Microplastics pose a human health risk in more ways than one

University of Exeter

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Bio-beads collected near Truro, Cornwall

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Credit: Beach Guardian

A new study shows that microplastics in the natural environment are colonised by pathogenic and antimicrobial resistant bacteria. The study team calls for urgent action for waste management and strongly recommends wearing gloves when taking part in beach cleans.

Microplastics are plastic particles less than 5mm in size and are extremely widespread pollutants. It is estimated that over 125 trillion particles have accumulated in the ocean (surface to seabed) and they have also been detected in soils, rivers, lakes, animals and the human body.

An emerging concern associated with microplastics are the microbial communities that rapidly make their home on the particle surface, forming complex biofilms known as the “Plastisphere”. These communities may often include pathogenic (disease-causing) or antimicrobial resistant (AMR) bacteria.

Wastewater treatment plants or solid waste landfill sites have been proposed to spread, boost or influence the evolution of antimicrobial resistance and pathogens in nature. This may well increase the risk to human health and it is therefore vital that more is understood about the interactions of the bacterial communities within the Plastisphere and other marine pollutants, such as domestic and clinical wastewater.

Lab studies have shown that some commonly-discarded plastic materials serve as a platform for the selective growth of bacterial communities responsible for AMR and diseases in both humans and animals. Whilst previous work has explored this in the environment, several questions and issues remained unanswered, which this new study aimed to address.

The study, titled ‘Sewers to Seas: Exploring Pathogens and Antimicrobial Resistance on Microplastics from Hospital Wastewater to Marine Environments’, was published this week in the journal Environment International.

The study team, led by Dr Emily Stevenson and involving scientists from Plymouth Marine Laboratory and the University of Exeter, developed a novel structure that would allow five different substrates (bio-beads, nurdles, polystyrene, wood and glass) to be secured along a waterway that was expected to decrease in anthropogenic pollution downstream.

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Bio-beads are small plastic pellets used in the wastewater treatment process by UK water companies to provide a surface for bacteria to grow and break down nutrients.

Nurdles are small plastic pellets used as the raw material to make almost all plastic products, such as bottles, clothes and car parts.

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After two months in the water, bacterial biofilms growing on each substrate were analysed using metagenomics; the genomic analysis of genetic material collected from an entire community of organisms in a specific environment.

The findings showed:

• Pathogens and AMR bacteria were found on all substrates, across all sample sites.
• Polystyrene and nurdles may pose a greater AMR risk than other substrates, potentially due to their ability to adsorb antibiotics and promote biofilm formation that facilitates transfer of antimicrobial resistance genes (ARGs). ​
• Over 100 unique ARGs sequences were identified in microplastic biofilms, which is more than on natural (wood) or inert (glass) substrates. ​
• Environmental bio-beads can support bacteria that carry resistance genes to key antibiotics, like aminoglycosides, macrolides and tetracyclines.
• Unexpectedly, some bacterial pathogens increased in prevalence moving downstream, when associated with microplastic biofilms. ​
• Environmental location played a significant role in microbial community composition and AMR gene prevalence.
• There is a potential biosecurity risks posed by microplastics, particularly in areas near aquaculture facilities, where filter-feeding organisms may ingest colonised particles containing pathogens and ARGs. ​

Dr Emily Stevenson, lead author and PhD researcher with Plymouth Marine Laboratory and the University of Exeter at the time of the study, said: “Following the recent concerning release of sewage bio-beads in Sussex, this timely study highlights the pathogenic and AMR risk posed by microplastic substrates littering our ocean and coasts. By identifying high-risk substrates, we can improve the monitoring of those, or even phase them out for safer alternatives.

“This novel research used a specifically-designed incubation structure that helped reduce bias from biofilm communities growing on cages, bags or boxes used to secure microplastics in traditional studies. Our study fixed these news structures along a transect from the clinic to marine waters and our findings clearly show the importance of this multiple environment transect. Previous studies have detected AMR and pathogen colonisation high pollution zones but we show that other surface waters can harbour communities with a high proportion of AMR.

“As this work highlights the diverse and sometimes harmful bacteria that grows on plastic in the environment, we recommend that any beach cleaning volunteer should wear gloves during clean ups, and always wash your hands afterwards”.

