Concentrations of antibiotics found in some of the world’s rivers exceed ‘safe’ levels by up to 300 times, the first ever global study has discovered.

Researchers looked for 14 commonly used antibiotics in rivers in 72 countries across six continents and found antibiotics at 65% of the sites monitored.

Metronidazole, which is used to treat bacterial infections including skin and mouth infections, exceeded safe levels by the biggest margin, with concentrations at one site in Bangladesh 300 times greater than the ‘safe’ level.

In the River Thames and one of its tributaries in London, the researchers detected a maximum total antibiotic concentration of 233 nanograms per litre (ng/l), whereas in Bangladesh the concentration was 170 times higher.

The most prevalent antibiotic was trimethoprim, which was detected at 307 of the 711 sites tested and is primarily used to treat urinary tract infections.

The research team compared the monitoring data with ‘safe’ levels recently established by the AMR Industry Alliance which, depending on the antibiotic, range from 20-32,000 ng/l.

Read more at University of York