Nanoplastics: Status and Knowledge Gaps in the Finalization of Environmental Risk Assessments

Effects of polystyrene nanoplastic size on zebrafish embryo development

Polystyrene nanoplastics (PS) require a comprehensive evaluation of their toxicity and potential risks to humans and the environment. The zebrafish model, a well-established animal model increasingly utilized for nanotoxicity assessments, was employed in this study. Our research aimed to explore the toxic effects of PS with sizes of 30, 100, 200, and 450 nm on zebrafish embryos. Exposure experiments were conducted on embryos at 4 h post-fertilization (hpf) using various concentrations of nanoparticles (20, 40, 60, 80, and 100 mg/L) until 96 hpf. Notably, PS ranging from 100 to 450 nm did not adversely affect zebrafish embryo development. However, PS with a size of 30 nm at a concentration of 100 mg/L resulted in embryo mortality but not embryonic malformations. Furthermore, our investigation confirmed the uptake of these nanoparticles by zebrafish larvae following the opening of their mouths, with the particles being found predominantly in the digestive system of the larvae. Additionally, 30 nm PS were found to significantly modulate the expression levels of genes associated with oxidative stress and apoptosis. These findings highlight the developmental impacts of 30 nm PS on zebrafish embryos, raising concerns about potential similar consequences in humans. Considering our findings, it is essential to encourage further research into the management and regulation of PS to mitigate their potential environmental and health impacts.

Nanoplastics composite norfloxacin induced changes in conformation and function of lysozyme and differential effects of co-exposure contamination

The concurrent environmental contamination by nanoplastics (NPs) and norfloxacin (NOR) is a burgeoning concern, with significant accumulations in various ecosystems and potential ingress into the human body via the food chain, posing threats to both public health and ecological balance. Despite the gravity of the situation, studies on the co-exposure contamination effects of these substances are limited. Moreover, the response mechanisms of key functional proteins to these pollutants are yet to be fully elucidated. In this work, we conducted a comprehensive assessment of the interaction mechanisms of NPs and NOR with lysozyme under both single and co-exposure condition, utilizing dynamic light scattering, ζ-potential measurements, multi-spectroscopy methods, enzyme activity assays and molecular docking, to obtain a relationship between the compound effects of NPs and NOR. Our results indicate that NPs adsorb NOR on their surface, forming more stable aggregates. These aggregates influence the conformation, secondary structure (α-Helix ratio decreased by 3.1 %) and amino acid residue microenvironment of lysozyme. And changes in structure affect the activity of lysozyme (reduced by 39.9 %) with the influence of composited pollutants exerting stronger changes. Molecular simulation indicated the key residues Asp 52 for protein function located near the docking site, suggesting pollutants preferentially binds to the active center of lysozyme. Through this study, we have found the effect of increased toxicity on lysozyme under the compounded conditions of NPs and NOR, confirming that the increased molecular toxicity of NPs and NOR is predominantly realized through the increase in particle size and stability of the aggregates under weak interactions, as well as induction of protein structural looseness. This study proposes a molecular perspective on the differential effects and mechanisms of NPs-NOR composite pollution, providing new insights into the assessment of in vitro responses to composite pollutant exposure.

Local thermal adaption mediates the sensitivity of Daphnia magna to nanoplastics under global warming scenarios

The toxicity of nanoplastics at environmentally relevant concentrations has received widespread attention in the context of global warming. Despite numerous studies on the impact of mean temperature (MT), the effects of daily temperature fluctuations (DTFs) on the ecotoxicity of nanoplastics remains largely unexplored. Moreover, the role of evolutionary adaptation in assessing long-term ecological risks is unclear. Here, we investigated the effects of polystyrene nanoplastics (5 μg L-1) on Daphnia magna under varying MT (20 °C and 24 °C) and DTFs (0 °C, 5 °C, and 10 °C). Capitalizing on a space-for-time substitution approach, we further assessed how local thermal adaptation affect the sensitivity of Daphnia to nanoplastics under global warming. Our results indicated that nanoplastics exposure in general reduced heartbeat rate, thoracic limb activity and feeding rate, and increased CytP450, ETS activity and Hgb concentrations. Higher MT and DTFs enhanced these effects. Notably, clones originating from their respective sites performed better under their native temperature conditions, indicating local thermal adaptation. Warm-adapted low-latitude D. magna showed stronger nanoplastics-induced increases in CytP450, ETS activity and Hgb concentrations under local MT 24 °C, while cold-adapted high-latitude D. magna showed stronger nanoplastics-induced decreases in heartbeat rate, thoracic limb activity and feeding rate under high MT than under low MT.

Detection of submicron- and nanoplastics spiked in environmental fresh- and saltwater with Raman spectroscopy

Detection of small plastic particles in environmental water samples has been a topic of increasing interest in recent years. A multitude of techniques, such as variants of Raman spectroscopy, have been employed to facilitate their analysis in such complex sample matrices. However, these studies are often conducted for a limited number of plastic types in matrices with relatively little additional materials. Thus, much remains unknown about what parameters influence the detection limits of Raman spectroscopy for more environmentally relevant samples. To address this, this study utilizes Raman spectroscopy to detect six plastic particle types; 161 and 33 nm polystyrene, < 450 nm and 36 nm poly(ethylene terephthalate), 121 nm polypropylene, and 126 nm polyethylene; spiked into artificial saltwater, artificial freshwater, North Sea, Thames River, and Elbe River water. Overall, factors such as plastic particle properties, water matrix composition, and experimental setup were shown to influence the final limits of detection.

