Aquatic testing of particulate materials (PMs), e.g., nanomaterials (NMs) and microplastics (MPs), poses inherent challenges potentially hindering the application of existing test guidelines (TGs). Those TGs are primarily designed for hazard assessment of the dissolvable form of a material, whereas the guidance document on aquatic and sediment toxicological testing of NM (OECD Guidance Document 317) encourages the inclusion of potential colloidal fractions in the assessment. A prerequisite for the testing of PMs is the preparation of stable dispersions. However, testing difficulties may result from the fact that nano-scale PMs are inherently unstable when dispersed in test media, leading to the need for differentiation of potential chemical vs. physical effects caused by the tested material. Aquatic testing of unstable PMs will likely result in inconsistent and non-uniform uptake and exposure scenarios and thus effects observed in the respective test systems. Maintaining stable exposure conditions is often very challenging given the constantly changing size of the PM and its agglomerates, requiring observed endpoints to be based on measured concentrations and particle size distributions present in the water phase, while neglecting agglomerated and settled particulates. In this paper we describe the current state of PM-testing, demonstrate PM-specific challenges in aquatic testing (e.g., test duration, physical effects, instability, biodegradation, bioaccumulation) with a focus on NMs, considering a set of most relevant TGs, and provide proposed testing considerations to optimize aquatic testing of PMs.

中文翻译：

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优化颗粒材料水生测试的实际考虑，重点关注纳米材料

颗粒材料（PM）例如纳米材料（NM）和微塑料（MP）的水生测试提出了固有的挑战，可能阻碍现有测试指南（TG）的应用。这些TG主要用于对材料的可溶解形式进行危害评估，而关于NM水生和沉积物毒理学测试的指导文件（OECD指导文件317）鼓励在评估中纳入潜在的胶体部分。 PM 测试的先决条件是制备稳定的分散体。然而，测试困难可能是由于纳米级颗粒物分散在测试介质中时本质上不稳定，导致需要区分测试材料引起的潜在化学效应和物理效应。对不稳定颗粒物的水生测试可能会导致不一致和不均匀的吸收和暴露场景，从而在各自的测试系统中观察到影响。鉴于 PM 及其团聚体的尺寸不断变化，保持稳定的暴露条件通常非常具有挑战性，需要观察到的终点基于水相中存在的测量浓度和粒径分布，同时忽略团聚和沉降的颗粒。在本文中，我们描述了 PM 测试的现状，展示了水生测试中 PM 特定的挑战（例如，测试持续时间、物理效应、不稳定性、生物降解、生物累积），重点关注 NM，考虑一组最相关的 TG，并提供建议的测试注意事项，以优化 PM 的水生测试。