Molecular toxicity of nanoplastics involving in oxidative stress and desoxyribonucleic acid damage

Polystyrene nanoplastics synergistically exacerbate diclofenac toxicity in embryonic development and the health of adult zebrafish

In this study, we investigated the possible ecotoxicological effect of co-exposure to polystyrene nanoplastics (PS-NPs) and diclofenac (DCF) in zebrafish (Danio rerio). After six days of exposure, we noticed that the co-exposure to PS-NP (100 μg/L) and DCF (at 50 and 500 μg/L) decreased the hatching rate and increased the mortality rate compared to the control group. Furthermore, we noted that larvae exposed to combined pollutants showed a higher frequency of morphological abnormalities and increased oxidative stress, apoptosis, and lipid peroxidation. In adults, superoxide dismutase and catalase activities were also impaired in the intestine, and the co-exposure groups showed more histopathological alterations. Furthermore, the TNF-α, COX-2, and IL-1β expressions were significantly upregulated in the adult zebrafish co-exposed to pollutants. Based on these findings, the co-exposure to PS-NPs and DCF has shown an adverse effect on the intestinal region, supporting the notion that PS-NPs synergistically exacerbate DCF toxicity in zebrafish.

The effects of micro- and nanoplastics on the central nervous system: A new threat to humanity?

Given the widespread production and use of plastics, poor biodegradability, and inadequate recycling, micro/nanoplastics (MNPs) have caused widespread environmental pollution. As a result, humans inevitably ingest MNPs through various pathways. However, there is still no consensus on whether exposure to MNPs has adverse effects on humans. This article aims to provide a comprehensive overview of the knowledge of MNPs and the potential mechanisms of their impact on the central nervous system. Numerous in vivo and in vitro studies have shown that exposure to MNPs may pass through the blood-brain barrier (BBB) and lead to neurotoxicity through impairments in oxidative and inflammatory balance, neurotransmitter alternation, nerve conduction-related key enzymes, and impact through the gut-brain axis. It is worth noting that MNPs may act as carriers and have more severe effects on the body when co-exposed with other substances. MNPs of smaller sizes cause more severe harm. Despite the scarcity of reports directly relevant to humans, this review brings together a growing body of evidence showing that exposure to MNPs disturbs neurons and has even been found to alter the memory and behavior of organisms. This effect may lead to further potential negative influence on the central nervous system and contribute to the development of other diseases such as central nervous system inflammation and Parkinson 's-like neurodegenerative disorders. There is a need further to investigate the threat of MNPs to human health.

Are bioplastics safe? Hazardous effects of polylactic acid (PLA) nanoplastics in Drosophila

The expanded uses of bioplastics require understanding the potential health risks associated with their exposure. To address this issue, Drosophila melanogaster as a versatile terrestrial in vivo model was employed, and polylactic acid nanoplastics (PLA-NPLs), as a proxy for bioplastics, were tested as a material model. Effects were determined in larvae exposed for 4 days to different concentrations (25, 100, and 400 μg/mL) of 463.9 ± 129.4 nm PLA-NPLs. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) approaches permitted the detection of PLA-NPLs in the midgut lumen of Drosophila larvae, interacting with symbiotic bacteria. Enzymatic vacuoles were observed as carriers, collecting PLA-NPLs and enabling the crossing of the peritrophic membrane, finally internalizing into enterocytes. Although no toxic effects were observed in egg-to-adult survival, cell uptake of PLA-NPLs causes cytological disturbances and the formation of large vacuoles. The translocation across the intestinal barrier was demonstrated by their presence in the hemolymph. PLA-NPL exposure triggered intestinal damage, oxidative stress, DNA damage, and inflammation responses, as evaluated via a wide set of marker genes. Collectively, these structural and molecular interferences caused by PLA-NPLs generated high levels of oxidative stress and DNA damage in the hemocytes of Drosophila larvae. The observed effects point out the need for further studies aiming to deepen the health risks of bioplastics before adopting their uses as a safe plastic alternative.

Micro(nano)plastics and Their Potential Impact on Human Gut Health: A Narrative Review

Microplastics and nanoplastics (MNPs) are becoming an increasingly severe global problem due to their widespread distribution and complex impact on living organisms. Apart from their environmental impact, the effects of MNPs on living organisms have also continued to attract attention. The harmful impact of MNPs has been extensively documented in marine invertebrates and larger marine vertebrates like fish. However, the research on the toxicity of these particles on mammals is still limited, and their possible effects on humans are poorly understood. Considering that MNPs are commonly found in food or food packaging, humans are primarily exposed to them through ingestion. It would be valuable to investigate the potential harmful effects of these particles on gut health. This review focuses on recent research exploring the toxicological impacts of micro- and nanoplastics on the gut, as observed in human cell lines and mammalian models. Available data from various studies indicate that the accumulation of MNPs in mammalian models and human cells may result in adverse consequences, in terms of epithelial toxicity, immune toxicity, and the disruption of the gut microbiota. The paper also discusses the current research limitations and prospects in this field, aiming to provide a scientific basis and reference for further studies on the toxic mechanisms of micro- and nanoplastics.

Plastic vs. glass: the effect of the synthetic material in contact with DMEK tissue during staining on endothelial cell loss

PURPOSE

Endothelial cell loss (ECL) during Descemet membrane endothelial keratoplasty (DMEK) graft preparation has been shown to affect graft survival and the need for re-grafting. The purpose of this study was to quantitatively assess the impact of the plastic and glass mediums in contact with DMEK donor tissue during intra-operative graft staining on ECL.

