RIS321186 Fast Fashion, snel eruit! bijlage 5

Polymer Degradation and Stability 199 (2022) 109901

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Polymer Degradation and Stability journal homepage: www.elsevier.com/locate/polymdegradstab

A review on microplastic emission from textile materials and its reduction techniques Aravin Prince Periyasamy∗, Ali Tehrani-Bagha Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, Espoo, 02150, Finland

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Article history: Received 27 January 2022 Revised 12 March 2022 Accepted 13 March 2022 Available online 17 March 2022 Keywords: Microplastics Microfibers Environmental pollution Domestic washing Emission Reduction techniques for microplastics Chemical finishing Textile

a b s t r a c t The production and consumption of textiles is continuously increasing due to the growth of population and fast fashion. Fiber fragments (1 μm–5 mm) released from garments and home textiles during washing, drying, and wearing are considered a new source of environmental pollution and health hazard. Fiber fragments can be ingested by aquatic animals and substantially threaten their metabolic activities. Small fiber fragments can also enter our food chain by the consumption of sea creatures, sea table salt, and drinking water. In this paper, we overview various important parameters on the release of fiber fragments from garments, and home textiles including the type of fabric, weaving/knitting structure, detergent type and concentration, temperature, pH, spin-speed, and duration of the washing and drying processes. The influence of various mechanical and chemical textile finishes on the release of fiber fragments is explained. Any process that reduces the strength of fibers and their interactions including sanding, brushing, bleaching can potentially increase the release of fiber fragments in consecutive wet processes. We highlight some of the most important environmental regulations on the release of microplastics and fiber fragments to the environment and provide a series of recommendations to reduce the impact. © 2022 The Author(s). Published by Elsevier Ltd.

This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

1. Introduction Plastics are synthetic macromolecule polymers that are used in the many different products, and they have become an integral part of human life [1,2]. Their cumulative plastic production rate has increased from 2 billion metric tons (BMT) in 1950 to over 8.3 BMT in 2017 and it is estimated to reach 34 BMT by 2050 [3]. The huge global demand for plastic materials is due to their high performance, low density, and versatile applications in textiles, automotive, construction, consumer goods, electrical & electronic devices, medical, and food & packaging industries [2]. Some of the thermoplastic materials (e.g., plastic bottles) are recycled and reused several times [4]. But a large proportion of single-use plastics are ended up in landfills, incinerators and contribute to environmental pollution [5]. The plastic particles have been spotted in various places including sea [6], coastlines [7], most remote islands [8], even in the deep sea [9] and Mount Everest [10]. Shopping bags, coffee cup lids, plastic water bottles, plastic forks and knives, and other single-use plastics account for the majority of plastics waste [2,11].

∗

Corresponding author. E-mail addresses: aravinprince.periyasamy@aalto.fi, aravinprincep@gmail.com (A.P. Periyasamy).

The global fiber production (synthetic and natural) has increased from 57 million metric tons (MMT) in 20 0 0 to 111 MMT in 2020 [12] and it is estimated to reach 145 MMT in 2030. Since 1995, synthetic fibers have dominated the textile market, overtaking cotton as the most popular fiber type, with synthetic fiber alone accounting for nearly 65% of worldwide output by 2020 [13,14]. Natural and synthetic fibers are used in a wide range of applications including garments [15], home textiles [16], filtration [17], and protective clothing [18]. Geographically, China and India hold the largest producers of synthetic fibers, accounting for 66% and 8% respectively [19]. Taiwan and the United States are ranked third and fourth, respectively, with each accounting for around 4% of worldwide synthetic fiber production. Aside from that, various manufacturing plants found in Oceania, the Middle East, and Africa [20]. Generally, the emission of microplastic into the aquatic environment are usually distinguished by their origin, namely primary and secondary. Primary microplastic is microplastics that are directly released into the environment as small plastic particles (<5 mm size) which include the fiber fragments released during the domestic washing process. Other sources for the primary microplastics comprise road markings, wear and tear of tyres, marine coatings, and cosmetics.

Secondary microplastics are the byproducts of the natural weathering of larger plastic objects that have been released into the environment [21]. Among the aforementioned

https://doi.org/10.1016/j.polymdegradstab.2022.109901 0141-3910/© 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

A.P. Periyasamy and A. Tehrani-Bagha

Polymer Degradation and Stability 199 (2022) 109901

Fig. 1. The number of publications related to microplastics since 20 0 0, retrieved using the words “microplastics”, “fiber fragment”, “microfibers in marine pollution”, “microplastics marine pollution”, “marine pollution or due to tiny plastic particles” and the words “microplastics or microplastic fibers” in the abstract. (Source: Scopus, date of search: July. 03.2021).

sources, garments are responsible for 35% of fiber fragments mitigation mainly during the washing cycles [22]. “Microfibers” is a well-established term in the textile industry as it indicates the fibers with 10–30 μm [23]. In addition, the fibrous materials which released during the laundering also called as microfibers. To differentiate these different meanings of microfibers in the textile industry as well in domestic washing, the microfiber consortium (TMC) [24] and American association of textile chemists and colorists (AATCC) have proposed to use the term “fiber fragments” instead [25]. In this paper, fiber fragments are defined as polymeric fibrous materials with a regular or irregular shape ranging from 1 μm to 5 mm [26]. The 2030 United Nations (UN) Agenda includes 17 Sustainable Development Goals (SDGs) intended to inspire and leading efforts to solve fundamental sustainability issues that humanity and the planet confront. Fiber fragments affects the clean water and sanitation (SDGs 6), marine environment (SDGs 14) and life in the land (SDGs 15) becomes threat due to the airborne microplastics. Fig. 1 shows exponential growth in the number of publications on microplastics and their emission since 2016.

The topic has gained so much importance due to the social awareness on the release of microplastic as well as the prominent scope for the research which connects the environmental effects of microplastics and their exposure to the marine environment. The source of fiber fragments from textiles and garments may get into the marine environment in different routes, which has been illustrated in Fig. 2. Based on the International Union for Conservation of Nature (IUCN) survey, the emission of fiber fragments to the environment is mainly due to garments made from synthetic fibers (34.8%), tires as a result of friction (28.3%) [27], road markings, landfilling, and other sources like fishing nets, etc. Most of the fiber fragments are commonly discharged into the environment after domestic washing. These tiny fibers may end up in the marine environment and enter the human food chain via sea table salt [28], contaminated water [29], and eating sea creatures [30].

