Plastic waste has been produced at a rapidly growing rate over the past several decades. The environmental impacts of plastic waste on marine and terrestrial ecosystems have been recognized for years. Recently, researchers found that micro- and nanoplastics (MNPs), micron (100 nm – 5 mm) and nanometer (1 – 100 nm) scale particles and fibers produced by degradation and fragmentation of plastic waste in the environment, have become an important emerging environmental and food chain contaminant with uncertain consequences for human health. This review provides a comprehensive summary of recent findings from studies of potential toxicity and adverse health impacts of MNPs in terrestrial mammals, including studies in both in vitro cellular and in vivo mammalian models. Also reviewed here are recently released biomonitoring studies that have characterized the bioaccumulation, biodistribution, and excretion of MNPs in humans. The majority MNPs in the environment to which humans are most likely to be exposed, are of irregular shapes, varied sizes, and mixed compositions, and are defined as secondary MNPs. However, the MNPs used in most toxicity studies to date were commercially available primary MNPs of polystyrene (PS), polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and other polymers. The emerging in vitro and in vivo evidence reviewed here suggests that MNP toxicity and bioactivity are largely determined by MNP particle physico-chemical characteristics, including size, shape, polymer type, and surface properties. For human exposure, MNPs have been identified in human blood, urine, feces, and placenta, which pose potential health risks. The evidence to date suggests that the mechanisms underlying MNP toxicity at the cellular level are primarily driven by oxidative stress. Nonetheless, large knowledge gaps in our understanding of MNP toxicity and the potential health impacts of MNP exposures still exist and much further study is needed to bridge those gaps. This includes human population exposure studies to determine the environmentally relevant MNP polymers and exposure concentrations and durations for toxicity studies, as well as toxicity studies employing environmentally relevant MNPs, with surface chemistries and other physico-chemical properties consistent with MNP particles in the environment. It is especially important to obtain comprehensive toxicological data for these MNPs to understand the range and extent of potential adverse impacts of microplastic pollutants on humans and other organisms.

过去几十年来，塑料废物的产生速度迅速增长。多年来人们已经认识到塑料废物对海洋和陆地生态系统的环境影响。最近，研究人员发现，环境中的塑料废物降解和破碎产生的微米级（100 nm – 5 mm）和纳米级（1 – 100 nm）颗粒和纤维等微纳米塑料（MNP）已成为重要的新兴塑料。对人类健康具有不确定后果的环境和食物链污染物。本综述全面总结了 MNP 对陆地哺乳动物的潜在毒性和不利健康影响的最新研究结果，包括体外细胞和体内哺乳动物模型的研究。本文还回顾了最近发布的生物监测研究，这些研究描述了 MNP 在人类中的生物蓄积、生物分布和排泄。人类最有可能接触的环境中的大多数 MNP 形状不规则、大小不一、成分混合，被定义为次生 MNP。然而，迄今为止，大多数毒性研究中使用的 MNP 都是市售的聚苯乙烯 (PS)、聚乙烯 (PE)、聚氯乙烯 (PVC)、聚对苯二甲酸乙二醇酯 (PET) 和其他聚合物的初级 MNP。这里回顾的新兴体外和体内证据表明，MNP 毒性和生物活性很大程度上取决于 MNP 颗粒的物理化学特性，包括尺寸、形状、聚合物类型和表面特性。对于人类暴露而言，已在人体血液、尿液、粪便和胎盘中发现了 MNP，这会带来潜在的健康风险。迄今为止的证据表明，MNP 在细胞水平上的毒性机制主要是由氧化应激驱动的。尽管如此，我们对 MNP 毒性和 MNP 暴露对健康的潜在影响的理解仍然存在巨大的知识差距，需要进一步的研究来弥补这些差距。这包括确定与环境相关的 MNP 聚合物的人群暴露研究以及毒性研究的暴露浓度和持续时间，以及采用与环境相关的 MNP 进行的毒性研究，其表面化学和其他物理化学性质与环境中的 MNP 颗粒一致。获得这些 MNP 的全面毒理学数据对于了解微塑料污染物对人类和其他生物体潜在不利影响的范围和程度尤为重要。