Joint toxicity of microplastics with triclosan to marine microalgae Skeletonema costatum

Interactions of microplastics and organic compounds in aquatic environments: A case study of augmented joint toxicity

High levels of persistent contaminants such as microplastics (MPs) and trace organic compounds (TrOCs) in the aquatic environment have become a major threat on the ecosystem and human health. While MP's role as a vector of environmental TrOCs is widely discussed in the literature, the corresponding implications of the interaction between these two compounds on human health (i.e., their joint toxic effect) have not been illustrated. Using a TrOCs model (Triclosan, TCS) and primary MPs (polystyrene microbeads), this work evaluates the sorption and desorption potential of TCS and MPs in simulated environmental and cellular conditions, respectively, and estimates the single and joint toxicity of these interactions toward human cells (Caco-2). Surface functionality of the microbeads highly increased their adsorption capacity of TCS, from 2.3 mg TCS for non-functionalized microbeads to 4.6 mg and 6.1 mg TCS per gram of microbeads for amino- and carboxyl-functionalized MPs, respectively. Using non-functionalized MPs, non-specific "hydrophobic-like" interactions and π-π interactions dominated the sorption mechanism of TCS; however, the addition of hydrogen interactions between functionalized microbeads and TCS increased the microbeads' overall sorption capacity. TCS was desorbed from both functionalized and non-functionalized MPs when changing from environmental conditions to cellular conditions. Desorption was found to be dependent on the matrix complexity and protein content as well as microbead functionality. Finally, toxicity tests suggested that while low concentrations of TCS and MPs (separately) have minor toxic effect toward Caco-2 cells, TCS-sorbed MPs at similar concentrations have an order of magnitude higher toxicity than pristine MPs, potentially associated with the close interaction of both MP and TCS with the cells. Overall, this study not only elucidates the role of MPs as a TrOC vector, but also demonstrates a realistic scenario in which co-presence of these environmental contaminants poses risks to the environment and human health.

Interactive effects of polymethyl methacrylate (PMMA) microplastics and salinity variation on a marine diatom Phaeodactylum tricornutum

Until now, knowledge about the interactive effects of microplastics and environmental factors on primary producers is quite limited. In this work, a marine diatom (Phaeodactylum tricornutum) was exposed to polymethyl methacrylate (PMMA) microplastics at different salinities (25, 35, and 45‰) for 10 days in order to study their interactive effects. Results showed that growth of P. tricornutum was negatively affected by PMMA microplastics and salinity variation with a minimum EC₅₀ value of 91.75 mg L^-1. Photosynthetic activity of P. tricornutum was also inhibited by the two factors, and their interactive effects on chlorophyll fluorescence parameters (F_v/F_m and Φ_PSII) were significant. In the algal cells, soluble protein accumulated, activities of two antioxidant enzymes changed, and malondialdehyde (MDA) content increased when this diatom was exposed to the microplastics at different salinities. These data would help to evaluate the risks of microplastics to primary producers under different environmental factors.

Critical review of the characteristics, interactions, and toxicity of micro/nanomaterials pollutants in aquatic environments

A wide range of contaminants of emerging concern such as micro/nanoplastics (MPs/PNPs) and metal-nanoparticles (Me-NPs) from anthropogenic activities have been identified in aquatic environments. The hazardous effects of these micro/nanomaterials as pollutants in organisms and the lack of knowledge about their behavior in aquatic environments have generated growing concern in the scientific community. The nanomaterials have a colloidal-type behavior due to their size range but with differences in their physicochemical properties. This review comprises the behavior of micro/nanomaterials pollutants and the physicochemical interactions between MPs/PNPs and Me-NPs in aquatic environments, and their potential toxicological effects in organisms. Moreover, this article describes the potential use of Me-NPs to remove MPs/PNPs present in the water column due to their photocatalytic and magnetic properties. It also discusses the challenge to determine harmful effects of micro/nanomaterials pollutants in organisms and provides future research directions to improve integrated management strategies to mitigate their environmental impact.

Chemical composition and particle size influence the toxicity of nanoscale plastic debris and their co-occurring benzo(α)pyrene in the model aquatic organisms Daphnia magna and Danio rerio

Little is known about how particle chemical composition and size might influence the toxicity of nanoscale plastic debris (NPD) and their co-occurring chemicals. Herein, we investigate the toxicity of 3 × 10¹⁰ particles/L polyethylene (PE, 50 nm), polypropylene (PP, 50 nm), polystyrene (PS, 200 and 600 nm), and polyvinyl chloride (PVC, 200 nm) NPD and their co-occurring benzo(a)pyrene (BaP) to Daphnia magna and Danio rerio. During the 21 days of exposure to PE 50 nm and PS 200 nm, the number of broods produced by D. magna decreased compared to other treatments. Exposure to BaP alone did not produce any effects on the reproduction of the daphnids, however, the mixture of BaP with PS (200 or 600 nm) or with PE (50 nm) reduced the number of broods. Exposure of D. rerio embryos to PE 50 nm, PS 200 nm, and PS 600 nm led to a delay in the hatching. The presence of PS 200 nm and PVC 200 nm eliminated the effects of BaP on the hatching rate of zebrafish. Our findings suggest that data generated for the toxicity of one type of NPD, e.g. PVC or PS may not be extrapolated to other types of NPD.

Microplastics and trace metals in fish species of the Gulf of Mannar (Indian Ocean) and evaluation of human health

The importance of microplastic (MPs) contamination in marine environments is reflected by increasing number of studies in fish species. Some even dedicated to the toxicological effects from the ingestion. Microplastics (MPs) and their trace metal composition were examined in the muscle and intestine of five commercially important fish species (i.e., Sufflamen fraenatus, Heniochus acuminatus, Atropus atropos, Pseudotriacanthus and Leiognathus brevirostris) from Thoothukudi at the Gulf of Mannar coast in south India. The abundance and morphology of MPs (size, shape, and texture) in muscle and intestinal were investigated by micro-Fourier Transform Infrared Spectroscopy (μ-FT-IR) and atomic force microscope (AFM). ICP-OES was used to investigate the adsorption/leaching of trace metals in microplastics in order to assess health risk for adults and children. Particles of 100-250 μm and white color dominated, and the mean abundances (items/100 g) of total MPs were more in Pseudotriacanthus (muscle: 51.2; intestine: 50.1) compared to Heniochus acuminatus (muscle: 9.6; intestine: 15), Leiognathus brevirostris (muscle: 12; intestine: 13.2) and Atropus atropus (muscle: 15.2; intestine: 44.1). Polyethylene (35.3%), polypropylene (27.2%), polyamide (nylon) (22.2%) and fiber (15.3%) represented the MPs present in muscles, and polyamide (nylon) (30.2%), polyethylene (28.1%), polypropylene (25.9%), and fiber (15.8%) composed the intestine MPs. We estimated possible consumption of 121-456 items of MPs/week by adults and about 19-68 items of MPs/week by children by considering the sizes of safe meals. Zn, Cu, Mn and Cr in these fish species reflected influence of the sewage waste. However, the non-carcinogenic risk evaluated through EDI, THQ, HI, and CR did not suggest any immediate health problem for the consumers.

Unraveling individual and combined toxicity of nano/microplastics and ciprofloxacin to Synechocystis sp. at the cellular and molecular levels

Although nanoplastics/microplastics (NPs/MPs) may interact with co-contaminants (e.g. antibiotics) in aquatic systems, little is known about their combined toxicity. Here, we compared the individual toxicity of NPs/MPs or ciprofloxacin (CIP, a very commonly detected antibiotic) and their combined toxicity toward a unicellular cyanobacterium Synechocystis sp. in terms of the cellular responses and metabolomic analysis. We found that CIP exhibited an antagonistic effect with NPs/MPs due to its adsorption onto the surface of NPs/MPs. Particle size-dependent toxic effects of NPs/MPs were observed. Reactive oxygen species (ROS) was verified as an important factor for NPs/MPs to inhibit cell growth, other than for CIP. Metabolomics further revealed that Synechocystis sp. up-regulated glycerophospholipids, amino acids, nucleotides, and carbohydrates to tolerate CIP pressure. NPs/MPs downregulated the TCA cycle and glycerophospholipids metabolism and impaired the primary production and membrane integrity via adhesion with Synechocystis sp.. Additionally, the toxicity of NPs/MPs throughout ten growth cycles at a sublethal concentration unveiled its potential risks in interfering with metabolism. Collectively, our findings provide insights into the joint ecotoxicity of NPs/MPs and antibiotics, and highlight the potential risks of co-pollutants at environmental relevant concentrations.

