Exploring the co-exposure effects of environmentally relevant microplastics and an estrogenic mixture on the metabolome of the Sydney rock oyster.

In aquatic environments the concurrent exposure of molluscs to microplastics (MPs) and estrogens is common, as these pollutants are frequently released by wastewater treatment plants into estuaries. Therefore, this study aimed to evaluate the independent and co-exposure impacts of polyethylene microplastics (PE-MPs) and estrogenic endocrine-disrupting chemicals (EEDCs) at environmentally relevant concentrations on polar metabolites and morphological parameters of the Sydney rock oyster. A seven-day acute exposure revealed no discernible differences in morphology; however, significant variations in polar metabolites were observed across oyster tissues. The altered metabolites were mostly amino acids, carbohydrates and intermediates of the Kreb's cycle. The perturbation of metabolites were tissue and sex-specific. All treatments generally showed an increase of metabolites relative to controls - a possible stimulatory and/or a potential hormetic response. The presence of MPs impeded the exposure of adsorbed and free EEDCs potentially due to the selective feeding behaviour of oysters to microplastics, favouring algae over similar-sized PE-MPs, and the formation of an eco/bio-corona involving faeces, pseudo-faeces, natural organic matter, and algae.

Effects and molecular mechanisms of polyethylene microplastic oxidation on wheat grain quality.

Polyethylene microplastics (PE MPs) are the main MPs in agricultural soils and undergo oxidation upon environmental exposure. However, the influence of MP oxidation on phytotoxicity (especially for crop fruit) is still limited. This study aimed to explore the effect of PE MP oxidation on crop toxicity. Herein, a combination of plant phenotyping, metabolomic, and transcriptomic approaches was used to evaluate the effects of low-oxidation PE (LOPE) and high-oxidation PE (HOPE) on wheat growth, grain quality, and related molecular mechanisms using pot experiments. The results showed that HOPE induced a stronger inhibition of wheat growth and reduction in protein content and mineral elements than LOPE. This was accompanied by root ultrastructural damage and downregulation of carbohydrate metabolism, translation, nutrient reservoir activity, and metal ion binding gene expression. Compared with HOPE, LOPE activated a stronger plant defense response by reducing the starch content by 22.87 %, increasing soluble sugar content by 44.93 %, and upregulating antioxidant enzyme genes and crucial metabolic pathways (e.g., starch and sucrose, linoleic acid, and phenylalanine metabolism). The presence of PE MPs in the environment exacerbates crop growth inhibition and fruit quality deterioration, highlighting the need to consider the environmental and food safety implications of MPs in agricultural soils.

Combined toxicity of polyethylene microplastics and nickel oxide nanoparticle on earthworm (Eisenia andrei): oxidative stress responses, bioavailability and joint effect.

The co-occurrence of heavy metals and microplastics (MPs) is an emerging issue that has attracted considerable attention. However, the interaction of nickel oxide nanoparticle (nano-NiO) combined with MPs in soil was poorly researched. Here, experiments were conducted to study the influence of nano-NiO (200 mg/kg) and polyethylene (PE) MPs with different concentrations (0.1, 1, and 10%) and sizes (13, 50, and 500 µm) on earthworms for 28 days. Compared to control, the damage was induced by PE and nano-NiO, which was evaluated by biomarker Integrated Biomarker Response index: version 2 (IBRv2) based on six biomarkers including SOD, POD, CAT, MDA, AChE, Na+/K+-ATPase and cellulase. The majority of the chosen biomarkers showed significant but complicated responses with increasing contaminant concentrations after 28 days of exposure. Moreover, the joint effect was assessed as antagonism by the effect addition index (EAI). Overall, this work expands our understanding of the combined toxicity of PE and nano-NiO in soil ecosystems.

Ecotoxicological effects of polyethylene microplastics and lead (Pb) on the biomass, activity, and community diversity of soil microbes.