Professor Pennie Lindeque, co-author and Head of Group for Marine Ecology and Society at Plymouth Marine Laboratory, said: “Our research shows that microplastics can act as carriers for harmful pathogens and antimicrobial-resistant (AMR) bacteria, enhancing their survival and spread. This interaction poses a growing risk to environmental and public health and demands urgent attention.

“By tracking a source-to-sea pathway influenced by hospital and domestic wastewater discharges, our study shows how antimicrobial-resistant pathogens colonised all substrates. Protected within their biofilms, each microplastic particle effectively becomes a tiny vehicle capable of transporting potential pathogens from sewage works to beaches, swimming areas and shellfish-growing sites.”

Dr Aimee Murray, co-author and Senior Lecturer of Microbiology at the University of Exeter, concluded: “Our research shows that microplastics aren’t just an environmental issue – they may also play a role in the dissemination of antimicrobial resistance. This is why we need integrated, cross-sectoral strategies that tackle microplastic pollution and safeguard both the environment and human health”.

The study team emphasises the need for further research into how microplastics interact with co-occurring pollutants, and for improved waste-management practices to reduce the spread of AMR and pathogenic organisms in the environment.

The research team have published an article in the Conversation: “Plastic ‘bio-beads’ from sewage plants are polluting the oceans and spreading superbugs – but there are alternatives.”

Stevenson et al Figure1

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Stevenson et al

Stevenson et al Figure 4

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Stevenson et al

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Journal

Environment International

DOI

10.1016/j.envint.2025.109944 

Article Title

Sewers to Seas: exploring pathogens and antimicrobial resistance on microplastics from hospital wastewater to marine environments

Article Publication Date

20-Nov-2025

 

Microplastics disrupt gut microbiome and fermentation in farm animals: Study reveals new risks to animal health and food safety

University of Helsinki

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Tiny plastic particles pervasive in agricultural environments, interact with and disrupt the microbial ecosystem in the rumen – the first stomach chamber of cattle.

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Credit: Helena Kuoppala.

Microplastics, tiny plastic particles pervasive in agricultural environments, interact with and disrupt the microbial ecosystem in the rumen – the first stomach chamber of cattle, reveals an international study.

“Our work is a first step toward understanding the biological consequences of microplastic exposure in farm animals,” said lead researcher Daniel Brugger, Associate Professor of Companion and Monogastric Production Animal Nutrition at the University of Helsinki. “There is an urgent need for in-vivo studies to better understand the impacts on animal health and food safety, especially as global plastic production continues to rise.”

The findings of a joint study from the University of Helsinki, University of Zurich, University of Hohenheim, and Technical University of Munich not only shed light on how microplastics are transformed within the digestive system of farm animals but also highlight potential risks for animal health, productivity, and food safety.

Using a controlled laboratory fermentation system, researchers incubated rumen fluid from cows with hay or barley and five common types of microplastics found in agricultural settings: polylactic acid (PLA), polyhydroxybutyrate (PHB), high-density polyethylene (HDPE), polyvinyl chloride (PVC), and polypropylene (PP). The microplastics were tested in various particle sizes and doses to evaluate their impact on rumen fermentation, microbial activity, and the plastics themselves.

The key findings of the study are:

• All tested microplastics did not remain inert in the rumen; instead, they interacted with the microbial ecosystem, altering fermentation and microbial functions.
• Their presence consistently reduced cumulative gas production, a key indicator of overall fermentation activity, regardless of plastic type, particle size, or dose.
• Total dry-matter disappearance increased with microplastic addition, suggesting that not only feed but also part of the plastic mass was broken down during fermentation, and potentially reduced microplastic size, increasing tissue penetration risk
• In barley-based incubations, microbial activity shifted, with proteins linked to stress responses increasing, while those involved in carbohydrate and amino-acid metabolism decreased - a pattern that is typical of a microbial stress response.

These results indicate that microplastics disturb normal microbial metabolism and are likely to be at least partially degraded into smaller fragments by rumen microbes.

Implications for agriculture and food safety

The study closes an important knowledge gap about how microplastics behave in the digestive systems of farm animals. While previous research has established that livestock are exposed to microplastics through contaminated soils and feed, it was unclear whether these particles remained unchanged or interacted with the microbiome.

