Impact of microplastics and nanoplastics on liver health:Current understanding and future research directions

With continuous population and economic growth in the 21st century,plastic pollution is a major global issue.However,the health concern of microplastics/nanoplastics(MPs/NPs)decomposed from plastic wastes has drawn public attention only in the recent decade.This article summarizes recent works dedicated to understanding the impact of MPs/NPs on the liver-the largest digestive organ,which is one of the primary routes that MPs/NPs enter human bodies.The interrelated mechanisms including oxidative stress,hepatocyte energy re-distribution,cell death and autophagy,as well as immune responses and inflammation,were also featured.In addition,the disturbance of microbiome and gut-liver axis,and the association with clinical diseases such as metabolic dysfunction-associated fatty liver disease,steatohepatitis,liver fibrosis,and cirrhosis were briefly discussed.Finally,we discussed potential directions in regard to this trending topic,highlighted current challenges in research,and proposed possible solutions.

Dietary exposure to sulfamethazine,nanoplastics and their binary mixture disrupts the spermatogenesis of marine medaka(Oryzias melastigma)

In the coastal environment,the co-occurrence of antibiotic and nanoplastic pollution is common.Investigating their individual and combined toxicity to marine organisms is of great necessity.In the present study,the reproductive toxicity of sulfamethazine(SMZ)and nanoplastics(polystyrene,PS)via the dietary route on the spermatogenesis of marine medaka(Oryzias melastigma)was examined.After 30 d of dietary exposure,SMZ alone decreased the gonadosomatic index(GSI)value(~35%)and the proportion of undifferentiated type A spermatogonia(A_(und))(~40%),probably by disrupting the testicular sex hormone production,the spermatogenesis-related growth factor network and the balance of apoptosis.Individual exposure to PS did not affect the GSI value or the proportions of germ cells at different developmental stages,but dysregulated the expression of several spermatogenesis-related genes.Interestingly,the presence of PS alleviated the decreased GSI value caused by SMZ.This alleviation effect was achieved by enhancing the spermatogonia differentiation instead of reversing the suppressed self-renewal of A_(und),suggesting that the mixture of PS and SMZ could cause reproductive effects in a different way.These findings expand our knowledge of threats of ubiquitous antibiotic and nanoplastic pollution to fish reproduction and population.

Evidence on Invasion of Blood,Adipose Tissues,Nervous System and Reproductive System of Mice After a Single Oral Exposure:Nanoplastics versus Microplastics

Objective This study was designed to provide the evidences on the toxicokinetics of microplastics(MPs)and nanoplastics(NPs)in the bodies of mammals.Methods 100 nm,3μm,and 10μm fluorescent polystyrene(PS)beads were administered to mice once by gavage at a dose of 200 mg/kg body weight.The levels and change of fluorescence intensity in samples of blood,subcutaneous fat,perirenal fat,peritesticular fat,cerebrum,cerebellum,testis,and epididymis were measured at 0.5,1,2,and 4 h after administration using an IVIS Spectrum small-animal imaging system.Histological examination,confocal laser scanning,and transmission electron microscope were performed to corroborate the findings.Results After confirming fluorescent dye leaching and impact of pH value,increased levels of fluorescence intensity in blood,all adipose tissues examined,cerebrum,cerebellum,and testis were measured in the 100 nm group,but not in the 3 and 10μm groups except in the cerebellum and testis at 4 h for the 3μm PS beads.The presence of PS beads was further corroborated.Conclusion After a single oral exposure,NPs are absorbed rapidly in the blood,accumulate in adipose tissues,and penetrate the blood-brain/testis barriers.As expected,the toxicokinetics of MPs is significantly size-dependent in mammals.

