Polyethylene microplastics increase the toxicity of chlorpyrifos to the marine copepod Acartia tonsa

Comparative assessment of microplastics and microalgae as vectors of mercury and chlorpyrifos in the copepod Acartia tonsa

Microplastics (MPs) raise concerns not only as pollutants themselves, but also due to their ability to act as vectors of pollutants adsorbed from seawater, transferring them to marine organisms. However, the relevance of MPs as carriers of pollutants compared to microalgae needs further exploration. This study compared the role of MPs (2-10 μm non-oxidized and 10-15 μm oxidized high-density polyethylene) and natural organic particles (Rhodomonas lens microalgae, MA) as carriers of mercury (Hg, 2.3 μg Hg/L) and chlorpyrifos (CPF, 1.0 μg CPF/L) to adult Acartia tonsa copepods, after 24-48 h exposure. Dose-response experiments were first performed with adult female copepods exposed to oxidized MPs (0.25-4.0 mg/L), waterborne Hg (0.01-10.0 μg/L) and Ox MPs + Hg (0.25-4.0 mg oxidized MPs/L + 0.50-8.0 μg Hg/L) for 48 h, to complement previous studies that focused on the pesticide CPF. Effects were evaluated with four replicates for physiological and reproductive responses (6 females/replicate), biochemical techniques (40 individuals/replicate) and Hg/CPF bioaccumulation measurements (1000 individuals/replicate). Copepods accumulated Hg/CPF similarly from dissolved pollutants (6204 ± 2265 ng Hg/g and 1251 ± 646 ng CPF/g) and loaded MPs (3125 ± 1389 ng Hg/g and 1156 ± 266 ng CPF/g), but significantly less from loaded MA (21 ± 8 ng Hg/g and 173 ± 80 ng CPF/g). After 24-48 h, copepods exposed to MPs + Hg/CPF showed generally greater biological effects than those exposed to dissolved Hg/CPF or to MA + Hg/CPF, although differences were not statistically significant. MA + CPF had significantly lower AChE inhibition (1073.4 nmol min-1 mg-1) and MA + Hg lower GRx induction (48.8 nmol min-1 mg-1) compared to MPs + Hg/CPF and dissolved Hg/CPF (182.8-236.4 nmol min-1 mg-1 of AChE and 74.1-101.7 nmol min-1 mg-1 of GRx). Principal component analysis suggested different modes of action for Hg and CPF.

Small microplastic ingestion by the calanoid Centropages furcatus in the Gulf of Thailand

Microplastics could be ingested by many organisms, including zooplankton, involving bioaccumulation and biomagnification mechanisms a cross food webs. The information about microplastic ingestion by zooplankton keeps increasing worldwide. However, it is still limited for particle sizes under 300 μm (small microplastics, SMPs) and in areas such as Southeast Asia, which is considered one of the hotspots for plastic debris. This study aimed to characterize the size, shape, and polymer types of the SMPs ingested by the copepod Centropages furcatus in Si Chang Island (upper Gulf of Thailand). The study spans offshore and coastal waters, with data collected across wet, intermediate, and dry seasons. Using a semi-automated technique for micro-FTIR (Fourier-transform infrared) scanning spectroscopy for particle analysis, we found ingested SMPs in all samples. A total of 750 individuals of the calanoid Centropages furcatus were analyzed, finding 309 plastic particles and an average ingestion value of 0.41 ± 0.13 particles ind-1, one of the highest recorded values. All the particles were fragments, with a predominant size under 50 μm, and polymer types as Polypropylene (PP, 71 %), followed by Ethylene-Propylene-Diene-Monomer (EPDM, 16 %) and Polyethylene (PE, 7 %). Up to 470.2 particles m-3 were estimated to be retained by this calanoid species and potentially available for trophic transfer. The effect of rainfall on SMPs ingestion was inconclusive, with a non-significant observed tendency to higher ingestion values near the coastal area than offshore area, suggesting a decrease in particle exposure due to the runoff effect. Nevertheless, future studies should increase the frequency of surveys to arrive at better conclusions.

Toxicity effects and mechanism of micro/nanoplastics and loaded conventional pollutants on zooplankton: An overview

Micro/nanoplastics in aquatic environments is a noteworthy environmental problem. Zooplankton, an important biological group in aquatic ecosystems, readily absorb micro/nanoplastics and produce a range of toxic endpoints due to their small size. This review summarises relevant studies on the effects of micro/nanoplastics on zooplankton, including combined effects with conventional pollutants. Frequently reported adverse effects include acute/chronic lethal effects, oxidative stress, gene expression, energetic homeostasis, and growth and reproduction. Obstruction by plastic entanglement and blockage is the physical mechanism. Genotoxicity and cytotoxicity are molecular mechanisms. Properties of micro/nanoplastics, octanol/water partition coefficients of conventional pollutants, species and intestinal environments are important factors influencing single and combined toxicity. Selecting a wider range of micro/nanoplastics, focusing on the aging process and conducting field studies, adopting diversified zooplankton models, and further advancing the study of mechanisms are the outstanding prospects for deeper understanding of impacts of micro/nanoplastics on aquatic ecosystem.

Developmental and biochemical markers of the impact of pollutant mixtures under the effect of Global Climate Change

This study investigates the combined impact of microplastics (MP) and Chlorpyriphos (CPF) on sea urchin larvae (Paracentrotus lividus) under the backdrop of ocean warming and acidification. While the individual toxic effects of these pollutants have been previously reported, their combined effects remain poorly understood. Two experiments were conducted using different concentrations of CPF (EC10 and EC50) based on previous studies from our group. MP were adsorbed in CPF to simulate realistic environmental conditions. Additionally, water acidification and warming protocols were implemented to mimic future ocean conditions. Sea urchin embryo toxicity tests were conducted to assess larval development under various treatment combinations of CPF, MP, ocean acidification (OA), and temperature (OW). Morphometric measurements and biochemical analyses were performed to evaluate the effects comprehensively. Results indicate that combined stressors lead to significant morphological alterations, such as increased larval width and reduced stomach volume. Furthermore, biochemical biomarkers like acetylcholinesterase (AChE), glutathione S-transferase (GST), and glutathione reductase (GRx) activities were affected, indicating oxidative stress and impaired detoxification capacity. Interestingly, while temperature increase was expected to enhance larval growth, it instead induced thermal stress, resulting in lower growth rates. This underscores the importance of considering multiple stressors in ecological assessments. Biochemical biomarkers provided early indications of stress responses, complementing traditional growth measurements. The study highlights the necessity of holistic approaches when assessing environmental impacts on marine ecosystems. Understanding interactions between pollutants and environmental stressors is crucial for effective conservation strategies. Future research should delve deeper into the impacts at lower biological levels and explore adaptive mechanisms in marine organisms facing multiple stressors. By doing so, we can better anticipate and mitigate the adverse effects of anthropogenic pollutants on marine biodiversity and ecosystem health.

Microplastics derived from plastic mulch films and their carrier function effect on the environmental risk of pesticides

Plastic film mulching can maintain soil water and heat conditions, promote plant growth and thus generate considerable economic benefits in agriculture. However, as they age, these plastics degrade and form microplastics (MPs). Additionally, pesticides are widely utilized to control organisms that harm plants, and they can ultimately enter and remain in the environment after use. Pesticides can also be sorbed by MPs, and the sorption kinetics and isotherms explain the three stages of pesticide sorption: rapid sorption, slow sorption and sorption equilibrium. In this process, hydrophobic and partition interactions, electrostatic interactions and valence bond interactions are the main sorption mechanisms. Additionally, small MPs, biodegradable MPs and aged conventional MPs often exhibit stronger pesticide sorption capacity. As environmental conditions change, especially in simulated biological media, pesticides can desorb from MPs. The utilization of pesticides by environmental microorganisms is the main factor controlling the degradation rate of pesticides in the presence of MPs. Pesticide sorption by MPs and size effects of MPs on pesticides are related to the internal exposure level of biological pesticides and changes in pesticide toxicity in the presence of MPs. Most studies have suggested that MPs exacerbate the toxicological effects of pesticides on sentinel species. Hence, the environmental risks of pesticides are altered by MPs and the carrier function of MPs. Based on this, research on the affinity between MPs and various pesticides should be systematically conducted. During agricultural production, pesticides should be cautiously selected and used plastic film to ensure human health and ecological security.

