Dirty laundry: How much microfiber do we emit with our washing?

The discovery was made by academics at the University of Leeds' School of Design, who co-created a test to measure how different materials and washing conditions affect the amount of microfibres released into water.

Microfibres are tiny threads that enter the environment when garments are made, worn and washed. Although they are smaller than 5mm and invisible to the naked eye, microfibres have a substantial impact as a major source of water pollution.

As part of a project funded by trade body the European Outdoor Group (EOG) and sustainable textiles organisation The Microfibre Consortium (TMC), the researchers estimated that annual microfibre release from the UK's washing was between 6,860 and 17,847 tonnes. That's the equivalent of around 600 to 1,500 double-decker buses.

Postgraduate researcher and lead author Alice Hazlehurst said: "Quantifying microfibre release is an important step in understanding the scale of the problem, as well as the potential impacts of this form of pollution. There are already lots of estimates out there, but these vary dramatically and it's almost impossible to make meaningful comparisons.

"We used a reliable testing method to compare microfibre release from different fabrics and under different washing conditions in the lab. Based on our results we were able to estimate the quantity of microfibre release at a realistic scale."

Based on their estimate, the researchers argue that microfibre release is a relatively small problem in comparison to the fashion industry's waste problem, with 365,000 tonnes of clothing going to landfill every year from the UK.

Laundry in the lab

In a collaborative project involving the University of Leeds, EOG and a large network of stakeholders, TMC co-created and released a globally aligned, standard test to determine the level of microfibres shed from fabric during domestic laundering.

The TMC Test Method has already been adopted by EU and US standard bodies due to its reliability. This will help clothing brands more accurately test their garments for microfibre release, inform washing machine manufacturers about filtering and give a clearer picture of the scale of the problem.

To create a more reliable estimate of UK microfibre release, researchers used a Gyrowash -- a device that replicates a domestic washing machine in lab conditions. They tested 16 common fabrics, including polyester, cotton, viscose and blended materials, and compared different yarn types and constructions (knitted or woven fabrics). They also measured the effects of washing conditions, including the size of the load and how much the machine shakes the clothes.

How do wash settings affect microfibre release?

More than twice as much microfibre material was released when the ratio of water to clothing was doubled. Filling up the washing machine drum with more clothes can reduce the amount of microfibres lost because less water moves through the clothes and dislodges loose material. However, overfilling a washing machine can be a safety concern, as well as potentially reducing the quality of the wash.

Agitation -- the term for how much a washing machine shakes clothes around -- also had a big impact, with higher agitations increasing microfibre loss significantly.

Microfibre loss reduced substantially after a brand-new fabric's first wash, but this effect levelled out after three washes. Other estimates have been based on the results of new fabrics being washed, so the findings suggested that less microfibre is being released than previously thought.

The testing showed that the fabric characteristics -- yarn type, construction (knitted or woven), fibre type (eg polyester or cotton) -- had more influence than washing conditions on how many microfibres were released. The worst offender for microfibre release was a chenille polyester fabric, whereas some fabrics that had been brushed or peached lost less material.

Dr Mark Sumner, Lecturer in the School of Design, said: "Ultimately, the research shows that fabric choice is complex and we shouldn't assume some fabrics are worse than others."

Dr Kelly Sheridan, research director at TMC, said: "The Microfibre Consortium has actively driven for a globally aligned test method that can be used by the textile industry to measure fibre fragmentation from finished fabrics.

"The TMC Test Method was the foundation for the development of an international ISO standard, which is testament to its accuracy and reliability. Consequently, microfibre loss data generated from this method can supersede that of previous quantification estimates that have used inconsistent test methodologies."