Microplastic pollution: a review of specific blood-tissue barrier breaches and health effects

Microplastic (1 μm - 5 mm) and nanoplastic (<1 μm) pollution is a heightening global challenge affecting the environment and the health of living creatures within. As primary precursors for plastic manufacturing, microplastics predominantly get into the environment through plastic product degradation and integrate into water, food chain and consumer products leading to potential health consequences. The mammalian system is equipped with several blood-tissue barriers with exclusive tight junctions that selectively regulate material transfer and protect vulnerable and functionally important organs. Nonetheless, emerging evidence indicates microplastics interact, traverse and compromise the integrity of these complex barriers. This review summarises the known and potential impact of microplastics on human health, focusing on specific organ barrier breaches. Evidence of microplastic traversal and deposition in distal mammalian organs are discussed. We further highlight current challenges facing both researchers and clinicians and provide an outlook for expanding our understanding of the impact of microplastic on health.