Bio-Based Fibers May Harm Earthworms

As industries seek alternatives to conventional plastics, bio-based materials are increasingly adopted in everyday products, from clothing to personal hygiene items. While they offer a potentially more sustainable option, these fibers – such as viscose and lyocell – are released into the environment through daily activities like washing and waste disposal, similar to traditional plastic fibers. A new study published in Environmental Science & Technology investigates whether these bio-based materials might pose unexpected ecological risks, focusing on their effects on earthworms.

Impact of bio-based fibers on earthworms

The study, conducted by researchers from the University of Plymouth and the University of Bath, evaluated how conventional polyester and bio-based fibers affected earthworms when present in soil. Earthworms are essential for soil health and nutrient cycling. In controlled settings, researchers found that earthworms exposed to bio-based fibers exhibited significant adverse effects compared to those exposed to polyester fibers. In high concentrations, up to 80% of earthworms died when exposed to viscose, while lyocell exposure resulted in 60% mortality. By contrast, mortality for earthworms in polyester-contaminated soil was 30%.

In a second experiment with more environmentally relevant fiber concentrations, the study observed reductions in earthworm reproduction in viscose-exposed soils. The earthworms also showed changes in growth patterns and increased burrowing activity when exposed to lyocell. These findings suggest that bio-based fibers may interfere with the biological functions of earthworms in ways that plastic microfibers do not.

Need for further assessment of bio-based materials

The results underscore the need to assess bio-based materials thoroughly before they are broadly adopted as sustainable alternatives to plastics. Although over 320,000 metric tons of these fibers were produced in 2022, research into their environmental impact is limited. This study, part of the BIO-PLASTIC-RISK project funded by the Natural Environmental Research Council, aims to fill that gap by highlighting the ecological risks that bio-based materials may pose if they accumulate in natural environments.

Implications for future material innovations

The research team emphasizes that while bio-based materials are intended to address the plastic pollution crisis, unintended ecological consequences must be considered. They urge additional environmental testing to evaluate any potential impacts on key soil organisms like earthworms. The findings arrive as global leaders prepare to discuss plastic pollution and potential regulatory measures at the United Nations Global Plastics Treaty negotiations in South Korea.

 "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.”

Professor Richard Thompson OBE FRS

As society continues to explore sustainable alternatives to plastics, this research highlights the importance of balancing material innovation with ecological impact assessments to avoid potential risks to essential species and ecosystems.

Reference: Courtene-Jones W, De Falco F, Burgevin F, Handy RD, Thompson RC. Are biobased microfibers less harmful than conventional plastic microfibers: evidence from earthworms. Environ Sci Technol. 2024. doi: 10.1021/acs.est.4c05856

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