Graphene-enhanced polymer composites are attracting interest due to the unique properties of graphene-related nanomaterials. However, their environmental impact, especially as sources of micro- and nanoplastics (MNPs), remains underexplored compared to conventional polymers. Therefore, comprehensive environmental risk assessments of advanced polymer nanocomposites are needed. This study assessed the toxic potential of reduced graphene oxide-enhanced polypropylene (PP-rGO) using a multi-biomarker approach, focusing on how rGO alters the ecotoxicological profile of polypropylene (PP). Terrestrial isopods were exposed for 14 days to soil mixed with PP and PP-rGO MNPs at 1% and 10% w/w, and to reduced graphene oxide (rGO) alone at 0.1% and 1% w/w. The lowest tested concentrations represent environmentally relevant levels of MNPs in soil, while the highest concentrations reflect a worst-case scenario. Organism-level toxicity was evaluated by monitoring survival, body weight change, and moulting frequency. Sublethal stress responses were evaluated in isolated isopod haemolymph using cellular and biochemical biomarkers, including haemocyte counts, haemocyte viability, and phenoloxidase-like activity. In addition, electron transport system activity, glutathione S-transferase activity, and acetylcholinesterase activity were assessed in whole-animal homogenates. At 1%, PP-rGO triggered sublethal stress without affecting survival. At 10%, it caused low toxicity and altered haemocyte profiles. rGO induced high toxicity at 1%, impacting survival and moulting. PP alone caused stress only at 10%. Embedding rGO in a polymer matrix reduces its toxicity compared to free rGO but still enhances PP effects. These findings highlight the need for thorough environmental risk assessment of nanocomposites.

Despite the widespread presence of cigarette butts in the environment, the potential toxicological effects posed by microplastics (MPs) derived from them remain poorly understood. In this study, we compared the effects of MPs from conventional cigarette butts (cellulose acetate) and heated tobacco devices (cellulose acetate and polylactic acid film), the latter being under-investigated. We also compared their effects before and after UV-accelerated aging. The most notable change in chemical properties of MPs following UV aging was a significant reduction in nicotine content, which fell below detection limits, while elemental composition remained largely unchanged. The surface of particles remained unchanged, but the size of heated tobacco devices cellulose acetate MPs also fragmented to smaller sizes. The effects were evaluated using Daphnia magna (48 h immobilization; 1, 10, 100 mg L-1), Lemna minor (168 h growth inhibition; 100 mg L-1), protozoan Tetrahymena thermophila (24 h, 100 mg L-1) and in vitro cytotoxicity test model using A549 human lung cells (24 h, 100 mg L-1). Toxicity tests revealed no significant effects of all types of MPs on any of used test models. UV-aging of MPs did not change the toxicological profile. Our findings showed that cigarette butt-derived MPs represent a complex mixture of polymers, residual nicotine, and metals. Comparing this research to previous studies suggests that MPs from different cigarette brands vary in chemical composition and toxicological potential.

With regard to the sustainability of plastics, the role of plastic additives can no longer be ignored or underestimated, as additives may play a more significant role in the biological impact of plastics than anticipated. Plasticizers form the largest group of additives, and phthalates are the best-known plasticizers. To date, several low molecular weight phthalates are restricted/banned due to health and environmental hazards, so various substitute plasticizers, especially high molecular weight phthalates such as di(2-propylheptyl) phthalate (DPHP), in particular, are increasingly used. However, the hazard data of DPHP, particularly those for environmental organisms, are very limited. The current study investigated the potential long-term impact of substitute plasticizer DPHP in comparison to that of the previously dominant di(2-ethylhexyl) phthalate (DEHP). As model organisms, aquatic arthropods, such as crustacean Daphnia magna, and terrestrial arthropods, such as mealworm Tenebrio molitor and woodlice Porcellio scaber, were chosen. Exposure to phthalates was carried out via 0.5-1000 mg DPHP/DEHP/kg-spiked sediment, soil, or food, depending on the assay. Solvents were used in spiking, and results are presented in relation to the solvent controls. For D. magna, both phthalates induced delayed reproduction in F0 and F1 generations and a smaller parental size at 25 mg/kg. The reduced number of broods (DPHP) and fertility (DEHP) was recorded in the F1 generation. For T. molitor, no adverse effects on organism mass, moult, or development were recorded during 8 week exposure at up to 1000 mg/kg food. For P. scaber, a 2-week exposure to phthalates did not affect immunity but triggered biochemical responses. DEHP exposure induced potential neurotoxicity (increase in acetylcholinesterase) above 50 mg/kg and detoxification (increase in glutathione S-transferase) above 100 mg/kg, simultaneously reducing metabolic activity. DPHP induced detoxification processes, even at 5 mg/kg. In conclusion, DPHP toxicity induction potential was comparable to that of DEHP, indicating that more hazard data are needed to ensure that DPHP is not a regrettable substitution to DEHP.

