According to a recent study, the concentration of active pharmaceutical ingredients (APIs) in rivers globally "pose a threat to environmental and human health."

Pharmaceuticals and other biologically active substances used by people are known to harm animals, and antibiotics in the environment increase the chance of drug resistance, one of humanity's biggest concerns.

The scientists measured the concentration of 61 active pharmaceutical ingredients (APIs) at more than 1,000 sites along 258 rivers and in 104 countries, covering all continents.

Only Iceland and a Venezuelan town where indigenous people do not utilize modern medications were unpolluted.

The most often found APIs were carbamazepine, an anti-epileptic medicine that is difficult to break down, metformin, a diabetic medication, and caffeine.

Antibiotics were identified at unsafe levels in one out of every five locations, and many sites contained at least one API at levels deemed toxic for animals, including impacts such as the feminization of fish.

APIs end up in rivers after being consumed by humans and cattle and excreted into the sewage system or directly into the environment, while some may also leak from pharmaceutical plants.

API levels were extremely high in Lahore, Pakistan, La Paz, Bolivia, and Addis Abeba, Ethiopia.

Madrid, Spain, was in the top 10 percent of places with the greatest cumulative concentrations, while Glasgow, UK, and Dallas, US, were in the top 20 percent.

"The World Health Organization and UN and other organizations say antimicrobial resistance is the single greatest threat to humanity – it's a next pandemic," said John Wilkinson, at the University of York, in the UK, and who led the study, which involved 127 researchers from 86 institutions.

The Kai Tak River in Hong Kong had the most APIs in a single location, with 34 separate APIs.

The greatest drug concentrations were discovered in low-to-middle income nations such as India and Nigeria.

According to a study published in January, 5 million individuals died in 2019 from antibiotic-resistant bacterial illnesses.

The study's locations with the most antibiotic-resistant damage closely correlate with those with the most drug pollution, indicating that river contamination may be a factor in driving up resistance.

One location in Bangladesh found metronidazole levels more than 300 times higher than the acceptable limit, presumably due to leakage from pharmaceutical manufacture.

Metronidazole levels were discovered to be more than 300 times higher than the legal limit in one place in Bangladesh, likely owing to leakage from pharmaceutical manufacturing.

The study did not include measurements of illegal drugs such as cocaine and MDMA, which have been detected in rivers at levels harmful to wildlife, although future analysis of the samples may do this.

Wilkinson said, "good sewage connectivity and wastewater treatment is the key to minimizing, though not necessarily eliminating, pharmaceutical concentrations."

Another method to minimize pollution, he says, is to use drugs more cautiously, particularly antibiotics, which are widely available without prescription in many countries and are commonly used needlessly, for example, to treat colds.

Prof Joakim Larsson, of the University of Gothenburg, Sweden, who was not part of the study researchers said pharmaceuticals "are almost omnipresent in rivers across the world."

“The study shows that a fairly large set of pharmaceuticals exceed ‘safe levels’, and often at a very large number of sites. Bacteria do not respect national borders, so if a new resistant bacterium develops on one side of our planet, it soon becomes a risk for everyone.”