Toxic cocktail of chemicals and drugs including antidepressants polluting UK rivers

A cocktail of chemicals, caffeine andincluding antidepressants and painkillers are the UK’s rivers, new analysis has found.

The alarming presence of these substances, which enter into waterways as a result of released from water firms, can pose a risk to aquatic life, warn experts. In addition, 61% of fresh waters in the UK are in a poor state because of high levels of the nutrients phosphate and nitrate, the source of which is sewage effluent and agricultural runoff.

Results from three days of testing in rivers by 4,531 volunteers for the research group Earthwatch found England had the worst level of poor water quality in rivers, with 67% of freshwater samples showing high levels of nitrate and phosphate.

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The Anglia and Thames river basin districts have the worst water quality in the UK with over 80% of surveys showing unacceptable nutrient concentrations. The county of Northumberland has the best water quality, whereas Rutland has the worst water quality in the UK.

Director of Science and Policy at Earthwatch Europe, Dr Sasha Woods, said the results were “deeply concerning” and “shows the alarming extent of pollution in UK rivers with no region left untouched”.

She added: “Our rivers are facing a multitude of threats, including sewage pollution to agricultural runoff and we need urgent action to protect these vital ecosystems. Otherwise we risk greater losses to freshwater biodiversity, the potential spread of antimicrobial resistance, and the very real threat of clean water scarcity. Healthy freshwater systems, free from harmful pollution aren’t a nice thing to have, they are vital if we are to address the biodiversity and climate crises.”

Earthwatch volunteers tested rivers over three days in September, gathering 2,338 datasets which were tested for high levels of phosphates and nitrates. 91 samples were sent for further testing for the presence of chemicals by Imperial College London. It found a concerning presence of antidepressants , antibiotics and painkillers (tramadol and diclofenac), as well as nicotine and caffeine.

Of the 91 samples, 100% contained caffeine, with levels in 80% of these samples presenting some risk to aquatic life. Nicotine was found in 25% of samples, with concentrations that present some risk to aquatic life found in 7% of samples. The antidepressant venlafaxine was found in 30% of samples analysed, with 13% of samples containing levels that posed a risk to aquatic life.

Dr Woods said the main source of this pollution is sewage from water company treatment works. Earthwatch warns that many of these substances pose a significant risk to aquatic organisms. Antidepressants have been shown to affect reproductive cycles and motility. Nicotine has been demonstrated to be more harmful to fish than to aquatic insects, and the presence of antibiotics in freshwater bodies is known to contribute to Antimicrobial Resistance - a phenomenon where microorganisms no longer respond to available antimicrobial drugs. The full extent of the impact is still being researched.

Dr Leon Barron, Reader in Analytical & Environmental Sciences within the School of Public Health at Imperial College London, said: “Our analysis has already identified several chemicals at levels which exceed accepted safe limits for aquatic life. We found pharmaceuticals, pesticides and even common substances like caffeine and nicotine at detectable levels in water up and down the country.

“What this work highlights is that despite treatment facilities being in place, these chemicals continuously find their way into our waterways. Rivers are still the lifeline of the UK, and that none pass good overall health status represents a national failure. More needs to be done to urgently clean up our water.”

The full analysis of about 300 chemicals will be published in a peer-reviewed journal in 2025. Initial results are already building a more complete picture of chemicals in rivers and lakes. Regular testing is key and there are already two further citizen science Great UK WaterBlitz weekends planned for 2025. People can register their interest to join on .