Washington: Stressing that antibiotic contamination is a global problem, researchers at the University of York have claimed that the concentration of antibiotics in some of the world’s rivers has crossed 'safe' levels by up to 300 times.
According to the study presented at a conference of the Society of Environmental Toxicology and Chemistry, the researchers looked for 14 commonly used antibiotics in rivers in 72 countries across six continents and found antibiotics at 65 per cent of the sites monitored.
The team said that the 'safe' limits most frequently exceeded in Asia and Africa, but sites in Europe, North America and South America also had levels of concern showing that antibiotic contamination was a 'global problem'.
Sites, where antibiotics exceeded 'safe' levels by the greatest degree were in Bangladesh, Kenya, Ghana, Pakistan and Nigeria, while a site in Austria was ranked the highest of the European sites monitored.
Dr John Wilkinson, from the University of York, who co-ordinated the monitoring work said, "Until now, the majority of environmental monitoring work for antibiotics has been done in Europe, N America and China. The studies have been done only on a handful of antibiotics. We know very little about the scale of the problem globally. Our study helps fill this key knowledge gap with data being generated for countries that had never been monitored before."
Professor Alistair Boxall, University of York, said, "The results are eye-opening and worrying, demonstrating the widespread contamination of river systems around the world with antibiotic compounds."
According to the study, 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, primarily used to treat urinary tract infections, which was detected at 307 sites of the 711 sites tested. Another antibiotic Ciprofloxacin, which is used to treat a number of bacterial infections, most frequently exceeded safe levels, surpassing the safety threshold in 51 places.
The study revealed that high-risk sites were typically adjacent to wastewater treatment systems, waste or sewage dumps and in some areas of political turmoil, including the Israeli and Palestinian border.
