The effects of high-density polyethylene and polypropylene microplastics on the soil and earthworm Metaphire guillelmi gut microbiota

A critical review of co-pollution of microplastics and heavy metals in agricultural soil environments

The soil environment is a primary destination for contaminants such as microplastics (MPs) and heavy metals (HMs), which are frequently detected simultaneously. The long-term coexistence of MPs and HMs in the soil necessitates unavoidable interactions, affecting their environmental chemical behavior and bioavailability. These co-contaminants pose potential threats to soil organism growth and reproduction, crop productivity, food security, and may jeopardize human health via the food chain. This paper summarizes the sources and trends of MPs in the soil environment, along with the mechanisms and current research status of MP adsorption or desorption of HMs. Additionally, this paper reviews factors affecting HM adsorption on MPs, including MP properties, HM chemical properties, and other environmental factors. Lastly, the effects of MPs and HMs on soil ecology and human health are summarized. The interaction mechanisms and potential biological effects of their co-contamination require further exploration. Future research should delve deeper into the ecotoxic effects of MP-HM co-contamination at cellular and molecular levels, to provide a comprehensive reference for understanding the environmental behavior of their co-contamination in soil.

High-density polyethylene microplastics in agricultural soil: Impact on microbes, enzymes, and carbon-nitrogen ratio

Microplastics (MPs), recognized as emerging pollutants, pose a significant threat to diverse organisms and have adverse effects on agricultural soil. High-density polyethylene (HDPE) holds a prominent position among prevalent forms of MPs. In the current investigations, the impact of HDPE was assessed at four different concentrations (0.25%, 0.5%, 0.75%, and 1.0%) on agricultural soil, microbial population, exoenzymes activities including amylase, cellulase, and invertase, and alteration in carbon-to-nitrogen (C/N) ratio. Both bacterial and fungal populations exhibited a non-concentration-dependent response to different concentrations of HDPE over time. In this study, we refer to the concentrations of 0.25%, 0.5%, 0.75%, and 1.0% as HT1, HT2, HT3, and HT4, respectively. Initial MP application significantly reduced bacterial colony counts for HT1, HT2, and HT4, while HT3 showed no significant change. On the 60th day, HT1 and HT3 exhibited a higher bacterial colony count compared to the control. On the other hand, fungal populations increased to maximum on day 1 but displayed no distinct time-dependent trend from days 15 to 60. Furthermore, enzyme activities decreased with increasing concentrations of MPs over an extended period. Molecular docking studies suggest that HDPE can hinder enzyme activity by forming hydrogen bonds with enzymes. The C/N ratio was found to be significantly higher in MP-treated soils on the 60th day relative to control, suggesting relatively slower degradation of carbon compounds in the MP-treated soils.

Exposure to polyethylene microplastics exacerbate inflammatory bowel disease tightly associated with intestinal gut microflora

Polyethylene microplastics (PE MPs) have sparked widespread concern about their possible health implications because of their abundance, pervasiveness in the environment and in our daily life. Multiple investigations have shown that a high dosage of PE MPs may adversely impact gastrointestinal health. In tandem with the rising prevalence of Inflammatory bowel disease (IBD) in recent decades, global plastic manufacturing has risen to more than 300 million tons per year, resulting in a build-up of plastic by-products such as PE MPs in our surroundings. We have explored current advancements in the effect PE MPs on IBD in this review. Furthermore, we compared and summarized the detrimental roles of PE MPs in gut microbiota of different organisms viz., earthworms, super worm's larvae, yellow mealworms, brine shrimp, spring tails, tilapia, gilt-head bream, crucian carp, zebrafish, juvenile yellow perch, European sea bass, c57BL/6 mice and human. According to this review, PE MPs played a significant role in decreasing the diversity of gut microbiota of above-mentioned species which leads to the development of IBD and causes severe intestinal inflammation. Finally, we pinpoint significant scientific gaps, such as the movement of such hazardous PE MPs and the accompanying microbial ecosystems and propose prospective research directions.

COVID-19 pandemic-related drugs and microplastics from mask fibers jointly affect soil functions and processes

The COVID-19 pandemic has led to an unprecedented increase in pharmaceutical drug consumption and plastic waste disposal from personal protective equipment. Most drugs consumed during the COVID-19 pandemic were used to treat other human and animal diseases. Hence, their nearly ubiquitous presence in the soil and the sharp increase in the last 3 years led us to investigate their potential impact on the environment. Similarly, the compulsory use of face masks has led to an enormous amount of plastic waste. Our study aims to investigate the combined effects of COVID-19 drugs and microplastics from FFP2 face masks on important soil processes using soil microcosm experiments. We used three null models (additive, multiplicative, and dominative models) to indicate potential interactions among different pharmaceutical drugs and mask MP. We found that the multiple-factor treatments tend to affect soil respiration and FDA hydrolysis more strongly than the individual treatments. We also found that mask microplastics when combined with pharmaceuticals caused greater negative effects on soil. Additionally, null model predictions show that combinations of high concentrations of pharmaceuticals and mask MP have antagonistic interactions on soil enzyme activities, while the joint effects of low concentrations of pharmaceuticals (with or without MP) on soil enzyme activities are mostly explained by null model predictions. Our study underscores the need for more attention on the environmental side effects of pharmaceutical contamination and their potential interactions with other anthropogenic global change factors.

Insights into tolerance mechanisms of earthworms (Eisenia fetida) in copper-contaminated soils by integrating multi-omics analyses

Earthworms can resist high levels of soil copper (Cu) contamination and play an essential role in absorbing them effectively. However, the molecular mechanisms underlying Cu tolerance in earthworms are poorly understood. To address this research gap, we studied alterations of Eisenia fetida in antioxidant enzymes, gut microbiota, metabolites, and genes under varying levels of Cu exposure soils (0, 67.58, 168.96, 337.92 mg/kg). Our results revealed a reduction in antioxidant enzyme activities across all treatment groups, indicating an adaptive response to alleviate Cu-induced oxidative stress. Analysis of gut microbiota revealed a significant increase in the abundance of bacteria associated with nutrient uptake and Cu2+ excretion under Cu stress. Furthermore, metabolomic analysis discovered an increase in certain metabolites associated with energy metabolism, such as pyruvic acid, L-malic acid, and fumaric acid, as Cu concentration escalated. These results suggested that enhanced energy supply contributes to the elevated tolerance of E. fetida towards Cu. Additionally, transcriptome analysis not only identified crucial detoxification genes (Hsp70, CTSL, GST, CHAC, and GCLC), but also confirmed the critical role of glutathione metabolism as a key pathway in E. fetida Cu detoxification processes. These findings provide a new perspective on the molecular mechanisms of Cu tolerance in earthworms.

Discrepant soil microbial community and C cycling function responses to conventional and biodegradable microplastics

Biodegradable microplastics (MPs) are promising alternatives to conventional MPs and are of high global concern. However, their discrepant effects on soil microorganisms and functions are poorly understood. In this study, polyethylene (PE) and polylactic acid (PLA) MPs were selected to investigate the different effects on soil microbiome and C-cycling genes using high-throughput sequencing and real-time quantitative PCR, as well as the morphology and functional group changes of MPs, using scanning electron microscopy and Fourier transform infrared spectroscopy, and the driving factors were identified. The results showed that distinct taxa with potential for MP degradation and nitrogen cycling were enriched in soils with PLA and PE, respectively. PLA, smaller size (150-180 µm), and 5% (w/w) of MPs enhanced the network complexity compared with PE, larger size (250-300 µm), and 1% (w/w) of MPs, respectively. PLA increased β-glucosidase by up to 2.53 times, while PE (150-180 µm) reduced by 38.26-44.01% and PE (250-300 µm) increased by 19.00-22.51% at 30 days. Amylase was increased by up to 5.83 times by PLA (150-180 µm) but reduced by 40.26-62.96% by PLA (250-300 µm) and 16.11-43.92% by PE. The genes cbbL, cbhI, abfA, and Lac were enhanced by 37.16%- 1.99 times, 46.35%- 26.46 times, 8.41%- 69.04%, and 90.81%- 5.85 times by PLA except for PLA1B/5B at 30 days. These effects were associated with soil pH, NO3--N, and MP biodegradability. These findings systematically provide an understanding of the impact of biodegradable MPs on the potential for global climate change.