1.1. Regulations In 1994, EU adopted a new regulation to prevent or reduce the impact of packaging and packaging waste on the environment (Council directive 94/62/EC) [31]. Although plastic shopping bags constitute product packaging within the meaning of that regulation, it does not include specific actions on the consumption of such bags. Beginning of 2015, a high level of consumption of plastic carrier bags littering environmental pollution and widespread problem in the water sources. Later, Directive (EU) 2015/720 suggested reducing the use and consumption of lightweight plastic shopping bags by the end of 2025 [32]. Council decision (EU) 2021/764 of 10 May 2021 [33], suggested controlling of water pollutants including plastics, fiber fragments and protection as well as restoration of water ecosystems to good ecological status. However, fiber fragments generation from domestic washing processes and various textile production sites are not included in these frameworks, therefore the situation is worsening and need better regulations. Many countries have started noticing the importance of the release of fiber fragments and they have regulations in place to reduce the impact of fiber fragments. As an example, the California state government recommended using a new fiber fragments filter system for washing machines.

This is an efficient way to minimize fiber fragments shedding from the domestic washing process [34]. Australian federal government collaborates with the washing machine manufacturers to place the microfiber filters in all new washing machines by 2030, so fiber fragments that move right into rivers from households across Australia are captured [35]. 1.2. Quantitative estimation of fiber fragments To identify the real release of fiber fragments, it is necessary to study the purchasing behavior of consumer. For USA consumers 2

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Polymer Degradation and Stability 199 (2022) 109901

Fig. 2. Main sources for the fiber fragments mitigation into the aquatic environment from domestic washing, textile industries, and garment waste/landfills and risks of fiber fragments for human and animal exposure, (WWTP- wastewater treatment plant).

buy one garment per week (53 garments per year), similarly, UK consumers buy 33 garments per year, perhaps, China 30, Japan 26, and India buys 5 garments per year [36]. Countries with larger population purchase the largest quantity of garments[36]. Klepp et al. [37] analyzed the washing frequency (N = 53,461 garments), Norwegian consumers, 39% of people wash every single wearing frequency. On other hand 14% of the population washes every 2 wearing frequency, 11% washes every 3 wearing frequency and 7% washes 4 wearing frequency. Garments like jeans, jackets, sweaters wash between multiple times worn it [38]. For the shedding of fiber fragments, consumers from United Kingdom (UK) observed 114 ± 66.8 mg of fiber fragments per kg of fabric [39] for typical washing conditions. Similarly, it is observed 100 mg of fiber fragments per kg of fabric releases in Switzerland [40]. UK consumers buy 33 garments per year [36], approximately consume 11 kgs (3 garments ≈ 1 kg) of garments per capita. As per the research output [39] (1 kg ≈ 114 mg fiber fragments emission), considering the release of 114 mg of fiber fragments per kg of garments after each washing cycle [40]. UK consumers buys 11 kg of garments and washing the dirty dresses twice a month, each person is responsible for the release of 114 mg × 11 kg × 12 months × 2 times=30,096 mg/year.

Reflect to the population (68,264,295 × 30,096 = 2.05 × 1012 mg), which is equivalent to 2054 t. This value represents only on the garments however, the consumers use non-garments like blankets, carpets, sportswear, gloves, caps, shopping bags. Therefore, it is expected to have higher mitigation level of the fiber fragments as it considers the garments and non-garments per capita. The main motto for providing these calculations/estimations is to create awareness to the public consumer. To obtain real figures and understand the impact of fiber fragments, it is essential to require the following information

2. Fiber fragments: potential health impacts Fiber fragments can be ingested by aquatic animals and substantially threaten their metabolic activities [41,42]. Fiber fragments expose three different ways to the human body. a. Inhalation (both indoor and outdoor), b. Ingestion (i.e., contaminated food and water) and c. Direct dermal contact of the particles through personal care products, textiles, or indoor dust triggering the health effects. It is difficult to analyze the influence of fiber fragments on human health as the lack of information on human exposure. 2.1. Inhalation The various textile production including spinning, weaving and processing, landfilling, waste incineration, and tumble drying of garments after washing are some of the major sources for the airborne fibrous fiber fragments [43,44] (Fig. 2). The ingestion of fiber fragments with inhalation is estimated to rise to 74,0 0 0 −121,0 0 0 particles per person in Vancouver, Canada [45]. Inhalation of poorly soluble particles and their impacts on the respiratory system is well explained in the mechanism of dust overloading [46,47]. The fiber fragments in outdoor and indoor environments are explained in Section 3.2. 2.2. Ingestion Ingestion of contaminated seafood, table salt, and drinking water is considered the major route for human exposure to fiber fragments [48]. Fig.

2 shows the possible pathways of fiber fragments to human health via the food chains. Fiber fragments may be found in various food including table salt [49,50], both tap and bottled drinking water [29,51–53], beer [54,55], honey [56,57] fruits/vegetables [58], and canned fish [59]. Fiber fragments consumption is estimated to be between 39,0 0 0 and 52,0 0 0 particles per person based on the American diet and lifestyle pattern [45]. However, the consumption varies for the different age groups,

Data for purchasing garments versus demographics. Data required for the type of garments, fiber types, fabric types. • Data for washing or tumble drying per person/family. • •

3

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Polymer Degradation and Stability 199 (2022) 109901

male, females, geographical conditions, and their food diets and lifestyles.

biodegradation. Therefore, the dye molecule chemically bonded to the surface of fibers and slow down the biodegradation of fibers. Generally, several functional additives were applied to the cellulosic origin fibers such as crease recovery, water/soil repellency, flame retardancy, antimicrobial, and softeners. As these finishes provide better properties to the wearers, however, it strongly affects their biodegradability in the marine environment [67,75]. Zambrano et al. [67] determined the biodegradation studies on dyeing (C.I. Reactive Blue 19) and various textile finishing including softener (modified amino-functional silicone), water repellent (non- Perfluorooctanoic acid fluorochemical), durable press finishes (Dimethylol dihydroxyethyleneurea). Results from this study evidenced that the finishes have strongly affected the biodegradation of cotton within the period of the experiment (102 days), the results are as follows; softener (89.6% biodegradation) > water repellent (74.9% biodegradation) > dyed (66.2% biodegradation) > durable press (63.0% biodegradation). The biodegradation of cotton mainly depends on the oxygen uptake versus the theoretical oxygen demand. Among the different finishes, durable press finishes consume less oxygen and are followed by the lowest degradation.

