Insecticiden

Il n’y a, bien sûr, pas de condamnation pécuniaire, mais le coup est rude. Le Tribunal de l’Union européenne a condamné la Commission européenne, mercredi 16 décembre, pour « avoir manqué à [ses] obligations » sur le dossier des perturbateurs endocriniens (PE). En vertu du règlement européen de 2012 sur les biocides, Bruxelles devait publier, au plus tard le 13 décembre 2013, les critères scientifiques permettant de réglementer ces molécules de synthèse agissant sur le système hormonal et présentes dans une variété de produits courants (pesticides, plastifiants, bisphénols, solvants, etc.). Or, constate le Tribunal dans son arrêt, « la Commission n’a pas adopté de tels actes » définissant les PE, en dépit d’« une obligation claire, pré́cise et inconditionnelle de [les] adopter » précisée par la réglementation.

To determine the exposure of native bees to pesticides, bees were collected from an existing research area in northeastern Colorado in both grasslands (2013–2014) and wheat fields (2014). Traps were deployed bi-monthly during the summer at each land cover type and all bees, regardless of species, were composited as whole samples and analyzed for 136 current-use pesticides and degradates. This reconnaissance approach provides a sampling of all species and represents overall pesticide exposure (internal and external). Nineteen pesticides and degradates were detected in 54 composite samples collected. Compounds detected in > 2% of the samples included: insecticides thiamethoxam (46%), bifenthrin (28%), clothianidin (24%), chlorpyrifos (17%), imidacloprid (13%), fipronil desulfinyl (7%; degradate); fungicides azoxystrobin (17%), pyraclostrobin (11%), fluxapyroxad (9%), and propiconazole (9%); herbicides atrazine (19%) and metolachlor (9%). Concentrations ranged from 1 to 310 ng/g for individual pesticides. Pesticides were detected in samples collected from both grasslands and wheat fields.

Das Paradigma von Paracelsus «Dosis sola facit venenum» (nur die Dosis macht das Gift) bildet noch immer die Grundlage für die Beurteilung der Risiken von Chemikalien. Bei der Risikoanalyse geht man davon aus, dass – mit Ausnahme der Genotoxizität – für praktisch alle potenzielle Risiken von chemischen Substanzen Schwellenwerte definiert werden können, unterhalb derer keine toxische Wirkung beobachtet wird. Dieser Ansatz wird unserer Meinung nach als einer der größten Fehler der Toxikologie in die Geschichte eingehen. Denn dabei wird die kumulative Toxizität mancher giftiger Substanzen ungenügend berücksichtigt. Bereits in den 1940er-Jahren kamen der Pharmakologe Hermann Druckrey und der Mathematiker Karl Küpfmüller mit theoretischen Ansätzen zu Dosis-Wirkungs-Beziehungen zum Schluss, dass der Zeitfaktor eine entscheidende Rolle bei der Wirkung von toxischen Substanzen spielen kann. Ihr Ausgangspunkt war die heute allgemein akzeptierte Ansicht, dass die pharmakologische oder toxische Wirkung einer Substanz durch die Wechselwirkung mit einem spezifischen Rezeptor entsteht, bzw. durch die Bindung an diese ‹Andockstelle› einer Zelle. Druckrey und Küpfmüller konnten zeigen, dass irreversible Wechselwirkungen – also Bindungen – zu einem Effekt führen, der sowohl von der Dosis als auch von der Zeit abhängig ist.

Neonicotinoids may be contributing towards the disappearance of butterflies from the countryside, according to the first scientific study to examine the effect of the controversial agricultural pesticides on British butterflies. Researchers found that 15 of 17 species which commonly live on farmland – including the small tortoiseshell, small skipper and wall butterfly – show declines associated with increasing neonic use. Using population data from 1985 to 2012 gathered on more than 1,000 sites across the country, scientists at the universities of Stirling and Sussex, in partnership with Butterfly Conservation and the Centre for Ecology and Hydrology, found that neonicotinoid use better explained steep population declines than other factors. Neonics were first introduced in 1994 and usage increased at its fastest rate during the first decade of the 21st century, when farmland butterflies also experienced a precipitous decline, despite a doubling in conservation spending and predictions that climate change would benefit most species. The Essex skipper declined by 67% between 2000 and 2009 and the small skipper declined by 62% in the same period. Both species’ caterpillars live on grasses found on field margins. Other common farmland butterflies to have suffered steep declines include the small tortoiseshell (64%), the wall brown (37%) and the large skipper (35%). According to the study, published in the journal PeerJ, these declines have largely occurred in England, where neonic usage is at its highest; in Scotland, where spraying of the pesticide is comparatively low, butterfly numbers are stable.

There has been widespread concern that neonicotinoid pesticides may be adversely impacting wild and managed bees for some years, but recently attention has shifted to examining broader effects they may be having on biodiversity. For example in the Netherlands, declines in insectivorous birds are positively associated with levels of neonicotinoid pollution in surface water. In England, the total abundance of widespread butterfly species declined by 58% on farmed land between 2000 and 2009 despite both a doubling in conservation spending in the UK, and predictions that climate change should benefit most species. Here we build models of the UK population indices from 1985 to 2012 for 17 widespread butterfly species that commonly occur at farmland sites. Of the factors we tested, three correlated significantly with butterfly populations. Summer temperature and the index for a species the previous year are both positively associated with butterfly indices.