Plastics and the Environment

Plastics are persistent and pervasive throughout the environment and have now been reported from the deepest parts of the ocean to the tops of the highest and most remote mountains. There is a body of information on the sources, degradation, and transport of plastics as well as a variety of research investigating the ecotoxicological and wider ecological consequences of plastic ingestion and accumulation. Such knowledge has been obtained with developments in field and laboratory methods for plastic identification and then well-publicized in the media and wider public communications. However, although there has been a large focus on plastic pollution within the past decade, there is plenty that we do not yet know. Even within the past five years, sources of microplastics (1 μm–5 mm) to the environment have been confirmed that had not previously been considered, for example, road paints and tire wear particles. Initial research focused on plastic in the marine environment, but understanding on the accumulation and impacts in terrestrial and freshwater environments is growing. There is a substantial lack of basic science focused on the efficiency of solutions aimed at mitigating plastic pollution. This review highlights some recent (past five years) research on plastics in the environment, including investigations in accumulation, sources, distribution, impacts, solutions and provides directions for future work. </jats:p

Environmental Deterioration of Biodegradable, Oxo-biodegradable, Compostable, and Conventional Plastic Carrier Bags in the Sea, Soil, and Open-Air Over a 3-Year Period

There is clear evidence that discarded single-use carrier bags are accumulating in the environment. As a result, various plastic formulations have been developed which state they deteriorate faster and/or have fewer impacts on the environment because their persistence is shorter. This study examined biodegradable, oxo-biodegradable, compostable, and high-density polyethylene (i.e., a conventional plastic carrier bag) materials over a 3 year period. These materials were exposed in three natural environments; open-air, buried in soil, and submersed in seawater, as well as in controlled laboratory conditions. In the marine environment, the compostable bag completely disappeared within 3 months. However, the same compostable bag type was still present in the soil environment after 27 months but could no longer hold weight without tearing. After 9 months exposure in the open-air, all bag materials had disintegrated into fragments. Collectively, our results showed that none of the bags could be relied upon to show any substantial deterioration over a 3 year period in all of the environments. It is therefore not clear that the oxo-biodegradable or biodegradable formulations provide sufficiently advanced rates of deterioration to be advantageous in the context of reducing marine litter, compared to conventional bags

Characterisation, Quantity and Sorptive Properties of Microplastics Extracted From Cosmetics

Cosmetic products, such as facial scrubs, have been identified as potentially important primary sources of microplastics to the marine environment. This study characterises, quantifies and then investigates the sorptive properties of plastic microbeads that are used as exfoliants in cosmetics. Polyethylene microbeads were extracted from several products, and shown to have a wide size range (mean diameters between 164 to 327 μm). We estimated that between 4594 – 94500 microbeads could be released in a single use. To examine the potential for microbeads to accumulate and transport chemicals they were exposed to a binary mixture of 3H-phenanthrene and 14C-DDT in seawater. The potential for transport of sorbed chemicals by microbeads was broadly similar to that of polythene (PE) particles used in previous sorption studies. In conclusion, cosmetic exfoliants are a potentially important, yet preventable source of microplastic contamination in the marine environment

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

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