Microplastic (MPs) contamination in terrestrial ecosystems is an emerging concern, with indirect impacts on soil biota often exceeding direct toxicity. This study examined direct and indirect effects of MPs from agricultural mulch films—low-density polyethylene (LDPE), polybutylene adipate terephthalate (PBAT) and starch bioplastics (starch-based)—on the soil isopod Porcellionides pruinosus. We conducted comparative feeding and mesocosm experiments under environmentally realistic conditions. We analysed toxicological endpoints like survival and weight change, and stress-related markers like total haemocyte count, differential haemocyte count, phenoloxidase PO-like activity, enzymatic assays of acetylcholinesterase, glutathione S-transferase, and electron transport system activity. No acute toxicity was observed; however, soil exposure had a more pronounced effect on P. pruinosus, confirming that indirect impacts via altered soil conditions are stronger than direct dietary exposure. Notably, only bio-based MPs triggered changes in cellular and biochemical stress parameters, while fossil-based MPs had no observable effect. The stress response of P. pruinosus in mesocosm experiments aligned with shifts in microbial respiration, suggesting that soil-mediated effects play a dominant role in organismal stress. These findings underscore the importance of considering indirect pathways in MP toxicity assessments and highlight the suitability of terrestrial isopods for integrating diverse toxicological endpoints and stress markers in both laboratory and mesocosm settings.

Plastic pollution is a growing environmental concern. Bioplastics, in particular, biodegradable plastics, are increasingly promoted as sustainable alternatives to regular plastics yet their impact on the environment is currently still unresolved. Previous studies show that the general public’s understanding of these materials remains limited, particularly among younger populations. This study thus investigated the knowledge, perceptions, attitudes, and behavioral intentions of Slovenian lower and upper secondary school students regarding regular plastics, bioplastics, and biodegradable plastics. A questionnaire was administered to 697 students (12–19 years old) from schools in Ljubljana and Kamnik during the 2023/24 and 2024/25 school years. The survey assessed knowledge of bioplastics and biodegradable plastics, attitudes towards their usefulness, perceptions of their environmental impacts, evaluations of alternative packaging materials, and willingness to pay for more sustainable products as an indicator of behavioral intention. Overall knowledge scores were relatively low, indicating limited understanding of bioplastics and biodegradable plastics among students (average score: 36% of the maximum score on the five-item knowledge scale). Upper secondary students demonstrated significantly greater knowledge than lower secondary students, and female students achieved higher knowledge scores than male students. Students generally perceived bioplastics, biodegradable plastics, and paper as more environmentally beneficial than regular plastics, tin, and glass packaging. Older students and female students also expressed more favorable attitudes towards sustainable materials. Willingness to pay for environmentally friendly products was moderate and positively associated with knowledge. These findings reveal important knowledge gaps and may provide useful information for the development of educational activities addressing plastic materials and their environmental implications, as well as students’ attitudes, perceptions, and behavioral intentions towards sustainable alternatives.

Sex-dependent variation in immune responses in arthropods is well established in cases of microbial infection or parasitism but remains less explored under environmental stress. In this study we examined whether the sex of terrestrial isopods Porcellio laevis affects their immune response to soil microplastic (MP) exposure. Animals were exposed for 14 days to polypropylene MPs at 0.05%, 0.5%, and 5% (w/w soil), and immune parameters, including total haemocyte count, haemocyte viability, phenoloxidase (PO)-like activity, and haemolymph protein content, were assessed alongside survival and growth. Overall, MP exposure induced sex-dependent alterations in immune status, with males and females exhibiting distinct response patterns: females exhibited reduced haemocyte-related parameters at specific MP concentrations, whereas males showed higher haemolymph protein levels and increased growth at the highest concentration. PO-like activity was consistently higher in females. Although not all responses were statistically significant, effect size analysis indicated medium to large sex-related differences across multiple endpoints. Most of the effects were related to the dose of MP, with changes detectable already at lower concentrations. These findings highlight the importance of incorporating sex as a biological factor in ecotoxicological studies and support the use of immune markers as sensitive indicators of sublethal environmental stress.

