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

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A revisited conceptualization of plastic pollution accumulation in marine environments: Insights from a social ecological economics perspective

The proliferation of synthetic polymer fragments in marine ecosystems has become a prominent issue within recent years, and its disastrous implications on marine species as well as associated social and economic costs have been extensively documented. A narrow perspective of analysis has characterized current conceptualizations of the phenomenon, which is further resembled in the proposed approaches to tackle the problem. Based on a critical realist philosophy of science, this article aims to investigate the fundamental and interdisciplinary dynamics underpinning the current production, consumption and post-consumption lifecycle of plastics, by abstracting transfactual relationships. These then provide the basis to develop a conceptual model for understanding the phenomenon in a more comprehensive manner, and form a framework to assess proposed policy responses for addressing the issue. Thereby the conceptual model draws upon four fields of knowledge: (i) thermodynamic laws and its relevance for economics, (ii) behavioral psychology and resulting limitations of individuals’ decision-making under conscious consumer theory, (iii) power theories of political science, and (iv) ethical considerations. The article suggests that ontological and epistemological discrepancies across disciplines, as well as the consequential neglect of several mechanisms have so far limited scientific progress to guide meaningful political action.

Clemens W. Gattringer, Marine Policy, Available online 18 December 2017, In Press

The article

Microplastics and nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport

Plastic litter is widely acknowledged as a global environmental threat and poor management and disposal lead to increasing levels in the environment. Of recent concern is the degradation of plastics from macro- to micro- and even to nanosized particles smaller than 100 nm in size. At the nanoscale, plastics are difficult to detect and can be transported in air, soil and water compartments. While the impact of plastic debris on marine and fresh waters and organisms has been studied, the loads, transformations, transport, and fate of plastics in terrestrial and subsurface environments are largely overlooked. In this review, we first present estimated loads of plastics in different environmental compartments. We also provide a critical review of the current knowledge vis-à-vis nanoplastic (NP) and microplastic (MP) aggregation, deposition, and contaminant co-transport in the environment. Important factors that affect aggregation and deposition in natural subsurface environments are identified and critically analyzed. Factors affecting contaminant sorption onto plastic debris are discussed, and we show how polyethylene generally exhibits a greater sorption capacity than other plastic types. Finally, we highlight key knowledge gaps that need to be addressed to improve our ability to predict the risks associated with these ubiquitous contaminants in the environment by understanding their mobility, aggregation behavior and their potential to enhance the transport of other pollutants.

Olubukola Alimi, Jeffrey Farner Budarz, Laura M Hernandez, and Nathalie Tufenkji, Environ. Sci. Technol., Just Accepted Manuscript, December 21, 2017
 

Enzymatic purification of microplastics in environmental samples

Micro-Fourier transform infrared (micro-FTIR) spectroscopy and Raman spectroscopy enable the reliable identification and quantification of microplastics (MPs) in the lower micron range. Since concentrations of MPs in the environment are usually low, the large sample volumes required for these techniques lead to an excess of coenriched organic or inorganic materials. While inorganic materials can be separated from MPs using density separation, the organic fraction impedes the ability to conduct reliable analyses. Hence, the purification of MPs from organic materials is crucial prior to conducting an identification via spectroscopic techniques. Strong acidic or alkaline treatments bear the danger of degrading sensitive synthetic polymers. We suggest an alternative method, which uses a series of technical grade enzymes for purifying MPs in environmental samples. A basic enzymatic purification protocol (BEPP) proved to be efficient while reducing 98.3 ± 0.1% of the sample matrix in surface water samples. After showing a high recovery rate (84.5 ± 3.3%), the BEPP was successfully applied to environmental samples from the North Sea where numbers of MPs range from 0.05 to 4.42 items m–3. Experiences with different environmental sample matrices were considered in an improved and universally applicable version of the BEPP, which is suitable for focal plane array detector (FPA)-based micro-FTIR analyses of water, wastewater, sediment, biota, and food samples.