Microplastics and heavy metals are ubiquitous and persistent contaminants that are widely distributed worldwide, yet little is known about the effects of their interaction on soil ecosystems. A soil incubation experiment was conducted to investigate the individual and combined effects of polyethylene microplastics (PE-MPs) and lead (Pb) on soil enzymatic activities, microbial biomass, respiration rate, and community diversity. The results indicate that the presence of PE-MPs notably reduced soil pH and elevated soil Pb bioavailability, potentially exacerbated the combined toxicity on the biogeochemical cycles of soil nutrients, microbial biomass carbon and nitrogen, and the activities of soil urease, sucrase, and alkaline phosphatase. Soil CO2 emissions increased by 7.9% with PE-MPs alone, decreased by 46.3% with single Pb, and reduced by 69.4% with PE-MPs and Pb co-exposure, compared to uncontaminated soils. Specifically, the presence of PE-MPs and Pb, individually and in combination, facilitated the soil metabolic quotient, leading to reduced microbial metabolic efficiency. Moreover, the addition of Pb and PE-MPs modified the composition of the microbial community, leading to the enrichment of specific taxa. Tax4Fun analysis showed the effects of Pb, PE-MPs and their combination on the biogeochemical processes and ecological functions of microbes were mainly by altering amino acid metabolism, carbohydrate metabolism, membrane transport, and signal transduction. These findings offer valuable insights into the ecotoxicological effects of combined PE-MPs and Pb on soil microbial dynamics, reveals key assembly mechanisms and environmental drivers, and highlights the potential threat of MPs and heavy metals to the multifunctionality of soil ecosystems.

Effects of polyethylene and biodegradable microplastics on the physiology and metabolic profiles of dandelion.

Biodegradable plastics, such as poly(butylene adipate terephthalate) (PBAT) and polylactic acid (PLA), are potential alternatives to conventional polyethylene (PE), both of which are associated with the production of microplastics (MPs). However, the toxicity of these compounds on medicinal plants and their differential effects on plant morphophysiology remain unclear. This study supplemented soils with MPs sized at 200 µm at a rate of 1% w/w and incubated them for 50 days to investigate the impact of MPs on the growth and metabolites of dandelion (Taraxacum mongolicum Hand.-Mazz.). The results demonstrated that the investigated MPs decreased the growth of dandelion seedlings, induced oxidative stress, and altered the activity of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase). Based on the comprehensive toxicity assessment results, the ecological toxicity was in the following order: PE MPs > PBAT MPs > PLA MPs. Metabolomics analyses revealed metabolic reprogramming in dandelion plants, leading to the enrichment of numerous differentially accumulated metabolites (DAMs) in the leaves. These pathways include carbohydrate metabolism, energy metabolism, and biosynthesis of secondary metabolites, suggesting that dandelions respond to MP stress by enhancing the activity of sugar, organic acid, and amino acid metabolic pathways. In addition, phenolic acids and flavonoids are critical for maintaining the balance in the antioxidant defense system. Our results provide substantial insights into the toxicity of biodegradable MPs to plants and shed light on plant defense and adaptation strategies. Further assessment of the safety of biodegradable MPs in terrestrial ecosystems is essential to provide guidance for environmentally friendly management.

Marine degradation and ecotoxicity of conventional, recycled and compostable plastic bags.

Plastic bags are currently a major component of marine litter, causing aesthetical nuisance, and undesirable effects on marine fauna that ingest them or are entangled. Plastic litter also rises concern on the ecotoxicological effects due to the potential toxicity of the chemical additives leached in aquatic environments. Conventional plastic bags are made of polyethylene, either from first use or recycled, but regulations restricting single-use plastics and limiting lightweight carrier bags (<50 µm thickness) have fostered the replacement of thin PE bags by compostable materials advertised as safer for the environment. In this study, we assess the degradation of commercially available plastic bags in marine conditions at two scales: aquariums (60 days) and outdoors flow-through mesocosm (120 days). Strength at break point and other tensile strength parameters were used as ecologically relevant endpoints to track mechanical degradation. Ecotoxicity has been assessed along the incubation period using the sensitive Paracentrotus lividus embryo test. Whereas PE bags did not substantially lose their mechanical properties within the 60 d aquarium exposures, compostable bags showed remarkable weight loss and tensile strength decay, some of them fragmenting in the aquarium after 3-4 weeks. Sediment pore water inoculum promoted a more rapid degradation of compostable bags, while nutrient addition pattern did not affect the degradation rate. Longer-term mesocosms exposures supported these findings, as well as pointed out the influence of the microbial processes on the degradation efficiency of compostable/bioplastic bags. Compostable materials, in contrast toPE, showed moderate toxicity on sea-urchin larvae, partially associated to degradation of these materials, but the environmental implications of these findings remain to be assessed. These methods proved to be useful to classify plastic materials, according to their degradability in marine conditions, in a remarkably shorter time than current standard tests and promote new materials safer for the marine fauna.

