Up to 90 Percent of Antibiotics Can End Up in Wastewater, Fueling Antimicrobial Resistance: Study

The journey of an antibiotic does not end when a patient swallows a pill.

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Most people may assume that once they take an antibiotic, the drug is broken down by the body and disappears.

But research from the University of Queensland in Australia and the University of Exeter in the UK says up to 90 percent of antibiotics taken by people make its way into wastewater systems, where they contribute to the growing concern of antimicrobial resistance (AMR).

The study, published in the Nature Water journal, found that antibiotic transformation products—chemical compounds formed when antibiotics break down—can drive antimicrobial resistance just as strongly as the original drugs, creating what researchers describe as a “hidden reservoir” of antibiotic activity in wastewater systems.

How Antibiotics End Up in Wastewater

According to lead researcher Pooja Lakhey from the University of Queensland, the answer lies in how the human body processes antibiotics.

“Our body is not that good at breaking down a lot of antibiotics that we take,” she told The Epoch Times in an interview.

“Because of this, a very large percentage of the antibiotics get passed unchanged, and then they get flushed right down the toilet.”

Lakhey explained that many antibiotics are water-soluble, allowing them to pass through the body and enter sewage systems through human waste, where they can stay dissolved and unchanged.

“So this in turn makes our wastewater system a massive, massive reservoir for these drugs.”

The study examined wastewater samples from Australia and the United Kingdom and found that antibiotic transformation products can continue exerting selective pressure on bacteria even after the original antibiotics have degraded.

Antimicrobial resistance occurs when bacteria evolve to survive medicines designed to kill them.

A Growing Global Health Challenge

The World Health Organisation (WHO) says AMR makes infections more difficult to treat, and increases the risks of medical procedures if the risk of infection cannot be effectively managed.

The WHO attributes AMR to the misuse and overuse of antimicrobial products in humans, animals, and plants.

Lakhey said resistance must be viewed as a global issue that extends beyond clinical settings.

“Antimicrobial resistance in general has been given this nickname of a ’silent pandemic,'” she said.

“It’s happening every year. There are millions of people affected and almost five million deaths every year due to AMR, but we don’t really see it how we can see other diseases or other pandemics.”

Lakhey said bacteria naturally develop resistance over time, but widespread antibiotic use can accelerate that process.

“We’re just contributing to their evolution in a way that that evolution happens faster than how it’s supposed to be,” she said.

“Because we’re using a lot of antibiotics, and they’re getting used to these antibiotics in higher concentrations in the environment, or even in our human body, the resistance is just becoming faster and faster.”

Prevention Starts at the Source

While the findings raise questions about antibiotic pollution, Lakhey said Australian wastewater treatment plants are already performing well at removing many pharmaceutical compounds before treated water is released back into the environment.

“Wastewater treatment plants, especially here in Australia, are really doing an amazing job at working on how to remove bloodstream antibiotics,” she said.

Rather than focusing solely on treatment technologies, Lakhey said efforts should be directed towards reducing the amount of antibiotics entering wastewater systems in the first place.

“I think more attention should be towards how we can prevent it,” she said, adding that true prevention involves addressing the problem at the source.

Antibiotic stewardship is one part of the solution. Lakhey said this includes ensuring antibiotics are prescribed appropriately and only used when necessary.

“For example, antibiotics don’t work against viral infections like the common cold, so avoiding unnecessary prescriptions helps slow the development of resistance,” she said.

“Stewardship also means using the right antibiotic, at the right dose, for the right amount of time, rather than taking a one-size-fits-all approach.”

However, Lakhey said addressing antimicrobial resistance would require a broader approach.

“Stewardship is a big part of the solution, but it’s not the only one,” she said.

She pointed to measures such as vaccination, good hygiene, and infection control to reduce infections and limit the need for antibiotics in the first place.

While environmental monitoring is receiving increasing attention, new approaches like phage therapy are being investigated. This technique works by using phages, a type of virus, to selectively target strains of bacteria, such as those that become resistant to antibiotics.

“We also need stronger surveillance and more attention to how antibiotics and resistant bacteria move through the environment,” Lakhey said.