Co-exposure to polystyrene nanoplastics and triclosan induces synergistic cytotoxicity in human KGN granulosa cells by promoting reactive oxygen species accumulation

In recent years, nanoplastics (NPs) and triclosan (TCS, a pharmaceutical and personal care product) have emerged as environmental pollution issues, and their combined presence has raised widespread concern regarding potential risks to organisms. However, the combined toxicity and mechanisms of NPs and TCS remain unclear. In this study, we investigated the toxic effects of polystyrene NPs and TCS and their mechanisms on KGN cells, a human ovarian granulosa cell line. We exposed KGN cells to NPs (150 μg/mL) and TCS (15 μM) alone or together for 24 hours. Co-exposure significantly reduced cell viability. Compared with exposure to NPs or TCS alone, co-exposure increased reactive oxygen species (ROS) production. Interestingly, co-exposure to NPs and TCS produced synergistic effects. We examined the activity of superoxide dismutase (SOD) and catalase (CAT), two antioxidant enzymes; it was significantly decreased after co-exposure. We also noted an increase in the lipid oxidation product malondialdehyde (MDA) after co-exposure. Furthermore, co-exposure to NPs and TCS had a more detrimental effect on mitochondrial function than the individual treatments. Co-exposure activated the NRF2-KEAP1-HO-1 antioxidant stress pathway. Surprisingly, the expression of SESTRIN2, an antioxidant protein, was inhibited by co-exposure treatments. Co-exposure to NPs and TCS significantly increased the autophagy-related proteins LC3B-II and LC3B-Ⅰ and decreased P62. Moreover, co-exposure enhanced CASPASE-3 expression and inhibited the BCL-2/BAX ratio. In summary, our study revealed the synergistic toxic effects of NPs and TCS in vitro exposure. Our findings provide insight into the toxic mechanisms associated with co-exposure to NPs and TCS to KGN cells by inducing oxidative stress, activations of the NRF2-KEAP1-HO-1 pathway, autophagy, and apoptosis.

Submicron- and nanoplastic detection at low micro- to nanogram concentrations using gold nanostar-based surface-enhanced Raman scattering (SERS) substrates

The presence of submicron- (1 μm-100 nm) and nanoplastic (<100 nm) particles within various sample matrices, ranging from marine environments to foods and beverages, has become a topic of increasing interest in recent years. Despite this interest, very few analytical techniques are known that allow for the detection of these small plastic particles in the low concentration ranges that they are anticipated to be present at. Research focused on optimizing surface-enhanced Raman scattering (SERS) to enhance signal obtained in Raman spectroscopy has been shown to have great potential for the detection of plastic particles below conventional resolution limits. In this study, we produce SERS substrates composed of gold nanostars and assess their potential for submicron- and nanoplastic detection. The results show 33 nm polystyrene could be detected down to 1.25 μg mL-1 while 36 nm poly(ethylene terephthalate) was detected down to 5 μg mL-1. These results confirm the promising potential of the gold nanostar-based SERS substrates for nanoplastic detection. Furthermore, combined with findings for 121 nm polypropylene and 126 nm polyethylene particles, they highlight potential differences in analytical performance that depend on the properties of the plastics being studied.

Sublethal effects induced by different plastic nano-sized particles in Daphnia magna at environmentally relevant concentrations

A growing number of studies have reported the toxic effects of nanoplastics (NPs) on organisms. However, the focus of these studies has almost exclusively been on the use of polystyrene (PS) nanospheres. Herein, we aim to evaluate the sublethal effects on Daphnia magna juveniles of three different NP polymers: PS-NPs with an average size of 200 nm, polyethylene [PE] NPs and polyvinyl chloride [PVC] NPs with a size distribution between 50 and 350 nm and a comparable mean size. For each polymer, five environmentally relevant concentrations were tested (from 2.5 to 250 μg/L) for an exposure time of 48 h. NP effects were assessed at the biochemical level by investigating the amount of reactive oxygen species (ROS) and the activity of the antioxidant enzyme catalase (CAT) and at the behavioral level by evaluating the swimming behavior (distance moved). Our results highlight that exposure to PVC-NPs can have sublethal effects on Daphnia magna at the biochemical and behavioral levels. The potential role of particle size on the measured effects cannot be excluded as PVC and PE showed a wider size range distribution than PS, with particles displaying sizes from 50 to 350 nm. However, we infer that the chemical structure of PVC, which differs from that of PE of the same range size, concurs to explain the observed effects. Consequently, as PS seems not to be the most hazardous polymer, we suggest that the use of data on PS toxicity alone can lead to an underestimation of NP hazards.