Screening of organic chemicals associated to virgin low-density polyethylene microplastic pellets exposed to the Mediterranean Sea environment by combining gas chromatography and liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry

In this work, organic chemicals associated with microplastics (MPs) exposed to a coastal anthropogenized environment for up to eight weeks have been screened for, in order to discern the (de)sorption dynamics of chemicals in the marine ecosystem. Low-density polyethylene (LDPE) pellets were studied since they represent primary MPs used by the plastic industry and a relevant input of MPs into the oceans. To maximize the coverage of chemicals that could be detected, both liquid and gas chromatography coupled to quadrupole-time-of-flight (GC-QTOF and LC-QTOF, respectively) were used. In the case of LC-QTOF, an electrospray ionization source was employed, and the compounds were investigated by combining suspect and non-target screening workflows. The GC-QTOF was equipped with an electron ionization source and compounds were screened in raw and derivatized (silylated) extracts by deconvolution and contrast to high- and low-resolution libraries. A total of 50 compounds of multifarious classes were tentatively identified. Among them, melamine and 2-ethylhexyl salicylate (EHS) were detected in the original MPs but were rapidly desorbed. Melamine was completely released into the marine environment, while EHS was partly released but a portion remained bound to the MPs. On the other hand, many other chemicals of both anthropogenic (e.g. phenanthrene or benzophenone) and natural origin (e.g. betaine and several fatty acids) accumulated onto MPs over time. Quantification of 12 unequivocally identified chemicals resulted into a total concentration of 810 μg/kg after MPs exposure for 8 weeks.

Effects of single and combined exposure of virgin or aged polyethylene microplastics and penthiopyrad on zebrafish (Danio rerio)

The interaction between pesticides and microplastics (MPs) can lead to changes in their mode of action and biological toxicity, creating substantial uncertainty in risk assessments. Succinate dehydrogenase inhibitor (SDHI) fungicides, a common fungicide type, are widely used. However, little is known about how penthiopyrad (PTH), a member of the SDHI fungicide group, interacts with polyethylene microplastics (PE-MPs). This study primarily investigates the individual and combined effects of virgin or aged PE-MPs and penthiopyrad on zebrafish (Danio rerio), including acute toxicity, bioaccumulation, tissue pathology, enzyme activities, gut microbiota, and gene expression. Short-term exposure revealed that PE-MPs enhance the acute toxicity of penthiopyrad. Long-term exposure demonstrated that PE-MPs, to some extent, enhance the accumulation of penthiopyrad in zebrafish, leading to increased oxidative stress injury in their intestines by the 7th day. Furthermore, exposure to penthiopyrad and/or PE-MPs did not result in histopathological damage to intestinal tissue but altered the gut flora at the phylum level. Regarding gene transcription, penthiopyrad exposure significantly modified the expression of pro-inflammatory genes in the zebrafish gut, with these effects being mitigated when VPE or APE was introduced. These findings offer a novel perspective on environmental behavior and underscore the importance of assessing the combined toxicity of PE-MPs and fungicides on organisms.

Occurrence, transport, and toxicity of microplastics in tropical food chains: perspectives view and way forward

Microplastics, which have a diameter of less than 5 mm, are becoming an increasingly prevalent contaminant in terrestrial and aquatic ecosystems due to the dramatic increase in plastic production to 390.7 million tonnes in 2021. Among all the plastics produced since 1950, nearly 80% ended up in the environment or landfills and eventually reached the oceans. Currently, 82-358 trillion plastic particles, equivalent to 1.1-4.9 million tonnes by weight, are floating on the ocean's surface. The interactions between microorganisms and microplastics have led to the transportation of other associated pollutants to higher trophic levels of the food chain, where microplastics eventually reach plants, animals, and top predators. This review paper focuses on the interactions and origins of microplastics in diverse environmental compartments that involve terrestrial and aquatic food chains. The present review study also critically discusses the toxicity potential of microplastics in the food chain. This systematic review critically identified 206 publications from 2010 to 2022, specifically reported on microplastic transport and ecotoxicological impact in aquatic and terrestrial food chains. Based on the ScienceDirect database, the total number of studies with "microplastic" as the keyword in their title increased from 75 to 4813 between 2010 and 2022. Furthermore, various contaminants are discussed, including how microplastics act as a vector to reach organisms after ingestion. This review paper would provide useful perspectives in comprehending the possible effects of microplastics and associated contaminants from primary producers to the highest trophic level (i.e. human health).

First assessment of anthropogenic particle ingestion in Pontellid copepods: Pontella mediterranea as a potential microplastic reservoir in the Neuston

Hyponeustonic species, living at the interface between the atmosphere and the oceans, comprise one of the most understudied and vast critical marine biotope, constantly exposed to high concentrations of anthropogenic contaminants and microplastic (MPs). Copepods of the Pontellidae family represent the primary components of this biotic assemblage worldwide, and their interaction with MPs is still unknown. We studied this interaction for the first time in Pontella mediterranea, assessing the ingestion of anthropogenic particles (APs) in 2793 individuals collected by manta trawl in the Northern Alboran Sea. We observed P. mediterranea abundances ranging from 41.67 to 1174.83 ind/m3, with a mean ingestion of 0.11 APs/ind, predominantly composed of MPs. These results confirm the low ingestion values observed for other copepod taxa. However, given its abundance, this species could retain an average of 45.15 and a maximum of 220 APs per m3 of seawater (APs/m3), mostly composed of cellulose acetate and cotton fibers. The abundances of APs were evaluated in surface (0-12 cm) and sub-surface waters (5 m depth) by combining manta trawl and Continuous Underway Fish Egg Sampler sampling. The AP abundances found (surface waters: 0.67 ± 1.04 APs/m3; subsurface waters: 3.85 ± 2.67 APs/m3) were consistent with those previously observed in the Mediterranean basin, confirming that the ingestion values observed in P. mediterranea are not due to a local accumulation of environmental MPs. Results highlight how this neustonic copepod could represent one of the largest reservoirs of APs within the upper layers of the oceans, representing an entry point for these particles within food webs. Considering the worldwide distribution and abundance of this family of copepods, the results are of environmental concern.

Microplastics increase the toxicity of mercury, chlorpyrifos and fluoranthene to mussel and sea urchin embryos

The objective of this study was to determine whether and to what extent microplastics (MPs) enhance the toxicity of pollutants as well as whether pollutant-loaded MPs act as relevant vectors of chemical pollutants. With this aim, the toxicity for mussel and sea urchin embryos of: 1) three dissolved pollutants (Pol): chlorpyrifos (CPF), fluoranthene (FLT) and mercury (Hg); 2) their mixture with Microplastics (MP + Pol); and 3) pollutant-loaded MPs (MPPol), was assessed. Analyses of CPF, FLT and Hg were also performed to evaluate the transfer among dissolved and particulate phases. In general, the 'MP + Pol' treatments were more toxic as 48-h EC50 (μg/L) than the 'Pol' treatments for sea urchin or mussel. The 48-h and 120-h EC50s (μg/L) for sea urchin showed little variation for CPF and MP + CPF, and no clear pattern was found for FLT and MP + FLT. The performed chemical analysis in the MPPol tests indicated that desorption was the main route to explain the observed toxicity of Hg and a relevant route for CPF and FLT. This study contributes to improve the knowledge about the interactions between MPs and chemical pollutants, which is fundamental for a more realistic ecological risk assessment in aquatic ecosystems.

A critical review on the evaluation of toxicity and ecological risk assessment of plastics in the marine environment

The increasing production of plastics together with the insufficient waste management has led to massive pollution by plastic debris in the marine environment. Contrary to other known pollutants, plastic has the potential to induce three types of toxic effects: physical (e.g intestinal injuries), chemical (e.g leaching of toxic additives) and biological (e.g transfer of pathogenic microorganisms). This critical review questions our capability to give an effective ecological risk assessment, based on an ever-growing number of scientific articles in the last two decades acknowledging toxic effects at all levels of biological integration, from the molecular to the population level. Numerous biases in terms of concentration, size, shape, composition and microbial colonization revealed how toxicity and ecotoxicity tests are still not adapted to this peculiar pollutant. Suggestions to improve the relevance of plastic toxicity studies and standards are disclosed with a view to support future appropriate legislation.