This is due to the chemical bond between the fiber and respective chemicals, resulting in slow down the biodegradation of fibers. On other hand, most of the dyes, pigments, chemicals, and auxiliaries used in the textile industry having mutagenic potentiality [76], some of the dyes containing Azure-B as it severely affects the deoxyribonucleic acid (DNA) [77–79]. For instance, cellulosic fibers are predominantly colored with reactive dyes, particularly anthraquinone containing reactive dyes considered as acute toxicity [80] and mutagenicity [81,82]. In addition, commonly used dyes for dyeing polyester including disperse red 1 [83], disperse orange 1 [83] are also considered as toxicity. When the fiber fragments released to the marine environment, these chemicals and dyes integrate with fiber fragment to create additional health hazardous to the aquatic animals.

2.3. Dermal contact The significance of dermal contact with fiber fragments is less towards exposure though (<100 nm) could transverse the dermal barrier as it is speculated. There is a possibility that the fiber fragments can pass through skin membrane, especially from wounds, sweat glands [60]. Nonetheless, it should not be abandoned without evidence that the fiber fragments can cross the dermal barrier and cause toxicity. 3. Fiber fragments from domestic washing The share of synthetic fibers in garments and home textiles has constantly increased since their introduction in the market because synthetic fibers (e.g., polyester (PET), polyamide (PA), acrylic (PAN), and polypropylene (PP)) are generally durable, strong, and affordable [61]. Synthetic fibers such as PET are commonly used in textile and clothing separately or in blend with cellulose fibers to enhance mechanical properties and durability. The growth of the fashion industry and textile clothing depend heavily on synthetic fibers as can be seen from the global fiber market [62]. The fiber fragments in the marine environment are classified as either natural or synthetic. The concentration of cellulosic fiber fragments in the ocean is much higher than the synthetic fiber fragments [63].

Nevertheless, natural fibers like cotton, wool, silk and man-made cellulosic fiber like bamboo, modal, tencel/lyocell are biodegraded as compared to the thermoplastic fibers in the marine environment [64]. Currently, the natural and man-made cellulosic fibers are floating on the oceans since they were disposed during the previous decade [63]. Generally, natural, and man-made cellulosic fibers are degrading easily, however, the presence of dyes and textile finishing chemicals can reduce their rate of biodegradation [64–67]. Due to the high production/consumption rate of PET fibers (over 70% of the global fiber production) [62], PET fiber fragments are commonly found in environment [68] and the contamination in the ocean in the order of, PET [69] > PAN [69] > PP [70]> PA [70]. The primary sources of fiber fragments release to the environment are domestic washing of garments, waste generated during textile production, discarded textiles, landfills situated near the riverside and domestic drainage. Apart from regular garments, various home textiles products such as curtains, carpets, mattresses, pillows, and tablecloths contribute noticeably to the release of fiber fragments. Fiber fragments have been accumulated in rivers, seas, and oceans over the past years, and they have turned into environmental pollutants endangering small and large microorganisms.

The reports show that the fiber fragments are floating on the ocean surface [71] and the level of contaminations is exponentially increasing [69], due to the higher consumption, landfilling of textiles and garment wastes [27].

3.2. Domestic washings and their influence on the release of fiber fragment Fiber fragments are mainly released into water/wastewater from domestic washing machines and discarded textiles from landfills. There have been limited quantitative research studies on this topic, as most of the works used an indirect method to calculate the release of fiber fragments [84–87]. Napper et al. [84] used a commercial washing machine to determine the release of fiber fragments from three different synthetic garments (100% PET, 100% PAN, and 65% polyester/35% cotton blend. The garments were washed in the presence/absence of a selected detergent and conditioner at two different temperatures (30 °C and 40 °C). During the washing process of 6 kg garments, 728,789 (100% PAN) and 496,030 (100% PET), 137,951 (65% polyester/35% cotton) fiber fragments are emitted. Belzagui et al. [88] analyzed the fiber fragments emission on fabrics made with 100% PET, 70% PAN/30% PA6, and 80% PET/ 20% elastane (PE) blends. The results showed that the release of fiber fragments from the PAN/PA blended fabric was the highest. It was concluded that the structure of garments influenced the fiber fragments shedding, whereas the fluffy garments (i.e., made from 100% PET woven fabrics) released more fiber fragments than the nonfluffy garments (i.e., made from 90% PET/20% elastane and 70% PAN/30% PA).

3.1. Effect of dyeing/finishing process and their relationship on fiber fragments Polyester, cellulose, and wool are used in the garment industry as it provides comfort, durability to the consumers [23]. The coloration of these fibers involves various synthetic dyes namely disperse, reactive, acid, metal complex, and direct dyes [72]. Most of textile dyes are intentional designed to be resistance against mild oxidation and reduction processes to tolerate washing cycles and sunlight degradation [73,74]. These dyes from different classes (Disperse, Reactive, Direct, Acid) remain on the fibers fragments and they may be released to the environment by hydrolysis and

3.2.1. Influence of detergent and softener The use of detergent enhanced the emission of fiber fragments, and it confirmed by previous experiments [40,84,85,87,89]. For do4

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mestic washing, two types of detergents are often used (powder and liquid). Powder detergent generates greater emission than liquid detergent, according to Chiweshe and Crews [90] and De Falco et al. [85]. However, powder detergents contain an inorganic component called zeolite, which is insoluble in water and causes more friction between the clothing and the machines due to the increased chances of fiber fragment production. Alkali-based detergents, in general, hydrolyze fiber surfaces (e.g., PET) and facilitate the release of fiber fragments. So, it can be concluded that the powder detergent plays a vital role in the shedding of fiber fragments during domestic washing, however, the chemical formulation in the detergent is important rather than the liquid or powder detergent. In another study, detergent reduces the mass of particles released from synthetic garments [91] thus the detergent behavior influence, as the detergent contains the surfactant which reduces the surface tension and lubricating the fibers to protect them from releases. Furthermore, given the existing lack of knowledge about fiber affinity for water and releases, more study is needed to determine the impact of detergent chemical action and methodology type.

