A STUDY has found toxic levels of pharmaceuticals in rivers which "pose a threat to environmental and/or human health" in more than a quarter of studied locations, with the River Clyde the most polluted in the UK.
Conducted by the University of York, the study is among the most extensive of pharmaceutical contamination on a global scale.
Researchers from around the world sampled 1052 sites on 258 rivers – from the River Clyde in Glasgow and River Thames in London, to the Brazilian Amazon and rivers in major cities such as Delhi, New York and Guangzhou.
The study included 104 countries and spanned all continents, and claims "to represent the pharmaceutical fingerprint of 471.4 million people".
Rivers in Pakistan, Bolivia and Ethiopia were some of the most polluted. Rivers in Iceland, Norway and the Amazon rainforest fared the best.
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In the UK, the study looked at 54 sampling locations on 12 rivers, and detected pharmaceuticals in all but four sites in Snowdonia, Wales.
The most contaminated site in the UK was Glasgow's River Clyde, but concentrations in UK rivers were in line with European sites more generally.
The assessment measured the presence of 61 pharmaceuticals, including some "lifestyle consumables" such as caffeine and nicotine, and whether they were above levels where they could have an effect on the environment.
The study, published in the Proceedings of the National Academy of Sciences (PNAS), warns that pollution of the world's rivers by medicinal chemicals is a global problem.
The authors claim: "The presence of these contaminants in surface water poses a threat to environmental and/or human health in more than a quarter of the studied locations globally."
Pollution poses a risk to freshwater habitats and wildlife, and could potentially contribute to the build-up of antimicrobial resistance, and also threatens global goals on water quality and pollution.
The analysis found pharmaceutical pollution in rivers on every continent – with nicotine and cotinine, caffeine and paracetamol being detected everywhere, including Antarctica.
An array of chemicals such as beta blockers, antibiotics, antidepressants, sleeping medication and antihistamines were found in rivers on all inhabited continents.
Some rivers are exposed to complex mixtures of chemicals; contaminants found at potentially harmful concentrations at some sites included beta blocker propranolol and antibiotic ciprofloxacin.
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The research found rivers in lower and middle income countries were the most polluted, with rubbish dumping along river banks, inadequate waste water infrastructure and pharmaceutical manufacturing and dumping of septic tank contents into rivers contributing to the issue.
The most polluted countries and regions of the world are the ones, such as sub-Saharan Africa, South America and parts of southern Asia, that have been researched the least.
In Africa, artemisinin, which is used in anti-malarial medicine, was also found in high concentrations.
Co-leader of the project Dr John Wilkinson, from the University of York, said: "We've known for over two decades now that pharmaceuticals make their way into the aquatic environment where they may affect the biology of living organisms.
"But one of the largest problems we have faced in tackling this issue is that we have not been very representative when monitoring these contaminants, with almost all of the data focused on a select few areas in North America, western Europe and China.
"Through our project, our knowledge of the global distribution of pharmaceuticals in the aquatic environment has now been considerably enhanced."
There needs to be global, inclusive and interconnected efforts to generate monitoring data needed to make decisions on how to reduce the environmental impacts of chemicals, the researchers said.
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