Evaluating the generation of microplastics from an unlikely source: The unintentional consequence of the current plastic recycling process

Unveiling the effects of micro and nano plastics in embryonic development

The improper disposal and degradation of plastics causes the formation and spread of micro and nano-sized plastic particles in the ecosystem. The widespread presence of these micro and nanoplastics leads to their accumulation in the biotic and abiotic components of the environment, thereby affecting the cellular and metabolic functions of organisms. Despite being classified as xenobiotic agents, information about their sources and exposure related to reproductive health is limited. Micro and nano plastic exposure during early developmental stages can cause abnormal embryonic development. It can trigger neurotoxicity and inflammatory responses as well in the developing embryo. In embryonic development, a comprehensive study of their role in pluripotency, gastrulation, and multi-differentiation potential is scarce. Due to ethical concerns associated with the direct use of human embryos, pluripotent cells and its 3D in vitro models (with cell lines) are an alternative source for effective research. Thus, the 3D Embryoid body (EB) model provides a platform for conducting embryotoxicity and multi-differentiation potential research. Pluripotent stem cells such as embryonic and induced pluripotent stem cells derived embryoid bodies (EBs) serve as a robust 3D in vitro model that mimics characteristics similar to that of human embryos. Thus, the 3D EB model provides a platform for conducting embryotoxicity and multi-differentiation potential research. Accordingly, this review discusses the significance of 3D in vitro models in conducting effective embryotoxicity research. Further, we also evaluated the possible sources/routes of microplastic generation and analyzed their surface chemistry and cytotoxic effects reported till date.

Plastics of the Future? An Interdisciplinary Review on Biobased and Biodegradable Polymers: Progress in Chemistry, Societal Views, and Environmental Implications

Global demand to reduce polymer waste and microplastics pollution has increased in recent years, prompting further research, development, and wider use of biodegradable and biobased polymers (BBPs). BBPs have emerged as promising alternatives to conventional plastics, with the potential to mitigate the environmental burdens of persistent plastic waste. We provide an updated perspective on their impact, five years after our last article, featuring several recent advances, particularly in exploring broader variety of feedstock, applying novel chemical modifications, and developing new functionalities. Life-cycle assessments reveal that environmental performance of BBPs depends on several factors including feedstock selection, production efficiency, and end-of-life management. Furthermore, the introduction of BBPs in several everyday life products has also influenced consumer perception, market dynamics, and regulatory frameworks. Although offering environmental advantages in specific applications, BBPs also raise concerns regarding their biodegradability under varying environmental conditions, potential microplastic generation, and soil health impacts. We highlight the need for a circular approach considering the entire polymer life cycle, from feedstock sourcing, modification and use, to end-of-life options. Interdisciplinary research, collaborative initiatives, and informed policymaking are crucial to unlocking the full potential of BBPs and exploiting their contribution to create a circular economy and more sustainable future.

Environmental consequences of interacting effects of changes in stratospheric ozone, ultraviolet radiation, and climate: UNEP Environmental Effects Assessment Panel, Update 2024

This Assessment Update by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) addresses the interacting effects of changes in stratospheric ozone, solar ultraviolet (UV) radiation, and climate on the environment and human health. These include new modelling studies that confirm the benefits of the Montreal Protocol in protecting the stratospheric ozone layer and its role in maintaining a stable climate, both at low and high latitudes. We also provide an update on projected levels of solar UV-radiation during the twenty-first century. Potential environmental consequences of climate intervention scenarios are also briefly discussed, illustrating the large uncertainties of, for example, Stratospheric Aerosol Injection (SAI). Modelling studies predict that, although SAI would cool the Earth's surface, other climate factors would be affected, including stratospheric ozone depletion and precipitation patterns. The contribution to global warming of replacements for ozone-depleting substances (ODS) are assessed. With respect to the breakdown products of chemicals under the purview of the Montreal Protocol, the risks to ecosystem and human health from the formation of trifluoroacetic acid (TFA) as a degradation product of ODS replacements are currently de minimis. UV-radiation and climate change continue to have complex interactive effects on the environment due largely to human activities. UV-radiation, other weathering factors, and microbial action contribute significantly to the breakdown of plastic waste in the environment, and in affecting transport, fate, and toxicity of the plastics in terrestrial and aquatic ecosystems, and the atmosphere. Sustainability demands continue to drive industry innovations to mitigate environmental consequences of the use and disposal of plastic and plastic-containing materials. Terrestrial ecosystems in alpine and polar environments are increasingly being exposed to enhanced UV-radiation due to earlier seasonal snow and ice melt because of climate warming and extended periods of ozone depletion. Solar radiation, including UV-radiation, also contributes to the decomposition of dead plant material, which affects nutrient cycling, carbon storage, emission of greenhouse gases, and soil fertility. In aquatic ecosystems, loss of ice cover is increasing the area of polar oceans exposed to UV-radiation with possible negative effects on phytoplankton productivity. However, modelling studies of Arctic Ocean circulation suggests that phytoplankton are circulating to progressively deeper ocean layers with less UV irradiation. Human health is also modified by climate change and behaviour patterns, resulting in changes in exposure to UV-radiation with harmful or beneficial effects depending on conditions and skin type. For example, incidence of melanoma has been associated with increased air temperature, which affects time spent outdoors and thus exposure to UV-radiation. Overall, implementation of the Montreal Protocol and its Amendments has mitigated the deleterious effects of high levels of UV-radiation and global warming for both environmental and human health.

