Antibiotics pollute many of the world’s rivers | Science News for Students

Antibiotics pollute many of the world’s rivers

The new findings suggest a growing risk that drug-resistant germs will develop throughout the environment
Jul 2, 2019 — 6:45 am EST
a photo of the Odaw River

A new survey finds antibiotics in about two-thirds of 711 river sites tested. They include the Odaw River, shown, running through Ghana’s capital of Accra.

Rob Marchant

Antibiotics taint two out of every three rivers sampled as part of a big new survey. Scientists made the finding while testing water from 165 rivers across 72 countries. Many of most polluted sites were in Asia and Africa. Until now, there had been little testing in these areas for drugs in water.

The new data are a big concern. Bacteria that can’t be killed by antibiotics pose a large and growing threat to health. Doctors call these bacteria “superbugs.” As microbes encounter drugs in the environment, many will evolve changes. Called mutations, some of these may allow the germs to survive the drugs. Later, people infected with those microbes may find themselves at risk of life-threatening disease.

It doesn’t matter that some of these pollution problems are occurring in far-off sites around the world. People should still be as concerned about resistance evolving in these places as they are about it developing in their own backyards, says William Gaze. He’s a microbial ecologist in England who works at the University of Exeter Medical School. Even if wealthy countries wipe out antibiotic pollution, drug-resistant microbes can hitch a ride to those countries. They can arrive with sick travelers. They might move around the world in migrating birds. They might even arrive in imports of animal-based foods, says Gaze. “It’s a global problem,” says this scientist, who was not involved with the new survey. That’s why, he adds, “We need global solutions.”

Alistair Boxall and John Wilkinson work in England at the University of York. Together, they tested water from 711 sites.  And 470 of them contained at least one antibiotic.

About one in every seven of the sites tested — 111 in all — contained unsafe levels of the drugs. That judgment is based on guidelines by the AMR Industry Alliance. It’s a global group of biotech and drug companies. It has set safety thresholds. And those are based on data showing what levels of a drug would neither kill algae nor promote drug resistance in bacteria.

“I don’t think I was expecting the degree of [high] concentrations that we saw,” says Boxall, who is an environmental chemist. “That was quite eye-opening.”

He and Wilkinson shared their findings in a pair of papers presented on May 27 and May 28. They spoke in Helsinki, Finland at a meeting of the Society of Environmental Toxicology and Chemistry.

More wide-ranging survey than ever before

No survey of drugs in water has ever been carried out on this scale, Boxall says. Earlier ones had focused on rivers in North America, Europe and China. In contrast, he and Wilkinson sent water-collection kits to colleagues all over the world. Then they tested the water they got back for 61 drugs. These included 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 with unsafe levels of the drugs contained more than one antibiotic. The most commonly found one was trimethoprim (Try-METH-oh-prim). It’s used to treat urinary-tract infections. And it showed up at more than four out of every 10 sites sampled. Other commonly found antibiotics were sulfamethoxazole (Sul-fa-meh-THOX-uh-zole), ciprofloxacin (Cih-pro-FLOX-uh-sin) and metronidazole (Meh-troh-NY-duh-zole).

The Kirtankhola River, near the south-central city of Barisal, Bangladesh, contained the highest antibiotic level of any site. Metronidazole levels there approached 40,000 nanograms per liter. That’s roughly 300 times what is considered safe. And the level of ciprofloxacin there was eight times what is deemed safe.

High antibiotic levels also showed up in several African rivers. These included ones in   Accra, the capital of Ghana; near Kenya’s capital city of Nairobi; and near Lagos, Nigeria’s biggest city. High levels also showed up in Lahore, the second-most populated city in Pakistan, and in a river near the Israeli city Nablus.

The highest level of antibiotics in Europe turned up in an urban tributary of the Danube as this river travels through Austria. The most polluted U.S. river was in North Liberty, Iowa, near many livestock farms.

The researchers did some detective work to figure out how the drugs were getting into these water. Google Street View showed some tainted waters were near plants that make medicines. Perhaps they released drug-making wastes into local waters, the researchers say. Photos from several very polluted sites in Africa and Asia, Boxall notes, also showed trash heaped along riverbanks and sewage-carrying trucks.