METHODS

Retrospective study that included patients who underwent DMEK surgery between January 2019 and June 2021 at Hôpital Maisonneuve-Rosemont and the Jewish General Hospital in Montreal, Canada. DMEK grafts were stained with 0.06% Trypan blue ophthalmic solution (VisionBlue®, Dutch Ophthalmic, USA, Exeter, NH) for 120 s in either a plastic or glass medium prior to delivery into the recipient's eye. The ECL was compared between the two groups 12-30 months post-operatively.

RESULTS

ECL at 12-30 months was significantly less in the eyes that had received grafts stained in a plastic medium compared to those stained in a glass medium. Graft survival and re-bubbling was higher in the glass group however this difference was not statistically significant.

CONCLUSION

Staining of the DMEK graft in a plastic medium caused less ECL compared to the glass medium.

Tissue damage, antioxidant capacity, transcriptional and metabolic regulation of red drum Sciaenops ocellatus in response to nanoplastics exposure and subsequent recovery

Nanoplastics are recognized as emerging contaminants that can cause severe toxicity to marine fishes. However, limited researches were focusing on the toxic effects of nanoplastics on marine fish, especially the post-exposure resilience. In this study, red drum (Sciaenops ocellatus) were exposed to 5 mg/L polystyrene nanoplastics (100 nm, PS-NPs) for a 7-day exposure experiment, and a 14-day recovery experiment that followed. The aim was to evaluate the dynamic alterations in hepatic and branchial tissue damage, hepatic antioxidant capacity, as well as hepatic transcriptional and metabolic regulation in the red drum during exposure and post-exposure to PS-NPs. Histopathological observation found that PS-NPs primarily triggered hepatic lipid droplets and branchial epithelial liftings, a phenomenon persistently discernible up to the 14 days of recovery. Although antioxidant capacity partially recovered during recovery periods, PS-NPs resulted in a sustained reduction in hepatic antioxidant activity, causing oxidative damage throughout the entire exposure and recovery phases, as evidenced by decreased total superoxide dismutase activities and increased malondialdehyde content. At the transcriptional and metabolic level, PS-NPs primarily induced lipid metabolism disorders, DNA damage, biofilm disruption, and mitochondrial dysfunction. In the gene-metabolite correlation interaction network, numerous CcO (cytochrome c oxidase) family genes and lipid metabolites were identified as key regulatory genes and metabolites in detoxification processes. Among them, the red drum possesses one additional CcO6B in comparison to human and zebrafish, which potentially contributes to its enhanced capacity for maintaining a stable and positive regulatory function in detoxification. This study revealed that nanoplastics cause severe biotoxicity to red drum, which may be detrimental to the survival of wild populations and affect the economics of farmed populations.

Regulation mechanisms of ferric ions release from iron-loaded transferrin protein caused by nano-sized polystyrene plastics-induced conformational and structural changes

Currently, the binding of iron-binding protein transferrin (TF) with NPs and their interaction mechanisms have not been completely elucidated yet. Here, we probed the conformation-dependent release of Fe ions from TF induced by nano-sized polystyrene plastics (PS-NPs) using dialysis, ICP-MS, multi-spectroscopic techniques, and computational simulation. The results showed that the release of free Fe ions from TF was activated after PS-NPs binding, which displayed a clear dose-effect correlation. PS-NPs binding can induce the unfolding and loosening of polypeptide chain and backbone of TF. Alongside this we found that the TF secondary structure was destroyed, thereby causing TF protein misfolding and denaturation. In parallel, PS-NPs interacted with the chromophores, resulting in the occurrence of fluorescence sensitization effects and the disruption of the surrounding micro-environment of aromatic amino acids. Also, the binding of PS-NPs induced the formation of new aggregates in the PS-NPs-TF system. Further simulations indicated that PS-NPs exhibited a preference for binding to the hinge region that connects the C-lobe and N-lobe, which is responsible for the Fe ions release and structural alterations of TF. This finding provides a new understanding about the regulation of the release of Fe ions of iron-loaded TF through NPs-induced conformational and structural changes.

Science-based evidence on pathways and effects of human exposure to micro- and nanoplastics

Human exposure to plastic particles has raised great concern among all relevant stakeholders involved in the protection of human health due to the contamination of the food chain, surface waters, and even drinking water as well as due to their persistence and bioaccumulation. Now more than ever, it is critical that we understand the biological fate of plastics and their interaction with different biological systems. Because of the ubiquity of plastic materials in the environment and their toxic potential, it is imperative to gain reliable, regulatory-relevant, science-based data on the effects of plastic micro- and nanoparticles (PMNPs) on human health in order to implement reliable risk assessment and management strategies in the circular economy of plastics. This review presents current knowledge of human-relevant PMNP exposure doses, pathways, and toxic effects. It addresses difficulties in properly assessing plastic exposure and current knowledge gaps and proposes steps that can be taken to underpin health risk perception, assessment, and mitigation through rigorous science-based evidence. Based on the existing scientific data on PMNP adverse health effects, this review brings recommendations on the development of PMNP-specific adverse outcome pathways (AOPs) following the AOP Users' Handbook of the Organisation for Economic Cooperation and Development (OECD).

