Microplastic particles are ubiquitous in the environment, from the air we breathe to the food we eat. The key question with respect to these particles is to what extent they cause risks for the environment and human health. There is no risk assessment framework that takes into account the multidimensionality of microplastic particles against the background of numerous natural particles, which together encompass an infinite combination of sizes, shapes, densities and chemical signatures. We review the current tenets in defining microplastic characteristics and effects, emphasizing advances in the analysis of the diversity of microplastic particles. We summarize the unique characteristics of microplastic compared with those of other environmental particles, the main mechanisms of microplastic particle effects and the relevant dose metrics for these effects. To characterize risks consistently, we propose how exposure and effect thresholds can be aligned and quantified using probability density functions describing microplastic particle diversity.

从我们呼吸的空气到我们吃的食物，微塑料颗粒在环境中无处不在。关于这些颗粒的关键问题是它们在多大程度上对环境和人类健康造成风险。没有风险评估框架考虑到微塑料颗粒在众多天然颗粒背景下的多维性，这些天然颗粒共同包含尺寸、形状、密度和化学特征的无限组合。我们回顾了当前定义微塑料特性和影响的原则，强调了在分析微塑料颗粒多样性方面取得的进展。我们总结了微塑料与其他环境颗粒相比的独特特性，微塑料粒子效应的主要机制和这些效应的相关剂量指标。为了一致地描述风险，我们建议如何使用描述微塑料颗粒多样性的概率密度函数来对齐和量化暴露和影响阈值。