Evidence is increasing that micro- and nanoplastic particles can have adverse effects on aquatic organisms. Exposure studies have so far mainly been qualitative since quantitative measurements of ...particle ingestion are analytically challenging. The aim of this study was therefore to use a quantitative approach for determining ingestion and egestion of micro- and nanoplastics in Daphnia magna and to analyze the influence of particle size, exposure duration and the presence of food. One week old animals were exposed to 2 μm and 100 nm fluorescent polystyrene beads (1 mg/l) for 24 h, followed by a 24 h egestion period in clean medium. During both phases body burdens of particles were determined by measuring the fluorescence intensity in dissolved tissues. Ingestion and egestion were investigated in the absence and presence of food (6.7·105 cells of Raphidocelis subcapitata per ml). Furthermore, feeding rates of daphnids in response to particle exposure were measured as well as effects on reproduction during a 21 days exposure (at 1 mg/l, 0.5 mg/l and 0.1 mg/l) to investigate potential impairments of physiology. Both particle sizes were readily ingested, but the ingested mass of particles was five times higher for the 2 μm particles than for the 100 nm particles. Complete egestion did not occur within 24 h but generally higher amounts of the 2 μm particles were egested. Animal body burdens of particles were strongly reduced in the presence of food. Daphnid feeding rates decreased by 21% in the presence of 100 nm particles, but no effect on reproduction was found despite high body burdens of particles at the end of 21 days exposure. The lower egestion and decreased feeding rates, caused by the 100 nm particles, could indicate that particles in the nanometer size range are potentially more hazardous to D. magna compared to larger particle sizes.
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•Animal body burdens were quantified using fluorescent plastic particles.•Microplastics were ingested in higher quantity than nanoplastics.•Highest degree of particle egestion was seen for microplastics.•Animal body burdens of particles strongly decreased in the presence of food.•Exposure to 100 nm polystyrene particles decreased Daphnia feeding rates.
The body burdens of plastic particles in Daphnia magna depended on the particle size, the exposure duration and the presence of food in the medium.
Microplastic research in recent years has shown that small plastic particles are found almost everywhere we look. Besides aquatic and terrestrial environments, this also includes aquatic species ...intended for human consumption and several studies have reported their prevalence in other food products and beverages. The scientific as well as public debate has therefore increasingly focused on human health implications of microplastic exposure. However, there is a big discrepancy between the magnitude of this debate and actual scientific findings, which have merely shown the presence of microplastics in certain products. While plastics can undoubtedly be hazardous to human health due to toxicity of associated chemicals or as a consequence of particle toxicity, the extent to which microplastics in individual food products and beverages contribute to this is debatable. Considering the enormous use of plastic materials in our everyday lives, microplastics from food products and beverages likely only constitute a minor exposure pathway for plastic particles and associated chemicals to humans. But as this is rarely put into perspective, the recent debate has created a skewed picture of human plastic exposure. We risk pulling the focus away from the root of the problem: the way in which we consume, use and dispose of plastics leading to their widespread presence in our everyday life and in the environment. Therefore we urge for a more careful and balanced discussion which includes these aspects.
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•There is data supporting possible chemical and particle toxicity effects of plastic.•The current debate on human health effects of plastics is unbalanced.•There is a disproportionate focus on microplastics in individual food products.•Exposure to additives and microplastics is mainly related to general plastic use.•We urge for a more balanced discussion on human exposure to plastics.
The accumulation of plastic litter in natural environments is a global issue. Concerns over potential negative impacts on the economy, wildlife, and human health provide strong incentives for ...improving the sustainable use of plastics. Despite the many voices raised on the issue, we lack a consensus on how to define and categorize plastic debris. This is evident for microplastics, where inconsistent size classes are used and where the materials to be included are under debate. While this is inherent in an emerging research field, an ambiguous terminology results in confusion and miscommunication that may compromise progress in research and mitigation measures. Therefore, we need to be explicit on what exactly we consider plastic debris. Thus, we critically discuss the advantages and disadvantages of a unified terminology, propose a definition and categorization framework, and highlight areas of uncertainty. Going beyond size classes, our framework includes physicochemical properties (polymer composition, solid state, solubility) as defining criteria and size, shape, color, and origin as classifiers for categorization. Acknowledging the rapid evolution of our knowledge on plastic pollution, our framework will promote consensus building within the scientific and regulatory community based on a solid scientific foundation.
It is well known that mussels are exposed to microplastics but ingestion and potential effects on mussel larvae are not well understood. We quantified ingestion and egestion of 100 nm and 2 μm ...polystyrene beads in blue mussel larvae after 4 h exposure and 16 h depuration using different plastic-to-microalgae ratios. Effects on growth and development of mussel larvae were investigated at 0.42, 28.2 and 282 μgL−1 within 15 days of exposure. We found that, on a mass basis, larvae ingested a higher amount of 2 μm than 100 nm beads, while egestion was independent of particle size and the plastics-to-algae ratio. Although particle egestion occurred readily, microplastics remained inside the larvae. Larval growth was not affected but abnormally developed larvae increased after exposure to polystyrene beads. Malformations were more pronounced for 100 nm beads, at higher concentration and after longer exposure time.