“Our study shows for the first time that microplastics do not simply pass through the digestive tract of farm animals. Instead, they interact with the gut microbiome, alter fermentation processes, and are partially broken down,” says Jana Seifert, Professor of Functional Microbiology of Livestock at the University of Hohenheim, Germany. “This means farm animals are not passive recipients of plastic pollution; their digestive systems may act as bioreactors that transform microplastics and redistribute them within agricultural systems.”

However, the findings also raise significant concerns. A stressed, less efficient microbiome could negatively impact animal health and productivity. Additionally, smaller plastic fragments formed during digestion may be more easily absorbed into tissues, potentially entering the human food chain. This risk could be particularly pronounced in young or stressed animals with more permeable intestinal barriers.

How to avoid plastics ending up to the feed-food chain?

Researchers raise the need for better management of plastic use in agriculture, including silage films, packaging materials, and sewage sludge on fields, to reduce microplastic contamination in animal feed. “Plastic pollution isn’t just an environmental issue ‘out there.’ It has direct biological consequences for farm animals, and potentially for humans, through the food chain,” Cordt Zollfrank, Professor of Biogenic Polymers at the Technical University of Munich, Germany, emphasises.

The research also provides a scientific foundation for future risk assessments and monitoring. Regulators, veterinarians, and the feed industry now have experimental evidence that microplastics interact with the rumen microbiome and are partially transformed. This must be considered when defining acceptable contamination levels and developing methods to detect plastics in feed, manure, and animal products.

“Our findings may also help to inform future research on microplastic–microbiome interactions in non-ruminant species, such as pigs, although this still needs to be tested in those animals,” says Brugger.

 

About microplastics
While most people associate microplastics with oceans and marine life, a significant portion of plastic pollution ends up on farmland, eventually reaching animal feed and digestive systems. Microplastics have already been detected in livestock feed, manure, and even human stool samples, indicating their circulation through the feed–food chain.

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Journal

Journal of Hazardous Materials

DOI

10.1016/j.jhazmat.2025.140481 

Subject of Research

Animals

Article Title

The interaction of microplastics with the ruminal ecosystem in vitro

Article Publication Date

19-Nov-2025

 

Recycling a pollutant to make ammonia production greener

Tohoku University

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Synthesis procedure and microstructural characterizations of RuGa IMC/C.

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Credit: Hao Li et

Ammonia fuels agriculture, supports industry, and is increasingly viewed as a key player in future clean-energy systems. Yet producing it is heat and pressure intensive. A research team has developed an electrocatalyst that helps turn nitrate--a common pollutant found in groundwater and agricultural runoff--into ammonia under far milder conditions.

Details of their findings were published in the journal Advanced Functional Materials on November 4, 2025.

"Our new catalyst has two main benefits: first, it reduces the emissions linked to fertilizer and chemical manufacturing, and second, it enables us to essentially recycle nitrate, which would otherwise pollute our water," points out Hao Li, Distinguished Professor at Tohoku University's Advanced Institute for Materials Research (WPI-AIMR).

The catalyst is made from an atomically ordered alloy of ruthenium (Ru) and gallium (Ga), forming a ruthenium-gallium intermetallic compound supported on carbon (RuGa IMC/C). Its structure places individual ruthenium atoms in precise positions surrounded by gallium, which does not react directly but shapes the environment in which each ruthenium site operates. This fine-tuned arrangement helps guide nitrate (NO₃⁻) toward the reaction steps that produce ammonia (NH₃).

Even at low nitrate concentrations, the catalyst converts nitrate efficiently at a very gentle voltage. It maintains strong selectivity across a broad concentration range and continues operating with steady performance, showing that careful atomic design can support nitrate conversion under realistic environmental conditions.

Computer simulations conducted by the researchers revealed why the structure worked so well. By introducing gallium, the electronic characteristics of ruthenium shift, affecting how nitrogen-containing molecules attach and transform on the surface. This adjustment also slows down hydrogen formation, a competing reaction that often limits ammonia yields.

The catalyst was also evaluated in a zinc-nitrate battery. The system generated consistent power and ran for hundreds of hours, showing that the material can support both chemical production and energy-related applications.

"We hope to convert a widespread pollutant into a valuable product and offer guidance for designing future catalysts that take advantage of controlled atomic ordering," adds Li.

Looking ahead, the researchers plan to expand their theoretical modeling, integrating machine-learning tools to more effectively map reaction pathways. This work aims to accelerate the design of next-generation electrocatalysts for sustainable chemical production.　

