Glyphosate causing neurodegenerative diseases? These links which remain to be demonstrated – L’Express

The fate of this herbicide should have been decided by a vote of the 27 member states, Friday October 13, on the extension of its authorization in the European Union. The qualified majority required to validate or reject the text was, however, not reached and a new vote will take place in mid-November. This deadline was nevertheless, once again, an opportunity to see its detractors, worried about its health risks, and its defenders, who denounce the economic consequences of its withdrawal and the lack of scientific certainty on its dangerousness. The column highlighting the links between glyphosate and neurodegenerative diseases is of course part of this context.

This statement, however, turns out to be surprising. One of the most comprehensive sources on the issue, the 1,000-page collective analysis “Pesticides and effects on health”, published by Inserm in 2021, does not in fact mention a link between glyphosate and Parkinson’s or Alzheimer’s. Alexis Elbaz, a researcher at Inserm who contributed to the chapter on disease in this report, is more reserved about this relationship, but believes that the forum raises good questions. “In neurodegenerative diseases, we distinguish Parkinson’s, Alzheimer’s and Charcot’s disease,” he recalls. Of these three pathologies, the best studied in relation to links with pesticides is Parkinson’s. A large number of studies show that it There is a link between the risk of Parkinson’s and the use of pesticides, which has led to it being considered an occupational disease among farmers in France, from 2012.

Studies have also been carried out on populations living near agricultural operations, particularly in California, where all use of pesticides has been declared since the 1970s, which has made it possible to obtain very precise databases. According to this work, people living near treated fields see their risk of developing Parkinson’s increase. “In France, work has shown that residents of the most agricultural regions also have a higher risk,” adds the expert. But these observations apply to all pesticides combined. “Knowing precisely which ones are affected is much more complicated,” he says.

Parkinson’s often develops after the age of 70. That is, years, even decades, after exposure to pesticides which are no longer always used today, in particular because many of them have been banned. Second, farmers use many different pesticides over their lifetime, often simultaneously. Measuring the extent to which they were exposed to each of these pesticides is therefore complex, if not impossible. Nevertheless, scientific studies have succeeded in identifying certain products, as shown by the Inserm analysis. Data thus confirm a presumption of a strong link between the increased risk of Parkinson’s disease and the use of organochlorine insecticides (banned for more than 10 years in France), a presumption of a moderate link with the use of paraquat (banned in Europe since 2007), as well as a weak presumption with three fungicides: zineb (banned since 2001), the ziram (partially authorized) and the mancopper (forbidden).

“On the other hand, there is little work that focuses on the relationship between the use of glyphosate and Parkinson’s, and those available do not show very consistent results,” adds the expert. The authors of the column nevertheless mention “a recent study” according to which “exposure to glyphosate was associated with signs of brain damage, measured by a blood marker of brain damage in Parkinson’s and Alzheimer’s diseases”. However, people exposed to glyphosate may also have been exposed to other unmeasured products which could help to explain this association. Even if this work raises a doubt which it would be important to investigate using new studies, it therefore does not allow us to conclude that glyphosate is responsible for an increased risk of developing these diseases – nor that it is not.

Another astonishing assertion from the forum, “the epidemic of Parkinson’s disease” could be explained by the use of pesticides and pollutants present in our environment. “According to projections made in France, the number of patients suffering from Parkinson’s disease will increase by approximately 65% ​​between 2010 and 2030, from 155,000 to 260,000 cases in France, indicates Alexis Elbaz. “The main reason is the aging of the population. It is also possible that this increase is partly linked to lifestyle – decrease in physical activity, environmental pollution – but these are not the main causes.” Another researcher, who requested anonymity, notes for his part that the authors of the article are “respectively a clinician and a researcher in electrophysiology, without notable scientific production on the links between pesticides and neurodegenerative diseases”. Alexis Elbaz recalls that Bas Bloem is an internationally recognized researcher into Parkinson’s disease.

The forum nevertheless raises the problem of the insufficient evaluation of pesticides before their marketing, particularly concerning their neurotoxicity. “In Europe, the evaluation of pesticides is carried out by manufacturers, who must provide files and studies required by the European Food Safety Authority (Efsa), which then gives its authorization, explains Alexis Elbaz. However, and I agree with the forum on this very important point, the tests requested from manufacturers are insufficient to determine whether a product is neurotoxic or not. The doses tested are insufficient and the tests carried out are not the right ones. We therefore lack data to know whether these products are neurotoxic or not.”

The researcher also recalls that recently published studies on the links between Parkinson’s and pesticides reveal problems concerning products used in the past. In other words, links to current products will probably not be known for several years. This is why he considers it crucial to improve, today, the procedures aimed at testing the neurotoxicity of pesticides. Ideally through evaluations carried out with the participation of independent bodies.