La saga de l’interdiction des néonicotinoïdes : pourquoi 20 ans d’attente ?


This may be the end of an interminable battle: on Friday 27 April 2018, the Member States of the European Union adopted the Commission's proposal to ban three neonicotinoids (clothianidin, imidacloprid and thiamethoxam) from all field crops. These products have been controversial since their deployment in the 1990s. Why did it take so long?

Ds early as 1994, French beekeepers reported serious disturbances affecting their colonies. These disturbances - which go as far as the more or less rapid mortality of the bees - appear mainly at the beginning of the flowering of the sunflowers, which supply an abundant quantity of nectar and pollen to the insects.

After a field survey, the beekeepers found that a new insecticide was being used for the preventive treatment of this crop: imidacloprid, a member of the neonicotinoid family. These neurotoxic insecticides act in particular on the central nervous system of insects.

Called Gaucho in its commercial formulation, it is produced by the German chemical company Bayer. It is applied according to a special method of administration: the insecticide is not sprayed on the plants, but coats the sunflower seeds from which it moves throughout the plant.

A trio of volunteer researchers

Having found no real help from the public authorities who authorised the use of this substance, beekeepers then turned to scientists who could provide proof of the toxicity - or not - of this substance.

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But few researchers get involved, no doubt sensing that the task would be fraught with pitfalls; not so much for scientific reasons, but rather because of the actors involved: the State, and especially the Ministry of Agriculture; the farming community, and especially the advocates of intensive agriculture; and finally, Bayer, which sells the insecticide.

Only three researchers agreed to embark on this "adventure"; their names deserve to be remembered as this (too) long story comes to an end: Jean-Marc Bonmatin (chemist at the CNRS), Luc Belzunces, (toxicologist at the INRA) and Marc Colin (pathologist at the Afssa, the current Anses).

Their first results, first published in research reports for the Ministry of Agriculture and then in scientific journals (e.g. in 2000, 2003 and 2004), show that bees are exposed to imidacloprid through nectar and pollen: the molecule is highly toxic to bees, even at low concentrations. In particular, it causes neurobehavioural disturbances that may explain the origin of the disturbances and deaths observed by beekeepers.

Virulent controversy

Denying the involvement of imidacloprid in bee deaths, some people claim - without any scientific demonstration - that these disorders are a "French disease": beekeepers do not take good care of their colonies and these would be victims of the "black disease" which causes chronic paralysis of viral origin.

But how do you explain that suddenly, at the time of the sunflower honeyflow, beekeepers stopped taking care of their colonies properly? And why, for some obscure reason, would the then healthy colonies be affected by black disease as soon as they came across sunflowers treated with a highly toxic insecticide? In previous years, the same untreated sunflowers did not cause any disease...

A lively controversy then began, which is described in detail in an report of the European Environment Agency published in 2013.

Video on the decline of bees (Le Monde/YouTube, 2015).

A final and unappealable challenge

In 2003, nine years after the first reports, the Minister of Agriculture, Jean Glavany, decided to create a group of about twenty experts, the Scientific and Technical Committee for the Multifactorial Study of Bee Disorders (CST), of which I was a member. This committee met for two years and published the following documents his final report on the Gaucho in 2003.

His conclusion is crystal clear:

"In the current state of our knowledge, based on the scenarios developed to assess exposure and the uncertainty factors chosen to assess hazards, the PEC/PNEC ("predictive environmental concentration"/"predictive no effect concentration") ratios obtained are of concern. They are in agreement with the field observations reported by many beekeepers in arable farming areas (maize, sunflower), concerning the mortality of foragers, their disappearance, behavioural problems and certain winter deaths. Consequently, the coating of sunflower and maize seeds with Gaucho leads to a significant risk for bees. »

This report will have an important impact: for the first time, the toxicity of imidacloprid to bees is recognised. Its conclusions will lead the Minister of Agriculture to suspend the use of Gaucho on two crops that are highly visited by bees, sunflower and corn.