Polystyrene nanoplastics aggravated ecotoxicological effects of polychlorinated biphenyls in on zebrafish(Danio rerio)embryos

In view of the accumulation of nanoplastics(NPs)in the food chain of environment and animals,and the good adsorption properties of nano-plastics to toxic substances,it is necessary to explore the influence of NPs in living organisms.In this study,single and joint toxicological effects of polystyrene nanoplastics(PS-NPs,size 80 nm)and polychlorinated biphenyls(PCBs),were explored in freshwater aquatic animal model zebrafish(Danio rerio).Our study found that exposure to single PS-NPs induced mild acute toxicity,albeit the combined exposure of PS-NPs and polychlorinated biphenyls aggravated the toxicity of PCBs in a dose-dependent manner.Results from gene expression profiling showed that NPs exposure could activate detoxification process,resulting in a slight up-regulation of antioxidant genes(sod1,gstp1),bone development genes(bmp2,bmp4)and cardiac gene(tbx20);while PCBs suppressed the detoxification through down-regulation of these genes,and the addition of NPs will exacerbate the impact of PCBs on gene suppression.Importantly,the results of in vivo purification experiments found that NPs showed prolonged retention in liver,intestine and gills of zebrafish and they might have crossed biological barrier and accumulate in lipid-rich tissues and excretion does not appear as the significant pathway for their elimination.In conclusion,the toxic effects of polychlorinated biphenyls on chorionic protected embryos were not significant as zebrafish chorion plays an important role in resisting the invasion of pollutants;PCBs can seriously damage the bone and heart development of zebrafish,while the presence of NPs significantly enhanced the toxicity of PCBs in zebrafish,which is an alarming concern for growing NPs levels and ecological safety in aquatic environment.

PREDICTION OF THE VISCOELASTIC PROPERTIES OF THE EQUIVALENT PARTICLE FOR THE INTERCALATED MULTI-LAYER STACK OF NANOPLASTICS

The aim of this paper is to apply the asymptotic homogenization method to determining analytically and numerically the transversely isotropic viscoelastic relaxation moduli of the equivalent particle for the intercalated multi-layer stack of intercalated type nanoplastics. A two-phase multilayered material containing n layers is considered. The matrix is assumed to be an isotropic viscoelastic standard linear body and the reinforcement is assumed to be an isotropic elastic body. Final explicit analytical formulae for the effective elastic moduli of the multilay- ered material are derived first; and then the correspondence principle is employed to obtain the homogenized relaxation moduli of the equivalent intercalated particle. A numerical example is given. Final explicit analytical formulae in the time domain derived here make it convenient to estimate the influence of all the particle parameters of micro-structural details on the effective properties of the equivalent intercalated particle. The results of this paper can also be applied to multi-layer composites.

Enhanced hepatic metabolic perturbation of polystyrene nanoplastics by UV irradiation-induced hydroxyl radical generation

The environmental behavior of and risks associated with nanoplastics(NPs)have attracted considerable attention.However,compared to pristine NPs,environmental factors such as ultraviolet(UV)irradiation that lead to changes in the toxicity of NPs have rarely been studied.We evaluated the changes in morphology and physicochemical properties of polystyrene(PS)NPs before and after UV irradiation,and compared their hepatotoxicity in mice.The results showed that UV irradiation caused particle size reduction and increased the carbonyl index(CI)and negative charge on the particle surface.UV-aged PS NPs(aPS NPs)could induce the generation of hydroxyl radicals(·OH),but also further promoted the generation of·OH in the Fenton reaction system.Hepatic pathological damage was more severe in mice exposed to aPS NPs,accompanied by a large number of vacuoles and hepatocyte balloon-like changes and more marked perturbations in blood glucose and serum lipoprotein,alanine aminotransferase and aspartate aminotransferase levels.In addition,exposure to PS NPs and aPS NPs,especially aPS NPs,triggered oxidative stress and significantly damaged the antioxidant capacity of mice liver.Compared with PS NPs,exposure to aPS NPs increased the number of altered metabolites in hepatic and corresponding metabolic pathways,especially glutathione metabolism.Our research suggests that UV irradiation can disrupt the redox balance in organisms by promoting the production of·OH,enhancing PS NPs-induced liver damage and metabolic disorders.This study will help us understand the health risks of NPs and to avoid underestimation of the risks of NPs in nature.

