Microplastics as "Vehicles for Bacteria" — The Invisible Risk from Sewage to Sea: The Quiet Pandemic of Microplastics and Antibiotic-Resistant Bacteria

1. Another "Face" of the Microplastic Problem

When people hear the word microplastics, many imagine "ocean trash" or "particles swallowed by sea turtles and seabirds."

However, recent research has highlighted that this issue is not just about "visual pollution."

A study titled "Sewers to Seas" by a UK research team revealed that microplastics act as carriers for pathogens and antibiotic-resistant bacteria (AMR bacteria), posing significant health risks to humans.Phys.org

Microplastics are tiny plastic fragments less than 5mm in size, with an estimated 125 trillion pieces existing in the ocean alone. Various studies have shown that they infiltrate from mountainous regions to the deep sea, soil, rivers, lakes, and even the human body.Phys.org

The focus of the recent study was on the microbial world called the "Plastisphere" that forms on the surface of these particles. This includes not only environmental microbes but also pathogens that cause diseases in humans and animals, as well as antibiotic-resistant bacteria.Phys.org

2. From Sewers to Seas: The Route Traced by "Sewers to Seas"

The research team installed a specialized device capable of fixing five types of materials in a waterway extending from hospital wastewater in southwestern England to the sea.

• Bio-beads used in sewage treatment plants

• Pellets known as nurdles, which are raw materials for plastic products

• Polystyrene fragments used in foam trays, among other things

• Wood fragments (natural material) for comparison

• Glass fragments (inert material) also for comparison

These were placed along points where pollution levels were expected to gradually decrease, from upstream near hospital wastewater, through midstream where urban wastewater mixes, to estuarine and coastal seawater. After two months, the biofilm (microbial membrane) that developed on each particle was collected and analyzed using metagenomics to examine the genes and microorganisms present.Phys.org

3. Findings: Plastics as "Prime Real Estate for Superbugs"

The analysis results were far from reassuring.

• Pathogens and antibiotic-resistant bacteria were detected on all materials and at all locations

• Particularly on the surfaces of polystyrene and nurdles, numerous resistance genes (ARGs) were concentrated

• Over 100 types of resistance genes were found in the plastic biofilm, far more than on the surfaces of wood or glass

• Bio-beads harbored bacteria with resistance genes against medically important antibiotics such as aminoglycosides, macrolides, and tetracyclines

• Surprisingly, certain pathogens increased on plastics as they moved downstream

In essence, plastic particles not only "carry some pathogens and resistant bacteria wherever they are," but also "concentrate particularly dangerous genes depending on the material."pml.ac.uk

The research team further warned that near fishing grounds and aquaculture sites, these "contaminated microplastics" could be ingested by filter-feeding organisms like bivalves, increasing health risks and biosecurity concerns through food consumption.pml.ac.uk

4. A World Where Antibiotics No Longer Work and Microplastics

Antibiotic-resistant bacteria (AMR) are already identified by the World Health Organization (WHO) as one of the greatest public health risks to humanity. In 2019, it was estimated that at least 1.27 million people died directly from AMR infections, with resistant bacteria involved in about 4.95 million deaths, surpassing the numbers for malaria and HIV.World Health Organization

The main cause of this crisis is, of course, the overuse of antibiotics in humans and livestock. However, "Sewers to Seas" illustrated a scenario where used antibiotics and excreta flow into the sewage, meet microplastics, and create a favorable "breeding ground" for resistant bacteria.Phys.org

The biofilm forming on plastic surfaces functions as a shelter protecting bacteria from antibiotics and UV rays, and if residual drugs are present, it can become a "selection test" site where only resistant bacteria survive. This study visualized a part of this scenario by tracing it continuously from sewage treatment plants to the sea.pml.ac.uk

5. A Timely Reality: Bio-bead Spill at Camber Sands

Coinciding with the publication of this study, a major news event occurred at Camber Sands, a popular beach in East Sussex, England, where millions to tens of millions of bio-beads were spilled from a sewage treatment plant.The Guardian

Despite the name "bio-beads," the content is plastic. They have been used for decades to cultivate bacterial films on their surfaces to purify wastewater. However, once leaked outside, they wash up on coastlines, are ingested by birds and fish mistaking them for food, and gradually become microplastics over time.The Guardian

Environmental groups like Surfers Against Sewage and local politicians strongly criticized the incident as a "man-made disaster exacerbated by failing infrastructure and the climate crisis," calling for a phased-out transition from the old bio-bead method to safer treatment technologies.Surfers Against Sewage

Amidst this, the recent study showing that antibiotic-resistant bacteria can settle on the surfaces of artificial plastics like bio-beads was received as a "timely warning."

6. How Did Social Media React?—Spreading Anxiety and Calls for Action

The study was shared on platforms like X (formerly Twitter) and Threads through official accounts of Phys.org and university and marine research institutions, reaching communities interested in marine environments and public health.Threads

Reactions on social media generally fell into the following tones.
(The following are not actual posts but summarized impressions of typical reactions.)

1. "What should we do about beach cleanups?" group

   • "I used to pick up nurdles with bare hands... I'll definitely wear gloves from now on."

   • "How careful should I be when playing on the beach with my kids?"
     Research teams and media are also urging the use of gloves and thorough handwashing during beach cleanup activities.Phys.org

2. "Questioning Infrastructure and Corporate Responsibility" group

   • "There's a limit to personal reusable bottles. We need to change the sewage treatment system."

   • "Have water utility companies underestimated the risks of continuing to use bio-beads?"
     Linked to the Camber Sands incident, there are prominent calls for "updating old treatment facilities."The Guardian

3. "Calling for Calm Amid Microplastic 'Panic'" group

   • "While there is indeed a risk, we must not forget the daily benefits of medicine and hygiene."

   • "The issue is not 'plastic or zero,' but 'where, how to use, and how to collect it.'"
     Some experts and journalists are encouraging discussions on scientific risk assessment and specific measures, rather than just inciting fear.pml.ac.uk

4. "Fisheries and Aquaculture Stakeholders Concerned About the Sea and Dining Tables"

   • "How should we explain the safety of shellfish and seafood?"

   • "The monitoring system is lagging behind."
     Fishery news sites and marine industry media are also covering this study, and discussions are beginning in the industry.Fish Focus

Looking at social media as a whole, while there is a growing recognition that "microplastics are a deeper issue than imagined," society as a whole still seems to be searching for answers to the question, "So what should we change?"

7. What We Can Do: From Individual to Policy Level

So, what can we do about the issue of "microplastics and antibiotic-resistant bacteria"?