Löder M., Imhof H. K., Ladehoff M. and al., Environ. Sci. Technol., 2017, 51 (24), pp 14283–14292

The article

Occurrence of microplastics and its pollution in the environment: A review

The pollution caused by microplastics in seas and fresh water is of growing environmental concern due to their slow degradability, biological ingestion by fish and other aquatic living organisms, and acting as carriers to concentrate and transport synthetic and persistent organic pollutants. As well as microplastics, chemical additives added to plastics during manufacture which may leach out upon ingestion, will enter food chains and potentially cause humans serious health problems.

Regulations in many counties/regions have been setup or to be implemented to ban the production/sale and use of primary microplastics (e.g., microbeads), which could reduce microplastics in the aquatic environment in certain level. However, the fragments from larger plastic items (second microplastics) are major contributors, and then new legislations have to be proposed and implemented in order to substantially reduce the amounts of microplastics in the environment and the associated environmental impact. Moreover, approaches and measures are to be taken by encouraging companies and all users to adopt the Reduce–Reuse–Recycle circular economy as this will represent a cost-effective way of reducing the quantity of plastic objects and microplastics particles entering and gathering in the marine/aquatic environment.

Jia-Qian Jiang, Sustainable Production and Consumption, Available online 21 November 2017, In Press

The article

Impact of microplastic beads and fibers on waterflea (Ceriodaphnia dubia) survival, growth, and reproduction: implications of single and mixture exposures

There is limited knowledge regarding the adverse effects of wastewater-derived microplastics, particularly fibers, on aquatic biota. In this study, we examined the acute (48 h) and chronic (8 d) effects of microplastic polyester fibers and polyethylene (PE) beads on freshwater zooplankton Ceriodaphnia dubia. We also assessed the acute response of C. dubia to a binary mixture of microplastic beads and fibers for the first time. Acute exposure to fibers and PE beads both showed a dose-dependent effect on survival. An equitoxic binary mixture of beads and fibers resulted in a toxic unit of 1.85 indicating less than additive effects. Chronic exposure to lower concentrations did not significantly affect survival of C. dubia, but a dose-dependent effect on growth and reproduction was observed. Fibers showed greater adverse effects than PE beads. While ingestion of fibers was not observed, scanning electron microscopy showed carapace and antenna deformities after exposure to fibers, with no deformities observed after exposure to PE beads. While much of the current research has focused on microplastic beads, our study shows that microplastic fibers pose a greater risk to C. dubia, with reduced reproductive output observed at concentrations within an order of magnitude of reported environmental levels.

Shima Ziajahromi, Anupama Kumar, Peta A. Neale, and Frederic D. L. Leusch, Environ. Sci. Technol., Article ASAP, October 23, 2017

Are we underestimating microplastic contamination in aquatic environments?

Plastic debris, specifically microplastic in the aquatic environment, is an escalating environmental crisis. Efforts at national scales to reduce or ban microplastics in personal care products are starting to pay off, but this will not affect those materials already in the environment or those that result from unregulated products and materials. To better inform future microplastic research and mitigation efforts this study (1) evaluates methods currently used to quantify microplastics in the environment and (2) characterizes the concentration and size distribution of microplastics in a variety of products. In this study, 50 published aquatic surveys were reviewed and they demonstrated that most (~80%) only account for plastics ≥ 300 μm in diameter. In addition, we surveyed 770 personal care products to determine the occurrence, concentration and size distribution of polyethylene microbeads. Particle concentrations ranged from 1.9 to 71.9 mg g−1 of product or 1649 to 31,266 particles g−1 of product. The large majority ( > 95%) of particles in products surveyed were less than the 300 μm minimum diameter, indicating that previous environmental surveys could be underestimating microplastic contamination. To account for smaller particles as well as microfibers from synthetic textiles, we strongly recommend that future surveys consider methods that materials < 300 μm in diameter.

Jeremy L. Conkle, Christian D. Báez Del Valle, Jeffrey W. Turner, Environmental Management, Environmental Management, , Volume 61, Issue 1, pp 1–8

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