Polystyrene nanoplastics induce glycolipid metabolism disorder via NF-κB and MAPK signaling pathway in mice

Nanoplastics-induced developmental and reproductive toxicity,neurotoxicity and immunotoxicity are a focus of widespread attention.However,the effects of nanoplastics(NPs)on glycolipid metabolism and the precise underlying mechanisms are unclear at present.Here,we showed that oral administration of polystyrene nanoparticles(PS-NPs)disrupts glycolipid metabolism,with reactive oxygen species(ROS)identified as a potential key signaling molecule.After PS-NPs treatment,excessive production of ROS induced the infammatory response and activated the antioxidant pathway through nuclear factor-erythroid factor 2-related factor 2.The activation of nuclear factor-κB(NFκB)signaling pathway induced the phosphorylation of the mitogen-activated protein kinases(MAPK)signaling pathway,which induced the activation of extracellular regulated kinases(ERK)and p38.Constitutive activation of the MAPK signaling proteins induced high continued phosphorylation of insulin receptor substrate-1,in turn,leading to decreased protein kinase B(Akt)activity,which weakened the sensitivity of liver cells to insulin signals and induced insulin resistance.In parallel,phosphorylation of Akt led to loss of control of Fo XO1,a key gene of gluconeogenesis,activating transcription of glucose-6-phosphatase(G6PC)and phosphoenolpyruvate carboxykinase(PEPCK)in a manner dependent on PGC1α.Moreover,the activated ERK promoted lipid accumulation through ERK-PPARγcascades.Therefore,sterol regulatory element-binding protein-1 and levels of its downstream lipogenic enzymes,ACC-1,were up-regulated.Upon treatment with the antioxidant resveratrol,PS-NPs-induced glucose and lipid metabolic disorders were improved by inhibiting ROS-induced activation of NFκB and MAPK signaling pathway in mice.Based on above,PS-NPs exposure disrupts glycolipid metabolism in mice,with ROS identified as a potential key signaling molecule.

The short and long-term effect of polystyrene nanoplastics on nitrifying sludge at high nitrite concentrations

The effect of nanoplastics(NPs)on nitrite oxidation bacteria(NOB)community in treating high-strength wastewater remains unclear,which seriously affects the stability of nitrogen removal process.In this study,highly active nitrifying sludge was enriched and exposed to 50nm polystyrene NPs(PS-NPs)for short-term(1,100,500,and 1000 mg/L,1.5 hr)and long-term(1,10,100 mg/L,40 days)at high nitrite concentration.In contrast to previous studies,our results showed that the exposures to PS-NPs had little effect on nitrifying performances.After long-term exposure,the protein/polysaccharide ratios in extracellular polymeric substances(EPS)were positively correlated with PS-NPs concentrations(0.78–0.99).The produced reactive oxygen species(ROS)were gradually removed,and PS-NPs higher than 10 mg/L caused damage to membrane integrity.Long-term exposure for 40 days increased the community diversity and caused significant differences between the control and exposed communities.The control group were dominated by Nitrobacter and Exiguobacterium,while the exposure group was dominated by Bacillus,Mycobacterium,and Nitrospira.A noticeable shift in the NOB community from Nitrobacter(26.5%to 3.4%)to Nitrospira(1.61%to 14.27%)was observed.A KEGG analysis indicated a decrease in cell growth and death,cell motility and energy metabolism.It appeared that NOB could adapt to PS-NPs stress through enhanced secretion and removal of oxidative damage.Overall,this study provided new insights into the response mechanism of NOB to PS-NPs exposure.

