Microplastics negatively impact ecosystems, human health and cellular proteostasis.

With the widespread use of plastics for both personal and industrial applications, significant amounts of micro- and nano-sized plastic particles (MNPs) are entering our air and waterways. This impacts ecosystems, triggers the formation of biofilms and facilitates the emergence of antibiotic-resistant bacteria. Moreover, direct human exposure to MNPS is inevitable and occurs primarily through ingestion and inhalation. Once internalized, MNPs cause oxidative stress and inflammation. Within tissue matrices, proteins and other macromolecules adhere to MNPs, forming a coating referred to as a corona. This corona provides the MNPs with biological identity that increases their propensity to enter cells and breach the blood-brain barrier. From a proteostasis perspective, proteins that physically interact with MNPs undergo conformational changes that result in the formation of a rigid β-sheet structure. This leads to amyloidogenesis in a manner that may pose a risk for neurodegenerative disease. This review synthesizes what is known about the properties of microplastics (MPs), their ecological impacts and their impacts on human health-with an emphasis on the ways that MP may interfere with the ability of cells and organisms to maintain healthy proteostasis. This article is part of the Theo Murphy meeting issue 'ProteostaSys: a systems view of proteostasis'.