Large-scale monitoring and risk assessment of microplastics in the Amazon River

Microplastics (MPs) are one of the most widespread contaminants worldwide, yet their risks for freshwater ecosystems have seldom been investigated. In this study, we performed a large monitoring campaign to assess the presence and risks of MPs in Amazonian freshwater ecosystems. We investigated MP pollution in 40 samples collected along 1500 km in the Brazilian Amazon, including the Amazon River, three major tributaries, and several streams next to the most important urban areas. MPs in the 55–5000 µm size range were characterized (size, shape, color) by microscopy and identified (polymer composition) by infrared spectroscopy. Ecotoxicological risks were assessed using chronic Species Sensitivity Distributions for effects triggered by food dilution and tissue translocation using data alignment methods that correct for polydispersity of environmental MPs and bioaccessibility. This study shows that MPs are ubiquitous contaminants in Amazonian freshwater ecosystems, with measured concentrations (55–5000 µm) ranging between 5 and 152 MPs/m3 in the Amazon River and its main tributaries, and between 23 and 74,550 MPs/m3 in urban streams. The calculated Hazardous Concentration for the 5% of species (HC5) derived from the SSDs for the entire MP range (1–5000 µm) were 1.6 × 107 MPs/m3 (95% CI: 1.2 × 106 – 4.0 × 108) for food dilution, and 1.8 × 107 MPs/m3 (95% CI: 1.5 × 106 – 4.3 × 108) for translocation. Rescaled exposure concentrations (1–5000 µm) in the Amazon River and tributaries ranged between 6.0 × 103 and 1.8 × 105 MPs/m3, and were significantly lower than the calculated HC5 values. Rescaled concentrations in urban streams ranged between 1.7 × 105 and 5.7 × 108 MPs/m3, and exceeded both calculated HC5 values in 20% of the locations. This study shows that ecological impacts by MP contamination are not likely to happen in the Amazon River and its major tributaries. However, risks for freshwater organisms may be expected in near densely populated areas, such as the cities of Manaus or Belem, which have limited wastewater treatment facilities.Large-scale monitoring and risk assessment of microplastics in the Amazon RiverpublishedVersio

Microplastic in angling baits as a cryptic source of contamination in European freshwaters.

High environmental microplastic pollution, and its largely unquantified impacts on organisms, are driving studies to assess their potential entry pathways into freshwaters. Recreational angling, where many anglers release manufactured baits into freshwater ecosystems, is a widespread activity with important socio-economic implications in Europe. It also represents a potential microplastic pathway into freshwaters that has yet to be quantified. Correspondingly, we analysed three different categories of industrially-produced baits ('groundbait', 'boilies' and 'pellets') for their microplastic contamination (particles 700 µm to 5 mm). From 160 samples, 28 microplastics were identified in groundbait and boilies, with a mean concentration of 17.4 (± 48.1 SD) MP kg-1 and 6.78 (± 29.8 SD) mg kg-1, yet no microplastics within this size range were recorded in the pellets. Microplastic concentrations significantly differed between bait categories and companies, but microplastic characteristics did not vary. There was no correlation between microplastic contamination and the number of bait ingredients, but it was positively correlated with C:N ratio, indicating a higher contamination in baits with higher proportion of plant-based ingredients. We thus reveal that bait microplastics introduced accidentally during manufacturing and/or those originating from contaminated raw ingredients might be transferred into freshwaters. However, further studies are needed to quantify the relative importance of this cryptic source of contamination and how it influences microplastic levels in wild fish

