Modifications of microplastics in urban environmental management systems: A review

Polystyrene microplastics and cypermethrin exposure interfered the complexity of antibiotic resistance genes and induced metabolic dysfunction in the gut of adult zebrafish

Environmental pollutants such as microplastics (MPs) and pesticides are becoming prevalent in aquatic ecosystems, posing risks to wildlife and human health. This study investigated the toxicological effects of polystyrene microplastics (PS-MPs) and cypermethrin (CYP) on adult female zebrafish (Danio rerio), focusing on intestinal microenvironment. Adsorption kinetics experimental results showed that PS-MPs can adsorb a certain amount of CYP on its surface, thereby forming a new type of composite pollutant. After exposure to red fluorescent PS-MPs for 4 days, it was found that the PS-MPs could enter the zebrafish and accumulate in the intestines. Five-month-old female zebrafish were exposed to PS-MPs, CYP, and a mixture of both for 21 days. After exposure, feces were collected and analyzed using metagenomic sequencing to determine microbial composition and functional changes. Metagenomic sequencing of naturally excreted feces showed that co-exposure synergistically reduced α-diversity and shifted community structure, with marked losses of beneficial Fusobacteriota, Firmicutes and Cetobacterium somerae and enrichment of pathogenic Preplasmiviricota. Functional annotation indicated that PS-MPs alone up-regulated glycoside hydrolases and glycosyl-transferases, whereas CYP and the co-exposure group suppressed a great number of the top 50 carbohydrate-active enzymes and decreased secondary metabolic pathways linked to amino-acid, lipid and carbohydrate metabolism pathways. Antibiotic-resistance gene (ARGs) profiling identified 57 ARG types (such as sul1, adeF, lnuC and mphA) after co-exposure. Finally, key genes related to amino acid metabolism, carbohydrate metabolism, and lipid metabolism in intestinal tissue were significantly altered. Collectively, our data demonstrated that PS-MPs and CYP exposure amplified gut dysbiosis, metabolic dysfunction and ARG complexity in zebrafish. Overall, the study highlighted the potential risks of combined environmental pollutants on intestinal microbiota, with implications for ecosystem health.

Detection of microplastics in the feline placenta and fetus

The present study aimed to detect microplastics in feline placentas and fetuses in the early stage of pregnancy. For this study, 8 pregnant queens were evaluated. A standardized protocol for the digestion of biological matter was used, as well as a plastic-free approach for sample collection and manipulation. Microplastics were investigated by means of Raman spectroscopy, with the aim of identifying their composition. Four of eight animals were contaminated, with a total of 19 microplastics detected in both fetal and placental samples. Specifically, fetuses from cats 4 and 7 were contaminated, as were the placentas from cats 5, 6, and 7. This work demonstrates that microplastics can accumulate in feline placentas even at the early stage of pregnancy. Moreover, preliminary results of the presence of microplastics in feline fetuses are shown, suggesting that microplastics can cross the placental barrier.

Characteristics and influencing factors of microplastics entering human blood through intravenous injection

The presence of microplastics in the human body and their potential health risks have drawn widespread attention in recent years. Microplastics have been detected in human blood, though their pathways of entry remain unclear. This study employed Raman spectroscopy and energy dispersive spectroscopy to evaluate the microplastic release characteristics of intravenous medical devices, aiming to investigate the influencing factors and the risk of microplastics entering the bloodstream. The results showed that microplastics were found in three widely-used medical devices, with abundances ranging from 0.44 to 2.00 items/n. Polyethylene, polypropylene (46.2 %), fragments (96.7 %), and white (86.8 %) were the predominant characteristics. Factors such as brand, specifications, and usage scenarios influence microplastic release, leading to differences in detection rates among different medical devices (0-100%). Repeated use significantly increases the risk of microplastic release (p < 0.05). Notably, built-in filtration membranes do not completely retain microplastics and may pose a risk of shedding fibers themselves. Using the exposure assessment model, the estimated microplastic release per person per year was 3.75 items for syringe, 6.22 items for infusion set, and 0.35 items for vein detained needle. Overall, although the amount of microplastics entering the human body through intravenous injection is significantly lower than that from dietary exposure and other pathways, the risk of direct entry into the bloodstream remains a concern. This research provides critical evidence for understanding the direct pathways and risks of microplastic exposure in human blood from plastic medical devices, offering significant scientific value for assessing exposure pathways and the safety of medical device use.

