17 Nov 2020
Researchers at the University of Sussex find two neurotoxic pesticides, both commonly found in flea products, exceeded accepted safe limits in some samples from 20 English rivers.
Paul Imrie
Job Title
Image: Emphyrio / Pixabay
Researchers have found widespread contamination of English rivers with two pesticides commonly used in veterinary flea products.
Fipronil or its metabolites were found in 98% of freshwater samples, with average concentration exceeding chronic safety thresholds fivefold.
Neonicotinoid imidacloprid was found in 66% of samples, with chronic toxicity limits for the latter exceeded at 7 out of 20 tested sites.
Full details of the study have been published in a paper in Science of the Total Environment.
The chemicals are banned for agricultural use because of their adverse environmental effects.
Vet Rosemary Perkins, a PhD student at the University of Sussex; and Dave Goulson, professor of biology at the university, examined 3,861 water samples collected by the Environment Agency in 20 English rivers from 2016-18.
The research was funded by the VMD, which lists 66 licensed veterinary products containing fipronil in the UK and 21 containing imidacloprid, either alone or in combination. Products include spot-on solutions, sprays and collars, and are a mixture of POM-V or over-the-counter/online products.
Dr Perkins said: “Fipronil is one of the most commonly used flea products, and recent studies have shown it degrades to compounds that are more persistent in the environment, and more toxic to most insects, than fipronil itself.
“Our results, showing that fipronil and its toxic breakdown products are present in nearly all of the freshwater samples tested, are extremely concerning.”
Prof Goulson said: “Fipronil and imidacloprid are both highly toxic to all insects and other aquatic invertebrates. Studies have shown both pesticides to be associated with declines in the abundance of aquatic invertebrate communities.
“The finding that our rivers are routinely and chronically contaminated with both of these chemicals – and mixtures of their toxic breakdown products – is deeply troubling.”
The paper, which also features Wayne Civil at the Environment Agency and vet Martin Whitehead as co-authors, identifies measures to minimise or prevent environmental harm from pet flea and/or tick products in the future.
It also notes the highest levels of pollution were found immediately downstream from wastewater treatment works, suggesting quantities of pesticides are passing from treated pets to rivers via household drains.
