Imidacloprid, the largest selling insecticide in the world, has received particular attention from scientists, policymakers and industries due to its potential toxicity to bees and aquatic organisms. The decline of aquatic macro-invertebrates due to imidacloprid concentrations in the Dutch surface waters was hypothesised in a recent paper by Van Dijk, Van Staalduinen and Van der Sluijs (PLOS ONE, May 2013). Although we do not disagree with imidacloprid's inherent toxicity to aquatic organisms, we have fundamental concerns regarding the way the data were analysed and interpreted. Here, we demonstrate that the underlying toxicity of imidacloprid in the field situation cannot be understood except in the context of other co-occurring pesticides. Although we agree with Van Dijk and co-workers that effects of imidacloprid can emerge between 13 and 67 ng/L we use a different line of evidence. We present an alternative approach to link imidacloprid concentrations and biological data. We analysed the national set of chemical monitoring data of the year 2009 to estimate the relative contribution of imidacloprid compared to other pesticides in relation to environmental quality target and chronic ecotoxicity threshold exceedances. Moreover, we assessed the relative impact of imidacloprid on the pesticide-induced potential affected fractions of the aquatic communities. We conclude that by choosing to test a starting hypothesis using insufficient data on chemistry and biology that are difficult to link, and by ignoring potential collinear effects of other pesticides present in Dutch surface waters Van Dijk and co-workers do not provide direct evidence that reduced taxon richness and abundance of macroinvertebrates can be attributed to the presence of imidacloprid only. Using a different line of evidence we expect ecological effects of imidacloprid at some of the exposure profiles measured in 2009 in the surface waters of the Netherlands.
Citation: Vijver MG, van den Brink PJ (2014) Macro-Invertebrate Decline in Surface Water Polluted with Imidacloprid: A Rebuttal and Some New Analyses. PLoS ONE 9(2): e89837. doi:10.1371/journal.pone.0089837
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An attempt to debunk a groundbreaking Utrecht university study
Vijver and van den Brink attempt to debunk the important study by Utrecht university scientists Van Dijk, Van Staalduinen and Van der Sluijs (PLOS ONE, May 2013) that underpins the decline of invertebrates in areas polluted with imidacloprid. They completely ignore the evidence on dose-response relationships of imidacloprid in arthropods published by Sanchez-Bayo and Tennekes since 2009, demonstrating that the risks of chronic exposure have been seriously underestimated and that new approaches to risk assessment, i.e., time to effect analyses in relation to exposure concentrations, are urgently required for realistic assessments of the risks associated with pesticide pollution of the environment. There is not a shadow of doubt that imidacloprid pollution of the environment kills non-target invertebrate species and I can see no valid reason to dispute the likewise conclusion of the Utrecht university scientists. The co-author of the current paper, Paul van den Brink, acknowledges that his Wageningen university chair was cofunded between 2008 and 2011 by pesticide producers Bayer and Syngenta but he doesn't regard this as a conflict of interest. Van den Brink doesn’t claim that imidacloprid poses less risks or toxicity than stated in the Van Dijk et al. (2013) paper but criticizes their methodology. May be so, but his current paper clearly serves the interests of pesticide producers by watering down the evidence implicating imidacloprid in the decline of invertebrates and invertebrate-dependent species.