Polystyrene nanoparticles induced mammalian intestine damage caused by blockage of BNIP3/NIX-mediated mitophagy and gut microbiota alteration

Nanoplastics possess the capacity for cellular internalization, and consequentially disrupt mitochondrial functionality, precipitating aberrations in energy metabolism. Given this, the potential accumulation of nanoplastics in alimentary sources presents a considerable hazard to the mammalian gastrointestinal system. While mitophagy serves as a cytoprotective mechanism that sustains redox homeostasis through the targeted removal of compromised mitochondria, the regulatory implications of mitophagy in nanoplastic-induced toxicity remain an underexplored domain. In the present investigation, polystyrene (PS) nanoparticles, with a diameter of 80 nm employed as a representative model to assess their toxicological impact and propensity to instigate mitophagy in intestinal cells both in vitro and in vivo. Data indicated that PS nanoparticles elicited BNIP3/NIX-mediated mitophagy within the intestinal milieu. Strikingly, the impediment of this degradation process at elevated concentrations was correlated with exacerbated pathological ramifications. In vitro assays corroborated that high-dosage cellular uptake of PS nanoparticles obstructed the mitophagy pathway. Furthermore, treatment with PS nanoparticles engendered alterations in gut microbiota composition and manifested a proclivity to modulate nutritional metabolism. Collectively, these findings elucidate that oral exposure to PS nanoparticles culminates in the inhibition of mitophagy and induces perturbations in the intestinal microbiota. This contributes valuable insights into the toxicological repercussions of nanoplastics on mammalian gastrointestinal health.

Micro- and nanoplastics (MNPs) and their potential toxicological outcomes: State of science, knowledge gaps and research needs

Plastic waste has been produced at a rapidly growing rate over the past several decades. The environmental impacts of plastic waste on marine and terrestrial ecosystems have been recognized for years. Recently, researchers found that micro- and nanoplastics (MNPs), micron (100 nm - 5 mm) and nanometer (1 - 100 nm) scale particles and fibers produced by degradation and fragmentation of plastic waste in the environment, have become an important emerging environmental and food chain contaminant with uncertain consequences for human health. This review provides a comprehensive summary of recent findings from studies of potential toxicity and adverse health impacts of MNPs in terrestrial mammals, including studies in both in vitro cellular and in vivo mammalian models. Also reviewed here are recently released biomonitoring studies that have characterized the bioaccumulation, biodistribution, and excretion of MNPs in humans. The majority MNPs in the environment to which humans are most likely to be exposed, are of irregular shapes, varied sizes, and mixed compositions, and are defined as secondary MNPs. However, the MNPs used in most toxicity studies to date were commercially available primary MNPs of polystyrene (PS), polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and other polymers. The emerging in vitro and in vivo evidence reviewed here suggests that MNP toxicity and bioactivity are largely determined by MNP particle physico-chemical characteristics, including size, shape, polymer type, and surface properties. For human exposure, MNPs have been identified in human blood, urine, feces, and placenta, which pose potential health risks. The evidence to date suggests that the mechanisms underlying MNP toxicity at the cellular level are primarily driven by oxidative stress. Nonetheless, large knowledge gaps in our understanding of MNP toxicity and the potential health impacts of MNP exposures still exist and much further study is needed to bridge those gaps. This includes human population exposure studies to determine the environmentally relevant MNP polymers and exposure concentrations and durations for toxicity studies, as well as toxicity studies employing environmentally relevant MNPs, with surface chemistries and other physico-chemical properties consistent with MNP particles in the environment. It is especially important to obtain comprehensive toxicological data for these MNPs to understand the range and extent of potential adverse impacts of microplastic pollutants on humans and other organisms.

Toxicity of microplastics and nanoplastics: invisible killers of female fertility and offspring health

Microplastics (MPs) and nanoplastics (NPs) are emergent pollutants, which have sparked widespread concern. They can infiltrate the body via ingestion, inhalation, and cutaneous contact. As such, there is a general worry that MPs/NPs may have an impact on human health in addition to the environmental issues they engender. The threat of MPs/NPs to the liver, gastrointestinal system, and inflammatory levels have been thoroughly documented in the previous research. With the detection of MPs/NPs in fetal compartment and the prevalence of infertility, an increasing number of studies have put an emphasis on their reproductive toxicity in female. Moreover, MPs/NPs have the potential to interact with other contaminants, thus enhancing or diminishing the combined toxicity. This review summarizes the deleterious effects of MPs/NPs and co-exposure with other pollutants on female throughout the reproduction period of various species, spanning from reproductive failure to cross-generational developmental disorders in progenies. Although these impacts may not be directly extrapolated to humans, they do provide a framework for evaluating the potential mechanisms underlying the reproductive toxicity of MPs/NPs.

