Effects of microplastics on the immune system: How much should we worry?

• Prolonged exposure to microplastics can be harmful to human health. • Microplastics have been detected in several human tissues. • Microplastics pose a significant risk to human health, the long-term effects of which are unknown. • Experimental animal models and in vitro studies can help to understand the biodistribution of microplastics in the body and how they affect cellular pathology. • The lack of consistency between in vivo/in vitro experimental paradigms make it difficult to draw definitive conclusions. Plastics are everywhere. It is widely recognized that they represent a global problem, the extent of which is yet to be defined. Humans are broadly exposed to plastics, whose effects and consequences are poorly characterized so far. The main route of exposure is via alimentary and respiratory intake. Plastics pollutions may come from both: water and food contamination itself, and their packaging. The smaller sizes ( i.e. microplastics <150 µm - MPs) are considered to be the most pervasive of living organisms and, therefore, potentially the most harmful. As humans occupy one of the apex positions of the food chain, we are exposed to bioaccumulation and biomagnification effects of MPs. In fact, MPs are commonly found in human stools and blood. However, there are no data available yet on their ability to accumulate and to produce detrimental consequences on biological systems. Even though the effects of plastics pollution are poorly studied in mammals, including humans, they appear to have inflammatory effects, which is rather concerning as many etiologies of disease are based on a pro-inflammatory status.