Science

Many of the worlds rivers are flush with dangerous levels of antibiotics

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In a massive survey of rivers across 72 countries, researchers found antibiotics at 66 percent of 711 sites sampled. Many of the most drug-polluted waterways were in Asia and Africa, where there hadnt been much data until now.

Environmental pollution from antibiotics is one driver of microbial drug resistance, which threatens public health. People should be as concerned about resistance evolving abroad as they are about resistance brewing in their own backyards, says William Gaze, a microbial ecologist at the University of Exeter Medical School in England who was not involved with the research. Even if wealthy countries curb antibiotic pollution, drug-resistant microbes can hitch a ride across the globe with traveling people, migrating birds or traded food and livestock, he says. “Its a global problem, and we need global solutions.”

About a third of the sites surveyed over the last year contained no detectable levels of antibiotics. But 66 percent, or 470 of the sites, tested positive for at least one of 14 types of antibiotics. And almost 16 percent, or 111 sites, contained concentrations considered unsafe, based on safety levels estimated by AMR Industry Alliance, a global biotech and pharmaceutical coalition. The alliance set its safety thresholds based on levels that wouldnt kill algae in the environment or promote resistance by killing susceptible bacteria.

“I dont think I was expecting the degree of concentrations that we saw. That was quite eye-opening,” says environmental chemist Alistair Boxall of the University of York in England, who conducted the survey with University of York colleague John Wilkinson. The two presented their results on May 27 and May 28 in Helsinki at a meeting of the Society of Environmental Toxicology and Chemistry.

The scale of the study is unprecedented, Boxall says. Previously, most surveys had focused on North America, Europe and China. So Boxall and Wilkinson sent water collection kits to colleagues all over the world and then tested samples from a total of 165 rivers for 61 drugs, including the 14 antibiotics.

Samples continue to roll in and the researchers plan to release more data in the future. “Ultimately, it would be nice if we could get samples from every country of the world,” Boxall says.

Many sites deemed to have unsafe antibiotic levels were contaminated with more than one of these drugs. The most commonly found antibiotic was trimethoprim, used to treat urinary tract infections, which showed up at 43 percent of the sampled sites. Other commonly occurring antibiotics were sulfamethoxazole, ciprofloxacin and metronidazole. Some of the antibiotics the researchers looked for — including oxytetracycline, amoxicillin and cloxacillin — were not detected at any site.

Samples from Bangladeshs Kirtankhola River, near the south-central city of Barisal, contained the highest antibiotic concentrations of any surveyed site. The level of metronidazole approached 40,000 nanograms per liter, or about 300 times the safe level. The commonly prescribed drug ciprofloxacin exceeded safe levels by a factor of eight.

High antibiotic concentrations were also foRead More – Source