Response of the terrestrial isopod Porcellio scaber to lipopolysaccharide challenge after microplastic and insecticide exposure

The exposure of organisms to microplastics could compromise their ability to cope with other environmental stressors, such as infections. In this context, we investigated the effects of a 14-day exposure of the terrestrial isopod Porcellio scaber to tire particles in soil (1.5 % w w-1 dry weight) on the organisms' response to a secondary exposure, i.e., injection of the bacterial endotoxin lipopolysaccharide. In addition, the insecticide chlorpyrifos (2 mg kg-1 dry weight) was tested as a positive control. The survival and immune response of P. scaber was assessed at the end of the 7- and 14-day primary exposure and two days after the secondary exposure, by analyzing selected haemolymph immune parameters (total haemocyte count, differential haemocyte count, and haemocyte viability). No change in survival was observed after primary exposure of P. scaber to tire particles or chlorpyrifos. However, primary exposure to chlorpyrifos triggered a strong activation of the immune response, which was not the case following exposure to the tire particles. Further injection of lipopolysaccharide into the body did not affect the survival of animals exposed to tire particles or chlorpyrifos, while a strong immunomodulatory change was observed, particularly with chlorpyrifos, and to some extent, tire particles. Based on these results, we conclude that exposure of P. scaber to tire particles or chlorpyrifos has no significant effect on the susceptibility of the organism to lipopolysaccharide in terms of their mortality, but primary exposure to an insecticide significantly modulates the immune response of the organisms to a second stressor. We discuss the "stress on stress" approach for testing low-toxic substances, such as microplastics, where an environmentally realistic exposure is followed by a secondary exposure.

Effects of farmland residual mulch film-derived microplastics on the structure and function of soil and earthworm Metaphire guillelmi gut microbiota

Microplastics derived from polyethylene (PE) mulch films are widely found in farmland soils and present considerable potential threats to agricultural soil ecosystems. However, the influence of microplastics derived from PE mulch films, especially those derived from farmland residual PE mulch films, on soil ecosystems remains unclear. In this study, we analyzed the bacterial communities attached to farmland residual transparent PE mulch film (FRMF) collected from peanut fields and the different ecological effects of unused PE mulch film-derived microplastics (MPs) and FRMF-derived microplastics (MPs-aged) on the soil and earthworm Metaphire guillelmi gut microbiota, functional traits, and co-occurrence patterns. The results showed that the assembly and functional patterns of the bacterial communities attached to the FRMF were clearly distinct from those in the surrounding farmland soil, and the FRMF enriched some potential plastic-degrading and pathogenic bacteria, such as Nocardioidaceae, Clostridiaceae, Micrococcaceae, and Mycobacteriaceae. MPs substantially influenced the assembly and functional traits of soil bacterial communities; however, they only significantly changed the functional traits of earthworm gut bacterial communities. MPs-aged considerably affected the assembly and functional traits of both soil and earthworm gut bacterial communities. Notably, MPs had a more remarkable effect on nitrogen-related functions than the MPs-aged in numbers for both soil and earthworm gut samples. Co-occurrence network analysis revealed that both MPs and MPs-aged enhanced the synergistic interactions among operational taxonomic units (OTUs) of the composition networks for all samples. For community functional networks, MPs and MPs-aged enhanced the antagonistic interactions for soil samples; however, they exhibited contrasting effects for earthworm gut samples, as MPs enhanced the synergistic interactions among the functional contents. These findings broaden and deepen our understanding of the effects of FRMF-derived microplastics on soil ecosystems, suggesting that the harmful effects of aged plastics on the ecological environment should be considered.

Impact of microplastics on nicosulfuron accumulation and bacteria community in soil-earthworms system

Microplastics (MPs) widely co-occur with various pollutants in soils. However, the data related to the impacts of MPs on terrestrial animal and microbial properties in pesticide-contaminated soils are few. In this study, the influence of MPs (0.01%, 0.1%, and 1%) on nicosulfuron concentrations in soil (10 µg/g) and earthworms were investigated, moreover, microbial community structure and diversity in soil and earthworm gut were also measured. After 30 days, the concentration of nicosulfuron in soil decreased to 1.27 µg/g, moreover, the residual concentration of nicosulfuron in soil (1%MPs and nicosulfuron) was only 44.8% of that in the single nicosulfuron treatment group. The accumulation of nicosulfuron in earthworms (1%MPs and nicosulfuron) was 7.37 µg/g, which was 1.82 times of that in the single nicosulfuron treatment group. In addition, 1% MPs decreased the richness and diversity of the soil and gut bacterial community in earthworms as well as altered microbial community composition, leading to the enrichment of specific microbial community. Our findings imply that MPs may change the migration of pesticides to terrestrial animal and as well as microbial diversity in earthworms and soil.

Low-density polyethylene enhances the disturbance of microbiome and antibiotic resistance genes transfer in soil-earthworm system induced by pyraclostrobin

Non-antibiotic chemicals in farmlands, including microplastics (MPs) and pesticides, have the potential to influence the soil microbiome and the dissemination of antibiotic resistance genes (ARGs). Despite this, there is limited understanding of the combined effects of MPs and pesticides on microbial communities and ARGs transmission in soil ecosystems. In this study, we observed that low-density polyethylene (LDPE) microplastic enhance the accumulation of pyraclostrobin in earthworms, resulting in reduced weight and causing severe oxidative damage. Analysis of 16 S rRNA amplification revealed that exposure to pyraclostrobin and/or LDPE disrupts the microbial community structure at the phylum and genus levels, leading to reduced alpha diversity in both the soil and earthworm gut. Furthermore, co-exposure to LDPE and pyraclostrobin increased the relative abundance of ARGs in the soil and earthworm gut by 2.15 and 1.34 times, respectively, compared to exposure to pyraclostrobin alone. It correlated well with the increasing relative abundance of genera carrying ARGs. Our findings contribute novel insights into the impact of co-exposure to MPs and pesticides on soil and earthworm microbiomes, highlighting their role in promoting the transfer of ARGs. This knowledge is crucial for managing the risk associated with the dissemination of ARGs in soil ecosystems.

Co-exposure to environmental microplastic and the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) induce distinctive alterations in the metabolome and microbial community structure in the gut of the earthworm Eisenia andrei

Microplastics (MPs) are recognized as emergent pollutants and have become a significant environmental concern, especially when combined with other contaminants. In this study, earthworms, specifically Eisenia andrei, were exposed to MPs (at a concentration of 10 μg kg-1 of soil), herbicide 2,4-D (7 mg kg-1 of soil), and a combination of the two for 7 and 14 days. The chemical uptake in the earthworms was measured, and the bacterial and archaeal diversities in both the soil and earthworm gut were analyzed, along with the metabolomic profiles. Additionally, data integration of the two omics approaches was performed to correlate changes in gut microbial diversity and the different metabolites. Our results demonstrated that earthworms ingested MPs and increased 2,4-D accumulation. More importantly, high-throughput sequencing revealed a shift in microbial diversity depending on single or mixture exposition. Metabolomic data demonstrated an important modulation of the metabolites related to oxidative stress, inflammatory system, amino acids synthesis, energy, and nucleic acids metabolism, being more affected in case of co-exposure. Our investigation revealed the potential risks of MPs and 2,4-D herbicide combined exposure to earthworms and soil fertility, thus broadening our understanding of MPs' toxicity and impacts on terrestrial environments.

Enhancing earthworm (Lumbricus terrestris) tolerance to plastic contamination through gut microbiome fortification with plastic-degrading microorganisms

Microorganisms from L. terrestris gut previously exposed to different types of plastic (PET, LDPE, LLDPE, and PS) were studied to be used as probiotics of earthworms in plastic-contaminated soils (LDPE, LLDPE and recycled mulching film) at mesocosm-scale trials. The most abundant morphotypes with enzymatic capacities of interest were identified. Pseudomonas alkylphenolica (PL4) and Pseudomonas putida (PL5) strains were selected to be used as inoculants using Morus alba leaves as carriers to strengthen the intestinal microbiota of earthworms. Culture (selective cetrimide agar medium) and molecular (qPCR) techniques were used to trace the presence of the inoculum in the intestine of the earthworms. Additionally, a metataxonomic analysis was carried out to study the biodiversity and functionality of the earthworm microbiome, and their measure of survival and weight. Probiotics improved the survival rates of earthworms exposed to plastics, which also increased the abundance of microbial groups of interest in plastic bioremediation tasks.

Effect of microplastic pollution on the gut microbiome of anecic and endogeic earthworms

Microplastic (MP) pollution constitutes an emerging type of pollution threatening both aquatic and terrestrial ecosystems. The impact on aquatic ecosystems has been extensively studied, but the effect on terrestrial ecosystems and their inhabitants is mostly underexplored. In this study, we explored the effect of MP pollution on gut bacterial microbiome of endogeic (Aporrectodea caliginosa) and anecic (Lumbricus terrestris) earthworms. The experiments were performed in sandy soil with 0.2% of low-density polyethylene MPs (LDPE MPs). We observed that the endogeic earthworms had 100% survival, while anecic earthworms survived 25 days in the control (i.e. in absence of MPs) and 21 days in the treatment with LDPE MPs. The main driver of shifts in the diversity and composition of the bacterial communities in the gut of tested earthworms was the lifestyle of the worms, followed by the presence of MPs. The bacterial microbiome diversity was significantly different among the two types of earthworms, and the highest bacterial diversity was found in the gut of the endogeic earthworms. The effect of MPs on gut bacterial microbiome was clearly observed in the changes in the relative abundance of several phyla and families of the bacterial communities in both types of earthworms, although it was most evident in the anecic earthworms. The Actinobacteriota, Proteobacteria, and Firmicutes were the main groups enhanced in the MP treatments, suggesting enrichment of the bacterial communities with potential plastic degraders.