Comparative growth and cellular responses of toxigenic Microcystis exposed to different types of microplastics at various doses

Microplastics (MPs) pollution frequently co-occur with Microcystis-dominated blooms in freshwaters, but MPs effects on toxigenic Microcystis growth and effect mechanisms remained poorly understood. This study used 0.5 μm-size polyethylene (PE) and polyvinyl chloride (PVC) to explore dose- and time-dependent effects of single and combined MPs (i.e., PE + PVC) on toxigenic Microcystis growth and cellular responses during 16 day-test. Results showed that Microcystis growth and cellular responses depended on exposure time, MPs dose and type. MPs elicited hormesis effect in early stage at low dose (5 mg/L), while increasingly inhibited growth with rising PVC or PE + PVC dose but declining PE dose (5, 10, 50 mg/L) in mid-late stage, with stress intensity of PE + PVC > PVC > PE. Further analyses revealed unobvious cell damage under MPs stress, largely because antioxidases were increasingly activated as MPs stress enhanced. Unicellular MCs release ability during mid stage almost coincided with total/bound amount and each fraction of ex-poly and ex-pro trends under MPs stress. Significant positive relationship existed between MCs release ability and ex-poly/ex-pro fractions and total amount of Microcystis cells along mid-late stage under MPs stress, validating that ex-poly/ex-pro production was regulated as a result of MCs release. Besides, unicellular MCs production ability was generally positively correlated with soluble, tightly-bound and total ex-poly and ex-pro at late stage. These suggested that cellular antioxidants, MCs production/release ability and ex-poly/ex-pro production of Microcystis could be coupled to exert integrated defense against MPs stress to protect surviving cells in Microcystis population. These findings are crucial for acquiring the fate of Microcystis-dominated blooms co-occurring with MPs pollution, and reasonably assessing and managing involved eco-risks.

Micro-polyethylene particles reduce the toxicity of nano zinc oxide in marine microalgae by adsorption

Contaminant adsorption by microplastics (MPs) allows them to act as contaminant vehicles or vectors, complicating eco-toxicological study of MPs. The contaminants adsorbed are mainly organic contaminants, especially hydrophobic organic contaminants (HOCs), although heavy-metal adsorption has also been reported. Compared to the mechanisms of HOC adsorption, those for metals are not fully understood. In the present study, combined-exposure assays revealed that polyethylene microplastics (PEMPs, 150 μm) alleviate the toxic effect of nano zinc oxide (nZnO, 20-30 nm) on marine microalgal growth by 14.4%. Thus, we hypothesized that nZnO adsorption onto PEMP surfaces ameliorates its toxicity to microorganisms. To test this hypothesis, PEMP samples isolated from nZnO suspensions were characterized. Their surfaces were observed by SEM, their Zn levels were measured by ICP-MS, and the compound form of Zn on the PEMP surface was determined by XRD analysis. The results indicated that 5.53%-7.16% of the Zn in the suspension is adsorbed during the first 24 h of exposure and that the Zn remains as the ZnO form upon adsorption. The findings in the present study provide important information on the role of MPs as metal oxide vehicles.

Ecological implications beyond the ecotoxicity of plastic debris on marine phytoplankton assemblage structure and functioning

Plastic pollution is a global issue posing a threat to marine biota with ecological implications on ecosystem functioning. Micro and nanoplastic impact on phytoplankton autotrophic species (e.g., cell growth inhibition, decrease in chlorophyll a and photosynthetic efficiency and hetero-aggregates formation) have been largely documented. However, the heterogeneity of data makes rather difficult a comparison based on size (i.e. micro vs nano). In addition, knowledge gaps on the ecological impact on phytoplankton assemblage structure and functioning are evident. A new virtual meta-analysis on cause-effect relationships of micro and nanoplastics on phytoplankton species revealed the significant effect posed by polymer type on reducing cell density for tested PVC, PS and PE plastics. Linked with autotrophic phytoplankton role in atmospheric CO₂ fixation, a potential impact of plastics on marine carbon pump is discussed. The understanding of the effects of microplastics and nanoplastics on the phytoplankton functioning is fundamental to raise awareness on the overall impact on the first level of marine food web. Interactions between micro and nanoplastics and phytoplankton assemblages have been quite documented by in vitro examinations; but, further studies considering natural plankton assemblages and/or large mesocosm experiments should be performed to evaluate and try predicting ecological impacts on primary producers.

Effects of polystyrene and triphenyl phosphate on growth, photosynthesis and oxidative stress of Chaetoceros meülleri

The toxicity of microplastics to marine organisms has attracted much attention; however, studies of their effects on marine microalgae remain limited. Here, the effects of the single and combined toxicity of polystyrene (PS) and triphenyl phosphate (TPhP) on the cell growth, photosynthesis, and oxidative stress of Chaetoceros meülleri were investigated. PS inhibited growth of the algae cells and caused a dose-dependent effect on oxidative stress. The significantly high production of reactive oxygen species (ROS) induced severe cell membrane damage, as confirmed by high fluorescence polarization. However, there was no obvious decrease in chlorophyll a content, and 80 mg/L of PS significantly promoted chlorophyll a synthesis. The TPhP also inhibited cell growth, except at low concentrations (0.2-0.8 mg/L), which stimulated algae growth over 48 h. Moreover, no obvious decrease in chlorophyll a and maximal photochemical efficiency of PSII was found in the TPhP experimental groups except for 3.2 mg/L TPhP, where the rapid light curves showed a significantly reduced photosynthetic capacity of algae. In addition, TPhP caused high ROS levels at 96 h, resulting in cell membrane damage. Using the additive index and independent action methods, the combined toxic effects of PS and TPhP on the algae were evaluated as antagonistic; however, cell membrane damage caused by high ROS levels was still noticeable. This study has shown the potential toxicity of PS and TPhP to marine microalgae, and provided insights into the combined risk assessment of TPhP and microplastics in the marine environment.

Particulate plastics-plant interaction in soil and its implications: A review

Particulate plastics (<5 mm), including macroplastics (1 μm to 5 mm), microplastics (100 nm to 1 μm) and nanoplastics (<100 nm), have become a global environmental problem due to their widespread occurrence, distribution and ecosystem risk. Although numerous studies on particulate plastics have been conducted in aquatic systems, investigations in the soil ecosystem are lacking. Soil is the main storage place of particulate plastics, conferring significant impacts on plant growth and development. The impact of particulate plastics on plants is directly related to the safety of agricultural products. This review comprehensively examines the pollution characteristics and exposure pathways of particulate plastics in agricultural soils, highlighting plastic uptake process, and mechanisms in plants, and effects of particulate plastics, biodegradable particulate plastics and combined pollution of plastics with other environmental pollutants on plant performances. This review identifies a number of future research prospects including the development of accurate quantitative methods for plastic analysis in soil and plant samples, understanding the environmental behaviors of conventional and biodegradable particulate plastics in the presence and absence of other environmental pollutants, unravelling the fate of particulate plastics in plants, phyto-toxicity and molecular regulatory mechanisms of particultate plastics, and developing best management practices for the production of safe agricultural products in plastic-contaminated soils.

