New drugs launched in the United States must first convince the FDA that they are safer or more effective than existing treatments. This is a statutory requirement. A similar approach is taken in Europe by the European Medicines Agency (EMA) and the Therapeutic Goods Administration (TGA) in Australia.
The same rigor has never been applied to biopolymers, and a new study highlights how we could be sleepwalking into avoidable environmental problems caused by them.
While not necessarily biodegradable, biopolymers are partly and sometimes entirely derived from biomass, such as plant, animal or marine materials. Cotton and viscose — also known as rayon — are common examples. Both contain a large percentage of cellulose.
During production, these polymer fibers are often treated with additives such as dyes and finishing products to make them oil-, stain- and water-repellent and, therefore, more durable.
They are used in clothing, wet wipes and sanitary products. However, their microfibers enter the environment through the laundry cycle and improperly flushed wet wipes and sanitary products. From there, they enter wastewater treatment facilities, where the majority are retained within biosolids in sewage sludge. This, in turn, is often used as an agricultural fertilizer.
Production is expected to rise in the coming decades as their use grows in the textile and apparel, medical and automotive sectors.
However, writing in Environmental Science & Technology (DOI: 10.1021/acs.est.4c05856), researchers at the UK’s University of Plymouth and University of Bath show that such fibers have the potential to induce greater ecotoxicological effects than traditional plastics.
The research compared the ecotoxicity of conventional polyester fibers with two bio-based fibers — viscose and lycocell — on earthworms. They chose earthworms because they are critical to soil health globally.
The study found that in high concentrations of fibers, 30% of earthworms died after 72 hours when exposed to polyester, while those exposed to the biobased fibers 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 fibers, indicated that earthworms housed in soils containing viscose fibers exhibited reduced reproduction compared to those exposed to polyester fibers. Earthworms in the soils containing lyocell fibers showed reduced growth plus also higher rates of burrowing within the soil compared to exposure to the other types of fiber.
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.
Winnie Courtene-Jones, lead author of the study and a lecturer in marine pollution, said: "Over 320,000 tons of biobased and biodegradable fibers 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 fibers 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 research was published just a few weeks before the United Nations gathered world leaders in Busan, South Korea, for the final round of negotiations regarding a possible Global Plastics Treaty. Such a treaty, the researchers suggest, should include independent ecological risk assessment and risk management on the ground to ensure responsible innovation with biobased polymers.
Professor Richard Thompson, senior author of the new study and head of the University of Plymouth's International Marine Litter Research Unit, attended the discussions.
He said: "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 emphasizes 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."
Meanwhile, the paper also notes that while the study contributes much-needed data on the acute and chronic effects of biobased fibers, further data are needed on other species to construct the species sensitivity distributions used in risk analysis and with data from real exposure scenarios to estimate the probable risks and uncertainties.
The study was carried out as part of the BIO-PLASTIC-RISK project and supported with £2.6 million ($3.3 million) in funding from the UK’s Natural Environmental Research Council.
