Insecticiden

This chapter provides insights into the difficulties and challenges of performing risk evaluations of agrochemicals. It is a critical review of the current methodologies used in ecological risk assessment of these chemicals, not their risks to humans. After an introduction to the topic, the current framework for ecological risk assessment is outlined. Two types of assessments are typically carried out depending on the purpose: i) regulatory assessments for registration of a chemical product; and ii) ecological assessments, for the protection of both terrestrial and aquatic ecosystems, which are usually site-specific. Although the general framework is well established, the methodologies used in each of the steps of the assessment are fraught with a number of shortcomings. Notwithstanding the subjectivity implicit in the evaluation of risks, there is scepticism in scientific circles about the appropriateness of the current methodologies because, after so many years of evaluations, we are still incapable of foreseeing the negative consequences that some agrochemicals have in the environment. A critical appraisal of such methodologies is imperative if we are to improve the current assessment process and fix the problems we face today.

On Tuesday 21 July Christian Schmidt, Germany’s Federal Minister of Agriculture, signed an urgency decree coming into immediate effect forbidding all trade, import and sowing of winterwheat seed-coated with the nicotinoids Clothianidin, Imidacloprid und Thiamethoxam. Minister Schmidt argumented the decision as necessary to prevent massive death of honey bees saying that “ with this decision honey bees will be protected from dust contaminated with insecticides. This serves the bees as an important part of nature as well as the farmers who are dependent on bees for the pollinisation of their plants.” The attached article by Klaus Wenzel, published in the Journal Entomologische Zeitschrift Heft 2-2015 in May, has been instrumental in bringing the German authorities to this decision.

New findings published in the journal Environmental Science & Technology investigate the use of insecticides--specifically neonicotinoids--and their effects on the decline of the honey bee population. Although sunlight plays an important role in degrading pollutants, its effects on neonicotinoids may diminish, particularly when exposed to water. In order to protect crops from pests, including whiteflies, beetles and termites, neonicotinoids are often used as a popular protection tool among farmers. However, they end up washing into the surface waters and soil. For the study, researchers looked to investigate the sunlight's effects on these insecticides in the water. They tested five neonicotinoids in water under simulated sunny conditions and within minutes, three degraded considerably, according to researchers. And while two took a few days to break down, a depth of just 3 inches of water was enough to shield at least one, thiamethoxam, from the sun. The researchers noted that at a persistent rate with shallow depth, this could increase insecticide exposure to both aquatic life and other wildlife exposure.

More than 70% of pollen and honey samples collected from foraging bees in Massachusetts contain at least one neonicotinoid, a class of pesticide that has been implicated in Colony Collapse Disorder (CCD), in which adult bees abandon their hives during winter, according to a new study from Harvard T.H. Chan School of Public Health. The study will be published online July 23, 2015 in the Journal of Environmental Chemistry. "Data from this study clearly demonstrated the ubiquity of neonicotinoids in pollen and honey samples that bees are exposed to during the seasons when they are actively foraging across Massachusetts. Levels of neonicotinoids that we found in this study fall into ranges that could lead to detrimental health effects in bees, including CCD," said Chensheng (Alex) Lu, associate professor of environmental exposure biology in the Department of Environmental Health at Harvard Chan School and lead author of the study.

