Current opinion: What is a nanoplastic?

https://doi.org/10.1016/j.envint.2022.107199

Discovery and quantification of plastic particle pollution in human blood.

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.

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Emergence of Nanoplastic in the Environment and Possible Impact on Human Health

Most microplastics are emitted, either directly or via the degradation of plastics, to the terrestrial environment and accumulate in large amounts in soils, representing a potential threat to terrestrial ecosystems. It is very important to evaluate the uptake of microplastics by crop plants because of the ubiquity of microplastics in wastewaters often used for agricultural irrigation worldwide. Here, we analyse the uptake of different microplastics by crop plants (wheat (Triticum aestivum) and lettuce (Lactuca sativa)) from treated wastewater in hydroponic cultures and in sand matrices or a sandy soil. Our results provide evidence in support of submicrometre- and micrometre-sized polystyrene and polymethylmethacrylate particles penetrating the stele of both species using the crack-entry mode at sites of lateral root emergence. This crack-entry pathway and features of the polymeric particles lead to the efficient uptake of submicrometre plastic. The plastic particles were subsequently transported from the roots to the shoots. Higher transpiration rates enhanced the uptake of plastic particles, showing that the transpirational pull was the main driving force of their movement. Our findings shed light on the modes of plastic particle interaction with plants and have implications for crops grown in fields contaminated with wastewater treatment discharges or sewage sludges. The presence of microplastics in wastewaters used for irrigation highlights the urgency of analysing the possible uptake of microplastics by crop plants. This study shows that submicrometre and micrometre plastic particles from treated wastewater enter the steles of crop plants via a crack entry at sites of lateral root emergence.

Effective uptake of submicrometre plastics by crop plants via a crack-entry mode

Marine plastic debris floating on the ocean surface is a major environmental problem. However, its distribution in the ocean is poorly mapped, and most of the plastic waste estimated to have entered the ocean from land is unaccounted for. Better understanding of how plastic debris is transported from coastal and marine sources is crucial to quantify and close the global inventory of marine plastics, which in turn represents critical information for mitigation or policy strategies. At the same time, plastic is a unique tracer that provides an opportunity to learn more about the physics and dynamics of our ocean across multiple scales, from the Ekman convergence in basin-scale gyres to individual waves in the surfzone. In this review, we comprehensively discuss what is known about the different processes that govern the transport of floating marine plastic debris in both the open ocean and the coastal zones, based on the published literature and referring to insights from neighbouring fields such as oil spill dispersion, marine safety recovery, plankton connectivity, and others. We discuss how measurements of marine plastics (both in situ and in the laboratory), remote sensing, and numerical simulations can elucidate these processes and their interactions across spatio-temporal scales.

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The physical oceanography of the transport of floating marine debris

Plastics can be found in all ecosystems across the globe. This type of environmental pollution is important, even if its impact is not fully understood. The presence of small plastic particles at the micro- and nanoscales is of growing concern, but nanoplastic has not yet been observed in natural samples. In this study, we examined four size fractions (meso-, large micro-, small micro-, and nanoplastics) of debris collected in the North Atlantic subtropical gyre. To obtain the nanoplastic portion, we isolated the colloidal fraction of seawater. After ultrafiltration, the occurrence of nanoscale particles was demonstrated using dynamic light scattering experiments. The chemical fingerprint of the colloids was obtained by pyrolysis coupled with gas chromatography–mass spectrometry. We demonstrated that the signal was anthropogenic and attributed to a combination of plastics. The polymer composition varied among the size classes. At the micro- and nanoscales, polyvinyl chloride, polyethylene terephthalate, p...

Nanoplastic in the North Atlantic Subtropical Gyre.

Estimates of cumulative plastic inputs into the oceans are expressed in hundred million tons, whereas the total mass of microplastics afloat at sea is 3 orders of magnitude below this. This large gap is evidence of our ignorance about the fate of plastics, as well as transformations and sinks in the oceans. One of the current challenges consists of identifying and quantifying plastic particles at the microscale, the small microplastics (SMP, 25–1000 μm). The aim of the present study is to investigate SMP concentration in count and in mass at the sea surface in the North Atlantic subtropical gyre during the sea campaign Expedition 7th Continent. After isolation, SMP were characterized by micro-Fourier-transform infrared spectroscopy. Microplastic distribution was modeled by a wind-driven vertical mixing correction model taking into account individual particle properties (dimension, shape and density). We demonstrate that SMP buoyancy is significantly decreased compared to the large microplastics (LMP, 1–5 mm) and consequently more susceptible to vertical transport. The uncorrected LMP concentration in count was between 13 000 and 174 000 pieces km–2, and was between 5 and 170 times more abundant for SMP. With a wind-driven vertical mixing correction, we estimated that SMP were 300 to 70 000 times more abundant than LMP. When discussing this in terms of weight after correction, LMP concentrations were between 50 and 1000 g km–2, and SMP concentrations were between 5 and 14 000 g km–2.

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Laurent Brach

Papers

Nanoplastic in the North Atlantic Subtropical Gyre.

Small Microplastics As a Main Contributor to Plastic Mass Balance in the North Atlantic Subtropical Gyre

Anticyclonic eddies increase accumulation of microplastic in the North Atlantic subtropical gyre