Microfibers and microplastics from textile materials: what are they and how to reduce them?

Thanks to two interesting studies*, reviewing the research on microfibres and microplastics, we try to shed light on a topic more and more preoccupying. The increase in the production of textile fibers in the last 20 years, in particular of synthetic ones, and the discoveries on the effects they have on man and the environment place more and more attention on the subject. Fiber fragments released from clothing and home textiles during washing, drying and use are considered a new source of environmental pollution and a health threat.

What are microfibres? What size are they?

“Microfibre” is a consolidated term in the textile industry to indicate fibers between 10 and 30 μm. The term “microfibers” is also used to indicate the fibrous material released during washing. It has been proposed to differentiate the term by calling these materials ‘fragments of fibres’, i.e. the fragments of fibers between 1 μm and 5 mm in size released from clothing and home textiles during washing, drying and use.

Therefore, “microfibres” in the textile industry actually indicates fibers between 10 and 30 micrometres, while what is released by clothing and home textiles is more correctly defined as a fragment of fibers and has dimensions between 1 μm and 5 millimetres.

What are microplastics?

Microplastics are fragments of synthetic fibers. Primary microplastic is released directly into the environment in the form of small plastic particles (less than 5mm in size) which include fiber fragments released during the domestic washing process. Other sources for primary microplastics include road markings, tire wear, marine coating and cosmetics. Secondary microplastics are the by-products of the natural erosion of larger plastic objects released into the environment.

Multiple steps in wastewater treatment plants can filter out up to 95% of fiber fragments. However, the remaining 5% of fiber fragments can end up in rivers and oceans and enter the food chain through:

• table salt;
• contaminated water;
• ingestion of marine creatures

causing adverse health effects.

They are not only a risk to our health, but also to that of marine creatures, threatening the functioning of their metabolic activities.

Additionally, fiber fragments can also impact health through inhalation (outdoor and indoor) and direct skin contact through personal care products, textiles, or indoor dust.

Where do fiber fragments mainly come from?

• From domestic washing of clothes
• From waste generated during textile production
• From discarded textiles
• From landfills near rivers and
• From domestic drainage

Considering domestic washing, how many microfibers are released?

The release of fiber fragments during washing varies from 100 to 300 mg per kg of washed fabric. So for a 7 kg washing machine load, it will range between 700 and 2100 mg in total. Making some estimates on a typical washing scheme (times, frequency, quantity) in developed countries, assuming that it is adopted in these countries by 1 billion people to wash their clothes, 14,400,000 kg of fragments of fibers is released to the environment every year. Any process that reduces fiber strength, including sanding, brushing, bleaching, has the potential to increase the release of fiber fragments in consecutive wet processes.

Various important parameters affect the release of fragments from textile fibers including type of fabric, weave/knit structure,  type and concentration of the detergent, temperature, pH, spin-speed of the spin cycle, duration of washing and processes drying.

Let’s consider for example he type of fiber.

The fiber fragments in the marine environment are classified as natural, cellulosic man-made and synthetic. The concentration of natural and cellulosic fiber fragments in the ocean is much higher than synthetic fiber fragments. Fabrics made from cotton and other cellulosic materials release more fiber fragments during the washing process than polyester fabrics. However, cotton, wool, silk and man-made cellulosic fibers such as bamboo, modal, tencel/lyocell are biodegradable compared to thermoplastic fibers in the marine environment. Polyester fibers are considered a greater threat to the environment than cotton because they have an extremely low biodegradation rate.

In general, natural and man-made cellulosic fibers degrade easily, however, the presence of dyes and chemicals for finishing the fabrics can reduce the biodegradation rate.

Most textile products are treated with various synthetic dyes. The presence of these chemicals can complicate the biodegradation of even natural fibers such as cotton.

In general, various functional additives have been applied to fibers of cellulose origin such as crease recovery, water/soil repellent, flame retardant, antimicrobial, and softeners. When fiber fragments are released into the marine environment, these chemicals and dyes integrate with the fiber fragment to create additional health hazards for aquatic creatures.

Let’s consider another variable, the detergent. How do they affect the release of microfibers?

