Nearly a third of all antibiotics that people consume end up in the world’s rivers, a new studyfinds. This could potentially harm aquatic life and impact human health by promoting drug resistance, researchers say.
Antibiotics, critical for treating various bacterial infections, are widely consumed by people, livestock and aquaculture fish, but the drugs are only partially absorbed by the body. Much is excreted, entering the environment, especially water bodies.
Previous studiesestimating environmental antibiotic pollution at global scales have done so using field data from select rivers or have also included livestock and industrial sources.
The recent study focused solely on the contribution of human consumption to antibiotics in rivers and oceans, including in places where no field measurements exist. To do so, 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 researchers validated the model using field measurements 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, the model showed.
“This is concerning because antibiotics in water bodies can not only pose risks to aquatic ecosystems but also (and maybe more importantly) promote the development and spread of antimicrobial resistance, posing risks to human health,” study lead author Heloisa Ehalt Macedo, a postdoctoral fellow at McGill University, Canada, told Mongabay by email.
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, Macedo said, making their persistence “a truly global issue.”
Of the 40 antibiotics examined, the model predicted that amoxicillin, one of most widely used worldwide, was the most likely to be present at risky levels in rivers, especially in areas with inadequate wastewater treatment infrastructure, like parts of Southeast Asia.
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.
“Our results show that antibiotic pollution in rivers arising from human consumption alone is already a critical issue, which would likely be further exacerbated by veterinary and industrial sources of related compounds,” co-author Bernhard Lehner, a professor in global hydrology at McGill University, told Mongabay by email.
Macedo said their study isn’t a warning against antibiotic use. Rather, their findings point to the importance of implementing monitoring programs to detect antibiotic contamination in rivers and improve wastewater treatment systems, she added.
Banner image: Water flowing at a wastewater treatment facility in Manila. Image by Danilo Pinzon/World Bank via Flickr (CC BY-NC-ND 2.0).