Furthermore, while counting the fiber fragments emission when the garment was washed with powder-based detergent cause a substantial error (underestimation) due to the entanglement of several fiber fragments [85], this due to the insoluble nature of inorganic substances. Fabric softeners, diminish the release of fiber fragments [84], after washing by more than 35% [85]; yet, some research claim that fabric softeners have no effect on the emission of fiber fragments [40,92]. In the washing machine, the garment-to-washing-liquid ratio plays a critical role in the emission of fiber fragments [93], authors observed 65 mg of fiber fragments per kg of garment and it increases to 125 mg of fiber fragments when the wash water is used twice the amount. In addition, the higher water volume increases the mechanical stress to the garments during the washing process. New additives (i.e., builders and softeners) for washing liquor were studied by Piñol et al. [94] to reduce fiber fragments emissions. The main function of the builders is to chelate the positive ions (Ca2+, Mg+ ) from the hard water during the washing process [95]. The soil and stain are removed efficiently using anionic surfactants, yet it is sensitive to multivalent ions present in the hard water. The anionic surfactants are bonded by positive ions causing precipitation which deposits on the fabric surface.

Besides, the calcium ion possesses the property of acting as “glue” amid the stain and the fabric surface to make it harder to remove, therefore, it reduces the cleaning efficiency. Perhaps, it is required more quantity of detergents or more friction to achieve the expected cleaning which is directly proportional to the favoring of fiber fragments releases. Generally, the detergent containing nonionic surfactant is easily soluble in water and it works very well in hard water however it is expensive as compared to the anionic surfactant. The hydrophilic part of nonionic detergents often consists of polyoxyethylene groups which can lubricate garments and reduce the release of fiber fragments [96]. The detergent industry uses different enzymes like cellulases, proteases, lipases, and amylases were added with the detergent to speed up the washing process, particularly it improves the stain removal efficiency [97]. Enzymes like cellulase break down the cellulosic fiber into monosaccharides [98] by simple hydrolysis of β −1,4-linkages present in cellulosic fibers. Therefore, the cellulasecontaining detergents break the fibers from the surface of the fabric, resulting in the increased mitigation of fiber fragments during the washing cycles.

Generally, the enzymes associated with detergents are expensive, good for washing and removals of stains, however, it mitigates more fiber fragments during washing.

3.2.2. Influence of temperature and duration Several research works have shown that the release of fiber fragments during laundry increases by temperature [99]. The release of fiber fragments is increased with increasing the washing temperature, at 30 °C, it can be observed 2,877,278 fiber fragments are released per one kilogram of jeans. Further, it increases to 3,121,692, and 3,283,341 fiber fragments per kilogram of PET jeans when washing temperature 45 °C, and 60 °C, respectively. These results are observed in constant washing treatment [100,101]. In some cases, a higher level of fiber fragments is released during the washing process at higher temperatures even without adding any detergent or conditioner [99]. Hernandez et al. [40] observed that there is no statistical difference in the fiber fragments releases with different washing temperatures (25, 40, 60, and 80 °C) without the addition of detergent and conditioner. Similar results were obtained, where the PET garments released higher fiber fragments at higher washing temperature [102], this was attributed to the surface hydrolysis of PET [103]. Henceforth, to reduce the release of fiber fragments during washing, one can keep the washing temperature low as possible (i.e., 30 °C).

The washing process is often conducted at temperatures between 30 and 90 °C that depend on the type of garments, the level of contamination, the nature of constituent fibers (e.g., cotton or PET), and the type of detergents. On contrary to anionic detergents, nonionic detergents are generally soluble in cold water, and they are not sensitive to the presence of water hardness (e.g., Ca2+ , Mg2+ ) [95]. So, washing powder/liquid based on nonionic detergents are preferable for washing clothes at lower temperatures. This has two advantages: (i) lower energy consumption during the washing process, and (ii) lower release of fiber fragments. The formulation of suitable detergents, washing temperature, pH, and duration can be slightly different for various natural or synthetic fibers. The combined effects of washing temperature and detergent increase the swelling action of cellulosic fibers. In the swollen state of cellulosic fibers, there is a higher possibility for the penetration of water in the amorphous regions and reduce the intermolecular interactions between the fibers. As an example, viscose fibers get weaker when they are wet due to the interruption of hydrogen bonds between the cellulose chains [104]. The swelling of cellulosic fibers increases the free space for the mobilization of the shattered fibers from the fabric structure.

Due to the sheer force under washing machine, the fuzz formation is enhanced as the swollen fabric structure and leads shedding capacity of the fabrics, and the mechanical action of the washing machine and tumble dryers break this fuzz on the surface of the fabrics and starts emits (Fig. 3). Synthetic fibers like PET are highly crystalline, mechanically tough, hydrophobic, and do not swell significantly under a washing temperature of less than 60 °C. At higher washing temperatures, there is a possibility for fiber fragments discharge [105–108]. However, the swelling is not a serious issue for hydrophobic fibers like PET as compared to the cellulosic fiber under higher temperatures. 3.2.3. Influence of drying on fiber fragments releases In cold countries, a tumble dryer is often used for drying clothes after each laundry. It was observed in one of the studies that the release of fiber fragments from a PET blanket was around 0.0014 wt.% for the washing process and 0.00359 wt.% for the drying process (approximately 3.5 times higher) [92]. The fiber fragments released during the washing process end up in wastewater while the fiber fragments released during the tumble drying are collected on air filters and end up in solid waste. Some of the broken fibers during the tumble drying are loosely attached to the surface of the fabric and are released to air when they are worn 5

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Polymer Degradation and Stability 199 (2022) 109901

Fig. 3. Schematic representation for the fiber fragments generation in the fabrics made from polyester and cellulosic origin.

or released to water in the subsequent washing process [109]. In contrast, atmospheric drying or air drying does not significantly influence the release of fiber fragments [40]. Normally, drying temperature, rate of agitation, time of the drying is major criteria that strongly affect the release of fiber fragments in a tumble dryer. So, the recommendation is to use a static drying process rather than a tumble dryer if possible, at a relatively lower temperature and shorter period.

and forcing around the washing drum, therefore, the garments move to-and-fro providing scrub-like washing. In pulsator, water pulse through the garments, resulting in gentle washing effect. Hartline et al. [110] reported that the top-loading washing machine releases approximately 9 times more fiber fragments than the front-loading machine. Perhaps, the top-loading washing machine has stronger friction with metal perforated baskets. The garments are constantly in contact with metal parts, apart from that the agitation speed of the machine also influences the higher rate of fiber fragments releases.