Micrometer scale polystyrene plastics of varying concentrations and particle sizes inhibit growth and upregulate microcystin-related gene expression in Microcystis aeruginosa

Microplastics (MPs) are a concerning environmental pollutant due to their adverse effects on aquatic organisms. However, the dose- and size-dependent effects of MPs on toxigenic cyanobacteria have not been extensively studied. Herein, we explored the effects of polystyrene MPs (PS-MPs) of varying particle sizes and concentrations on the growth and physiology of Microcystis aeruginosa. The results showed that exposure to 1 µm PS-MPs at a concentration of 2-10 mg L^-1 significantly inhibited the growth of M. aeruginosa in a concentration-dependent manner. After 12 days of exposure, high concentrations of 1 µm PS-MPs (≥ 2 mg L^-1) increased levels of reactive oxygen species. Following exposure to 5 mg L^-1 PS-MPs of different particle sizes, algal growth was inhibited and oxidative stress was induced by 0.5 and 1 µm PS-MPs. At the molecular level, transcription of the atpB gene was generally downregulated in all PS-MPs treatments, while ftsH and fabZ were upregulated. Exposure to PS-MPs also altered the transcription levels of microcystin-related genes (mcyA and mcyH), causing more microcystin to be produced by M. aeruginosa. The results will be useful for understanding the toxicity of MPs toward toxigenic cyanobacteria, and evaluating the ecological risks of MPs in aquatic environments.

Biomarkers-based assessment of triclosan toxicity in aquatic environment: A mechanistic review

Triclosan (TCS), an emergent pollutant, is raising a global concern due to its toxic effects on organisms and aquatic ecosystems. The non-availability of proven treatment technologies for TCS remediation is the central issue stressing thorough research on understanding the underlying mechanisms of toxicity and assessing vital biomarkers in the aquatic organism for practical monitoring purposes. Given the unprecedented circumstances during COVID 19 pandemic, a several-fold higher discharge of TCS in the aquatic ecosystems cannot be considered a remote possibility. Therefore, identifying potential biomarkers for assessing chronic effects of TCS are prerequisites for addressing the issues related to its ecological impact and its monitoring in the future. It is the first holistic review on highlighting the biomarkers of TCS toxicity based on a comprehensive review of available literature about the biomarkers related to cytotoxicity, genotoxicity, hematological, alterations of gene expression, and metabolic profiling. This review establishes that biomarkers at the subcellular level such as oxidative stress, lipid peroxidation, neurotoxicity, and metabolic enzymes can be used to evaluate the cytotoxic effect of TCS in future investigations. Micronuclei frequency and % DNA damage proved to be reliable biomarkers for genotoxic effects of TCS in fishes and other aquatic organisms. Alteration of gene expression and metabolic profiling in different organs provides a better insight into mechanisms underlying the biocide's toxicity. In the concluding part of the review, the present status of knowledge about mechanisms of antimicrobial resistance of TCS and its relevance in understanding the toxicity is also discussed referring to the relevant reports on microorganisms.

Effects of Nanoplastics on the Dinoflagellate Amphidinium carterae Hulburt from the Perspectives of Algal Growth, Oxidative Stress and Hemolysin Production

Recently, the effects of nanoplastics (NPs) on aquatic organisms have attracted much attention; however, research on the toxicity of NPs to microalgae has been insufficient. In the present study, the effects of polystyrene nanoplastics (nano-PS, 50 nm) on growth inhibition, chlorophyll content, oxidative stress, and algal toxin production of the marine toxigenic dinoflagellate Amphidinium carterae Hulburt were investigated. Chlorophyll synthesis was promoted by nano-PS on day 2 but was inhibited on day 4; high concentrations of nano-PS (≥50 mg/L) significantly inhibited the growth of A. carterae. Moreover, despite the combined effect of superoxide dismutase (SOD) and glutathione (GSH), high reactive oxygen species (ROS) level and malondialdehyde (MDA) content were still induced by nano-PS (≥50 mg/L), indicating severe lipid peroxidation. In addition, the contents of extracellular and intracellular hemolytic toxins in nano-PS groups were significantly higher than those in control groups on days 2 and 8, except that those of extracellular hemolytic toxins in the 100 mg/L nano-PS group decreased on day 8 because of severe adsorption of hemolytic toxins to the nano-PS. Hence, the effects of nano-PS on A. carterae are closely linked to nano-PS concentration and surface properties and exposure time. These findings provide a deep understanding of the complex effects of NPs on toxigenic microalgae and present valuable data for assessing their environmental risks.

Toxicity mechanisms of polystyrene microplastics in marine mussels revealed by high-coverage quantitative metabolomics using chemical isotope labeling liquid chromatography mass spectrometry

Marine microplastic has become an important environmental issue of global concern due to its wide distribution and harmful impacts. However, there is still insufficient information on the toxicity mechanism of microplastics to marine organisms. In this study, we developed and applied a high-coverage quantitative metabolomics technique to investigate the toxicity mechanisms of the polystyrene microspheres (micro-PS) on marine mussels (Mytilus coruscus). A total of 3599 metabolites were quantified, including 163 positively identified metabolites, 318 high-confident putatively identified metabolites, and 2602 mass-matched metabolites from the hemolymph of mussels. Metabolomics analysis indicated that micro-PS disrupted the amino acid metabolism, particularly phenylalanine metabolism, which may lead to oxidative stress and neurotoxicity. Micro-PS at environmentally relevant concentrations induced oxidative stress and immunotoxicity in mussels. After 7 days of recovery, along with the significant clearance of micro-PS by mussels, both metabolite levels and biochemical indicators generally returned to the same level as the control group. Overall, the results showed that microplastics at environmentally-relevant concentrations can cause toxic effects on mussels but these influences are reversible. We envisage the usages of high-coverage metabolomics for investigating the toxicity of various types of microplastics under many different conditions, including those relevant to the marine environment.

Microplastics and plankton: Knowledge from laboratory and field studies to distinguish contamination from pollution

Due to their ubiquitous presence, size and characteristics as ability to adsorb pollutants, microplastics are hypothesized as causing a major impact on smaller organisms, such as plankton. Despite this, there is a need to determine whether these impacts just relate to the environmental presence of the materials or their effects on biological processes. Therefore, we aimed to 1) review current research on plankton and microplastics; 2) compare field and laboratory experimental findings, and 3) identify knowledge gaps. The systematic review showed that 70% of the 147 relevant scientific publications were from laboratory studies and microplastics interactions with plankton were recorded in 88 taxa. Field study publications were relatively scarce and the characteristics of microplastics collected in the field were very different from those used in laboratory experiments thereby limiting the comparison between studies. Our systematic review highlighted knowledge gaps in: 1) the number of field studies; 2) the non-comparability between laboratory and field conditions, and 3) the low diversity of plankton species studied. Furthermore, this review indicated that while there are many studies on contamination by microplastics, the effects of this contamination (i.e., pollution per se) have been less well-studied, especially in the field at population, community, and ecosystem levels.

Combined hepatotoxicity of imidacloprid and microplastics in adult zebrafish: Endpoints at gene transcription

Microplastics (MPs) and pesticides are two kinds of ubiquitous pollutants that can pose a health risk to aquatic organisms. However, researches about the combined effects of MPs and pesticides are very limited. A simple combined exposure model was established in this study, adult zebrafish were exposed to 100 μg/L imidacloprid (IMI), 20 μg/L polystyrene microplastics (PS), and a combination of PS and IMI (PS + IMI) for 21 days. The results demonstrated that exposure to PS and IMI inhibited the growth of zebrafish and altered the levels of glycolipid metabolism and oxidative stress-related biochemical parameters. While gene expression analysis revealed that, compared with PS or IMI treatment group, combined exposure caused a greater change in gene expression levels involving the process of glycolipid metabolism (Gk, Hk1, Aco, PPar-α, Cpt1, Acc, Fas, PPar-γ, Apo) and inflammatory response (IL-1β, IL-6, IL-8, TNF-α, IL-10). The results demonstrated that even combined exposure of low concentrations of PS and IMI could cause more severe hepatotoxicity in zebrafish, especially in terms of gene transcription. And more combined toxicity studies are essential for MPs and pesticides risk assessment.

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.

