Handwashing is a major source of pet pesticide pollution in UK rivers

Fipronil and imidacloprid are highly toxic pesticides that are no longer approved for use in outdoor agriculture, but continue to be widely used in pet flea treatments, typically applied to the back of the pet’s neck (known as spot-ons).

The researchers found that wastewater from sewage treatment works is a major source of fipronil and imidacloprid pollution in rivers. They conclude that pesticides used in flea products on domestic pets are washing down household drains, in concentrations exceeding safe limits for wildlife.

Owner handwashing was the largest source of emissions with fipronil or imidacloprid detected in all tests on pet owners for at least 28 days after a spot-on application to their pet. Current guidelines advise that owners should not touch pets in the 24 hours following product administration, but this research shows that pollution is occurring continuously for the entire duration of action of the product.

This study builds on previous research conducted by the Sussex researchers, which found that fipronil was detected in 98% of freshwater samples, and imidacloprid in 66%, and a paper by the Imperial researchers that showed these chemicals are reaching urban rivers in concentrations that are known to harm aquatic life.

Professor Dave Goulson from the University of Sussex, who supervised the research, commented, “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. Pet owners will also be upset to learn that they are accidentally polluting our rivers by using these products.”