Microplastics and volatile organic compounds released from face masks after disinfection: Layers and materials differences

Effective disinfection methods are critical for ensuring the reusability of masks, yet these methods may inadvertently introduce health concerns associated with microplastics (MPs) and volatile organic compounds (VOCs). This study investigated the impact of ultraviolet germicidal irradiation (UVGI) and sodium hypochlorite (NaClO) bleaching on mask filter layers composed of four distinct materials. Our results revealed that UVGI induced more pronounced damage compared to bleaching, leading to the significant release of both MPs and VOCs. After UVGI treatment at conventional disinfection doses, meltblown (MB) fabrics released MPs reaching 864 ± 182 μg/g (92 ± 19 particles/g). For all filter layers, the quantity of released MPs followed the order: MB > HDPE>PU ≈ NW. These MPs were identified as degraded debris from the mask filter layers. The specific VOCs generated varied depending on the material composition. Non-woven (NW) and MB fabrics, both comprised of polypropylene, predominantly produced various branched aliphatic hydrocarbons and their derivative oxides. The cotton-like fabric, composed of high-density polyethylene, primarily emitted different linear aliphatic hydrocarbons and oxygenates. In contrast, the polyurethane filter layer of reusable masks released aromatic compounds, nitrogenous compounds, and their oxidation products. The formation of VOCs was primarily attributed to bond breakage and oxidative damage to the filter structure resulting from the disinfection process. In summary, as UVGI induced higher yields of MPs and VOCs compared to bleaching, the latter would be a safer option for mask disinfection.

Co-exposure to polystyrene microplastics and cypermethrin enhanced the effects on hepatic phospholipid metabolism and gut microbes in adult zebrafish

Microplastics (MPs) can absorb environmental pollutants from the aquatic environment to cause mixed toxicity, which has received widespread attention. However, studies on the joint effects of MPs and insecticides are limited. As one of the most widely used pyrethroids, there was a large amount of residual cypermethrin (CYP) in water due to insufficient decomposition. Here, adult female zebrafish were exposed to MPs, CYP, and their mixtures for 21 days, respectively. After exposures, the MPs and CYP caused tissue damage to the liver. Hepatic triglyceride (TG) level increased significantly after MPs + CYP exposure, and the expression of genes about glycolipids metabolism was significantly altered. Furthermore, metabolome results suggested that MPs + CYP exposure resulted in increased content of some glycerophospholipid, affecting phospholipid metabolism-related pathways. In addition, through 16 s rDNA sequencing, it was found that MPs + CYP led to significant changes in the proportion of dominant phyla. Interestingly, Cetobacterium which increased in CYP and the co-exposure group was positively correlated with most lipid metabolites. Our results suggested that co-exposure to MPs and CYP enhanced the disturbances in hepatic phospholipid metabolism by affecting the gut microbial composition, while these changes were not observed in separate treatment groups. These results emphasized the importance of studying the joint toxicity of MPs and insecticides.

Characteristics and ecological risks of microplastic pollution in a tropical drinking water source reservoir in Hainan province, China

Microplastic (<5 mm) pollution has become a pressing environmental concern in recent years. The present study investigated the occurrence characteristics and assessed the ecological risk of microplastics in the surface water and sediment of the Chitian Reservoir, a drinking water source in Hainan province (China). The results indicated that microplastics were detected in the surface water and sediment of the Chitian Reservoir and its surrounding areas. The overall abundance of microplastics in the water was 3.05 ± 1.16 items per L and in the sediment was 0.15 ± 0.06 items per g dry weight, which is relatively low compared to other reservoirs in China. The dominant components of microplastics detected in the Chitian Reservoir were polypropylene (PP), rayon, and polyester. Physical morphology analysis of microplastics showed that fibers with small particle sizes (<1 mm) and white color were the predominant characteristics in both the surface water and sediment. The domestic sewage from surrounding residents and agricultural wastewater may be the primary sources of microplastics in the reservoir. Ecological risk assessment revealed that the overall pollution load index (PLI) in the surface water (0.65) and sediment (0.51) of the Chitian Reservoir and its surrounding area is at a low level. The potential ecological hazards (RI) of microplastics (0.13 to 336.78 in water; 0.23 to 465.93 in sediment) in most sites fall within the scope of level I, but those in a few sites are at level II due to the presence of polyvinyl chloride (PVC). This study enriches the data on microplastic pollution in inland reservoir systems, providing fundamental reference information for future ecotoxicological studies and the management of microplastic pollution control.