There are conflicting studies. Some show that the use of detergent promotes the emission of fiber fragments compared to washing with water only. Others that the use of the cleaner has no significant impact on the release of microfiber. The apparent contradiction in the results is likely driven by differences in testing methodology (some studies use clean, often new or artificially aged, and homogenous wash loads of garments including one or a few garment types; others measure the release from solid consumer laundry).

Powder or liquid? Powder detergent generates a higher emission than liquid detergent. Powder detergents contain an inorganic component called zeolite, which is insoluble in water and causes more friction between the clothes and the washing machine with a higher chance of producing fiber fragments.

However, the chemical formulation of the detergent matters, whether it’s liquid or powder.

Generally, nonionic surfactant-containing detergent is easily soluble in water and works very well in hard water, but is more expensive than anionic surfactant.

The detergent industry uses various enzymes to speed up the washing process. These products are more expensive, good for washing and stain removal; according to some studies they attenuate the fiber fragments more during washing, according to others they increase the release.

Furthermore, the research results also show a significant reduction in the release of microfibre after the first cycles.

If what emerges from the various studies on the impact of detergent does not seem to give certainties, it is instead evident how much the temperature and quantity of water affect it.

How does the water temperature affect the microfibre release?

The release of fiber fragments increases with increasing washing temperature.

In some cases, a higher level of fiber fragments is released during the washing process at higher temperatures even without the addition of detergent or fabric softener.

To reduce the release of fiber fragments during washing, we can keep the washing temperature as low as possible (30°C).

Powder/liquid detergents based on non-ionic detergents seem preferable for washing clothes at lower temperatures with two advantages: (i) lower energy consumption during the washing process and (ii) lower release of fiber fragments.

What is the impact of the washing machine load and the amount of water on the release of microfibres?

In the washing machine, the garment-to-washing liquid ratio plays a critical role in the emission of fiber fragments. One study found the release of 65 mg of fiber fragments per kg of garment and increases to 125 mg of fiber fragments when the wash water is doubled. The higher volume of water increases the mechanical stress of the garments during the washing process.

We should try to wash with full loads but use an adequate amount of detergent and avoid overfilling the washing machine, because it could negatively impact the cleaning performance and lead to mechanical failure of the appliance.

Does the type of washing machine have an impact on microfibres?

A study on top-loading washing machines that work on the agitator principle (a central pivot that twists the clothes back and forth with the movement and rubs them against itself) release about 9 times more fiber fragments than to front-loading washing machines.

High-efficiency (top-load) washers generate significantly less microfiber shedding than traditional (top-load) washers, likely due to lower water fill volumes and therefore lower water/fabric ratio .

And does drying produce the release of microfibers?

I frammenti di fibra rilasciati durante il processo di lavaggio finiscono nelle acque reflue, mentre i frammenti di fibra rilasciati durante l’utilizzo dell’asciugatrice vengono raccolti sui filtri dell’aria e finiscono nei rifiuti solidi. Alcune delle fibre spezzate durante l’asciugatura sono attaccate in modo lasco alla superficie del tessuto e vengono rilasciate nell’aria quando sono indossate o rilasciate nell’acqua nel successivo processo di lavaggio. Al contrario, l’asciugatura all’aria non influenza significativamente il rilascio di frammenti di fibre.

Normalmente, la temperatura di asciugatura, la velocità di agitazione, il tempo di asciugatura sono i criteri principali che influenzano fortemente il rilascio di frammenti di fibre in un’asciugatrice.

The fiber fragments released during the washing process end up in the wastewater, while the fiber fragments released during the use of the dryer are collected on the air filters and end up in the solid waste. Some of the fibers broken down during drying are loosely attached to the surface of the fabric and are released into the air when worn or released into the water in the subsequent washing process. Conversely, atmospheric or air drying did not significantly affect the release of fiber fragments.

Normally, drying temperature, agitation speed, drying time are the main criteria which strongly influence the release of fiber fragments in a tumble dryer.

The characteristics of the fabric also have an impact.

The generation and release of fiber fragments are influenced by many aspects such as the type of fabric, geometry, yarn, and the entire manufacturing history (spinning, knitting or weaving processes, scouring, bleaching, dyeing , finishing and drying), in addiction to the physico-chemical properties of the fibres. Any factor that improves the physical interactions between fibers in the fabric structure reduces the release of fiber fragments during repeated washing and drying processes.

