Scientists have recently discovered that pesticides commonly used as flea treatments for pets are contaminating rivers. The new research reveals widespread contamination, with two neurotoxic pesticides found in concentrations that far exceed accepted safe limits. More specifically, researchers have found widespread contamination of English rivers with two neurotoxic pesticides commonly used in veterinary flea products: fipronil and the neonicotinoid imidacloprid.
These chemicals (fipronil and the neonicotinoid imidacloprid) are banned for agricultural use due to the adverse environmental effects, but there is minimal environmental risk assessment for pesticides used on domestic cats and dogs. This is due to the assumption that there are likely to be fewer environmental impacts due to the amount of product used. But there is growing concern that this assumption may be incorrect.
“The use of pet parasite products has increased over the years, with millions of dogs and cats now being routinely treated multiple times per year…Fipronil is one of the most commonly used flea products, and recent studies have shown that 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.” -Rosemary Perkins, researcher
According to the Veterinary Medicines Directorate (VMD), who funded the research, there are 66 licensed veterinary products containing fipronil in the UK, and 21 containing imidacloprid, either alone or in combination with other parasiticides. These include spot-on solutions, topical sprays and collars impregnated with the active ingredient.
While some of these products can be purchased only with a veterinary prescription, others can be bought without a prescription from pet shops, supermarkets, pharmacies and online. Many pet owners receive year-round preventative flea and/or tick treatment from their vet practice via healthcare plans.
Fipronil has a history of very limited agricultural use prior to its ban in 2017. It is also licensed for use in ant and cockroach baits, however only one product is licensed for use by non pest-control professionals. Use on pets seems to be the most plausible source of the widespread contamination of rivers.
Scientists examined the occurrence of fipronil and imidacloprid in English rivers as indicators of the potential contamination of waterways from the use of pet flea treatments.
They found that the average fipronil concentration across the rivers sampled by the Environment Agency exceeded chronic safety thresholds five-fold. The overall pollution levels in English rivers indicate that fipronil and its toxic breakdown products pose a high risk to aquatic ecosystems.
While, in most rivers, imidacloprid was found to pose a moderate risk, in seven out of the 20 rivers sampled there was a high environmental risk.
“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.” -Professor Dave Goulson
How Neurotoxic Chemicals Move from Pets to Waterways
The highest levels of pollution were found immediately downstream of wastewater treatment works, supporting the hypothesis that significant quantities of pesticide may be passing from treated pets to the environment via household drains.
Bathing of pets treated with spot-on fipronil flea products has been confirmed as a potentially important route to waterways for fipronil via sewers, and the washing of hands, pet bedding or other surfaces that have come into contact with treated pets are potential additional pathways for entry to sewers. Other pathways for contamination of waterways includes swimming and rainfall wash-off from treated pets. The strong correlation between fipronil and imidacloprid levels across the river sites tested suggest that they may be coming from a common source.
Pet Flea Products in the U.S. containing
fipronil and/or imidacloprid
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Journal Reference: Rosemary Perkins, Martin Whitehead, Wayne Civil, Dave Goulson. Potential role of veterinary flea products in widespread pesticide contamination of English rivers. Science of The Total Environment, 2020; 143560. Summary; DOI: 10.1016/j.scitotenv.2020.143560