Interfacial quantum chemical characterization of aromatic organic matter adsorption on oxidized microplastic surfaces

Examining the adsorption efficiency of individual contaminants on microplastics (MPs) is resource-intensive and time-consuming. To address this challenge, combined laboratory adsorption experiments with model simulations were performed to investigate the adsorption capacities and mechanisms of MPs before and after aging. Our adsorption experiments revealed that aged polyethylene (PE) and polyvinyl chloride (PVC) MPs exhibited increased adsorption capacity for benzene, phenol, and naphthalene. Additionally, density functional theory (DFT) simulations provided insights into changes in adsorption sites, adsorption energy, and charge density on MPs. The π bond of the benzene ring emerged as a pivotal factor in the adsorption process, with van der Waals forces exerting dominant influence. For instance, the adsorption energy of benzene on pristine PE was -0.01879 eV. When oxidized groups, such as hydroxyl, carbonyl, and carboxyl, on the surface of aged PE became the adsorption sites, the adsorption energy increased to -0.06976, -0.04781, and -0.04903 eV, respectively. Regions with unoxidized functional groups also exhibited higher adsorption energies than pristine PE. These results indicated that aged PE had a stronger affinity for benzene compared to pristine PE, enhancing its adsorption. Charge density difference and energy density of states corroborated this observation, revealing larger π-bond charge accumulation areas for benzene on aged PE, suggesting stronger dipole interactions and enhanced adsorption. Similar trends were observed for phenol and naphthalene. In summary, the DFT calculations aligned with the adsorption experiment findings, confirming the effectiveness of simulation methods in predicting changes in the adsorption performance of aged MPs.

It matters how we measure - Quantification of microplastics in drinking water by μFTIR and μRaman

The water treatment for microplastics (MP) at a Danish groundwater-based waterworks was assessed by Fourier-Transform IR micro-spectroscopy (μFTIR) (nominal size limit 6.6 μm) and compared to results from Raman micro-spectroscopy (μRaman) (nominal size limit 1.0 μm) on the same sample set. The MP abundance at the waterworks' inlet and outlet was quantified as MP counts per cubic metre (N/m3) and estimated MP mass per cubic metre (μg/m3). The waterworks' MP removal efficiency was found to be higher when analysing by μFTIR (counts: 78.14 ± 49.70%, mass: 98.73 ± 11.10%) and less fluctuating than when using μRaman (counts: 43.2%, mass: 75.1%). However, both techniques pointed to a value of ∼80% for the counts' removal efficiency of MPs >6.6 μm. Contrarily to what was shown by μRaman, no systematic leaking of MPs from the plastic elements of the facility could be identified for the μFTIR dataset, either from the counts (inlet 31.86 ± 17.17 N/m3, outlet 4.98 ± 2.09 N/m3) or mass estimate (inlet 76.30 ± 106.30 μg/m3, outlet 2.81 ± 2.78 μg/m3). The estimation of human MP intake from drinking water calculated from the μFTIR data (5 N/(year·capita)) proved to be approximately 332 times lower than that calculated from the μRaman dataset, although in line with previous studies employing μFTIR. By merging the MP length datasets from the two techniques, it could be shown that false negatives became prevalent in the μFTIR dataset already below 50 μm. Further, by fitting the overall frequency of the MP length ranges with a power function, it could be shown that μFTIR missed approximately 95.7% of the extrapolated MP population (1-1865.9 μm). Consequently, relying on only μFTIR may have led to underestimating the MP content of the investigated drinking water, as most of the 1-50 μm MP would have been missed.

Gaseous products generated from polyethylene and polyethylene terephthalate during ultraviolet irradiation: Mechanism, pathway and toxicological analyses

The generation of various degradation products from microplastics (MPs) has been confirmed under ultraviolet (UV) irradiation. The gaseous products, primarily volatile organic compounds (VOCs), are usually overlooked, leading to potential unknown risks to humans and the environment. In this study, the generation of VOCs from polyethylene (PE) and polyethylene terephthalate (PET) under UV-A (365 nm) and UV-C (254 nm) irradiation in water matrixes were compared. More than 50 different VOCs were identified. For PE, UV-A-derived VOCs mainly included alkenes and alkanes. On this basis, UV-C-derived VOCs included various oxygen-containing organics, such as alcohols, aldehydes, ketones, carboxylic acid and even lactones. For PET, both UV-A and UV-C irradiation induced the generation of alkenes, alkanes, esters, phenols, etc., and the differences between these two reactions were insignificant. Toxicological prioritization prediction revealed that these VOCs have diverse toxicological profiles. The VOCs with the highest potential toxicity were dimethyl phthalate (CAS: 131-11-3) from PE and 4-acetylbenzoate (3609-53-8) from PET. Furthermore, some alkane and alcohol products also presented high potential toxicity. The quantitative results indicated that the yield of these toxic VOCs from PE could reach 10² μg g^-1 under UV-C treatment. The degradation mechanisms of MPs included direct scission by UV irradiation and indirect oxidation induced by diverse activated radicals. The former mechanism was dominant in UV-A degradation, while UV-C included both mechanisms. Both mechanisms contributed to the generation of VOCs. Generally, MPs-derived VOCs can be released from water to the air after UV irradiation, posing a potential risk to ecosystems and human beings, especially for UV-C disinfection indoors in water treatments.

