A Review of Microplastic Ingestion, Translocation, and Egestion by Organisms — Do Organisms Ingest and Then Excrete Microplastics?

In this review, data on the ingestion, translocation and egestion of microplastics by different organisms are analysed and summarized to predict the behaviour of microplastics in human body. Microplastics translocation from the gastrointestinal tract to the circulatory system or tissue are associated with the species and groups of organisms and the size of microplastics. Ingested microplastics are translocated to thoracic lymph nodes via macrophages and to the liver, kidney, spleen, heart, brain and secondary target organs via systemic circulation. In the ingestion, translocation, and egestion of microplastics by mammals, particles of >150 μm are rarely translocated or absorbed by organs (except the gut), characterized by a localization effect on the immune system or gut infection. Although microplastics <150 μm are linked to systemic exposure, their absorption remains limited with intense absorption restricted to particles <1.5μ m. Existing studies have focused on laboratory experiments to investigate microplastic concentrations in food, the type of plastics, and morphology (e.g., free or aggregate state, particle size, and shape). To further understand the behaviours of microplastics, systematic and comprehensive studies should be continued.