About the World Premier International Research Center Initiative (WPI)

The WPI program was launched in 2007 by Japan's Ministry of Education, Culture, Sports, Science and Technology (MEXT) to foster globally visible research centers boasting the highest standards and outstanding research environments. Numbering more than a dozen and operating at institutions throughout the country, these centers are given a high degree of autonomy, allowing them to engage in innovative modes of management and research. The program is administered by the Japan Society for the Promotion of Science (JSPS).

See the latest research news from the centers at the WPI News Portal: www.eurekalert.org/newsportal/WPI

Main WPI program site:  www.jsps.go.jp/english/e-toplevel

Advanced Institute for Materials Research (AIMR)

Tohoku University

Establishing a World-Leading Research Center for Materials Science

AIMR aims to contribute to society through its actions as a world-leading research center for materials science and push the boundaries of research frontiers. To this end, the institute gathers excellent researchers in the fields of physics, chemistry, materials science, engineering, and mathematics and provides a world-class research environment.

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Journal

Advanced Functional Materials

DOI

10.1002/adfm.202524120 

Article Title

Atomically Ordered RuGa Intermetallic Electrocatalyst Enables High-Efficiency Nitrate-to-Ammonia Conversion

Article Publication Date

24-Nov-2025

A universal formula is developed to predict the impact of temperature on living beings

An international research project involving the University of Granada has unified more than 30,000 thermal performance measurements in some 2,700 species

University of Granada

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The Universal Thermal Performance Curve (UTPC) can be applied to all species and measures of their performance in response to thermal variations: from battery cell division (left) to shark swimming in the ocean (right).

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Credit: University Of Granada

An international team of researchers, including members from the University of Granada, has developed a mathematical model that predicts with unprecedented accuracy how temperature affects all levels of life, from enzymes to entire ecosystems. The study, which has just been published in the journal Proceedings of the National Academy of Sciences (PNAS), reveals that there is a universal curve that describes this behavior in virtually all living organisms, a finding that will revolutionize our understanding of the impact of global warming on nature.

The study involved Ignacio Peralta Maraver, a researcher in the Department of Ecology and the Modeling Nature (MNat) Unit of Excellence at the University of Granada, Jean-François Arnoldi, from the CNRS Theoretical and Experimental Ecology Station in Moulis (France), and Andrew L. Jackson and Nicholas Payne, from the Department of Zoology at Trinity College Dublin. The research shows that, from the molecular level to the ecosystem scale, all processes that vary with temperature can be unified under a single mathematical equation.

The universal pattern of nature

For Ignacio Peralta-Maraver, “this model could become a new standard in the ecology and physiology of global warming.” All living beings are affected by temperature, but the newly validated mathematical equation—the Universal Thermal Performance Curve (UTPC)—unifies tens of thousands of seemingly distinct curves that explain how species function at different temperatures. Most surprisingly, the UTPC seems to apply not only to all species, but also to any measure of their performance in the face of thermal variations: from lizards running on a treadmill to sharks swimming in the ocean to the rate of cell division in bacteria.

The most relevant aspect of the new UTPC is that it shows a common pattern: as organisms warm up, their performance slowly increases until it reaches an optimum (where it is at its maximum), but with further warming, performance declines rapidly. This rapid decline above the optimum temperature means that overheating can be dangerous, with the risk of physiological failure or even death. One of the clearest conclusions of the study is that species may be more limited than feared in their ability to adapt to global climate change, given that temperatures continue to rise in most regions.

Understanding how species adapt to change

The results of the study are consistent across an analysis of more than 30,000 different performance measures and a huge diversity of species: from bacteria to plants, and from lizards to insects. This means that the pattern holds across species from all major groups that have diverged widely over billions of years of evolution.

Despite this great biological diversity, the study shows that, in essence, all life forms remain remarkably constrained by this “rule” that dictates how temperature influences their ability to function. The most that evolution has achieved is to shift the curve up or down, but life has not found a way to deviate from this specific form of thermal performance.

The next step in the research will be to use this model as a reference to identify whether there are species or systems that, even in a subtle way, manage to escape this pattern. If they are found, we will have to ask ourselves why and how they do so, especially given the projections of an increasingly warmer climate in the coming decades.

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Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2513099122 

Method of Research

Experimental study

Subject of Research

Animals

Article Title

A universal thermal performance curve arises in biology and ecology