Thousands of tons of microfibres are being released into European marine environments every year

A new study has revealed that almost 13,000 tonnes of microfibres, equivalent to two rubbish trucks every day, are being released into European marine environments every year – but this could be reduced by as much as 30% if we made a small change to our laundry habits.

The findings have been published by the scientific journal PLOS ONE today, ahead of World Oceans Day on Monday 8 June.

Every time you wash your clothes, thousands of tiny microfibres from the fabric are released into rivers, the sea and the ocean, causing marine pollution.

Scientists have speculated for some time that these microfibres may cause more harm than microbeads, which were banned from UK and US consumer products in recent years.

Researchers from Northumbria University worked in partnership with Procter & Gamble, makers of Ariel, Tide, Downy and Lenor on the first major forensic study into the environmental impact of microfibres from real soiled household laundry.

Their forensic analysis revealed an average of 114 mg of microfibres were released per kilogram of fabric in each wash load during a standard washing cycle.

Given that a 2013 AISE report suggested 35.6 billion wash loads are completed in 23 European countries each year, the researchers suggest a massive 12,709 tonnes of microfibres are being released from washing machines into rivers, the sea and the ocean each year in Europe alone. This is the equivalent of two rubbish trucks worth of waste ending up in marine environments each day.

However, the researchers achieved a 30% reduction in the amount of microfibres released when they performed a 30-minute 15 C wash cycle, in comparison to a standard 85-minute 40 C cycle, based on typical domestic laundering.

If households changed to cooler, faster washes, they would potentially save 3,813 tonnes of microfibres being released into marine ecosystems in Europe.

The researchers found even more significant differences when they compared different microfibre release from different types of North American washing machines.

Households in North America and Canada have historically used high volume traditional top loading washing machines with an average 64 litre wash water volume. The market is gradually moving to high-efficiency machines which use up to 50% less water and energy per load.

As a consequence, these high-efficiency machines released less microfibres than traditional top-loading machines, with notable examples including a 70% reduction in microfibres from polyester fleece fabrics and a 37% reduction from polyester T-shirts.

How you can reduce the impact of microfiber loss when you wash your clothes. Credit: Northumbria University

Other key findings emerging from the study include:

• Larger wash loads led to a decrease in the release of microfibres, due to a lower ratio of water to fabric. As such, the research team advises consumers fill—but do not overfill—their washing machines. A correctly filled washing machine should be around three-quarters full.
• New clothes release more microfibres than older clothes. Microfibre release was more prominent in new clothes during the first eight washes.
• Fabric softeners were found to have no direct impact on microfibre release when tested in both European and North American washing conditions.

A novel aspect of the study was the involvement of forensics expertise from Dr. Kelly Sheridan, an expert in forensic textile fibres who has worked on several high-profile murder cases. Her guidance ensured the research could be conducted without cross-contamination of fibres from other sources.

The team applied test methods used in forensic science, such as spectroscopic and microscopy techniques, to examine the structure and composition of the microfibres released from the clothing.

This enabled the fibres to be weighed and characterised to determine the ratios of manmade to natural fibres being released from wash loads.

The researchers found that 96% of the fibres released were natural, coming from cotton, wool and viscose, with synthetic fibres, such as nylon, polyester and acrylic accounting for just 4%.

A positive point to note is that the natural fibres from plant and animal sources biodegrade much more rapidly than synthetic fibres. A previous study has identified that cotton fibres degraded by 76% after almost eight months in wastewater, compared to just 4% deterioration in polyester fibres.

This means that natural fibres will continue to degrade over time, whereas petroleum-based microfibres plateaued and can be expected to remain in aquatic environments for a much longer period.

John R. Dean, Professor of Analytical and Environmental Sciences at Northumbria University, who led the study, said: “This is the first major study to examine real household wash loads and the reality of fibre release. We were surprised not only by the sheer quantity of fibres coming from these domestic wash loads, but also to see that the composition of microfibres coming out of the washing machine does not match the composition of clothing going into the machine, due to the way fabrics are constructed.

“Finding an ultimate solution to the pollution of marine ecosystems by microfibres released during laundering will likely require significant interventions in both textiles manufacturing processes and washing machine appliance design.”

Dr. Neil Lant, Research Fellow at Procter & Gamble, said: “This study has proven that consumer choices in the way they do their laundry can have a significant and immediate impact on microfibre pollution. These won’t eliminate the issue but could achieve a meaningful short-term reduction while other solutions such as washing machine filters and low-shedding clothing are developed and commercialised.”

The researchers say that the study provides evidence for appliance manufacturers to introduce filtering systems into the design of machines and develop approaches to reduce water consumption in laundry. Procter & Gamble laundry products, such as Ariel Pods, are suited to low temperatures and the company intends to use this evidence to bring further innovations to enable consumers to wash with low temperatures without compromising on performance.

