Microplastics: challenges of assessment in biological samples and their implication for in vitro and in vivo effects

Microplastics (MPs) have attracted global interest because they have been recognized as emerging pollutants that require urgent attention. MPs are plastic particles with a size between 1 micron and 5 millimeters (1 µm-5mm); those measuring less than 1 µm are known as nanoplastics (NPs). MPs are distributed in the environment in various physical forms that depend on the original morphology of the primary plastics, the degradation process, and the erosion factors to which they were subjected. Humans may be exposed to these pollutants mainly by ingestion or inhalation, which could adversely affect human health. This review focuses on exposure pathways, sources, and evidence of adverse effects reported in vitro and in vivo studies. In addition , we highlight the application of methods and techniques to assess the precise levels of exposure to MPs in biological samples to generate knowledge about their potential threat to human health.