Micro- and nanoplastics in soil: Linking sources to damage on soil ecosystem services in life cycle assessment

Soil ecosystems are crucial for providing vital ecosystem services (ES), and are increasingly pressured by the intensification and expansion of human activities, leading to potentially harmful consequences for their related ES provision. Micro- and nanoplastics (MNPs), associated with releases from various human activities, have become prevalent in various soil ecosystems and pose a global threat. Life Cycle Assessment (LCA), a tool for evaluating environmental performance of product and technology life cycles, has yet to adequately include MNPs-related damage to soil ES, owing to factors like uncertainties in MNPs environmental fate and ecotoxicological effects, and characterizing related damage on soil species loss, functional diversity, and ES. This study aims to address this gap by providing as a first step an overview of the current understanding of MNPs in soil ecosystems and proposing a conceptual approach to link MNPs impacts to soil ES damage. We find that MNPs pervade soil ecosystems worldwide, introduced through various pathways, including wastewater discharge, urban runoff, atmospheric deposition, and degradation of larger plastic debris. MNPs can inflict a range of ecotoxicity effects on soil species, including physical harm, chemical toxicity, and pollutants bioaccumulation. Methods to translate these impacts into damage on ES are under development and typically focus on discrete, yet not fully integrated aspects along the impact-to-damage pathway. We propose a conceptual framework for linking different MNPs effects on soil organisms to damage on soil species loss, functional diversity loss and loss of ES, and elaborate on each link. Proposed underlying approaches include the Threshold Indicator Taxa Analysis (TITAN) for translating ecotoxicological effects associated with MNPs into quantitative measures of soil species diversity damage; trait-based approaches for linking soil species loss to functional diversity loss; and ecological networks and Bayesian Belief Networks for linking functional diversity loss to soil ES damage. With the proposed conceptual framework, our study constitutes a starting point for including the characterization of MNPs-related damage on soil ES in LCA.

Ecotoxicological effects of co-exposure biodegradable microplastics polylactic acid with cadmium are higher than conventional microplastics polystyrene with cadmium on the earthworm

Microplastics (MPs) are plastic fragments with particle sizes <5 mm, ubiquitously distributed in terrestrial environments. However, the negative effects of MPs, such as joint-pollution with heavy metals on soil fauna remain controversial. This study investigated survival rate, growth, reproduction, avoidance behavior, histology, biochemical assays, comet assay, qPCR, Cd content, and IBR index. We found that six types of traditional MPs (PC, PP, PVC, LDPE, PET and PS, and PLA (a biodegradable microplastics)) had no adverse effects on earthworm growth, survival and reproduction. Moreover, we found that earthworms exhibit an avoidance behavior towards PLA. Both PS and PLA can exacerbated Cd pollution, leading to loose circular muscle layer, DNA damage in coelomocytes, and impaired antioxidant system due to increased reactive oxygen species (ROS). mRNA level of HSP70 increased under joint-pollution of both PS and Cd or PLA and Cd compared to Cd treatment alone. MPs enhanced Cd accumulation in earthworms in Cd-contaminated soil. Notably, the Integrated Biomarkers Response index revealed that the toxicity of joint PLA and Cd was greater than the joint effect of PS and Cd, which might violate the original intention of biodegradable plastics having non-toxic influence on the soil fauna. Our findings provide new insights into the ecotoxicological effects of MPs, the joint ecotoxicological effects of MPs and Cd on earthworms, and the ecological risks of MPs to soil fauna.

A comprehensive study on the ecotoxicity of ivermectin to earthworms (Eisenia fetida)

Ivermectin (IVM) is a dewormer commonly utilized in animal farming. Nevertheless, there is a deficiency of research on the bioecotoxicity of IVM in soil. In this study, earthworms were utilized as test animals to investigate the ecotoxicological impacts of IVM. The experiment lasted 28 days and involved adding varied doses of IVM to a culture substrate of soil mixed with cow dung and feeding it to earthworms. The experiment entailed recording earthworm weight, number of earthworm cocoons, histological damage, oxidative stress indicators, and gene expression levels. The analysis results showed that earthworm growth and reproduction were hampered by IVM. Moreover, pathological damage to the earthworms increased with increasing IVM concentration, which caused increased oxidative damage to the earthworms. These findings offer a summary of the impact of IVM on earthworms and a reference point for future research examining the ecological implications of IVM.

Effects of cadmium and pyrene on earthworm-associated bacterial communities: Unveiling new perspectives for soil pollution management

Earthworms are considered to be excellent bioindicators of soil pollution. In recent years, there has been increasing interest in examining the effects of soil pollution on earthworm-associated microbiomes, with a particular focus on the gut microbiomes. However, relatively little effort has been invested in comprehensively investigating other microbiomes associated with earthworms and their responses to soil pollution. To fill this gap, we systematically studied the effects of Cd, pyrene, and combined pollution on the bacterial community in different vermicompartments, i.e., burrow wall, gut, and cast, in both epigeic Eisenia fetida and anecic Metaphire guillelmi, using a 2D-terraria incubator and high-throughput sequencing techniques. The results showed that bacterial alpha diversity followed the order of burrow wall > cast > gut, and this did not vary with soil pollution or earthworm ecotypes. Moreover, the dominant phyla in the vermicompartments were similar across different pollution treatments. Principal coordinate analysis (PCoA) revealed that the bacterial communities in different vermicompartments and ecotypes of earthworm were separated from each other, whereas they were grouped together in polluted treatments and unpolluted conditions. These results imply that even in polluted soil, vermicompartment and earthworm ecotypes remain the most significant factors affecting earthworm-associated microbiomes. However, the impacts of soil pollution on the bacterial composition in each vermicompartment were still evident. A comprehensive analysis revealed that the gut bacterial communities are more sensitive to soil contamination than casts and burrow wall in different ecotypes. Additionally, linear discriminant analysis of effect size (LefSe) identified several bacteria in Gemmatimonadota, the Firmicutes phylum in the burrow walls, and Patescibacteria (phyla) in the gut as potential biomarkers for pyrene contamination in soil. This research provides a comprehensive understanding of the effects of soil pollution on earthworm-associated microbiomes, thereby enhancing our understanding of earthworm ecotoxicology and soil pollution management.

Structure and diversity of earthworm communities in long-term irrigated soils with raw effluent and treated wastewater

This study was conducted in two natural meadows: first, soils were irrigated with raw wastewater (SIRWW) and in the second, soils were irrigated with treated wastewater (SITWW). Earthworms were sampled in eight soil blocks spaced 10 m apart at each site. Earthworm community was characterized and compared using density, biomass, composition, structure, species richness, and diversity parameters. At both meadows, 459 earthworm individuals from two families and seven species were collected. The highest earthworm density and species richness were recorded at SIRWW. Nicodrilus caligenus was the most abundant species. Most of earthworm community parameters decreased significantly at SITWW. Only two species (N. caligenus and Octodrilus complanatus) were common between the two grasslands. Among the seven species identified at both meadows, four (Allolobophora longa, Eisenia foetida, Allolobophora rosea, Allolobophora chlorotica) were exclusively present in SIRWW, whereas a single species (Amynthas sp.) was characterized in SITWW. Three ecological earthworm groups (epigeic, endogeic, and anectic) were represented in SIRWW, with the dominance of endogeics. Further studies are needed to quantify pollution in this soils and the accumulation of pollutant load in earthworms. It is also important to highlight the relationship between the abundance and diversity of earthworms in these two ecosystems with soil biological activity.

Effects of biochar on earthworms during remediation of potentially toxic elements contaminated soils

With the widespread use of biochar for soil remediation and improvement, its effects on soil organisms are receiving increased attention. The impacts of biochar on earthworms are still poorly understood. This study aimed to assess the potential ecotoxicity of rice husk biochar (RB) and sludge biochar (SB) on earthworms during potentially toxic elements (PTEs) contaminated soil remediation. The results showed that high rates of RB addition (5% and 10%) caused earthworm mortality, but SB addition did not affect earthworm survival. When added at non-lethal rates (3%), RB and SB addition did not affect survival, weight loss, and PTEs accumulation of earthworms, while resulting in apparent avoidance behavior and oxidative stress response. Among them, RB addition was more likely to cause avoidance behavior, while SB addition had a more pronounced stress effect on earthworms. Additionally, the bacterial communities in the earthworm gut were more sensitive to biochar addition than those in soil. SB addition had a greater impact on earthworm gut bacterial communities than RB addition. The addition of RB and SB increased the abundance of Bacillaceae while decreasing the abundance of Rhizobiaceae in the earthworm gut. This change in the composition of bacterial community may impact the nitrogen cycle and organic matter degradation functions of earthworms. The study suggests that RB and SB may have different effects on earthworms during PTEs-contaminated soil remediation, depending on their properties. It will assist us to understand the potential ecotoxicity of biochar and provide several guidance for its safe application.

