Microplastics in the Environment

© The Royal Society of Chemistry 2019. Microplastics are small pieces of plastic debris less than 5 mm in diameter. They have accumulated in the environment as a consequence of: the direct release of small particles, such as those used in cosmetics; or as a consequence of wear, for example fibres released from textiles. The main source of microplastic is considered to be the fragmentation of larger items of plastics in the environment. Microplastics are widely distributed in freshwater and marine environments including remote locations such as the arctic and deep sea. A wide range of organisms are known to ingest microplastics and laboratory studies indicate the potential for harmful effects. Plastic debris can also transport co-contaminants including chemical additives and pollutants sorbed from sea water. These chemicals can be released to organisms upon ingestion, but there is little evidence that plastics provide an important pathway leading to toxicological effects in environmentally relevant scenarios. Removing microplastics from the environment is impractical and the most effective solutions are to minimise the release of plastics to the environment as litter. In this regard much could be achieved by actions to reduce the accumulation of larger items of litter such as packaging, which will eventually fragment into microplastics

Marine Litter: Are There Solutions to This Environmental Challenge?

Between 1950 and 2015, it is estimated that 6300 Mt of plastic waste have been produced. Of this,around the 80% ended up in landfills or in the natural environment [1]. The combination of this typeof waste disposal and of the durability and resistance to degradation of plastics, has led to the currentubiquitous and abundant presence of plastic debris in the environment. The greatest warning signalof this plastic pollution problems has come from marine environment, where it is estimated that 75%of all marine litter is plastic and this debris has been reported to be accumulating at the sea surface[2], on shorelines of the most remote islands [3], in the deep sea [4] and in arctic sea ice [5]. Despitefirst reports on marine plastic litter dates back to the 1960s (Kenyon & Kridler, 1969) only recentlyit has been recognized as a pervasive global issue [1].There is a range of evidence on the harm caused by marine litter; with negative impacts oncommercial fisheries, maritime industries and infrastructures, as well as on a wide range of marineorganisms as a consequence of entanglement and ingestion [6].Plastic debris can be defined and described according to different characteristics including origin,polymer type, shape, size, colour or original use. However, the main classification used is about thesize: macroplastic (\u3e20 mm diameter), mesoplastic (5–20 mm) and microplastic (\u3c5 mm) [7]. Sincemacroplastics are more visible, they have been for long time considered as one of the most concerningforms of plastic pollution. In fact, these items can be more easily recognized and categorisedaccording to their original usage (i.e. fishing, packaging, or sewage related debris). More subtle andcomplicate is instead the pollution related to the presence of microplastics that, with accumulatingdata on the impact and consequences of such debris, has received increasing research interest andcurrently represents one of the greatest challenges in the fight against plastic pollutio

Microplastics: an introduction to environmental transport processes

Microplastic pollution is widespread across the globe, pervading land, water, and air. These environments are commonly considered independently, however, in reality these are closely linked. This review gives an overview of the background knowledge surrounding sources, fate and transport of microplastics within the environment. We introduce a new “Plastic Cycle” concept in order to better understand the processes influencing flux and retention of microplastics between and across the wide range of environmental matrices. As microplastics are a pervasive, persistent and potentially harmful pollutant, an understanding of these processes will allow for assessment of exposure to better determine the likely long‐term ecological and human health implications of microplastic pollution

Structure of Colloid-Polymer Suspensions

We discuss structural correlations in mixtures of free polymer and colloidal particles based on a microscopic, 2-component liquid state integral equation theory. Whereas in the case of polymers much smaller than the spherical particles the relevant polymer degree of freedom is the center of mass, for polymers larger than the (nano-) particles conformational rearrangements need to be considered. They have the important consequence that the polymer depletion layer exhibits two widely different length scales, one of the order of the particle radius, the other of the order of the polymer radius or the polymer density screening length in dilute or semidilute concentrations, respectively. Their consequences on phase stability and structural correlations are discussed extensively.Comment: 37 pages, 17 figures; topical feature articl

Self-Consistent Field study of Polyelectrolyte Brushes

We formulate a self-consistent field theory for polyelectrolyte brushes in the presence of counterions. We numerically solve the self-consistent field equations and study the monomer density profile, the distribution of counterions, and the total charge distribution. We study the scaling relations for the brush height and compare them to the prediction of other theories. We find a weak dependence of the brush height on the grafting density.We fit the counterion distribution outside the brush by the Gouy-Chapman solution for a virtual charged wall. We calculate the amount of counterions outside the brush and find that it saturates as the charge of the polyelectrolytes increases

Message in a bottle: open source technology to track the movement of plastic pollution

