When textiles were first identified as a source of microplastic pollution, polyester fleece was rapidly singled out as a likely major contributor. But new research has revealed the presence of cotton and cellulosic microfibres, too. These are being found in places where they are not expected to be, going against a widely held assumption that natural and wood-based fibres are biodegradable. 

Cotton and cellulosic microfibres are being found in the Arctic, in the deep sea and in the air we breathe. A research study has even collected indigo-dyed cotton fibres in the far reaches of the Canadian north. It is not yet fully understood how they get there (it might be through the air), and it is not known how dangerous they are.

Should we be concerned? Cellulose is a natural material, it is the most abundant biopolymer on Earth, and its presence in waterways may come from sources other than textiles. But the microfibres being found are often of a modified type, known as anthropogenically modified cellulose, which is not a natural substance.

 Reports indicate that the presence of cotton and cellulosic microfibres is far from trivial. These two fibre families represent roughly 36% of all textile fibres produced annually but they made up nearly 80% of the microplastic particles collected in the Southern European deep seas. Polyester came in second (13%), followed by acrylic, polyamide, polyethylene and polypropylene. These are the findings of a research team led by Anna Sanchez Vidal at the University of Barcelona, Spain, in a paper published in 2018.

“Though polyester is the main fibre used in clothing, it is not the main fibre observed in oceans and in nature. Natural fibres are found in high proportions, even though it is believed they should biodegrade,” said Dr Richard Blackburn, associate professor and textiles technology group leader at the University of Leeds, speaking at a webinar organised by The Microfibre Consortium. 

Cellulose is the most abundant polymer in the world, and cotton a very pure form of cellulose, he says. Once mercerised, however, cotton fibres switch from cellulose type I to cellulose type II, a term used to describe manmade or semi-synthetic cellulosic fibres such as viscose and acetate. “It is not a naturally occurring fibre,” he says. Various chemical treatments including oxidisation, or bleaching, change the chemistry of the fibre, while dyes form covalent bonds that make cotton more crystalline. This, he says leads to a greater possibility for chemicals to leach from cotton than from a synthetic fibre.

In this relatively new field of research, there are many gaps in the science and literature. It is not known how microfibres adsorb or release chemicals in the environment, nor how chemicals affect biodegradation, and even less is known on their potential impact on the health of biota and animals as they travel through the food chain.

Research from North Carolina State University, funded by Cotton Incorporated, shows that the natural fibre biodegrades faster than synthetics in wastewater treatment plants, fresh water and salt water environments. “Once dyed and finished, cotton fibres still biodegrade, but sometimes at faster or slower rates, and more research is needed to better understand how textile chemistries accelerate or retard fibre degradation,” says Dr Jesse Daystar, chief sustainability officer for Cotton Incorporated.

Additionally, related research with University of North Carolina Wilmington is under way to better understand how accumulated cotton and polyester microfibres impact aquatic life. “The science surrounding the environmental impacts of microfibres is quickly evolving and Cotton Incorporated is committed to leading research to better understand and address the impact of apparel on the environment and reduce the environmental impact of our clothing.” Cotton Incorporated is also working with Ocean Wise to investigate ways to reduce microfibres shedding from textiles.

Phasing out polyester 

As more is known, it may become more difficult to brush the issue aside. Its emergence has led some companies in the denim industry to phase out polyester and seek alternatives for other synthetics. In Italy, Candiani is replacing fossil-fuel based fibres with plant-based ones, as seen with Coreva, a biodegradable stretch fibre made from natural rubber. Turkish mill Orta Anadolu is said to be rethinking its policy with regards to synthetic fibres.

French jeans brand Kaporal is addressing the issue by phasing out the chemicals that can leach from a fabric and generate microplastics, Beatrice Gonzadi, the brand’s sustainability manager, tells Inside Denim. It now sources recycled polyester from Unifi’s Repreve Our Ocean programme, which contributes to removing what are called ocean-bound plastics from the environment. The brand has created a Blue Impact label for its most eco-responsible products. “When we launched this range, in autumn/winter 2019, it had a single reference, and we now have 30% of the spring/summer 2021 collection that is sustainably designed,” she says. The brand’s goal is to reach 50%, and this, she notes, covers the entire sourcing and manufacturing process, including fabric, laundering and accessories.

Anthropogenically modified cellulose

But keeping synthetics to a minimum in collections is only part of the problem. The number of indigo-hued cellulosic microfibres that a research team at the University of Toronto found in its study prompted it to focus specifically on this source of pollution. The report, ‘The Widespread Environmental Footprint of Indigo Denim Microfibers from Blue Jeans’, was published in July 2020.