Environmental Microplastic Exposure Changes Gut Microbiota in Chickens

As novel environmental contaminants, MPs exist widely in the environment and accumulate in organisms, which has become a global ecological problem. MP perturbations of organismal physiology and behavior have been extensively recorded in aquatic animals, but the potential effects of MPs on poultry are not well characterized. Here, we explored the adverse effects of MP exposure on the growth performance and gut microbiota of chickens. Results showed that the growth performance of chickens decreased significantly during MP exposure. Additionally, Firmicutes, Bacteroidota, and Proteobacteria were found to be dominant in the gut microbiota of MP-exposed chickens, regardless of health status. Although the types of dominant bacteria did not change, the abundances of some bacteria and the structure of the gut microbiota changed significantly. Compared with the controls, the alpha diversity of gut microbiota in chickens exposed to MPs showed a significant decrease. The results of comparative analyses of bacteria between groups showed that the levels of 1 phyla (Proteobacteria) and 18 genera dramatically decreased, whereas the levels of 1 phyla (Cyanobacteria) and 12 genera dramatically increased, during MP exposure. In summary, this study provides evidence that exposure to MPs has a significant impact on the growth performance and gut microbial composition and structure of chickens, leading to a gut microbial imbalance. This may raise widespread public concern about the health threat caused by MP contamination, which is relevant to the maintenance of environmental quality and protection of poultry health.

Inhibitory effect of polyethylene microplastics on roxarsone degradation in soils

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, Rox(V)), an extensively used organoarsenical feed additive, enters soils through the application of Rox(V)-containing manure and further degrades to highly toxic arsenicals. Microplastics, as emerging contaminants, are also frequently detected in soils. However, the effects of microplastics on soil Rox(V) degradation are unknown. A microcosm experiment was conducted to investigate soil Rox(V) degradation responses to polyethylene (PE) microplastics and the underlying mechanisms. PE microplastics inhibited soil Rox(V) degradation, with the main products being 3-amino-4-hydroxyphenylarsonic acid [3-AHPAA(V)], N-acetyl-4-hydroxy-m-arsanilic acid [N-AHPAA(V)], arsenate [As(V)], and arsenite [As(III)]. This inhibition was likely driven by the decline in soil pH by PE microplastic addition, which may directly enhance Rox(V) sorption in soils. The decreased soil pH further suppressed the nfnB gene related to nitroreduction of Rox(V) to 3-AHPAA(V) and nhoA gene associated with acetylation of 3-AHPAA(V) to N-AHPAA(V), accompanied by a decrease in the relative abundance of possible Rox(V)-degrading bacteria (e.g., Pseudomonadales), although the diversity, composition, network complexity, and assembly of soil bacterial communities were largely influenced by Rox(V) rather than PE microplastics. Our study emphasizes microplastic-induced inhibition of Rox(V) degradation in soils and the need to consider the role of microplastics in better risk assessment and remediation of Rox(V)-contaminated soils.

Randomly-shaped nanoplastics induced stronger biotoxicity targeted to earthworm Eisenia fetida species: Differential effects and the underlying mechanisms of realistic and commercial polystyrene nanoplastics

Nanoplastics (NPs) are widely distributed in various environments, including soil, and have been known to adversely affect soil organisms. Currently, most of the obtained studies were principally focused on the ecological risks of commercial sphere-type microbeads (SNPs), while ignoring that they might be different from randomly-shaped nanoplastics (RNPs) in a real environment. Thus, this study was undertaken to probe the shape-dependent effects of NPs on the earthworm Eisenia fetida and the corresponding poisoning mechanisms, and discriminate the toxicity differences between SNPs and RNPs at the molecule, cell, tissue, and animal levels. The results showed SNPs and RNPs exhibited lethal effects to earthworms with the LC₅₀ determined to be 27.42 g/kg and 21.69 g/kg, respectively after a 28-day exposure. SNPs and RNPs exposure can cause ROS-induced ROS release in worm, inducing oxidative stress through mitochondria-mediated pathway, leading to lipid peroxidation, DNA damage, and histopathological changes, thereby contributing to decreased stress resistance against exogenous stressors. To reduce ROS-mediated oxidative damage, the antioxidant defense system in E. fetida can be activated, which scavenges unwanted ROS. High doses of SNPs and RNPs inhibited the AChE activity in worms, causing excess acetylcholine accumulation in the synaptic space, which finally lead to neurotoxicity. Also, two kinds of NPs can induce the abnormal expression of genes relevant to oxidative stress, reproduction, growth, and tight junction protein in E. fetida, which ultimately contribute to various detrimental effects, tissue damage and dysfunction, reproductive and developmental toxicity. The results obtained from the Integrated Biological Response (IBR) suggested that long-term exposure to high-dose SNPs and RNPs can induce the stronger toxicity effects to E. fetida worms, and RNPs-induced toxicity can be different and stronger than that of SNPs. Our results provide insights for revealing the environmental effects posed by randomly-shaped NPs-contaminated soil, and are of importance for assessing the contribution of NPs with different physical characteristics to soil eco-safety.

Environmental impacts of microplastic and role of plastisphere microbes in the biodegradation and upcycling of microplastic

Increasing usage of plastic has led to the deposition of plastic in the environment which later become microplastic, a pollutant of global concern. These polymeric particles affect the ecosystem bestowing toxicity and impede the biogeochemical cycles. Besides, microplastic particles have been known for their role in aggravating the effect of various other environmental pollutants including organic pollutants and heavy metals. These microplastic surfaces are often colonized by the microbial communities also known as "plastisphere microbes" forming biofilms. These microbes include cyanobacteria like Nostoc, Scytonema, etc., and diatoms like Navicula, Cyclotella, etc. Which become the primary colonizer. In addition to the autotrophic microbes, Gammaproteobacteria and Alphaproteobacteria dominate the plastisphere microbial community. These biofilm-forming microbes can efficiently degrade the microplastic in the environment by secreting various catabolic enzymes such as lipase, esterase, hydroxylase, etc. Besides, these microbes have shown great potential for the bioconversion of microplastic to polyhydroxyalkanoates (PHA), an energy efficient and sustainable alternative to the petroleum based plastics. Thus, these microbes can be used for the creation of a circular economy using waste to wealth strategy. This review provides a deeper insight into the distribution, transportation, transformation, and biodegradation of microplastic in the ecosystem. The formation of plastisphere by the biofilm-forming microbes has been described in the article. In addition, the microbial metabolic pathways and genetic regulations involved in the biodegradation have been discussed in detail. The article suggests the microbial bioremediation and upcycling of microplastic along with various other strategies for effectively mitigate the microplastic pollution.

Detecting microplastics in organic-rich materials and their potential risks to earthworms in agroecosystems

Microplastics (MPs) are a major emerging contaminant in agroecosystems, due to their significant resistance to degradation in terrestrial environments. Although previous investigations have reported the harmful effects of MPs contamination on soil biological properties, still little is known about the characteristics and fate of MPs in biosolid-amended soils and their risks to soil biota, particularly earthworms. We determined microplastics' concentration, size distribution, and chemical composition in 3 sewage sludge biosolids and 6 biosolid-amended agricultural soils. In addition, we assessed the potential short-term risks of MPs to earthworms' (Amynthas Gracilis and Eisenia Fetida) survival rate and fitness in an environmentally relevant exposure study (28 days). Biosolid-amended soils (1000-3100 MPs kg^-1 dry mass) showed ≈30 times lower MPs content than investigated biosolids (55400-73800 MPs kg^-1 dry mass), with microplastic fragment to fibre ratios between 0.2 and 0.6 and 0.3-0.4 in soils and biosolids, respectively. Total MPs dry mass was also ≈19 times lower in assessed soils (12-26 mg kg^-1) than biosolids (328-440 mg kg^-1). On average 77% and 80% of plastic fragments had a lower dimension than 500 µm, while 50% and 67% of plastic fibres had a length of less than 1000 µm in soil and biosolid samples, respectively. Polyethylene (23.6%) was the major source of microplastic contamination in biosolid-amended soils, while polyethylene terephthalate (41.6%) showed the highest concentration in biosolid samples. Spiked polyethylene MPs did not show any significant effect on earthworms' survival rate (93-99%). However, biosolid application significantly (P < 0.05) decreased survival rate of Eisenia Fetida (81%) but showed no significant effect on Amynthas Gracilis (93%). Biosolid amendment significantly (P < 0.05) decreased earthworms' growth rate, with higher impact on Eisenia Fetida than Amynthas Gracilis, while there were no significant differences between control and microplastic spiked treatments. The overall decrease in MPs concentration of earthworm casts, compared with initial MPs concentrations in soil, indicated that the investigated species did not bioaccumulate MPs during the exposure experiment.