Ecotoxicity evaluation using the avoidance response of the oribatid mite Oppia nitens (Acari: Oribatida) in bioplastics, microplastics, and contaminated Superfund field sites.

Bioplastics are considered sustainable alternatives to conventional microplastics which are recognized as a threat to terrestrial ecosystems. However, little is known about the potential ecotoxicological effects of bioplastics on soil fauna and ecosystems. The present study assessed the toxicity of microplastics [Polystyrene (PS), Polyethylene (PE)] and bioplastics [Polyvinyl alcohol (PVA), Sodium polyacrylate (NaPa) on a key soil fauna Oppia nitens, a soil oribatid mite, and investigated the ecological relevance of O. nitens avoidance response as a valuable tool for the risk assessment of contaminated soils such as the Superfund sites. Findings showed that the mites' net response indicated avoidance behavior such that in most cases as concentrations of micro- and bioplastics increased, so did the avoidance responses. The avoidance EC50 endpoints showed PS < PE < PVA < NaPa, indicating higher deleterious effects of microplastics. High toxicity of PS in soils to O. nitens at EC50 of 165 (±25) mg/kg compared to bioplastics and other known contaminants poses an enormous threat to soil. For bioplastics in this study, there were no significant avoidances at concentrations up to 16,200 mg/kg compared to PS and PE which showed avoidance responses at 300 and 9000 mg/kg respectively, implying that bioplastics might be relatively safer to soil mites compared to conventional microplastics. Also, results indicated that long-term heavy metal pollution such as in contaminated Superfund sites decreased microbial biomass; a useful bioindicator of soil pollution. Furthermore, O. nitens avoidance of heavy metals contaminated sites demonstrated the ecological relevance of avoidance response test when assessing the habitat integrity of contaminated soil. The present study further supports the inclusion of the oribatid mite, O. nitens in the ecological risk assessment of contaminants in soil.

Effect of conventional and biodegradable microplastics on earthworms during vermicomposting process.

The potential effect of microplastics is an increasingly growing environmental issue. However, very little is known regarding the impact of microplastics on the vermicomposting process. The present study explored the effect of non-biodegradable (low density polyethylene; LDPE) and biodegradable (polybutylene succinate-co-adipate; PBSA) microplastics on earthworm Eisenia fetida during vermicomposting of cow dung. For this, earthworms were exposed to different concentrations (0, 0.5, 1 and 2%) of LDPE and PBSA of 2 mm size. The cow dung supported the growth and hatchlings of earthworms, and the toxicity effect of both LDPE and PBSA microplastics on Eisenia fetida was analyzed. Microplastics decreased the body weight of earthworms and there was no impact on hatchlings. The body weight of earthworm decreased from 0 to 60th day by 18.18% in 0.5% of LDPE treatment, 5.42% in 1% of LDPE, 20.58% in 2% of LDPE, 19.99% in 0.5% of PBSA, 15.09% in 1% of PBSA and 16.36% in 2% of PBSA. The physico-chemical parameters [pH (8.55-8.66), electrical conductivity (0.93-1.02 (S/m), organic matter (77.6-75.8%), total nitrogen (3.95-4.25 mg/kg) and total phosphorus (1.16-1.22 mg/kg)] do not show much significant changes with varying microplastics concentrations. Results of SEM and FTIR-ATR analysis observed the surface damage of earthworms, morphological and biochemical changes at higher concentrations of both LDPE and PBSA. The findings of the present study contribute to a better understanding of microplastics in vermicomposting system.

Assessing genotoxic effects of plastic leachates in Drosophila melanogaster.

