One site in Bangladesh had concentrations 300 times what is considered safe.

(University of York)

At a Glance

More than 700 rivers were tested in 72 countries. Sixty-five percent of the rivers tested had unsafe concentrations of antibiotics.

Hundreds of the world's rivers are polluted with unsafe concentrations of antibiotics which may contribute to a rise in drug-resistant diseases that are expected to kill 10 million people by 2050, a new study says.

Researchers with the U.K.'s University of York tested for 14 commonly used antibiotics in more than 700 rivers in 72 countries. They found that 65 percent of the rivers had concentrations that One river in Bangladesh had concentrations 300 times what is considered safe, according to a press release.

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

“The results are quite eye opening and worrying, demonstrating the widespread contamination of river systems around the world with antibiotic compounds," Alistair Boxall of the York Environmental Sustainability Institute said in the press release.

Ciprofloxacin, used to treat a number of bacterial infections, was the antibiotic that most frequently exceeded safe levels, surpassing the safety threshold in 51 places.

The safe threshold is between 20-32,000 nanograms per liter (ng/l) depending on the compound and was established by the AMR Industry Alliance, a coalition of biotech, diagnostics and pharmaceutical companies working to curb antimicrobial resistance.

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Asia and Africa had the most river sites polluted with antibiotics and the rivers where antibiotics exceeded ‘safe’ levels by the greatest degree were in Bangladesh, Kenya, Ghana, Pakistan and Nigeria.

The researchers noted that rivers in Europe, North America and South America were also polluted, making this a "global problem."

The concentrations of antibiotics that make their way into rivers via human or animal waste were highest near wastewater treatment facilities or waste and sewage dumps.

In April, the calling resistance to antibiotics, antivirals, antifungals and antiprotozoals a “global crisis.”

According to the report by the UN's Interagency Coordination Group on Antimicrobial Resistance, more than 700,000 people die each year from drug-resistant diseases, including 230,000 deaths from multi-drug-resistant tuberculosis. The agency added that drug-resistant diseases could kill 10 million by 2050.

"There is no time to wait. Unless the world acts urgently, antimicrobial resistance will have disastrous impact within a generation," the authors wrote.

Boxall noted that many scientists and policy makers believe contamination of rivers could be an "important contributor" to the rise in drug-resistant diseases.

“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," Boxall said.