Can the impact of micro- and nanoplastics on human health really be assessed using in vitro models? A review of methodological issues

Because of the many advantages they offer (strength, low cost, durability, lightweight, resistance, etc.), plastics are integral part of our daily life with a production constantly rising. However, their waste management is still inadequate, resulting in their release and accumulation in the environment, representing a main source of pollution. Their degradation results in debris of variable size including microplastics (0.1 μm-5 mm) and even nanoplastics (<0.1 μm), whose potential impact on ecosystems and human health have raised concerns. The potential adverse effects they may cause have been evaluated using both in vitro and in vivo models. However, due to some specific characteristics of micro- and nanoplastics, there are challenging questions about whether conventional in vitro tests are appropriate for evaluating their toxicity. For example, low-density plastics float on the surface of the culture medium and cannot come into contact with cells adhering to the bottom of the culture plates, which prevents proper evaluation of potential adverse effects and leads to misinterpretation of toxicological assays. In this review, we discuss the main issues related to the evaluation of micro- and nanoplastics toxicity using conventional in vitro assays. A literature survey has allowed to propose some solutions to circumvent these issues including the use of mathematical models to accurately determine the dose of particles delivered to cells, advanced 3D models (organoids), inverted cell culture models, cell cultures at the air-liquid interface or under dynamic conditions. Finally, we propose some perspectives and recommendations for further research on the in vitro evaluation of micro- and nanoplastics toxicity, underlining the importance of using standardized protocols for comparison purposes and samples and experimental conditions more representative of real-life exposure.

Benzo [a] pyrene-loaded aged polystyrene microplastics promote colonic barrier injury via oxidative stress-mediated notch signalling

The adsorption of toxic substances on polystyrene microplastics (PSMPs) can modify their biological toxicity and exacerbate the threat to human health. The effects of benzo [a] pyrene (B (a) P)-loaded aged PSMPs on colonic barrier integrity remains unclear. Here, we showed that binding environmentally relevant concentrations of B (a) P alteredl̥ the physicochemical features and markedly enhanced the toxicity of PSMPs. Compared to pristine PSMP, PSMP@B (a) P promoted colonic barrier degradation, body weight loss, colon length shortening, oxidative stress (OS), autophagy, inflammation, and bacterial translocation. Microplastic (MP) exposure induced injury to the colon barrier, including tight junction (TJ) and mucosal barriers, via overactivation of the Notch signalling pathway under increased OS in mice and intestinal organoids. Notably, PSMP@B (a) P exposure exacerbated damage to TJ and the mucosal barrier via the overproduction of reactive oxygen species (ROS), which could be related to the release of B (a) P from PSMP@B (a) P induced by the acidic environment of autophagosomes, which in turn exert synergistic toxic effects with PSMPs. Our study elucidates some of the potential molecular mechanisms by which B (a) P enhances PSMP-related intestinal toxicity, which provides a potential therapeutic approach for diseases caused by PSMP@B (a)P and PSMP pollution.

Kinetics of polystyrene nanoplastic deposition on SiO2 and Al2O3 surfaces: Ionic strength effects

Nanoplastic pollution is an emerging environmental threat to the critical zone. The transport of nanoplastic particles in subsurface environments can be determined mainly by soil minerals because they provide surfaces that interact with nanoplastic particles. However, the interactions between mineral surfaces and nanoplastics are poorly understood. In this study, the deposition kinetics of polystyrene-nanoplastic particles onto representative oxide surfaces SiO2 and Al2O3 at circumneutral pH were investigated using a quartz crystal microbalance, with variations in the ionic strength (0.1-100 mM) of the well-dispersed nanoplastic particles suspension. While polystyrene-nanoplastic particles deposited minimally on the SiO2 surface at an ionic strength of < 100 mM (∼10 ng/cm2), substantial deposition occurred at 100 mM (3.7 ± 0.4 μg/cm2). On the Al2O3 surface, a significant amount of polystyrene-nanoplastic particle was deposited from the lowest ionic strength (4.5 ± 0.8 μg/cm2). The deposition mass at 100 mM NaCl was two times higher (7.2 ± 0.2 μg/cm2) than on the SiO2 surface, while the deposition rates were similar between the two surfaces (10-15 Hz/min). Our results indicate that alumina most likely exerts a stronger influence than quartz on the transport of nanoplastic particles in soils and groundwater aquifers. The deposition kinetics strongly depends on the mineral surface and solution ionic strength, and these quantitative results can serve as validation data in developing transport modeling of nanoplastic in subsurface environments.

Aged microplastics change the toxicological mechanism of roxithromycin on Carassius auratus: Size-dependent interaction and potential long-term effects

Size effects of microplastics have received extensive attention for their influence on other pollutants and harm to organisms. In this study, we investigated the uptake, elimination, tissue distribution and potential toxicity mechanism of roxithromycin (ROX) in the presence of 0.5, 5 and 50 μm of aged microplastics (AMPs) in Carassius auratus. The results showed that AMPs promoted the ROX bioaccumulation of various tissues in a size-dependent manner. AMPs and ROX significantly induced superoxide dismutase and catalase activities of liver and gut, and inhibited acetylcholinesterase activities of brain. The coexistence of smaller AMPs exacerbated pathological abnormalities in liver, gill and brain induced by ROX, while larger AMPs caused more intestinal damage. Moreover, high-throughput 16S rRNA gene sequencing indicated that the abundance of Proteobacteria in 0.5 μm AMPs and ROX joint treatments and Firmicutes and Bacteroidota in 50 μm AMPs and ROX joint treatments were significantly raised (p < 0.05). Metabolomics revealed that AMPs and ROX had a size-dependent long-term effect on gut microbial metabolites, which was mainly related to galactose metabolism, amino acid metabolism and primary bile acid biosynthesis pathways after a 7-day elimination, respectively. These results provide important insights into the relationship between the size effect of AMPs and interaction mechanism of AMPs and coexisting pollutants on aquatic organisms.