Tributyl phosphate can inhibit the feeding behavior of rotifers by altering the axoneme structure, neuronal coordination and energy supply required for motile cilia

Organophosphorus flame retardants (OPFRs) are frequently detected in aquatic environments and can potentially amplify the food chain, posing a potential risk to organisms. Marine invertebrates have primitive nervous systems to regulate behavior, but how they respond to OPFRs that are potentially neurotoxic substances is unclear. This study assessed changes in the feeding behavior of rotifer Brachionus plicatilis exposed to alkyl OPFRs tributyl phosphate (TnBP) (0.376 nM, 3.76 and 22.53 µM) to elucidate the mechanism of behavioral toxicity. TnBP at 22.53 μM reduced the ingestion and filtration rates of rotifers for Chlorella vulgaris and Phaeocystis globosa in a 24-h test and altered rotifer-P. globosa population dynamics in 15-d coculture. Ciliary beat frequency was also reduced, and the expression of genes encoding the cilia axoneme was downregulated. TnBP could inhibit rotifer acetylcholinesterase activity by binding this protein and reduce the expression of the exocytotic membrane protein syntaxin-4, suggesting a disorder in nervous regulation of cilia beat. Moreover, TnBP induced abnormal shape and dysfunction of mitochondria, which caused insufficient energy required for ciliary movement. This study revealed diverse neurotoxicity mechanisms of TnBP, particularly as a potentially competing acetylcholinesterase ligand for aquatic invertebrates. Our research also provides a meaningful reference for OPFR-induced behavioral toxicity assessments.

Single and combined effects of polyethylene microplastics and acetochlor on accumulation and intestinal toxicity of zebrafish (Danio rerio)

The co-exposure of microplastics (MPs) and other contaminants has aroused extensive attention, but the combined impacts of MPs and pesticides remain poorly understood. Acetochlor (ACT), a widely used chloroacetamide herbicide, has raised concerns for its potential bio-adverse effects. This study evaluated the influences of polyethylene microplastics (PE-MPs) for acute toxicity, bioaccumulation, and intestinal toxicity in zebrafish to ACT. We found that PE-MPs significantly enhanced ACT acute toxicity. Also, PE-MPs increased the accumulation of ACT in zebrafish and aggravate the oxidative stress damage of ACT in intestines. Exposure to PE-MPs or/and ACT causes mild damage to the gut tissue of zebrafish and altered gut microbial composition. In terms of gene transcription, ACT exposure triggered a significant increase in inflammatory response-related gene expressions in the intestines, while some pro-inflammatory factors were found to be inhibited by PE-MPs. This study provides a new perspective on the fate of MPs in the environment and on the assessment of the combined effects of MPs and pesticides on organisms.

Laboratory Studies about Microplastic Aging and Its Effects on the Adsorption of Chlorpyrifos

The constant change in microplastics (MP) due to exposure to environmental conditions leads to physical and chemical changes that enhance their ability to transport other pollutants, increasing the concern about their widespread presence in the environment. This work aimed to simulate the aging process of six MP (polyamide 6, unplasticized polyvinyl chloride, low-density polyethylene, polystyrene, polyethylene-co-vinyl acetate, polypropylene) in freshwater and seawater ecosystems at laboratory scale and evaluate its effects through optical microscope observation, Fourier transform infrared spectroscopy-Attenuated Total Reflectance (FTIR-ATR), Raman spectroscopy, and thermal gravimetric analysis (TGA). Through a combined experimental study of aged MP, the degradation by UV interaction was evidenced by the appearance of new infrared bands in the FTIR spectra assigned to ketones and hydroxyl groups. While Raman analysis and microscope images reveal the appearance of pores, wrinkles, and roughness in the MP surfaces. Variations in the temperature of the maximum weight loss of the MP were observed in the TGA analysis. The adsorption of chlorpyrifos (CPF), a common pesticide widely used in agriculture, by the pristine and aged MP was also studied. The highest affinity for CPF was observed for pristine LDPE and the lowest for PP. The batch adsorption studies revealed an increase in adsorption capacity as a consequence of the aging process for both MP. These results proved that the weathering effects caused changes in the behavior of MP, namely in the interaction with other pollutants.

Microplastics in gastrointestinal tracts of gentoo penguin (Pygoscelis papua) chicks on King George Island, Antarctica

Microplastics (< 5 mm) have been found in marine ecosystems worldwide, even in Antarctic ecosystems. In this study, the stomach and upper intestines of 14 dead gentoo penguin (Pygoscelis papua) chicks were collected and screened for microplastics on King George Island, a gateway to Antarctic research and tourism. A total of 378 microplastics were identified by Fourier-transform infrared spectroscopy, with 27.0 ± 25.3 microplastics per individual. The detected number of microplastics did not increase with the mass of penguin chicks, suggesting no permanent accumulation of microplastics. However, the concentration of microplastics was much higher (9.1 ± 10.8 microplastics per individual within the size range 100-5000 μm) than the previously reported concentration in the penguin feces, and a greater number of smaller microplastics were found. Marine debris surveys near the breeding colony found various plastic (79.3%) to be the most frequent type of beached debris, suggesting that local sources of marine plastic waste could have contributed to microplastic contamination of penguin chicks being fed by parents that forage in nearby seas. This finding confirms the presence of microplastics in an Antarctic ecosystem and suggests the need for stronger waste management in Antarctica and a standardized scheme of microplastic monitoring in this once-pristine ecosystem.

Revealing the sorption mechanisms of carbamazepine on pristine and aged microplastics with extended DLVO theory

The co-occurrence of microplastics (MPs) and organic contaminants in aquatic environment can complexify their environmental fate via sorption interactions, especially when the properties of MPs can even vary due to the aging effect. Thus, quantitatively clarifying the sorption mechanisms is required to understand their environmental impacts. This study selected popularly occurring carbamazepine (CBZ) and four types of MPs as model systems, including polyethylene, polyvinyl chloride, polyethylene terephthalate and polystyrene in their pristine and aged forms, to investigate the sorption isotherms, kinetics, and desorption. The variation of MPs during the aging process were analyzed with scanning electron microscopy, contact angle, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It was found that the aging process elevated the sorption capacity and intensified the desorption hysteresis of CBZ on MPs via increasing the surface roughness, decreasing the particle size, and altering the surficial chemistry of all MPs. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was innovatively applied hereby to calculate the interfacial free energies and revealed that the hydrophobic interaction was significantly lessened after aging for all MPs with the slightly enhanced van der Waals interaction. Then the total interfacial free energies were dropped down for all MPs, which resulted in their declined specific sorption capacity. This work reveals the sorption mechanisms of CBZ on pristine and aged MPs with XDLVO and provides a useful reference to study the sorption of other neutral organics onto MPs.

Trophic transfer of DDE, BP-3 and chlorpyrifos from microplastics to tissues in Dicentrarchus labrax

Microplastic pollution and associated chemical contaminants is a topic of growing interest. In recent years, the number of publications reporting the presence of microplastics (MPs) in marine organisms has increased exponentially. However, there is a gap in knowledge about the trophic transfer of contaminants from microplastics to animal tissues, as well as possible health effects. In this study we analyzed the trophic transfer and biomagnification of three chemical pollutants present in microplastics: dichlorodiphenyldichloroethylene (DDE-p,p'), benzophenone 3 (BP-3) and chlorpyrifos (CPS). The reference values used were concentrations found in environmental microplastics in the Canary Islands (minimum and maximum). European seabass (Dicentrarchus labrax) were fed for 60 days with 5 different treatments: A) feed; B) feed with chemical pollutants at maximum concentration; C) feed + 10 % virgin MPs; D) feed + 10 % MPs with chemical pollutants at minimum concentration; E) feed + 10 % MPs with chemical pollutants at maximum concentration. We detected trophic transfer of DDE-p,p', CPS and BP-3 from the feed (treatment B) to the muscle and liver of fish. In the case of DDE-p,p', transfer to liver and muscle was also observed in the treatments consisting of feed plus plastics with different levels of contamination (C, D and E). No effect of the experimental treatments on fish condition indices was observed.

Filtration of biopolymer PHB particles loaded with synthetic musks does not cause significant bioaccumulation in marine mussels

The role of the biopolymer polyhydroxybutyrate (PHB, <250 µm) as a vehicle of a synthetic musks mixture (celestolide, galaxolide, tonalide, musk xylene, musk moskene and musk ketone) to Mytilus galloprovincialis was investigated. For 30 days, virgin PHB, virgin PHB+musks (6.82 µg g-1) and weathered PHB+musks, were daily spiked into tanks containing mussels, followed by a 10-day depuration period. Water and tissues samples were collected to measure exposure concentrations and accumulation in tissues. Mussels were able to actively filter microplastics in suspension but the concentration of the musks found in tissues (celestolide, galaxolide, tonalide) were markedly lower than the spiked concentration. Estimated Trophic Transfer Factors suggest that PHB will only play a minor role on musks accumulation in marine mussels, even if our results suggest a slightly extended persistence in tissues of musks loaded to weathered PHB.