Cigarette filters comprise plasticised cellulose acetate, a synthetic polymer categorized as bioplastic. They represent a significant source of microplastics (MPs), in particular microfibers, and associated chemicals, yet their impact on organisms, especially soil invertebrates, is not well-studied. This research examines the effects of MPs milled from smoked (SCF-MPs) and unsmoked cigarette filters (UCF-MPs) on terrestrial invertebrates (Porcellio scaber, Tenebrio molitor) and aquatic invertebrates (Daphnia magna, Brachionus calyciflorus). SCF-MPs and UCF-MPs were found to be 9.06 ± 4.1 μm and 12.71 ± 6.82 μm in size, respectively. Both samples contained triacetin and potentially toxic metals, while SCF-MPs also contained nicotine and a larger number of trace organic compounds. While exposure to SCF-MPs or UCF-MPs (up to 1.5% MPs, w/w in soil) did not affect the survival of either terrestrial invertebrate, several physiological responses were observed. These included changes in immune parameters, energy-related biomarker levels, and altered glutathione S-transferase and acetylcholinesterase activities. Both types of MPs were acutely toxic to aquatic invertebrates, reducing the survival rates of B. calyciflorus (10 mg L-1 of either particle after 48h exposure) and D. magna (100 mg L-1 of SCF-MPs after 48h exposure). SCF-MPs generally caused more pronounced effects than UCF-MPs. This study highlights the need for effective environmental management to address both smoked and unsmoked cigarette filters.

Knowing the fate of nanoplastics in organisms is indispensable to assess the risk of these persistent environmental pollutants. We designed an in-depth study on the biodistribution of metal (europium)-doped polystyrene nanoparticles (EuPSs) in terrestrial isopods (Crustacea, Porcellio scaber) upon dietary exposure. Biodistribution of two types of spherical EuPSs, 100 nm and 300 nm, with similar Eu content and negligible dissolution of Eu ions in deionized water, was investigated. In the first step, the total Eu concentration in different body regions (gut, digestive glands and rest of the body) was measured with inductively coupled plasma mass spectrometry (ICP-MS). Next, tissue localisation of the particles was analysed using X-ray microtomography, fluorescent microscopy and laser ablation ICP-MS. In addition, scanning electron microscopy was used to check the presence of the particles in the digestive system. As the measured levels of Eu in body parts other than the gut, including the digestive gland, are negligibly low, we conclude that EuPSs do not accumulate in the body of P. scaber following dietary exposure. Based on our findings, we recommend complementing analytical and microscopic techniques with detailed physiological and anatomical knowledge of the investigated organisms before drawing any conclusions on body distribution.

Agricultural mulching films are potential sources of microplastics (MPs) in soil. As an alternative to conventional non-degradable mulching films, a variety of different biodegradable mulching films are used. However, it is not yet known whether MPs from biodegradable mulching films pose a lower risk to terrestrial invertebrates compared to MPs from conventional mulching films. In this study, the effects of MPs produced from two conventional polyethylene (PE-1 and PE-2) and two biodegradable (starch-based poly(butylene adipate co-terephthalate); PBAT-BD-1, and PBAT-BD-2) fossil-based mulching films on terrestrial crustacean woodlice Porcellio scaber and mealworm Tenebrio molitor were compared. A key finding was that no clear differences in induced responses between biodegradable and conventional MPs were detected. No adverse effects on P. scaber after two weeks and on T. molitor after four weeks of exposure were observed up to 5 % (w/w dry soil) of either MP type. However, some sublethal physiological changes in metabolic rate and immune parameters were found in P. scaber after two weeks of exposure indicating a response of organisms to the presence of MP exposure in soil. In addition, it was demonstrated that both types of MPs might affect the soil water holding capacity and pH. In conclusion, we confirmed that biodegradable MPs can induce responses in organisms hence further studies testing the environmental hazard of biodegradable MPs are justified.

