Evidence from in vitro and in vivo studies on the potential health repercussions of micro- and nanoplastics

Plastic is a synthetic or semisynthetic polymer with numerous physicochemical properties, and its fragmentation can give rise to microplastics (MPs) and nanoplastics (NPs). These particles can enter our ecosystem, where a process of constant degradation facilitates their dispersion and absorption by different species, affecting multiple organs and systems. The objective of this review was to provide an update on the potential health effects of MPs and NPs indicated by in vitro and in vivo studies. In vitro studies have described the absorption of plastic particles of different sizes and have documented their proinflammatory effects and genotoxicity, which can lead to the structural alteration of cells. MPs and NPs have also been implicated in the development of antibiotic resistance. In vivo studies have demonstrated that MPs and NPs can access organisms via dietary and respiratory pathways and through the epidermis. Their reported effects include: changes in microbiota and digestive enzyme production; inflammatory processes at respiratory level; circulatory and reproductive system disorders; and neurotoxicity, inducing behavioral changes. In vitro and in vivo studies have evidenced detrimental effects in different organs and systems as a function of the dose, size, and chemical properties of plastic particles. Further research is warranted to determine the effects on human health of these particles at environmental doses.