Progress on the Effects of Microplastics on Aquatic Crustaceans: A Review

It is impossible to overlook the effects of microplastics on aquatic life as they continuously accumulate in aquatic environments. Aquatic crustaceans, as both predator and prey, play an important role in the food web and energy transmission. It is of great practical significance to pay attention to the toxic effects of microplastics on aquatic crustaceans. This review finds that most studies have shown that microplastics negatively affect the life history, behaviors and physiological functions of aquatic crustaceans under experimental conditions. The effects of microplastics of different sizes, shapes or types on aquatic crustaceans are different. Generally, smaller microplastics have more negative effects on aquatic crustaceans. Irregular microplastics have more negative effects on aquatic crustaceans than regular microplastics. When microplastics co-exist with other contaminants, they have a greater negative impact on aquatic crustaceans than single contaminants. This review contributes to rapidly understanding the effects of microplastics on aquatic crustaceans, providing a basic framework for the ecological threat of microplastics to aquatic crustaceans.

A critical review on the interaction of polymer particles and co-existing contaminants: Adsorption mechanism, exposure factors, effects on plankton species

This review considers the interaction of microplastics (MPs)/nanoplastics (NPs) and co-existing contaminants, including organic contaminants, potentially toxic elements (PTEs), and metal/metal-oxide nanoparticles. Stronger adsorption between plastic particles and co-existing contaminants can either facilitate or prevent more contaminants to enter plankton. The characteristics of MPs/NPs, such as polymer type, size, functional groups, and weathering, affect combined effects. Mixture toxicity is affected by those factors simultaneously and also affected by the type of co-existing contaminants, their concentrations, exposure time, dissolved organic matter, and surfactant. For co-exposure involving organics and metal nanoparticles, marine Skeletonema costatum generally had antagonistic effects, while marine Chlorella pyrenoidosa, Platymonas subcordiformis, and Tetraselmis chuii, showed synergistic effects. For co-exposure involving organics and PTEs, both Chlorella sp. and Microcystis aeruginosa generally demonstrated antagonistic effects. Freshwater Chlorella reinhardtii and Scenedesmus obliquus had synergistic effects for co-exposure involving metal/metal oxide nanoparticles. Zooplankton shows more unpredicted sensitivity towards the complex system. Different co-existing contaminants have different metabolism pathways. Organic contaminants could be biodegraded, which may enhance or alleviate mixture toxicity. PTEs could be adsorbed and desorbed under changing environments, and further affect the combined effects. The presence of metal/metal-oxide nanoparticles is more complicated, since some may release ion metals, increasing contaminant composition.

Multi-and transgenerational synergistic effects of glyphosate and chlorpyrifos at environmentally relevant concentrations in the estuarine rotifer Proales similis

We evaluated the multi-and transgenerational effects of single and combined environmentally relevant concentrations of glyphosate (GLY) and chlorpyrifos (CPF) in the estuarine rotifer Proales similis. The acute and chronic toxicities of GLY and CPF were determined as individual compounds and as a mixture. Rotifers were exposed to environmental concentrations of GLY (1, 10, 100, and 1000 μg/L) and CPF (0.1, 1, 5, and 10 μg/L). The main findings were as follows: (i) the LC₅₀ values were 33.91 mg/L (GLY) and 280 μg/L (CPF); (ii) the toxic unit (TU₅₀) of the mixture was 0.30, corresponding to 10.17 mg/L GLY and 83 μg/L CPF; (iii) the multigenerational study indicated that the tested concentrations of GLY and CPF, both single and combined, significantly and consistently decreased the growth rates of P. similis from the F0 to F6 generations; (iv) in most cases, GLY and CPF mixtures induced a strong synergistic effect; and (v) transgenerational effects were detected in the F4 generation, especially GLY and CPF in higher equitoxic proportions. These effects seem to dissipate in F5. Across multigeneration, a slight recovery could indicate population resilience to pollution. Our findings suggest that a mixture of GLY and CPF at environmental concentrations is likely to occur under real field conditions, increasing the risk to marine and estuarine invertebrates such as rotifers.

Influence of microplastics on the toxicity of chlorpyrifos and mercury on the marine microalgae Rhodomonas lens

The growing use of plastics, including microplastics (MPs), has enhanced their potential release into aquatic environments, where microalgae represent the basis of food webs. Due to their physicochemical properties, MPs may act as carriers of organic and inorganic pollutants. The present study aimed to determine the toxicity of polyethylene MPs (plain and oxidized) and the model pollutants chlorpyrifos (CPF) and mercury (Hg) on the red microalgae Rhodomonas lens, to contribute to the understanding of the effects of MPs and associated pollutants on marine ecosystems, including the role of MPs as vectors of potentially harmful pollutants to marine food webs. R. lens cultures were exposed to MPs (1-1000 μg/L; 25-24,750 particles/mL), CPF (1-4900 μg/L), Hg (1-500 μg/L), and to CPF- and Hg-loaded MPs, for 96 h. Average specific growth rate (ASGR, day^-1), cellular viability and pigment concentration (chlorophyll a, c2 and carotenoids) were measured at 48 and 96 h. No significant effects were observed on the growth pattern of the microalgae after 96-h exposure to plain and oxidized MPs. However, a significant increase in cell concentration was detected after 48-h exposure to plain MPs. A decrease of the ASGR was noticed after exposure to CPF, Hg and to CPF/Hg-loaded MPs, whereas viability was affected by exposure to MPs, CPF and Hg, alone and in combination. Chlorophyll a and c2 significantly decreased when microalgae were exposed to plain MPs and CPF, while both pigments significantly increased when exposed to CPF-loaded MPs. Similarly, chlorophyll and carotenoids content significantly decreased after exposure to Hg, whereas a significant increase in chlorophyll a was observed after 48-h exposure to Hg-loaded MPs, at the higher tested concentration. Overall, the presence of MPs modulates the toxicity of Hg and CPF to these microalgae, decreasing the toxic effects on R. lens, probably due to a lower bioavailability of the contaminants.

Presence and implications of plastics in wild commercial fishes in the Alboran Sea (Mediterranean Sea)

The presence of plastic in the environment has become a major problem for marine ecosystems. The identification of the global micro and mesoplastic uptake by commercial fish populations may allow for a better understanding of their impact. This study aims to determine the presence and composition of plastic in two pelagic fish (Engraulis encrasicolus and Scomber scombrus) and two demersal species (Scyliorinus canicula and Mullus barbatus) from the Alboran Sea (western Mediterranean) to quantify the relationship between plastic prevalence and the environment and feeding behavior in the selected fish species. Samples of these four fish species from sites in the Alboran Sea were studied for ingested plastics. These localized samples were also compared to published values which covered a broader geographical range. Samples from the Alboran Sea study sites showed that the predominant fiber color was black and the predominant plastic polymers were polyethylene and cellulose. At the Alboran Sea study site the highest plastic occurrence was found in S. scombrus, whereas in the published literature the highest occurrence of plastics in digestive tracts was found in E. encrasicolus. The general prevalence of marine plastic pollution and levels of macro- and micro-plastic ingested by commercial fish species in this study support the idea that quantifying plastic presence and composition may be essential to understanding potential impacts on marine ecosystems.

Microplastics: Occurrences, treatment methods, regulations and foreseen environmental impacts

Microplastics are a silent threat that represent a high degree of danger to the environment in its different ecosystems and of course will also have an important impact on the health of living organisms. It is evident the need to have effective treatments for their treatment, however this is not a simple task, this as a result of the behavior of microplastics in wastewater treatment plants due to their different types and nature, their long molecular chain, reactivity against water, size, shape and the functional groups they carry. Wastewater treatment plants are at the circumference of the release of these wastes into the environment. They often act as a source of many contaminations, which makes this problem more complex. Challenges such as detection in the current scenario using the latest analytical techniques impede the correct understanding of the problem. Due to microplastics, treatment plants have operational and process stability problems. This review paper will present the in-depth situation of occurrence of microplastics, their detection, conventional and advanced treatment methods as well as implementation of legislations worldwide in a comprehensive manner. It has been observed that no innovative or new technologies have emerged to treat microplastics. Therefore, in this article, technologies targeting wastewater treatment plants are critically analyzed. This will help to understand their fate, but also to develop state-of-the-art technologies or combinations of them for the selective treatment of microplastics. The pros and cons of the treatment methods adopted and the knowledge gaps in legislation regarding their implementation are also comprehensively analyzed. This critical work will offer the development of new strategies to restrict microplastics.

