Hundreds of the world’s rivers are awash with “dangerous levels of antibiotics,” the largest global study on the subject has found.
The study, which examined the levels of 14 commonly used antibiotics at 711 sites in 72 countries, found that 65 percent of those sites are contaminated with the drugs.
The findings come as the United Nations in April declared antibiotic resistance a global health emergency that could kill 10 million people by 2050.
Speaking at the Helsinki conference, Alistair Boxall, co-leader of the study and environmental scientist, told The Guardian: “It’s quite scary and depressing. We could have large parts of the environment that have got antibiotics at levels high enough to affect resistance.”
Experts fear the levels of the drugs in rivers could contribute to a rise in bacteria that’s resistant to treatment by antibiotics, which means they can no longer be used in medicines for humans.
Professor William Gaze, a microbial ecologist at the University of Exeter who was not involved in the study, told The Guardian, “A lot of the resistance genes we see in human pathogens originated from environmental bacteria.”
The antibiotics enter rivers and soil via human and animal waste, as well as leaks from drug manufacturing sources and wastewater treatment plants.
The research, which was put together by a global team of scientists led by the University of York, found 35 percent of river sites in Africa and 23 percent in Asia exceeded safe limits for concentrations of antibiotics.
In Kenya, one site contained levels of antibiotics more than 100 times the safe level, with some areas so concentrated no fish could survive, researchers said.
Higher levels of antibiotics were found in the rivers of lower-income countries, the study found.
Metronidazole, which is used to treat vaginal infections, was discovered in Bangladesh at more than 300 times the safe level, with residues of the drug discovered near a wastewater treatment plant.
Lack of access to technology to dispose of the drugs in lower-income countries is likely to contribute to the higher levels of contamination, The Guardian reported.
Meanwhile, 15 percent of river sites tested in North America and 18 percent of river sites in South America contained dangerous levels of the drugs. Eight percent of sites in Europe exceeded safe limits, the study found.
Even if relatively low levels of the drugs are found in rivers, it could still increase the likelihood of the development and spread of antibiotic resistance, researchers said.
“Even the low concentrations seen in Europe can drive the evolution of resistance and increase the likelihood that resistance genes transfer to human pathogens,” Gaze told The Guardian.
“The results are quite eye-opening and worrying, demonstrating the widespread contamination of river systems around the world with antibiotic compounds,” Boxall said.
“Many scientists and policymakers now recognize the role of the natural environment in the antimicrobial resistance problem. Our data show that antibiotic contamination of rivers could be an important contributor,” he added.
“Solving the problem is going to be a mammoth challenge and will need investment in infrastructure for waste and wastewater treatment, tighter regulation, and the cleaning up of already contaminated sites.”