Microplastic fragmentation into nanoplastics by water shear forces during wastewater treatment: Mechanical insights and theoretical analysis

Nanoplastics (NPs) are generated from the fragmentation of microplastics (MPs) through mechanical forces such as mixing, sonication and homogenization in wastewater treatment plants (WWTPs). Despite their environmental significance, the formation mechanisms and size distribution of NPs in WWTPs are not well understood. This study presents an in-depth investigation into the fragmentation mechanisms of polyethylene (PE) and polystyrene (PS) MPs, sized 250 μm and 106 μm, under simulated WWTP conditions. Our findings demonstrate that under water shear forces ranging from 32 to 100 kJ/L weathered PS and PE particles were further disintegrated into nano-sized particles. Nanoparticle tracking analysis results revealed a significant increase in NP numbers from 8.34 × 10⁸ to 1.54 × 101⁰ NPs/mL as the water shear force increased from 32 to 100 kJ/L. Notably, the smallest NP, measuring 54.2 nm, was produced from 106 μm PS particles at 100 kJ/L. Scanning electron microscope images confirmed micro-cracks on the particle surfaces as the dominant fragmentation mechanism. A robust correlation between experimental NP sizes and theoretical predictions underscores the continuous production of NPs during water treatment processes. These results offer groundbreaking insights into the transformation of MPs within WWTPs and underscore the urgent need for effective strategies to mitigate NP pollution.

Recycle or Not? An Exploration of Microplastic Generation During Plastic Processing via a Local Case Study

Microplastic (MP), an emerging pollutant, has been identified as a critical target in tackling plastic pollution. Although a plethora of studies have explored MP generation from various sources, limited attention has been paid to plastic processing. This study investigated MP (10 μm-5 mm) generation in virgin and waste plastic extrusion processing. MPs at a density of 2.13 × 105-9.79 × 107 (approximately 0.01-10.85 g) were generated when processing 1 t of plastic. Feedstock sources, polymer types, and pelletizing techniques were found to influence the process. With a moderate weight (270.58-527.34 t) but enormous amount (1.34 × 1016-2.63 × 1016) of MPs generated globally in 2022, plastic processing is an underestimated but vital source of MPs, emphasizing the need for MP inspection and appropriate removal technologies in the industry, especially for virgin plastic processing and water ring pelletizing. Further simulation indicated that up to 84.35% of MPs could be removed using commonly available materials in the investigated plastic processing facility, with a higher removal efficiency for larger-sized particles. In this regard, plastic recycling was superior to virgin plastic processing with fewer and larger-sized MPs generated, which could facilitate MP removal and should be fostered.

Plastic recycling: A panacea or environmental pollution problem

Increasing plastic waste is a critical global challenge to ecological and human health requiring focused solutions to reduce omnipresent plastic pollution in the environment. While recycling has been touted as one solution to counter plastic waste and resource utilization, it has been largely ineffective in offsetting the impact of rising global plastic production of more than 400 million metric tonnes annually, due to low global recycling rates of only 9%. Over three decades since implementing plastic resin codes, recycling has favoured thermoplastics, neglecting thermoset plastics. There is a constant need to enhance overall recycling efficiency by exploring advanced methods, as enormous gaps exist in fully unlocking the potential of plastic recycling. We identify critical gaps associated with plastic waste recycling and its potential environmental impacts. We discuss substantial progress in recycling technology, designs-for-recyclability with controlled chemical use, and economic incentives to expand markets for recycled plastics and to curb plastic leakage into the environment. Additionally, we highlight some emerging strategies and legally binding international policy instruments, such as the Global Plastics Treaty that require further development to reduce plastic waste and improve plastic recyclability.