Plastic particles in medicine: A systematic review of exposure and effects to human health

Single-use plastics (SUPs) have become an essential constituent of our daily life. It is being exploited in numerous pharmaceutical and healthcare applications. Despite their advantages and widespread use in the pharma and medical sectors, the potential clinical problems of plastics, especially the release of micro-nanoplastics (MNPs) and additives from medical plastics (e.g. bags, containers, and administrative sets) and sorption of drugs remain understudied. Certainly, the MNPs are multifaceted stressors that cause detrimental effects to the ecosystem and human health. The origin and persistence of MNPs in pharmaceutical products, their administration to humans, endurance and possible health implication, translocation, and excretion have not been reviewed in detail. The prime focus of this article is to conduct a systematic review on the leaching of MNPs and additives from pharmaceutical containers/administrative sets and their interaction with the pharmaceutical constituents. This review also explores the primary and secondary routes of MNPs entry from healthcare plastic products and their potential health hazards to humans. Furthermore, the fate of plastic waste generated in hospitals, their disposal, and associated MNPs release to the environment, along with preventive, and alternative measures are discussed herein.

Polystyrene nanoparticles: the mechanism of their genotoxicity in human peripheral blood mononuclear cells

Plastic nanoparticles are widely spread in the biosphere, but health risk associated with their effect on the human organism has not yet been assessed. The purpose of this study was to determine the genotoxic potential of non-functionalized polystyrene nanoparticles (PS-NPs) of different diameters of 29, 44, and 72 nm in human peripheral blood mononuclear cells (PBMCs) (in vitro). To select non-cytotoxic concentrations of tested PS-NPs, we analyzed metabolic activity of PBMCs incubated with these particles in concentrations ranging from 0.001 to 1000 µg/mL. Then, PS-NPs were used in concentrations from 0.0001 to 100 μg/mL and incubated with tested cells for 24 h. Physico-chemical properties of PS-NPs in media and suspension were analyzed using dynamic light scattering (DLS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and zeta potential. For the first time, we investigated the mechanism of genotoxic action of PS-NPs based on detection of single/double DNA strand-breaks and 8-oxo-2'-deoxyguanosine (8-oxodG) formation, as well as determination of oxidative modification of purines and pyrimidines and repair efficiency of DNA damage. Obtained results have shown that PS-NPs caused a decrease in PBMCs metabolic activity, increased single/double-strand break formation, oxidized purines and pyrimidines and increased 8oxodG levels. The resulting damage was completely repaired in the case of the largest PS-NPs. It was also found that extent of genotoxic changes in PBMCs depended on the size of tested particles and their ζ-potential value.

Consequences of nano and microplastic exposure in rodent models: the known and unknown

The ubiquitous nature of micro- (MP) and nanoplastics (NP) is a growing environmental concern. However, their potential impact on human health remains unknown. Research increasingly focused on using rodent models to understand the effects of exposure to individual plastic polymers. In vivo data showed critical exposure effects depending on particle size, polymer, shape, charge, concentration, and exposure routes. Those effects included local inflammation, oxidative stress, and metabolic disruption, leading to gastrointestinal toxicity, hepatotoxicity, reproduction disorders, and neurotoxic effects. This review distillates the current knowledge regarding rodent models exposed to MP and NP with different experimental designs assessing biodistribution, bioaccumulation, and biological responses. Rodents exposed to MP and NP showed particle accumulation in several tissues. Critical responses included local inflammation and oxidative stress, leading to microbiota dysbiosis, metabolic, hepatic, and reproductive disorders, and diseases exacerbation. Most studies used MP and NP commercially provided and doses higher than found in environmental exposure. Hence, standardized sampling techniques and improved characterization of environmental MP and NP are needed and may help in toxicity assessments of relevant particle mixtures, filling knowledge gaps in the literature.

Pulmonary toxicology assessment of polyethylene terephthalate nanoplastic particles in vitro

Nanoplastics are more likely to be suspended in air and pose a risk of respiratory exposure. However, the early health effects of low-dose nanoplastics on the respiratory system, which are expected to reflect the risk of atmospheric nanoplastics, need to be further evaluated. In this study, nanoparticles of polyethylene terephthalate, a representative plastic polymer in air, were prepared by a precipitation method. The toxicity impacts of nano-PET at environmental concentrations on the human lung carcinoma cell A549 cells were evaluated. Although the nano-PET was identified to enter the cells by confocal microscope observation and alkali-assisted thermal depolymerization coupled with LC-MS/MS analysis, the nano-PET exhibited low toxicity on mitochondrial membrane potential levels and cell apoptosis. At low concentrations of 0.10 and 0.98 μg/mL, the nano-PET had a slight promotion effect on cell viability, while an inhibitory effect on cell viability presented at higher nano-PET concentrations of 98.40 and 196.79 μg/mL. The cell survival rate at 98.4 and 196.79 μg/mL of nano-PET are lower than that of the control, and significant oxidative stress in cells caused by the nano-PET exposure at 49.2 μg/mL was observed. A decrease tendency of mitochondrial membrane potential with the increasing nano-PET exposure presents, which is consistent with the change of reactive oxygen species. Furthermore, nano-PET at ≦ 98.4 μg/mL could not increase the sum of apoptotic in the cells, but the late apoptotic cells increased with the increase of the exposure dose. The major mechanism of the toxic effect of nano-PET on cells may be the increase of reactive oxygen species caused by oxidative stress, which in turn induces a decrease in the mitochondrial membrane potential. This study provides information on the toxicity of nano-PET at environmental concentrations in human lung cells, which helps to enrich the risk cognition of nanoplastics in the respiratory system.

