Two pesticides found in common flea and tick treatments for pets are turning up in UK waterways at levels high enough to damage wildlife. That is the finding of a report by the Environment and Climate Change Committee of the UK's House of Lords.
According to New Scientist, the report calls for flea and tick treatments to be sold only after consultation with a vet, pharmacist or qualified pet shop staff. The committee's position is that people should not treat their pets for parasites unless the animals actually need it.
The two pesticides at the center of the concern are fipronil, a broad-spectrum insecticide, and imidacloprid, a neonicotinoid. Both were once used in agriculture until they were banned. They continued to be detected in rivers after the farming bans, and researchers initially assumed this was a legacy of agricultural use. More recent work suggests pet parasite medications are now the primary source.
Rosemary Perkins at Imperial College London, one of the experts who gave evidence to the committee, described the scale of the problem. "They're incredibly potent at extremely low levels," she said of the two pesticides. With more sensitive testing now available, they are turning up "pretty much everywhere in waterways," she said.
The pesticides are reaching rivers partly through spot-on flea treatments applied directly to pets' skin. In many UK waterways, levels are high enough to harm invertebrates including mayflies, dragonflies and caddisflies. Those insects are food sources for fish and birds, meaning the effects move up the food chain.
The report identifies a core regulatory failure. There has been no rigorous environmental assessment of pet parasite treatments before approval. Regulators assumed that medicines used in non-food animals like cats and dogs posed negligible environmental risk. Perkins said that assumption no longer holds. "It's really opened up a Pandora's box, because we have dozens of these products that have been approved based on this assumption that we now know is not scientifically valid," she said.
The report also raised concerns about human health. "There is also worryingly insufficient evidence to assess whether or not [pet parasite medicines] are harmful to human health," the report states.
The committee also criticized the independence of regulators. Both UK and international regulators "appear to be too influenced by and beholden to the views of the industry," the report states.
Perkins said the scope of the problem extends beyond the UK. The same products are sold across many countries. "This is a worldwide issue," she said. "There's been a historical assumption that any veterinary medicine used in non-food animals — cats and dogs, companion animals — is associated with negligible environmental risk. Effectively, they have no meaningful environmental risk assessment."
The full scale of environmental damage remains unclear. The report acknowledged that the true extent of harm from these treatments has not yet been measured.
