Millions of miles (kilometers) of rivers worldwide contain antibiotic pollution levels high enough to promote drug resistance and harm aquatic life, according to a study led by McGill University.
Published in
PNAS Nexus, this study is the first to estimate the global scale of river contamination from human antibiotic use. Researchers calculated that approximately 8,500 tons of antibiotics - nearly one-third of annual human consumption - end up in global river networks each year, often even after wastewater treatment.
"Even though individual antibiotic residues occur at very low concentrations in most waterways, making them extremely difficult to detect, chronic and cumulative exposure to these substances in the environment may nevertheless pose risks to human health and aquatic ecosystems," explains Heloisa Ehalt Macedo, a postdoctoral fellow in geography at McGill University and the study's lead author.
The research team used a global model validated by field data from nearly 900 river sites. They found that amoxicillin, the world's most widely used antibiotic, was also most likely to be present at risky concentrations, particularly in Southeast Asia where increasing usage and limited wastewater treatment exacerbate the problem.
"This study isn't a warning against antibiotic use, which remains essential for global health, but our findings indicate their presence in waterways could have adverse effects on aquatic environments and antibiotic resistance, requiring mitigation strategies and risk management," notes Bernhard Lehner, professor of global hydrology in McGill's Department of Geography and study co-author.
These findings are particularly significant as the study didn't account for antibiotics from livestock or pharmaceutical plants - two major sources of environmental contamination.
"Our results show that river pollution from human antibiotic consumption alone is a major issue, likely worsened by veterinary or industrial sources of related compounds," says Jim Nicell, professor of environmental engineering at McGill and study co-author. "We urgently need monitoring programs to detect antibiotic or other chemical contamination in waterways, especially in areas our model predicts as vulnerable."
The study "Antibiotics in the global river system arising from human consumption" by Heloisa Ehalt Macedo, Bernhard Lehner, Jim Nicell, Usman Khan and Eili Klein was published in
PNAS Nexus.
The research was funded by Canada's Natural Sciences and Engineering Research Council along with a James McGill Chair and Fessenden Professorship in Science and Innovation at McGill University.