Plastic polymers were largely added with chemical substances to be utilized in the items and product manufacturing. The leachability of these substances is a matter of concern given the wide amount of plastic waste, particularly in terrestrial environments, where soil represents a sink for these novel contaminants and a possible pathway of human health risk. In this study, we integrated genetic, molecular, and behavioral approaches to comparatively evaluate toxicological effects of plastic leachates, virgin and oxodegradable polypropylene (PP) and polyethylene (PE), in Drosophila melanogaster, a novel in vivo model organism for environmental monitoring studies and (eco)toxicological research. The results of this study revealed that while conventional toxicological endpoints such as developmental times and longevity remain largely unaffected, exposure to plastic leachates induces chromosomal abnormalities and transposable element (TE) activation in neural tissues. The combined effects of DNA damage and TE mobilization contribute to genome instability and increase the likelihood of LOH events, thus potentiating tumor growth and metastatic behavior ofRasV12 clones. Collectively, these findings indicate that plastic leachates exert genotoxic effects in Drosophila thus highlighting potential risks associated with leachate-related plastic pollution and their implications for ecosystems and human health.

Melatonin counteracts polyethylene microplastics induced adreno-cortical damage in male albino rats.

There are various substances that can disrupt the homeostatic mechanisms of the body, defined as endocrine-disrupting chemicals (EDCs). The persistent nature of microplastics (MPs) is a cause for concern due to their ability to accumulate in food chains and widespread use, making their toxic effects particularly alarming. The potential of MPs for disrupting the endocrine system was observed in multiple tissues. Moreover, the adrenal gland is known to be extremely sensitive to EDCs, while with the effect of MPs on the adrenal gland has not previously been studied. This study aimed to highlight the potential polyethylene microplastics (PE-MPs) induced adreno-toxic effects rather than exploring the implicated mechanisms and concluding if melatonin (Mel) can afford protection against PE-MPs induced adreno-toxicity. To fulfill the goal, six groups of rats were used; control, Mel, PE-MPs (3.75 mg/kg), PE-MPs (15 mg/kg), PE-MPs (3.75 mg/kg) +Mel, and PE-MPs (15 mg/kg) +Mel. PE-MPs induced toxic changes in the adrenal cortex, which was evident by increased adrenal weight, histopathological examination, and ultrastructural changes detected by electron microscope. A reduction in serum cortisol and an increase in serum adrenocorticotropic hormone resulted from the adreno-toxic effects of PE-MPs. Mechanisms may include the reduction of steroidogenesis-related genes, as PE-MPs drastically reduce mRNA levels of StAR, Nr0b1, Cyp11A1, as well as Cyp11B1. Also, oxidative stress that results from PE-MPs is associated with higher rates of lipid peroxidation and decreased superoxide dismutase and glutathione. PE-MPs inflammatory effect was illustrated by elevated expression of IL-1ß and NF-kB, detected by immunohistochemical staining, in addition to increased expression of caspase-3 and mRNA of Bax, markers of proapoptotic activity. The impacts of PE-MPs were relatively dose-related, with the higher dose showing more significant toxicity than the lower one. Mel treatment was associated with a substantial amelioration of PE-MPs-induced toxic changes. Collectively, this study fills the knowledge gap about the MPs-induced adrenal cortex and elucidates various related toxic mechanisms. It also supports Mel's potential protective activity through antioxidant, anti-inflammatory, anti-apoptotic, and gene transcription regulatory effects.

Combined contamination of microplastic and antibiotic alters the composition of microbial community and metabolism in wheat and maize rhizosphere soil.

The widespread application of antibiotics and plastic films in agriculture has led to new characteristics of soil pollution. The impacts of combined contamination of microplastics and antibiotics on plant growth and rhizosphere soil bacterial community and metabolisms are still unclear. We conducted a pot experiment to investigate the effects of polyethylene (0.2%) and norfloxacin/doxycycline (5 mg kg-1), as well as the combination of polyethylene and antibiotics, on the growth, rhizosphere soil bacterial community and metabolisms of wheat and maize seedlings. The results showed that combined contamination caused more serious damage to plant growth than individual contamination, and aggravated root oxidative stress responses. The diversity and structure of soil bacterial community were not markedly altered, but the composition of the bacterial community, soil metabolisms and metabolic pathways were altered. The co-occurrence network analysis indicated that combined contamination may inhibit the growth of wheat and maize seedings by simplifying the interrelationships between soil bacteria and metabolites, and altering the relative abundance of specific bacteria genera (e.g. Kosakonia and Sphingomonas) and soil metabolites (including sugars, organic acids and amino acids). The results help to elucidate the potential mechanisms of phytotoxicity of the combination of microplastic and antibiotics.