Effects of nano- and microplastics on kidney: Physicochemical properties, bioaccumulation, oxidative stress and immunoreaction

The potential toxicity of nanoplastics (NPs) and microplastics (MPs) has raised concerns. However, knowledge of the effects of NPs/MPs on the health of mammals is still limited. Here we investigated the alteration of the physicochemical properties of polystyrene NPs (PS-NPs: 50 nm) and MPs (PS-MPs: 300 nm, 600 nm, 4 μm) in the gastrointestinal tract. Moreover, we investigated the uptake and bioaccumulation and the toxic effects of these plastic particles in the kidneys of mice. The results revealed that their digestion promoted the aggregation of PS-NPs and PS-MPs and increased the Zeta-potential value. Both PS-NPs and PS-MPs bioaccumulated in the kidneys, and the aggregation of 600 nm PS-MPs exacerbated their biotoxicity. The PS-NPs and PS-MPs caused mice weight loss, increased their death rate, significantly alternated several biomarkers, and resulted in histological damage of the kidney. We also found that exposure to PS-NPs and PS-MPs induced oxidative stress and the development of inflammation. These findings provide new insights into the toxic effects of NPs and MPs on mice.

Mechanistic insights into primary biotransformation of diethyl phthalate in earthworm and significant SOD inhibitory effect of esterolytic products

Phthalic acid esters (PAEs) are used as plasticizer or modifier in artificially-manufactured products. Though the rapid biotransformation of phthalates in microbes and plants have been well documented, it is less studied yet in terrestrial animals, e.g. earthworm. In this study, the major biotransformation of diethyl phthalate (DEP) in Eisenia fetida was illustrated using in vitro incubation of earthworm crude enzymes. DEP could be substantially biotransformed into phthalate monoester (MEP) and a small amount of phthalic acid (PA) through esterolysis, which was verified to be driven by endogenous carboxylesterase. Despite the inferior contribution, the oxidation of DEP might also occur under the initiated electron transfer by NADPH coenzyme. The dominant metabolite MEP showed a higher inhibition of superoxide dismutase (SOD) activity than DEP with EC₅₀ of 0.0082 ± 0.0016 mmol/L, so the higher ecological risks of MEP would be marked. The inhibition effect of PA was validated to be even stronger than MEP though it was slightly generated. The direct binding interaction with SOD was proved to be an important molecular event for regulation of SOD activity. Besides the static quenching mechanism, the caused conformational changes including despiralization of α-helix and spatial reorientation of tryptophan were spectrally believed to affect binding and underlie inhibition efficiency of SOD activity.

Microplastics in terrestrial ecosystems: Moving beyond the state of the art to minimize the risk of ecological surprise

Microplastic (plastic particles measuring <5mm) pollution is ubiquitous. Unlike in other well-studied ecosystems, for example, marine and freshwater environments, microplastics in terrestrial systems are relatively understudied. Their potential impacts on terrestrial environments, in particular the risk of causing ecological surprise, must be better understood and quantified. Ecological surprise occurs when ecosystem behavior deviates radically from expectations and generally has negative consequences for ecosystem services. The properties and behavior of microplastics within terrestrial environments may increase their likelihood of causing ecological surprises as they (a) are highly persistent global pollutants that will last for centuries, (b) can interact with the abiotic environment in a complex manner, (c) can impact terrestrial organisms directly or indirectly and (d) interact with other contaminants and can facilitate their transport. Here, we compiled findings of previous research on microplastics in terrestrial environments. We systematically focused on studies addressing different facets of microplastics related to their distribution, dispersion, impact on soil characteristics and functions, levels of biological organization of tested terrestrial biota (single species vs. assemblages), scale of experimental study and corresponding ecotoxicological effects. Our systematic assessment of previous microplastic research revealed that most studies have been conducted on single species under laboratory conditions with short-term exposures; few studies were conducted under more realistic long-term field conditions and/or with multi-species assemblages. Studies targeting multi-species assemblages primarily considered soil bacterial communities and showed that microplastics can alter essential nutrient cycling functions. More ecologically meaningful studies of terrestrial microplastics encompassing multi-species assemblages, critical ecological processes (e.g., biogeochemical cycles and pollination) and interactions with other anthropogenic stressors must be conducted. Addressing these knowledge gaps will provide a better understanding of microplastics as emerging global stressors and should lower the risk of ecological surprise in terrestrial ecosystems.

Key mechanisms of micro- and nanoplastic (MNP) toxicity across taxonomic groups

Micro- and nanoplastics (MNPs) are ubiquitous in aquatic and terrestrial environments, and detrimental biological effects have been observed on a variety of organisms, from bacteria and alga to plants and animals. A fast-growing number of toxicological studies report diverse responses and wide species-dependent sensitivity upon MNP exposure. While studies are dominated by in vivo animal tests, our understanding of cellular toxicity and the corresponding toxicity mechanisms is still limited. This challenges the proper assessment of environmental hazards and health risks of MNPs. In this review, we gathered and analyzed the up-to-date studies on humans, animals, plants, alga, and bacteria, and identified the similarities and differences in key toxicity mechanisms of MNPs across different taxonomic groups. Particularly, human cell-based studies at the cellular level provide fundamental and valuable information on the key toxicity mechanisms, which are essential to answer the question of whether and how MNPs pose health threats. In general, toxicity mechanisms of MNPs depend on their size, surface characteristics, polymer type, as well as cell type. Plausible toxicity mechanisms mainly include membrane disruption, extracellular polymeric substance disruption, reactive oxygen species generation, DNA damage, cell pore blockage, lysosome destabilization, and mitochondrial depolarization. A deeper understanding of these key mechanisms in different taxonomic groups can also improve both in vivo and in vitro models useful for predictive impact assessments of plastic pollution on the environment and human health.