Fasn involved in the nephrotoxicity induced by polystyrene nanoplastics and the intervention of melatonin through intestinal microbiota-mediated lipid metabolism disorder

Nanoplastics(NPs)can accumulate in the kidney and cause kidney injury,but the multi-organ interaction mechanism and preventive measures of kidney injury are still unclear.In this study,in vivo(60μg/day,42 days)and in vitro(0.4μg/μL,24 h)exposure models of polystyrene nanoplastics(PS-NPs,80 nm)in mice and human kidney cortex proximal tubule epithelial cells(HK-2 cells)were established,respectively.Our study revealed that PS-NPs caused obvious pathological changes and impaired renal function in mice,which were related to lipid metabolism disorders mediated by intestinal flora.Desulfovibrionales-fatty acid synthase(Fasn)-docosahexaenoic acid(DHA)pathway may be one of the mechanisms of kidney injury in mice.Importantly,we also found that melatonin attenuates PS-NPs-induced nephrotoxicity by modulating lipid metabolism disorders(represented by DHA)and affects Fasn expression.In conclusion,our study revealed the important role of intestinal flora-mediated lipid metabolism in PS-NPs-induced nephrotoxicity and preliminarily provided potential key gene targets and effective preventive measures for PS-NPs-induced nephrotoxicity.

Nrf2-mediated ferroptosis of spermatogenic cells involved in male reproductive toxicity induced by polystyrene nanoplastics in mice

Microplastics(MPs)and nanoplastics(NPs)have become hazardous materials due to the massive amount of plastic waste and disposable masks,but their specific health effects remain uncertain.In this study,fluorescence-labeled polystyrene NPs(PS-NPs)were injected into the circulatory systems of mice to determine the distribution and potential toxic effects of NPs in vivo.Interestingly,whole-body imaging found that PS-NPs accumulated in the testes of mice.Therefore,the toxic effects of PS-NPs on the reproduction systems and the spermatocytes cell line of male mice,and their mechanisms,were investigated.After oral exposure to PS-NPs,their spermatogenesis was affected and the spermatogenic cells were damaged.The spermatocyte cell line GC-2 was exposed to PS-NPs and analyzed using RNA sequencing(RNA-seq)to determine the toxic mechanisms;a ferroptosis pathway was found after PS-NP exposure.The phenomena and indicators of ferroptosis were then determined and verified by ferroptosis inhibitor ferrostatin-1(Fer-1),and it was also found that nuclear factor erythroid 2-related factor 2(Nrf2)played an important role in spermatogenic cell ferroptosis induced by PS-NPs.Finally,it was confirmed in vivo that this mechanism of Nrf2 played a protective role in PS-NPs-induced male reproductive toxicity.This study demonstrated that PS-NPs induce male reproductive dysfunction in mice by causing spermatogenic cell ferroptosis dependent on Nrf2.

Nanoplastics promote the dissemination of antibiotic resistance genes and diversify their bacterial hosts in soil

The wide application of plastics has led to the ubiquitous presence of nanoplastics and microplastics in terrestrial environments.However,few studies have focused on the mechanism underlying the effects of plastic particles on soil microbiomes and resistomes,especially the differences between nanoplastics and microplastics.This study investigated the microbiome and resistome in soil exposed to polystyrene microplastics(mPS)or nanoplastics(nPS)through 16S rRNA and shotgun metagenomic sequencing.Distinct microbial communities were observed between mPS and nPS exposure groups,and nPS exposure significantly changed the bacterial composition even at the lowest amended rate(0.01%,w/w).The abundance of antibiotic resistance genes(ARGs)in nPS exposure(1%)was 0.26 copies per cell,significantly higher than that in control(0.21 copies per cell)and mPS exposure groups(0.21 copies per cell).It was observed that nanoplastics,bacterial community,and mobile genetic elements(MGEs)directly affected the ARG abundance in nPS exposure groups,while in mPS exposure groups,only MGEs directly induced the change of ARGs.Streptomyces was the predominant host for multidrug in the control and mPS exposure,whereas the primary host was changed to Bacillus in nPS exposure.Additionally,exposure to nPS induced several bacterial hosts to exhibit possible multi-antibiotic resistance characteristics.Our results indicated that the effects of plastic particles on the soil microbial community were size-dependent,and nano-sized plastic particles exhibited more substantial impacts.Both microplastics and nanoplastics promoted ARG transfer and diversified their bacterial hosts.These findings bear implications for the regulation of plastic waste and ARGs.

