Potential adverse health effects of ingested micro- and nanoplastics on humans. Lessons learned from <i>in vivo</i> and <i>in vitro</i> mammalian models

In recent years, increasing global attention has focused on "microplastics" (MPs) and "nanoplastics" (NPs) resulting in many studies on the effects of these compounds on ecological and environmental aspects. These tiny particles (<5000 µm), predominantly derived from the degradation of plastics, pollute the marine and terrestrial ecosystems with the ability to enter into the food chain. In this manner, human consumption of food contaminated with MPs or NPs is unavoidable, but the related consequences remain to be determined. The aim of this review is to complement previous reviews on this topic by providing new studies related to exposure, absorption, and toxicity in mammalian <i>in vivo</i> and <i>in vitro</i> systems. With respect to novel information, gaps and limitations hindering attainment of firm conclusions as well as preparation of a reliable risk assessment are identified. Subsequently, recommendations for <i>in vivo</i> and <i>in vitro</i> testing methods are presented in order to perform further relevant and targeted research studies.