Do drinking water plants retain microplastics? An exploratory study using Raman micro-spectroscopy

The retainment of microplastics (MPs) down to 1 μm by a Danish drinking water plant fed with groundwater was quantified using Raman micro-spectroscopy (μRaman). The inlet and outlet were sampled in parallel triplicates over five consecutive days of normal activity. For each triplicate, approximately 1 m³ of drinking water was filtered with a custom-made device employing 1 μm steel filters. The MP abundance was expressed as MP counts per liter (N/L) and MP mass per liter (pg/L), the latter being estimated from the morphological parameters provided by the μRaman analysis. Hence the treated water held on average 1.4 MP counts/L, corresponding to 4 pg/L. The raw water entering the sand filters held a higher MP abundance, and the overall efficiency of the treatment was 43.2% in terms of MP counts and 75.1% in terms of MP mass. The reason for the difference between count-based and mass-based efficiencies was that 1-5 μm MP were retained to a significantly lower degree than larger ones. Above 10 μm, 79.6% of all MPs were retained by the filters, while the efficiency was only 41.1% below 5 μm. The MP retainment was highly variable between measurements, showing an overall decreasing tendency over the investigated period. Therefore, the plastic elements of the plant (valves, sealing components, etc.) likely released small-sized MPs due to the mechanical stress experienced during the treatment. The sub-micron fraction (0.45-1 μm) of the samples was also qualitatively explored, showing that nanoplastics (NPs) were present and that at least part hereof could be detected by μRaman.

Analysis of microplastics released from plastic take-out food containers based on thermal properties and morphology study

Plastic take-out food containers may release microplastics (MPs) into food and pose a potential risk to food safety and human health. Here, after being subjected to hot water treatment, MPs released from three types of plastic food containers (polypropylene, PP; polyethylene, PE; expanded polystyrene, EPS) were identified by micro-Raman spectroscopy. The results showed that the size of released MPs ranged from 0.8-38 μm and over 96% MPs were smaller than 10 μm. Various MPs concentrations were found from the three types of containers, that is, 1.90 × 10⁴, 1.01 × 10⁵, and 2.82 × 10⁶ particles/L on average from PP, PE, and EPS, respectively. Moreover, based on thermal and morphology analysis, we discovered that both relaxations of the polymer chains in the rubbery state and defects caused by processing techniques might contribute to the release of MPs. Thus, such release can be reduced by increasing the thermal stability of the materials and mitigating the defects generated during production.

Release of millions of micro(nano)plastic fragments from photooxidation of disposable plastic boxes

The widespread use of disposable plastic boxes is exacerbating the dangers of microplastics (MPs); however, little is known about the fragmentation behavior of MPs during aging. In this study, the dynamic evolution on the release of micro(nano)plastics and photoaging properties of two disposable plastic boxes (polypropylene (PP) and polystyrene (PS)) were investigated under light irradiation and mechanical abrasion. Results showed that the weight of PP and PS was decreased by 53 % and 100 %, respectively after 60 d of ultraviolet irradiation (UV60). Moreover, a large number of fragmented particles were produced from the combined light irradiation and abrasion, with 0.142 ± 0.006 and 0.141 ± 0.013 million micro(nano)plastics/mL particles from PP and PS boxes, respectively, and the nanometer range (<100 nm) accounted for 70.8 % and 46.8 %. The correlation model of the average size or alteration time versus carbonyl index (CI) was developed, which indicated that the fragmentation behavior was mainly related to the photooxidation, though mechanical abrasion also played a certain enhancing role. Additionally, PS was susceptible to the fragmentation and photooxidation compared to PP possibly since the phenyl ring of PS was more vulnerable to UV attack than the methyl of PP. The findings of this study clarify the dynamic fragmentation process of micro(nano)plastics of disposable plastic boxes and provide useful information to access environmental fate of MPs more holistically.

Release of microplastics and nanoplastics in water from disposable surgical masks after disinfection

During the COVID-19 pandemic, disposable surgical masks were generally disinfected and reused due to mask shortages. Herein, the role of disinfected masks as a source of microplastics (MPs) and nanoplastics (NPs) was investigated. The amount of MPs and NPs released from masks disinfected by UV ranged from 1054 ± 106 to 2472 ± 70 and from 2.55 ± 0.22 × 10⁹ to 6.72 ± 0.27 × 10⁹ particles/piece, respectively, comparable to that of the undisinfected masks, and the MPs were changed to small-sized particles. The amount of MPs and NPs released after alcohol and steam treatment were respectively lower and higher than those from undisinfected masks, and MPs were shifted to small-sized particles. The amount of MPs and NPs released in water after autoclaving was lower than for undisinfected masks. In all, the amount of fibers released after disinfection decreased greatly, and certain disinfection processes were found to increase the amount of small-sized NPs released from masks into aqueous environments.