Time-dependent effects of microplastics on soil bacteriome

Microplastic threats to biodiversity, health and ecological safety are adding to concern worldwide, but the real impacts on the functioning of organisms and ecosystems are obscure owing to their inert characteristics. Here we investigated the long-lasting ecological effects of six prevalent microplastic types: polyethylene (PE), polypropylene (PP), polyamide (PA), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) on soil bacteria at a 2 % (w/w) level. Due to the inertia and lack of available nitrogen of these microplastics, their effects on bacteriome tended to converge after one year and were strongly different from their short-term effects. The soil volumes around microplastics were very specific, in which the microplastic-adapted bacteria (e.g., some genera in Actinobacteria) were enriched but the phyla Bacteroidetes and Gemmatimonadetes declined, resulting in higher microbial nitrogen requirements and reduced organic carbon mineralization. The reshaped bacteriome was specialized in the genetic potential of xenobiotic and lipid metabolism as well as related oxidation, esterification, and hydrolysis processes, but excessive oxidative damage resulted in severe weakness in community genetic information processing. According to model predictions, microplastic effects are indirectly derived from nutrients and oxidative stress, and the effects on bacterial functions are stronger than on structure, posing a heavy risk to soil ecosystems.

Biological responses of Chironomus sancticaroli to exposure to naturally aged PP microplastics under realistic concentrations

Microplastic (MP) is yet another form of chronic anthropogenic contribution to the environment. MPs are plastic particles (<5 mm) that have been widely found in the most diverse natural environments, but their real impacts on ecosystems are still under investigation. Here, we studied the toxicity of naturally aged secondary polypropylene (PP) MPs after constant exposure to ultraviolet radiation (26 µm) to the third instar larvae of Chironomus sancticaroli, a dipteran species. The concentrations tested were 13.5; 67.5; and 135 items g^-1 of dry sediment. C. sancticaroli organisms were investigated for fragment ingestion, mortality and changes in enzymatic biomarkers after 144 h of exposure. The organisms were able to ingest MPs from the first 48 h, and the amount of items internalized was dose-dependent and time-dependent. Overall, the results show that mortality was low, being significant at the lowest and highest concentrations (13.5 and 135 items g^-1). Regarding changes in biochemical markers, after 144 h MDA and CAT activities were both significantly altered (increased and reduced, respectively), while SOD and GST levels were unchanged. In the present study, naturally aged polypropylene MPs induced biochemical toxicity in C. sancticaroli larvae, with toxicity being higher according to exposure time and particle concentration.

Evaluation of soil ecological health after exposure to environmentally relevant doses of Di (2-ethylhexyl) phthalate: Insights from toxicological studies of earthworms at different ecological niches

As one of the most critical soil faunas in agroecosystems, earthworms are significant in preserving soil ecological health. Di (2-ethylhexyl) phthalate (DEHP) is a major plasticizer and widely used in plastic products like agricultural films. However, it has become ubiquitous contaminant in agricultural soil and poses a potential threat to soil health. Although the awareness of the impacts of DEHP on soil ecology is increasing, its adverse effects on soil invertebrates, especially earthworms, are still not well developed. In this study, the ecotoxicological effects and underlying mechanisms of environmentally relevant doses DEHP on earthworms of different ecological niches were investigated at the individual, cytological, and biochemical levels, respectively. Results showed that the acute toxicity of DEHP to M. guillelmi was higher than E. foetida. DEHP induced reactive oxygen species (ROS) levels and further caused oxidative damage (including cellular DNA and lipid peroxidation damage) in both species, speculating that they may exhibit similar oxidative stress mechanisms. Furthermore, two earthworms presented the alleviated toxicity when re-cultured in uncontaminated circumstances, yet, the accumulated ROS in bodies could not be completely scavenged. Risk assessment indicated that the detrimental impacts of DEHP were more significant in the M. guillelmi than in E. foetida in whole experiments prides, and the biomarkers additionally showed a species-specific trend. Besides, molecular docking revealed that DEHP could bind to the active center of superoxide dismutase/catalase (SOD/CAT) by hydrogen bonding or hydrophobic interactions. Overall, this study will provide a novel insight for accurate contaminant risk assessment, and also highlight that the comprehensive biological effects of different species should be emphasized in soil ecological health diagnostics and environmental toxicology assays, as otherwise it may lead to underestimation or misestimation of the soil health risk of contaminants.

Abundance, spatial distribution, and characteristics of microplastics in agricultural soils and their relationship with contributing factors

Agro-ecosystem contamination with microplastics (MPs) is of great concern. However, limited research has been conducted on the agricultural soil of tropical regions. This paper investigated MPs in the agro-ecosystem of Hainan Island, China, as well as their relationships with plastic mulching, farming practices, and social and environmental factors. The concentration of MPs in the study area ranged from 2800 to 82500 particles/kg with a mean concentration of 15461.52 particles/kg. MPs with sizes between 20 and 200 μm had the highest abundance of 57.57%, fragment (58.16%) was the most predominant shape, while black (77.76%) was the most abundant MP colour. Polyethylene (PE) (71.04%) and polypropylene (PP) (19.83%) were the main types of polymers. The mean abundance of MPs was significantly positively correlated (p < 0.01) with all sizes, temperature, and shapes except fibre, while weakly positively correlated with the population (p = 0.21), GDP (p = 0.33), and annual precipitation (p = 0.66). In conclusion, plastic mulching contributed to significant contamination of soil MPs in the study area, while environmental and social factors promoted soil MPs fragmentation. The current study results indicate serious contamination with MPs, which poses a concern regarding ecological and environmental safety.

Exposure to Polypropylene Microplastics via Oral Ingestion Induces Colonic Apoptosis and Intestinal Barrier Damage through Oxidative Stress and Inflammation in Mice

Extensive environmental pollution by microplastics has increased the risk of human exposure to plastics. However, the biosafety of polypropylene microplastics (PP-MPs), especially of PP particles < 10 μm, in mammals has not been studied. Thus, here, we explored the mechanism of action and effect of exposure to small and large PP-MPs, via oral ingestion, on the mouse intestinal tract. Male C57BL/6 mice were administered PP suspensions (8 and 70 μm; 0.1, 1.0, and 10 mg/mL) for 28 days. PP-MP treatment resulted in inflammatory pathological damage, ultrastructural changes in intestinal epithelial cells, imbalance of the redox system, and inflammatory reactions in the colon. Additionally, we observed damage to the tight junctions of the colon and decreased intestinal mucus secretion and ion transporter expression. Further, the apoptotic rate of colonic cells significantly increased after PP-MP treatment. The expression of pro-inflammatory and pro-apoptosis proteins significantly increased in colon tissue, while the expression of anti-inflammatory and anti-apoptosis proteins significantly decreased. In summary, this study demonstrates that PP-MPs induce colonic apoptosis and intestinal barrier damage through oxidative stress and activation of the TLR4/NF-κB inflammatory signal pathway in mice, which provides new insights into the toxicity of MPs in mammals.

Anthropogenic disturbance promotes the diversification of antibiotic resistance genes and virulence factors in the gut of plateau pikas (Ochotona curzoniae)

The prevalence and transmission of antibiotic resistance genes (ARGs) and virulence factors (VFs) pose a great threat to public health. The importance of pollution in determining the occurrence of ARGs and VFs in wildlife is poorly understood. Using a metagenomic approach, this study investigates the composition and functional pathways of bacteria, ARGs, and VFs in the gut microbiome of Plateau pikas in regions of medical pollution (MPR), heavy tourist traffic (HTR), and no contamination (NCR). We found that the abundance of probiotic genera (Clostridium, Eubacterium, Faecalibacterium, and Roseburia) were significantly lower in the HTR. The metabolic pathways of replication and repair in the endocrine and nervous systems were significantly enriched in the MPR, whereas endocrine and metabolic diseases were significantly enriched in the NCR. The Shannon and Gini–Simpson α-diversity indices of ARGs were highest in the HTR, and there were significant differences in β-diversity among the three regions. The resistance of ARGs to glycopeptide antibiotics increased significantly in the MPR, whereas the ARGs for aminocoumarins increased significantly in the HTR. The diversity of mobile genetic elements (MGEs) was significantly higher in the MPR than in other regions. We observed a strong positive correlation between ARGs and pathogenic bacteria, and the network structure was the most complex in the MPR. There were significant differences in the β-diversity of VFs among the three regions. Medical pollution led to significant enrichment of fibronectin-binding protein and PhoP, whereas tourism-related pollution (in the HTR) led to significant enrichment of LPS and LplA1. Our study indicates that environmental pollution can affect the structure and function of gut microbes and disseminate ARGs and VFs via horizontal transmission, thereby posing a threat to the health of wild animals.

