Thursday, November 27, 2025

Electrolysis can solve one of our biggest contamination problems

ETH Zurich

Patrick Domke and other ETH researchers found the solution in electrolysis — image:
Removing insecticides from contaminated soils – Patrick Domke (pictured) and other ETH researchers found the solution in electrolysis.
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Credit: Hannes Cullum / IVY FILMSTUDIO GmbH

They were once considered miracle workers – insecticides such as lindane or DDT were produced and used millions of times during the 20th century. But what was hailed as progress led to a global environmental catastrophe: persistent organic pollutants (POPs) are so chemically stable that they remain in soil, water and organisms for decades. They accumulate in the fatty tissue of animals and thus enter the human food chain. Many of these substances were banned long ago, but their traces can still be found today – even in human blood.

How to remediate such contaminated sites, be they soils, bodies of water or landfills, is one of the major unresolved questions of environmental protection. How can highly stable poisons be rendered harmless without creating new problems? Researchers at ETH Zurich, led by Bill Morandi, Professor of Synthetic Organic Chemistry, have now found a promising approach. Using an innovative electrochemical method, they are not only able to break down these long-lived pollutants but also to convert them into valuable raw materials for the chemical industry.

Converting pollutants into raw materials

A key distinction between this and previous work is that the carbon skeleton of the pollutants is recycled and made reusable, while the halide component is sequestered as a harmless inorganic salt. “The previous methods were also energetically inefficient,” says Patrick Domke, a doctoral student in Morandi’s group. He explains: “The processes were expensive and still led to outcomes that were harmful to the environment.”

Together with electrochemistry specialist Alberto Garrido-Castro, a former postdoc in this group, Domke developed a process that renders the pollutants in question completely harmless. During this project, the two researchers were able to draw on the many years of experience of ETH professor Morandi, who has been working on the transformation of such compounds for years. “The key advance of this new technology is the use of alternating current to sequester the problematic halogen atoms as innocuous salts such as NaCl (table salt), while still generating valuable hydrocarbons,” says Morandi.

Using electricity to break down toxins

Electrolysis enables almost complete dehalogenation of pollutants under mild, environmentally friendly and cost-effective conditions. It cleaves the stable carbon-halogen bonds, leaving behind only harmless salts such as table salt and useful hydrocarbons such as benzene, diphenylethane or cyclododecatriene. These are actually sought-after intermediates in the chemical industry, for example, for plastics, varnishes, coatings and pharmaceutical applications. In this way, the technology not only contributes to the remediation of contaminated sites but also to the sustainable circular economy.

“What makes our process so special from a technical point of view is that we supply electricity using alternating current, similar to the electrical waveform delivered to households. It is one of the most cost-effective resources in chemistry,” explains Garrido-Castro. “Alternating current protects the electrodes from wear, which is why we can reuse them for many subsequent electrolysis cycles. In addition, the alternating current suppresses unwanted side reactions and the formation of poisonous chlorine gas, allowing the pollutant’s halogen atoms to be fully converted to inorganic salts.” The reactor used by the researchers consists of an undivided electrolysis cell in which dimethyl sulfoxide (DMSO) is used as a solvent – itself a by-product of the pulp process in paper production.

A fully thought-out circular economy

The process can be applied not only to pure substances but also to mixtures from contaminated soils. Soil or sludge can therefore be treated without pre-treatment or further separation processes. A prototype of the reactor has already been successfully tested on classic environmental toxins such as lindane and DDT. “Our system is mobile and can be assembled on site. This eliminates the need to transport these hazardous substances,” explains Domke.

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Plastic pollution is worsened by warming climate and must be stemmed, researchers warn

Increased toxicity from plastic pollution in a warmer climate is highly likely to be affecting whole ecosystems, with potentially disproportionate impacts on apex predators such as orcas

Frontiers

A new review published in Frontiers in Science is calling for urgent action to avoid irreversible ecological damage by stemming the tide of microplastics entering the environment.

Climate change conditions turn plastics into more mobile, persistent, and hazardous pollutants. This is done by speeding up plastic breakdown into microplastics - microscopic fragments of plastic - spreading them considerable distances, and increasing exposure and impact within the environment.

This is set to worsen as both plastic manufacturing and climate effects increase. Global annual plastic production rose 200-fold between 1950 and 2023.

The authors, from Imperial College London, urge eliminating non-essential single-use plastics (which account for 35% of production), limiting virgin plastic production, and creating international standards for making plastics reusable and recyclable.

