Bio-based fibers could pose greater threat to the environment than conventional plastics

Such materials are increasingly being advocated as environmentally friendly alternatives to plastics, and used in textiles and products including clothing, wet wipes and period products.

However, microfibres of the materials are emitted into the environment through the laundry cycle, the application of sewage sludge as fertilisers, or the simple wear and tear of textile products.

Despite increasing quantities of bio-based products being produced and sold all over the world, there has been little research to assess their potential impact on species and ecosystems.

To address that, a new study in the journal Environmental Science and Technology tested the effects of conventional polyester fibres and two bio-based fibres -viscose and lyocell -- on earthworms, a species critical to the health of soils globally.

The study found that in high concentrations of fibres, 30% of earthworms died after 72 hours when exposed to polyester, while those exposed to the bio-based fibres experienced much higher mortality of up to 60% in the case of lyocell and 80% for viscose.

A second experiment, using environmentally relevant concentrations of the fibres, indicated that earthworms housed in soils containing viscose fibres exhibited reduced reproduction compared to those exposed to polyester fibres. Earthworms in the soils containing lyocell fibres showed reduced growth and also higher rates of burrowing within the soil compared to exposure to the other types of fibre.

The researchers say the study highlights the complex nature of global efforts to reduce the threat of microplastic pollution, and the importance of testing new materials being advocated as alternatives to plastics before they are released on the open market.

The study was carried out as part of the BIO-PLASTIC-RISK project, led by researchers at the University of Plymouth and the University of Bath, and supported with £2.6million funding by the Natural Environmental Research Council.

Dr Winnie Courtene-Jones, lead author on the new study and now a Lecturer in Marine Pollution at Bangor University, said: "Over 320,000 tonnes of bio-based and biodegradable fibres were produced globally in 2022 and research shows that substantial quantities of that will end up in the environment. However, evidence of their ecological impacts has been lacking. Our study has shown that bio-based fibres have a range of adverse effects on earthworms -- animals which are critical to the functioning of the environment. It highlights the importance of gathering further evidence before alternatives to conventional plastics are made available even more widely."

The new study follows research published earlier in 2024 which highlighted that being exposed to the materials used in biodegradable teabags can result in earthworm populations experiencing up to 15% greater mortality, and have a detrimental effect on earthworm reproduction.

It has been published just a few weeks before the United Nations gathers world leaders meet in Busan, South Korea, for the final round of negotiations regarding a possible Global Plastics Treaty.

Professor Richard Thompson OBE FRS, senior author on the new study and Head of the University of Plymouth's International Marine Litter Research Unit, will be at those discussions along with policy makers, scientists and other delegates from across the world.

He added: "It is clear that along with recycling and re-use, tackling plastic pollution will require a reduction in the quantities of plastics used and produced. There is increasing interest in alternative materials that could be used as substitutes for plastic, but this publication further emphasises the importance of testing new innovations in relevant environmental settings prior to widescale adoption. I firmly believe it is possible to tackle the plastic pollution crisis, but independent scientific evidence will be critical in helping us avoid unintended consequences as we look for solutions."