Abstract
Anthe et al. (Environ Sci Eur 32:147, 2020. https://doi.org/10.1186/s12302-020-00424-4) develop a mathematical model to calculate the contribution of veterinary medicinal products (VMPs) to the levels of imidacloprid observed in the UK water monitoring programme. They find that VMPs make only a very small contribution to measured pollution levels, and that the estimated concentrations do not exceed ecotoxicological thresholds. However, shortcomings in methodology—including the implicit assumption that imidacloprid applied to pets is available for release to the environment for 24 h only and failure to incorporate site-specific sewage effluent data relating to measured levels—raise questions about their conclusions. Adjusting for these and other deficiencies, we find that their model appears consistent with the conclusion that emissions from VMPs may greatly exceed ecotoxicological thresholds and contribute substantially to imidacloprid waterway pollution in the UK. However, the model utilises imidacloprid emissions fractions for animals undergoing the different scenarios (for example, bathing) that are extrapolated from unpublished studies that do not clearly resemble the modelled scenarios, with insufficient evidence provided to support their derivation. As a result, we find that the model presented by Anthe et al. provides no reliable conclusions about the contribution of veterinary medicinal products to the levels of imidacloprid in UK waterways.
Highlights
Imidacloprid has been found to contaminate many surface waters around the world, at levels that pose a significant risk to the diverse communities that these ecosystems support [10, 16, 21]
*Correspondence: rp442@sussex.ac.uk 1 School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK Full list of author information is available at the end of the article initial calculations of exposure concentrations in surface waters from the treatment of pets with imidacloprid in The Netherlands show that the environmental threshold of 8.3 ng/l would be exceeded if only 1.15% of applied imidacloprid passed from treated pets to waterways via household drains [19]
Anthe et al do not acknowledge or discuss this significant and highly relevant pattern in the data they present. They use the calculated predicted environmental concentration (PEC) from their model to argue that Veterinary medicinal product (VMP) do not contribute substantially to imidacloprid pollution of UK waterways, but do not provide any substantial alternative explanation for the imidacloprid pollution seen, or for why higher levels are consistently found in locations immediately downstream of STPs, other than to conclude that “imidacloprid concentrations in UK surface waters cannot be attributed to a specific end-use of the compound but may result from various applications”
Summary
Imidacloprid has been found to contaminate many surface waters around the world, at levels that pose a significant risk to the diverse communities that these ecosystems support [10, 16, 21].
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