Aged microplastics decrease the bioavailability of coexisting heavy metals to microalga Chlorella vulgaris

Environmental aging of ubiquitous microplastics (MP) occurs through the action of biotic and abiotic factors, and aged MP exhibit different physicochemical properties and environmental behavior from virgin MP. This study aimed to investigate the aged micro-sized polystyrene (mPS) and polyvinyl chloride (mPVC), and the heavy metals copper (Cu) and cadmium (Cd), and examine the effects of their combined toxicities on microalga Chlorella vulgaris. Results showed that the presence of MP inhibited cell growth as compared with the control, the inhibition rate (I) decreased as concentrations of MP rose and aged MP exhibited stronger inhibition of cells than did virgin MP. The largest I was achieved in each culture with the MP concentration of 0.01 g/L, in which aged mPS with the maximal of 36.84% (I_{aged mPS}) followed by aged mPVC (I_{aged mPVC} = 30.03%), virgin mPS (I_{virgin mPS} = 29.10%) and virgin mPVC (I_{virgin mPVC} = 16.72%). Addition of the heavy metals Cu²⁺ and Cd²⁺ significantly inhibited cell growth, and toxicity increased with concentrations in a range of 0.5-2.0 mg/L; the maximum I values were 19.50% (I_Cu) and 85.14% (I_Cd), respectively. The combined toxicity of aged MP + Cu or aged MP + Cd was less than that of individual heavy metals. In particular, as compared with the maximal I_Cd of 85.14% achieved by single Cd²⁺, the toxicity of Cd²⁺ was greatly reduced when combined with aged mPS and mPVC, with the I value decreased to 27.55% (I_{aged mPS}) and 32.51% (I_{aged mPVC}), respectively. Both single and combined treatments caused cell damage to the microalga, accompanied by increased superoxide dismutase (SOD) and intracellular malonaldehyde (MDA) content.

Current Progress on Marine Microplastics Pollution Research: A Review on Pollution Occurrence, Detection, and Environmental Effects

Recently, microplastics pollution has attracted much attention in the environmental field, as researchers have found traces of microplastics in both marine and terrestrial ecological environments. Here, we reviewed and discussed the current progress on microplastics pollution in the marine environment from three main aspects including their identification and qualification methods, source and distribution, and fate and toxicity in a marine ecosystem. Microplastics in the marine environment originate from a variety of sources and distribute broadly all around the world, but their quantitative information is still lacking. Up to now, there have been no adequate and standard methods to identify and quantify the various types of microplastics, which need to be developed and unified. The fate of microplastics in the environment is particularly important as they may be transferred or accumulated in the biological chain. Meanwhile, microplastics may have a high adsorption capacity to pollutants, which is the basic research to further study their fate and joint toxicity in the environment. Therefore, all the findings are expected to fill the knowledge gaps in microplastics pollution and promote the development of relative regulations.

The joint effect of parental exposure to microcystin-LR and polystyrene nanoplastics on the growth of zebrafish offspring

The coexistence of nanoplastics (NPs) and various pollutants in the environment has become a problem that cannot be ignored. In order to identify the microcystin-LR (MCLR) bioaccumulation and the potential impacts on the early growth of F1 zebrafish (Danio rerio) offspring in the presence of polystyrene nanoplastics (PSNPs), PSNPs and MCLR were used to expose adult zebrafish for 21days. The exposure groups divided into MCLR (0, 0.9, 4.5 and 22.5μgL^-1) alone groups and PSNP (100μgL^-1) and MCLR co-exposure groups. F1 embryos were collected and developed to 120 h post-fertilization (hpf) in clear water. Compared with the exposure to MCLR only, the combined exposure increased the parental transfer of MCLR to the offspring and subsequently exacerbated the growth inhibition of F1 larvae. Further research clarified that combined exposure of PSNPs and MCLR could reduce the levels of thyroxine (T4) and 3, 5, 3'-triiodothyronine (T3) by altering the expression of hypothalamus-pituitary-thyroid (HPT) axis-related genes, eventually leading to growth inhibition of F1 larvae. Our results also exhibited combined exposure of PSNPs and MCLR could change the transcription of key genes of the GH/IGF axis compared with MCLR single exposure, suggesting the GH/IGF axis was a potential target for the growth inhibition of F1 larvae in PSNPs and MCLR co-exposure groups. The present study highlights the potential risks of coexistence of MCLR and PSNPs on development of fish offspring, and the environmental risks to aquatic ecosystems.

Review of aquatic toxicity of pharmaceuticals and personal care products to algae

Pharmaceuticals and Personal Care Products (PPCPs) have been frequently detected in the environment around the world. Algae play a significant role in aquatic ecosystem, thus the influence on algae may affect the life of higher trophic organisms. This review provides a state-of-the-art overview of current research on the toxicity of PPCPs to algae. Nanoparticles, contained in personal care products, also have been considered as the ingredients of PPCPs. PPCPs could cause unexpected effects on algae and their communities. Chlorophyta and diatoms are more accessible and sensitive to PPCPs. Multiple algal endpoints should be considered to provide a complete evaluation on PPCPs toxicity. The toxicity of organic ingredients in PPCPs could be predicted through quantitative structure-activity relationship model, whereas the toxicity of nanoparticles could be predicted with limitations. Light irradiation can change the toxicity through affecting algae and PPCPs. pH and natural organic matter can affect the toxicity through changing the existence of PPCPs. For joint and tertiary toxicity, experiments could be conducted to reveal the toxic mechanism. For multiple compound mixture toxicity, concentration addition and independent addition models are preferred. However, there has no empirical models to study nanoparticle-contained mixture toxicity. Algae-based remediation is an emerging technology to prevent the release of PPCPs from water treatment plants. Although many individual algal species are identified for removing a few compounds from PPCPs, algal-bacterial photobioreactor is a preferable alternative, with higher chances for industrial applications.

Plastisphere enrich antibiotic resistance genes and potential pathogenic bacteria in sewage with pharmaceuticals

Microplastics (MPs) and pharmaceuticals are common emerging pollutants in sewage, and their coexistence may have more negative effects on the environments. This study chose tetracycline (TC), ampicillin (AMP) and triclosan (TCS) to investigate the responses of antibiotic resistance genes (ARGs) and microbial communities on different MPs (polyvinyl chloride (PVC), polyethylene (PE)) biofilms (plastisphere). The adsorption capacity of three pharmaceuticals on PVC and PE decreased in the order of AMP > TC > TCS. PE was more conducive to microbial attachment than PVC. MPs led to the increase of the total copies of ARGs and mobile genetic elements (MGEs) in the sewage. Importantly, multidrug ARGs and MGEs were enriched on plastisphere. Furthermore, the co-occurrence of TC and MPs led to higher risks of spreading ARGs and MGEs. In addition, potential pathogenic bacteria Legionella, Mycobacterium, Neisseria and Arcobacter were more abundant on plastisphere than those in sewage, and these bacteria might be the hosts for ARGs and MGEs. This study showed that plastisphere could be repositories of ARGs and MGEs in sewage and accumulated potential pathogenic bacteria.

Environmentally relevant concentrations and sizes of microplastic do not impede marine diatom growth

The current knowledge about the ecological effects of microplastic (MP) remains limited, and to-date ecotoxicity tests often utilize standard microplastic with one or two distinct size classes and expose the organisms to unrealistically high MP concentrations. We exposed the marine diatom Phaeodactylum tricornutum to microplastic particles of a mimicked realistic size frequency distribution complemented with serial experiments with distinct size classes. To do so, we exposed this diatom to a concentration series of different sized polyethylene (PE) microbeads (sizes: 10-106 µm; 1.25 ×10²-1.25 ×10⁷ particles/L) in a 72-h growth inhibition test. No effect on the growth of P. tricornutum by virgin PE microbeads up to 1.25 × 10⁷ particles/L (or 499 mg/L), indicating environmentally relevant concentrations and sizes of MP does not alter the growth of marine diatoms. Results of smaller sized MPs (10-20 µm) did not differ from those obtained with larger MPs (90-106 µm) and mix sized MPs (10-106 µm), i.e. no impact on the microalgae growth. As a pioneer work, our results contribute with high quality dose-response data to an improved risk assessment of microplastic under realistic present and future marine MP pollution.