For example, woven polyester fabric emits higher fiber fragments than knitted polyester fabric.

The mechanical structure of the fibers deteriorates over time due to various parameters including exposure to sunlight, wear and washing. Exposure of fabrics to sunlight can increase the heat and accelerate the oxidation of the fibers and their gradual degradation. In addition to this, the fibers deteriorate due to mechanical stress, repeated washing cycles, abrasion and rubbing during wear, perspiration.

How can we limit the release of microfibers?

L’installazione di filtri per lavatrice per mitigare il problema è una possibile soluzione ma non si ha certezza che la filtrazione sia efficiente al 100%. Così il sacchetto che trattiene le microfibre (Guppy Friend). Si sta considerando la rimozione delle microfibre negli impianti di trattamento delle acque reflue, anche se è impegnativo.

I prodotti tessili dovrebbero essere utilizzati il più a lungo possibile prima che finiscano nelle discariche. La minimizzazione dei rifiuti tessili riduce anche il rilascio di frammenti di fibre dalle discariche. Dovremmo riciclare i tessuti il più possibile e creare dagli scarti tessili nuove fibre con tecniche adeguate.

Relativamente al rilascio di microfibre, i tessuti biologici provenienti da risorse rinnovabili dovrebbero essere preferiti a quelli sintetici a base di petrolio.

Il nostro comportamento di acquisto influenza fortemente la mitigazione dei frammenti di fibra. Gli attuali modelli di consumo portano a danni ambientali ed è necessaria maggiore consapevolezza della possibilità di ridurre dei frammenti di fibra dovuti ai processi di lavaggio domestici. I tessuti devono essere lavati in condizioni più miti con meno agitazione meccanica. Il rilascio di microfibra può essere notevolmente ridotto utilizzando cicli di lavaggio più freddi e più brevi, lavando carichi completi ma non eccessivamente colmi e preferendo lavatrici ad alta efficienza. Tali interventi hanno vantaggi anche sulla cura degli indumenti aumentandone la vita utile con benefici di impatto ambientale più ampi.

Contemporaneamente i brand dovrebbero avere più consapevolezza della mitigazione dei frammenti di fibre rispetto ai tipi di tessuto, fornendo i messaggi di avviso su ogni capo realizzato, scegliendo più consapevolmente i materiali e preferendo metodi di finissaggio e tintura più rispettosi dell’ambiente.

Installing filers  for washing machines is a possible solution to mitigate the problem, but there is no certainty that the filtration is 100% efficient. Thus the bag that holds the microfibers (Guppy Friend)). The removal of microfibers in wastewater treatment plants is being considered, although it is challenging.

Textile products should be used for as long as possible before they end up in landfills. Textile waste minimization also reduces the release of fiber fragments from landfills. We should recycle fabrics as much as possible and create new fibers from textile waste with suitable techniques.

Concerning the release of microfibres, bio-based fabrics from renewable resources should be preferred to oil-based synthetic ones.

Our purchasing behavior strongly influences the mitigation of fiber fragments. Current consumption patterns lead to environmental damage. Greater awareness of the possibility of reducing fiber fragments due to domestic washing processes is then needed. Fabrics should be washed under milder conditions with less mechanical agitation. Microfiber shedding can be significantly reduced by using cooler and shorter wash cycles, washing full but not overly full loads, and preferring high-efficiency washers. These interventions also have advantages on the care of garments, increasing their useful life with wider environmental impact benefits.

At the same time, brands should have more awareness of the mitigation of fiber fragments with respect of the types of fabric, providing warning messages on each garment, choosing materials more consciously and preferring more environmentally friendly finishing and dyeing methods.

 

*Sources:

Aravin Prince Periyasamy, Ali Tehrani-Bagha, A review on microplastic emission from textile materials and its reduction techniques, March 2022, Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, Finland, Science Direct

Lant et al., Microfiber release from real soiled consumer laundry and the impact of fabric care products and washing conditions, June 2020, Plos One

Photo: Mel Poole; Chris Curry; Moonstarious Project; Engin Akyurt; Chloe Skinner.