Mulching films, widely used in agriculture, are a large source of microplastics (MPs) to soil. However, there is little knowledge on the long-term effects of agricultural MPs on soil invertebrates. We investigated the effects of MPs from conventional non-biodegradable, fossil-based, low-density polyethylene (PE) and biodegradable fossilbased poly(butylene adipate-coterephthalate) (starch-PBAT blend) mulching films on two generations of the mealworm Tenebrio molitor. No effects of MPs (0.005 %-5 %, w/w dry food) on mealworm development and survival were observed until the end of the experiments (12 weeks for the first generation, nine weeks for the second generation), but effects on their moulting and growth were observed. These were most evident for PE MPs (5 %, w/w), where a decrease in larval growth and moulting was noted in the first generation. On the contrary, PBAT MPs (5 %, w/w) significantly induced the growth of mealworms in the second generation. In addition, there was a non-significant trend towards increased growth at all other PBAT MP exposure concentrations. Increased growth is most likely due to the biodegradation of starch PBAT MPs by mealworms. Overall, these data suggest that PE and PBAT MPs do not induce significant effects on mealworms at environmentally relevant concentrations, but rather only at very high exposure concentrations (5 %).

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.

Synthetic fibers released from sewage sludge and tire particles released from traffic are among the most common types of microplastics in soil. In soil, microplastics may interact with chemicals, such as plant protection products used in agriculture. Most studies on the interactions of microplastics and chemicals focused on aquatic environments and only few addressed soil arthropods. To increase the understanding of the combined effects of microplastics and chemicals on soil arthropods, we studied the effects of polyester fibers and tire particles on the toxicity of the insecticide chlorpyrifos. Springtails (Folsomia candida) and woodlice (Porcellio scaber) were exposed in Lufa 2.2 soil to a range of chlorpyrifos concentrations (0.0088-0.8 and 0.2-3.9 mg kg(-1) dry soil, respectively) without or with 0.05 % w/w ("low") or 0.5 % w/w ("high") of microplastics. Tire particles reduced the lethality of chlorpyrifos to springtails (LC50 = 0.13-0.14 mg kg(-1) dry soil) and isopods (LC50 = 1.6 mg kg(-1) dry soil) by a factor of 2- > 2.5 and the chlorpyrifos-induced inhibition of acetylcholinesterase (AChE) activity and changes in electron transfer system (ETS) activity in P. scaber by a factor of 2-4. Polyester fibers reduced the chlorpyrifos-induced inhibition of AChE activity by a factor of 2 and increased (ETS) activity in P. scaber by a factor of >3. The fibers did not affect the toxicity of chlorpyrifos to the survival of P. scaber or the survival and reproduction of F. candida. These results indicate that the bioavailability of chlorpyrifos may be decreased by microplastics, especially by tire particles. This study shows the importance of applying a mixture toxicity approach for understanding the threats of microplastics to soil, but also suggests that the organism and the endpoints chosen are crucial for the interpretation of the effects of combined exposures to microplastics and chemicals.

The terrestrial crustacean Porcellio scaber is an established test organism in environmental research. We analysed the haemolymph proteome of P. scaber using a classical proteomic approach based on one-dimensional gel electrophoresis and tandem mass spectrometry. Using a publicly available protein database and our P. scaber transcriptome data, we have identified 76 proteins involved in cytoskeleton formation, protein degradation, vesicular transport, genetic information processing, detoxification, carbohydrate and lipid metabolism reflecting haemocyte metabolic activity, active intracellular transport, and intercellular communication. Compared with the data reported for other crustaceans, 28 of these P. scaber proteins have been linked to its immunity, among them hemocyanin, α-2-macroglobulin, phenoloxidase 3, superoxide dismutase, glutathione S-transferase, haemolymph clottable protein, and histones H4 and H2B. Our results thus provide a firm base for studying the innate immune response of P. scaber at the level of the haemolymph proteome. This knowledge is of particular importance in ecotoxicity studies with various environmental stressors where understanding physiological changes is important to reveal possible modes of action.