Effect assessment of nano- and microplastics in freshwater ecosystems

The release of plastic waste into the environment has become one of the major water quality problems of the Anthropocene. Nanoplastics, with a size smaller than 0.1 µm, and microplastics, with a size between 0.1 µm and 5 mm, comprise the smallest particle fraction of plastic debris. Although the accumulation of nano- and microplastics is currently a major concern, studies addressing their effects on single species are scarce and nothing is known about their long-term effects at the community level. Freshwaters are particularly affected as sediments are known to accumulate nano- and microplastics due to the vicinity of sources and due to aggregation and biofouling processes and subsequent settling, which create hotspot areas that might pose a risk for benthic organisms. The general objective of this thesis is to assess threshold effect concentrations of nano- and microplastics in freshwater ecosystems, and to provide guidance on how such effects should be assessed in the context of risk assessment. For this, chronic single species tests were conducted with freshwater benthic macroinvertebrates exposed to nano- and microplastics via sediment following a standard setup to measure their individual threshold-effect concentrations. Benthic macroinvertebrates were exposed to polystyrene microplastic fragments, microplastics made by scraping and grinding second-hand tires and raspberry-shaped polystyrene nanoplastics with a palladium-core, separately. The tested benthic macroinvertebrates included the amphipods Gammarus pulex and Hyalella azteca, the isopod Asellus aquaticus, the worms Lumbriculus variegatus and Tubifex spp., and the bivalve Sphaerium corneum. The ingestion, retention and egestion of the polystyrene microplastics, the microplastics released from car tyres and the polystyrene nanoplastics were analysed for G. pulex using micro-Fourier Transformed Spectroscopy, image analysis and inductively coupled plasma mass spectrometry, respectively. In addition to the effects of nano- and microplastics on single species, we measured community threshold-effect concentrations for nano- and  microplastics. For this, trays containing sediment and nano or microplastics at five concentrations, including two environmentally realistic concentrations, were embedded at the bottom of a semi-artificial ditch containing a stable donor community. The donor community was allowed to colonize the trays and after 3 and 15 months, trays were retrieved, and species were identified and counted. Effects were assessed on the community composition, population sizes and species diversity. In this thesis, we also explore the potential use of in vitro toxicity tests to assess the risks of nanoplastics on human health, in this case with and without chemical mixtures originating from wastewater treatment plant effluent and surface waters. To this aim, we evaluated the genotoxicity of two spherical polystyrene nanoplastics with average sizes of 50 nm and 500 nm at four concentrations in three matrices using the Ames fluctuation test, which has the purpose of detecting base-pair and frameshift mutations in the genome of Salmonella typhimurium with and without metabolic activation. Then, following recently developed quality assessment methods for studies reporting abundance of microplastic in biota and water samples, we critically review 105 papers reporting microplastic effects on aquatic biota. For this, 20 Quality assurance/Quality control (QA/QC) criteria were defined within four main categories: particle characterization, experimental design, applicability for risk assessment and ecological relevance. With the aim of detecting knowledge gaps within effect studies with microplastic, we provide an overview of the study characteristics of the reviewed studies with respect to the size, shape and polymer type of the microplastic used, the tested species, the duration of the exposure, the endpoints studied and use or not of effect thresholds to report the results. Moreover, demonstrated and suggested effects and effect mechanisms reported in the reviewed papers are summarized and discussed, with the results of the quality evaluation applied as a method to assess the overall weight of evidence regarding probable ecologically relevant effects. Finally, we develop a tiered approach ecological risk assessment for microplastic using the data generated in this thesis and data taken from the literature

Quality criteria for microplastic effect studies in the context of risk assessment: A critical review

In the literature, there is widespread consensus that methods in plastic research need improvement. Current limitations in quality assurance and harmonization prevent progress in our understanding of what the true effects of microplastic in the environment are. Following the recent development of quality assessment methods for studies reporting concentrations in biota and water samples, we propose a method to assess the quality of microplastic effect studies. We reviewed 105 microplastic effect studies with aquatic biota, provided a systematic overview of their characteristics, developed 20 quality criteria in four main criteria categories (particle characterization, experimental design, applicability in risk assessment, and ecological relevance), propose a protocol for future effect studies with particles, and, finally, used all the information to define the weight of evidence with respect to demonstrated effect mechanisms. On average, studies scored 44.6% (range 20-77.5%) of the maximum score. No study scored positively on all criteria, reconfirming the urgent need for better quality assurance. Most urgent recommendations for improvement relate to avoiding and verifying background contamination, and to improving the environmental relevance of exposure conditions. The majority of the studies (86.7%) evaluated on particle characteristics properly, nonetheless it should be underlined that by failing to provide characteristics of the particles, an entire experiment can become irreproducible. Studies addressed environmentally realistic polymer types fairly well; however, there was a mismatch between sizes tested and those targeted when analyzing microplastic in environmental samples. In far too many instances, studies suggest and speculate mechanisms that are poorly supported by the design and reporting of data in the study. This represents a problem for decision-makers and needs to be minimized in future research. In their papers, authors frame 10 effects mechanisms as ‘suggested’, whereas 7 of them are framed as ‘demonstrated’. When accounting for the quality of the studies according to our assessment, three of these mechanisms remained. These are inhibition of food assimilation and/or decreased nutritional value of food, internal physical damage and external physical damage. We recommend that risk assessment addresses these mechanisms with higher priority.<br/

Nano- and microplastics affect the composition of freshwater benthic communities in the long term

Given the societal concern about the presence of nano- and microplastics in the environment, our nescience with respect to in situ effects is disturbing. Data on long-term implications under ecologically realistic conditions are particularly important for the risk assessment of nano- and microplastics. Here, we evaluate the long-term (up to 15 months) effects of five concentrations of nano- and microplastics on the natural recolonization of sediments by a macroinvertebrate community. Effects were assessed on the community composition, population sizes and species diversity. Nano- and microplastics adversely affected the abundance of macroinvertebrates after 15 months, which was caused by a reduction in the number of Naididae at the highest concentration (5% plastic per sediment dry weight). For some other taxa, smaller but still significant positive effects were found over time, altogether demonstrating that nano- and microplastics affected the community composition