Thermal hydrolysis alleviates polyethylene microplastic-induced stress in anaerobic digestion of waste activated sludge.

Microplastics are known to negatively affect anaerobic digestion (AD) of waste activated sludge. However, whether thermal hydrolysis (TH) pretreatment alters the impact of microplastics on sludge AD remains unknown. Herein, the effect of TH on the impact of polyethylene (PE) microplastics in sludge AD was investigated. The results showed that the inhibition of methane production by PE at 100 particles/g total solids (TS) was reduced by 31.4% from 12.1% to 8.3% after TH at 170 °C for 30 min. Mechanism analysis indicated TH reduced the potential for reactive oxygen species production induced by PE, resulting in a 29.1 ± 5.5% reduction in cell viability loss. In addition, additive leaching increased as a result of rapid aging of PE microplastics by TH. Acetyl tri-n-butyl citrate (ATBC) release from PE with 10 and 100 particles/g TS increased 11.5-fold and 8.6-fold after TH to 68.2 ± 5.5 µg/L and 124.0 ± 5.1 µg/L, respectively. ATBC at 124.0 µg/L increased methane production by 21.4%. The released ATBC enriched SBR1031 and Euryarchaeota, which facilitate the degradation of proteins and promote methane production. This study reveals the overestimated impact of PE microplastics in sludge AD and provides new insights into the PE microplastics-induced impact in practical sludge treatment and anaerobic biological processes.

Polyethylene microplastics alter root functionality and affect strawberry plant physiology and fruit quality traits.

Strawberry, a globally popular crop whose fruit are known for their taste and health benefits, were used to evaluate the effects of polyethylene microplastics (PE-MPs) on plant physiology and fruit quality. Plants were grown in 2-L pots with natural soil mixed with PE-MPs at two concentrations (0.2% and 0.02%; w/w) and sizes (⌀ 35 and 125 µm). Plant physiological responses, root histochemical and anatomical analyses as well as fruit biometric and quality features were conducted. Plants subjected to ⌀ 35 µm/0.2% PE-MPs exhibited the most severe effects in terms of CO2 assimilation due to stomatal limitations, along with the highest level of oxidative stress in roots. Though no differences were observed in plant biomass, the impact on fruit quality traits was severe in ⌀ 35 µm/0.2% MPs treatment resulting in a drop in fruit weight (-42%), soluble solid (-10%) and anthocyanin contents (-25%). The smallest sized PE-MPs, adsorbed on the root surface, impaired plant water status by damaging the radical apparatus, which finally resulted in alteration of plant physiology and fruit quality. Further research is required to determine if these alterations also occur with other MPs and to understand more deeply the MPs influence on fruit physio-chemistry.

Combined toxic effects of polyethylene microplastics and lambda-cyhalothrin on gut of zebrafish (Danio rerio).

Microplastics (MPs), which are prevalent and increasingly accumulating in aquatic environments. Other pollutants coexist with MPs in the water, such as pesticides, and may be carried or transferred to aquatic organisms, posing unpredictable ecological risks. This study sought to assess the adsorption of lambda-cyhalothrin (LCT) by virgin and aged polyethylene MPs (VPE and APE, respectively), and to examine their influence on LCT's toxicity in zebrafish, specifically regarding acute toxicity, oxidative stress, gut microbiota and immunity. The adsorption results showed that VPE and APE could adsorb LCT, with adsorption capacities of 34.4 mg∙g-1 and 39.0 mg∙g-1, respectively. Compared with LCT exposure alone, VPE and APE increased the acute toxicity of LCT to zebrafish. Additionally, exposure to LCT and PE-MPs alone can induce oxidative stress in the zebrafish gut, while combined exposure can exacerbate the oxidative stress response and intensify intestinal lipid peroxidation. Moreover, exposure to LCT or PE-MPs alone promotes inflammation, and combined exposure leads to downregulation of the myd88-nf-κb related gene expression, thus impacting intestinal immunity. Furthermore, exposure to APE increased LCT toxicity to zebrafish more than VPE. Meanwhile, exposure to PE-MPs and LCT alone or in combination has the potential to affect gut microbiota function and alter the abundance and diversity of the zebrafish gut flora. Collectively, the presence of PE-MPs may affect the toxicity of pesticides in zebrafish. The findings emphasize the importance of studying the interaction between MPs and pesticides in the aquatic environment.