Stress response to nanoplastics with different charges in Brassica napus L.during seed germination and seedling growth stages

Nanoplastic pollution has become a significant problem in farmland systems worldwide.However,research on the effects of nanoplastics(NPs)with different charges on field crops is still limited.In our study,NPs with different charges,including unmodified polystyrene nanoplastics(PS),positively charged polystyrene nanoplastics(PS-NH_(2)),and negatively charged polystyrene nanoplastics(PSSO3H),were investigated for their impacts on seed germination and seedling growth of rape.The results showed that seed water uptake(after 12 h),seed germination,seed vigour,and relative root elongation were all significantly reduced under exposure to NPs(200 mg/L).Similarly,remarkable decreases in plant biomass(root weight,shoot weight),growth(root length,plant height),photosynthesis ability(chlorophyll a,chlorophyll b,carotenoids),essential nutrient uptake(Fe,Mn,Zn,Cu),and plant quality(soluble protein,soluble sugar,crude fibre content)of rape seedlings were also observed after exposure to NPs.Among the three kinds of NPs,PS-NH_(2)showed stronger effects.Moreover,superoxide dismutase,peroxidase,and catalase activities of rape seedlings were changed,and the content of malondialdehyde was significantly increased under exposure to NPs.Furthermore,positively charged PS-NH_(2)showed stronger effects on the phenotype,physiology,biochemistry,nutrient uptake,and plant quality of rape.Notably,a comprehensive toxicity evaluation revealed that PS-NH_(2)had the strongest toxicity to rape.The present study provides important implications for the interaction and risk assessment of NPs and crops in soil-plant systems.

Melatonin and probiotics ameliorate nanoplastics-induced hematopoietic injury by modulating the gut microbiotametabolism

Plastic pollution has become a non-negligible global pollution problem.Nanoplastics(NP)can reach the bone marrow with blood circulation and develop hematotoxicity,but potential mechanisms and prevention strategies are lacking.Here,we report the biological distribution of NP particles in the bone marrow of mice and hematopoietic toxicity after exposure to 60μg of 80 nm NP for 42 days.NP exposure inhibited the capability of bone marrow hematopoietic stem cells to renew and differentiate.Notably,probiotics and melatonin supplementation significantly ameliorated NP-induced hematopoietic damage,and the former was superior to the latter.And interestingly,melatonin and probiotic interventions may involve different microbes and metabolites.After melatonin intervention,creatine showed a stronger correlation with NP-induced gut microbiota disorders.In contrast,probiotic intervention reversed the levels of more gut microbes and plasma metabolites.Of these,threonine,malonylcarnitine,and 3-hydroxybutyric acid might be potential performers in the regulation of hematopoietic toxicity by gut microbes,as they had a more significant relationship with the identified microbes.In conclusion,supplementation with melatonin or probiotics may be two candidates to prevent hematopoietic toxicity attributable to NP exposure.Also,the multi-omics results may lay the foundation for future investigations into in-depth mechanisms.

Investigating Microplastics and Nanoplastics Released from a Rubber Band Used for Orthodontic Treatment with Improved Raman Imaging Algorithms