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•Blue mussel larvae ingested more 2 μm than 100 nm polystyrene beads on a mass basis.•Egestion was independent of particle size and the ratio of plastic to food algae.•None of the particle sizes were completely egested after up to 48 h in clean water.•Abnormal larval development increased during 15 d exposure to both particle sizes.•More malformations were observed for 100 nm beads and with longer exposure time.
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•P. subcapitata cultures were exposed to plastic nanoparticles in adsorption assays.•UV/Vis and AFM showed ionic strength and surface chemistry influence adsorption of anionic and ...neutral nanoplastics.•Growth inhibition of algae is antagonistically influenced by carboxylate-modified polystyrene and calcium.•Physico-chemical characterization and proper dose metrics can be used to predict ecotoxicity.
To investigate processes possibly underlying accumulation and ecological effects of plastic nano-particles we have characterized their interaction with the cell wall of green algae. More specifically, we have investigated the influence of particle surface functionality and water hardness (Ca2+ concentration) on particle adsorption to algae cell walls. Polystyrene nanoparticles with different functional groups (non-functionalized, −COOH and −NH2) as well as coated (starch and PEG) gold nanoparticles were applied in these studies. Depletion measurements and atomic force microscopy (AFM) showed that adsorption of neutral and positively charged plastic nanoparticles onto the cell wall of P. subcapitata was stronger than that of negatively charged plastic particles. Results indicated that binding affinity is a function of both inter-particle and particle-cell wall interactions which are in turn influenced by the medium hardness and particle concentration. Physicochemical modelling using DLVO theory was used to interpret the experimental data, using also values for interfacial surface free energies. Our study shows that material properties and medium conditions play a crucial role in the rate and state of nanoparticle bio-adsorption for green algae. The results show that the toxicity of nanoparticles can be better described and assessed by using appropriate dose metrics including material properties, complexation/agglomeration behavior and cellular attachment and adsorption. The applied methodology provides an efficient and feasible approach for evaluating potential accumulation and hazardous effects of nanoparticles to algae caused by particle interactions with the algae cell walls.
It is becoming increasingly important to develop assessment criteria for the quality of nanoplastics studies. This study is an attempt to establish such criteria based on those developed for ...engineered nanomaterials, the GUIDEnano and DaNa criteria being two representatives. These criteria were applied to studies on polystyrene nanoparticles (PS NPs), which currently represent the majority of studies on nanoplastics. We compiled a list of existing nanomaterial-related criteria that are not fully relevant to PS NPs and propose additional nanoplastic-specific criteria targeting polymer chemical composition, source, production and field collection, impurities/chemical additives, density, hydrophobicity, colour, and chemical leaching. For each criterion, scientific justification is provided. We conclude that the existing study quality assessments originally developed for nano(eco)toxicity studies can, through refinements, be applied to those dealing with nanoplastics studies, with a further outlook on microplastics. The final quality criteria catalogue presented here is intended as a starting point for further elaborations considering different purposes of an assessment.
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•Nanoplastic quality criteria for ecotoxicity studies are presented.•As a basis, engineered nanomaterial quality criteria were reviewed.•Based on scientific evidence they were refined by additional, plastic specific quality criteria.•Specific considerations are needed for secondary nanoplastics.•The quality criteria catalogue presented can be extended to microplastics.
In aquatic toxicity testing of engineered nanoparticles (ENPs) the process of agglomeration is very important as it may alter bioavailability and toxicity. In the present study, we aimed to identify ...test conditions that are favorable for maintaining stable ENP suspensions. We evaluated the influence of key environmental parameters: pH (2–12) and ionic strength using M7, Soft EPA (S EPA) medium, and Very Soft EPA (VS EPA) medium; and observed the influence of these parameters on zeta potential, zeta average, and acute immobilization of Daphnia magna for three different ENPs. Despite being sterically stabilized, test suspensions of silver (Ag) ENPs formed large agglomerates in both VS EPA and M7 media; and toxicity was found to be higher in VS EPA medium due to increased dissolution. Low-agglomerate suspensions for zinc oxide (ZnO) could be obtained at pH 7 in VS EPA medium, but the increase in dissolution caused higher toxicity than in M7 medium. Titanium dioxide (TiO2) ENPs had a point of zero charge in the range of pH 7–8. At pH 7 in VS EPA, agglomerates with smaller hydrodynamic diameters (~200nm) were present compared to the high ionic strength M7 medium where hydrodynamic diameters reached micrometer range. The stable suspensions of TiO2 ENPs caused immobilization of D. magna, 48-h EC50 value of 13.7mgL−1 (95% CI, 2.4mg–79.1mgL−1); whereas no toxicity was seen in the unstable, highly agglomerated M7 medium suspensions, 48-h EC50 >100mgL−1. The current study provides a preliminary approach for methodology in testing and assessing stability and toxicity of ENPs in aquatic toxicity tests of regulatory relevance.
•Media composition and pH can affect the stability of test suspensions.•Measuring of point of zero charge is necessary in aquatic tests.•VS EPA medium at pH 7 were the optimal test parameters for lowest hydrodynamic diameters.•Agglomerates of small hydrodynamic diameter (TiO2 ENPs) were more toxic.
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