Adverse effects of microplastics on earthworms: A critical review

Microplastics are widely distributed in terrestrial environments and have been known to adversely affect earthworms. Based on 65 publications, we summarized the effects of microplastics on the growth, behavior, oxidative responses, gene expression, and gut microbiota of earthworms. Since microplastics are often present simultaneously with other pollutants, especially heavy metals and hydrophobic organic chemicals (HOCs), the interactions and combined effects of microplastics and these pollutants on earthworms have also been discussed. It has been shown that earthworms can selectively ingest microplastics, preferring to those with smaller particle size (especially smaller than 50 μm) and biodegradable compositions. Generally, microplastics with higher concentrations (especially those > 0.5%, w/w) and smaller sizes (e.g., 100 nm) have greater adverse effects on earthworms. Additionally, microplastics can facilitate the accumulation of heavy metals and organic pollutants by earthworms and pose severer damages. Current knowledge gaps and perspectives for future work are pointed out.

Effects of conventional versus biodegradable microplastic exposure on oxidative stress and gut microorganisms in earthworms: A comparison with two different soils

The ecotoxicity of microplastics (MPs) to soil animals is widely recognized; however, most studies have only focused on conventional MPs. This study compared the effects of various concentrations (0.5%, 1%, 2%, 5%, 7%, and 14%, w/w) of polyethylene (PE) and biodegradable polylactic acid (PLA) MPs on oxidative stress and gut microbes in Eisenia fetida (E. fetida) from two different soils (black and yellow soils). The results indicated that the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione S-transferase (GST), and acetylcholinesterase (AchE) decreased after exposure to PE and PLA MPs for 14 days, whereas malondialdehyde (MDA) levels increased. This level of decrease or increase exhibited a "decrease-increase" trend with increasing MP exposure doses. After 28 days, the activities of SOD, CAT, POD, AchE, and GST increased, whereas MDA levels decreased, and the level of increase or decrease increased with increasing MP dose. The integrated biological response index revealed that the toxic effects of MPs were concentration-dependent, and MP concentration was more important than MP type or soil type. The toxicity of PE MPs was generally higher than that of PLA MPs on day 14, with no significant difference on day 28. Moreover, MPs did not alter the dominant gut microbiota of E. fetida, but altered the relative abundances of Actinobacteriota, Bacteroidota, Ascomycota, and Rozellomycota. Furthermore, different gut microbial phyla exhibited discrepant responses to MPs. Our results demonstrated that both conventional and biodegradable MPs induced oxidative stress in E. fetida, and biodegradable MPs showed no less toxicity compared to conventional MPs. Additionally, MP-induced toxic effects did not differ significantly between black and yellow soils, suggesting that MP-induced toxic effects were less affected by soil type.

Vermicomposting leads to more abundant microplastics in the municipal excess sludge

Municipal excess activated sludge is not only an important reservoir of microplastics particles, but is also a vehicle of entry of microplastics into the environments as soil amendments or organic fertilizer. Vermicomposting is a cost-effective technology for sludge valorization. However, it is not clear whether vermicomposting affects the occurrence of microplastics in residual sludge. Here, the variation of microplastics (0.05-5 mm) in sludge, including the abundance, type, size, and morphology, before and after vermicomposting by epigeic earthworms under different temperature conditions (15 °C, 20 °C and 25 °C) were investigated by micro Fourier Transform Infrared Spectroscopy (μ-FTIR) and Scanning Electronic Microscopy (SEM). More abundant (over 10⁴ particles ∙kg^-1 (dry weight)), and smaller microplastics (over 60% in total with 0.05-0.5 mm) in the treated sludge via earthworms were observed compared to the raw sludge. The increment of vermicomposting temperature was more obvious (p < 0.05) for the enrichment of the microplastics, especially for polyethylene particle. Gizzard grinding and microbial digestion in the gut of earthworms may contribute to the fragment of microplastics. The present study suggests that the sludge-sourced vermicompost is still an important hotspot of microplastics, posing a potential threat to the receiving environments.

Current development and future challenges in microplastic detection techniques: A bibliometrics-based analysis and review

Microplastics have been considered a new type of pollutant in the marine environment and have attracted widespread attention worldwide in recent years. Plastic particles with particle size less than 5 mm are usually defined as microplastics. Because of their similar size to plankton, marine organisms easily ingest microplastics and can threaten higher organisms and even human health through the food chain. Most of the current studies have focused on the investigation of the abundance of microplastics in the environment. However, due to the limitations of analytical methods and instruments, the number of microplastics in the environment can easily lead to overestimation or underestimation. Microplastics in each environment have different detection techniques. To investigate the current status, hot spots, and research trends of microplastics detection techniques, this review analyzed the papers related to microplastics detection using bibliometric software CiteSpace and COOC. A total of 696 articles were analyzed, spanning 2012 to 2021. The contributions and cooperation of different countries and institutions in this field have been analyzed in detail. This topic has formed two main important networks of cooperation. International cooperation has been a common pattern in this topic. The various analytical methods of this topic were discussed through keyword and clustering analysis. Among them, fluorescent, FTIR and micro-Raman spectroscopy are commonly used optical techniques for the detection of microplastics. The identification of microplastics can also be achieved by the combination of other techniques such as mass spectrometry/thermal cracking gas chromatography. However, these techniques still have limitations and cannot be applied to all environmental samples. We provide a detailed analysis of the detection of microplastics in different environmental samples and list the challenges that need to be addressed in the future.

Effects of microplastics from disposable medical masks on terrestrial invertebrates

This study investigated impacts of microplastics from disposable polypropylene medical masks on woodlice Porcellio scaber, mealworm larvae Tenebrio molitor and enchytraeids Enchytraeus crypticus. Effects of microplastics on survival, reproduction, immune parameters and energy-related traits were assessed after 21 days exposure in soil. Microplastics obtained from each medical mask layer separately differed in size and shape (inner frontal layer: 45.1 ± 21.5 µm, fibers; middle filtering layer: 55.6 ± 28.5 µm, fragments; outer layer: 42.0 ± 17.8 µm, fibers) and composition of additives. Overall, the concentrations of metals and organic chemicals were too low to cause effects on soil invertebrates. The microplastics from disposable medical masks at 0.06%, 0.5%, 1.5%, w/w did not induce severe adverse effects on survival or reproduction (for enchytraeids). A transient immune response of woodlice and a change in energy-related traits in mealworms were observed, which was most clearly seen for the microplastics from the outer layer. This was reflected in increased electron transfer system activity of mealworms and different immune response dynamics of woodlice. In conclusion, the tested soil invertebrates respond to microplastics from disposable medical masks, but it remains unclear what these changes mean for their fitness on the long term.

Comparison of fitness effects in the earthworm Eisenia fetida after exposure to single or multiple anthropogenic pollutants

Terrestrial ecosystems are exposed to many anthropogenic pollutants. Non-target effects of pesticides and fertilizers have put agricultural intensification in the focus as a driver for biodiversity loss. However, other pollutants, such as heavy metals, particulate matter, or microplastic also enter the environment, e.g. via traffic and industrial activities in urban areas. As soil acts as a potential sink for such pollutants, soil invertebrates like earthworms may be particularly affected by them. Under natural conditions soil invertebrates will likely be exposed to combinations of pollutants simultaneously, which may result in stronger negative effects if pollutants act synergistically. Within this work we study how multiple pollutants affect the soil-dwelling, substrate feeding earthworm Eisenia fetida. We compared the effects of the single stressors, polystyrene microplastic fragments, polystyrene fibers, brake dust and carbon black, with the combined effect of these pollutants when applied as a mixture. Endpoints measured were survival, increase in body weight, reproductive fitness, and changes in three oxidative stress markers (glutathione S-transferase, catalase and malondialdehyde). We found that among single pollutant treatments, brake dust imposed the strongest negative effects on earthworms in all measured endpoints including increased mortality rates. Sub-lethal effects were found for all pollutants. Exposing earthworms to all four pollutants simultaneously led to effects on mortality and oxidative stress markers that were smaller than expected by the respective null models. These antagonistic effects are likely a result of the adsorption of toxic substances found in brake dust to the other pollutants. With this study we show that effects of combinations of pollutants cannot necessarily be predicted from their individual effects and that combined effects will likely depend on identity and concentration of the pollutants.

Ecotoxicological effects of micro- and nanoplastics on terrestrial food web from plants to human beings

Micro- and nanoplastics (MNPs) are present in almost all environmental compartments. Terrestrial soils are major environmental reservoirs for MNPs, but the ecotoxicological effects of MNPs on terrestrial biota remain relatively understudied. In this review, we collated findings of previous research on the uptake and impact of MNPs in terrestrial organisms, including flora, fauna, and human beings. Terrestrial plants can take up MNPs via the roots or leaves and translocate them to other parts. MNPs have been detected in the gastrointestinal tracts or feces of many terrestrial animals, including some high trophic-level predators, indicating the incidence of direct ingestion or trophic transfer of MNPs. The presence of MNPs in food items and human feces combines to verify human intake of MNPs via the dietary pathway. Exposure to MNPs can cause diverse effects on terrestrial organisms, including alterations in growth performance, oxidative stress, metabolic disturbance, cytotoxicity, genotoxicity, and mortality. The biological internalization and impact of MNPs are influenced by the physicochemical properties of MNPs (e.g., particle size, polymer type, surface chemistry, and exposure concentrations) and the physiology of the species. MNPs can also affect the bioavailability of co-occurring intrinsic or extrinsic contaminants to terrestrial biota, but their specific role is under dispute. Finally, we underlined the current research gaps and proposed several priorities for future studies.