3.2.4. Effect of washing machines Commercially there are two types of washing machines namely front loading and top loading were used in the domestic consumers, perhaps it may work either through pulsator or agitator principle [99]. Most of the top loading washing machines works under agitator principle, where it creates the motion by shaking

3.2.5. Effect of textile properties The generation and release of fiber fragments are influenced by many aspects such as fabric type, geometry (woven, knit, or nonwoven), yarn types (twist, evenness, hairiness, staple fiber, fila6

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ment, and the number of fibers per cross-section), processing history (spinning, knitting, or weaving, scouring, bleaching, dyeing, finishing, and drying processes), and physicochemical properties of the fibers [40,111]. The formation and release of fiber fragments is mainly due to the breakage of the short-staple fibers. Generally, it is difficult to obtain the yarn evenness for the fibers from the natural origin as the staple length varies. The natural fibers consist of short-staple fibers (length between 2.5 and 6.0 cm) and long-staple fibers (length > 6.0 cm) [112–114]. Nevertheless, combed yarn (i.e., combing process are carried out to improve the yarn quality by removing short fibers) certainly provides uniformity, as it removes most of the short-staple fibers. For staple yarn productions, synthetic fibers like PET, PA, PAN, and regenerated fibers like Lyocell, Viscose rayon are generally cut into staple fibers with appropriate length (typically less than 32 mm) [114–118]. The origins of fuzz development include the cross-sectional shape, thickness, stiffness, yarn hairiness, friction, and abrasion resistance of the fibers [119– 123]. During washing, short-staple fibers (also known as protruding fibers) and a large number of fiber fragments are emitted due to enhanced hairiness in the yarn [124], which further possible to form fuzz (Fig. 3).

The pilling formation is mainly due to the surface rupture of staple fibers under mechanical actions. Fuzz formation initiates the pilling formation in the fabric [123,125] which detaches from the surface due to the mechanical action during the washing and wearing cycles. The pill formation delivers a similar mechanism for both synthetic fibers like polyester and cellulosic fibers like cotton/lyocell, the predicted mechanism for the fiber fragments generations is shown in Fig. 3. As per the reference [90], while washing the synthetic garments, the fabric conditioners increase the possibilities of pill formation. The percentage of various components in the yarn or fabric construction (e.g., in blend fibers/yarns/fabrics) play a major role in the fiber fragments generation/release during laundering. In contrast, fabrics made from 100% synthetic or synthetic blends release higher fiber fragments than the natural fibers, this is due to the friction between the fibers during yarn formation [99,126]. Generally, synthetic fibers do not have the natural convolution or crimp. Due to the mechanical action by washing and tumble dryer, small fiber fragments can be released from the main fibers due to the weak fiber-fiber interactions [92].

The fabric and yarn structure strongly influences the fiber fragments generations, in this case, the fleece and pile structure release significantly higher fiber fragments than the plain-woven fabrics [70,85,92], this is due to the open structure of loops or protruding fibers in the surface of fleece fabric [39,127]. The effect of fabric type on the release of fiber fragments has been also investigated by De Falco et al. [102]. The release of fiber fragments was in the order of; 100% PET woven blouse < 100% PET knitted t-shirt < 100% PET knitted fabric < 50% PET/50% cotton knitted sweatshirt. 100% PET knitted fabric and 50% PET/50% cotton knitted sweatshirts were made from staple yarns and no significant difference in the release of fiber fragments was observed among them [102]. However, fabrics made from continuous filament fibers release fewer fiber fragments into the air than the fabrics made from short-staple fibers [102]. The highest emission of fiber fragments was observed for 50% PET/50% cotton knitted sweatshirts in both the medium as 80% (in water) and 97% (in the air). De Falco et al. [85] observed that the woven polyester fabric emits higher fiber fragments than the knitted polyester fabric. Generally, woven fabric has a rigid structure, resulting the surface rupture is much higher as compared to the knitted fabric as it provides elasticity during the mechanical action.

Additionally, the yarn used for knitted polyester fabric contains less hairiness (Fig. 4a) as compared to the woven fabric. Apart from that, continuous fila-

ments were used in the yarn which is further used to produce the knitted fabric (Fig. 4a). Microfleece is a kind of knitted terry fabric that is napped and/or cut by the mechanical process. In contrast, single yarn is used in the weft (Fig. 4b), and doubled yarn is used for warp (Fig. 4c). These microfleeces released significantly higher fiber fragments than single jersey knitted fabrics [70]. Aged garments approximately release 25% higher fiber fragments than new garments [110]. The mechanical structure of fibers deteriorates over time due to various parameters including sunlight exposure, wear, and washing. The exposure of fabrics to sunlight with a wide spectrum of wavelength covering UV, visible, and IR regions can increase the heat and accelerate the oxidation of fibers and their gradual degradation. Other than that, fibers deteriorate due to mechanical stress, repeated wash cycles, abrasion, and friction during the wear, sweating, exposure to gasses like CO2 , NO, and NO2 . The mechanical actions during the washing process can break down staple fibers and separate them from the yarn [126]. Nevertheless, parameters like the twist of yarns, breaking strength, elongation, bending rigidity, friction, and the softness of the yarn play a vital role in the emission of fiber fragments [70,102,126,128]. Yarn hairiness is a measure of the length of protruding fibers from the yarn surface.

Yarn hairiness provides the fuzz formation as it further forms the pilling in the fabric structure which results in the discharge of fiber fragments. Yarn properties such as unevenness indicating the higher coefficient of variation percentages leading to the poor appearance and lower yarn strength [129–132]. Based on earlier studies the yarns produced from finer and longer fibers have lower unevenness and hairiness [133,134]. The yarn hairiness depends on the twisting levels and the diameter of the yarn, and the rigidity, elongation, tenacity, and length of the fibers [120,129,132,135,136]. In the constant washing conditions [126] (i.e., washing temperature 44 °C, 25 metal balls with constant quantity of detergent and time), it is observed that the mitigation of fiber fragments follows the order as 100% cotton spun yarn > 100% PET spun yarns > 100% viscose-rayon spun yarns > 50/50 polyester/cotton spun yarns. This is due to the lower uniformity in the fiber length in the cotton yarns. For polyester and viscose rayon, static charge, and cohesion between fibers in the yarn structure is very high. In addition, the low wet strength of viscose rayon causes higher fiber fragments generation. Polyester yarns have comparatively similar hairiness to the viscose rayon since the fibers are much stronger, which does not emit a huge fiber fragments count during laundering [126].

