Abundance and risk assessment of microplastics in water, sediment, and aquatic insects of the Nile River

Microplastics (MPs) are a serious threat in freshwater environments. The ecological risk and abundance level of MPs in abiotic and biotic compartments of the Nile River haven't been systematically reported. Thus, these issues were highlighted in the present study during different seasons of the sampling year. The results showed that MP concentrations in the river ranged from 2.24 ± 0.6 to 3.76 ± 1.1 particles/L, 298 ± 63 to 520 ± 80 particles/kg dry weight, and 0.081 ± 0.051 to 4.95 ± 2.6 particles/individual in surface water, sediment, and different species of aquatic insects, respectively. All the extracted MPs are colored blue, red, and black. Fiber-shaped polyesters (<500-1500 μm) were the most common MPs in all the river compartments. MPs' dominance was observed during the summer in comparison with that in the other seasons. Environmental risk indicators indicate the high ecological risk of MPs, which are widely distributed in the Nile River. In conclusion, MP consumption by aquatic insects may not only be related to levels of environmental contamination, since other variables, such as taxon size, weight, and particular feeding behavior, may also be significant. Additionally, the presence of MPs in insects (at lower trophic levels) creates the potential for predation-based inter-trophic level transmission. Thus, higher trophic-level investigations of various feeding groups should be carried out to identify any possible harm that MPs cause to various aquatic organisms.

Are bioplastics safe? Hazardous effects of polylactic acid (PLA) nanoplastics in Drosophila

The expanded uses of bioplastics require understanding the potential health risks associated with their exposure. To address this issue, Drosophila melanogaster as a versatile terrestrial in vivo model was employed, and polylactic acid nanoplastics (PLA-NPLs), as a proxy for bioplastics, were tested as a material model. Effects were determined in larvae exposed for 4 days to different concentrations (25, 100, and 400 μg/mL) of 463.9 ± 129.4 nm PLA-NPLs. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) approaches permitted the detection of PLA-NPLs in the midgut lumen of Drosophila larvae, interacting with symbiotic bacteria. Enzymatic vacuoles were observed as carriers, collecting PLA-NPLs and enabling the crossing of the peritrophic membrane, finally internalizing into enterocytes. Although no toxic effects were observed in egg-to-adult survival, cell uptake of PLA-NPLs causes cytological disturbances and the formation of large vacuoles. The translocation across the intestinal barrier was demonstrated by their presence in the hemolymph. PLA-NPL exposure triggered intestinal damage, oxidative stress, DNA damage, and inflammation responses, as evaluated via a wide set of marker genes. Collectively, these structural and molecular interferences caused by PLA-NPLs generated high levels of oxidative stress and DNA damage in the hemocytes of Drosophila larvae. The observed effects point out the need for further studies aiming to deepen the health risks of bioplastics before adopting their uses as a safe plastic alternative.

Interactions between microplastics and Culex sp. larvae in wastewater

Microplastics (MPs) are a growing issue because they endanger both aquatic organisms and humans. Studies have indicated that wastewater treatment plants (WWTPs) are one of the major contributors to MPs in the environment. However, studies on the abundance of MP contamination in WWTPs and its transmission into aquatic organisms are still scarce, especially in Egypt. The goal of this study was to examine the temporal fluctuations in the distribution of MPs in surface water and the dominant macroinvertebrate fauna (Culex sp. larvae) in a fixed wastewater basin in Sohag Governorate, Egypt. The average of MPs in the surface water was 3.01 ± 0.9 particles/L. The results indicated to seasonal variation of MP abundance in the wastewater basin that was significantly higher in winter than in the other seasons. The risk index for polymers (H), pollution load index (PLI), and potential ecological risk index (RI) were used to assess the degree of MP contamination. The basin has moderate H values (<1000) because of the presence of polymers with moderate hazard scores such as polyester (PES), polyethylene (PE), and polypropylene (PP). According to the PLI values, surface water is extremely contaminated with MPs (PLI: 88 to 120). The RI values of surface water showed higher ecological risk (level V). MPs in Culex sp. larvae were seasonally changed with an 85% detection rate, and an abundance average of 0.24 ± 0.65 particles/ind, MP concentration in Culex sp. larvae was influenced by the MP characters (shape, color, and polymer). The larvae of Culex sp. showed a greater preference for black and red fibrous polyester (PES) with sizes (<1000 μm) of MPs. These findings suggest that Culex sp. larvae prefer ingesting MPs that resemble their food. It is possible to overestimate Culex sp.'s preference for lower sizes because of their catabolism of MPs. To better understand the preferences of Culex sp. larvae for MPs, further controlled trials should be conducted. PRACTITIONER POINTS: Wastewater is highly contaminated with microplastics (MPs) in the different seasons. First report of detection of the seasonal abundance of MP in Culex sp. larvae. Culex sp. larvae showed a stronger feeding preference for MPs with specific characteristics. Smaller size and blue polyester fibers were the dominant characteristics of MPs in wastewater.