This is the final version. Available on open access from Public Library of Science via the DOI in this recordData Availability: Data used in this study are available in the Movebank open data repository at https://www.movebank.org/cms/webapp?gwt_fragment=page=studies,path=study1271155477 (Movebank ID No. 1271155477).Rivers worldwide are now acting as major transport pathways for plastic pollution and discharge large quantities of waste into the ocean. Previous oceanographic modelling and current drifter data have been used to predict the movement and accumulation of plastic pollution in the marine environment, but our understanding of the transport and fate through riparian systems is still largely unknown. Here we undertook a proof of concept study by applying open source tracking technology (both GPS (Global Positing System) cellular networks and satellite technology), which have been successfully used in many animal movement studies, to track the movements of individual plastic litter items (500 ml PET (polyethylene terephthalate) drinks bottles) through the Ganges River system (known as the Ganga in India and the Padma and Meghna in Bangladesh, hereafter known as the Ganges) and the Bay of Bengal. Deployed tags were successfully tracked through the Ganges river system and into the Bay of Bengal marine system. The “bottle tags” were designed and built (e.g. shape, size, buoyancy) to replicate true movement patterns of a plastic bottle. The maximum distance tracked to date is 2845 km over a period of 94 days. We discuss lessons learnt from the development of these plastic litter tags, and outline how the potential widespread use of this open source technology has the ability to significantly increase understanding of the location of accumulation areas and the timing of large inputs of plastic pollution into the aquatic system. Furthermore, “bottle tags” may act as a powerful tool for stimulating social behaviour change, informing science-based policy, and as valuable educational outreach tools for public awareness.National Geographic Societ

Synaptic Responses Evoked by Tactile Stimuli in Purkinje Cells in Mouse Cerebellar Cortex Crus II In Vivo

Sensory stimuli evoke responses in cerebellar Purkinje cells (PCs) via the mossy fiber-granule cell pathway. However, the properties of synaptic responses evoked by tactile stimulation in cerebellar PCs are unknown. The present study investigated the synaptic responses of PCs in response to an air-puff stimulation on the ipsilateral whisker pad in urethane-anesthetized mice.Thirty-three PCs were recorded from 48 urethane-anesthetized adult (6-8-week-old) HA/ICR mice by somatic or dendritic patch-clamp recording and pharmacological methods. Tactile stimulation to the ipsilateral whisker pad was delivered by an air-puff through a 12-gauge stainless steel tube connected with a pressurized injection system. Under current-clamp conditions (I = 0), the air-puff stimulation evoked strong inhibitory postsynaptic potentials (IPSPs) in the somata of PCs. Application of SR95531, a specific GABA(A) receptor antagonist, blocked IPSPs and revealed stimulation-evoked simple spike firing. Under voltage-clamp conditions, tactile stimulation evoked a sequence of transient inward currents followed by strong outward currents in the somata and dendrites in PCs. Application of SR95531 blocked outward currents and revealed excitatory postsynaptic currents (EPSCs) in somata and a temporal summation of parallel fiber EPSCs in PC dendrites. We also demonstrated that PCs respond to both the onset and offset of the air-puff stimulation.These findings indicated that tactile stimulation induced asynchronous parallel fiber excitatory inputs onto the dendrites of PCs, and failed to evoke strong EPSCs and spike firing in PCs, but induced the rapid activation of strong GABA(A) receptor-mediated inhibitory postsynaptic currents in the somata and dendrites of PCs in the cerebellar cortex Crus II in urethane-anesthetized mice

Sirtinol Treatment Reduces Inflammation in Human Dermal Microvascular Endothelial Cells

Histone deacetylases (HDAC) are key enzymes in the epigenetic control of gene expression. Recently, inhibitors of class I and class II HDAC have been successfully employed for the treatment of different inflammatory diseases such as rheumatoid arthritis, colitis, airway inflammation and asthma. So far, little is known so far about a similar therapeutic effect of inhibitors specifically directed against sirtuins, the class III HDAC. In this study, we investigated the expression and localization of endogenous sirtuins in primary human dermal microvascular endothelial cells (HDMEC), a cell type playing a key role in the development and maintenance of skin inflammation. We then examined the biological activity of sirtinol, a specific sirtuin inhibitor, in HDMEC response to pro-inflammatory cytokines. We found that, even though sirtinol treatment alone affected only long-term cell proliferation, it diminishes HDMEC inflammatory responses to tumor necrosis factor (TNF)α and interleukin (IL)-1β. In fact, sirtinol significantly reduced membrane expression of adhesion molecules in TNFã- or IL-1β-stimulated cells, as well as the amount of CXCL10 and CCL2 released by HDMEC following TNFα treatment. Notably, sirtinol drastically decreased monocyte adhesion on activated HDMEC. Using selective inhibitors for Sirt1 and Sirt2, we showed a predominant involvement of Sirt1 inhibition in the modulation of adhesion molecule expression and monocyte adhesion on activated HDMEC. Finally, we demonstrated the in vivo expression of Sirt1 in the dermal vessels of normal and psoriatic skin. Altogether, these findings indicated that sirtuins may represent a promising therapeutic target for the treatment of inflammatory skin diseases characterized by a prominent microvessel involvement