Broads Authority shares concerns around impact of flea treatments on waterways

The Broads Authority is joining calls for better awareness and understanding around the significant negative impacts that dog and cat flea treatments can have on our waterways and welcomes the Government's new plan to address this pollution.

A light-green coloured dragonfly is seen perched on top of a body of water laying eggs, with its tail kinked at an angle. The rest of the image is out of focus but gives the impression of a shimmering river scene at dawn or dusk.Ongoing research has shown that spot-on flea treatments containing insecticides such as fipronil and imidacloprid pose significant risks to aquatic wildlife in waterways across the UK. These powerful insecticides are banned from agricultural use due to their harmful environmental effects, but can still be commonly found in readily-available pet products.

The issue arises as these flea treatments, which are applied to dogs and cats, don’t just stay on pets. When dogs swim, get wet, or are washed (or we stroke them and wash our hands) harmful chemicals enter the waterways via drainage systems. The insecticides persist on a pet’s coat for weeks and the chemicals can remain active for up to 90 days, even though they kill fleas within just 24-36 hours.

At particular risk are insects such as dragonflies, damselflies and freshwater beetles. These species are essential parts of a healthy wetland ecosystem. They spend much of their life underwater and are essential to the food chain, and provide food for fish, birds, and other wildlife. However, they are extremely sensitive to pollution.

Once in the water, insecticides can wipe out aquatic invertebrates and disrupt the delicate balance of our wetland ecosystems. For example, declines in the population of mayfly nymphs may mean less food for species such as perch, which then has a knock-on effect for bird species like great-crested grebes which feed on fish.

The chemicals can also directly impact other species. Studies have shown that bird nests which have been lined with treated animal fur contain high amounts of the chemicals found in flea treatments. Evidence suggests that these chemicals are directly harmful to birds, eggs and chicks, with a greater number of unhatched eggs or dead chicks in nests due to a higher concentration of insecticides.

The Government's new plan is an important step in tackling the presence of harmful chemicals. We believe that better awareness around these negative impacts and encouraging understanding of the simple changes that pet owners can make will help to lessen the risk. We welcome an evidence-based review followed by consideration of regulatory actions based on the findings.

To help the environment, pet owners can:

Two small dogs can be seen sat on the top of a white boat looking towards the camera, they are staring directly at the lens and appear to be at ease. Both are white/brown in colour and are wearing dog life jackets.

  • Consider less-toxic flea and tick treatments, such as those containing dimethicone, which work by physically immobilising parasites rather than poisoning them.
  • Stop their dog from entering rivers, lakes, ponds or ditches if they have been recently treated with spot-on treatments.
  • Choose oral chewable tablets that offer protection against fleas and ticks but don’t require insecticides to be applied to the coat.
  • If spot-on treatments must be used, apply them only when necessary (as not all pets require year-round use) and try not to get any treatment on their hands during application.

Jonathan Newman, Senior Advisor on Biologically Active Substances at the Environment Agency, said:

“It is important that pet health is prioritised, but not at the expense of the environment.

“Spot-on flea and tick treatments contain substances that can pose a significant risk to aquatic insects, and we encourage pet owners and veterinary professionals to be mindful of these environmental risks when choosing and applying treatments.”

Andrea Kelly, Environment Policy Adviser for the Broads Authority added:

“It is shocking just how serious the negative impacts might be of these flea treatments on our waterways, especially considering how readily-available the products are from vets, supermarkets or online stores.

“Given how many people love seeing kingfishers and other wildlife when on the rivers, we believe that a lack of awareness is the main reason why this has become such a widespread form of pollution. Pet owners aren’t necessarily tuned in to the environmental dangers posed by these treatments as the issues have not been widely publicised.”

“We hope that by adding our name to the list of organisations working to raise awareness of this issue we can better educate pet owners and encourage them to change their habits to help our precious wetland habitats.”

For more information see the page on our website: https://www.broads-authority.gov.uk/looking-after/managing-land-and-water/water-quality/flea-treatments-and-their-impact-on-water-quality

Thursday 31 July 2025

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