Titanium-doped PET nanoplastics, from opaque milk bottle degradation, as a model of environmental true-to-life nanoplastics. Hazardous effects on Drosophila

Micro and nanoplastics (MNPLs) are emergent environmental pollutants, resulting from the degradation of plastic waste, requiring urgent information on their potential risks to human health. To determine such risks, reliable true-to-life materials are essential. In this work, we have used titanium-doped PET NPLs [PET(Ti)NPLs], obtained by grinding opaque milk polyethylene terephthalate (PET) bottles, as a true-to-life MNPLs model. These opaque PET bottles, with an average size of 112 nm, contain about 3% Ti in the form of titanium dioxide rod nanoparticles. TEM investigation confirmed the mixed Ti/PET nature of the obtained true-to-life NPLs, and the rod shape of the embedded TiO2NPs. In the in vivo Drosophila model neither PET(Ti)NPLs nor TiO2NPs reduced the survival rates, although their internalization was confirmed in different compartments of the larval body by using confocal and transmission electron microscopies. The presence of Ti in the PET(Ti)NPLs permitted to quantify its presence both in larvae (2.1 ± 2.2 μg/g of Ti) and in the resulting adults (3.4 ± 3.2 μg/g of Ti) after treatment with 500 μg/g food of PET(Ti)NPL, suggesting its potential use to track their fate in more complex organisms such as mammals. PET(Ti)NPLs, as well as TiO2NPs, altered the expression of genes driving different response pathways, inducing significant oxidative stress levels (up to 10 folds), and genotoxicity. This last result on the genotoxic effects is remarkable in the frame of the hot topic discussion on the risk that titanium compounds, used as food additives, may pose to humans.

Seasonal variations of microplastic in sediment, Chironomus sp. larvae, and chironomid tubes in two wastewater sites in Sohag Governorate, Egypt

Microplastic (MP) contamination is an acknowledged global problem that poses a severe risk to aquatic ecosystem biota. Nevertheless, little is known about their prevalence in animal construction. The main objective of our study was to reduce the gap information of seasonal abundance, distribution, composition, and risk assessment of MP contamination. The concentrations of MPs in sediment, Chironomus sp. larvae, and their tubes were found to be higher in site 2 (S2) than in site 1 (S1) during the four seasons of the year. However, MP concentrations ranged from 312 ± 64.7 to 470 ± 70 items/kg dry weight, 0.79 ± 0.16 to 1.1 ± 0.3 particles/individual, and 0.5 ± 0.04 to 0.9 ± 0.04 particles/tube in sediment, Chironomus, and chironomid tubes, respectively. Blue and red polyester fibers are the most dominant MPs which are distributed in sediment, Chironomus, and chironomid tubes. The length of the dominant fiber accumulates in Chironomus, and their tubes are highly varied compared to that of the substrate. Additionally, we found that the mean number of MPs/individual larvae in the fourth instar was significantly higher than that in the second instar. Risk indicators for the environment, polymer risk assessment, and pollution load were estimated, where they were higher in S2 than in S1 correlated to MPs abundance and polymer type. The seasonal fluctuation in MP concentration, characterization, and risk in the two sites could depend on the amount of sewage effluent discharged into the wastewater treatment plants (WWTPs), which was reflected by Chironomus sp. larvae. Therefore, further research should be done to adopt the applicability of Chironomus as MP bioindicators in various freshwater environments throughout the world.

