A recent report published by the EFSA (European Food Safety Authority) confirms the role of insecticides from the neonicotinoid family in the decline of the bee population. This negative impact is caused by the high toxicity of these synthetic molecules derived from nicotine on the nervous system of these insects. What affects bees also affects plants, soils, water, and finally, people. INSERM report details pesticide-induced diseases in men
Although nicotine is best known as the molecule responsible for the strong dependence of smokers on cigarettes, it must be remembered that this substance is basically a powerful insecticide produced by the tobacco plant as a means of defense. Plants cannot flee their aggressors and have therefore had to develop during their evolution a very sophisticated biochemical arsenal, capable of neutralizing predators that threaten their survival.
The mechanism used is very complex: when an insect (a caterpillar, for example) tries to feed on the leaves of the tobacco plant, it detects the presence of certain amino acids in the saliva of the insect. and responds immediately, in just a few minutes, by producing large amounts of nicotine in its leaves (a single leaf can then contain the equivalent of a hundred cigarettes in nicotine). Nicotine is excessively toxic for the insect, because the chemical structure of this molecule is similar to that of the neurotransmitter acetylcholine and therefore causes excessive stimulation of the nervous circuits which leads to paralysis and death of the aggressor insect.
Neonicotinoid pesticides: water-soluble neurotoxins
These insecticidal properties of nicotine were known for a long time by the Amerindians who used it, in the form of a tobacco infusion, to protect their crops from insect pests. However, nicotine is far too toxic for humans to be used on a large scale in agriculture, which motivated the discovery of derivatives of this molecule which possessed a strong insecticidal activity, while being less toxic for animals. Synthetic neonicotinoids are the result of these efforts, and this family of neurotoxins chemically similar to nicotine have become, since the 1990s, the most widely used insecticides worldwide.
Neonicotinoids are often used preventively, for example to coat the seeds of large-scale crops, such as corn and soy, and thus protect them from insects during their growth. Unfortunately, these insecticides are very stable and can end up in the pollen of treated plants and be taken up by bees living near the fields. In addition, neonicotinoids are water soluble and therefore can spread into the environment where they are taken up by other plants which are also foraged by bees.
No doubt: neonicotinoids are decimating bees
A large number of studies suggest that this contamination of pollen by neonicotinoids is very harmful to the functioning and survival of bees. For example, studies show that not only do neonicotinoid insecticides cause disorientation problems in forager bees that prevent them from returning to their hive, but they also limit the growth of hives and the development of new queens, with disastrous consequences. for the survival of the colony (only the queens survive the winter). This observation therefore suggests that these insecticides could play a leading role in the decrease in bee populations observed since the beginning of the millennium, a very worrying phenomenon since approximately 80% of commercially exploited plants in the world need pollinators to to reproduce.
An analysis of all the scientific data accumulated on this subject recently published by the European Food Safety Agency confirms that the three main neonicotinoids used in agriculture, namely clothianidin, imidacloprid and thiamethoxam, are indeed toxic to bees. A meta-analysis has also recently shown that neonicotinoids do not significantly increase crop yields. In the European Union, these insecticides have already been banned for use since 2013 for crops visited by bees (maize, rapeseed and sunflower) and it is possible that this report could pave the way for a complete ban.
Pesticides don’t stop at the field. They penetrate the soil, but also (and above all) the plants, fruits and vegetables they treat. It is therefore by eating treated foods that consumers are exposed to pesticides. In June 2013, Inserm published a summary of studies based on thirty years of epidemiological and toxicological work. The report highlights about fifteen pathologies induced by pesticides and shows a strong link between exposure to pesticides and the onset of Parkinson’s disease, non-Hodgkin’s lymphoma, prostate cancer or multiple myeloma ( kind of blood cancer). Pesticides can also have other consequences on the body, such as causing male infertility, causing spontaneous abortions or serious fetal malformations.
Woodcock B et al. Country-specific effects of neonicotinoid pesticides on honey bees and wild bees. Science 2017; 356: 1393-1395.
EFSA (European Food Safety Authority). Conclusion on the peer review of the pesticide risk assessment for bees for the active substance clothianidin considering the uses asseed treatments and granules. EFSA Journal 2018; 16: 5177, 86 pp. https://doi.org/10.2903/j. efsa.2018.5177ISS.
Furlan L et al. An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 3: alternatives to systemic insecticides. About. Science. pollute. Res. Int., published online February 25, 2018.