Bacteria such as E. coli and intestinal enterococci can survive long enough on sewage-associated plastic waste like wet wipes and cotton swabs to pose risks to human health if they wash up on shore, new research from Scotland’s University of Stirling has found.
Over two days last December, researchers collected and sampled plastic waste found on 10 beaches against naturally-occurring substrates such as sand and seaweed, where there is little opportunity for the faecal matter to bind. The plastic essentially enhances the survival of the harmful bacteria, the study found.
Thirty-three wastewater treatment plants discharge directly into the tidal estuary where the research was conducted.
To illustrate the extent of the issue, the study refers to the findings of the 2021 Great British Beach Clean, which reported an average of 25 wet wipes per 100 m on Scottish beaches.
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In the U.K., a government Environmental Audit Committee estimated in 2022 that some 7 million wet wipes, 2.5 million tampons and 1.5 million sanitary pads are incorrectly flushed down the toilet every day, resulting in sewage blockages and the release of untreated sewage into the aquatic environment.
The problem has also occurred in Canada. Earlier this spring, when a valve broke at a wastewater treatment plant in the west of Quebec City, hundreds of millions of litres of sewage flowed into the St. Lawrence River, forcing officials to ask residents not to flush baby wipes or sanitary napkins down the toilet.
Canadian research has also highlighted other issues around wipes. In 2019, Toronto Metropolitan University researchers found during testing that 21 out of 23 wet wipes marketed as “flushable” did not disintegrate in drains. Wet wipes, baby wipes, moist towelettes, and sanitary products can be made partly or fully of plastic polymers, including polyethylene terephthalate (PET), polypropylene (PP) and polyethylene.
But now, researchers from Stirling’s Faculty of Natural Sciences have found that wipes washed up on the beach may be more than just eyesores.
“Plastics in the environment become rapidly colonized by microbial biofilm and such ‘plastisphere’ communities are highly variable, diverse and importantly can harbour human pathogens,” states the study.
The research is part of the £1.85 million Plastic Vectors’ project – funded by the Natural Environment Research Council (NERC) – which is investigating how plastics in the environment can help transport bacteria and viruses, and the impact that may have on human health.
The team also found evidence that species of vibrio – a naturally occurring bacteria, some strains of which can cause a severe upset stomach – were able to colonize on wet wipes. They also found high rates of antimicrobial resistance and resistance to antibiotics present in the bacteria on the wipes and cotton swabs.
Led by Professor Richard Quilliam from Stirling’s department of Biological and Environmental Sciences, the research team notes that sewage being directly discharged into rivers and the sea has been more common in recent years, especially after heavy rain when some sewage treatment plants exceed their capacity for effective treatment.
“Some of the plastic waste we have recovered could be from legacy sewage spills that have persisted in the environment, but the volume of waste we are seeing is shocking,” said Professor Quilliam in a statement about the new research.
PhD researcher Rebecca Metcalf, also from the University of Stirling, is lead author of a new paper reporting the study. She said: “Finding faecal bacteria could also indicate the possibility of other human pathogens such as norovirus, rotavirus, or salmonella.
“The extent to which people could be exposed to these pathogens is beyond the scope of our study, but obviously there’s always a risk of children picking up and playing with wet wipes or other plastic waste on the beach,” added Metcalf.
Researchers said that the demand for wet wipes has increased as a result of the COVID-19 pandemic, and “now more than ever, there is an urgent need for greater investment in public awareness programs to eliminate wet wipes entering sewerage systems.”
Back in Canada, the Saskatchewan City of Prince Albert even issued an advisory to its 36,000 residents during March of 2021 to stop flushing face masks down the toilet.