Ecotoxic effects of microplastics and contaminated microplastics - Emerging evidence and perspective

The high prevalence and persistence of microplastics (MPs) in pristine habitats along with their accumulation across environmental compartments globally, has become a matter of grave concern. The resilience conferred to MPs using the material engineering approaches for outperforming other materials has become key to the challenge that they now represent. The characteristics that make MPs hazardous are their micro to nano scale dimensions, surface varied wettability and often hydrophobicity, leading to non-biodegradability. In addition, MPs exhibit a strong tendency to bind to other contaminants along with the ability to sustain extreme chemical conditions thus increasing their residence time in the environment. Adsorption of these co-contaminants leads to modification in toxicity varying from additive, synergistic, and sometimes antagonistic, having consequences on flora, fauna, and ultimately the end of the food chain, human health. The resulting environmental fate and associated risks of MPs, therefore greatly depend upon their complex interactions with the co-contaminants and the nature of the environment in which they reside. Net outcomes of such complex interactions vary with core characteristics of MPs, the properties of co-contaminants and the abiotic factors, and are required to be better understood to minimize the inherent risks. Toxicity assays addressing these concerns should be ecologically relevant, assessing the impacts at different levels of biological organization to develop an environmental perspective. This review analyzed and evaluated 171 studies to present research status on MP toxicity. This analysis supported the identification and development of research gaps and recommended priority areas of research, accounting for disproportionate risks faced by different countries. An ecological perspective is also developed on the environmental toxicity of contaminated MPs in the light of multi-variant stressors and directions are provided to conduct an ecologically relevant risk assessment. The presented analyses will also serve as a foundation for developing environmentally appropriate remediation methods and evaluation frameworks.

Ingestion and egestion of polystyrene microplastic fragments by the Pacific oyster, Crassostrea gigas

Marine microplastics (MPs) pose a risk to human health through accumulation in maricultural organisms, particularly bivalves. Various studies have reported the presence of MP particles in Pacific oysters (Crasostrea gigas). In this study, we investigated the size-specific ingestion and egestion of polystyrene (PS) MPs by Pacific oysters. The cultivation density of C. gigas was maintained at 1 L of filtered seawater per oyster (n = 5) during the MP ingestion and egestion experiments. On exposure to 300 n/L of PS MP fragments for 7 d, 60.4% of the PS was ingested within 6 h (7.25 × 10² ± 1.36 × 10² n/indv.), and the ingestion was saturated at 12 h (1.2 × 10³ ± 2.2 × 10² n/indv.) in C. gigas. The maximum MP ingestion capacity (Ig_max) of a single Pacific oyster was 73.0 ± 16.3 n/g wet weight. Further, 62.9% of the PS MP particles were egested for 7 d from the saturated single C. gigas. Ingestion and egestion varied according to the PS MP size. In the case of <50 μm PS MP, ingestion rate was low but MP amount and net-ingestion efficiency was significantly higher than other PS MP sizes. In addition, egestion, egestion rate, and net-egestion efficiency for <50 μm PS MPs were significantly higher than other PS MP sizes. Therefore, smaller MPs (<50 μm) normally exhibit the highest ingestion and egestion rates; therefore, the 50-300 μm size fraction exhibited the highest residual possibility (particles >1000 μm were excluded). Additionally, considering the net-egestion efficiency, the most economical and efficient depuration period was 24 h. This study clarifies the size-specific MP accumulation in oysters, and the egestion results suggest that the potential risk of MPs to human health through the intake of maricultural products could be reduced by depuration.

Impact of microplastics and ocean acidification on critical stages of sea urchin (Paracentrotus lividus) early development

One of the major consequences of increasing atmospheric CO₂ is a phenomenon known as ocean acidification. This alteration of water chemistry can modulate the impact on marine organisms of other stressors also present in the environment, such as microplastics (MP). The objective of this work was to determine the combined impact of microplastic pollution and ocean acidification on the early development of Paracentrotus lividus. To study these multi-stressor impacts on development P. lividus the sea urchin embryo test (SET) was used. Newly fertilised embryos of P. lividus were exposed to a control treatment (filtered natural seawater), MP (3000 particles/mL), acidified sea water (pH = 7.6), and a combination of MP and acidification (3000 particles/mL + pH = 7.6). After 48, 72, and 96 h measurements of growth and morphometric parameters were taken. Results showed that ocean acidification and MP cause alterations in growth and larval morphology both before and after the larvae start to feed exogenously. The exposure to MP under conditions of ocean acidification did not produce any additional effect on growth, but differences were observed at the morphological level related to a decrease in the width of larvae at 48 h. Overall, changes in larvae shape observed at three key points of their development could modify their buoyancy affecting their ability to obtain and ingest food. Therefore, ocean acidification and MP pollution might compromise the chances of P. lividus to survive in the environment under future scenarios of global climate change.

A review of interactions of microplastics and typical pollutants from toxicokinetics and toxicodynamics perspective

The widespread microplastics (MPs) pollution has become a concerning environmental issue. The interactions between MPs and typical pollutants may change the bioaccumulation, and toxicity of pollutants, leading to high uncertainty in risk assessment. Still, significant gaps remain in the knowledge available to integrate these interactions in the perspectives of toxicokinetics (TK) and toxicodynamics (TD), which is also an essential part of quantitative toxicological research. This review systematically summarizes the interaction between MPs and typical pollutants in TK and TD processes. MPs can be acted as the vector or sink of pollutants to increase or decrease their bioaccumulation, and also may not affect their bioaccumulation due to no interaction. The adverse outcome pathway (AOP) framework enables novel approaches for determining the interaction between MPs and pollutants in the TD process. MPs can directly or indirectly enhance, reduce and not affect the toxicity of pollutants. A series of factors influencing the interaction in TK and TD processes are summarized, including MPs characteristics and exposure scenarios. TK-TD approach can quantitatively understand the interaction between MPs and pollutants based on the mechanism. Given the current knowledge gap in TK and TD processes, future perspectives on combined exposure research are proposed.

Microplastic pollution in the surface seawater in Zhongsha Atoll, South China Sea

The prevalence of microplastics in the marine environment has attracted extensive attention. So far, no information is known regarding the temporal and spatial variations of microplastics in Zhongsha Atoll. This study, for the first time, comprehensively investigated the occurrence and distribution of microplastics in the surface seawater in Zhongsha Atoll based on two ocean cruises. The abundances of microplastics measured in the surface seawater of Zhongsha Atoll were in the ranges of not detected (ND) to 67 items/m³, and ND to 160 items/m³ in 2019 and 2020, respectively. All microplastics detected in Zhongsha Atoll were fibers, most of which were transparent and less than 2 mm. Polyethylene terephthalate was the dominating composition of microplastics. These results suggested that sewage, surface runoff, atmospheric deposition by neighboring land, and fishing activities may be the primary pollution sources. This study provides critical information on microplastic pollution in Zhongsha Atoll for the first time, calling for more research in the management of marine plastic debris in the future.

Unpalatable Plastic: Efficient Taste Discrimination of Microplastics in Planktonic Copepods

Planktonic copepods are the most abundant animals in the ocean and key players in global biochemical processes. Recent modeling suggests that zooplankton ingestion of microplastics (MPs) can disrupt the biological carbon pump and accelerate a global loss of oceanic oxygen. Here we investigate the behavioral responses and ingestion rates of a model feeding-current generating copepod when exposed to microplastics of different characteristics by small-scale video observations and bottle incubations. We found that copepods rejected 80% of the microplastics after touching them with their mouth parts, in essence exhibiting a kind of taste discrimination. High rejection rates of microplastics were independent of polymer type, shape, presence of biofilms, or sorbed pollutant (pyrene), indicating that microplastics are unpalatable for feeding-current feeding copepods and that post-capture taste discrimination is a main sensorial mechanism in the rejection of microplastics. In an ecological context, taking into account the behaviors of planktonic copepods and the concentrations of microplastics found in marine waters, our results suggest a low risk of microplastic ingestion by zooplankton and a low impact of microplastics on the vertical exportation of fecal pellets.