Uncontrolled Disposal of Used Masks Resulting in Release of Microplastics and Co-Pollutants into Environment

The global panic caused by COVID-19 has continued to increase people’s demand for masks. However, due to inadequate management and disposal practice, these masks have, unfortunately, entered the environment and release a large amount of microplastics (MPs), posing a serious threat to the environment and human health. Understanding the occurrence of mask waste in various environments, release of mask-origin MPs, and related environmental risk is essential to mask-waste management in current and future epidemic prevention and control. This paper focuses on the global distribution of mask waste, the potential release of waste-origin MPs, and the impact on the environment. Specifically, the physical and chemical properties of polypropylene (the most common plastic material in a mask), which show a high adsorption capacity for heavy metals and organic pollutants and play a role as a support for microbial growth, were extensively reported. In addition, several important issues that need to be resolved are raised, which offers a direction for future research. This review focuses on the essentiality of handling masks to avoid potential environmental issues.

Accumulation of nylon microplastics and polybrominated diphenyl ethers and effects on gut microbial community of Chironomus sancticaroli

Microplastics (MP) are emerging contaminants with the capacity to bind and transport hydrophobic organic compounds of environmental concern, such as polybrominated diphenyl ethers (PBDEs). The aim of this study was to investigate the ingestion of nylon (polyamide) MP alone and when associated with PBDEs and their effects on Chironomus sancticaroli larvae survival and microbiome structure. Survival, PBDE uptake and microbial community composition were measured in fourth instar larvae exposed for 96 h to BDEs- 47, 99, 100 and 153 in the presence and absence of 1% w/w MP in sediment. Microbiome community structures were determined through high throughput sequencing of 16S small subunit ribosomal RNA gene (16S rRNA). Initial experiments showed that larvae ingested MP faster at 0.5% w/w MP, while depuration was more efficient at 1% w/w MP, although retention of MP was seen even after 168 h depuration. No mortality was observed as a result of PBDEs and MP exposure. MP had a negative effect on PBDE concentration within larvae (η² = 0.94) and a negative effect on sediment concentrations (η² = 0.48). In all samples, microbial communities were dominated by Alphaproteobacteria, Betaproteobacteria, Actinobacteria and Gammaproteobacteria. Bacterial alpha diversity was not significantly affected by PBDEs or MP exposure. However, the abundance of discrete bacterial taxa was more sensitive to MP (X² = 45.81, p = 0.02), and PBDE exposure. Our results highlight that C. sancticaroli showed no acute response to MPs and PBDEs, but that MPs influenced bacterial microbiome structure even after only short-term acute exposure.

Reduction performance of microplastics and their behavior in a vermi-wetland during the recycling of excess sludge: A quantitative assessment for fluorescent polymethyl methacrylate

Large amounts of microplastics (MPs) that have accumulated in excess sludge may increase the environmental risk for its subsequent treatment. This study aimed to investigate the performance and mechanism of the reduction of MPs in excess sludge in a vermi-wetland. For this, 1 μm, 100 μm, and 500 μm of fluorescent MPs stained with Nile red were added to raw sludge, and their decreased numbers were quantified during the treatment of sludge. The results showed that the removal rates of chemical oxygen demand and total solids from the excess sludge were 63.44%-90.98% and 37.61%-51.56% in the vermi-wetland, respectively. The numbers of 1 μm, 100 μm, and 500 μm MPs could be reduced by 86.62%-95.69%, 95.44%-99.52%, and 100% in the vermi-wetland, respectively. These results indicate that the vermi-wetland is more effective at eliminating MPs. Further insight into the vermi-wetland stratification was obtained, and more than 74.87% of the MPs were intercepted in the vermicompost layer. Moreover, all the particle sizes of MPs were found in the excrement of earthworms. However, only 1 μm MPs were detected in their digestive organs. This study suggests that the interception effect is primarily responsible for elimination of MPs in excess sludge, and the bioturbation of earthworms plays an important role in the mobilization of MPs in vermi-wetlands.

Microplastics impact the accumulation of metals in earthworms by changing the gut bacterial communities

Microplastics (MPs) are defined as plastic debris with particle size smaller than 5 mm, which have been frequently detected in environments. In this study, earthworms (Eisenia foetida) were exposed to three different sized polystyrene (PS; 0.1, 10 and 100 μm) at 10 and 100 mg per kg soil for 21 days. We examined the contents of metals (Cu, Zn, Ni and Pb) and gut microbial communities in earthworms exposed to MPs. Results showed that MPs reduced the accumulation of Ni and Pb in earthworms on the 21st day. The composition of gut bacterial communities was altered in earthworms exposed to MPs, especially 10 μm MPs, featuring a higher relative abundance of Proteobacteria (44.5%) and Bacteroidetes (27.1%) than the control group. Additionally, gut microorganisms including genus Paenibacillus and Achromobacter in earthworms were expected to be potential biomarkers for Cu and Zn. The microbial community networks showed that MPs affected bacterial community connections by size effect, and MPs with smaller size increased the complexity of earthworm microbial community networks. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that metabolism was the main difference in the bacterial communities in different treatments, especially carbohydrate metabolism and amino acid metabolism, which was relevant to the survival and growth of bacteria. This study provides insight into the environmental risks of MPs on terrestrial organisms.

Extraction, identification, and environmental risk assessment of microplastics in commercial toothpaste

Microplastics in personal care and food products are given much importance globally due to the adverse impact of microplastics on living beings. In the present study, microplastics from ten different commercially sold toothpaste in India were extracted by vacuum filtration and characterized with microscopic and Fourier-transform infrared spectroscopic analyses. Results revealed that colorless fragments and fibers were the microparticle types of common occurrence which ranged from 0.2 to 0.9% weight in the toothpaste with an abundance range of 32.7-83.2%. Fifty percent of the toothpaste samples showed more than 50% microplastic particle abundance indicating that the microplastic plastic particles were added by the manufacturers. The minimum size of microplastics recorded in the present study was 3.5 μm with a maximum size exceeding 400 μm. The maximum number of microplastics in the toothpaste was 167, 508 and 193 respectively, distributed in the size range of <100 μm, 100-400 μm, and >400 μm. The present study recorded four major polymer types, viz., cellophane, polypropylene, polyvinyl chloride, and polyamide in the toothpaste samples. Surprisingly, polyethylene-a common polymer reported in toothpaste was not traced in the present samples. Regarding the Indian context, the current study is a new addition to the knowledge of the occurrence of microplastics in toothpaste. The average annual addition of microplastics into the environment through toothpaste was calculated as 1.4 billion g/year for India, posing a significant threat to the environment.

Effects of diisononyl phthalate exposure on the oxidative stress and gut microorganisms in earthworms (Eisenia fetida)

Phthalate esters (PAEs) are widely used as plasticizers and can be ubiquitously detected in environment. However, the toxic effects and mechanisms of diisononyl phthalate (DINP) on earthworms are still poorly understood. In this study, earthworms (Eisenia fetida) were exposed to DINP at various doses (0, 300, 600, 1200, and 2400 mg/kg) to investigate their subchronic toxicity. The results demonstrated that the reactive oxygen species (ROS) levels displayed an "increase-decrease" trend with the increasing DINP doses after DINP exposure on days 7, 14, 21, and 28. The malondialdehyde (MDA) content increased with increasing DINP doses on days 7, 14, and then decreased on days 21, 28. The values of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) showed similar variation patterns and reached a maximum level on 21 d. Moreover, on day 28, the SOD and CAT gene expression levels were upregulated, while the GST gene expression levels were downregulated. Meanwhile, 16S rRNA genes of E. fetida gut bacteria and surrounding soil bacteria were measured after 28 days of exposure to DINP. The Chao index of E. fetida gut bacteria decreased when the treatment with the highest concentration (2400 mg/kg) was applied. At the phylum level, the abundance of Chloroflexi was significantly lower in the gut of E. fetida. In addition, the abundance of Proteobacteria at the phylum level and Ottowia at the genus level significantly increased in the surrounding soil. Overall, our results shed light on the toxic mechanism of DINP at biochemical, molecular, and omics levels, and contributed to a better understanding of the ecotoxicity of DINP.

