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Plastics under the microscope

25/03/2020

Hohenstein has developed a test for measuring fabrics’ shedding capacity and hopes to further industry understanding through its membership of the Microfibre Consortium.

Germany-based testing institute Hohenstein has developed a new method for analysing microfibre shedding from textiles, that is the result of four years of research, led by scientist Jasmin Haap. It says it goes beyond previously available tests to measure count, length, diameter and shape and can separate results for cellulosic fibres and non-cellulosic fibre.

Last October, through its work with the Microfibre Consortium (TMC), Hohenstein released the dynamic image analysis to TMC’s 40 members, including adidas, Mammut, Lenzing, WL Gore and the European Outdoor Group. The test was offered in conjunction with a filtration test that had been developed by the University of Leeds on behalf of TMC, offering clients two ways to conduct tests. Chair of TMC Sophie Mather describes the tests as “the crucial bridge from deep academic work to the reality of commercial product development that the industry is crying out for”.

Synthetic microfibres are the tiny pieces of plastic (< 5mm) released into water during mechanical stress, particularly washing (both industrial and domestic), but also through the manufacture of the fabrics and at the point of their disposal. Wastewater containing microfibres eventually flows into rivers and lakes, where they can be ingested by fish, birds and animals, entering the food chain. It is unclear how this affects humans.

Fibres are one of the most frequent particle shapes detected in environmental samples. With the finger pointing at the clothing industry, multiple studies are under way, involving various groups and companies, trying to produce testing methods that could help companies make better material choices or limit the shedding in other ways.

“Although exact figures to the extent of the impact from the clothing industry have not yet been quantified, both media and non-governmental organisations are quick to hold the industry responsible,” said Sophie Mather. “In answer to this, in order to mitigate industry risk, it is the obligation of those associated to textiles to take action.”

Image analysis

Hohenstein’s dynamic image analysis is an optical detection system for particle characterisation and is widely used in the medical and the food industry. Dispersed effluent is transported through a cuvette and a high-resolution camera captures images of the particles. Every fibre is photographed and analysed by software Hohenstein has developed – a single sample might contain 10,000 images. The software can categorise the fibres according to size and structure, but cannot determine what they are made of; adding sulphuric acid as a next step helps to assess their construction.

Hohenstein suggests its method helps to overcome some difficulties with earlier tests: counting microfibres by eye has the potential for human error and limitations such as overlapping, and weighing microparticles after filtration could lead to overestimations, with contaminates such as dust potentially sticking to the fibres. Its dynamic image analysis of wastewater is non-destructive, allowing additional tests to be performed. 

Previous studies have also concentrated on the five main fibre groups – cotton, polyester, polyamide, wool and silk – but there has been little research on blends. As poly-cotton blends are the most readily manufactured fibre, Hohenstein wanted to offer that option, and received funding from the German government for the research. It also focused on industrial washing, rather than from domestic machines, an area where data is scarce.

Clouding judgement

During the testing process, Hohenstein found that only 10% of the shedding was down to fibre – 90% were contaminants and particles that may have been picked up in the manufacturing stage. “100% polyester fabrics could show some cotton shedding,” says Dr Jan Beringer, Hohenstein’s senior scientific expert, “as manufacturing does not take place in a ‘clean’ environment – contaminants are everywhere.” Obviously, many fabrics are blends, and also contain dyes, finishes, coatings and other chemicals, which can make the analysis more complex. It also found that the finer the fibre, the more it shed, and said it was surprised by finding that staple fibres do not appear to shed more than filament fibres.

So, what’s next? 

With the test now available to brands and manufacturers, it is a matter of which fabrics are tested, and how companies choose to act. Data from TMC members will be reviewed by mid-March and by April, and it is hoped more third-party labs will be able to offer the test. “Findings will be released firstly to TMC members, then we will do a delayed release of information to the public,” says Katy Stevens, technical director at TMC, adding that they need to be 100% sure of the methods and would rather be overcautious, given the potential ramifications. “We are talking to various partners around the world because we would like one global method; if they differ it would be hard to compare data, so we are working to make sure our methods are aligned,” she adds.

Dr Beringer says that as a third-party testing provider, Hohenstein has to remain neutral in terms of advice to clients but that “there is a worldwide effort in agreeing standards. We are all talking to each other to align on that.”

Other research papers have shown that particles from tyres make up a large portion of microplastics in the oceans, as do those from cosmetics, and that in terms of fibres found in water samples, cellulosic or natural fibres seem to exist in larger quantities than synthetic fibres (possibly because synthetics are more abrasion resistant). The types of washing machine used and detergent seem to have an effect on shedding, while the quality of the wastewater treatment is also important. “This is a key issue that needs to be addressed. If there is no wastewater treatment, all fibres will end up in the ground and the oceans,” says Mr Beringer.

While a study from Finnish company EMPA early in 2019 found the scale of harm that microplastics were doing to humans in Europe seemed negligible (for now), it is apparent that more data is needed. Companies at least now have tools to ramp up analysis as the regulatory bodies, and the public, begin to examine more closely where plastics persist, and their implications for our health.

See WSA May/June 2019, The rising tide of microplastics, for a wider look at the current research.