A Critical Review on the Impacts of Nanoplastics and Microplastics on Aquatic and Terrestrial Photosynthetic Organisms

Microplastic and nanoplastic contamination is widespread and affects aquatic and terrestrial ecosystems. Photosynthetic organisms are present in both media, they are primary producers, sink for CO₂ , and they represent a major point of entry in the food chain. Here, the current knowledge on the fate and impacts of microplastics and nanoplastics in interaction with these organisms is reviewed. As a general trend, plastic characteristics (smaller size and positive charge) play a crucial role in their toxicity toward photosynthetic organisms. Plastic leachates (containing additives) also represent a major source of toxicity, and some harmful compounds such as phthalate esters are shown to accumulate in plants and generate a risk for the consumers. Adsorption of plastic particles is evidenced for each type of photosynthetic organism, and uptake and translocation in terrestrial plants is evidenced for nanoplastics, leading to concerns for trophic chain contamination. The available techniques for the detection of microplastics and nanoplastics and their secondary products in biological samples and media are also listed. Finally, the current gaps of knowledge, specific challenges, and future research directions are also discussed.

Exploring the multilevel effects of triclosan from development, reproduction to behavior using Drosophila melanogaster

Triclosan (TCS) is widely used as an antibacterial agent, but its residue in the environment poses a great threat. In this study, Drosophila melanogaster were treated with series concentrations of TCS and the effects on development, behavior, reproduction, and oxidative stress indicators were investigated. The results showed that high concentrations of TCS severely interfered with the metamorphosis, resulting in lower hatching rate and longer development time. The hatching rate was only 75.00% ± 4.08% in 0.80 mg/mL TCS group. TCS also showed dose-dependent damage to the fertility of flies, causing ovarian defects and decreased the number of offspring. Almost no offspring adults hatched when exposed to high concentrations of TCS (0.50 and 0.80 mg/mL), and the hatching rate was 0% in 0.80 mg/mL TCS group. Larvae crawling, adult climbing and anti-starvation ability were also affected to varying degrees and showed hormesis. TCS could damage larval intestinal cells in a dose-dependent manner, and injury was lightened with culture time prolonging to 30 h. It is noteworthy that TCS caused redox imbalance with an increase on catalase (CAT) activity and decrease on reactive oxygen species (ROS) level. Our results conclude that TCS elicits multiple impacts on Drosophila and its rational use should be strengthened.

Current understanding and challenges for aquatic primary producers in a world with rising micro- and nano-plastic levels

The impacts of micro- and nanoplastics (MNPs) on aquatic animals have been intensively studied; however, the extent and magnitude of potential effects of MNPs on aquatic primary producers are poorly understood. In this study, we quantitatively analyzed the published literature to examine the impacts of MNPs on growth, photosynthesis, pigments, and metabolism of aquatic microalgae. MNPs negatively affected growth of microalgae but usually had a high EC₅₀ (>25 mg/L). However, positively charged MNPs had a much lower EC₅₀ (<1 mg/L). MNPs lowered maximum photochemical efficiency of photosystem II (F_v/F_m) with the effect increasing with concentration of MNPs but diminishing with exposure time, and also reduced chlorophyll a content to enhanced extent with increased MNPs concentration. MNPs induced relatively higher changes in superoxide dismutase (SOD) and malondialdehyde (MDA) levels in marine algae than in freshwater algae. Reactive oxygen species (ROS) levels increased with MNPs concentration and exposure time while SOD levels first increased and then decreased with increasing MNPs concentration. Macrophytes were found to be able to trap MNPs via multiple mechanisms. Future work should focus on the mechanisms behind MNPs impacts on primary productivity and global carbon cycle, and the combined effects of MNPs with other environmental factors.

Microplastics and associated contaminants in the aquatic environment: A review on their ecotoxicological effects, trophic transfer, and potential impacts to human health

The microplastic pollution and related ecological impacts in the aquatic environment have attracted global attention over the past decade. Microplastics can be ingested by aquatic organisms from different trophic levels either directly or indirectly, and transferred along aquatic food chains, causing different impacts on life activities of aquatic organisms. In addition, microplastics can adsorb various environmental chemical contaminants and release toxic plastic additives, thereby serving as a sink and source of these associated chemical contaminants and potentially changing their toxicity, bioavailability, and fate. However, knowledge regarding the potential risks of microplastics and associated chemical contaminants (e.g., hydrophobic organic contaminants, heavy metals, plastic additives) on diverse organisms, especially top predators, remains to be explored. Herein, this review describes the effects of microplastics on typical aquatic organisms from different trophic levels, and systematically summarizes the combined effects of microplastics and associated contaminants on aquatic biota. Furthermore, we highlight the research progress on trophic transfer of microplastics and associated contaminants along aquatic food chain. Finally, potential human health concerns about microplastics via the food chain and dietary exposure are discussed. This work is expected to provide a meaningful perspective for better understanding the potential impacts of microplastics and associated contaminants on aquatic ecology and human health.

Toxicological interactions of microplastics/nanoplastics and environmental contaminants: Current knowledge and future perspectives

The co-occurrence of microplastics/nanoplastics (MPs/NPs) with other environmental contaminants has stimulated a focus shift of its skyrocketed research publications (more than 3000 papers during 2016-2020, Web of Science) from ubiquitous occurrence to interactive toxicity. Here, in this review, we provided the current state of knowledge on toxicological interaction of MPs/NPs with co-contaminants (heavy metals, polycyclic aromatic hydrocarbons, pharmaceuticals, pesticides, nanoparticles, organohalogens, plastic additives, and organotins). We discussed the possible interactions (aggregation, adsorption, accumulation, transformation, desorption) that played a role in influencing the toxicity of the mixture. Besides, the type of interactions such as synergistic, antagonistic, potentiating was expounded to get a deeper mechanistic understanding. Despite the wide occurrence and usage, scant studies were available on polypropylene, polyethylene terephthalate. Our analysis shows a dearth of research on common occurring heavy metals (mercury, lead, chromium), phthalates, personal care products. Considerations for environmental factors such as the presence of dissolved organic matter, pH, salinity, temperature, and effects of different colors and types of polymer are recommended.

Microplastics can act as vector of the biocide triclosan exerting damage to freshwater microalgae

Despite the large number of recent studies on microplastics (MPs) and their ability to act as carriers of pollutants, the knowledge about the biological effects of MPs loaded with chemicals is scarce. The aim of this study was to evaluate the potential of MPs as vectors for the antimicrobial triclosan (TCS). For it, we tested low-density polyethylene (LDPE), polyamide (PA), polyethylene terephthalate (PET), polyoxymethylene (POM), polypropylene (PP), polystyrene (PS) and the biodegradable polylactic acid (PLA). Thus, chemical analysis of sorption and desorption of TCS by these MPs was evaluated. The effect of TCS-loaded MPs to Anabaena sp. PCC7120, a cyanobacterium model of primary producers in freshwater ecosystems, was investigated. Chemical analyses showed different capacity of sorption depending on the MP type, which was related to some of their physicochemical properties. PA (104.7 μg/g), POM (57.4 μg/g) and LDPE (18.3 μg/g) were the polymers that sorbed the highest amounts of TCS. Glass transition temperature of polymers and their physicochemical interaction with TCS explained the extent of sorption. Significant decreases were found in growth, 22.3%, 94.6% and 81.0%, and chlorophyll a content, 58.4%, 95.0% and 89.6%, of Anabaena when exposed to TCS-loaded LDPE, PA and POM beads, respectively, which were the only MPs displaying significant sorption-desorption of TCS, implying that these MPs could act as vectors of TCS towards freshwater microalgae. This finding is of fundamental relevance as microalgae are at the base of the aquatic trophic chain and support growth of upper organisms.

Interactive effects of micro/nanoplastics and nanomaterials/pharmaceuticals: Their ecotoxicological consequences in the aquatic systems

Micro/nanoplastics are ubiquitous in the environment and cause pollution of the aquatic ecosystem, in particular, which is a serious concern worldwide. Micro/nanoplastics can act as a vector for multiple co-contaminants that co-exist in the aquatic environment. Apart from micro/nanoplastics, nanomaterials and pharmaceuticals are other emerging contaminants that can also raise severe problems. Thus, in this review, the physicochemical interactions occurring between micro/nanoplastics and nanomaterials and pharmaceuticals and the factors (chemical and environmental) affecting the sorption efficiency of nanomaterials and pharmaceuticals have been addressed. Furthermore, the influence of micro/nanoplastics on the bioavailability and toxic effects of nanomaterials and pharmaceuticals on both freshwater and marine species has been highlighted. Additional focus has also been given to study the mechanism of toxicity of the micro/nanoplastics-nanomaterials and pharmaceuticals complex on the different species of different trophic levels. Finally, this review addresses the knowledge gaps and provides insights into the future research strategies to better understand the interactive mechanisms between the binary contaminants and also the toxicity mechanisms of micro/nanoplastics and nanomaterials and pharmaceuticals.