Most teenagers experience orthodontic treatment,but we do not know the possible adverse effect of the released microplastics and nanoplastics that are recently categorized as emerging contaminants.Herein,we test the rubber band that has been employed to improve the biting of teeth during the orthodontic process to confirm the release of microplastics and nanoplastics.We improve the characterization of microplastics and nanoplastics by(i)Raman imaging,to extract and map the signal from the scanning spectrum matrix or the hyperspectral matrix and to enhance the signal-to-noise ratio statistically.To effectively extract the signal,(ii)chemometrics such as principal component analysis(PCA)are explored to convert the hyperspectral matrix to an image with an increased certainty.The nonsupervised PCA is intentionally corrected,via(iii)the algebra-based algorithm,to further increase the certainty to image the microplastics and nanoplastics.Once the signal is weak,(iv)an additional algorithm of image reconstruction via deconvolution is developed to average the background noise and smooth the image.By doing so,we estimate that millions of microplastics and nanoplastics are released daily in potential from a rubber band applied in a teenager's mouth,which might be a big concern.Overall,our approach provides a suitable option to characterize the microplastics and nanoplastics from a complex background.

Data quality assessment for studies investigating microplastics and nanoplastics in food products: Are current data reliable?

Data on the occurrence of microplastics and nanoplastics(MP/NPs)in foods have been used to assess the human health risk caused by the consumption of MP/NPs.The reliability of the data,however,remains unclear because of the lack of international standards for the analysis of MP/NPs in foods.Therefore,the data quality needs to be assessed for accurate health risk assessment.This study developed 10 criteria applicable to the quality assessment of data on MP/NPs in foods.Accordingly,the reliability of 71 data records(69 of them only focused on MPs)was assessed by assigning a score of 2(reliable without restrictions),1(reliable but with restrictions),or 0(unreliable)on each criterion.The results showed that only three data records scored 2 or 1 on all criteria,and six data records scored 0 on as many as six criteria.A total of 58 data records did not include information on positive controls,and 12 data records did not conduct the polymer identification,which could result in the overestimation or underestimation of MP/NPs.Our results also indicated that the data quality of unprocessed foods was more reliable than that of processed foods.Furthermore,we proposed a quality assurance and quality control protocol to investigate MP/NPs in foods.Notably,the characteristics of MP/NPs used in toxicological studies and those existing in foods showed a remarkable discrepancy,causing the uncertainty of health risk assessment.Therefore,both the estimated exposure of MP/NPs and the claimed potential health risks should be treated with caution.

Recent progress and future directions of the research on nanoplastic-induced neurotoxicity

Many types of plastic products,including polystyrene,have long been used in commercial and industrial applications.Microplastics and nanoplastics,plastic particles derived from these plastic products,are emerging as environmental pollutants that can pose health risks to a wide variety of living organisms,including humans.However,it is not well understood how microplastics and nanoplastics affect cellular functions and induce stress responses.Humans can be exposed to polystyrene-microplastics and polystyrene-nanoplastics through ingestion,inhalation,or skin contact.Most ingested plastics are excreted from the body,but inhaled plastics may accumulate in the lungs and can even reach the brain via the nose-to-brain route.Small-sized polystyrene-nanoplastics can enter cells by endocytosis,accumulate in the cytoplasm,and cause various cellular stresses,such as inflammation with increased pro-inflammatory cytokine production,oxidative stress with generation of reactive oxygen species,and mitochondrial dysfunction.They induce autophagy activation and autophagosome formation,but autophagic flux may be impaired due to lysosomal dysfunction.Unless permanently exposed to polystyrene-nanoplastics,they can be removed from cells by exocytosis and subsequently restore cellular function.However,neurons are very susceptible to this type of stress,thus even acute exposure can lead to neurodegeneration without recovery.This review focuses specifically on recent advances in research on polystyrene-nanoplastic-induced cytotoxicity and neurotoxicity.Furthermore,in this review,based on mechanistic studies of polystyrene-nanoplastics at the cellular level other than neurons,future directions for overcoming the negative effects of polystyrene-nanoplastics on neurons were suggested.