Microplastics in copepods reflects the manmade flow restrictions in the Kochi backwaters, along the southwest coast of India

This baseline study on microplastics (MPs) in calanoid copepods in the Kochi backwaters (KBW), India's largest estuary system on the west coast, focuses on (a) the spatiotemporal variations of MPs with the seasonal hydrography setting, and (b) how man-made flow restrictions of a large saltwater barrage contribute to MPs in copepods and their potential to transfer to higher trophic levels. This study found that MPs in copepods in the KBW ranged from av. 0.01 ± 0.014 to 0.11 ± 0.03 no./ind. seasonally. When the saltwater barrage shutters were fully/partially closed during the Pre-monsoon/Northeast Monsoon, MPs in copepods were considerably larger (av. 0.11 ± 0.03 no./ind., and av. 0.075 ± 0.02 no./ind., respectively) as compared to the Southwest Monsoon (av. 0.03 ± 0.01 no./ind.), when the barrage shutters were fully open. This shows the potential of man-made flow restrictions to increase the bioconcentration of MPs in copepods and their possible transfer to higher trophic levels through the food chain, adding to the region's previous discovery that much higher trophic level resources are polluted with a high concentration of MPs.

Biomarker responses in zebrafish (Danio rerio) following long-term exposure to microplastic-associated chlorpyrifos and benzo(k)fluoranthene

Continuously increasing plastic production causes a constant accumulation of microplastic particles (MPs) in the aquatic environment, especially in industrialized and urbanized areas with elevated wastewater discharges. This coincides with the release of persistent organic pollutants (polycyclic aromatic hydrocarbons (PAHs), pesticides) entering limnic ecosystems. Although the assessment of potential effects of environmental pollutants sorbed to MPs under chronic exposure scenarios seems vital, data on potential hazards and risk by combined exposure to pollutants and microplastics for aquatic vertebrates is still limited. Therefore, zebrafish (Danio rerio) were exposed over 21 days to the organophosphate insecticide chlorpyrifos (CPF; 10 and 100 ng/L) and the PAH benzo(k)fluoranthene (BkF; 0.78 and 50 µg/L) either dissolved directly in water or sorbed to different MPs (irregular polystyrene, spherical polymethyl methacrylate; ≤ 100 µm), where CPF was sorbed to polystyrene MPs and BkF was sorbed to polymethyl methacrylate MPs. Contaminant sorption to MPs and leaching were documented using GC-EI-MS; potential accumulation was studied in cryosections of the gastrointestinal tract. Enzymatic biomarkers and biotransformation were measured in liver and brain. Overall, exposure to non-contaminated MPs did not induce any adverse effects. Results of fluorescence tracking, CYP1A modulation by BkF as well as changes in acetylcholinesterase activity (AChE) by CPF were less pronounced when contaminants were sorbed to MPs, indicating reduced bioavailability of pollutants. Overall, following exposure to waterborne BkF, only minor amounts of parent BkF and biotransformation products were detected in zebrafish liver. Even high loads of MPs and sorbed contaminants did not induce adverse effects in zebrafish; thus, the potential threat of MPs as vectors for contaminant transfer in limnic ecosystems can be considered limited.

Trash-to-fuel: Converting municipal waste into transportation fuels by pyrolysis

In daily life humankind is producing a significant amount of garbage, creating a great environmental concern. However, garbage consists of high amounts of carbon based materials, making it a very useful resource. An easy way to use it is to produce transport fuels obtained through pyrolysis. Multiple plastic waste materials were investigated here. Thermogravimetric analysis (TGA) of individual polymers shows that almost complete conversion could be achieved. More than 70% liquid fuels were derived from pyrolysis of polypropylene, polystyrene at 450°C, and low-/high-density polyethylene at 500°C. Using gas chromatography/high-resolution mass spectrometry (GC/HR-MS) allows studying the thermal transformation and proposing a mechanism. An examination of carbon number distribution reveals the potential of plastic liquid fuels, which can be used as an alternative to partial substitution of fossil-fuel-derived gasoline and diesel fuel and also provides a final use of polymer materials, which otherwise would be deposited on waste dumps.

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Development of pyrolysis reactor to convert municipal waste to transportation fuels

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Studying the reaction parameters of a set of different individual polymer materials

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Development of a reaction and degradation mechanism

Seeking for a perfect (non-spherical) microplastic particle - The most comprehensive review on microplastic laboratory research

In recent decades, much attention has been paid to microplastic pollution, and research on microplastics has begun to grow exponentially. However, microplastics research still suffers from the lack of standardized protocols and methods for investigation of microplastics under laboratory conditions. Therefore, in this review, we summarize and critically discuss the results of 715 laboratory studies published on microplastics in the last five years to provide recommendations for future laboratory research. Analysis of the data revealed that the majority of microplastic particles used in laboratory studies are manufactured spheres of polystyrene ranging in size from 1 to 50 µm, that half of the studies did not characterize the particles used, and that a minority of studies used aged particles, investigated leaching of chemicals from microplastics, or used natural particles as a control. There is a large discrepancy between microplastics used in laboratory research and those found in the environment, and many laboratory studies suffer from a lack of environmental relevance and provide incomplete information on the microplastics used. We have summarized and discussed these issues and provided recommendations for future laboratory research on microplastics focusing on (i) microplastic selection, (ii) microplastic characterization, and (iii) test design of laboratory research on microplastics.

Comparative role of microplastics and microalgae as vectors for chlorpyrifos bioacumulation and related physiological and immune effects in mussels

Microplastics (MP) are contaminants of concern per se, and also by their capacity to sorb dissolved chemicals from seawater, acting as vehicles for their transfer into marine organisms. Still, the role of MP as vehicles for contaminants and their associated toxicological effects have been poorly investigated. In this work we have compared the role of MP (high density polyethylene, HDPE, ≤22 μm) and of natural organic particles (microalgae, MA) as vehicle for chlorpyrifos (CPF), one of the most common pesticides found in river and coastal waters. We have compared the capacity of MP and MA to carry CPF. Then, the mussel Mytilus galloprovincialis has been exposed for 21 days to dissolved CPF, and to the same amount of CPF loaded onto MP and MA. The concentration of CPF in mussel' tissues and several physiological, energetics and immune parameters have been analyzed after 7 and 21 days of exposure. Results showed similar CPF accumulation in mussel exposed to MP and to MA spiked with CPF. This revealed that MP acted as vector for CPF in a similar way (or even to a lesser extent) than MA. After 21 days of exposure mussels exposed to MP spiked with CPF displayed similar or more pronounced biological effects than mussels exposed to dissolved CPF or to MA loaded with CPF. This suggested that the combined "particle" and "organic contaminant" effect produced an alteration on the biological responses greater than that produced by each stressor alone, although this was evident only after 3 weeks of exposure.

Microplastics reduce the bioaccumulation and oxidative stress damage of triazole fungicides in fish

Microplastics (MPs) and pesticides are typical representatives of harmful chemicals in polluted waters. It is understood that the combined toxicity may differ from that of a single toxic substance. Although their combined toxicities on aquatic organisms have practical significance and research value, they have received little attention due to their complicated interaction, and the mechanism has rarely been reported. In this paper, we designed a study to investigate the single and combined effects of polystyrene microplastics (PS-MPs) and the triazole fungicide difenoconazole on zebrafish, and to explore the mechanism of this effect. The results showed that PS-MPs could reduce the bioaccumulation of difenoconazole in zebrafish to a certain extent and alleviate the oxidative stress damage of difenoconazole in the zebrafish liver. The transcriptome and qRT-PCR data revealed the association of multiple pathways in the difenoconazole response, while the presence of PS-MPs ameliorated this effect in gene expression changes. Due to the properties of PS-MPs and the interaction between them, the toxic effect of difenoconazole when combined with PS-MPs is more prominent. These results provide a novel aspect to understand the environmental behavior of MPs and to evaluate the combined effect of MPs and pesticides on aquatic food.