A review of microplastics aggregation in aquatic environment: Influence factors, analytical methods, and environmental implications

A large amount of plastic waste released into natural waters and their demonstrated toxicity have made the transformation of microplastics (MPs; < 5 mm) and nanoplastics (NPs; < 100 nm) an emerging environmental concern. Aggregation is one of the most important environmental behaviors of MPs, especially in aquatic environments, which determines the mobility, distribution and bioavailability of MPs. In this paper, the sources and inputs of MPs in aquatic environments were first summarized followed by the analytical methods for investigating MP aggregation, including the sampling, visualization, and quantification procedures of MP' particle sizes. We critically evaluated the sampling methods that still remains a methodological gap. Identification and quantification of MPs were mostly carried out by visual, spectroscopic and spectrometric techniques, and modeling analysis. Important factors affecting MP aggregation in natural waters and environmental implications of the aggregation process were also reviewed. Finally, recommendations for future research were discussed, including (1) conducting more field studies; (2) using MPs in laboratory works representing those in the environment; and (3) standardizing methods of identification and quantification. The review gives a comprehensive overview of current knowledge for MP aggregation in natural waters, identifies knowledge gaps, and provides suggestions for future research.

The influence of different polymer types of microplastics on adsorption, accumulation, and toxicity of triclosan in zebrafish

Although the combined effects of microplastics (MPs) and other organic pollutants have raised increasing attention, the impacts of polymer types on the biological effects (e.g., bioaccumulation and toxicity) of the mixtures are still unclear. This study aimed to evaluate the influence of different polymer types of MPs including polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) on the adsorption, accumulation, and toxic effects of triclosan (TCS) in zebrafish. As a result, all three types of MPs could adsorb TCS and PP-MPs has the highest adsorption capacity for TCS (1.18 mg/g). Compared with the TCS alone, MPs changed the distribution of TCS in tissues and increased the accumulation of TCS in the liver and gut following the order of TCS + PP > TCS + PVC > TCS + PE. Compared with individual TCS and PP-MPs, after co-exposed for 28 days, TCS + PP significantly aggravated oxidative stress and lipid peroxidation in the liver as well as enhanced neurotoxicity in the brain. Moreover, TCS + PP disturbed the metabolism in the liver and MPs contributed more to the metabolic disorders. The upregulated lipid metabolites (e.g., sphingosine and L-palmitoylcarnitine) and downregulated carbohydrate metabolites (e.g., sucrose) could be potential targets for future risk assessment of MPs combined with other pollutants.

Growth inhibition, toxin production and oxidative stress caused by three microplastics in Microcystis aeruginosa

Microplastics (MPs) have aroused widespread concern due to their extensive distribution in aquatic environments and adverse effects on aquatic organisms. However, the underlying toxicity of different kinds of MPs on freshwater microalgae has not been examined in detail. In this study, we investigated the effects of polyvinyl chloride (PVC), polystyrene (PS) and polyethylene (PE) MPs on the growth of Microcystis aeruginosa, as well as on its toxin production and oxidative stress. We found that all three kinds of MPs had an obvious inhibition effect on the growth of M. aeruginosa. Considering the results of antioxidant-related indicators, the activity of superoxide dismutase (SOD) and catalase (CAT), and cell membrane integrity were greatly affected with exposure to PVC, PS and PE MPs. Moreover, the content of intracellular (intra-) and extracellular (extra-) microcystins (MCs) had a noticeable increase due to the presence of PVC, PS, and PE MPs. Finally, according to the comprehensive stress resistance indicators, the resistance of M. aeruginosa to three MPs followed the order: PE (3.701)> PS (3.607)> PVC (2.901). Our results provide insights into the effects of different kinds of MPs on freshwater algae and provide valuable data for risk assessment of different types of MPs.

Effect of polyethylene particles on dibutyl phthalate toxicity in lettuce (Lactuca sativa L.)

The effects of dibutyl phthalate (DBP) on the toxicity and edible quality (e.g., soluble proteins, soluble sugars, and vitamin C) of green and purple lettuce in the presence of polyethylene (PE) fragments were evaluated. The results revealed that PE treatment for 28 days decreased DBP and monobutyl phthalate content in lettuce roots and leaves, but enhanced the inhibitory effects of DBP on root growth and activity, reduced soluble protein and sugar content in lettuce leaves, and increased vitamin C content in lettuce leaves. Scanning and transmission electron microscopies revealed that PE only adhered to the root surface and did not enter the lettuce roots. Moreover, separation of the cell wall was aggravated in lettuce roots treated with DBP+PE, but not in lettuce treated with individual DBP or PE, and even led to the expansion of endoplasmic reticulum vesicles and cell rupture. Gaussian analysis indicated that PE interacted with DBP molecules through van der Waals interactions, which decreased DBP transport from the culture solution into the lettuce roots. In addition, purple lettuce was more sensitive to exogenous pollutants than green lettuce. This study provides new insights for food safety related to DBP fate and toxicity under PE stress.

Aggregation and stability of sulfate-modified polystyrene nanoplastics in synthetic and natural waters

Nanoplastics (NPs) are becoming emerging pollutants of global concern. Understanding the environmental behavior of NPs is crucial for their environmental and human risk assessment. In this study, the aggregation and stability of polystyrene (PS) NPs were investigated under different hydrochemical conditions such as pH, salt type (NaCl, CaCl₂, Na₂SO₄), ionic strength (IS), and natural organic matter (NOM). The critical coagulation concentrations of PS NPs were determined to be 158.7 mM NaCl, 12.2 mM CaCl₂, and 80.0 mM Na₂SO₄. Ca²⁺ was more effective in destabilizing PS NPs, compared to Na⁺, owing to its stronger charge screening effect. In the presence of monovalent ions, NOM reduced aggregation through steric repulsion, whereas in the case of divalent ions, NOM induced aggregation through cation bridging. Initial and long-term stability studies demonstrated that, in waters with high IS and NOM content, NOM was the most significant factor affecting NPs aggregation. PS NPs would be highly suspended in all freshwaters, and even in wastewater, whereas they would aggregate rapidly and deposit in seawater. Finally, a statistical model was established to evaluate the hydrodynamic diameter of NPs in different waters. The results indicated the stability of PS NPs in natural aquatic environments and their potential for long-term transport.

A critical review of interactions between microplastics, microalgae and aquatic ecosystem function

With the widespread occurrence of microplastics in aquatic ecosystems having been firmly established, the focus of research has shifted towards the assessments of their influence on ecosystem functions and food webs. This includes interactions between microplastics and microalgae, as fundamental components at the base of aquatic food webs and pivotal organisms in a wide range of ecosystem functions. In this review, we present the current state of knowledge on microalgae-microplastic interactions and summarize the potential effect on their respective fate. Microplastics can and do interact with microalgae and the available literature has suggested that the epiplastic community of microalgae differs consistently from the surrounding aquatic communities; however, it is still not clear whether this different colonization is linked to the composition of the surface or more to the availability of a "hard" substrate on which organisms can attach and grow. Further studies are needed to understand to what extent the properties of different plastic materials and different environmental factors may affect the growth of microalgae on plastic debris. Biofouling may alter microplastic properties, especially increasing their density, consequently affecting the vertical fluxes of plastics. Moreover, microplastics may have toxic effects on microalgae, which could be physical or related to chemical interactions with plasticizers or other chemicals associated with plastics, with consequences for algal growth, photosynthetic activity, and morphology. Microplastics seems to have the potential to affect not only the quality (e.g., fatty acids and lipids composition, food dilution effect) but also the quantity of algal production, both positively and negatively. This may have consequences for energy fluxes, which may propagate throughout the whole food web and alter aquatic productivity. Even though experimental results have indicated reciprocal impacts between plastics and microalgae, it is currently difficult to predict how these impacts may manifest themselves at the ecosystem level. Therefore, further studies are needed to address this important topic.

