The global production of anthropogenic fibres has markedly increased over recent decades, rising from 23% in 1965 to approximately 72% of today’s textile market. As a result, fibre-shaped microplastics (MPs) represent the most prevalent form detected in environments. In parallel, European policies (e.g., Regulation 2025/40 and Directive 2019/904) are promoting a transition towards recycled plastic materials. However, the ecotoxicological consequences of using recycled instead of virgin MPs remain poorly understood.
This study compares the effects of fossil-based polyamide 6 (PA6) and chemically regenerated PA6 (Econyl®) fibres on the benthic freshwater species Chironomus riparius across two generations. Econyl® is produced via chemical de-polymerization, monomer purification and re-polymerization.Organisms were exposed to a single environmentally relevant concentration (2 mg per 150 g dry sediment), based on MP levels reported in Italian rivers. Fibres were standardized (200 μm length, 40 μm diameter), and the experimental design followed OECD 233 guideline. In addition, oxidative damage biomarkers such as malondialdehyde (MDA) and protein carbonyl content (PCC) were measured, prior to adult emergence, in both generations.
In the first generation, both materials induced comparable responses across emergence rate, fecundity, and fertility, with only slight deviations from controls. Differences in development rate and time were observed for PA6, although these remained consistent with Econyl® patterns. In the second generation, a clearer differentiation emerged: while both polymers affected the same endpoints, PA6 exerted stronger effects, particularly on reproductive parameters, and developmental responses appeared more consistent.
Notably, no significant differences were detected for MDA and PCC in either generation, confirming similar oxidative stress responses between the two polymers. Overall, the findings suggest that regenerated fibres may reduce ecological risks, supporting plastic recycling as a strategy to mitigate MP impacts in freshwater ecosystems.