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In comparison with previously published expert reports on the toxicity of pesticides for bees, the CST report was innovative, as the working group conducted a critical analysis of the studies submitted by Bayer and public researchers (mainly INRA and CNRS), as well as published scientific articles on the subject. Some 340 documents were analysed in detail.

The originality of this analysis was to introduce criteria for the quality of the studies, which had not previously been done either in France or at the European level. These criteria aimed, for example, to ensure that the samples were in sufficient number and representative of natural conditions, that control batches (untreated) were present, etc. The aim was to ensure the quality of the studies, which had not previously been carried out in France or at the European level.

The application of these criteria led to the rejection of a large number of studies of insufficient scientific quality that had been taken into account for the registration of Gaucho.

It should be remembered here that this in-depth analysis was made possible thanks to significant human resources (two full-time post-doctoral students for two years), the experts of the working groups rarely having the time to analyse in depth and critically the very numerous studies submitted... Support largely provided by the beekeeping sector, which agreed to use European money dedicated to supporting beekeeping for this purpose.

The issue of evaluations

In 2011, the European Commission request to the European Food Safety Authority (EFSA) to assess, prior to any placing on the market, the evaluation quality on the risks that pesticides pose to bees; in particular, to assess the environmental assessment system based on the recommendations of the International Commission for Plant-Bee Relationships (ICPBR), an organization close to the phytosanitary companies.

Following this request, an EFSA working group will then draft in 2012 an science advice noting that the toxicity of pesticides placed on the market has not been properly assessed; indeed, several key aspects have not been taken into account: toxicity on larvae, long-term effects on colonies, chronic toxicity on adults, sublethal toxicity (the fact that bees can become disoriented after exposure to an insecticide, not returning to their hive and dying quickly).

The experts also show that the field trials follow a single, very unprotective guideline established by the ICPBR. As a result, bee exposures to systemic seed coatings, such as neonicotinoids, were not really considered.

Since the late 1990s, the effects of these products on bees have not been properly assessed before they are placed on the market. And while EFSA has proposed in 2013 a new guide for the assessment of these risks for domestic and wild beesThis document is still not fully followed up by risk assessment bodies in the European Union.

Information still missing

In 2013, EFSA is assessing the risks associated with the use of three neonicotinoids: clothianidin, imidacloprid and thiamethoxam, used for the seed treatments.

Based on the arguments of the 2012 Scientific Opinion and data from the scientific literature, EFSA identifies a number of acute risks associated with the use of these products. However, some assessments could not yet be finalised due to incomplete data provided by the companies.

It is particularly striking that, 20 years after the placing on the market of imidacloprid and related compounds, certain data have still not been provided by the plant protection companies in order to finalise the evaluation of their toxicity; and that, despite this absence, these substances have been authorised.

As a result of this new evaluation, the European Commission has therefore decided to propose to EU Member States to suspend the authorisation of these three neonicotinoid insecticides, except for crops not attractive to bees and winter cereals. These three substances are therefore still widely used in the environment.

In February 2018, 17 years after the CST report and 24 years after the first alerts, EFSA finally publishes a new evaluation which shows that most uses of neonicotinoid pesticides pose a risk to wild and domestic bees.

The least we can say is that this process has taken far too long: before authorizing the marketing of a pesticide, it is absolutely necessary to ensure that it is safe for wildlife and human health!

What about other species?

We have considered here the case of bees, but many other species have most probably been affected, and have been for a long time, by these substances.

(see in this respect various review articles published in 2014, 2015 and 2017).

But let us end on a hopeful note: in January 2018, the European Parliament decided to set up a special committee to investigate the How pesticides are authorised in Europe.

It is to be hoped that parliamentarians will henceforth analyse very rigorously all the causes that led to the placing on the market of substances whose toxicity had not been sufficiently assessed for the environment, and which it was so difficult and time-consuming to ban. And that they will propose new procedures for the registration of these products, based on the best established scientific knowledge and the absence of conflicts of interest of the experts and institutions in charge of these assessments.

Gérard ArnoldEmeritus research director, apidologist, National Centre for Scientific Research (CNRS)

The original text of this article was published on The Conversationa UP' editorial partner.

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