Combined effects of microplastics and chemical contaminants on the organ toxicity of zebrafish (Danio rerio)

Microplastics contamination of the aquatic environment is considered a growing problem. The ingestion of microplastics has been documented for a variety of aquatic animals. Studies have shown the potential of microplastics to affect the bioavailability and uptake route of sorbed co-contaminants of different nature in living organisms. Persistent organic pollutants and metals have been the co-contaminants majorly investigated in this field. The combined effect of microplastics and sorbed co-contaminants in aquatic organisms still needs to be properly understood. To address this, we have subjected zebrafish to four different feeds: A) untreated feed; B) feed supplemented with microplastics (LD-PE 125–250 µm of diameter); C) feed supplemented with 2% microplastics to which a mixture of PCBs, BFRs, PFCs and methylmercury were sorbed; and D) feed supplemented with the mixture of contaminants only. After 3 weeks of exposure fish were dissected and liver, intestine, muscular tissue and brain were extracted. After visual observation, evaluation of differential gene expression of some selected biomarker genes in liver, intestine and brain were carried out. Additionally, quantification of perfluorinated compounds in liver, brain, muscular tissue and intestine of some selected samples were performed. The feed supplemented with microplastics with sorbed contaminants produced the most evident effects especially on the liver. The results indicate that microplastics alone does not produce relevant effects on zebrafish in the experimental conditions tested; on the contrary, the combined effect of microplastics and sorbed contaminants altered significantly their organs homeostasis in a greater manner than the contaminants alone.

Sandra Rainieri, Nadia Conlledo, Bodil K. Larsen, Kit Granby, Alejandro Barranco, Environmental Research, Volume 162, April 2018, Pages 135-143

The article

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In vitro effects of virgin microplastics on fish head-kidney leucocyte activities

Microplastics are well-documented pollutants in the marine environment that result from production or fragmentation of larger plastic items. The knowledge about the direct effects of microplastics on immunity, including fish, is still very limited. We investigated the in vitro effects of microplastics [polyvinylchloride (PVC) and polyethylene (PE)] on gilthead seabream (Sparus aurata) and European sea bass (Dicentrarchus labrax) head-kidney leucocytes (HKLs). After 1 and 24 h of exposure of HKLs with 0 (control), 1, 10 and 100 mg mL−1 MPs in a rotatory system, cell viability, innate immune parameters (phagocytic, respiratory burst and peroxidase activities) and the expression of genes related to inflammation (il1b), oxidative stress (nrf2, prdx3), metabolism of xenobiotics (cyp1a1, mta) and cell apoptosis (casp3) were studied. Microplastics failed to affect the cell viability of HKLs. In addition, they provoke very few significant effects on the main cellular innate immune activities, as decrease on phagocytosis or increase in the respiratory burst of HKLs with the highest dose of microplastics tested. Furthermore, microplastics failed to affect the expression of the selected genes on sea bass or seabream, except the nrf2 which was up-regulated in seabream HKLs incubated with the highest doses. Present results seem to suggest that continue exposure of fish to PVC or PE microplastics could impair fish immune parameters probably due to the oxidative stress produced in the fish leucocytes.

Cristóbal Espinosa, José María García Beltrán, María Angeles Esteban, Alberto Cuesta, Environmental Pollution, Volume 235, April 2018, Pages 30–38

The article

Do polyethylene microplastic beads alter the intestinal uptake of Ag in rainbow trout (Oncorhynchus mykiss)? Analysis of the MP vector effect using in vitro gut sacs

Microplastic (MP) vector effects have been well described in the literature but surprisingly little is in known about the impact of MPs on the intestinal uptake of contaminants. The present study aimed to determine whether the intestinal fate of Ag was affected by the presence of polyethylene MP beads. Ag (added as 110mAg) was introduced into the lumen of rainbow trout (Oncorhynchus mykiss) anterior/mid-intestine gut sac preparations as Ag only, Ag and MPs (co-exposure) and Ag-incubated MPs (where Ag was adsorbed to the MP). Results show that after 3 h exposure the distribution of accumulated Ag between the four intestinal compartments (mucus layer, mucosal epithelium, muscle layer and serosal saline) was not affected by either MP condition when compared to Ag alone (p > 0.05, One way ANOVA). Across all treatment groups mucus layer binding dominated (54.2–72.6%) whereas relatively little Ag was transported to the blood compartment (i.e. combined muscle layer and serosal saline compartments, 8.5–15.0%). Accompanying adsorption/desorption studies were performed in relevant media. Over 24 h, 60.6± 2.9% of the available Ag in artificial freshwater adhered to the surface of the PE MPs. In pH adjusted luminal fluids (pH 2.2, 4.1, 7.4 and 9.8) that span the range of conditions encountered within the rainbow trout digestive tract, there was almost complete dissociation at acidic pHs within 3 h (<2% remaining on MPs at both pH 2.2 and pH 4.1). Such pHs are typical of piscine stomach. Based on our finding we suggest that following the ingestion of MPs with adsorbed pollutants, desorption would occur prior to entering the site of uptake. The MPs themselves have no impact on the trans-epithelial transport of the contaminant, but the net result of the MP vector effect is to potentially introduce labile contaminant forms into the intestine.