Kopenski enakonožci vrste Porcellio scaber so v naravnem okolju izpostavljeni številnim patogenom in parazitom, ki lahko pri gostitelju povzročijo poškodbe tkiv ter vplivajo na imunokompetenco in fitnes organizma. Bakterijska okužba povzroči aktivacijo mehanizmov prirojene imunosti, kot so fagocitoza, tvorba reaktivnih kisikovih in dušikovih zvrsti, aktivnost antioksidativnih encimov, nodulacija ter proces melanizacije. Molekularni vzorci patogenov oziroma mikrobov ter s patogenezo povezane poškodbe pri gostitelju sprožijo prepisovanje genov v celicah hemolimfe, tj. hemocitih, ki opravljajo pomembno funkcijo mediatorjev imunskega odgovora. V aktualni raziskavi smo preučevali spremembe v izražanju genov ob simptomatski bakterijski okužbi z Rhabochlamydia porcellionis ter jih primerjali z asimptomatskimi oziroma zdravimi P. scaber. Iz hemolimfe (hemocitov) asimptomatskih in simptomatskih živali smo izolirali celokupno RNA, jo prepisali v cDNA ter z metodo RT-qPCR določili relativno izražanje izbranih genov, povezanih z imunostjo (Toll4, Dscam, MyD88, Cat, MnSod, CypG, A2m, Atg5 in Nos). Ugotovili smo značilne spremembe v izražanju izbranih genov, kar kaže na njihovo vlogo v imunskem odgovoru P. scaber v primeru bakterijske okužbe, dodatno pa smo z biokemijskimi metodami dokazali povečano aktivnost encima alfa-2-makroglobulin ter mejno značilno povišanje encima katalaza. Na podlagi rezultatov lahko zaključimo, da preučevani geni predstavljajo molekularne označevalce za imunski odziv, ki jih je moč uporabiti v različnih okoljskih raziskavah.

The presence of microplastics (MPs) in the environment has raised many concerns, and therefore approaches and technologies to remove them in situ are of high interest. In this context, we investigated the interactions between polyethylene MPs (fragments with a mean size of 149 ± 75 μm) and an aquatic floating macrophyte Lemna minor in order to assess its potential use for in situ phytoremediation. We first investigated the long-term effects of a high (100 mg/L = 9600 MPs/L), but still environmentally relevant concentration of MPs on L. minor. Subsequently bioadhesion of MPs was studied and the number and strength of MPs adhering to plant biomass were assessed. MPs did not adversely affect various parameters of plants (e.g., specific growth rate, chlorophyll contents, total antioxidant capacity, electron transport system activity, and contents of energy-rich molecules) throughout the duration of the experiment (12 weeks), except for the first week of the experiment, when protein content and total antioxidant capacity were affected. On the other hand, MPs affected the root length of L. minor during the first eight weeks of the experiment, while further exposure resulted in a decrease in the effects, indicating the ability of L. minor to tolerate the presence of MPs for a long period of time. MPs adhered rapidly to the plant biomass and the average percentages of strongly and weakly adhered particles were 6.5% and 20.0%, respectively, of the total MPs applied. In summary, results of this study suggest that L. minor can tolerate hotspot concentrations of MPs and can collect MPs from the water surface. Therefore, phytoremediation using floating plants could be considered as a potential method for in situ removal of MPs from the aquatic environment.

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.

The COVID-19 pandemic has increased the use of disposable plastics, including medical masks, which have become a necessity in our daily lives. As these are often improperly disposed of, they represent an important potential source of microplastics in the environment. We prepared microplastics from polypropylene medical masks and characterised their size, shape, organic chemical leaching, and acute toxicity to the planktonic crustacean Daphnia magna. The three layers of the masks were separately milled and characterised. Each of the inner frontal, middle filtering, and outer layers yielded different types of microplastics: fibres were obtained from the inner and outer layer, but irregular fragments from the middle layer. The shape of the obtained microplastics differed from the initial fibrous structure of the intact medical mask layers, which indicates that the material is deformed during cryo-milling. The chemical compositions of plastics-associated chemicals also varied between the different layers. Typically, the inner layer contained more chemicals related to antimicrobial function and flavouring. The other two layers also contained antioxidants and their degradation products, plasticisers, cross-linking agents, antistatic agents, lubricants, and non-ionic surfactants. An acute study with D. magna showed that these microplastics do not cause immobility but do physically interact with the daphnids. Further long-term studies with these microplastics are needed using a suite of test organisms. Indeed, studies with other polypropylene microplastics have shown numerous adverse effects on other organisms at concentrations that have already been reported in the environment. Further efforts should be made to investigate the environmental hazards of polypropylene microplastics from medical masks and how to handle this new source of environmental burden.

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.