The research team found that textile microfibres made up 87% to 90% of the anthropogenic particles found in sediments collected in the Canadian Arctic Archipelago, Laurentian Great Lakes and shallow suburban lakes in southern Ontario. Among these particles, 21% to 51% were anthropogenically modified cellulose, and 40% to 57% were identified as indigo denim microfibres, representing 12% to 23% of all microfibres analysed.

These numbers led the authors to “hypothesise that blue jeans are a major source of introduction of anthropogenic cellulose microfibres into aquatic environments and serve as a tangible and potent indicator of anthropogenic pollution”.

Dyeing, along with other treatments applied to improve the durability or performance of fabrics, are thus believed to increase the synthetic content of the original raw material. “We found microplastic microfibres in sediments at 1500 metres. It takes them a long time to reach these depths, but our research suggests that they biodegrade at a slower rate than previously thought,” says Samantha Athey, key author of the paper. She does however concede that this could be due to the colder conditions found at these depths and that cellulosic fibres should break down faster than synthetic ones.

The team compared the microfibres collected in the environment with those shed by domestic laundering, with a series of three types of jeans: used, new and distressed models of Levi’s 501 Original Fit blue jeans made in 98% to 100% cotton. New jeans were found to release a significantly greater number of microfibres than used ones. “We found that the microparticles released during washing were virtually the same as fibres found in the environment,” says Ms Athey.

For her thesis, Ms Athey is pursuing research into domestic laundering as a source of textile microfibres and specifically seeking to identify the presence of unintentionally added contaminants, such as PCBs, plasticisers and flame retardants. “These legacy chemicals are no longer in use, but they are persistent and identified as Chemicals of Mutual Concern in the US and Canada. Fibres could be a conduit for them entering the environment,” she says.

The study of fibre fragmentation 

More research is needed to understand the many parameters that lead to fibre shedding, be it during manufacturing or home laundering. Not only is the issue complex, it is also difficult to quantify. There is as yet no globally recognised method of collecting and measuring the samples themselves. This has been the first focus of research for industry organisations looking to better understand the issue and determine its impact on manufacturing.

In 2018, five industry organisations created a Cross Industry Agreement (CIA) to tackle the microplastics issue. Members include trade bodies representing detergents (AISE) and synthetic fibre manufacturers (CIRFS) along with European outdoor (EOG), textiles (EURATEX) and sporting goods industry (FESI) associations. The CIA published an update on its research in January and announced that a harmonised test method had been developed and handed over to the European Committee for Standardisation (CEN) for use as an official standard.

New research suggests that home laundering may not be the predominant emission pathway, the CIA update says. It confirms that natural textile fibres make up a greater proportion of textile fibres sampled in the air than synthetic fibres, in a proportion of 70-75% for natural and regenerated cellulose materials and 17-30% for fibres of petrochemical origin. It intends to pursue research to better understand what triggers fibre fragmentation which should help find a solution to reduce the phenomenon.

The Microfibre Consortium (TMC), based in the UK, has been working on the issue since 2016. Its research first focused on the development of a collection and quantification protocol, but it is also looking into the mechanics of fibre fragmentation and is testing fabrics (200 to date) to build up a knowledge base. “We are collaborating with members to test more fabrics, in specific research areas, that will provide the consortium with the data needed to produce conclusive industry statements,” TMC managing director, Sophie Mather, said in an emailed statement. TMC members include some 40 companies among them Fast Retailing, Gap, H&M, Inditex, Primark and Target.

At a recent online forum with its research partner the University of Leeds, the organisation presented data that confirms the complex nature of fibre fragmentation. Contrary to the findings of earlier research papers, it says it is not related only to fibre composition, but to the interconnection of all elements that make up a textile. The results of its research will be presented at the TMC Fibre Fragmentation Summit to be held online from March 23 to April 1, 2021.

There is, as yet, no clear idea of the pathways the microparticles take nor how dangerous natural fibres are. “Anthropogenic modified cellulose may not be as persistent as synthetics, but we are finding them everywhere, in the air, in the sea, in animals, in biota. Until we can confirm they are not harmful, we should mitigate their release,” says Samantha Athey. She mentions laundering less and adding better filters to washing and drying machines. Some research suggests that adding a specific type of enzyme to wastewater treatment plants could be a solution. Many questions remain about these tiny particles and the debate goes beyond plastic.

French brand Kaporal Jeans identifies its most sustainable products as part of its Blue Impact label and has taken measures to remove virgin synthetics from its ranges and replace them with Unifi’s Our Ocean recycled polyester from ocean-bound plastics. 
PHOTO: Kaporal Jeans

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