Beyond plastics: occurrence and ecological risks of non-plastic microfibres in aquatic organisms

Abstract Non-plastic microfibres, here defined as anthropogenically manipulated fibres of cellulosic or animal origin such as wool, cotton and rayon, have been increasingly recognised as a significant component of anthropogenic microparticle pollution in aquatic environments. Emerging attention has also been brought to the ecological ramifications of non-plastic microfibres and their associated chemical additives. However, environmental anthropogenic microparticle surveys have often omitted both plastic and non-plastic microfibres, with greater attention being placed on microplastic fragments, films, and spheres. This lack of attention has potentially led to the underestimation of non-plastic microfibre pollution in aquatic environments and biota. Through a comprehensive systematic review, we collate and analyse published literature (2011–2024) on non-plastic microfibre occurrence in aquatic animals and the associated ecological impacts. This review demonstrates that plastic and non-plastic microfibres, when looked for, are a significant component of anthropogenic microparticle (AMP) loading in aquatic biota across environments, habitats and feeding strategies. Greatest loading appears in freshwater environments with some cases accounting for 100% of detected anthropogenic microparticles, despite relatively limited study focus. The ecological impacts of non-plastic microfibres may also elicit varied effects on biota, depending on the context and nature of exposure, although targeted experiments are scarce in the literature. This review highlights the underestimation and potential misidentification of non-plastics due to methodological limitations, inconsistent reporting, and lack of focus. Here we emphasise that future research should develop standardised anthropogenic microparticle survey methodologies that incorporate non-plastic particles and microfibres, with greater effort placed on understanding microfibre pollution in aquatic biota. Further exploration into the ecological impact of non-plastics is crucial to understanding and mitigating the risks associated with these pollutants.