The synergistic effect of microplastic and malathion exposure on fiddler crab Minuca ecuadoriensis microplastic bioaccumulation and survival

We assessed the combined effects of polyethylene microplastic (MP) and malathion (MLT) on the survival of the fiddler crab Minuca ecuadoriensis, and MP tissue bioaccumulation in four treatments following 120 h exposure: T1) Control; T2) MLT 50 mg L^-1; T3) MP 200 mg L^-1; and T4) MLT (50 mg L^-1) + MP (200 mg L^-1). The highest mortality (80%) was in T4, followed by T2 (28%) and no mortality was in T3. Higher MP bioaccumulation was observed in T4 (572 items g tissue^-1) followed by T3 (70 items g tissue^-1). Our findings indicate that the synergistic effect of MLT and MP increased M. ecuadoriensis bioaccumulative capacity and decreases survival. Thus, as MP contamination in aquatic environments is ubiquitous, our study raises a warning on the synergistic effects of MP with other environmental contaminants and serves as a baseline for further studies.

Impact of polypropylene microplastics and chemical pollutants on European sea bass (Dicentrarchus labrax) gut microbiota and health

Plastic pollution has become a global problem for marine ecosystems. Microplastics (MPs) are consumed by several marine organisms, including benthic and pelagic fish species that confuse them with food sources, thus contributing to bioaccumulation along the food chain. In addition to structural intestinal damage, ingestion of MPs represents a pathway for fish exposure to potentially hazardous chemicals, too. Most of them are endocrine disrupters, genotoxic or induce immune depression in fish. Accordingly, we assessed the combined toxicological effects of microplastics (MPs) and adsorbed pollutants by adding them to marine fish diet. European sea bass (Dicentrarchus labrax) juveniles were fed for 60 days with feeds containing polypropylene MPs, either virgin or contaminated with chemical pollutants (a blend of dichlorodiphenyldichloroethylene, chlorpyrifos, and benzophenone-3). The data demonstrated a synergic action of MPs and chemical pollutants to induce an inflammatory-like response in distal intestine of sea bass as shown by the up regulation of cytokine il-6 and tnf-α expression. Morphological analysis detected the presence of a focus of lymphocytes in anterior and posterior intestinal segments of fish fed with contaminants in the diet. With regard to microbiota, significant changes in bacterial species richness, beta diversity, and composition of gut microbiota were observed as a consequence of both pollutants and polluted MPs ingestion. These perturbations in gut microbial communities, including the reduction of beneficial lactic acid bacteria and the increase in potential pathogenic microorganism (Proteobacteria and Vibrionales), were undeniable signs of intestinal dysbiosis, which in turn confirmed the signs of inflammation caused by pollutants, especially when combined with MPs. The results obtained in this study provide, therefore, new insights into the potential risks of ingesting MPs as pollutant carriers in marine fish.

Glyphosate and glufosinate ammonium, herbicides commonly used on genetically modified crops, and their interaction with microplastics: Ecotoxicity in anuran tadpoles

The effects of glyphosate (GLY)-based and glufosinate ammonium (GA)-based herbicides (GBH and GABH, respectively) and polyethylene microplastic particles (PEMPs) on Scinax squalirostris tadpoles were assessed. Tadpoles were exposed to nominal concentrations of both herbicides (from 1.56 to 100 mg L-1) and PEMPs (60 mg L-1), either alone or in combination, and toxicity evaluated at 48 h. Acetylcholinesterase (AChE), carboxylesterase (CbE), and glutathione-S-transferase (GST) activities were analyzed at the three lowest concentrations (1.56, 3.12 and 6.25 mg L-1, survival rates >85%) of both herbicides alone and with PEMPs. Additionally, the thermochemistry of the interactions between the herbicides and polyethylene (PE) was analyzed by Density Functional Theory (DFT). The median-lethal concentration (LC50) was 43.53 mg L-1 for GBH, 38.56 mg L-1 for GBH + PEMPs, 7.69 for GABH, and 6.25 mg L-1 for GABH+PEMPs. The PEMP treatment increased GST but decreased CbE activity, whereas GBH and GABH treatments increased GST but decreased AChE activity. In general, the mixture of herbicides with PEMPs increased the effect observed in the individual treatments: the highest concentration of GBH + PEMPs increased GST activity, whereas GABH+PEMP treatments decreased both AChE and CbE activities. DFT analysis revealed spontaneous interactions between the herbicides and PE, leading to the formation of bonds at the herbicide-PE interface, significantly stronger for GA than for GLY. The experimental and theoretical findings of our study indicate that these interactions may lead to an increase in toxicity when pollutants are together, meaning potential environmental risk of these combinations, especially in the case of GA.

Multigenerational study of life history traits, bioaccumulation, and molecular responses of Pseudodiaptomus annandalei to cadmium

Metal pollution provide a substantial challenge for environmental health. This study investigated the multigeneration effects of cadmium on populations of the copepod species Pseudodiaptomus annandalei, exposed to a sublethal concentration, 40 µg/L of cadmium (Cd), over 10 generations. At the end of each generation, copepod individuals were collected to estimate fecundity, bioaccumulation, and real time qPCR quantification of selected differentially expressed genes to evaluate Cd effects and sex-specific responses of copepods across multiple generations. Our results revealed a sex-specific accumulation of Cd integrating 10 successive generations. The concentration of Cd was significantly higher (p < 0.05) in males than in females. We also observed a generational increase in Cd accumulation. Fecundity increased, with the exception of the first generation, possibly as a compensation for a decrease of copepod population size under Cd exposure. Protein expression of copepods exposed to Cd occurred in a sex-specific manner. Hemerythrin was mostly up-regulated in both copepod sexes exposed to Cd with males having the highest expression levels, while heat shock protein 70 was mostly up-regulated in males and down-regulated in female copepods, both exposed to Cd. Although copepods are known to develop adaptive mechanisms to tolerate toxic chemicals, continuous exposure to metals could lead to the bioaccumulation of metals in their offspring through maternal transfer and direct uptake from the medium over several generations. As a consequence, increased metal concentrations in copepods could result in physiological damage, reducing their fitness, and possibly compromise copepod population structures. This study showed that mortality, life history traits and molecular responses of a copepod species provided important toxicological endpoints and bio-markers for environmental risk assessments. Environmental pressure resulting from continuous exposure to persistent pollutants like Cd, could have evolutionary significance. The tendency for copepods to selectively adapt to a toxic environment through modifications, could increase their chance of survival over a long term.

Environmental Impacts of Personal Protective Clothing Used to Combat COVID- 19

Personal protective clothing is critical to shield users from highly infectious diseases including COVID-19. Such clothing is predominantly single-use, made of plastic-based synthetic fibers such as polypropylene and polyester, low cost and able to provide protection against pathogens. However, the environmental impacts of synthetic fiber-based clothing are significant and well-documented. Despite growing environmental concerns with single-use plastic-based protective clothing, the recent COVID-19 pandemic has seen a significant increase in their use, which could result in a further surge of oceanic plastic pollution, adding to the mass of plastic waste that already threatens marine life. In this review, the nature of the raw materials involved in the production of such clothing, as well as manufacturing techniques and the personal protective equipment supply chain are briefly discussed. The environmental impacts at critical points in the protective clothing value chain are identified from production to consumption, focusing on water use, chemical pollution, CO₂ emissions, and waste. On the basis of these environmental impacts, the need for fundamental changes in the business model is outlined, including increased usage of reusable protective clothing, addressing supply chain "bottlenecks", establishing better waste management, and the use of sustainable materials and processes without associated environmental problems.

Combined polystyrene microplastics and chlorpyrifos decrease levels of nutritional parameters in muscle of rainbow trout (Oncorhynchus mykiss)

Microplastic (MP) is a major contaminant in the aquatic environment. In addition to the physical threats posed by microplastic ingestion, their potential as a vector for the transport of hydrophobic pollutants is required to be adequately addressed. This study examined the effects of polystyrene microplastics individually or combined with chlorpyrifos insecticide on nutritional parameters in muscle of rainbow trout (Onchorhynchus mykiss). Fish were exposed to individual polystyrene microplastic concentrations (30 or 300 μg/L), or individual chlorpyrifos concentrations (2 or 6 μg/L), and their combination at similar concentrations of chlorpyrifos and microplastics. Results showed individual polystyrene microplastics had minimal effects on amino acid and fatty acid composition and no effect on protein contents of fish muscle. However, significant alterations in amino acid and fatty acid composition, and protein contents, were observed in combined polystyrene microplastics and chlorpyrifos groups. These findings suggested that polystyrene microplastics cause toxicity and increase the adverse effects of chlorpyrifos on the muscle of fish. This investigation provided evidence toward low nutritional value of farmed or wild fish muscle that grows in areas with high concentrations of microplastics and pesticides.

Do microplastic contaminated seafood consumption pose a potential risk to human health?