Resolving the effects of environmental micro- and nanoplastics exposure in biota: A knowledge gap analysis

The pervasive spread of microplastics (MPs) and nanoplastics (NPs) has raised significant concerns on their toxicity in both aquatic and terrestrial environments. These polymer-based materials have implications for plants, wildlife and human health, threatening food chain integrity and ultimate ecosystem resilience. An extensive - and growing - body of literature is available on MP- and NP-associated effects, including in a number of aquatic biota, with as yet limited reports in terrestrial environments. Effects range from no detectable, or very low level, biological effects to more severe outcomes such as (but not limited to) increased mortality rates, altered immune and inflammatory responses, oxidative stress, genetic damage and dysmetabolic changes. A well-established exposure route to MPs and NPs involves ingestion with subsequent incorporation into tissues. MP and NP exposures have also been found to lead to genetic damage, including effects related to mitotic anomalies, or to transmissible damage from sperm cells to their offspring, especially in echinoderms. Effects on the proteome, transcriptome and metabolome warrant ad hoc investigations as these integrated "omics" workflows could provide greater insight into molecular pathways of effect. Given their different physical structures, chemical identity and presumably different modes of action, exposure to different types of MPs and NPs may result in different biological effects in biota, thus comparative investigations of different MPs and NPs are required to ascertain the respective effects. Furthermore, research on MP and NP should also consider their ability to act as vectors for other toxicants, and possible outcomes of exposure may even include effects at the community level, thus requiring investigations in mesocosm models.

Toxic effects on bioaccumulation, hematological parameters, oxidative stress, immune responses and neurotoxicity in fish exposed to microplastics: A review

Exposure to microplastics (MP) in aquatic environment leads to bioaccumulation in fish, with MP size being a major factor in determining the accumulation profile. MPs absorbed into the fish body enter the circulatory system and affect hematological properties, changing the blood physiology. MPs also induce an imbalance in reactive oxygen species (ROS) production and antioxidant capacity, causing oxidative damage. In addition, MPs impact immune responses due to physical and chemical toxicity, and cause neurotoxicity, altering AchE activity. Here, the toxic effects of MPs in fish through various indicators were examined, including bioaccumulation, hematological parameters, antioxidant responses, immune responses, and neurotoxicity in relation to MP exposure, facilitating the identification of biomarkers of MP toxicity following exposure of fish.

Algal density affects the influences of polyethylene microplastics on the freshwater rotifer Brachionus calyciflorus

Most previous researches focused on the toxicity of polystyrene microplastics (MPs) to marine organisms, but less on polyethylene MPs and freshwater zooplanktons. The present study aims to elucidate the toxicity of polyethylene (PE) MPs (diameter = 10-22 μm) to the typical freshwater rotifer Brachionus calyciflorus. Firstly, fluorescent microscope observation showed that rotifers could ingest PE MPs and accumulate them in their digestive tracts. Life-table experiments revealed that exposure to 0.5 × 10³, 2.5 × 10³, and 1.25 × 10⁴ particles/mL PE MPs significantly reduced net reproductive rate and intrinsic rate of pollution increase of rotifers under algal densities (Scenedesmus obliquus) of 0.1 × 10⁶, and 0.5 × 10⁶ cells/mL, but no significant effects were observed under 2.5 × 10⁶ cells/mL algal density. These results showed that PE MPs suppressed the reproduction of rotifer and this negative effect could be alleviated by increasing food supply. The swimming linear speed of rotifers significantly decreased with increasing MP concentrations. The activities of superoxide dismutase and Na⁺-K⁺-ATPase significantly decreased in treatments with high concentration of PE MPs under 0.1 × 10⁶ cells/mL algal density, but did not change significantly in MP treatments under 0.5 × 10⁶ and 2.5 × 10⁶ cells/mL, compared to the control. Glutathione peroxidase activity significantly increased in treatments with 1.25 × 10⁴ particles/mL and 2.5 × 10³ particles/mL under 0.1 × 10⁶ and 0.5 × 10⁶ cells/mL algal density, respectively, but did not change significantly in all MP treatments under 2.5 × 10⁶ cells/mL. Exposure to PE MPs might lower the gathering capacity of algae, induce oxidative stress, trigger cell membrane damages and disturb energy metabolism in rotifers, which can explain the PE MPs toxicity to rotifer reproduction.

