Open letter, veterinary parasiticides in the environment

An open letter to the Environment Minister regarding veterinary parasiticides in the environment. Read the full letter below.

Have you asked your MP to sign the Early Day Motion (EDM) about toxic pesticides used in tick and flea treatments?

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Dear Minister,

We are environmentalists, academics and veterinary professionals, writing to express our urgent concern about the mounting evidence that fipronil and imidacloprid- two chemicals widely used in over‑the‑counter flea and tick treatments for pets- are contaminating the UK’s rivers, lakes, ponds and wildlife.

Veterinary medicines are vital for protecting animal and human health. Pet owners should feel confident that the products they use protect their pets, their health and the environment. Yet the current regulatory system does not adequately account for environmental harm.

Fipronil and imidacloprid (a neonicotinoid), for instance, were banned for agricultural use in 2017 and 2018 respectively, but are still widely sold as spot-on and collar treatments, often used on a monthly, preventative basis by pet owners without any veterinary advice. There are around 11 million dogs and 10.5 million cats in the UK, with upwards of 75% receiving flea treatments in the last year. Recent research funded by the Department for Environment, Food & Rural Affairs shows that a significant proportion of these chemicals ultimately go down the drain, where they are not removed by wastewater treatment plants or septic systems, allowing them to enter rivers.  Recent evidence shows also how fipronil and imidacloprid can reach rivers through a further ‘down the drain’ route where household wastewater is misconnected to surface drains rather than foul sewers, thus bypassing treatment entirely.

There is a substantial and growing body of scientific evidence that fipronil and imidacloprid from pet parasiticides are contaminating our environment and likely to be having a significant effect on the aquatic ecosystem. Fipronil and imidacloprid are frequently detected in UK rivers, often at levels above ecological safety thresholds. The level of pollution is high with imidacloprid recently identified as one of the highest risk chemicals of concern across the whole Greater London catchment, while fipronil has been ranked the organic chemical of most concern in surface waters in England, and top ten in groundwaters.

Both chemicals are highly toxic and have been associated with freshwater invertebrates declines, with species such as mayflies and dragonflies particularly at risk. A 2026 study by Cardiff University found reductions of over 90% in the abundances of species of mayflies and caddisflies at sites with increased concentrations of imidacloprid. Their combined effects disrupt food webs and undermine ecosystem functions with cascading effects on other wildlife, including fish and birds that depend on invertebrates as a vital food source. New studies from the University of Sussex give some of the first evidence in wild birds that these chemicals are being passed from contaminated nesting material (pet fur) into eggs and avian tissue, and that they are also widely found in bird feather samples, raising urgent questions about the broader ecological risks beyond polluting rivers.

Some veterinary organisations have taken the steps that are available to them to address the environmental impact of these products and promote responsible use. However, the widespread extent of presence of these chemicals in the environment mean broader, urgent action from the industry is necessary. The British Veterinary Association encourages professionals to avoid blanket prophylactic treatment, and instead risk assess the use of parasiticides for individual animals, and where possible and reasonable avoid prescribing topical products for pets which are likely to swim or be bathed.

While we welcome the Government’s Pharmaceuticals in the Environment Group roadmap, progress is too slow. Environmental organisations and academic experts must be more closely involved. This issue will not be solved by improved product labels or user compliance alone. It requires a regulatory framework that fully recognises and addresses environmental risk. At present these products can be widely distributed without professional advice and without prescription. Given the wide range of UK-approved parasiticides with non-banned active ingredients, restricting fipronil and imidacloprid would not limit treatment availability. Broader regulation of all active ingredients would better protect companion animals and support policy decisions aimed at reducing environmental pollution.

There is minimal environmental risk assessment before veterinary parasiticides go to market. Drugs for companion animals are not subject to a Phase II environmental risk assessment – where exposure and ecotoxicity are evaluated in detail – unlike veterinary medicines used in livestock.

The Government’s monitoring of veterinary medicine residues in the environment also remains limited and inconsistent.