They also hope it will encourage textile manufacturers to help by conducting filtered pre-washing to remove the most labile fibres which can easily break down and displace.

The study is a further example of the work undertaken at Northumbria University which led to it being ranked 6th in the UK and 27th globally for sustainability last month.

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Global fiber production, both synthetic and natural, has more than doubled in the past 20 years, reaching 107 million metric tons (MMT) in 2018 and is expected to reach 145 MT in 2030 if business as usual continues (1).

Largely driven by the production of polyester (55 MT year−1 in 2018), synthetic polymers have dominated the textile market since the mid-1990s when they overtook cotton as the dominant fiber type. Synthetic fibers now account for almost two-thirds of global fiber production (2) and for 14.5% of plastic production by mass (3). With a market share of 24% and 15% growth from 2017 to 2018 (1), cotton is the second most important fiber (27 MT year−1 in 2018), followed by man-made cellulosics (e.g., viscose/rayon), which account for 6.2% of global fiber production (6.7 MT year−1).

Other plant-based fibers, such as jute, linen, and hemp, together account for 5.7% of the global market (6 MT year−1), while animal fibers (wool and silk) account for just over 1% of annual production (1). The main uses of both natural and synthetic fibers are clothing and apparel, followed by household and furnishings, automotive, and other industrial applications such as construction, filtration, and personal care (4). Shedding of fabric materials, wear and tear, and increased consumption have led to the accumulation of these fibers in the natural environment (5, 6).

Large numbers of fibers are discharged into wastewater from washing clothes (7–9), with each garment releasing up to 107 fibers per wash (10–12), and enter the environment through wastewater effluent (13), aerial deposition (14, 15), or through the application of contaminated sludge on agricultural soils (16).

As a consequence, fibers are now the most prevalent type of anthropogenic particle found by microplastic pollution surveys around the world (17), including human exposure studies (18). Substantial concentrations have been detected in surface and subsurface waters (19–21), in sea ice (22), deep-sea (23, 24) and coastal sediments (25), as well as in terrestrial and freshwater ecosystems (26, 27).

Given their abundance, it is not surprising that fibers have been detected in food (18), drinking water (28), and human lungs (29), as well as in the digestive tracts of many aquatic (30, 31) and terrestrial organisms (32). Under laboratory conditions, adverse health effects due to ingestion of microfibers have been observed in marine (33), freshwater (34), and terrestrial (35) invertebrates, but no proof of harm is currently available for wild organisms exposed to environmentally relevant fiber concentrations.

In addition, a wide variety of chemicals are used during textile production including dyes, additives, and flame retardants (4), raising concerns about the role of fibers as vectors of hazardous substances into the environment (7).

Because of the risk of external contamination (36), fibers were initially excluded from microplastic surveys (37). However, they are now commonly included in many studies, often accounting for 80–90% of microplastic counts (7, 17), although their synthetic nature is seldom demonstrated. Here, we show that synthetic polymers only account for a small portion of the fibers extracted from open ocean samples.

Besides emphasizing the need for further research on the fate and impacts of natural fibers in marine ecosystems, our results indicate that, in the absence of a comprehensive chemical characterization, the abundance of microplastic fibers in natural environments has been probably overestimated. Our results highlight a considerable mismatch between the global production of synthetic textiles and the current composition of marine fibers, a finding that deserves further research.

RESULTS
Our dataset consists of 916 seawater samples collected at 617 locations in six oceanic basins (13,447.5 liters of seawater filtered). Fibers were found in 99.7% of all samples, totaling 23,593 fibers (median 18 fibers per sample; Q1–Q3, 10–31 fibers). Fibers were absent from only three samples: one subsurface sample collected in the North Atlantic and two samples collected off the coast of Mozambique in the Indian Ocean.

The raw concentration of fibers spanned three orders of magnitude from 0.02 to 25.8 fibers liter−1 (Fig. 1) with a median concentration of 1.7 fibers liter−1, which decreased to 1.6 fibers liter−1 (Table 1) after applying correction factors for contamination level, sampling depth, and mesh size effect (table S1 and fig. S1). Most fibers were dark/black (57.1%) or light/gray (24.2%), followed by blue (10.1%), red/orange (5.2%), yellow/amber (2.9%), and green (0.4%).

Fiber concentration was not homogeneous across ocean basins [Kruskall-Wallis H(χ2) = 140.1, P = 2.5 × 10−41). The highest concentrations were found in the Mediterranean Sea (Fig. 2), while the North Atlantic Ocean exhibited significantly lower concentrations than all other basins (Table 1).

The concentration of fibers tended to increase from north to south, but the latitudinal range sampled was greater in the southern hemisphere, and this pattern may reflect a general increase in fiber concentrations at higher latitudes (fig. S2). When excluding Mediterranean samples, a significant negative correlation was found between latitude and corrected fiber concentration [rs(806) = –0.16, P = 2.3 × 10−6].

