Antibiotics are lifesavers. But after we use them, they don’t just disappear—they often end up in rivers, lakes, and streams around the world. And according to a new study led by researchers at McGill University, the scale of this pollution is far greater than we realized.
Published in PNAS Nexus, the study estimates that about 8,500 tons of human-used antibiotics—roughly one-third of global consumption—leak into rivers every year. Even after passing through wastewater treatment systems, a significant amount still makes its way into the environment, where it can promote antibiotic resistance and damage aquatic ecosystems.
“While the amounts of residues from individual antibiotics translate into only very small concentrations in most rivers, which makes them very difficult to detect, the chronic and cumulative environmental exposure to these substances can still pose a risk to human health and aquatic ecosystems,” said author Heloisa Ehalt Macedo..
A Global Model, Grounded in Real Data
The McGill-led team built a global model and validated it with field data from nearly 900 river sites worldwide. Their findings show that antibiotic pollution is a global issue, but some areas—particularly Southeast Asia—are more at risk due to high antibiotic use and limited wastewater infrastructure.
The study identifies amoxicillin—one of the most commonly used antibiotics worldwide—as the most likely to reach risky levels in rivers. That’s a concern because low, persistent concentrations of antibiotics can drive bacteria to develop resistance, turning once-treatable infections into hard-to-fight superbugs.
Why It Matters
First, a reality check: This is not an anti-antibiotics message.
“This study is not intended to warn about the use of antibiotics—we need antibiotics for global health treatments,” said Bernhard Lehner, the study’s co-author.
It’s about understanding the environmental ripple effects of our medical choices and developing smarter systems of usage and management.
The Hidden Sources We Didn’t Even Count
Perhaps most alarming is that the study did not account for antibiotics from factory farming or pharmaceutical manufacturing—two major contributors to environmental pollution. Therefore, the real numbers are likely even worse.
So What Can Be Done?
The researchers stress the need for monitoring programs that test for antibiotics in waterways, especially in regions flagged as high risk by their model. Right now, many countries lack the infrastructure or policy guidance to keep tabs on pharmaceutical pollution.
This research also highlights the importance of investing in better wastewater treatment technologies, particularly in fast-growing urban areas. Existing systems often aren’t designed to filter out complex chemical compounds like antibiotics, which means they pass right through and into our rivers.
The Bottom Line
Antibiotics remain one of modern medicine’s most powerful tools—but what happens to them after they leave our bodies and how we use them matters, too. This study doesn’t tell us to stop using them. It tells us to start paying attention to where they go and responsibility of use.
Because while rivers may look clean on the surface, their invisible contents could be shaping the future of global health in ways we can’t afford to ignore.
HE Macedo et al. Antibiotics in the global river system arising from human consumption. PNAS Nexus (2025). DOI: 10.1093/pnasnexus/pgaf096