Der BUND begrüßt das neue Verbot der Neonikotinoide Clothianidin, Thiamethoxam und Imidacloprid zur Saatgutbeizung für Wintergetreide. Bundeslandwirtschaftsminister Christian Schmidt hatte per Eilverordnung ein „vollständiges Verbot der Einfuhr und des Inverkehrbringens“ dieser drei Pestizidwirkstoffe angeordnet. Der BUND-Pestizidexperte Tomas Brückmann sagte zu der Entscheidung: „Neonikotinoide tragen maßgeblich zum weltweiten Bienenvölkersterben bei. Das gesetzliche Verbot zur Beizung von Wintergetreide kann nur ein Schritt auf dem Weg dazu sein, alle Neonikotinoide vom Markt zu nehmen. Neonikotinoide stören das Immunsystem und das Lernvermögen der Bienen erheblich. EU-weit sind die drei jetzt per Eilverordnung eingeschränkten Neonikotinoide zwar seit Dezember 2013 für bienenrelevante Kulturen verboten. Experten kritisieren aber, dass auch die Verwendung in so genannten nicht bienenrelevanten Kulturen große Gefahren für Bienen und Umwelt verursacht. Weitere gefährliche Neonikotinoide sind außerdem noch ohne jegliche Einschränkung zugelassen. Landwirtschaftsminister Schmidt muss jetzt konsequent sein und das zuständige Bundesamt anweisen, die Zulassungen aller neonikotinoidhaltiger Produkte zurückzunehmen. Neonikotinoide sind Nervengifte, die Bienen und andere Lebewesen erheblich schädigen, sie müssen deshalb ausnahmslos verboten werden.“

Dans le texte proposé, deux éminents toxicologues, doublés d'excellents mathématiciens, Henk A. TENNEKES hollandais, et Francisco SANCHEZ-BAYO australien, ont mis en commun leur compétence pour démontrer que les "Tests Standards", aujourd'hui en usage dans le domaine des travaux préalables à l'homologation des substances chimiques -en particulier des pesticides-, ne sont pas en mesure de définir des "niveaux sûrs d'exposition", tant pour les êtres humains que pour la biodiversité. Cette incapacité relève tant des points de vue "conceptuel que statistique". S'appuyant sur les travaux, anciens certes, de Haber d'une part, et de Druckrey (pharmacologue) et Küpfmüller (mathématicien) d'autre part, mais pourtant toujours d'une évidente actualité, ils démontrent d'un côté les failles des Tests Standards, de l'autre ils démontrent qu'un test, fondé sur une base conceptuelle et une pratique différentes, le test "Time-To-Event" ou TTE, "Temps-pour-un-Evènement", permet au contraire de prévoir les effets probables, au cours du temps, des substances sur les espèces non-cibles. Ainsi s'effondre le postulat (idéologique car jamais démontré) de l'innocuité des "faibles doses". Sous certaines conditions, résultant de l'interaction entre la substance et les récepteurs de l'organisme, plus le temps d'exposition s'allonge plus la dose totale reçue diminue pour produire un même effet. La substance est ainsi plus toxique à faible dose qu’à forte dose, le temps jouant ainsi un rôle majeur dans l’expression de la toxicité. Ce démenti scientifique formel, infligé au postulat "d'un seuil d'innocuité" des faibles doses, ouvrira-t-il les yeux des différentes Agences gouvernementales ? Si l’on souhaite assurer la sécurité des humains et l’avenir de la biodiversité il y a urgence !

We have identified 30 papers from a literature search on PubMed and Google Scholar using the following combined key words of “pollinators”, “honeybee”, “bees”, “pesticides”, or “neonicotinoids”, as of September 30, 2014, and from a cross-reference check of a report made available by European Parliament in preparation to fulfill their regulatory mandate on the issue of protecting pollinators among their membership nations. Those paper are relevant to examine the effects of sub-lethal pesticide exposures on the health of honeybees (Apis mellifera), bumblebees (Bombus terrestris), and other bees. The weight-of-evidence of this review clearly demonstrated bees’ susceptibility to insecticides, in particular to neonicotinoids, and the synergistic effects to diseases that are commonly present in bee colonies. One important aspect of assessing and managing the risks posed by neonicotinoids to bees is the chronic effects induced by exposures at the sub-lethal levels. More than 90% of literature published after 2009 directly or indirectly demonstrated the adverse health effects associated with sub-lethal exposure to neonicotinoids,including abnormal foraging activities, impaired brood development, neurological or cognitive effects, and colony collapse disorder.