Pesticides harmful to bees have been detected in the majority of English waterways tested over the past year, according to data analysed by two environmental charities.

The Rivers Trust and Wildlife and Countryside Link found that neonicotinoid pesticides, known for their damaging effects on pollinators, were present in 85% of rivers tested by the Environment Agency between 2023 and 2024.

These pesticides, which are banned in the UK, were approved for emergency use by the previous government to combat a disease threatening sugar beet crops. This decision, made by the Department for Environment, Food and Rural Affairs (Defra), is now under investigation by the Office for Environmental Protection (OEP).

The government promised “to ban the use of neonicotinoid pesticides that threaten bees and other vital pollinators.”

The OEP is examining whether Defra’s emergency authorisation for neonicotinoid use in 2023 and 2024 complied with environmental laws, raising questions about the government’s promise to ban pesticides that harm bees and other pollinators.

Neonicotinoids are a class of insecticides used to control pests in agriculture, horticulture, and veterinary medicine. However, they are highly toxic to bees and other beneficial insects.

Despite their ban, sugar beet farmers were allowed to use these pesticides to protect crops from virus yellows, a disease spread by aphids.

Dan Green, agriculture director for British Sugar, defended the decision, stating that the pesticide was necessary to safeguard the UK’s sugar beet industry and farmers’ livelihoods.

Environmental charities, however, are urging the government to enforce and extend the ban on neonicotinoids to protect ecosystems and public health. They are also calling for improved river monitoring by the Environment Agency, which currently tests only a small proportion of the country’s waterways.

Dr. Richard Gill, a principal researcher at Imperial College London, highlighted the broader dangers of neonicotinoids.

While high concentrations can kill bees outright, even smaller doses have cumulative, sub-lethal effects. These include impairing bees’ ability to fly, gather pollen, and sustain their colonies. The chemicals may also alter bees’ genes, compounding their decline.

The issue comes amidst a backdrop of declining bee populations across the UK. Dr. Gill attributed this decline to multiple factors, including urbanisation, agricultural land-use changes, climate change, emerging pathogens, and pesticide use.

“It is concerning that we’re finding these pesticides in the rivers,” Dr Gill said, adding it was important to monitor the concentration of the chemicals in the waterways.

The presence of neonicotinoids in rivers further complicates the crisis, as these chemicals also harm aquatic ecosystems and river insects, which are vital for biodiversity.

Amy Fairman of the River Action campaign group emphasised that agricultural pollution, including pesticide runoff, now contributes more to water contamination in the UK than sewage.

“River insects are right at the bottom of the food chain,” she said. “If we’re destroying the bottom of the food chain in our rivers, this is going to have a knock-on effect.”

She also warned that neonicotinoids pose risks to human health, advising those considering swimming in rivers to educate themselves about potential contamination.

She suggested people considering swimming in polluted rivers should “understand the levels of contamination” and “educate” themselves about the risks before entering the water.

While the charities’ findings are based on a limited dataset, the analysis suggests a slight increase in neonicotinoid levels compared to previous years.

The Rivers Trust and Wildlife and Countryside Link are pressing for more comprehensive and consistent river monitoring to better understand the scale of the problem and address the ongoing threats to ecosystems and pollinators.