Polyethylene, whose surface has been modified by UV irradiation, induces cytotoxicity: A comparison with microplastics found in beaches.

Microplastics, plastic particles 5 mm or less in size, are abundant in the environment; hence, the exposure of humans to microplastics is a great concern. Usually, the surface of microplastics found in the environment has undergone degradation by external factors such as ultraviolet rays and water waves. One of the characteristics of changes caused by surface degradation of microplastics is the introduction of oxygen-containing functional groups. Surface degradation alters the physicochemical properties of plastics, suggesting that the biological effects of environmentally degraded plastics may differ from those of pure plastics. However, the biological effects of plastics introduced with oxygen-containing functional groups through degradation are poorly elucidated owing to the lack of a plastic sample that imitates the degradation state of plastics found in the environment. In this study, we investigated the degradation state of microplastics collected from a beach. Next, we degraded a commercially available polyethylene (PE) particles via vacuum ultraviolet (VUV) irradiation and showed that chemical surface state of PE imitates that of microplastics in the environment. We evaluated the cytotoxic effects of degraded PE samples on immune and epithelial cell lines. We found that VUV irradiation was effective in degrading PE within a short period, and concentration-dependent cytotoxicity was induced by degraded PE in all cell lines. Our results indicate that the cytotoxic effect of PE on different cell types depends on the degree of microplastic degradation, which contributes to our understanding of the effects of PE microplastics on humans.

Effects of microplastics on microbial community structure and wheatgrass traits in Pb-contaminated riparian sediments under flood-drainage-planting conditions.

The coexistence of microplastics (MPs) and heavy metals in sediments has caused a potential threat to sediment biota. However, differences in the effects of MPs and heavy metals on microbes and plants in sediments under different sediment conditions remain unclear. Hence, we investigated the influence of polyethylene (PE) and polylactic acid (PLA) MPs on microbial community structure, Pb bioavailability, and wheatgrass traits under sequential incubation of sediments (i.e., flood, drainage, and planting stages). Results showed that the sediment enzyme activities presented a dose-dependent effect of MPs. Besides, 10 % PLA MPs significantly increased the F1 fractions in three stages by 11.13 %, 30.10 %, and 17.26 %, respectively, thus resulting in higher Pb mobility and biotoxicity. MPs altered sediment bacterial composition and structures, and bacterial community differences were evident in different incubation stages. Moreover, the co-exposure of PLA MPs and Pb significantly decreased the shoot length and total biomass of wheatgrass and correspondingly activated the antioxidant enzyme activity. Further correlation analysis demonstrated that community structure induced by MPs was mainly driven by sediment enzyme activity. This study contributes to elucidating the combined effects of MPs and heavy metals on sediment ecosystems under different sediment conditions.

Freeze-thaw aged polyethylene and polypropylene microplastics alter enzyme activity and microbial community composition in soil.

In cold regions, microplastics (MPs) in the soil undergo freeze-thaw (FT) aging process. Little is known about how FT aged MPs influence soil physico-chemical properties and microbial communities. Here, two environmentally relevant concentrations (50 and 500 mg/kg) of 50 and 500 µm polyethylene (PE) and polypropylene (PP) MPs treated soils were subjected to 45-day FT cycles (FTCs). Results showed that MPs experienced surface morphology, hydrophobicity and crystallinity alterations after FTCs. After 45-day FTCs, the soil urease (SUE) activity in control (MPs-free group that underwent FTCs) was 33.49 U/g. SUE activity in 50 µm PE group was reduced by 19.66 %, while increased by 21.16 % and 37.73 % in 500 µm PE and PP groups compared to control. The highest Shannon index was found in 50 µm PP-MPs group at 50 mg/kg, 2.26 % higher than control (7.09). Compared to control (average weighted degree=8.024), all aged MPs increased the complexity of network (0.19-1.43 %). Bacterial biomarkers of aged PP-MPs were associated with pollutant degradation. Aged PP-MPs affected genetic information, cellular processes, and disrupted the biosynthesis of metabolites. This study provides new insights into the potential hazards of MPs after FTCs on soil ecosystem in cold regions.