How deep a river is, how fast it flows and whether a sampling site was downstream of a city or hospital can also affect levels of any drugs found, Boxall says.

He, Wilkinson and their colleagues plan to test how levels of the drugs measured at some sites might affect algae and other organisms. They hope such findings can help officials across the globe take needed action to cut drug pollution.

Power Words

(more about Power Words)

algae     Single-celled organisms, once considered plants (they aren’t). As aquatic organisms, they grow in water. Like green plants, they depend on sunlight to make their food.

antibiotic     A germ-killing substance, usually prescribed as a medicine (or sometimes as a feed additive to promote the growth of livestock). It does not work against viruses.

bacteria     (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals). Bacteria are one of the three domains of life on Earth.

biotech     Short for biotechnology, which is the use of living cells to make useful things.

chemistry     The field of science that deals with the composition, structure and properties of substances and how they interact. Scientists use this knowledge to study unfamiliar substances, to reproduce large quantities of useful substances or to design and create new and useful substances.

colleague     Someone who works with another; a co-worker or team member.

concentration     (in chemistry) A measurement of how much of one substance has been dissolved into another.

downstream     Further on in the direction in which a stream is flowing or the path at which stream water will flow in its trek to towards the oceans.

ecology      A branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.

environment     The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).

evolve     (adj. evolving) To change gradually over generations, or a long period of time. In living organisms, such an evolution usually involves random changes to genes that will then be passed along to an individual’s offspring. These can lead to new traits, such as altered coloration, new susceptibility to disease or protection from it, or different shaped features (such as legs, antennae, toes or internal organs).

germ     Any one-celled microorganism, such as a bacterium or fungal species, or a virus particle. Some germs cause disease. Others can promote the health of more complex organisms, including birds and mammals. The health effects of most germs, however, remain unknown.

infection     A disease that can spread from one organism to another. It’s usually caused by some type of germ.

livestock     Animals raised for meat or dairy products, including cattle, sheep, goats, pigs, chickens and geese.

microbe     Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.

mutation     (v. mutate) Some change that occurs to a gene in an organism’s DNA. Some mutations occur naturally. Others can be triggered by outside factors, such as pollution, radiation, medicines or something in the diet. A gene with this change is referred to as a mutant.

organism     Any living thing, from elephants and plants to bacteria and other types of single-celled life.

resistance     (as in drug resistance) The reduction in the effectiveness of a drug to cure a disease, usually a microbial infection.

risk     The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

sewage     Wastes — primarily urine and feces — that are mixed with water and flushed away from homes through a system of pipes for disposal in the environment (sometimes after being treated in a big water-treatment plant).

society     An integrated group of people or animals that generally cooperate and support one another for the greater good of them all.

superbug     A popular term for a disease-causing germ that can withstand medicines.

survey     To view, examine, measure or evaluate something, often land or broad aspects of a landscape.

taint     To contaminate something with an unexpected, unnatural or illegal substance.

threshold     A lower limit; or the lowest level at which something occurs.

toxicology     The branch of science that probes poisons and how they disrupt the health of people and other organisms. Scientists who work in this field are called toxicologists .

tract     A particular, well-defined area. It can be a patch of land, such as the area on which a house is located. Or it can be a bit of real estate in the body. For instance, important parts of an animal’s body will include its respiratory tract (lungs and airways), reproductive tract (gonads and hormone systems important to reproduction) and gastro-intestinal tract (the stomach and intestines — or organs responsible for moving food, digesting it, absorbing it and eliminating wastes).

urban     Of or related to cities, especially densely populated ones or regions where lots of traffic and industrial activity occurs. The development or buildup of urban areas is a phenomenon known as urbanization.

waste     Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.


Journal: A. Boxall and J. Wilkinson. Identifying hotspots of resistance selection from antibiotic exposure in urban environments around the world. SETAC Europe 29th Annual Meeting, Helsinki, Finland. May 27, 2019.

Journal: J. Wilkinson and A. Boxall. The first global study of pharmaceutical contamination in riverine environments. SETAC Europe 29th Annual Meeting, Helsinki, Finland. May 28, 2019.