Titanium-doped PET nanoplastics of environmental origin as a true-to-life model of nanoplastic

The increased presence of secondary micro/nanoplastics (MNPLs) in the environment requires urgent studies on their potentially hazardous effects on exposed organisms, including humans. In this context, it is essential to obtain representative MNPL samples for such purposes. In our study, we have obtained true-to-life NPLs resulting from the degradation, via sanding, of opaque PET bottles. Since these bottles contain titanium (TiO₂NPs), the resulting MNPLs also contain embedded metal. The obtained PET(Ti)NPLs were extensively characterized from a physicochemical point of view, confirming their nanosized range and their hybrid composition. This is the first time these types of NPLs are obtained and characterized. The preliminary hazard studies show their easy internalization in different cell lines, without apparent general toxicity. The demonstration by confocal microscopy that the obtained NPLs contain Ti samples offers this material multiple advantages. Thus, they can be used in in vivo approaches to determine the fate of NPLs after exposure, escaping from the existing difficulties to follow up MNPLs in biological samples.

The hazardous impact of true-to-life PET nanoplastics in Drosophila

Plastic pollution is a continuously growing problem that can threaten wildlife and human beings. Environmental plastic waste is degraded into small particles termed micro/ nanoplastics (MNPLs) that, due to their small size, can be easily internalized into the exposed organisms, increasing the risks associated with their exposure. To appropriately determine the associated health risk, it is essential to obtain/test representative MNPLs' environmental samples. To such end, we have obtained NPLs resulting from sanding commercial water polyethylene terephthalate (PET) bottles. These true-to-life PETNPLs were extensively characterized, and their potential hazard impacts were explored using Drosophila melanogaster. To highlight the internalization through the digestive tract and the whole body, transmission electron microscopy (TEM) and confocal microscopy were used. In spite of the observed efficient uptake of PETNPLs into symbiotic bacteria, enterocytes, and hemocytes, the exposure failed to reduce flies' survival rates. Nevertheless, PETNPLs exposure disturbed the expression of stress, antioxidant, and DNA repair genes, as well as in those genes involved in the response to physical intestinal damage. Importantly, both oxidative stress and DNA damage induction were markedly increased as a consequence of the exposure to PETNPLs.

Chironomus sp. as a Bioindicator for Assessing Microplastic Contamination and the Heavy Metals Associated with It in the Sediment of Wastewater in Sohag Governorate, Egypt

The consequences of plastic waste pollution have imposed wide global concerns. One of these consequences is the production of micro- and nanosized particles (MNPLs) from aged plastics. The problem of MNPLs is magnified by their potential to transport various contaminants due to their large surface area and other variable physiochemical properties. From this point on, it is important to know the real concentration of MNPLs in our environment and their potential to internalize wild organisms as well as transfer contaminants that are completely highlighted. As a result, our study is the first to detect MP pollution in the upper Egypt wastewater environment. It could be utilized as a baseline to estimate MP wastes and develop management techniques, particularly in Sohag Governorate. The concentration and characterization of MPs in sludge, water, Chironomus sp. larvae, and their tubes were studied in this work. Chironomus sp. is a reliable bioindicator prevalent in such contaminated environments, and it was used to demonstrate how MPs invade biological barriers. Our results found that red and blue polyester fibers are much more prevalent than other polymers, colors, and shapes of MPs. While each dry kilogram of wastewater sludge contains 310 ± 84 particles, this amount is reduced to 1.55 ± 0.7 per liter in the water column. Biologically, the present study succeeded in detecting the MPs inside the wild organism, with concentrations reaching 71 ± 21 and 4.41 ± 1.1 particles per gram wet weight in Chironomus sp. larvae and their tubes (chironomid tubes), respectively. The potential hazard of MPs stems from their propensity to transfer pollutants. At this point, our findings revealed a corresponding and significant concentration of various heavy metals (Cu, Pb, Cd, and Ni) detected in MPs or Chironomus sp. versus sludge. In conclusion, our findings not only proved the presence of MPs in wastewater but also demonstrated their ability to internalize cross-wild organisms, allowing toxins to accumulate inside their bodies, raising concerns about the possible health impacts of plastic pollution.

