamol in rivers – the equivalent of a quarter tablet of paracetamol in an Olympic swimming pool. It’s a very low concentration, what we call trace, even ultra-trace, but that tells us that there is the presence of these compounds that are active from the first small grain present . Finally, all the drugs we take, all the cosmetic products we use, sooner or later, end up in this receiving environment.

In addition to human activity, many substances are present in water and have consequences for human health…

MD : Rocks release a number of minerals – such as fluoride – which will infiltrate human drinking water. And by dint of consuming it, and therefore being exposed to this fluoride, we end up having consequences on the enamel of the teeth. This is called “dental fluorosis”. The teeth will take on a reddish color. This is very common in Senegal for example. The presence of sodium from fossil rocks is also a problem. Sodium whose concentrations often greatly exceed the recommendations of the World Health Organization. Finally, in the Ferlo area [dans le nord-est du Sénégal], there is a high iron content. It is a trace element that must be present in the body but only in trace amounts. Beyond that, poisoning occurs.

Global warming also has an impact on water quality. If a river is less full, this does not mean that it will be less polluted.

J.L. : On the contrary, even, since the less water there is, the higher the concentration of pollutants. This is one of the spectra that worries us with climate change, in addition to the quantitative aspect. This change disrupts the natural cycle. Temperature increases disrupt the aquatic ecosystem. Appear microalgae, cyanobacteria, all organisms, some of which have the ability to proliferate very quickly. And the more we stress bacteria and viruses, the more virulent they become, the better they defend themselves. They then become more and more infectious.

How to get healthier water?

EA: Around the world, nearly four billion people do not have access to proper sanitation. Two billion people do not have access to water that meets regulations for human consumption. It’s gigantic and it shows the importance of infrastructures, but also their limits. You can live in a region with your feet in the water, but without infrastructure, you don’t have the availability of the resource. We are talking about water desalination, but this produces water that does not meet the tastes and the representation of the quality that we want to obtain for use. Israel has initiated the seawater desalination system and is arriving at increasingly acceptable costs. But then, you have to see how the network is deployed, how it is integrated into land use planning, how it is integrated by the different users, and for what types of uses.

Then, when we don’t have a structured treatment system, especially in rural areas, people adopt specific more or less effective practices that are sometimes based on beliefs. For example, we will put water in a place, in a canary [un récipient en terre cuite], which will preserve a certain freshness in the water, but also help it to settle. The particles will fall to the bottom and it will clearly clear the water. Others will filter it with a piece of cloth.

Are you optimistic on the issue of water in Africa?

MD: Yes, we can be. Today, 23% of the water supply in the Senegalese capital comes from Lake Guiers, about 250 kilometers from Dakar. A seawater desalination plant is being built in a district called Mamelles, to help supply the capital. At the same time, traditional devices, tested in the laboratory, have shown quite satisfactory results from the point of view of taste and from the point of view of the physico-chemical composition. If such practices are popularized, distributed at the level of the territory, the populations will be able to have access to quality water without major difficulties.

EA: However, pay attention to all the issues. It is necessary to accompany the populations and to measure the impact of this policy on their way of life, but also from an environmental point of view. Greater sedentarization, with herds, creates pressure on the resource, for example. There is a new balance to be found for ecosystems. A water policy is not just about pulling pipes.

JL: Indeed, it is really necessary to study the consequences of an action beyond its technical framework. Behind financial issues, there is a real human and cultural dimension. I am thinking in particular of the change in the quality of the water that we are going to distribute to people who have never drunk this type of water, who have always lived in a highly parasitic environment, at risk, and who could lose their natural immunity. . Taking all the parameters into account is both strategic and political.

Also listen “The Knowledge Factory” is anchored on the African continent for its second season

“The Knowledge Factory” is a podcast written and hosted by Joséfa Lopez for The world. Directed by: Eyeshot. Graphic identity: Mélina Zerbib. Partnership: Sonia Jouneau, Victoire Bounine. Partner: Espace Mendès-France in Poitiers.

Josefa Lopez and Caroline Andrieu