The endocrine disrupting effects of nanoplastic exposure: A systematic review

Good mechanical properties and low costs have led to a global expansion of plastic production and use. Unfortunately, much of this material can be released into the environment as a waste product and cleaved into micro- and nanoplastics (NPs) whose impact on the environment and human health is still largely unknown. Considering the growing worldwide awareness on exposure to chemicals that can act as endocrine disruptors, a systematic review was performed to assess the impact of NPs on the endocrine function of in vitro and in vivo models. Although a limited number of investigations is currently available, retrieved findings showed that NPs may induce changes in endocrine system functionality, with evident alterations in reproductive and thyroid hormones and gene expression patterns, also with a trans-generational impact. Nanoplastic size, concentration, and the co-exposure to other endocrine disrupting pollutants may have an influencing role on these effects. Overall, although it is still too early to draw conclusions regarding the human health risks derived from NPs, these preliminary results support the need for further studies employing a wider range of plastic polymer types, concentrations, and time points as well as species and life stages to address a great variety of endocrine outcomes and to achieve a broader and shared consensus on the role of NPs as endocrine disruptors.

Formation, behavior, properties and impact of micro- and nanoplastics on agricultural soil ecosystems (A Review)

Micro and nanoplastics (MPs and NPs, respectively) in agricultural soil ecosystems represent a pervasive global environmental concern, posing risks to soil biota, hence soil health and food security. This review provides a comprehensive and current summary of the literature on sources and properties of MNPs in agricultural ecosystems, methodology for the isolation and characterization of MNPs recovered from soil, MNP surrogate materials that mimic the size and properties of soil-borne MNPs, and transport of MNPs through the soil matrix. Furthermore, this review elucidates the impacts and risks of agricultural MNPs on crops and soil microorganisms and fauna. A significant source of MPs in soil is plasticulture, involving the use of mulch films and other plastic-based implements to provide several agronomic benefits for specialty crop production, while other sources of MPs include irrigation water and fertilizer. Long-term studies are needed to address current knowledge gaps of formation, soil surface and subsurface transport, and environmental impacts of MNPs, including for MNPs derived from biodegradable mulch films, which, although ultimately undergoing complete mineralization, will reside in soil for several months. Because of the complexity and variability of agricultural soil ecosystems and the difficulty in recovering MNPs from soil, a deeper understanding is needed for the fundamental relationships between MPs, NPs, soil biota and microbiota, including ecotoxicological effects of MNPs on earthworms, soil-dwelling invertebrates, and beneficial soil microorganisms, and soil geochemical attributes. In addition, the geometry, size distribution, fundamental and chemical properties, and concentration of MNPs contained in soils are required to develop surrogate MNP reference materials that can be used across laboratories for conducting fundamental laboratory studies.

Detrimental effects of individual versus combined exposure to tetrabromobisphenol A and polystyrene nanoplastics in fish cell lines

The potential interactions between the diverse pollutants that can be released into the environment and the resulting outcomes are a challenging issue that needs to be further examined. This in vitro study was aimed to assess potential toxic effects caused by combined exposure to tetrabromobisphenol A, a flame retardant widely used and frequently detected in aquatic matrices, and commercially available polystyrene nanoparticles as reference material to evaluate nanoplastics risks. Our results, using freshwater fish cell lines and a set of relevant cytotoxicity endpoints including cell viability, oxidative stress, and DNA damage, provide additional mechanistic insights that could help to fully characterize the toxicity profiles of tetrabromobisphenol A and polystyrene nanoparticles. Furthermore, we describe subtle changes in cell viability as well as the generation of oxidative DNA damage after coexposure to subcytotoxic concentrations of the tested pollutants.

Nanoplastics in the soil environment: Analytical methods, occurrence, fate and ecological implications

Soils play a very important role in ecosystems sustainability, either natural or agricultural ones, serving as an essential support for living organisms of different kinds. However, in the current context of extremely high plastic pollution, soils are highly threatened. Plastics can change the chemical and physical properties of the soils and may also affect the biota. Of particular importance is the fact that plastics can be fragmented into microplastics and, to a final extent into nanoplastics. Due to their extremely low size and high surface area, nanoplastics may even have a higher impact in soil ecosystems. Their transport through the edaphic environment is regulated by the physicochemical properties of the soil and plastic particles themselves, anthropic activities and biota interactions. Their degradation in soils is associated with a series of mechanical, photo-, thermo-, and bio-mediated transformations eventually conducive to their mineralisation. Their tiny size is precisely the main setback when it comes to sampling soils and subsequent processes for their identification and quantification, albeit pyrolysis coupled with gas chromatography-mass spectrometry and other spectroscopic techniques have proven to be useful for their analysis. Another issue as a consequence of their minuscule size lies in their uptake by plants roots and their ingestion by soil dwelling fauna, producing morphological deformations, damage to organs and physiological malfunctions, as well as the risks associated to their entrance in the food chain, although current conclusions are not always consistent and show the same pattern of effects. Thus, given the omnipresence and seriousness of the plastic menace, this review article pretends to provide a general overview of the most recent data available regarding nanoplastics determination, occurrence, fate and effects in soils, with special emphasis on their ecological implications.