As the dumping of untreated wastewater into the sea sparks pollution warnings, new research has identified a “significant risk” of increasing antimicrobial resistance associated with wastewater systems across the UK.
A research team led by the University of Exeter has carried out the most comprehensive assessment of risks posed by antibiotics in the environment in the UK to date, now published in the journal Environment International.
The team discovered that the levels of the antibiotic ciprofloxacin are likely to result in increased antibiotic resistance in wastewater and, in some cases, potentially in rivers. Ciprofloxacin is commonly used to treat respiratory, skin, and urinary tract infections, amongst other conditions.
Crucially, the research shows that antibiotic pollution from human waste poses a risk to the environment in higher-income countries like the UK, despite having longstanding sanitation infrastructures.
The World Health Organisation recognises antibiotic resistance as one of the greatest health threats of our time. By 2050, up to 10 million deaths each year could be caused by antibiotics. Other antimicrobial drugs would no longer work to treat common diseases, including respiratory tract, sexually transmitted, and urinary tract infections. The threat of resistance could also increase the risk of contracting an infection after basic surgical procedures.
Around 70 per cent of the antibiotics taken as medicines end up in the natural environment. They end up there through trace residues excreted by patients and inappropriate disposal of drugs, among other sources.
Bacteria are also present in wastewater. When exposed to antibiotics, they can evolve resistance within these environments. This could mean an increased threat to human health if resistant bacteria enter and colonise the gut by swallowing water while swimming.
Antimicrobial resistance detected at high levels
A recent UK Water Industry Research (UKWIR) survey measured the concentrations of several antibiotics in untreated wastewater entering treatment plants and the treated wastewater released into rivers and streams.
The survey, conducted at 67 treatment plants across the UK, was carried out across all four seasons over multiple years.
The research team at the University of Exeter Medical School compared this data to results from their previous studies. Those studies determined the lowest antibiotic concentrations that increase antibiotic resistance. They found a significant risk that the antibiotic ciprofloxacin could result in increased antibiotic-resistant bacteria in wastewater and the environment.
Comments from authors
Dr Aimee Murray of the University of Exeter, who led the research, said: “We need more awareness of the fact that antibiotics are environmental pollutants. When we take antibiotics, they aren’t fully broken down by our bodies. Instead, they are excreted into our wastewater treatment system and released into the environment. This research shows that antibiotic pollution could increase antibiotic resistance in sewage and, in some cases, our rivers. Elevated levels of antibiotic resistance pose a greater threat to human health.
“This is the first evidence of risks posed by antibiotics in the UK in driving increased antibiotic resistance in the environment. It’s very timely considering the current public concern over sewage pollution. Release of antibiotics into the environment isn’t currently regulated. This paper and other emerging research suggest this may be required in future.”
PhD student April Hayes and joint-first author said: “Concern is increasing about pollution in our surface waters in the UK. This research demonstrates that pharmaceutical pollution is also a threat to our waters in England and Wales. Additionally, this research shows that this risk can vary by region, likely due to several different factors. Further understanding of the differences between these regions, such as antibiotic prescribing rates, or types of wastewater treatment used, may help address this pressing issue.”
Concerning levels of antimicrobial resistance
PhD student Laura Murray and joint-first author, said: “Antibiotics can persist in UK wastewater effluent despite the sewage being treated. Some, such as ciprofloxacin, can be present in UK surface waters, including rivers, at levels that may drive the evolution of antibiotic-resistant bacteria. A particular concern is that storms and heavy rainfall can cause untreated sewage overflows. On the one hand, the discharge of raw sewage could result in higher antibiotic resistance risks as the sewage hasn’t been treated. On the other hand, the raw sewage may be heavily diluted with rainwater, decreasing risks. Certainly, more research on combined sewer overflows is needed to appreciate how raw sewage discharges impact antibiotic resistance risk fully.”
The research found that the East of England had the highest risks of antibiotic resistance development in untreated sewage. The East Midlands saw the highest risks in treated sewage overall. The West Midlands and the South West were close behind. This also translated into the highest predicted risks for these three regions in the rivers and streams receiving the treated sewage.
Professor Will Gaze leads the wider environmental dimension of the antimicrobial resistance research programme at the University of Exeter. He said: “It’s important to translate our data on the evolution of antibiotic resistance into risk assessments that can be used to inform policy and practice. This research is a great example of this approach.”
The paper is entitled ‘Predicting selection for antimicrobial resistance in UK wastewater and aquatic environments: ciprofloxacin poses a significant risk’.
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