Image description: A winding river through a dark landscape, with the sun in the centre of the sky. Image by Pixabay.

A new study finds nearly a third of all antibiotics that people consume, equivalent to 8,500 tonnes, end up in the world’s rivers every year.

Previous studies estimating environmental antibiotic pollution at global scales have done so using field data from select rivers or have also included livestock and industrial sources.

Instead, this new recent study focused solely on the contribution of human consumption to antibiotics in rivers and oceans, including in places where no field measurements exist.

The researchers used a model to simulate the pathway of the 40 most globally used antibiotics across the world’s river systems. The model used existing data on the antibiotics to track their journey, right from human consumption through excretion, transport and removal through wastewater systems, discharge into rivers, and eventual degradation in water bodies. The research team used a global model validated by field data from nearly 900 river locations. 

From 2012-2015, people consumed about 29,200 metric tons of the 40 most-used antibiotics each year, the researchers found. Nearly a third of those antibiotics, about 8,500 metric tons, were released into rivers globally and millions of kilometres of rivers around the world are carrying antibiotic pollution at levels high enough to promote drug resistance and harm aquatic life. The model also showed that 3,300 metric tons (11%) of antibiotic residues reached oceans or lakes. This indicates antibiotics can travel far from their original sources making their persistence “a truly global issue.”

They found that amoxicillin, the world’s most-used antibiotic, is the most likely to be present at risky levels, especially in Southeast Asia, where rising use and limited wastewater treatment amplify the problem.

The researchers caution actual antibiotic levels may be much higher in locations where other sources of antibiotics can enter the environment, such as near pharmaceutical industries or livestock production sites. Researchers clarified that while the study is not a warning against antibiotic use, their findings underscore the importance of implementing monitoring programs to detect antibiotic contamination in rivers and improve wastewater treatment systems.