14-05-2025
The antibiotics we take are entering our rivers and helping breed resistance
You take an antibiotic. A few days later, you feel better and move on. But the medicine doesn't just enter your body and completely disappear. It passes through your body and enters the environment. Some antibiotics end up in rivers, where they alter microbial life. Given that microbes are everywhere, including inside us, this eventually affects us.
A startling new study published in PNAS Nexus lays this out in global detail. Each year, over 8,500 tonnes of antibiotics consumed by humans are flushed into rivers worldwide. And this number is only from medical use. It does not include antibiotics dumped by pharmaceutical factories or those used in farms to fatten animals. These are well-known sources of environmental contamination, which I discussed in detail in When the Drugs Don't Work: The Hidden Pandemic That Could End Modern Medicine.
In the new study, researchers from McGill University used computer models to trace how the 40 most-used antibiotics move through wastewater systems and surface waters. They found that even with sewage treatment, large quantities of these drugs escape into the environment. When rivers run low, for example, under low-flow conditions during hot, dry months, residues concentrate to dangerous levels across six million kilometers of waterways.
It should not surprise anyone familiar with antibiotic resistance that India ranks near the top. We already knew India is one of the world's highest consumers of antibiotics. Now, the new paper estimates that 87 percent of our rivers have antibiotic levels above safe limits, affecting 677,000 kilometers of waterways.
Many Indian cities don't treat all their sewage. In smaller towns and rural areas, most waste flows untreated into open drains, streams, or lakes. Even where treatment plants exist, they rarely remove drug residues completely. Antibiotics like amoxicillin (71 percent of which is excreted unchanged), cefixime (100 percent excreted), and ceftriaxone are routinely prescribed in India. All are now being detected in rivers. Cefixime alone contaminates more than 80 percent of India's affected rivers.
Once antibiotics enter the environment, they do not just float passively. They keep exerting pressure. Antibiotics do not kill all bacteria outright. In rivers, where countless microbes live and interact, low concentrations act as a filter. Susceptible bacteria are eliminated. Resistant strains survive and pass on to their genes, both to their offspring and to other bacteria. The process is invisible, but bacteria reproduce fast, and resistance spreads quickly.
Also Read: 13-year-long study finds resistance for last-resort antibiotics
In When the Drugs Don't Work, I wrote that resistance does not only emerge in people. It begins in the environment, in river sediment, in sewage bacteria, in the microbial sludge of drains. Once superbugs take hold, they can reach humans through contaminated water, food, poor hygiene, or hospital surfaces.
The study estimates that 750 million people live within 10 kilometers of rivers with the highest levels of antibiotic contamination. In India alone, the study estimates 315 million people live near the most contaminated rivers.
The researchers calculate that someone drinking two liters a day from our most polluted rivers could consume enough antibiotics to exceed safe health limits. Even low-level, chronic exposure can disrupt the gut microbiome and raise the risk that resistant bacteria take hold silently.
The researchers compared their model with real-world measurements from 877 sites. In some Indian and Pakistani rivers, they found over ten different antibiotics, each one exceeding safe levels. If all sources were included, the risk would be even higher.
And this is only the tip of the iceberg. This paper included only human antibiotic use. It left out veterinary antibiotics, which exceed human consumption, as well as aquaculture and pharmaceutical waste.
We have already seen resistance spread through water. In well-documented studies over the past fifteen years, researchers have found deadly superbugs in rivers and in water from drains and public taps in major Indian cities, including in New Delhi. The link between resistance and environmental contamination is real. It is growing. It is underappreciated.
This new study should be a wake-up call. The antibiotics that treat us do not just vanish. Unless we rethink how we use, dispose, and treat them, we will continue to drown in antibiotics.
Anirban Mahapatra is a scientist and author, most recently of the popular science book, When The Drugs Don't Work: The Hidden Pandemic That Could End Medicine. The views expressed are personal.
