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How to Minimize Pet's Contribution to Water Pollution

Recent research discloses that handwashing in the weeks following spot-on flea and tick treatments is the primary source of pet pesticide pollution in rivers.

Image Credit: Imperial College London

To address harmful pet pesticides flowing into waterways, researchers from Imperial College London and the University of Sussex are advocating for a reassessment of the regulatory framework and prescribing procedures.

Highly toxic pesticides like fipronil and imidacloprid are still used to treat pets for fleas; these treatments are usually applied to the back of the pet's neck and are no longer authorized for use in outdoor agriculture.

The researchers discovered that a significant source of imidacloprid and fipronil pollution in waterways is wastewater from sewage treatment plants. They came to the conclusion that household pesticide concentrations are higher than those that are safe for wildlife and that these pesticides are found in flea products used on domestic pets.

Significant Source of Contamination

Samples from 98 dogs administered spot-on fipronil or imidacloprid were gathered by the researchers, who then assessed the extent to which owner handwashing, dog bathing, and bedding washing contributed to domestic sewage and consequent wastewater pollution.  The study discovered that pesticide washoff happened along all three channels.

When fipronil or imidacloprid was discovered in all tests on pet owners for at least 28 days following a spot-on application to their pet, owner handwashing was the main source of emissions. According to current rules, owners should avoid touching their pets for 24 hours after administering a treatment; however, this research demonstrates that contamination occurs continually throughout the substance’s whole duration of action.

This research confirms that fipronil and imidacloprid used in spot-on flea products are important surface water pollutants. With around 22 million cats and dogs in the UK, we urgently need to rethink how these products are regulated and used.

Rosemary Perkins, Study First Author and Veterinary Surgeon, University of Sussex

Guy Woodward said, “Despite these chemicals being banned from outdoor agricultural use for several years, we are still finding them in UK freshwaters at levels that could harm aquatic life, and this paper shows how domestic pet flea and tick treatments, a largely overlooked but potentially significant source of contamination, could be polluting our waterways.”

Reviewing Practices

This study expands upon earlier research by the Sussex researchers, who discovered that 66% of freshwater samples had fipronil and 98 % had imidacloprid. Additionally, a paper by Imperial researchers revealed that these chemicals are making their way into urban rivers at concentrations known to be harmful to aquatic life.

Now that pet flea medications are on the market, the researchers are urging a reassessment of prescribing and regulatory procedures because the existing products do not account for the amount of river contamination caused by down-the-drain wash-off. Studies have shown that significant emissions to the aquatic environment are produced even when product recommendations are followed.

Recently, the British Veterinary Association released a policy statement suggesting that vet clinics steer clear of annual parasite treatment programs and give individual veterinarians the freedom to have educated conversations with their patients.

These two chemicals are extremely potent neurotoxic insecticides and it is deeply concerning that they are routinely found on the hands of dog owners through ongoing contact with their pet and their owners will also be upset to learn that they are accidentally polluting our rivers by using these products.

Dave Goulson, Research Supervisor and Professor, University of Sussex

Journal Reference:

Perkins, R.,, (2024). Down-the-drain pathways for fipronil and imidacloprid applied as spot-on parasiticides to dogs: Estimating aquatic pollution. Science of the Total Environment.

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