This correlation was also significant when the dataset was restricted to a single cruise [Antarctic Circumnavigation Expedition (ACE)], both including the North Atlantic [rs(406) = –0.23, P = 3.6 × 10−6] and only samples collected in the southern hemisphere [rs(715) = –0.11, P = 0.0021].

High fiber concentrations were found in the Southern Ocean between 40°S and 60°S (Fig. 2 and Table 1), suggesting accumulation of fibers north of the polar front or retention within the Antarctic Circumpolar Current. Nevertheless, the concentration of fibers south of 60°S was not significantly different from that found in the South Atlantic or the Indian Ocean (table S2).

Median fiber length was 1.07 mm (Q1–Q3, 0.65–1.74 mm; range, 0.09–27.06 mm). Only 10 fibers were longer than 10 mm, and only 3 fibers were longer than 15 mm. Fiber length distribution showed a peak in abundance around 0.8–0.9 mm and a pronounced gap below 0.4 mm (Fig. 3A).

Significant differences were found in fiber length among ocean basins [Kruskal-Wallis H(χ2) = 43.9, P = 1.6 × 10−9), with fibers from the Mediterranean Sea being significantly longer and fibers from the Southern Ocean being significantly shorter than all other basins (Table 2). Fibers from the Indian and the Atlantic Ocean were of intermediate length and not significantly different from each other (table S3A).

Median fiber diameter was 16.7 μm (Q1–Q3, 15.0–20.4 μm; range, 5 to 239 μm). Most fibers had a diameter of 10–11 μm, 15–17 μm, or 19–20 μm (Fig. 3B). Median aspect ratio (length:diameter) was 62.9 (Q1–Q3, 35.7–104.8; range, 3.1 to 1315).

As with fiber length, there were significant differences among ocean basins in fiber diameters [Kruskal-Wallis H(χ2) = 33.09, P = 2.9 × 10−7], with all basins being significantly different from each other except the Indian and the Southern oceans (table S3). Fibers from the Mediterranean Sea were significantly thicker than those collected in the Southern, Indian, and Atlantic oceans (Table 2 and fig. S3B).

When compared to seawater samples, the fibers extracted from procedural blanks (n = 161) were significantly thinner (Mann-Whitney U = 1.45 × 10−5, P = 0.0238) but not shorter (Mann-Whitney U = 1.61 × 10−5, P = 0.911). The same was true when considering all basins separately (Table 2), with the exception of the Mediterranean Sea, where fibers were significantly longer and thicker, and the Indian Ocean, where fibers were significantly thicker than those found in the blanks (fig. S3 and table S3).

Micro–Fourier transform infrared (μFTIR) characterization revealed that 91.8% of fibers were natural fibers of animal or plant origin (n = 1984). Most fibers were cellulosics (79.5%), with cotton being the most frequent match (50% of all fibers; n = 992), followed by other plant-based fibers (e.g., viscose, linen, jute, kenaf, hemp, etc.), which accounted together for 29.5% of all fibers (n = 585). A further 12.3% (n = 244) were animal fibers: 11.6% wool and 0.6% silk. Only 8.2% of fibers were synthetic (n = 163). Most plastic fibers were polyester (n = 123; 6.2% of the total), followed by acrylic and nylon (n = 14 each; 0.7%), polypropylene (n = 7; 0.4%), and aramid (n = 5; 0.3%).

The composition of fibers was not homogeneous across ocean basins (χ2 = 46.89, df = 12, P = 9.04 × 10−9). The relative proportion of synthetic fibers increased at higher latitudes, from 6.8% in the Mediterranean to a maximum of 12.6% in Antarctic waters south of 60°S (Fig. 4). A similar pattern was found for animal fibers, whose contribution in the Southern Ocean (14.5%) was almost double that in the Indian Ocean (7.7%) and the Mediterranean Sea (6.3%).

There was a corresponding decrease in the occurrence of cellulosic fibers at higher latitudes from a maximum of 86.9% in the Mediterranean to 72.9% in Antarctic waters. The composition of fibers extracted from blank samples (n = 150) was significantly different from seawater samples (χ2 = 7.987, df = 2, P = 0.0092), because of a higher proportion of cellulosic fibers (87.3%) and a shortage of wool fibers (4.7%), but similar content of synthetic fibers (8%).

All the synthetic fibers from the Indian Ocean (n = 24) were made of polyester, while polypropylene and aramid were found only in the Mediterranean and in the Southern Ocean, although in low numbers (table S4).

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More information: The paper, Microfiber Release from Real Soiled Consumer Laundry and Impact of Fabric Care Products and Washing Conditions is available through PLOS ONE.