Antagonistic in vivo interaction of polystyrene nanoplastics and silver compounds. A study using Drosophila

Since heavy metals and micro-/nanoplastics (MNPLs) can share common environmental niches, their potential interactions could modulate their hazard impacts. The current study was planned to evaluate the potential interactions between silver compounds (silver nanoparticles or silver nitrate) and two different sizes of polystyrene nanoplastics (PSNPLs) (PS-50 and PS-500 nm), administered via ingestion to Drosophila larvae. While egg-to-adult survival was not affected by the exposure to silver compounds, PSNPLs, or their coexposures, the combined treatments succeeded to restore the delay of fly emergence induced by silver compounds. Transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS) showed the ability of PSNPLs to transport silver compounds (regardless of their form) across the intestinal barrier, delivering them into the hemolymph of Drosophila larvae in a concentration exceeding that mediated by the exposure to silver compounds alone. The molecular response (gene expression) of Drosophila larvae greatly fluctuated, accordingly if exposures were administered alone or in combination. Although PSNPLs produced some oxidative stress in the hemocytes of Drosophila, especially at the highest dose (1 mM), higher levels were observed after silver exposure, regardless of its form. Interestingly, the oxidative stress of silver, especially that produced by nano‑silver, drastically decreased when coexposed with PSNPLs. Similar effects were observed regarding the DNA damage induced in Drosophila hemocytes, where cotreatment decreased the genotoxicity induced by silver compounds. This antagonistic interaction could be attributed to the ability of tiny plastic specks to confine silver, avoiding its bioavailability, and diminishing their potential impacts.

A new source of representative secondary PET nanoplastics. Obtention, characterization, and hazard evaluation

Micro and nanoplastics (MNPLs) are emergent environmental pollutants requiring urgent information on their potential risks to human health. One of the problems associated with the evaluation of their undesirable effects is the lack of representative samples, matching those resulting from the environmental degradation of plastic wastes. To such end, we propose an easy method to obtain polyethylene terephthalate nanoplastics from water plastic bottles (PET-NPLs) but, in principle, applicable to any other plastic goods sources. An extensive characterization indicates that the proposed process produces uniform samples of PET-NPLs of around 100 nm, as determined by using AF4 and multi-angle and dynamic light scattering methodologies. An important point to be highlighted is that to avoid the metal contamination resulting from methods using metal blades/burrs for milling, trituration, or sanding, we propose to use diamond burrs to produce metal-free samples. To visualize the toxicological profile of the produced PET-NPLs we have evaluated their ability to be internalized by cells, their cytotoxicity, their ability to induce oxidative stress, and induce DNA damage. In this preliminary approach, we have detected their cellular uptake, but without the induction of significant biological effects. Thus, no relevant increases in toxicity, reactive oxygen species (ROS) induction, or DNA damage -as detected with the comet assay- have been observed. The use of representative samples, as produced in this study, will generate relevant data in the discussion about the potential health risks associated with MNPLs exposures.

Novel insights into biodegradation, interaction, internalization and impacts of high-aspect-ratio TiO2 nanomaterials: A systematic in vivo study using Drosophila melanogaster

The elongated nature of the high-aspect-ratio nanomaterials (NMs) can help us to obtain valuable information on its biodegradation, physical interaction with target-cells, and internalization. Three different length nano-titanium have been studied using Drosophila, TEM, and different biological markers. Nano-titanium, regardless of its shape, was eroded and degraded just entering the gut lumen of the larvae. Results showed that the distinguished shape of nanowires helps to understand the interactions of NMs with the intestinal barrier. The peritrophic membrane, as the first defense line of the intestinal barrier, succeeded in the reservation of NMs, though the perpendicular particles of nanowires stabbing it, making pores, and permitting their translocation into intestinal cells. On the other side, the exposure to TiO₂NPs did not decrease egg-to-adult viability, but all its different shapes, especially nanowires, mediated a wide molecular response including changes of expression in genes involved in stress, antioxidant, repair, and physical interaction responses. All these changes concerning their ability to elevate ROS levels ultimately led to potential genotoxicity. So, the high aspect ratio NMs are efficient in understanding the outstanding issues of NMs exposure, but at the same time could induce genotoxic impact rather than the low aspect ones.

