The Wildlife and Countryside Link and the Rivers Trust analysed Environment Agency water testing data for five harmful pesticides, known as neonicotinoids, and found that at least one of these was present in 29 out of the 283 sites measured between 2020 and 2022.
These included Clothianidin, Imidacloprid, and Thiamethoxam which have been banned for outdoor crop use in the UK since 2018 and are known to be harmful to pollinators and aquatic life. Clothianidin is a breakdown product of Thiamethoxam.
They also found Thiacloprid, which was banned in 2020 due to potential human health impacts, and Acetamiprid which is still authorised for UK use but is known to bioaccumulate and be highly toxic to birds, earthworms and moderately toxic to most aquatic organisms.
Clothianidin and Imidacloprid were most prevalent at the sites, with most exceeding the EU’s proposed Environmental Quality Standard (EQS) for what is deemed safe for aquatic life.
At 29% of the sites, the level of these pesticides was over four times the EQS level, according to the campaign group.
The highest concentrations were detected in the east of England, South East and West Midlands in the river Ivel, Waveney, Nene, Ouse and Tame.
The highest number of neonics found at single sites were detected in Yorks and Humber, the West Midlands and east of England.
Tessa Wardley, director of communications and advocacy at the Rivers Trust, said: “Our new analysis shows neonicotinoids at worrying levels at multiple sites. But this is likely to be just a drop in the ocean of neonicotinoid river pollution.
“Environment Agency monitoring of pesticides in our rivers is sorely lacking. Monitoring is infrequent and practically non-existent during wet weather when the risk of rapid flushing of these and other pesticides into our rivers is greatest. If we are to get a grip on this potentially devastating source of river pollution, we need effective monitoring that can actually reveal the scale of the problem.”
The results come as the government considers whether it will approve the use of Thiamethoxam - used on English sugar beet farms in the aphid pesticide Cruiser SB – for a fourth consecutive year.
READ MORE: ‘Toxic addiction’: Emergency authorisation granted for banned pesticide for third year in a row
The emergency authorisations have been controversial as they went against the expert recommendations.
Nick Mole, policy officer at Pesticide Action Network UK, described the findings as “hugely concerning”.
He said: “There must be no more ‘emergency’ extensions for the use of banned pesticides and the UK government must introduce a robust, effective and well-funded monitoring system for all UK waterbodies as a matter of urgency.”
In January 2023 the EU Court of Justice declared that emergency authorisations of prohibited neonicotinoid-treated seeds are not in line with EU law.
Barnaby Coupe, land use policy manager at The Wildlife Trusts, described it as “completely unacceptable” that the UK government continues to grant authorisations for harmful pesticides.
“It has ignored the science and the advice of its own experts in granting repeat authorisations to apply toxic neonicotinoids to our countryside, and the result is much diminished wildlife.”
A DEFRA spokesperson said: “Our comprehensive Plan for Water is tackling every source of pollution through more investment, stronger regulation and tougher enforcement, while ensuring the use of pesticides does not harm people or pose unacceptable risks to our rivers.
“In our forthcoming pesticides action plan we will also set out our ambition to minimise the risks and impacts of pesticides through an increased uptake of Integrated Pest Management across all sectors.
"More widely, we have more than doubled the funding to help farmers to improve slurry management, while also expanding our Sustainable Farming Incentive offer to pay farmers to reduce their use of insecticides.”