Microplastic pollution represents a global problem with negative impacts on aquatic environment and organisms’ health. To date, most of the laboratory toxicological studies on microplastics (MPs) have made use of single commercial micro and nano-polymers, which do not reflect the heterogeneity of environmental MPs. To improve the relevance of the hazard assessment, micrometer-sized plastic particles of miscellaneous non-reusable waste plastics, with size <100 µm and <50 µm (waste microplastics, wMPs), were characterized by microscopic and spectroscopic techniques and tested on developing zebrafish and Xenopus laevis by FET and FETAX assays respectively. Moreover, the modalities of wMP interaction with the embryonic structures, as well as the histological lesions, were explored by light and electron microscopy.

We have shown that wMPs had very heterogeneous shapes and sizes, were mainly composed of polyethylene and polypropylene and contained metal and organic impurities, as well as submicrometric particle fractions, features that resemble those of environmental occurring MPs. wMPs (0.1–100 mg/L) caused low rate of mortality and altered phenotypes in embryos, but established species-specific biointeractions. In zebrafish, wMPs by adhering to chorion were able to delay hatching in a size and concentration dependent manner. In Xenopus embryos, which open stomodeum earlier than zebrafish, wMPs were accumulated in intestinal tract, where produced mechanical stress and stimulated mucus overproduction, attesting an irritation response.

Although wMP biointeractions did not interfere with morphogenesis processes, further studies are needed to understand the underlying mechanisms and long-term impact of these, or even smaller, wMPs.

微塑料污染是一个全球性问题，对水生环境和生物体健康产生负面影响。迄今为止，大多数关于微塑料 (MPs) 的实验室毒理学研究都使用了单一的商业微纳米聚合物，这并不能反映环境 MPs 的异质性。为了提高危害评估的相关性，通过显微和光谱技术对各种不可重复使用的废塑料的微米级塑料颗粒（尺寸 <100 µm 和 <50 µm）进行了表征，并在斑马鱼发育中进行了测试和非洲爪蟾分别通过 FET 和 FETAX 测定。此外，通过光学和电子显微镜探索了 wMP 与胚胎结构以及组织学病变相互作用的方式。

我们已经证明 wMP 具有非常不均匀的形状和大小，主要由聚乙烯和聚丙烯组成，含有金属和有机杂质，以及亚微米颗粒部分，这些特征类似于环境发生的 MP。wMPs (0.1–100 mg/L) 导致胚胎的低死亡率和改变的表型，但建立了物种特异性的生物相互作用。在斑马鱼中，wMPs 通过附着在绒毛膜上能够以依赖于大小和浓度的方式延迟孵化。在比斑马鱼更早打开口的非洲爪蟾胚胎中，wMPs 在肠道中积累，在肠道中产生机械应力并刺激粘液过度产生，证明了刺激反应。

尽管 wMP 生物相互作用不会干扰形态发生过程，但需要进一步研究以了解这些甚至更小的 wMP 的潜在机制和长期影响。