Absorption, distribution, metabolism, excretion and toxicity of microplastics in the human body and health implications

Microplastics (MPs; <5 mm) in the biosphere draws public concern about their potential health impacts. Humans are potentially exposed to MPs via ingestion, inhalation, and dermal contact. Ingestion and inhalation are the two major exposure pathways. An adult may consume approximately 5.1 × 103 items from table salts and up to 4.1 × 104 items via drinking water annually. Meanwhile, MP inhalation intake ranges from 0.9 × 104 to 7.9 × 104 items per year. The intake of MPs would be further distributed in different tissues and organs of humans depending on their sizes. The excretion has been discussed with the possible clearance ways (e.g., urine and feces). The review summarized the absorption, distribution, metabolic toxicity and excretion of MPs together with the attached chemicals. Moreover, the potential implications on humans are also discussed from in vitro and in vivo studies, and connecting the relationship between the physicochemical properties and the potential risks. This review will contribute to a better understanding of MPs as culprits and/or vectors linking to potential human health hazards, which will help outline the promising areas for further revealing the possible toxicity pathways.