Natural materials in products such as wet wipes may do more harm to the environment than the synthetic ones they are intended to replace, researchers at the University of Bangor say. 

So-called bio-based fibres – typically derived from wood pulp or other plant-derived materials – are advocated as more environmentally friendly alternatives to plastics, and frequently used in textiles and products including clothing, wet wipes and period products.

However, microfibres of all these materials – natural and synthetic – 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.

The scientists at Bangor say comparatively little is known about the impact that that natural fibres used in personal hygiene and clothing products have on species and ecosystems. 

To address that, their study – published in the journal Environmental Science and Technology – tested the effects of conventional polyester fibres and two commonly used 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 (levels that reflect real-world conditions), 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 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.

“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 wide-scale adoption”

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 wide-scale 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.”