F. Khan, D. Boyle, E. Chang, N. R. Bury, Environmental Pollution,Volume 231, Part 1, December 2017, Pages 200-206

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Microplastic and mesoplastic contamination in canned sardines and sprats

No report was found on the occurrence of microplastics in processed seafood products that are manufactured for direct human consumption. This study investigates the potential presence of micro- and mesoplastics in 20 brands of canned sardines and sprats originating from 13 countries over 4 continents followed by their chemical composition determination using micro-Raman spectroscopy. The particles were further inspected for their inorganic composition through energy-dispersive X-ray spectroscopy (EDX). Plastic particles were absent in 16 brands while between 1 and 3 plastic particles per brand were found in the other 4 brands. The most abundant plastic polymers were polypropylene (PP) and polyethylene terephthalate (PET). The presence of micro- and mesoplastics in the canned sardines and sprats might be due to the translocation of these particles into the edible tissues, improper gutting, or the result of contamination from the canneries. The low prevalence of micro- and mesoplastics sized > 149 μm, and the absence of potentially hazardous inorganic elements on them, might indicate the limited health risks associated with their presence in canned sardines and sprats. Due to the possible increase in micro- and mesoplastic loads in seafood products over time, the findings of this study suggest their quantification to be included as one of the components of food safety management systems.

Ali Karami, Abolfazl Golieskardi, Cheng Keong Choo, Vincent Larat, Samaneh Karbalaei, Babak Salamatinia, Science of The Total Environment, Volume 612, 15 January 2018, Pages 1380-1386

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Microplastics: minuscule particles with big consequences?

Since the mass production of plastics, contamination of the marine environment with these persistent synthetic materials has become an ever-increasing problem. Lately, it has become clear that microplastics play a big part in this. These small plastic particles (< 5mm) are ubiquitous in seawaterand sediments. There are various entry ways, such as fragmentation of macroplastics and drainage of primary microplastic via wastewater. Recent studies have shown that microplastics may be ingested by numerous marine organisms. This could result in diverse health effects, including mechanical injury and cellular toxicity. Adverse effects of microplastics are possibly enhanced by the contamination of these plastic particles with toxic chemicals. Furthermore, microplastics and microplastic contaminants could accumulate in the food chain, eventually affecting humans. Despite the growing number of publications on microplastics, there are still many unanswered questions regarding this topic. In this article, the contemporary knowledge of microplastics in the marine environment is provided.

S. Knoll, A. Decostere, A.M. Declercq, VLAAMS DIERGENEESKUNDIG TIJDSCHRIFT, 86 (4): 203-212, JUL-AUG 2017

The article

Digestible fluorescent coatings for cumulative quantification of microplastic ingestion

The ubiquitous presence of microplastics in the environment makes it imperative to understand their effects. In particular, we must understand exposure, i.e., how many microplastics are ingested by organisms. This has proved difficult because counting microplastics in an organism’s gut content provides only a snapshot in time. Here, we show a method that uses a digestible fluorescent coating (DFC) to quantify cumulative microplastic ingestion. Our method enables precise and automated enumeration of cumulative microplastic ingestion with the flexibility to track different microplastic types and sizes with distinct fluorescent tracers. We confirm the coating is not acutely toxic and is not preferentially ingested by several invertebrate species. This method provides a unique and reliable approach to quantify cumulative microplastic ingestion in laboratory exposure studies, and can be used to advance our understanding of the impact of microplastics to wildlife.

Evan G. Karakolis, Brian Nguyen, Jae Bem You, Percival J. Graham, Chelsea M. Rochman and David Sinton, Environ. Sci. Technol. Lett., Article ASAP, December 26, 2017

The article

Pollutants in plastics within the north Pacific subtropical gyre

Here we report concentrations of pollutants in floating plastics from the North Pacific accumulation zone (NPAC). We compared chemical concentrations in plastics of different types and sizes, assessed ocean plastic potential risks using sediment quality criteria, and discussed the implications of our findings for bioaccumulation. Our results suggest that at least a fraction of the NPAC plastics is not in equilibrium with the surrounding seawater. For instance, ‘hard plastic’ samples had significantly higher PBDE concentrations than ‘nets and ropes’ samples, and 29% of them had PBDE composition similar to a widely used flame-retardant mixture. Our findings indicate that NPAC plastics may pose a chemical risk to organisms as 84% of the samples had at least one chemical exceeding sediment threshold effect levels. Furthermore, our surface trawls collected more plastic than biomass (180 times on average), indicating that some NPAC organisms feeding upon floating particles may have plastic as a major component of their diets. If gradients for pollutant transfer from NPAC plastic to predators exist (as indicated by our fugacity ratio calculations), plastics may play a role in transferring chemicals to certain marine organisms.

Qiqing Chen, Julia Reisser, Serena Cunsolo, Christiaan Kwadijk, Michiel Kotterman, Maira Proietti, Boyan Slat, Francesco Ferrari, Anna Schwarz, Aurore Levivier, Daqiang Yin, Henner Hollert, and Albert A. Koelmans, Environ. Sci. Technol., Just Accepted Manuscript, 2017