Toxic and Genotoxic Effects of Silver Nanoparticles in Drosophila

The in vivo model Drosophila melanogaster was used here to determine the detrimental effects induced by silver nanoparticles (AgNPs) exposure. The main aim was to explore its interaction with the intestinal barrier and the genotoxic effects induced in hemocytes. The observed effects were compared with those obtained by silver nitrate, as an agent acting via the release of silver ions. Larvae were fed in food media containing both forms of silver. Results indicated that silver nitrate was more toxic than AgNPs when the viability "egg-to-adult" was determined. Depigmentation was observed in adults including those exposed to nontoxic concentrations, as indicative of exposure action. Interestingly, AgNPs were able to cross the intestinal barrier affecting hemocytes that show significant increases in the levels of intracellular reactive oxygen species. Additionally, significant levels of genotoxic damage, as determined by the comet assay, were also induced. When the expression of different stress-response genes was determined, for both AgNPs and silver nitrate, significant upregulation of Sod2 and p53 genes was observed. Our results confirm for the first time that in an in vivo model as Drosophila, AgNPs are able to cross the intestinal barriers and produce primary DNA damage (comet assay) via oxidative stress induction. In general, the effects induced by silver nitrate were more pronounced than those induced by AgNPs what would emphasize the role of silver ions in the observed effects. Environ. Mol. Mutagen. 60:277-285, 2019. © 2018 Wiley Periodicals, Inc.

Copper oxide nanoparticles and copper sulphate act as antigenotoxic agents in drosophila melanogaster

The biological reactivity of metal and metal oxide nanomaterials is attributed to their redox properties, which would explain their pro- or anti-cancer properties depending on exposure circumstances. In this sense, copper oxide nanoparticles (CuONP) have been proposed as a potential anti-tumoral agent. The aim of this study was to assess if CuONP can exert antigenotoxic effects using Drosophila melanogaster as an in vivo model. Genotoxicity was induced by two well-known genotoxic compounds, namely potassium dichromate (PD) and ethyl methanesulfonate (EMS). The wing-spot assay and the comet assay were used as biomarkers of genotoxic effects. In addition, changes in the expression of Ogg1 and Sod genes were determined. The effects of CuONP cotreatment were compared with those induced by copper sulfate (CS), an agent releasing copper ions. Using the wing-spot assay, CuONP and CS were not able to reduce the genotoxic effects of EMS exposure, but had the ability to decrease the effects induced by PD, reducing the frequency of mutant twin-spots that arise from mitotic recombination. In addition, CuONP and CS were able to reduce the DNA damage induced by PD as determined by the comet assay. In general, similar qualitative antigenotoxic effects were obtained with both copper compounds. The antigenotoxic effects of environmentally relevant and non-toxic doses of CuONP and CS may be explained by their ability to partially restore the expression levels of the repair gene Ogg1 and the antioxidant gene Cu,ZnSod, both of which are inhibited by PD treatment. Environ. Mol. Mutagen. 58:46-55, 2017. © 2016 Wiley Periodicals, Inc.