The Uptake and Distribution Evidence of Nano-and Microplastics in vivo after a Single High Dose of Oral Exposure

Objective Tissue uptake and distribution of nano-/microplastics was studied at a single high dose by gavage in vivo.Methods Fluorescent microspheres(100 nm,3μm,and 10μm)were given once at a dose of 200 mg/(kg∙body weight).The fluorescence intensity(FI)in observed organs was measured using the IVIS Spectrum at 0.5,1,2,and 4 h after administration.Histopathology was performed to corroborate these findings.Results In the 100 nm group,the FI of the stomach and small intestine were highest at 0.5 h,and the FI of the large intestine,excrement,lung,kidney,liver,and skeletal muscles were highest at 4 h compared with the control group(P<0.05).In the 3μm group,the FI only increased in the lung at 2 h(P<0.05).In the 10μm group,the FI increased in the large intestine and excrement at 2 h,and in the kidney at 4 h(P<0.05).The presence of nano-/microplastics in tissues was further verified by histopathology.The peak time of nanoplastic absorption in blood was confirmed.Conclusion Nanoplastics translocated rapidly to observed organs/tissues through blood circulation;however,only small amounts of MPs could penetrate the organs.

Microplastic and nanoplastic exposure and risk of diabetes mellitus

The issue of plastic pollutants has become a growing concern.Both microplastics(MPs)(particle size<5 mm)and nanoplastics(NPs)(particle size<1μm)can cause DNA damage,cytotoxicity,and oxidative stress in various organisms.The primary known impacts of microplastic/nanoplastic are observed in the liver and respiratory system,leading to hepatotoxicity and chronic obstructive pulmonary disease.Although research on the effects of MPs and NPs on diabetes is still in its early stages,there are potential concerns.This editorial highlights the risk to diabetics from co-exposure to contaminants and MPs/NPs,supported by evidence from animal studies and the various chemical compositions of MPs/NPs.

Analytical methods and environmental processes of nanoplastics

The degradation of plastic debris may result in the generation of nanoplastics(NPs).Their high specific surface area for the sorption of organic pollutions and toxic heavy metals and possible transfer between organisms at different nutrient levels make the study of NPs an urgent priority.However,there is very limited understanding on the occurrence,distribution,abundant,and fate of NPs in the environment,partially due to the lack of suitable techniques for the separation and identification of NPs from complex environmental matrices.In this review,we first overviewed the state-of-the-art methods for the extraction,separation,identification and quantification of NPs in the environment.Some of them have been successfully applied for the field determination of NPs,while some are borrowed from the detection of microplastics or engineered nanomaterials.Then the possible fate and transport of NPs in the environment are thoroughly described.Although great efforts have been made during the recent years,large knowledge gaps still exist,such as the relatively high detection limit of existing method failing to detect ultralow masses of NPs in the environment,and spherical polystyrene NP models failing to represent the various compositions of NPs with different irregular shapes,which needs further investigation.

An insight into aggregation kinetics of polystyrene nanoplastics interaction with metal cations

Once inevitably released into the aquatic environment,polystyrene nanoplastics(PS-NPs)will present complicated environmental behaviors,of which the aggregation is a key process determining their environmental fate and impact.In this study,the aggregation kinetics of different sizes(30 nm and 100 nm)of PS-NPs with metal cations(Na^(+),K^(+),Ca^(2+),Mg^(2+)and Pb^(2+))at different solution pH(3,6 and 8)were investigated.The results showed that the aggregation of PS-NPs increased with cation concentration.Taking Pb^(2+)as an example,the adsorption behavior of cations onto PS-NPs was determined by transmission electron microscopy(TEM)and energy dispersive X-ray(EDX)spectroscopy,which demonstrated Pb^(2+)could be adhered onto the surface of PS-NPs with the effect of charge neutralization.The critical coagulation concentrations(CCC)of smaller PS-NPs were higher than that of larger PS-NPs for monovalent cations,whereas a different pattern is observed for divalent cations.It was suggested that there were other factors that DLVO theory does not consider affect the stability of NPs with different particle sizes.In addition,it should be noted that PS-NPs had the capacity of adsorbing large amounts of heavy metal cations and carried them transport to a long distance,and the corresponding ecological risks need to further elucidate.