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EXPERT REACTION: Clothes washing creates more microplastic pollution on land than in water

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Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Washing clothes made from synthetic microfibres is a major contributor to plastic pollution on cropland, according to new research. US scientists calculated the annual spread of plastic microfibres from hand-washing and washing machines around the world. They found that over 176,500 metric tonnes of microfibres currently end up on cropland and landfill sites via wastewater treatment sludge, compared to 167,000 tonnes leaking into waterways per year. The authors say the use of microplastics should be reduced, since wastewater treatment processes don't prevent pollution.

Journal/conference: PLOS ONE

Link to research (DOI): 10.1371/journal.pone.0237839

Organisation/s: University of California at Santa Barbara, USA

Funder: This work was supported by Ocean Conservancy, Purnell, and the Outdoor Industry Association Microfiber Research Cohort; S.S. acknowledges the financial support of the US Environmental Protection Agency's Science to Achieve Results Program under Grant No. 83557907; and the authors thank H. William Kuni for his generous support for TK's and RG's involvement through the H. William Kuni Interdisciplinary Fellowship.

Media release

From: PLOS

Synthetic clothing fibers contribute vast amounts of plastic pollution to terrestrial environments

Microfibers in wash water largely end up on cropland

176,500 metric tons of synthetic microfibers—chiefly polyester and nylon—are released every year onto terrestrial environments across the globe, according to a new study in the open access journal PLOS ONE by Jenna Gavigan and colleagues at the University of California at Santa Barbara. The microfibers are shed from clothing during washing, and the amount ending up on land now exceeds the amount that enters waterbodies.

Plastic pollution in the ocean has received lots of attention in recent years, but waterways are not the only place that plastic accumulates. Fourteen percent of all plastic is used to make synthetic fibers, chiefly for clothing. Microfibers, defined as particles less than 5 millimeters in length, are generated in large quantities at every stage of a fiber’s life cycle, especially during washing, which mechanically fragments synthetic fibers. When wash water becomes part of the flow to a wastewater treatment plant, the microfibers it contains may be retained along with biosolid sludge, which may be applied to cropland or buried in landfills.

To understand the global scope and distribution of synthetic microfiber release, the authors collected data on global production, consumption, and release of plastics, incorporating further data on microfibers released during washing both by machine and by hand, and the accumulation and distribution of microfibers in wastewater treatment plants and the fate of the wastewater sludge that contains much of this plastic waste. Because many regions do not have detailed data on wastewater treatment, the authors approximated where necessary to develop a comprehensive picture, using median income as a proxy for likely degree of wastewater treatment.

The data does not represent the total emissions produced from clothing throughout its lifetime – for example, secondhand clothing is not accounted for. However, the authors’ calculations showed that approximately 5.6 million metric tons of synthetic microfibers were released from apparel washing between 1950, the start of widespread use of synthetic fibers, and 2016—half of it in the last 10 years. Just under half of it ended up on land, either on the surface (1.9 million metric tons) or in landfills (0.6 million metric tons). Emissions are growing 12.9% annually, and current annual emissions to land (176.5 thousand metric tons per year) exceed those to waterbodies (167 thousand metric tons per year).

“Large-scale removal of microfibers from the environment is unlikely to be technically feasible or economically viable, so the focus needs to be on emission prevention,” Gavigan said. “Since wastewater treatment plants don’t necessarily reduce emissions to the environment, our focus needs to be reducing emissions before they enter the wastewater stream.”

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Professor Ian Rae is an expert on chemicals in the environment at the School of Chemistry at the University of Melbourne. He was also an advisor to the United Nations Environment Programme on chemicals in the environment and isĀ former President of the Royal Australian Chemical Institute

This is the latest wrinkle in the fabric of a fascinating story about the tiny bits of synthetic fibre that are released when our clothes are bashed around in the washing machine, from there they find their way into the environment via wastewater and a sewage treatment plant.

One of the first studies to report this phenomenon was published in 2011 and included results from some sandy beaches in Australia - at Port Douglas (Qld) and Busselton (WA) - and discharge from the sewage plants at West Hornsby and Hornsby Heights in NSW. As a research topic it's been quite popular, taken up by a number of other groups over the intervening decade, so the topic is not new but the study just published has some quantitative data that are unique.

The researchers used world-wide data - necessarily approximate - on the quantity of clothing being washed in machines and by hand (only half as much fibre released in such gentle washing), the rate at which microfibres are released and go to sewage treatment plants and what happens from there, either release to water bodies or retained in solids that can be kept on land or incinerated. They estimate that 360,000 tonnes a year are released from clothes washing, with 167,000 tonnes going to water bodies, and 177,000 tonnes remaining on land. Incineration accounts for 17,000 tonnes and it's worth noting here that pyrolysis could be involved in the future when the waste is used a source of synthetic oil.

The main polymers detected in the study were polyesters and nylons, no surprises there.

'Kept on land' can mean that sewage sludge (it sounds so much better as biosolids, the name we use in Australia) in simply landfilled or used as fertilizer because of the nutrients it contains. Users need to be very careful with the latter practice because of the heavy metals that are also caught in the sewage and can poison soils where crops are grown. 

However, most Australian biosolids still go to agriculture or land rehabilitation.

Australian data are not mentioned explicitly in this study. They are probably contained in the 'rest of world' figures, that account for about 9 per cent of the microfibres being released to the environment.

