By Abdullahi Lukman
An estimated 8,500 tons of antibiotics—about one-third of all antibiotics consumed by humans annually—are making their way into the world’s rivers, even after passing through wastewater treatment systems, according to a new global study published in PNAS Nexus.
Researchers warn that this widespread contamination poses serious risks to aquatic ecosystems and contributes to the growing threat of antibiotic resistance.
“Even at chronic, low concentrations, antibiotics in natural waters reduce microbial diversity, increase resistance genes, and can harm fish and algae,” the study’s authors noted.
The research, led by McGill University postdoctoral fellow Heloisa Ehalt Macedo, is the first to estimate the global scale of antibiotic pollution in river systems stemming solely from human use.
Using data from nearly 900 rivers, the team built and validated a global model that highlights regional hot spots, particularly in Southeast Asia, where high antibiotic use and limited wastewater treatment intersect.
Amoxicillin—the world’s most commonly used antibiotic—was identified as the compound most likely to reach harmful concentrations in these vulnerable areas.
“While individual concentrations are often small and hard to detect, the cumulative exposure over time can pose significant ecological and health risks,” Macedo said in a press release.
The study explicitly excluded contributions from pharmaceutical manufacturing and animal agriculture, suggesting that the actual scale of river antibiotic pollution is even greater.
“Human use alone is causing a critical level of contamination. Adding in veterinary and industrial sources would likely worsen the situation,” said Jim Nicell, co-author and professor of environmental engineering at McGill.
Co-author Bernhard Lehner emphasized that the study isn’t a warning against antibiotic use but a call for responsible management.
“Antibiotics are essential for human health, but we must recognize and mitigate their unintended environmental consequences,” he said.
The researchers are calling for expanded global monitoring programs and targeted mitigation strategies, especially in high-risk regions, to reduce the ecological footprint of antibiotic pollution in freshwater systems.
