Potentially toxic levels of pharmaceutical drugs have been found in a quarter of river sites surveyed across the world, a study has found.
Researchers around the world have studied more than 1,000 sites on 258 rivers, including the Thames in London and other UK waterways.
The Amazon River in Brazil was also included in the study along with rivers in major cities such as Delhi, New York and Guangzhou.
The assessment measured the presence of 61 pharmaceuticals, including some compounds also linked to lifestyles such as caffeine, 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 the pollution of the world’s rivers by medicinal chemicals is a global problem.
Pollution poses a risk to freshwater habitats and wildlife and potentially contributes to the build-up of antimicrobial resistance.
It also threatens global goals for water quality and pollution, the research warns.
Beta blockers, antibiotics and antidepressants found
The analysis, carried out at the University of York, revealed pharmaceutical pollution in rivers on every continent, with nicotine and cotinine, caffeine and paracetamol everywhere, including Antarctica.
An array of chemicals such as beta-blockers, antibiotics, antidepressants, sleeping pills and antihistamines have been found in rivers on every inhabited continent.
While most chemicals seen in rivers globally are below concentrations that could have ecological effects, there were levels of contaminants that could pose a threat to the environment or human health in more than a quarter of the places studied.
And some rivers are exposed to complex mixtures of chemicals.
Contaminants found in potentially harmful concentrations at some sites included the beta-blocker propranolol and the antibiotic ciprofloxacin.
For the study, water samples were taken from sites ranging from a village in Venezuela, where modern drugs are not used, to cities ranging from Lagos to Las Vegas, as well as areas of instability. politics such as Baghdad and the Palestinian West Bank.
Read more: ‘Chemical cocktail’ – Sewage, slurry and plastic are flowing in English rivers, say MPs
The research found that low- and middle-income countries were the most polluted, while garbage dumping along river banks, poor sewage treatment infrastructure, and pharmaceutical manufacturing and content dumping septic tanks in rivers were the activities most associated with the problem.
The most polluted countries and regions of the world are those, such as sub-Saharan Africa, South America and parts of South Asia, which have been least studied.
The most contaminated river in the UK
In the UK, the study looked at 54 sampling sites across 12 rivers and detected pharmaceuticals at all but four sites in Snowdonia, Wales.
The most contaminated site in the UK was the River Clyde in Glasgow, but concentrations in UK rivers more generally matched European sites.
Project co-lead Dr John Wilkinson, University of York, said: “We have known for more than two decades now that pharmaceuticals enter the aquatic environment where they can affect the biology of living organisms. .
“But one of the biggest problems we’ve faced in solving this problem is that we haven’t been very representative when monitoring these contaminants, with almost all of the data concentrated in a few select areas in America. Northern, Western Europe and China.
“Thanks to our project, our knowledge of the global distribution of pharmaceuticals in the aquatic environment has improved considerably.”
Global, inclusive and interconnected efforts must be made to generate the monitoring data needed to make decisions about how to reduce the environmental impacts of chemicals, the researchers said.