Most concern about microfibres and other tiny pieces of plastic in the oceans has been about ingestion by marine organisms. Even inert plastics can interfere with the operation of organs when the particles lodge and cause irritation. The other concern is that as they progress through the environment the plastics pick up other organic pollutants like pesticides and industrial chemicals, and can then 'deliver' them as toxins to animals consuming them.

Microfibres in soil are less of a worry than those in the oceans, but the authors of this recent paper recommend strong action to prevent their release from washing machines by redesigning the machines or the fabrics. Good luck with that! Another way is by ensuring more efficient filtering of the water as it leaves the machine, about which they observe that collected material would need to be disposed of by incineration or landfill. And here's a puzzle: if landfill is acceptable as a disposal method, you'd have to ask why there is such a fuss, in the abstract of their paper and the publicity surrounding the publication of their work, about microfibres going to 'terrestrial environments'.

Last updated: 16 Sep 2020 2:16pm
Declared conflicts of interest:
None declared.
Professor Oliver Jones is from the School of Science at RMIT University

You might not realise that you are wearing plastic, but you almost certainly are. Man-made fibres like polyester and nylon that make up much of our modern day wardrobes are actually types of plastic. Like most other plastics they don’t degrade easily but break down into smaller and smaller pieces called microplastics, or in this case, microfibres.

Microfibres are little pieces of artificial fibres less than 5mm long (often much smaller) and thinner than a human hair. Millions of them are released when we wash clothes made of these artificial materials.

We used to think microfibres got washed out to rivers and sea (and they do). What this research does is point out, quite starkly, that microfibre pollution may be an even bigger issue for land that it is for the oceans.

This paper isn’t the complete picture as the data are predicted rather than measured and authors had to estimate make assumptions where raw data weren’t available - but they have done a very thorough job of it. Even if their results are an overestimate, they are still a cause for concern and something we really need to address sooner rather than later.

Last updated: 16 Sep 2020 2:16pm
Declared conflicts of interest:
None declared.
Dr Paul Harvey is an Environmental Public Health Scientist. He was formerly an adjunct Professor at Macquarie University, and is now owner of Environmental Science Solutions and Director of COVID-19 Check Pty Ltd.

This new research quantifies a problem that has been known for a long time. Clothing and other textiles release micro-plastic fibres into the environment when they are washed. What we didn't know before was exactly how much micro-fibre pollution was being created.

The numbers in the research are staggering, but most likely an underestimate. Micro-fibre pollution is possibly the worst kind of plastic pollution, because these fibres are the perfect size for ingestion by marine organisms. The fibres can accumulate in the organism, potentially leading to chemicals leaching from the plastic and into the organism. These organisms are then consumed by higher-order feeders and that is how humans can become exposed to plastic chemicals through consumption of seafood. The article also points to plastic fibres in wastewater sludge that is reused for agriculture purposes which is an unchecked exposure pathway to environmental micro-plastic pollution in Australia.

The research demonstrates that micro-fibre and micro-plastic pollution is a global problem and one which can only be resolved by a universally adopted approach.

Last updated: 16 Sep 2020 2:15pm
Declared conflicts of interest:
None declared.
Dr Thava Palanisami is from the Global Innovative Centre for Advanced Nanomaterials (GICAN) in the School of Engineering at The University of Newcastle

Synthetic fibres are everywhere; emitted from both indoor and outdoor environment. As shown by this study, washing synthetic cloths could contribute an enormous amount of synthetic fibre load. This is just one of the major sources; the overall load will be several orders of magnitude if we account for atmospheric deposition, road run-off and indoor fibres.

Existing wastewater treatment plants are not designed to remove these fibres; we recently reported that a well-designed advanced treatment plant could retain more than 98 per cent in the sludge and affecting the nutritive value of the sludge. Yet, the 2 per cent escape via treated water is still enormous; these tiny microfibers are toxicologically more relevant as it has the potential to cross the intestinal membrane for various organisms. The fact that a large quantity of microfibers found in wastewater also presents an ideal opportunity to stop the microfiber by implementing advanced treatment technologies.

However, we acknowledge the fact wastewater do contain other emerging threats such as pathogens, PFAS, antibiotic resistance etc. Therefore, advanced technologies should aim to treat or remove all the emerging contaminants together. Our team, recently developed a promising technology that can capture 100 per cent microfibers, PFAS and kill pathogens, awaiting further confirmation via field trials.

Last updated: 16 Sep 2020 2:15pm
Declared conflicts of interest:
Thava has two projects which are closely related to this study.
Professor Kevin Thomas is Director of the Queensland Alliance for Environmental Health Sciences at the University of Queensland

The publication is interesting for a number of reasons. It provides an estimate of the microfibre flux and pathways from apparel washing both globally and historically. It highlights how undeveloped our understanding of the environmental “plastics cycle” is and that in addition to synthetic fibres that is also leakage of other plastics into the biosphere from treated and untreated wastewater and biosolids. High consumption plastics such as polyethylene, polyvinyl chloride, PET, polypropylene and polystyrene also contribute to the loads emitted into the receiving environmental compartments. 

It is nice to see that the considerable uncertainty in such approaches being acknowledged and used to assess what parameters influence the predictions. We really need to improve our understanding of how plastics are cycling within the biosphere, what changes they are undergoing and where they end up. The field scientifically is very much in its infancy.

Last updated: 16 Sep 2020 2:11pm
Declared conflicts of interest:
None declared.

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