Protecting our rivers from an unlikely threat: pet flea treatments
We love our pets. But many of us don't realise that the monthly flea treatments we apply to our dogs and cats may be quietly poisoning our rivers and streams, including the Dart and its tributaries.
Alongside SongBird Survival, WildFish, Buglife, and dozens of leading conservation groups, universities, and veterinary professionals FOD is choosing to support a letter sent to Environment Minister at the Department for Environment, Food and Rural Affairs (Defra), calling for urgent action on two chemicals widely used in over-the-counter flea treatments: fipronil and imidacloprid.
Both chemicals are already banned for agricultural use - fipronil since 2017, imidacloprid since 2018 - yet they remain freely available in pet shops and supermarkets, often without any veterinary guidance. And once they wash off our pets into drains, they pass through sewage treatment largely unchanged.
The evidence is stark. Fipronil has been ranked the organic chemical of greatest concern in surface waters across England. Imidacloprid has been identified as one of the highest risk chemicals in the entire Greater London catchment. A 2026 Cardiff University study found reductions of over 90% in mayfly and caddisfly populations at sites with elevated imidacloprid levels. These are the invertebrates at the very base of the food web. They sustain the trout, dippers, and kingfishers that make rivers like the Dart so special and so fundamental for a functioning ecosystem.
New research from the University of Sussex has found these chemicals in wild bird feathers, nesting material, unhatched eggs, and dead chicks. The contamination is not confined to the water, it is moving through the entire ecosystem.
For those of us who have dedicated years to improving the health of the Dart catchment, this is deeply concerning. Pesticide contamination from agriculture has long been on our radar, but the role of veterinary parasiticides has been largely invisible in monitoring and regulation. It is a huge source of worry.
The letter calls on the Government to reclassify fipronil and imidacloprid pet treatments as prescription-only, so that a vet can assess whether they are truly necessary before they are used. It also calls for proper environmental risk assessment of all companion animal parasiticides, routine monitoring of their residues in our waterways, and a regulatory framework that genuinely accounts for harm to nature.
These are not unreasonable asks. There are effective, lower-risk alternatives already on the market. Requiring a prescription would not limit access to treatment, it would simply ensure the most environmentally damaging options are used only when genuinely needed.
What can you do?
If you have pets, speak to your vet about the environmental impact of flea treatments and ask whether a lower-risk alternative might be suitable. And if you'd like to add your voice, read the full letter and find out more via Buglife.
Image; Ollie. Flea and tick free without fipronil or imidacloprid treatments.