Distribution of microplastic and small macroplastic particles across four fish species and sediment in an African lake

Pollution with microplastics has become an environmental concern worldwide. Yet, little information is available on the distribution of microplastics in lakes. Lake Ziway is one of the largest lakes in Ethiopia and is known for its fishing and drinking water supply. This study aims to examine the distribution of plastic particles, of all sizes (micro- and small macro-plastics) in four of the major fish species of the lake and in its shoreline sediment. The gastrointestinal tracts analysis showed that 35% of the sampled fishes ingested plastic particles. The median number of particles per fish was 4 (range 1–26). Benthic (Clarias gariepinus) and benthopelagic (Cyprinus carpio and Carassius carassius) fish species were found to contain a significantly higher number of plastic particles in comparison to the planktivorous fish species (Oreochromis niloticus). More fishes ingested plastic particles in the wet compared to the dry season. The maximum plastic size (40 mm fibre) was found in C. carpio. Estimated median mass of plastic particles in fish was 0.07 (0.0002–385.2) mg/kg_ww. Fish and sediment samples close to known potential sources of plastic particles had a higher plastic ingestion frequency (52% of the fish) and higher plastic concentration compared to the other parts of the lake. The median count and mass of plastic particles measured in sediment of the lake were 30,000 (400–124,000) particles/m3 and 764 (0.05–36,233) mg/kg_dw, respectively, the upper limits of which exceed known effect thresholds. Attenuated total reflection (ATR) - Fourier-transform infrared (FTIR) spectroscopy showed that polypropylene, polyethylene and alkyd-varnish were the dominant polymers in fishes and in sediment. The plastic particles size distributions were Log-linear and were identical for plastic particles found in fish and in sediment, suggesting strong benthic-pelagic coupling of plastic particles transfe

Effects of nanoplastics and microplastics on the growth of sediment-rooted macrophytes

Plastic debris of all sizes has been detected in marine, terrestrial and freshwater habitats. Effects of plastic debris on macrophytes have hardly been studied, despite their importance in aquatic ecosystems. We provide the first experimental study exploring nano- and microplastic effects on the growth of sediment-rooted macrophytes. Myriophyllum spicatum and Elodea sp. were exposed to sediments amended with six doses of polystyrene (PS) nanoplastic (50–190 nm, up to 3% sediment dry weight) and PS microplastic (20–500 μm, up to 10% dry weight) under laboratory conditions. Both macrophyte species were tested for changes in root and shoot dry weight (DW), relative growth rate (RGR), shoot to root ratio (S:R), main shoot length and side shoot length. Microplastics did not produce consistent dose-effect relationships on the endpoints tested, except that main shoot length was reduced for M. spicatum with increasing microplastic concentration. Nanoplastic significantly reduced S:R for both macrophytes as a result of increased root biomass compared to shoot biomass. Nanoplastic also caused a decrease in M. spicatum main shoot length; however, shoot biomass was not affected. Elodea sp. side shoot length, root and shoot biomass and RGR were positively correlated to the nanoplastic concentration. All effects occurred at higher than environmentally realistic concentrations, suggesting no immediate implications for ecological risks. Our study did not aim for the elucidation of the exact mechanistic processes that cause the effects, however, particle size seems to play an important factor

Microplastic effect thresholds for freshwater benthic macroinvertebrates

Now that microplastics have been detected in lakes, rivers and estuaries all over the globe, evaluating their effects on biota has become an urgent research priority. This is the first study that aims at determining the effect thresholds for a battery of six freshwater benthic macroinvertebrates with different species traits, using a wide range of microplastic concentrations. Standardized 28 d single species bioassays were performed under environmentally relevant exposure conditions using polystyrene microplastics (20 - 500 µm) mixed with sediment at concentrations ranging from 0 to 40% sediment dry weight (dw). Microplastics caused no effects on the survival of Gammarus pulex, Hyalella azteca, Asellus aquaticus, Sphaerium corneum and Tubifex spp. and no effects were found on the reproduction of Lumbriculus variegatus. No significant differences in growth were found for H. azteca, A. aquaticus, S. corneum, L. variegatus and Tubifex spp. However, G. pulex showed a significant reduction in growth (EC10=1.07% sediment dw) and microplastic uptake was proportional with microplastic concentrations in sediment. These results indicate that although the risks of environmentally realistic concentrations of microplastics may be low, they still may affect the biodiversity and the functioning of aquatic communities which after all also depend on the sensitive species