Table 1 provides a detailed summary of the textile properties and their influence on fiber fragments reduction. Table 2 describes the important parameters to be considered for reducing the release of fiber fragments during the washing and drying processes. 3.3. Fiber fragments in air Dris et al. [137,138] investigations suggest that the traces of fiber fragments can be found in the open-air environment and to a larger extent indoor. The sources of fiber fragments are the windblown debris from sewage sludge, municipal effluent treatment plants, textile production sites, and landfill sites, the airborne fiber fragments from nearby above locations are quite common due to the fiber fragment density larger than that of air (e.g., for polyester, approximately 1.39 g cm−3 at sea level and 15 °C) [139–141]. Particles of three different synthetic polymers (PE, PP, and PET) were detected in the outdoor environment between 175 and 313 particles/m2 /day in Dongguan city in China [142]. Shanghai people daily inhale approximately about 21 particles of fiber fragments from open air [143]. In another study, out of 114 lung cancer patients 99 patients were observed to have fibers in their lungs 7

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Polymer Degradation and Stability 199 (2022) 109901

Fig. 4. Optical microscope images of (a) continuous polyester yarn from PEP; (b) a staple polyester weft yarn, (c) a staple polyester warp yarn from PEC; (d) a staple polypropylene weft yarn, (e) a staple polypropylene warp yarn from PP, (reprinted from [86] with kind permission of Elsevier publications). Table 1 Desirable textile properties for fiber fragments reduction. Parameter

Preference

Notes

Fiber

Staple fiber Filament

Yarn

Finer yarn count (linear density) Use of combed yarn

Higher staple length is preferable to reduce the fiber fragments emission. Continuous filaments with higher tenacity with higher elongation reduce the release of fiber fragments Finer yarn has more elongation than the coarser. Finer yarn has fewer short fibers Combed yarns are more uniform than carded and open-end spun yarn. Combed yarn are less hairy fibers, contains longer fiber in ratio resulting in the reduction of fiber fragments emission. Usually, higher twist higher the yarn strength and reduces the fiber fragments More floating weave structure (satin, 3/1 twill) has higher fiber fragments emission. Higher cover factor increases the fiber/fiber interaction and reduces the fiber fragments emission. Fabric having higher abrasion resistance properties could reduce the emission of fiber fragments. Bio-polishing treatment on cellulosic-based fibers has a significant reduction of fuzz fibers. Singeing processes reduce the protruding fibers which have a strong impact on the reduction of fiber fragments emission. Another mechanical finishing process like brushing and raising increases the fiber fragments emission. Complete sealing is required on the edges of garments to ensure the reduction of fiber fragments emission. Mechanical damages due to the contact of sewing needle with fibers and the friction between sewing thread and fabric can increase the release of fiber fragments

Fabric

Higher twist Fabric structure

Fabric finishing

Fabric physical properties Enzymatic finishing Mechanical finishing

Garments

Sealing the edges Sewing threads

Table 2 Parameters to be considered for reducing the release of fiber fragments during washing and drying processes. Parameter

Preference

Notes

Wash temperature

Lower

Detergent formulation

Lower concentration and better formulation

Spin-speed

Lower

Wash duration Washing machine Drying

Shorter Front-loading outdoor static drying

The oxidation and degradation of fibers in washing medium is increased by temperature. Detergents wet the surfaces and the slippage of fibers from yarns and fabrics increases at higher temperature. So, high temp. should be generally avoided Liquid detergents based on nonionic detergents rather than formulations containing anionic detergents with inorganic salts and abrasives are preferable. The formulation should show its high washing efficiency at a lower temp and high-water hardness. High rotational speed and agitation increase the friction between garments and solid surfaces and the release of fiber fragments Long washing cycles increase the chance of fiber fragment emission. Top loading washing machine release 9 times more than the front-loading washing machine. Tumble drying and high temperature increase noticeably the release of fiber fragments

8

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which is equivalent to 87%. Further, it was observed that the fiber dimension to be 50 μm length and likely to spread longer than 250 μm [144]. The inhaled fibers stay in the lungs for a long time, and they may turn into a life threat. We should also note that these fibers may also contain toxic dyes, heavy metals, or other harmful additives [145,146]. Dris et al. [137] found 1586 - 11,130 fibers/day/m2 in the indoor environment in a private apartment located 10 km away from Paris city center. The air samples were collected inside the private apartment at 1.2 m height which is the standard breathing height of an adult. Quartz fiber GF/A Whatman filters were used to collect the deposited fiber fragments. Overall, 1–60 fibers/m3 fiber fragments were observed indoors compared with a considerably lower amount of 0.3 to 1.5 fibers/m3 outdoor. 67% of detected fibers were cellulosic and the rest of them were synthetic fibers such as PP which is predominantly used in carpets, sofa, and other furnishings.

to the abrasion during wear and washing, these polymeric films have possibilities to release the micro sized particles addition to the fiber fragments. Several studies have been conducted to investigate the mitigating effect of a variety of typical finishing treatments on fiber fragments. The chemical treatment can reduce the protruding fibers with strong linkage to the surface of the textile ensures the reduction of fiber fragments releases [67,75]. There are different resins namely acrylic resins, Polyurethane resins and silicone emulsion were applied on the different synthetic fabric through padding and exhaustion methods [94]. Acrylic resins show a good pilling resistance out of selected auxiliaries with all the fabrics (PET, PP, PAN and PA), this trend was observed in both woven and knitted fabrics. On other hand, the fiber fragments emission from the acrylic resin finished fabric shows less than other finished fabric. Similarly, softness was higher in the fabric due to silicon emulsion than the pristine PET fabric, yet it is noted that pilling was worse. There was a significant reduction in fiber fragments release with silicon emulsion finished fabric over other finishes as shown by the laundry tests. This is primarily caused due to the friction reduction between fabric and detergent during the washing process since silicon finish generates a soft surface of PET fabric.

However, we did not find any report on the durability of these chemical finishes to see if these are permanent or temporarily solutions for the release of fiber fragments.