Microplastics are present in all parts of the ocean and can have deleterious effects on marine resources. The aim of this work was to map the presence of microplastics in commercial marine species such as bivalves (mussels Mytilus galloprovincialis and clams Scrobicularia plana), crabs (Carcinus maenas) as well as fish (Mullus surmuletus) to relate microplastics levels to pollution sources, assess possible impact on marine food chains and on human health. These species were collected from several sites of the Ria Formosa lagoon and along the south coast of Portugal. A quantitative assessment (number, size and color) and typology of microplastics were made in these species. Only one green fragment of polypropylene was detected in the gills of the crabs, while a blue polyethylene fragment was detected in the hepatopancreas of the mullets. Moreover, no microplastics were present in S. plana nor in the crabs whole soft tissues. Among mussels, 86% of microplastics were present from all sites and the number, size and color were site specific. Mussels from the west side of the coast (Sites 1-3) had the highest levels of MPs per mussel and per weight compared to the other sites, probably related to the impact of touristic activity, fishing gears, fresh water and sewage effluents along with the hydrodynamics of the area.

Time to Safeguard the Future Generations from the Omnipresent Microplastics

Microplastics (MPs) as a ubiquitous environmental pollutant have drawn growing attention, and it is concerning that children are more sensitive to MPs than adults. Unfortunately, information about the link between children and MPs is insufficient. Therefore, we review the sources and exposure routes of children to MPs and collect evidence for the potential risks. Children can ingest and/or inhale MPs derived from various foodstuffs and plastic products. Despite the limited knowledge on the toxicity to humans, current studies have proved the accumulation and translocation of MPs in different tissues and organs. Main damages including cytotoxicity, neurotoxicity, and immunotoxicity can be caused by pristine polymers and/or co-contaminants. There is much more to be understood about MPs, especially their health effects, and this study has made it clear that it is time to protect our future generations from the threat of MPs.

Microplastics and other anthropogenic particles in Antarctica: Using penguins as biological samplers

Microplastics (< 5 mm in size) are known to be widespread in the marine environment but are still poorly studied in Polar Regions, particularly in the Antarctic. As penguins have a wide distribution around Antarctica, three congeneric species: Adélie (Pygoscelis adeliae), chinstrap (Pygoscelis antarcticus) and gentoo penguins (Pygoscelis papua) were selected to evaluate the occurrence of microplastics across the Antarctic Peninsula and Scotia Sea. Scat samples (used as a proxy of ingestion), were collected from breeding colonies over seven seasons between 2006 and 2016. Antarctic krill (Euphausia superba), present in scat samples, contributed 85%, 66% and 54% of the diet in terms of frequency of occurrence to the diet of Adélie, gentoo and chinstrap penguins, respectively. Microplastics were found in 15%, 28% and 29% scats of Adélie, chinstrap and gentoo penguin respectively. A total of 92 particles were extracted from the scats (n = 317) and 32% (n = 29) were chemically identified via micro-Fourier Transform Infrared Spectroscopy (μ-FTIR). From all the particles extracted, 35% were identified as microplastics, particularly polyethylene (80%) and polyester (10%). It was not possible to ascertain the identification of the remaining 10% of samples. Other anthropogenic particles were identified in 55% of samples, identified as cellulose fibres. The results show a similar frequency of occurrence of particles across all colonies, suggesting there is no particular point source for microplastic pollution in the Scotia Sea. Additionally, no clear temporal variation in the number of microplastics in penguins was observed. Overall, this study reveals the presence of microplastics across Antarctica, in three penguin species and offers evidence of other anthropogenic particles in high numbers. Further research is needed to better understand the spatio-temporal dynamics, fate and effect of microplastics on these ecosystems, and improve plastic pollution policies in Antarctica.

Micro/nanoplastics effects on organisms: A review focusing on 'dose'

Microplastics have become predominant contaminants, attracting much political and scientific attention. Despite the massively-increasing research on microplastics effects on organisms, the debate of whether environmental concentrations pose hazard and risk continues. This study critically reviews published literatures of microplastics effects on organisms within the context of "dose". It provides substantial evidence of the common occurrence of threshold and hormesis dose responses of numerous aquatic and terrestrial organisms to microplastics. This finding along with accumulated evidence indicating the capacity of organisms for recovery suggests that the linear-no-threshold model is biologically irrelevant and should not serve as a default model for assessing the microplastics risks. The published literature does not provide sufficient evidence supporting the general conclusion that environmental doses of microplastics cause adverse effects on individual organisms. Instead, doses that are smaller than the dose of toxicological threshold and more likely to occur in the environment may even induce positive effects, although the ecological implications of these responses remain unknown. This study also shows that low doses of microplastics can reduce whereas high doses can increase the negative effects of other pollutants. The mechanisms explaining these findings are discussed, providing a novel perspective for evaluating the risks of microplastics in the environment.

Microplastics interaction with terrestrial plants and their impacts on agriculture

Microplastics (MPs) are widespread in natural ecosystems and have attracted considerable attention from scientists all over the world because they are believed to threaten every life form. In addition to their potential physical and chemical effects on organisms, MPs may act as a carrier for many micropollutants, including antibiotics, heavy metals, and others. Over the last 10-15 yr, extensive research has been carried out on MPs in marine environments regarding their sources, fate, and toxicity. However, studies concerning their accumulation in the soil ecosystem, uptake, internalization, and impacts on photosynthetic components of the terrestrial ecosystem and risk assessments have been scanty. Thus, there is a large knowledge gap on the extent to which terrestrial environments, especially agroecosystems, are affected by MPs and their subsequent risks to human health. This review summarizes up-to-date findings about MPs on terrestrial environments and provides guidelines for future studies regarding the phytotoxic effects of MPs on plants; the mechanism of uptake and translocation in plant tissues; detection tools for MPs in plants; impacts on plant growth, plant development, and agricultural productivity; and, most important, the future prospects of MPs interaction and accumulation in plants.

Microplastics reduce net population growth and fecal pellet sinking rates for the marine copepod, Acartia tonsa

Microplastics (<5 mm) are ubiquitous in the global environment and are increasingly recognized as a biological hazard, particularly in the oceans. Zooplankton, at the base of the marine food web, have been known to consume microplastics. However, we know little about the impacts of microplastics across life history stages and on carbon settling. Here, we investigated the effects of ingestion of neutrally buoyant polystyrene beads (6.68 μm) by the copepod Acartia tonsa on (1) growth and survival across life history stages, (2) fecundity and egg quality, (3) and fecal characteristics. We found that microplastic exposure reduced body length and survival for nauplii and resulted in smaller eggs when copepods were exposed during oogenesis. Combining these life history impacts, our models estimate a 15% decrease in population growth leading to a projected 30-fold decrease in abundance over 1 year or 20 generations with microplastic exposure. In addition, microplastic-contaminated fecal pellets were 2.29-fold smaller and sinking rates were calculated to be 1.76-fold slower, resulting in an estimated 4.03-fold reduction in fecal volume settling to the benthos per day. Taken together, declines in population sizes and fecal sinking rates suggest that microplastic consumption by zooplankton could have cascading ecosystem impacts via reduced trophic energy transfer and slower carbon settling.

How do humans recognize and face challenges of microplastic pollution in marine environments? A bibliometric analysis

Microplastics (MPs) are abundant in marine environments, drawing global attention from scientists and rendering it significant to review the research progress and predict future trends of this field. To achieve that, we collected 1898 publications on marine MPs from Web of Science and performed a bibliometric analysis by CiteSpace and VOSviewer. Additionally, we utilized an unrestricted retrieval of literature from ScienceDirect to supplement our major findings. Trends in publication numbers show the growth in study from the initial stage ( 2012 and before), when microplastic (MP) occurrence, abundance, and distribution were primarily investigated. Throughout the ascent stage (between 2013-2016), when diverse sampling and analytical methods were applied to capture and identify MPs from the ocean, baseline data have been gleaned on physiochemical properties of MPs. The research focus then shifted to the bioaccumulation and ecotoxicological effects of MPs on marine biota, further highlighting their potential deleterious impacts on human health via dietary exposure, and this period was defined as the exploration stage (2017 and onwards). Nevertheless, key challenges including the lack of standard procedures for MP sampling, technical limitations in MP detecting and identification, and controversy about the underlying effects on the marine ecosystems and humans have also been arisen in the last decade. The present study elucidates how we gradually recognize MP pollution in marine environments and what challenges we face, suggesting future avenues for MP research.