Microfibers in Life Cycle Assessment: Comparing the Physical Effects of Cellulosic and Synthetic Fibers via Characterization Factors Development

Textile clothing is a significant contributor to microfiber pollution in aquatic ecosystems. A large portion of emitted microfibers are cellulosic-based, either natural (e.g., cotton, linen) or semi-synthetic (e.g., viscose, lyocell), which can be ingested by aquatic organisms, posing harmful effects even at environmentally relevant concentrations. Studies comparing the effects of cellulosic and synthetic fibers report conflicting results: some suggest synthetic fibers are more harmful, others the opposite. However, the absence of a species sensitivity distribution (SSD) curve for cellulosic microfibers (CMFs) has prevented cross-species comparisons. Because CMFs are plant-based and degrade faster, cellulosic textiles are often considered more sustainable than synthetic ones, yet this claim has not been supported by a life cycle assessment (LCA) that accounts for microfiber emissions. In Life Cycle Impact Assessment (LCIA), characterization factors (CFs) have been developed for synthetic microfibers and microplastics (MPs), but not for CMFs, due to a missing exposure and effect factor (EEF) specific to these fibers. Given that cellulosic textiles can release more microfibers during washing and are found in greater environmental abundance than synthetic microfibers, CFs for CMFs are a critical gap this work addresses. The fate of CMFs (cotton, linen, viscose, lyocell, rayon, modal) in marine water and sediments was modelled based on material density, degradation, and size. An EEF was derived from a hazardous concentration for 20% of species (HC20), using an SSD of EC10eq values. The HC20 _EC10 of CMFs was statistically similar to that of MPs, indicating similar physical effect mechanisms. The EEF was combined with fate to compute CFs, which were applied in an LCA comparing the ecosystem quality impacts of a cotton and a polyester t-shirt. Results show that polyester emissions caused significant impacts, while cotton emissions did not.