4. Reduction techniques for fiber emission 4.1. Mechanical finishing Mechanical finishes like singeing or calendaring reduce the fiber fragments releases. Singeing is the process of removing the loose hairy fibers protruding from the fabric surface by controlled open flame, and calendaring is the process where the fabric is compressed by passing between two or more rollers under controlled conditions of time, temperature, and pressure [147]. Sanforizing and heat setting treatments are conducted to shrink and fix the fabric in both warp and weft directions. Mechanical finishes are usually semi-durable, and they cannot protect the fabric against the release of fiber fragments after few washing cycles. The protrusion of fibers on the fabric surface appears after few washing cycles. Shearing and brushing is a mechanical surface treatment that makes the fabric soft and bulky. In the shearing process, the surface fibers (protruding fibers) are uniformly cut with the desired length. The brushing process helps to pull the fiber from the yarn structure. In both finishes, there is a significant physical change in the fabric surface structure which enhances the release of fiber fragments (Fig. 5). Usually, a higher release of fiber fragments during the first few washes is due to the release of entrapped fiber fragments generated during the mechanical finishing stage [148].

Finishing with pectin. De Falco [152] reduced the fiber fragments release on the polyamide (PA) fabric by simple pectin-based finishing treatment. It was achieved by two step processes, as i) synthesis of PEC- Glycidyl methacrylate (GMA, 97%) and ii) grafting of PEC-GMA on the fabric (PEC-GMA-PA). Based on the sustainable concerns, pectin was selected further due to its abundant availability, and its ability to react with textiles. An emulsion mixture was created by treating PEC with GMA initially and further the PEC-GMA emulsion grafts on the PA fabric. The chemistry between PEC-GMA was well explained by Maior et al. [153]. The pristine-PA and PEC-GMA-PA fabrics were washed for 45 min at 40 °C using a commercial detergent (ariel) according to ISO 105-C06:2010 standard test method. The results represent that the pristine-PA fabric emits fiber fragments of 12 ± 222 μm length, 18 ± 3 μm mean diameter, and 0.359 g fiber fragments per kg of wash. Contrastingly, PEC-GMA-PA mitigates fiber fragments of 550 ± 384 μm length, 16 ± 4 μm mean diameter, and 0.058 g fiber fragments per kg of fabric, which is a 90% reduction of fiber fragments.

4.2. Chemical finishing

Finishing with biodegradable polymers. The biodegradable polymers like polylactic acid (PLA) and Poly (butylene succinate-co-butylene adipate) (PBSA) were coated on the PA fabric by electrofluidodynamic (EFD) coating method [154]. The finished fabric shows a strong reduction (90%) of fiber fragments releases as compared to the pristine fabric. The advantages of the EFD treatment are: (a) homogeneity of coating, (b)possible to coat the nano-sized particles, and (c) finishing the fabric surface without losing the basic properties. PLA and PBSA finished PA fabric release the fiber fragments per gram of washed fabric as 428 ± 92 and 456 ± 120, respectively. Perhaps, 3966 ± 1425 fiber fragments per gram of fabric are emitted by the pristine PA fabric. Further, 90% reduction in fiber fragments shedding from the PA fabric are reported by this research rather than the previous research (pectin-based finishing) [152]. A uniform surface coating has been created on the fabric by the finishing process where it protects the material from mechanical and chemical reactions during the laundering process. After laundering, pristine PA fabric could emit 0.35 g/kg of fiber fragments as an estimated weight. Whereas finished PA fabric with PLA and PBSA was observed 63.4 and 76.8% fewer fiber fragments release upon the PA fabric, respectively.

However, the finishing process reduces 15–20% of the mechanical properties [154]. Addition-

4.2.1. Enzymatic treatment The issue of fiber fragments releases can be resolved by the help of surface modifications of textiles. Biopolishing treatments with garments made from cellulose fibers resulting the removal of fibrils or microfibrils from surfaces. As, the presence of fibrils caused by pilling formation on garments looks appear badly. Enzymatic removal of fibrils preserves the original color, resulting in softer [149,150]. Sankarraj and Nallathambi [151], cellulase that has been immobilized has a powerful impact on projecting fibers on the surface of cotton garments (see Fig. 6). In comparison to the pristine fabric, the projecting fibers from the surface of the fabric have been decreased after the enzymatic treatment. However, there is no data related to the protrusion of fibers form after wash and wear cycles versus durability for the enzymatic treatment. 4.2.2. Coating and chemical finishing Textile finishing and coating with a series of chemicals including silicone, polyurethane, acrylic polymers can reduce the release of fiber fragments. These polymers form a film on the surface of fibers and protect them against abrasion mechanical distress. Due 9

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Polymer Degradation and Stability 199 (2022) 109901

Fig. 5. Various mechanical finishing and their impact of fiber fragments emission during domestic washing.

Fig. 6. Microscopical image of protruding fibers on pristine fabric surface (a) fabric treated with soluble cellulase (b) and immobilized cellulase treated fabric (c), (reprinted from [151], with kind of Elsevier publications).

ally, the coating is durable at least for 5 washing cycles and PLA provides more durability than the PBSA coatings.

ties to release the plastic micro particles. Acrylic silicon emulsion, Pectin, PLA and PBSA based finish usage signify to be effective. Nevertheless, it is essential to choose eco-friendly chemicals and polymers for the process of sustainable finishing to avoid further polluting the environment. Yet, there are numerous possibilities like enzyme treatment, plasma treatment, and other biopolymers that were not ever tried so far and providing the future scope for the researchers.

Finishing with chitosan. The fiber fragments shedding from chitosan finished PET fabric was analyzed by Piñol et al. [94]. There are 3047 fiber fragments per gram of fabric were released by the pristine PET fabric while 1726, 2497, and 2237 fiber fragments per gram of fabric were emitted by chitosan finished PET fabric for 1, 2, and 3% chitosan concentration, respectively. The fabrics treated with 3% chitosan released 27% less fiber fragments compared to the non-treated sample. Though, there are no consistent results when the results are reproduced by repeated testing, as it may be due to the poor attraction on chitosan with PET fabric So, this treatment is considered to be non-durable and less effective as compared to pectin [152] and PLA / PBSA [154]. Table 3 summarizes the potential key findings of various mechanical and chemical finishing on the reduction of fiber fragments in the laundry. Apart from singeing and calendaring, there is a reduction of fiber fragments shedding by other finishes like compacting [94]. However, the results are positive in the case of polymeric chemical finishes. Polymeric film covering fibers can act as a protective layer against abrasion which reduce the release of fiber fragments. Although, polymeric film being the protective layer have possibili-

