On account of environmental concerns, the fate and adverse effects of plastics have attracted considerable interest in the past few years. Recent studies have indicated the potential for fragmentation of plastic materials into nanoparticles, i.e., "nanoplastics," and their possible accumulation in the environment. Nanoparticles can show markedly different chemical and physical properties than their bulk material form. Therefore possible risks and hazards to the environment need to be considered and addressed. However, the fate and effect of nanoplastics in the (aquatic) environment has so far been little explored. In this review, we aim to provide an overview of the literature on this emerging topic, with an emphasis on the reported impacts of nanoplastics on human health, including the challenges involved in detecting plastics in a biological environment. We first discuss the possible sources of nanoplastics and their fates and effects in the environment and then describe the possible entry routes of these particles into the human body, as well as their uptake mechanisms at the cellular level. Since the potential risks of environmental nanoplastics to humans have not yet been extensively studied, we focus on studies demonstrating cell responses induced by polystyrene nanoparticles. In particular, the influence of particle size and surface chemistry are discussed, in order to understand the possible risks of nanoplastics for humans and provide recommendations for future studies.

Realization of the immense potential of nanomaterials for biomedical applications will require a thorough understanding of how they interact with cells, tissues, and organs. There is evidence that, depending on their physicochemical properties and subsequent interactions, nanomaterials are indeed taken up by cells. However, the subsequent release and/or intracellular degradation of the materials, transfer to other cells, and/or translocation across tissue barriers are still poorly understood. The involvement of these cellular clearance mechanisms strongly influences the long-term fate of used nanomaterials, especially if one also considers repeated exposure. Several nanomaterials, such as liposomes and iron oxide, gold, or silica nanoparticles, are already approved by the American Food and Drug Administration for clinical trials; however, there is still a huge gap of knowledge concerning their fate in the body. Herein, clinically relevant nanomaterials, their possible modes of exposure, as well as the biological barriers they must overcome to be effective are reviewed. Furthermore, the biodistribution and kinetics of nanomaterials and their modes of clearance are discussed, knowledge of the long-term fates of a selection of nanomaterials is summarized, and the critical points that must be considered for future research are addressed.

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The plausibility of human exposure to microplastics has increased within the last years. Microplastics have been found in different food types including seafood, salt, sugar and beverages. So far, human health effects of microplastics after ingestion are unknown. Herein, we designed a novel, three-dimensional in vitro intestinal model consisting of the human intestinal epithelial cell lines Caco-2 and HT29-MTX-E12 as well as human blood monocyte-derived macrophages and dendritic cells that is suitable to assess the possible effects of ingested microplastics. Relevant microplastic particles (in the order of 50-500 µm), including polymers representing tire wear and polyolefins, which represent major sources of microplastic in the EU, were compared to other polymer classes and an inorganic microparticle, healing earth, which is intended for human consumption. Microplastic particles were exposed at concentrations of 823.5-1380.0 µg/cm 2 to the model using a dry powder insufflator system to aerosolize the particles directly on the intestinal model's surface. Cytotoxicity was investigated after 6, 24 and 48 h of exposure via measuring the release of lactate dehydrogenase. Inflammatory end points including the cytokines IL-8, TNFα and IL-1β as well as changes of the barrier integrity after exposure were additionally monitored. We demonstrated that all of the microplastics and the healing earth particles did not cause any significant cytotoxicity or release of (pro-)inflammatory cytokines and did not change the barrier integrity of the co-culture at any of the time points investigated.

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This work aims to establish a production and characterization protocol for fluorescent plastic nanoparticles of poly(ethylene terephthalate) (PET), polypropylene (PP), and polystyrene (PS) that can be tracked in biological environments.

As the production of plastic products continues to increase, determining the fate of plastic waste in the environment is of high importance. Densely populated areas, such as Mediterranean coastlines, represent locations of high pollution risk for surrounding environments. Thus, this study aims to assess the abundance, size, and composition of floating meso-and microplastics collected during four weeks in 2018 in the Ligurian and Tyrrhenian Seas. The results show average meso-and microplastic particle concentrations of 28,376 ± 28,917 particles km −2 , and an average mass of 268.61 ± 421.18 g km −2. The particle shape ratio was 65% fragments, 19% films, 10% lines, 4% foams, and 2% pellets. Microplastic particles comprised 65% of the sample. Analysis with attenuated total reflection Fourier transform infrared spectroscopy showed predominant polymer types included polyethylene, polypropylene, polystyrene, and polyamide. These data are an important starting point for long-term monitoring of plastic pollution levels within this region.