The toxicity of virgin and UV-aged PVC microplastics on the growth of freshwater algae Chlamydomonas reinhardtii

Although more attention has been paid to plastic pollution in marine ecosystems, research on the influence of plastic in freshwater ecosystems remains limited. To help fill this information gap, this article represents an investigation of the effects of virgin polyvinyl chloride (v-PVC) microplastics (MPs) and UV-aged polyvinyl chloride (a-PVC) MPs on the growth and chlorophyll content of the freshwater algae, Chlamydomonas reinhardtii (C. reinhardtii) at different periods (0, 24, 48, 72 and 96 h). The results suggest that both virgin and aged PVC MPs have negative effects on the growth of C. reinhardtii in the range of 10 mg/L to 200 mg/L, which leads to the reduction of chlorophyll-a level in the cells. Furthermore, a-PVC MPs were more toxic than v-PVC MPs, as shown by the a-PVC MPs' lower EC₅₀ values after 96 h (63.66 mg/L for a-PVC MPs and 104.93 mg/L for v-PVC MPs). The inhibition effect of both kinds of PVC was also testified by the enhancement of enzymatic activity of superoxide dismutase (SOD) and malondialdehyde (MDA) in algae. Meanwhile, a-PVC MPs obviously had a higher toxicity than v-PVC MPs. The aging process that affected the surface characteristics of a-PVC was identified using Fourier transform infrared (FTIR) and Zetasizer. The carbonyl groups formed on the surface and the increased zeta potential of the a-PVC MPs affected the interaction between the microplastics and the algae, which increased the toxicity of aged microplastics. The research results presented here provide more evidence of the risks microplastics bring into the freshwater ecosystem.

Global trends and prospects in microplastics research: A bibliometric analysis

Microplastic pollution is a global enviromental issues. This is the first time in recent decades that quantitative and qualitative evidence from bibliometrics and Altmetric has been used to conduct an in-depth statistical analysis of global microplastics research knowledge and demonstrate research progress, trends and hotspots. We comprehensively searched the Web of Science Core Collection scientific database from its inception (1986) to September 21, 2019. The study shown that the number of papers on microplastics has increased significantly since 2011. Worldwide, researchers in the field come mostly from Western Europe, mainly spread in the UK, Netherlands and Belgium. With the exception of China, the contribution of developing countries was very limited. Moreover, this study systematically elaborated the hotspots in this field (especially in ecological toxicity and human health risks). The results shown that research on marine systems and marine plankton is still dominant. Since human beings are the ultimate consumers of the food chain, microplastics may have potential effects on the human respiratory system and gastrointestinal tract. Towards that end, some topics and perspectives are noted that could indicate the current scientific hotspots and guide future research directions.

Risks of floating microplastic in the global ocean

Despite the ubiquitous and persistent presence of microplastic (MP) in marine ecosystems, knowledge of its potential harmful ecological effects is low. In this work, we assessed the risk of floating MP (1 μm-5 mm) to marine ecosystems by comparing ambient concentrations in the global ocean with available ecotoxicity data. The integration of twenty-three species-specific effect threshold concentration data in a species sensitivity distribution yielded a median unacceptable level of 1.21 ∗ 10⁵ MP m^-³ (95% CI: 7.99 ∗ 10³-1.49 ∗ 10⁶ MP m^-³). We found that in 2010 for 0.17% of the surface layer (0-5 m) of the global ocean a threatening risk would occur. By 2050 and 2100, this fraction increases to 0.52% and 1.62%, respectively, according to the worst-case predicted future plastic discharge into the ocean. Our results reveal a spatial and multidecadal variability of MP-related risk at the global ocean surface. For example, we have identified the Mediterranean Sea and the Yellow Sea as hotspots of marine microplastic risks already now and even more pronounced in future decades.

Microplastics in the environment: Interactions with microbes and chemical contaminants

Microplastics (MPs) are contaminants of emerging concern that have gained considerable attention during the last few decades due to their adverse impact on living organisms and the environment. Recent studies have shown their ubiquitous presence in the environment including the atmosphere, soil, and water. Though several reviews have focused on the occurrence of microplastics in different habitats, little attention has been paid to their interaction with biological and chemical pollutants in the environment. This review therefore presents the state of knowledge on the interaction of MPs with chemicals and microbes in different environments. The distribution of MPs, the association of toxic chemicals with MPs, microbial association with MPs and the microbial-induced fate of MPs in the environment are discussed. The biodegradation and bioaccumulation of MPs by and in microbes and its potential impact on the food chain are also reviewed. The mechanisms driving these interactions and how these, in turn, affect living organisms however are not yet fully understood and require further attention.

Co-occurrence of microplastics and triclosan inhibited nitrification function and enriched antibiotic resistance genes in nitrifying sludge

As more and more microplastics (MPs) and triclosan (TCS), which are added in consumer products, enter wastewater treatment plants with sewage, there are concerns about the impacts of the co-occurrence of MPs and TCS on biological wastewater treatment. In this study, the co-effects of four 1 mg/L MPs (polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC) and polyamide (PA)) and 0.5 mg/L TCS on nitrification were investigated in lab-scale nitrifying sequencing batch reactors (SBRs) (SBR-PE, SBR-PS, SBR-PVC and SBR-PA) relative to control which received no MPs (SBR-CK). The removal rates of NH₄⁺-N and TCS in SBR-CK were around 100% and 92%, respectively. Compared with SBR-CK, no measurable inhibition was observed on nitrification in SBR-PE and SBR-PS, however, SBR-PVC and SBR-PA rapidly lost nitrification function during 14 days, which might be due to the reducing of MLSS caused by PVC, PA and TCS co-loading. Furthermore, PS, PVC and PA decreased the removal of TCS. The co-occurrence of TCS and PS, PVC, PA increased extracellular polymeric substances, reduced microbial diversity and shifted microbial communities. Notably, the acrA-03, mexF, fabI, intI1, intI3 and IS613 genes were enriched by MPs and TCS co-loading. Therefore, the removal of MPs and TCS from wastewater should be prioritized.

The impacts of polyethylene terephthalate microplastics (mPETs) on ecosystem functionality in marine sediment

The effects of microplastics (MPs) on the ecological functioning in marine sediments is largely unknown. However, coastal marine sediments and their resident communities play critical roles in the transformation of organic matter and the cycling of nutrients that influence both local and global processes. To investigate how microplastics influence ecosystem functions associated with sediment biogeochemistry, large bivalves and microphytobenthos, we conducted a 31-day laboratory experiment. The experiment tested the role of micro-polyethylene terephthalate (mPETs) at five concentrations (0%, 1%, 3%, 6%, and 8% based on wet weight of top 1 cm sediment). Canonical principle of coordinate analysis (CAP) was applied to assess change on the ecosystem functionality with increasing concentrations of mPETs. Our results highlight that stress effects on ecosystem function are the product of the interaction between Macomona liliana, microphytobenthos and mPETs.

Microplastic pollution research methodologies, abundance, characteristics and risk assessments for aquatic biota in China

The widespread presence of microplastics in global aquatic ecosystems has aroused growing concern about the potential impacts of microplastics on aquatic biota. In marine and freshwater environments, microplastics are distributed pervasively within water bodies from the upper water column to the bottom layer, making them available to a large variety of aquatic organisms that inhabit different locations. The ingestion of microplastic particles may cause harm to aquatic organisms. Although China's aquatic environments have been seriously polluted by microplastics, the impacts of microplastics on aquatic biota remain to be elucidated. This review summarizes the current state of knowledge about microplastic pollution in aquatic biota in China; specifically, the concentration and characteristics of microplastic particles in aquatic organisms from both seawater and freshwater environments are discussed. The results showed that various aquatic organisms in China have been found to consume microplastics. The average number of microplastic pieces discovered in biota ranged from 0.07 particles to 164 particles per individual in different organisms. The most frequently observed colors of microplastics detected in biota were blue and transparent, and the detected microplastics mainly consisted of fibers. In addition, the impacts of microplastics on aquatic organisms, including physical impacts, chemical impacts, the trophic transfer of microplastics and the potential risks to humans, were discussed. Finally, knowledge gaps were identified in order to guide future studies.