4.2.3. Finishing on denim garments Various denim finishing such as stone washing, sand blasting, scrapping, whiskers, tacking, grinding (i.e., destroy look), ripping cuts were involved in removing the dyes from the fabric surface [146,155,156]. Generally, the denim fabric has dyed with indigo by ring dyeing technique [157], when the abrasion takes place on the fabric surface, it enhances the faded effect. All these finishing have higher possibilities for the mitigation of fiber fragments during domestic washing as it opens the yarn structure and made soft, fluffy, flannel effect. Perhaps, denim finishing with cellulase enzymes removes fuzz fibers [158], hairiness on the fabric surface which significantly reduce the mitigation of fiber fragments during the washing cycles, however, yet there are no studies to support this statement. 10

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Table 3 Influence of mechanical and chemical finishing on fiber fragments releases. Finishing techniques

Results

Refs.

Finishing with chitosan

27% reduction of fiber fragments releases on polyester fabric. Poor durability and inconsistent results Significant reduction of fiber fragments released from PET fabric. No durability measurement for both finishes. 63.4% reduction of fiber fragments releases from the treated PA fabric 76.8% reduction of fiber fragments releases from the treated PA fabric 90% reduction of fiber fragments releases from the treated PA fabric Significantly reduce the fiber fragments emission. Non-durable

[94]

Finishing with silicone and acrylic resin Finishing with PLA Finishing with PBSA Finishing with pectin Mechanical finishing: singeing and calendering shearing and brushing

[94] [154] [154] [152]

Both finishing generates the fuzz fibers on the surface of the fabric to provide comfort properties, as it discharges a significant quantity of fiber fragments during domestic washing.

5. Conclusion and recommendations for future remarks

much higher than that made from continuous filaments. The type of yarn spinning (e.g., ring or open-end) and fabric interlacing (e.g., weaving or knitting) can play an important role in this matter. Any factor that enhances the physical interactions between fibers in the fabric structure reduces the release of fiber fragments during repeated laundry and drying processes. (c) Fabric Finishes: Some of the mechanical textile finishes (e.g., calendering, compacting, and sanforizing) and applying chemicals (e.g., softeners, anti-crease agents, cross-linkers) can reduce the release of fiber fragments from fabric in following wet processes. (d) Washing: Increasing the concentration of detergents containing abrasive inorganic salts, increasing the washing temperature and duration, and strong mechanical agitations can increase the breakage and release of fiber fragments from textiles. (e) Drying: Intensive drying conditions with mechanical agitations (i.e., tumble drying) can increase the breakage and release of fiber fragments from textiles. The broken and damaged fibers may remain on the surface of textiles and be released to the water stream during the next washing cycle.

There is a growing concern about the release of fiber fragments from textile products to the environment. This can be evidenced by the number of scientific publications on the topic during the last ten years (Fig. 1). The average textile consumption is estimated to be 25 kg/person/year in Europe and people wash their garments on a regular basis with automatic washers. The mechanical agitation of automatic washers and dryers causes abrasion, distortion and entanglement of fibers, and surface fuzz formation more rapidly. The release of fiber fragments during washing ranges from 100 to 300 mg for kg of washed fabric [128]. Considering the release of 100 mg of fiber fragments per kg of garments after each washing cycle [40], and only washing the dirty dresses 6 kg twice a month, each person is responsible for the release of 100 mg × 6 kg × 12 months × 2 times=14,400 mg/year [39]. If we assume only 1 billion people in developed countries wash their garments with this scheme, 14,40 0,0 0 0 kg of fiber fragments is released to the environment each year. The population of world has reached to 7.9 billion in 2021 [159] and this figure can be much higher which shows the impact of fiber fragments on the environment. Multiple steps in wastewater treatment plants can filter up to 95% of fiber fragments. Nonetheless, the remaining 5% of released fiber fragments eventually reach rivers and oceans.

As we discussed in Section 2, these small fibers can enter the food chain and impose a health risk for sea creatures and human beings. Ingestion and inhalation are the two main pathways for ubiquitous fiber fragments to enter human health as considered potential health impacts. These fiber fragments cause numerous adverse effects including infected organs and its failures, and cancer [144,160]. When the organisms are exposed consistently for a long duration, fiber fragments could cause chronic health issues. Therefore, neglecting this problem or acting late will only make the situation worse due to the increase in production and consumption of textile products in the coming years. People should be informed about the extent of this problem and the environmental awareness should force the stakeholders to act responsibly. Finally, the policy makers and environmental agencies should enforce new environmental regulations to mitigate this problem rather quickly. As we discussed in detail in previous sections, the release of fiber fragments from textiles depends on several parameters:

Nowadays, most textile products are made from polyester fibers [62] (approximately 70%) and cellulosic [13] (approximately 20%). Therefore, most of the research works on the release of fiber fragments were focused on these two fibers. Fabrics made from cotton and other cellulosic materials release more fiber fragments during the washing process than fabrics made from polyester. However, polyester fibers are considered a bigger threat to the environment than cotton because they are hydrophobic with an extremely low biodegradation rate. It should be noted here that there are several research gaps and a lack of thorough investigation on the fate of fibers with various treatments and finishing. Most textile products are dyed with various synthetic colorants including reactive dyes or coated with various chemicals and auxiliaries to render new functionality (e.g., water repellency, antimicrobial finishes). The presence of these chemicals may complicate the biodegradation of even natural fibers such as cotton. There is a need for measuring the aquatic toxicity and biodegradation of the fibers in the environment with and without various functional chemicals. Such research works will help (a) textile industry to develop textile finishes with lower environmental impacts and (b) environmental agencies to enforce better and evidence-based environmental regulations.

Our recommendations for the impact of textiles on the environment and more specifically the release of fiber fragments are as follows:

(a) Physical-chemical properties of fibers: The release of fiber fragments from natural fibers such as cotton are typically higher than that of synthetic fibers such as polyester. This can be attributed to the strength, durability, and resistance of fibers against various agencies including weathering (e.g., sunlight, UV radiation, oxidative gasses), chemicals (e.g., bleaching agents), wear/abrasion, repeated washing, and drying cycles (b) Yarn and fabric structure: The release of fiber fragments from staple yarns or fabrics made from staple fibers is generally