Potential role of veterinary flea products in widespread pesticide contamination of English rivers

summary of:
Potential role of veterinary flea products in widespread pesticide contamination of English rivers
Author(s):
R. Perkins, M. Whitehead, W. Civil and D. Goulson
Published in:
Date:
November 2020
DOI:
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In our edition of: Feb 2021

our summary:

Perkins, R. et al. (2021) Potential role of veterinary flea products in widespread pesticide contamination of English rivers. Science of The Total Environment, 755 (1), 143560

The paper, entitled Potential role of veterinary flea products in widespread pesticide contamination of English rivers, was published in the journal Science of The Total Environment and reports on research carried out at the University of Sussex and funded by the Veterinary Medicines Directorate.

The aim of the research was to examine the occurrence of fiprones (fipronil and two of its main metabolites) and imidacloprid in English rivers, as indicators of the level of contamination of waterways with these products.

Samples of river water were collected as part of the Environment Agency surveillance program and tested for imidacloprid and fipronil (between 2016-2018) and for the metabolites fipronil sulfone and fipronil sulfide (between 2017-2018). There were 20 sample sites for which complete data were available included in the analysis. River sample site locations were classed as either less than 2 km downstream of wastewater treatment works (WTW) (5 sites, all of which were urban), or greater than 2 km downstream of WTW or with no WTW impact (15 sites, including 4 urban sites and 11 agricultural sites).

The authors acknowledge that there are currently no environmental quality standards for imidacloprid, fipronil, fipronil sulfone or fipronil sulfide in British surface waters, so acute and chronic toxicity limits were based on published data, which they state are higher than many limits that have been proposed or adopted elsewhere.

Risk quotients were calculated for each substance under investigation, by dividing the measured concentration by the toxicity limit, indicating the extent to which the toxicity limit has been exceeded.

Fipronil was detected in all 20 sites sampled between 2016 and 2018, and in 1303 out of 1322 individual samples. Fipronil sulfone was detected at all 18 sites and Fipronil sulfide was detected in 16 out of 18 sites sampled between 2017 and 2018, (in 586 and 417 out of 607 individual samples respectively). In all cases the levels detected were higher at the sites <2 km downstream from WTW, although in the case of fipronil sulfide this difference was not statistically significant. Imidacloprid was detected in 19 out of 20 sites sampled between 2016 and 2018, and in 873 out of 1325 individual samples. Sites within 2 km of WTW had significantly higher concentrations of imidacloprid than sites >2 km downstream of WTW.

Sixteen out of twenty sites had mean concentrations that exceeded the chronic toxicity limit for fipronil, including all the sites <2 km downstream of WTW, and six sites had mean concentrations that exceeded the acute toxicity limit. All sites tested for fipronil sulfone had mean values that exceeded the chronic toxicity limit, and 17 out of the 18 sample sites had mean values that exceeded the acute toxicity limit.

The chronic toxicity limits for fipronil sulfone and fipronil sulfide are below the limit of detection, meaning that all samples in which these compounds were detected exceeded the chronic toxicity threshold.

The authors conclude that fipronil and its toxic metabolites pose a high risk to the aquatic environment while imidacloprid was considered to pose a moderate to high risk to the aquatic environment as it is less toxic than fiprones to most aquatic insect species and has higher acute and chronic toxicity limits.

As the use of fipronil and imidacloprid in agriculture have now been banned the authors conclude that the most likely source for the contamination is the fipronil and imidacloprid from “spot-on” ectoparasiticides for pets.

Although the paper only reports on data from sites in 20 English rivers it does suggest that further research should be carried out to determine the environmental risks associated with the use of these products and on the effect of companion animal parasiticides on the wider environment.

While this research is new it is not the first time that concerns have been raised regarding the effect of veterinary medicines on the wider environment, with concerns about the risk of Diclofenac to vultures and neonicotinoids on bees already having made the news.

Image copyright attribute: Luboslav Ivanko

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