Effects of polypropylene micro- and nanoplastics from surgical masks in amphibian and echinoderm models

Micro- and nanoplastic toxicity is a growing environmental concern, especially in aquatic ecosystems. This study investigates the acute and chronic effects of polypropylene microfibers (PP MFs), derived from artificially aged surgical face masks, on two aquatic species: the freshwater amphibian Xenopus laevis and the marine brittle star Ophiactis virens. Characterisation of the aged PP material revealed both microfibers (mean size: 21.7 ± 13.4 μm × 1.9 ± 0.8 μm) and nanofragments (mean diameter: 176 ± 28 nm), with a nano/micro abundance ratio of 4.3. X. laevis larvae ingested large quantities of PP MFs, resulting in near-complete gut obstruction, while juvenile O. virens did not show internal accumulation. Despite this, both species exhibited some sublethal effects, particularly at the behavioural level and at the highest tested dose (10 µg mL⁻¹). Indeed, X. laevis larvae reduced their swimming activity, whereas O. virens showed impaired righting ability. Moreover, X. laevis larvae grew significantly more than controls at all tested concentrations (0.1–10 µg mL⁻¹). No significant effect was observed at the cell-tissue level, except for a few cases of ultrastructural alteration in X. laevis intestinal epithelium. The LOEC values were 0.1 µg mL⁻¹ for X. laevis and 10 µg mL⁻¹ for O. virens; corresponding NOECs were < 0.1 and 1.0 µg mL⁻¹, respectively. These findings highlight species-specific responses, likely linked to ecological traits and life stage, and caution against generalizing toxicity outcomes across taxa. Overall, the study underscores the environmental legacy of COVID-19-related waste able to release a huge quantity of both micro- and nano-plastics with variable yet significant impacts on aquatic life.