Interfacial interaction between micro/nanoplastics and typical PPCPs and nanoplastics removal via electrosorption from an aqueous solution

Micro/nanoplastics have raised worldwide concern with extensive research on its transfer, toxicity and removal. However, the primary environmental process-adsorption of nanoplastics has not been uncovered since the discovery of nanosized plastics. Here, we synthesized nanoscale polystyrene (PS) particles with mean diameter of ∼40 nm to avoid unknown properties from purchased ones, and thoroughly investigated its adsorption towards two typical pharmaceuticals and personal care products (PPCPs) with distinct characteristics, which are antibiotic (ciprofloxacin) and endocrine disruptor (bisphenol-A). Moreover, UV radiation is applied to simulate aging process in natural cases, and the carbonyl index derived from FTIR spectra increased clearly from 0.183 to 0.387. The adsorption capacity at equilibrium of CIP and BPA increased from 0.15 to 4.07 to 4.92 and 8.71 mg/g after weathering, respectively. Besides, the effect of environmental factors (pH, humic acid, salinity and cations) was also studied. Furthermore, electrosorption technology is applied to remove nanoplastics in solution for the first time, with the capacity of 0.707 g nano-polystyrene/g AC and 0.322 g aged-nano-polystyrene/g AC, suggesting that adsorption under electric field is presumably a feasible tertiary treatment method targeted at nanoplastics in wastewater treatment plants (WWTPs).

Microplastics combined with tetracycline in soils facilitate the formation of antibiotic resistance in the Enchytraeus crypticus microbiome

Growing evidence suggests that microplastics can adsorb antibiotics and may consequently exacerbate effects on the health of exposed organisms. Our current understanding of the combined effects of microplastics and antibiotics on antibiotic resistance genes (ARGs) in soil invertebrates is limited. This study aimed to investigate changes in the microbiome and ARGs in Enchytraeus crypticus following exposure to a soil environment that contained both microplastics and antibiotics. Tetracycline (TC), polyamide (PA) and polyvinyl chloride (PVC) were used to construct microcosms of polluted soil environments (TC, PA, PVC, PA+TC, PVC+TC). The differences in microbiomes and ARGs were determined by bacterial 16S rRNA gene amplicon sequencing and high throughput quantitative PCR. The results show that compared with the Control or microplastics alone treatments, TC was significantly accumulated in E. crypticus when exposed to TC alone or in combination with microplastics (P < 0.05), but there were no significant differences about TC accumulation between TC, PA+TC, and PVC+TC treated E. crypticus (P > 0.05). Microplastics and TC significantly disturbed the microbial community, and decreased the microbial alpha diversity of E. crypticus (P < 0.05). However, there were no significant differences between TC, microplastics and their combined exposure treatments, and no toxic synergies on the diversity of E. crypticus microbiome between tetracycline and microplastics in soil environment. All the treatments increased the diversity of ARGs in E. crypticus (39-49 ARGs vs. 25 ARGs of control). In particular, treatments combining PVC and TC or PA and TC exposure resulted in greater ARGs abundance than the treatments when E. crypticus was exposed to PVC, PA or TC alone. These results add to our understanding of the combined effects of microplastics and antibiotics on the ARGs and microbiome of soil invertebrates.

Behavior of tetracycline and polystyrene nanoparticles in estuaries and their joint toxicity on marine microalgae Skeletonema costatum

Polystyrene nanoplastics (PS NPs), which are newly emerging as particulate pollutants, are one of the most abundant plastic types in marine debris. Although there has been extensive research on microplastics, the sorption behavior of PS NPs in surface waters remains unknown. In addition, in the previous joint toxicity studies, the concentration of organic pollutant in the joint system was based on the EC₅₀ of this pollutant, rather than the actually amount of this pollutant adsorbed on nanoplastics (NPs). In this study, the sorption behavior of PS NPs with different surface charges in the surface water of estuaries and joint toxicity of that absorbed tetracycline antibiotic in equilibrium were investigated for the first time. Because of the electrostatic repulsion, salting-out effect, and partition function, the sorption capacity of tetracycline antibiotic by differently charged PS NPs was enhanced with increasing salinity. The biological effects of exposure to tetracycline-saturated PS NPs were complicated, which can be attributed to the surface characteristics of mixtures such as hydrophobicity and charges. Thus, the role of NPs in the natural environment as a carrier of antibiotics may provide an alternative for antibiotic inputs from inland water to coastal marine water, which would not only change the environmental fate and ecotoxicology of antibiotics and NPs, but also pose challenges to the safety of coastal aquaculture and marine ecosystem.

The influence of nanoplastics on the toxic effects, bioaccumulation, biodegradation and enantioselectivity of ibuprofen in freshwater algae Chlorella pyrenoidosa

Plastic pollution has become a pressing issue due to its persistence in the environment. Smaller plastics are more easily ingested, potentially exerting greater influences on organisms. In this study, the effects of polystyrene nanoplastics (NP) on the toxic effects, bioaccumulation, biodegradation and enantioselectivity of ibuprofen (IBU) in algae Chlorella pyrenoidosa were explored. The influences on the growth rate, chlorophyll a, total antioxidant capacity (T-AOC), reactive oxygen species (ROS) and lipid peroxidation (MDA) were evaluated after 96 h of exposure to a combination of polystryene NP (1 mg L^-1) and IBU (5-100 mg L^-1). The results indicated that the inhibitory effect of IBU on C. pyrenoidosa growth was alleviated in the presence of NP. For instance, the 96 h-IC₅₀ value for rac-IBU in the treatment lacking NP was 45.7 mg L^-1, and the corresponding value in the treatment containing NP was 63.9 mg L^-1. The co-exposure of NP led to a significant enhancement of T-AOC and slight reduction of ROS and MDA compared with the individual exposure (IBU) group, suggesting a decreased oxidative stress. In addition, treatment with NP led to a decreased bioaccumulation and accelerated biodegradation of IBU in C. pyrenoidosa and enhanced removal in the medium. The enantioselective toxicity, bioaccumulation and biodegradation of IBU were observed both in the absence and presence of NP. S-IBU exhibited a greater toxicity, and R-IBU was preferentially accumulated and degraded in C. pyrenoidosa. No interconversion of the two enantiomers occurred regardless of the presence of NP. This consequence implied that the influence of coexistent NP should be considered in the environmental risk assessment of pharmaceuticals and personal care products in aquatic environments.

Identifying alternative solvents for C60 manufacturing using singular and combined toxicity assessments

Linseed oil, olive oil, and sunflower oil were selected based on green chemistry principles and C₆₀ solubility as alternative solvents to replace 1,2,4-trimethylbenzene (TMB) for C₆₀ manufacturing. Singular acute toxicity experiments of C₆₀ and the four solvents was performed using Daphnia magna to identify the solvent with the lowest toxicity and estimate the toxicity of C₆₀. The EC₅₀ for C₆₀ was estimated to be higher than 176 ppm. The toxicity of the solvents increased from sunflower oil to olive oil, linseed oil, and TMB. Combined toxicity tests were conducted to investigate the interaction between C₆₀ and the solvent since essential oils can be nanocarriers and facilitate the transport of C₆₀ into the cell membranes, which would increase its toxicity. Various concentrations of C₆₀ (0, 11, 22, 44, 88, and 176 mg/L) were mixed with solvents at their EC₅₀ concentrations. The toxicity of linseed oil increased with increasing C₆₀ concentrations. For olive and sunflower oil, the toxicity was lowered with low concentrations of C₆₀. Olive oil was determined to be a suitable solvent for C₆₀ manufacturing based on singular and combined toxicity assessments. This study showed the importance of considering combined toxicity for solvent selection.