The combined effects of azoxystrobin and different aged polyethylene microplastics on earthworms (Eisenia fetida): A systematic evaluation based on oxidative damage and intestinal function.

Pesticides and microplastics are common pollutants in soil environments, adversely affecting soil organisms. However, the combined toxicological effects of aged microplastics and pesticides on soil organisms are still unclear. In this study, we systematically studied the toxicological effects of azoxystrobin and four different aged polyethylene (PE) microplastics on earthworms (Eisenia fetida). The purpose was to evaluate the effects of aging microplastics on the toxicity of microplastics-pesticides combinations on earthworms. The results showed that different-aged PE microplastics promoted azoxystrobin accumulation in earthworms. Meanwhile, combined exposure to azoxystrobin and aged PE microplastics decreased the body weight of earthworms. Besides, both single and combined exposure to azoxystrobin and aged PE microplastics could lead to oxidative damage in earthworms. Further studies revealed that azoxystrobin and aged PE microplastics damage the intestinal structure and function of earthworms. Additionally, the combination of different aged PE microplastics and azoxystrobin was more toxic on earthworms than single exposures. The PE microplastics subjected to mechanical wear, ultraviolet radiation, and acid aging exhibited the strongest toxicity enhancement effects on earthworms. This high toxicity may be related to the modification of PE microplastics caused by aging. In summary, these results demonstrated the enhancing effects of aged PE microplastics on the toxicity of pesticides to earthworms. More importantly, aged PE microplastics exhibited stronger toxicity-enhancing effects in the early exposure stages. This study provides important data supporting the impact of different aged PE microplastics on the environmental risks of pesticides.

Individual and combined impact of microplastics and lead acetate on the freshwater shrimp (Caridina fossarum): Biochemical effects and physiological responses.

Microplastics and heavy metals pollution is recognised as a major problem affecting aquatic ecosystems. For this reason, this study aims to assess the toxicity of different concentrations of polyethylene microplastics (PE-MPs) (0.0, 500, and 1000 µg L-1) with a mean size of 15-25 µm and lead acetate Pb(C2H3O2)2 (0.0, 2.5, and 5 mg L-1), both individually and in combination, through the exposure of the freshwater grass shrimp, Caridinia fossarum for 15 days, focusing on microplastic interaction with co-occurring contaminants. After being exposed to both contaminants, either individually or in combination, significant alterations in numerous biochemical markers were observed. Specifically, exposure to lead acetate alone resulted in significant changes across ALP, AST, ALT, LDH, GGT, and BChE enzyme activity levels indicating hepatotoxicity and neurotoxicity. Also, Pb exposure led to alterations in total antioxidant capacity, MDA, total lipids, and glycogen contents, signalling the onset of oxidative stress. Exposure to PE-MPs alone led to changes in ALP, LDH, GGT, and BChE enzyme levels, and in MDA, total lipids, and glycogen samples' contents. Remarkably, the study observed increased bioaccumulation of lead acetate in samples treated with the combination, emphasizing the synergistic impact of PE-MPs on the toxicity of lead acetate. This synergy was also evident in AST and ALT enzyme activity levels and MDA contents. This underscores the necessity for measures to address both microplastic pollution and heavy metal contamination, taking into account the synergistic behaviour of MPs in the presence of concurrent contaminants.

Chemical reactivity theory to analyze possible toxicity of microplastics: Polyethylene and polyester as examples.

Micro- and nanoplastics are widespread throughout the world. In particular, polyethylene (PE) and polyethylene terephthalate or polyester (PET) are two of the most common polymers, used as plastic bags and textiles. To analyze the toxicity of these two polymers, oligomers with different numbers of units were used as models. The use of oligomers as polymeric templates has been used previously with success. We started with the monomer and continued with different oligomers until the chain length was greater than two nm. According to the results of quantum chemistry, PET is a better oxidant than PE, since it is a better electron acceptor. Additionally, PET has negatively charged oxygen atoms and can promote stronger interactions than PE with other molecules. We found that PET forms stable complexes and can dissociate the guanine-cytosine nucleobase pair. This could affect DNA replication. These preliminary theoretical results may help elucidate the potential harm of micro- and nanoplastics.