The fashion industry has come under increasing fire for its impact on the planet, from production to clothes racks and back to the environment in the form of microfibres.
Now, the plot thickens. A chance discovery and resulting global survey, described in the journal Science Advances, found that nearly 92% of textile fibres floating in the ocean come from natural plant- or animal-based materials such as cotton and wool.
In 2017, Guiseppe Suaria, from Italy’s Institute of Marine Sciences National Research Council, and an international team of scientists were on an Antarctic Circumnavigation Expedition, charged with sampling microplastics.
They were using traditional plankton net-based methods with mesh that doesn’t tend to retain small fibres, he says.
“During the expedition, however, other team members dedicated to studying the phytoplankton brought our attention to the presence of many bright and coloured fibres in their seawater samples.”
Surprised, his team added that to their project throughout the expedition, then followed up on another five expeditions worldwide to compile a global dataset derived from 916 seawater samples of more than 23,000 fibres from 617 locations.
At first, they weren’t sure if the fibres were coming from their own ship’s wastewater outlets, so they used a metal bucket to collect water undisturbed by the ship from its bow during navigation before filtering the samples.
Back in the lab, the team counted, isolated and analysed the fibres to determine their composition, abundance and global distribution.
They found considerable variation across sites, with concentrations ranging from 0.02 to 25.8 fibres per litre, translating to an average 90,000 to 380,000 metric tonnes of plastic floating in the top layer of the Earth’s oceans.
The highest concentrations were in the Mediterranean Sea and the lowest in the North Atlantic Ocean. Only three samples didn’t contain fibres, one from the North Atlantic and two off the coast of Mozambique in the Indian Ocean.
They were surprised to find high concentrations in the remote Southern Ocean, which they speculate could have arrived there via land or sea.
Micro-Fourier transform infrared analysis showed 79.5% were cellulose-based (mostly cotton but including viscose, linen, jute, kenaf and hemp), 12.3% were animal-based (mainly wool) and 8.2% were synthetic (predominantly polyester, along with acrylic and nylon).
This contradicts previous studies of microplastics, which the authors suggest could mean others have assumed all coloured fibres are synthetic and not subjected them to careful chemical analysis.
The overwhelmingly high concentration of natural fibres is also in stark contrast to the global production of textiles, which has been dominated by synthetic fibres since the mid-1990s.
It’s possible that natural fabrics shed more fibres in the washing machine, but it could also reflect how long they’ve been there, the authors suggest.
“[A] crucial factor to understand is the life span of different fibre types in the environment,” they write, “given the historical dominance of plant and animal fibre use in textiles.”
Wool and cotton are thought to break down more quickly than man-made fibres, but the study suggests they are not degrading as would be expected, which could have to do with their production.
“Probably, the degradation of these fibres is slowed down by chemical dyes and additives which are added during textile production,” says Suaria. “However, we still know very little on this, and more research is needed to better understand why these fibres are not degrading at sea.”
Their impact on the surrounding environment and ecosystem also needs to be explored, says co-author Jasmine Lee from Monash University, Australia.
Meanwhile, it seems that replacing synthetic with natural fibres will not absolve the fashion industry from making radical changes, after having doubled textile production in the last 20 years, soaring to 107 million metric tonnes in 2018 alone and rising.