Time-dependent immune response in Porcellio scaber following exposure to microplastics and natural particles

Microplastics are very common contaminants in the environment. Despite increasing efforts to assess the effects of microplastics on soil organisms, there remains a lack of knowledge on how organisms respond to diverse types of microplastics after different exposure durations. In the present study, we investigated the immune response of the terrestrial crustacean Porcellio scaber exposed to the two most common microplastic particles in the environment: polyester fibres and tyre particles. We also tested two natural particles: wood dust and silica powder, with all treatments performed at 1.5% w/w. The response of P. scaber was evaluated at the level of the immune system, and also the biochemical, organism and population level, after different exposure durations (1, 2, 4, 7, 14, 21 days). These data reveal dynamic changes in the levels of some immune parameters shortly after exposure, with a gradual return to control values. The total number of haemocytes was significantly decreased after 4 days of exposure to tyre particles, while the proportion of different haemocyte types in the haemolymph was altered shortly after exposure to both polyester fibres and tyre particles. Moreover, 7 days of exposure to tyre particles resulted in increased superoxide dismutase activity in the haemolymph, while metabolic activity in whole woodlice (measured as electron transport system activity) was increased after exposure for 7, 14 and 21 days. In contrast, the natural particles did not elicit any significant changes in the measured parameters. Survival and feeding of P. scaber were not altered by exposure to the microplastics and natural particles in soil. Overall, this study defines a time-dependent transient immune response of P. scaber, which indicates that immune parameters represent sensitive biomarkers of exposure to microplastics. We discuss the importance of using natural particles in studies of microplastics exposure and their effects.

Earthworms' Degradable Bioplastic Diet of Polylactic Acid: Easy to Break Down and Slow to Excrete

Microplastics (MPs) in soils may be ingested by terrestrial animals. While the application of bioplastics is increasing, the ingestion and excretion characteristics of bio-MPs by terrestrial animals are poorly understood as compared to fossil-MPs. Here, the approach-avoidance behavior of adult earthworms Eisenia fetida to MP-contaminated soil was assessed. Fossil-based poly(ethylene terephthalate) (PET) and bio-based poly(lactic acid) (PLA) MPs were found to be preferred by the earthworms, which might be due to the odor of polymer monomers. MPs in earthworm casts were analyzed by microscopy counting and liquid chromatography-tandem mass spectrometry. The amount of microscopically recognizable excreted PET and PLA was 553 and 261 items/g, respectively, while a higher proportion of smaller PLA particles also presented. Bio-based PLA is much easy to break down by earthworms than fossil-based PET. Submicron and nanocron PLA accounted for 57 and 13% of the excreted PLA on the 10th day of excretion. MP excretion was well described with the first-order kinetic model, and the elimination half-life was 9.3 (for PET) and 45 h (for PLA). A longer excretion period of PLA may be related to its potential to break down in the earthworms' digestive tract. This not only promotes the environmental degradation of PLA but also suggests the ecological risk caused by nanoparticles.

Microplastics identification and quantification in the composted Organic Fraction of Municipal Solid Waste

Composted Organic Fraction of Municipal Solid Waste (OFMSW) is used in agricultural soils as a source of organic matter and nutrients. Besides, its use avoids landfilling or incineration following the principles of circular economy. It is well established that source separated OFMSW is suitable for compost production, but its quality depends on their content in non-compostable materials. In this work, we selected and studied the final refined compost form five OFMSW facilities over a five-month period. The plants displayed differences in collection systems, concentration on non-desired materials, treatment technology and density of served population. The presence of plastic was studied using a separation and identification process that consisted of oxidation and flotation followed by spectroscopic identification. The results showed a concentration of plastic impurities in the 10-30 items/g of dry compost range. The concentration of small fragments and fibres (equivalent diameter < 5 mm) was in the 5-20 items/g of dry weight range and were dominated by fibres (25% of all particles <500 μm). Five polymers represented 94% of the plastic items: polyethylene, polystyrene, polyester, polypropylene, polyvinyl chloride, and acrylic polymers in order of abundance. Polyethylene was more abundant in films, polystyrene in fragments, polypropylene in filaments, and fibres were dominated by polyester. Our results showed that smaller plants, with OFMSW door-to-door collection systems produced compost with less plastic of all sizes. Compost from big facilities fed by OFMSW from street bin collection displayed the highest contents of plastics. No debris from compostable bioplastics were found in any of the samples, meaning that if correctly composted their current use does not contribute to the spreading of anthropogenic pollution. Our results suggested that the use of compostable polymers and the implementation of door-to-door collection systems could reduce the concentration of plastic impurities in compost from OFMSW.

Role-Playing Between Environmental Pollutants and Human Gut Microbiota: A Complex Bidirectional Interaction

There is a growing interest in the characterization of the involvement of toxicant and pollutant exposures in the development and the progression of several diseases such as obesity, diabetes, cancer, as well as in the disruption of the immune and reproductive homeostasis. The gut microbiota is considered a pivotal player against the toxic properties of chemicals with the establishment of a dynamic bidirectional relationship, underlining the toxicological significance of this mutual interplay. In fact, several environmental chemicals have been demonstrated to affect the composition, the biodiversity of the intestinal microbiota together with the underlining modulated metabolic pathways, which may play an important role in tailoring the microbiotype of an individual. In this review, we aimed to discuss the latest updates concerning the environmental chemicals–microbiota dual interaction, toward the identification of a distinctiveness of the gut microbial community, which, in turn, may allow to adopt personalized preventive strategies to improve risk assessment for more susceptible workers.

Short-term effects of polyethene and polypropylene microplastics on soil phosphorus and nitrogen availability

Microplastics are an emerging threat to soils, but little is known about their effects on soil nitrogen (N) and phosphorus (P) cycling. In this study, a three-month soil incubation experiment has been conducted to analyze the effects of polyethene (PE) and polypropylene (PP) microplastics in sizes of 0-1 mm and 1-5 mm on soil available phosphate, nitrate, and ammonium contents under different fertilization regimes. Soil phosphorus and nitrogen availability were continuously determined in-situ by ion-exchange membrane method during the incubation. Microplastic surface chemical composition and the specific surface area were analyzed by FTIR and BET, respectively. The 16s rRNA sequencing of soil bacterial communities as well as soil pH have been determined after the incubation. The results showed that the presence of microplastics could significantly (P < 0.05) decrease soil available phosphate content from 122.61 mg P L^-1 to 63.43 mg P L^-1. The addition of PP microplastics could significantly increase soil available ammonium content from 0.94 mg N L^-1 to 1.53 mg N L^-1. Since microplastics had undetectable specific surface area and limited effects on soil microorganisms, adsorption and microorganism alteration functions might not be the main drivers of microplastic effects on soil phosphorus and nitrogen.

Interactive effects of environmental microplastics and 2,4-dichlorophenoxyacetic acid (2,4-D) on the earthworm Eisenia andrei

Given the wide use of plastic and pesticides in agriculture, microplastics (MP) and the herbicide 2,4 dichloro-phenoxy-acetic acid (2-4-D) can be present simultaneously in soil. Nevertheless, little is known about their combined toxicity. In this study, Eisenia andrei was exposed to environmental MP (100 µg kg^-1 soil) and 2,4-D (7 mg kg^-1 soil) for 7 and 14 days. Bioaccumulation, genotoxicity, oxidative stress and gene expression level were assessed. Results revealed that MP increased 2,4-D bioaccumulation in earthworms. Simultaneous exposure to both these pollutants caused a significant reduction in lysosomal membrane stability (LMS) and an increase in micronuclei (MNi) frequency. Biochemical analysis revealed oxidative alterations in earthworms exposed to all treatments; being very pronounced in earthworms exposed to the mixture in terms of increase in glutathione-S-Transferase (GST), catalase (CAT) and malondialdehydes accumulation (MDA). Furthermore, an up-regulation in cat and gst expression level was recorded in worms exposed to single or mixture treatment, except MP in case of gst. Our data highlight the toxicity of the combined exposure to MP and 2,4-D and afford new insights into the potential ecological risks posed by MP in terrestrial ecosystems.

Analyzing microplastics with Nile Red: Emerging trends, challenges, and prospects

The development and applications of effective analytical techniques for identification and quantification of microplastics in diverse spheres are increasing in the scientific arena. Nile Red (NR) staining has progressed as a low-cost, simple-to-use approach for analyzing the environmental impact of a wide spectrum of microplastics (e.g., ≥ 3 µm - ≤ 5 mm; polyethylene, polypropylene, and polyvinyl chloride etc.). Given the recent surge of research into this methodology, it is critical to examine the findings and present future directions. Herein, we review accomplishments to date of the current protocols describing the sample preparation, staining and fluorescence conditions, contamination measures, and data analysis based on 56 field observations focusing on microplastic pollution and NR staining technique. Additionally, we discuss the challenges in current analyses towards standardization and recommendations related to it. Finally, we conclude that, despite methodological discrepancies, the NR method has emerged as a viable standalone substitute for visual identification; yet not all that fluoresce with NR are microplastics, which necessitates extensive sample preparation or additional spectroscopy techniques for chemical analysis to validate the results. This article informs the reader about how the NR technique is advancing microplastic research and identifies current needs for future advancements.