Microplastics have recently become a growing environmental issue, whereas the smaller fractions, nanoplastics, have received less attention. Due to their small size, nanoplastics may affect organisms differently and potentially more severely than larger microplastics. In natural environments nanoplastics also interact with organic material and form larger aggregates, which may, potentially, reduce their toxicity as they grow in size. We tested the change in toxicity towards Daphnia magna by controlling the size of the aggregates of positively charged 50 nm polystyrene nanoplastics, which are highly toxic as single particles. We show that although 200 to 500 nm nanoplastics are not toxic, aggregates of 50 nm nanoplastics in the same size range are at least as toxic as the free, 50 nm, nanoplastics. Hence, an increase in size through aggregation, a process likely to occur as nanoparticles enter natural ecosystems, does not reduce toxicity. In a broader context this finding provides a firm basis for societal decision making regarding the potency of nanoparticles as they enter natural ecosystems.

中文翻译：

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蛋白质控制的聚苯乙烯纳米塑料的聚集不会降低对大型蚤的毒性

近年来，微塑料已成为一个日益严重的环境问题，而较小的部分即纳米塑料受到的关注较少。由于纳米塑料的尺寸小，因此与较大的塑料相比，其对生物的影响可能不同，甚至可能更严重。在自然环境中，纳米塑料还可以与有机材料相互作用并形成较大的聚集体，这可能会随着其尺寸的增加而降低其毒性。我们测试了对水蚤的毒性变化通过控制带正电的50 nm聚苯乙烯纳米塑料聚集体的大小，该聚集体作为单个颗粒具有很高的毒性。我们表明，尽管200至500 nm纳米塑料无毒，但在相同尺寸范围内的50 nm纳米塑料的聚集体的毒性至少与游离的50 nm纳米塑料一样。因此，通过聚集而增加尺寸（该过程可能随着纳米颗粒进入自然生态系统而发生）不会降低毒性。在更广泛的背景下，这一发现为纳米颗粒进入自然生态系统时的效能做出社会决策提供了坚实的基础。