Oxidative Properties of Polystyrene Nanoparticles with Different Diameters in Human Peripheral Blood Mononuclear Cells (In Vitro Study)

With the ongoing commercialization, human exposure to plastic nanoparticles will dramatically increase, and evaluation of their potential toxicity is essential. There is an ongoing discussion on the human health effects induced by plastic particles. For this reason, in our work, we assessed the effect of polystyrene nanoparticles (PS-NPs) of various diameters (29, 44 and 72 nm) on selected parameters of oxidative stress and the viability of human peripheral blood mononuclear cells (PBMCs) in the in vitro system. Cells were incubated with PS-NPs for 24 h in the concentration range of 0.001 to 100 µg/mL and then labeled: formation of reactive oxygen species (ROS) (including hydroxyl radical), protein and lipid oxidation and cell viability. We showed that PS-NPs disturbed the redox balance in PBMCs. They increased ROS levels and induced lipid and protein oxidation, and, finally, the tested nanoparticles induced a decrease in PBMCs viability. The earliest changes in the PBMCs were observed in cells incubated with the smallest PS-NPs, at a concentration of 0.01 μg/mL. A comparison of the action of the studied nanoparticles showed that PS-NPs (29 nm) exhibited a stronger oxidative potential in PBMCs. We concluded that the toxicity and oxidative properties of the PS-NPs examined depended to significant degree on their diameter.

Response of G protein-coupled receptor CED-1 in germline to polystyrene nanoparticles in Caenorhabditis elegans

The deposition of a certain amount of nanopolystyrene (NPS) can be observed in the gonad of Caenorhabditis elegans. However, we still know little about the response of germline towards NPS exposure. In the germline of C. elegans, NPS (1-1000 μg L^-1) increased the expression levels of two G protein-coupled receptors (GPCRs), namely PAQR-2 and CED-1. Moreover, susceptibility to NPS toxicity was observed in ced-1(RNAi) worms, which suggested that the protective response of germline was mediated by GPCR CED-1. In the germline, five proteins (CED-10, VPS-34, SNX-1, RAB-7, and RAB-14) functioned as downstream targets of GPCR CED-1 in controlling NPS toxicity. Furthermore, these five targets in the germline regulated NPS toxicity by affecting the activities of p38 MAPK and insulin signaling pathways in intestinal cells. Therefore, we raised a GPCR CED-1-mediated signaling cascade in the germline in response to NPS exposure, which is helpful for understanding the molecular basis of the germline in response to NPS exposure.

Different effects of nano- and microplastics on oxidative status and gut microbiota in the marine medaka Oryzias melastigma

Plastic is regarded as a major environmental concern. In particular, nanoplastics and microplastics (NMPs) are attracting global attention due to their potential impact on aquatic organisms. Here, we examined the effects of NMPs (50 nm polystyrene microbead nanoplastics [NPs] and 45 µm microplastics [MPs]) on oxidative status and gut microbiota in the marine medaka Oryzias melastigma. The NP-exposed group exhibited stronger oxidative stress with higher activation levels of antioxidants compared to the MP-exposed group. However, the MP-exposed group demonstrated induction of intestinal damage (e.g., increased mucus ratio) with further alterations of gut microbiota, compared to the NP-exposed group. In particular, MPs caused more significant alterations of microbiota composition at both phylum and genus levels. Thus, in this study we show distinct toxicity pathways of NPs and MPs, an oxidative stress-mediated pathway (e.g., antioxidants) induced by NP exposure and dysbiosis of gut microbiota in association with immune dysfunction induced by MP exposure. Our results are helpful for expanding our knowledge about the impacts of NMPs as potentially harmful substances in the aquatic environment.

Micro- and nanoplastic induced cellular toxicity in mammals: A review

Plastic based products are ubiquitous due to their tremendous utility in our daily lives. However, the limited biodegradable nature of plastics has recently raised pollution concerns globally, especially micro- and nanoplastics. These anthropogenic pollutants are either manufactured specifically in the small size range for various commercial applications or formed due to fragmentation of macro plastics in the environment. Micro- and nanoplastics are currently widespread in the oceans, freshwater bodies, land and even present in our food. The biological effects of micro- and nanoplastics on aquatic organisms are well documented but their impacts on mammalian system have not been rigorously investigated. This review discusses the potential routes of exposure to micro- and nanoplastics, biological effects of these particles in mammalian cells, factors influencing toxicity, and the probable mechanisms of cytotoxicity. In general, small size, positive charge, high dose, and presence of toxic additives or pollutants in the micro/nanoplastics appear to induce cellular toxicity through oxidative stress, membrane damage, immune response and genotoxicity. Understanding the cellular fate and toxicity of these materials may help extrapolate risks to mammals.

A critical viewpoint on current issues, limitations, and future research needs on micro- and nanoplastic studies: From the detection to the toxicological assessment

Increasing scientific attention on the presence of micro- and nanoplastics (MNPs) in the environments and their potential toxic effects on humans and the ecosystems is evident. Accordingly, the number of publications on this topic has increased substantially from only 5 in 2010 to more than 850 in 2019. Thus, this critical review aimed at providing state-of-the-art information on the existing methods for characterization and detection of MNPs in various matrices, as well as the reported toxic effects of MNPs in both in vivo and in vitro systems, anticipating challenges and providing future needs to improve the current scientific knowledge. We performed a systematic search of recent literature on available methodologies for the characterization/detection of MNPs in different samples, and the summary of such protocols is provided. Also, the existing procedures for in vitro and in vivo toxicity evaluation of MNPs were critically described. The results of our search revealed that quite a great deal of effort had been made to detect, characterize, and quantify the fate and effect of MNPs. However, we are still far from a complete understanding of behaviors of MNPs in the environments and biological systems. Thus, there is a need to advance the existing protocols to improve data accuracy. Besides, more studies that focus on uptake kinetics, accumulation, and biodistribution of MNPs in biological systems are required.