Drosophila melanogaster as a suitable in vivo model to determine potential side effects of nanomaterials: A review

Despite being a relatively new field, nanoscience has been in the forefront among many scientific areas. Nanoparticle materials (NM) present interesting physicochemical characteristics not necessarily found in their bulky forms, and alterations in their size or coating markedly modify their physical, chemical, and biological properties. Due to these novel properties there is a general trend to exploit these NM in several fields of science, particularly in medicine and industry. The increased presence of NM in the environment warrants evaluation of potential harmful effects in order to protect both environment and human exposed populations. Although in vitro approaches are commonly used to determine potential adverse effects of NM, in vivo studies generate data expected to be more relevant for risk assessment. As an in vivo model Drosophila melanogaster was previously found to possess reliable utility in determining the biological effects of NM, and thus its usage increased markedly over the last few years. The aims of this review are to present a comprehensive overview of all apparent studies carried out with NM and Drosophila, to attain a clear and comprehensive picture of the potential risk of NM exposure to health, and to demonstrate the advantages of using Drosophila in nanotoxicological investigations.

A comprehensive study of the harmful effects of ZnO nanoparticles using Drosophila melanogaster as an in vivo model

This study planned to determine the range of biological effects associated with ZnO-NP exposure using Drosophila melanogaster as an in vivo model. In addition, ZnCl2 was used to determine the potential role of Zn ions alone. Toxicity, internalization through the intestinal barrier, gene expression changes, ROS production, and genotoxicity were the end-points evaluated. No toxicity or oxidative stress induction was observed in D. melanogaster larvae, whether using ZnO-NPs or ZnCl2. Internalization of ZnO-NPs through the intestinal barrier was observed. No significant changes in the frequency of mutant clones (wing-spot test) or percentage of DNA in tail (comet assay) were observed although significant changes in Hsp70 and p53 gene expression were detected. Our study shows that ZnO-NPs do not induce toxicity or genotoxicity in D. melanogaster, although uptake occurs and altered gene expression is observed.

Assessing potential harmful effects of CdSe quantum dots by using Drosophila melanogaster as in vivo model

Since CdSe QDs are increasingly used in medical and pharmaceutical sciences careful and systematic studies to determine their biosafety are needed. Since in vivo studies produce relevant information complementing in vitro data, we promote the use of Drosophila melanogaster as a suitable in vivo model to detect toxic and genotoxic effects associated with CdSe QD exposure. Taking into account the potential release of cadmium ions, QD effects were compared with those obtained with CdCl2. Results showed that CdSe QDs penetrate the intestinal barrier of the larvae reaching the hemolymph, interacting with hemocytes, and inducing dose/time dependent significant genotoxic effects, as determined by the comet assay. Elevated ROS production, QD biodegradation, and significant disturbance in the conserved Hsps, antioxidant and p53 genes were also observed. Overall, QD effects were milder than those induced by CdCl2 suggesting the role of Cd released ions in the observed harmful effects of Cd based QDs. To reduce the observed side-effects of Cd based QDs biocompatible coats would be required to avoid cadmium's undesirable effects.

Antioxidant and antigenotoxic properties of CeO2 NPs and cerium sulphate: Studies with Drosophila melanogaster as a promising in vivo model

Although in vitro approaches are the most used for testing the potential harmful effects of nanomaterials, in vivo studies produce relevant information complementing in vitro data. In this context, we promote the use of Drosophila melanogaster as a suitable in vivo model to characterise the potential risks associated to nanomaterials exposure. The main aim of this study was to evaluate different biological effects associated to cerium oxide nanoparticles (Ce-NPs) and cerium (IV) sulphate exposure. The end-points evaluated were egg-to-adult viability, particles uptake through the intestinal barrier, gene expression and intracellular reactive oxygen species (ROS) production by haemocytes, genotoxicity and antigenotoxicity. Transmission electron microscopy images showed internalisation of Ce-NPs by the intestinal barrier and haemocytes, and significant expression of Hsp genes was detected. In spite of these findings, neither toxicity nor genotoxicity related to both forms of cerium were observed. Interestingly, Ce-NPs significantly reduced the genotoxic effect of potassium dichromate and the intracellular ROS production. No morphological malformations were detected after larvae treatment. This study highlights the importance of D. melanogaster as animal model in the study of the different biological effects caused by nanoparticulated materials, at the time that shows its usefulness to study the role of the intestinal barrier in the transposition of nanomaterials entering via ingestion.