To deal with the immediate threat from fipronil and imidacloprid to the environment, we urge Government to:

• Provide a clear timeline for the Veterinary Medicines Directorate’s review of distribution categories for pet parasiticides containing fipronil and imidacloprid; and

• Reclassify pet parasiticides containing fipronil and imidacloprid as prescription only, ensuring appropriate veterinary advice is given upon prescription.

Further to this, we urge the Government to urgently address systemic failures in the regulation of veterinary medicines and the evaluation of their environmental impacts by:

• Adopting Environmental Quality Standards for veterinary medicines, prioritising pesticides banned in outdoor agricultural use, such as fipronil and imidacloprid;

• Establishing routine national monitoring of veterinary parasiticide residues in surface waters;

• Strengthening the environmental duties within veterinary medicines legislation and authorisation decisions;

• Requiring full environmental risk assessments for widely used companion animal parasiticides;

• Improving transparency of regulatory data and environmental assessments and introducing mechanisms for ongoing re-evaluation of authorised products in light of new environmental evidence;

• Better aligning regulatory frameworks for pesticides used on different categories – namely veterinary parasiticides, plant protection products and biocides – and environmental protection law.

We would welcome clarification on the steps that the Government intends to take to ensure that veterinary medicines regulation protects animal welfare, public health and recognises impact on the natural environment.

Yours sincerely,

List of signatories:

Professor Alex Ford, Professor of Biology – University of Portsmouth
Dr Alexander Lees, Reader in Biodiversity – Manchester Metropolitan University
Dr Andrew Prentis, Veterinary Surgeon & Visiting Fellow – Grantham Institute at Imperial College London
Dr Cannelle Tassin de Montaigu, Research Fellow – University of Sussex
Professor Carl Sayer, Professor of Freshwater Ecology – University College London
Professor Dave Goulson, Professor of Biology – University of Sussex
Professor Gary Fones, Professor of Environmental Aquatic Chemistry – University of Portsmouth
Professor Emeritus Ian G. Cowx – Hull International Fisheries Institute, University of Hull
Professor Michael Antonou, Professor Emeritus in Molecular Genetics and Toxicology – King’s College London
Dr Miya Warrington, Research fellow in Ecology and Conservation – Oxford Brookes University
Professor Steve Ormerod, Professor of Ecology – Cardiff School of Biosciences/Water Research Institute

Angling Trust – Jamie Cook, CEO
British Dragonfly Society – Dr Pam Taylor, Trustee and Convenor of the BDS Dragonfly Conservation Group
British Trust for Ornithology – Professor Juliet Vickery, CEO
Bumblebee Conservation Trust – Dr Andrew Impey, CEO
Campaign for National Parks – Dr. Rose O’Neill, Chief Executive
The Exmoor Society – Kate O’Sullivan, Chair
Friends of the Earth – Paul De Zylva, Senior Analyst
Froglife – Kathy Wormald, CEO
The Game and Wildlife Conservation Trust – Dr Alastair Leake, Director of Policy
Greenpeace UK – Nina Schrank, Nature Campaign Lead
Institute of Fisheries Management – Paul Coulson, CEO
MCS-Aware – Alicia Hurrell, Charity Manager
People’s Trust for Endangered Species – Nida Al-Fulaij, CEO
Pesticide Action Network UK – Nick Mole, UK Policy Manager
River Action UK – James Wallace, CEO
The Rivers Trust – Dr Rob Collins, Director Policy and Science
RSPB – Katie-Jo Luxton, Executive Director – Global Conservation
Surfers Against Sewage – Henry Swithinbanks, Policy and Advocacy Lead
Westcountry Rivers Trust – Dr. Laurence Couldrick, CEO
Wildlife & Countryside Link – Richard Benwell, CEO
The Wildlife Trusts – Joan Edwards OBE, Director Policy and Public Affairs

Dr Andre Menache MRCVS – Director, Progressive Veterinary Association
Dr Cyril Bennet MBE – Fellow of the Royal Entomological Society of London
Jeff Gill – campaigner
Dr Mark Jones MRCVS – Policy Advisor, Progressive Veterinary Association
Dr Ueli Zellweger – retired vet and environmental campaigner