A British parliamentary committee has called for flea and tick treatments to be pulled off supermarket and pet shop shelves, and New Zealand researchers say the same chemicals are already showing up in wastewater here at concentrations high enough to damage freshwater life.
The House of Lords Environment and Climate Change Committee published its report, titled Paws for Concern, on Wednesday 5 August. It found that the intensive year-round dosing of cats and dogs with parasite products is not backed by good evidence, and that the chemicals are washing out of homes and into rivers in quantities that harm insects and other aquatic life. The committee wants the British government to end the general sale of the products off the shelf and through unchecked online subscriptions, and replace it with a system where a treatment is supplied only alongside individual advice about the animal’s lifestyle, location and actual clinical need.
Two of the chemicals at the centre of the report, fipronil and imidacloprid, were banned for outdoor agricultural use in Britain by 2018 because of the damage they do to bees and other insects. They remain freely available there, and here, in spot-on treatments squeezed onto the back of a pet’s neck. The British Veterinary Association said 93.5 percent of the vets it surveyed were concerned about the environmental impact of parasite treatments and 80 percent supported restrictions on their sale.
The New Zealand question is whether any of that applies here, and the early answer from researchers is that it does. Chloe McMenamin, a lecturer and researcher in the School of Environmental and Animal Sciences at Unitec, told the Science Media Centre she has spent four years testing for flea and tick chemicals in North Island wastewater. Her team has found imidacloprid, fipronil and fluralaner at what she described as “concentrations likely to cause ecological impact”, and the testing indicates the compounds pass through the wastewater treatment process “essentially unchanged”.
McMenamin said the sales model is the problem. “The current practice of selling flea and tick treatment products for pets freely over the counter for routine monthly use is increasingly difficult to justify given the weight of scientific evidence,” she said. She also pointed to overseas work showing the chemicals do not stay on the animal. Birds line their nests with moulted fur, and studies in Britain and Hungary have found the residues in unhatched eggs, dead chicks and the feathers of adult garden birds. Ponds where treated dogs swim have recorded levels exceeding safety thresholds for aquatic life for weeks after a dose.
How the chemicals get from a bathroom to a river is less exotic than people assume. Professor Leon Barron of Imperial College London, whose team supplied evidence to the committee, said most of it arrives through ordinary household plumbing. “After you use it, it washes off the pet, contaminates your skin, clothes, upholstery, and floors. When these are washed, it ends up down the drain,” he said. Barron said his group has tested thousands of water samples across British waterways and coastal areas, and these products “come up consistently as posing the worst risk to aquatic life”. Because treatment plants do not remove some of the compounds, he said, the contamination is not confined to raw sewage overflows but is present in water that has been treated.
Scale matters, and New Zealand is a heavily pet-owning country. The 2024 pet data report from Companion Animals New Zealand put pets in 63 percent of households, with an estimated 1.26 million cats and about 830,000 dogs. That is roughly two million cats and dogs in a population of about 5.3 million people, a higher ratio of pets to people than Britain has. Professor Melanie Kah of the University of Auckland’s School of Environment made the same point, noting that given the country’s “very high rate of pet ownership”, research here could prove very impactful. She said the substances face strict controls in farming because of their toxicity to aquatic life, but “such restrictions do not apply when they are used as pet treatments”.
That regulatory split exists in New Zealand too. Imidacloprid is one of five neonicotinoid insecticides the Environmental Protection Authority said in 2020 it intended to reassess, citing new information about environmental and human health effects. Flea treatments, though, sit in a different system, registered as veterinary medicines by the Ministry for Primary Industries under the agricultural compounds and veterinary medicines rules, where the assessment is built around the animal rather than the catchment the animal lives in.
Not everyone thinks a British report should drive New Zealand policy. Veterinarian Siobhan Ellis said the topic is important and valuable to be discussing, and supported calls for more research, data and education for vets on the environmental effects of the products. But she said fipronil and imidacloprid are “falling out of favour with NZ vets for newer products” about which much less is known environmentally, and that “the NZ environment is very different”, with less densely populated cities and a warmer climate that may mean a genuinely higher need for flea control. She recommended New Zealand do its own work before changing anything.
Dr Joanne Clapcott, president of the New Zealand Freshwater Sciences Society, urged the same caution while making the case for looking. She said the country’s rivers are already under pressure from well-established threats such as “excess nutrients, sediment, habitat loss and climate change”, and that the significance of pet medicines here is not yet known. What is needed, she said, is “sustained investment in freshwater monitoring and independent science” so emerging contaminants are picked up early rather than after the damage is done.
Professor Oliver Jones, a chemist at RMIT University in Melbourne, warned against overcorrecting. “Prophylactic treatment of pets for fleas and ticks is not a bad thing in itself. If you don’t treat an animal until after it is infected, you are potentially causing suffering that could be avoided,” he said, describing the evidence that the medicines reach the environment as very strong while the consequences remain less clear.
The practical advice from the researchers is modest and does not require anyone to stop treating a sick animal. Barron’s suggestion was simply to “talk to your vet and see if your animal is at risk of ticks and fleas and whether you actually need them”. McMenamin makes a similar case for treating when parasites are present rather than dosing on a monthly calendar out of habit. The committee’s recommendations now go to the British government for a response. Nothing in New Zealand changes as a result, but the wastewater results suggest the question is not a purely British one.
Do you treat your cat or dog every month, or only when you spot fleas? Tell us in the comments below.
This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job 🙂
Leave a Reply