“Plastic pollution and the climate are co-crises that intensify each other. They also have origins—and solutions—in common,” said lead author Prof Frank Kelly, from Imperial’s School of Public Health. “We urgently need a coordinated international approach to stop end-of-life plastics from building up in the environment.”

Joint crises

The researchers conducted a comprehensive review of existing evidence that highlights how the climate crisis worsens the impact of plastic pollution.  

Rising temperatures, humidity, and UV exposure all boost the breakdown of plastics. Furthermore, extreme storms, floods, and winds can increase fragmentation as well as dispersal of plastic waste – with six billion tons and rising – into landfill, aquatic and terrestrial ecosystems, atmospheric environments, and food webs.

There are growing concerns about the persistence, spread, and accumulation of microplastics that can disturb nutrient cycles in aquatic ecosystems, reduce soil health, and crop yields. They also adversely affect feeding, reproduction, and the behavior of organisms that are capable of ingesting them, should levels exceed safe thresholds.

Microplastics can also act as ‘Trojan horses’ to transfer other contaminants like metals, pesticides, and PFAS ‘forever chemicals’. Climatic conditions may also enhance the adherence and transfer of these contaminants, as well as the leaching of hazardous chemicals such as flame retardants or plasticizers.

There is also historical plastic to consider. When ice forms in the sea, it takes up microplastics and concentrates them, removing them from the water. However, as sea ice melts under warming conditions, this process could reverse and become a major additional source of plastic release.

“There’s a chance that microplastics – already in every corner of the planet – will have a greater impact on certain species over time. Both the climate crisis and plastic pollution, which come from society’s over-reliance on fossil fuels, could combine to worsen an already stressed environment in the near future,” said co-author Dr Stephanie Wright from Imperial’s School of Public Health.

Apex predators particularly vulnerable

Combined impacts when both stressors occur together are particularly apparent across many marine organisms. Research into corals, sea snails, sea urchins, mussels and fish shows that microplastics can make them less able to cope with the rising temperatures and ocean acidification.

Filter-feeding mussels can concentrate microplastics extracted from the water, transferring this pollution to predators: effects like this can increase levels of microplastics higher in the food chain.

Species at these higher trophic levels are often already vulnerable to a host of other stressors, whose effects may be amplified by plastics. For instance, a recent study found that microplastic-induced mortality in fish quadrupled with a rise in water temperature. Another study showed that increased ocean hypoxia, which is also driven by warming, caused cod to double their microplastic intake.

Apex predators such as orcas may be particularly susceptible to the double hit of microplastics and climate change. These long-lived mammals are likely to experience significant microplastic exposure over the course of their lifetime.

The potential loss of keystone species that shape the functioning of the wider ecosystem could have far-reaching implications.

“Apex predators such as orcas could be the canaries in the coal mine, as they may be especially vulnerable to the combined impact of climate change and plastic pollution,” said co-author Prof Guy Woodward from Imperial’s Department of Life Sciences.

Microplastics are also known to affect ecosystems on land, but these interactions are even more complex and harder to predict than for aquatic life.

Urgent action required on microplastics

The evidence showing increased amounts, spread, and harm of microplastics adds further impetus to calls for urgent action on plastic pollution.

The researchers say we must rethink the whole approach towards using plastics in the first place. “A circular plastics economy is ideal. It must go beyond reduce, reuse, and recycle to include redesign, rethink, refuse, eliminate, innovate, and circulate — shifting away from the current linear take–make–waste model,” said co-author Dr Julia Fussell from Imperial.

This review also demonstrates that integrating interactive effects of plastic pollution and climate stressors offers a way to steer, coordinate and prioritize research and monitoring, along with policy and action.

According to Wright: “The future will not be free of plastic, but we can try to limit further microplastic pollution. We need to act now, as the plastic discarded today threatens future global-scale disruption to ecosystems.”

“Solutions require systemic change: cutting plastic at source, coordinated global policy such as the UN Global Plastics Treaty, and responsible, evidence-based innovation in materials and waste management,” said Kelly.

Journal

Frontiers in Science

DOI

10.3389/fsci.2025.1636665

Method of Research

Literature review

Subject of Research

Not applicable

Article Title

Plastic pollution under the influence of climate change: implications for the abundance, distribution and hazards in terrestrial and aquatic ecosystems

Article Publication Date

27-Nov-2025

Microplastics pose a human health risk in more ways than one

University of Exeter

image:
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.

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.

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

Credit

Stevenson et al

Stevenson et al Figure 4

Credit

Stevenson et al