Impact of bioplastic contamination on the mechanical recycling of conventional plastics

Quality assurance of a recycled product is currently one of the biggest issues that the plastic recycling industry faces. The purity of the input plastic waste stream has significant influence over the quality of the recycled product. This research evaluated the impact of polylactic acid (PLA) contamination within the input waste stream of high-density polyethylene (HDPE) recycling. The ultimate tensile strength was noted to reduce by 50% when PLA contamination was at 10%. An investigation into the effect that UVA radiation (simulating solar radiation) has on HDPE contaminated with PLA was also performed to determine the long-term effect of the bioplastic contamination. After UVA treatment, the ultimate tensile strength was reported to reduce by 51% when PLA contamination was only at 2.5%. A water contact angle analysis indicated the PLA contamination increased the hydrophilic nature of the HDPE sheets, potentially creating issues if the intended use of the recycled product was to store liquids. Microscopic analysis of the HDPE sheets contaminated with PLA showed deformations, ridges, cracks, and holes appear on the surface due to the immiscibility of the two polymers that was confirmed by FTIR analysis. Colour changes were visibly noted, with UVA exposure increasing the rate of colour change. Based on the findings in this study, PLA contamination of even 1% in a HDPE waste stream would significantly reduce the quality of the recycled product.

Human exposure to microplastics via the consumption of nonalcoholic beverages in various packaging materials: The case of Hong Kong

There is growing concern over microplastics in food and beverages, with potential implications for human health. However, little is known about microplastics in nonwater, nonalcoholic packaged beverages. This study addresses this research gap by implementing a dual-method approach that includes laboratory analysis to quantify microplastics in 50 packaged nonalcoholic beverages sold in Hong Kong, coupled with a beverage frequency questionnaire survey to provide a more accurate estimate of microplastic intake from these beverages. The beverages analysed spanned five categories-juice drinks, ready-to-drink teas, soda waters, soft drinks, and sports and energy drinks-and were packaged in four forms: aluminium cans, aseptic cartons, plastic bottles and glass bottles. The results showed that all beverage samples contained microplastics, with an average abundance of 42.1 ± 41.2 n/L (interquartile range [IQR]: 17.8-54.1 n/L), and these particles were predominantly smaller than 150 µm in size. Additionally, based on an annual beverage consumption rate of 157.3 ± 209.7 L/capita (IQR: 42.9-183.0 L/capita), it is estimated that Hong Kong adults ingest approximately 6200 microplastics per capita each year. The potential primary sources of these microplastics are atmospheric fallout and the packaging materials that endure mechanical stresses during the manufacturing and transportation of beverages. Compared to other known routes of exposure, including air, seafood, sugar, salt and honey, packaged nonalcoholic beverages present a comparable level of microplastic exposure, being lower than the first three but higher than the latter two. Nevertheless, the high prevalence of smaller microplastics in the samples is concerning. This study is considered to be important for food safety and human health, as it not only raises public awareness about microplastic contamination in packaged beverages but also serves as a call to action for the beverage industry to adopt more robust safety measures and for policymakers to revise packaging standards to reduce microplastic contamination and safeguard public health.

Machine Learning in the Analysis of the Mechanical Shredding Process of Polymer Recyclates

Artificial intelligence methods and techniques creatively support the processes of developing and improving methods for selecting shredders for the processing of polymer materials. This allows to optimize the fulfillment of selection criteria, which may include not only indicators related to shredding efficiency and recyclate quality but also energy consumption. The aim of this paper is to select methods of analysis based on artificial intelligence (AI) with independent rule extraction, i.e., data-based methods (machine learning-ML). This study took into account real data sets (feature matrix 1982 rows × 40 columns) describing the shredding process, including energy consumption used to optimize the parameters for the energy efficiency of the shredder. Each of the 1982 records in a .csv file (feature vector) has 40 numbers divided by commas. The data were divided into a learning set (70% of the data), a testing set (20% of the data), and a validation set (10% of the data). Cross-validation showed that the best model was LbfgsLogisticRegressionOva (0.9333). This promotes the development of the basis for an intelligent shredding methodology with a high level of innovation in the processing and recycling of polymer materials within the Industry 4.0 paradigm.

Chemical methods to remove microplastics from wastewater: A review

Microplastics (Mps) have emerged as a pervasive environmental concern, with their presence detected not only in freshwater ecosystems but also in drinking and bottled water sources. While extensive research has centered on understanding the origins, migration patterns, detection techniques, and ecotoxicological impacts of these contaminants, there remains a notable research gap about the strategies for Mps removal. This study reviews existing literature on chemical approaches for mitigating microplastic contamination within wastewater systems, focusing on coagulation precipitation, electrocoagulation, and advanced oxidation methods. Each approach is systematically explored, encompassing their respective mechanisms and operational dynamics. Furthermore, the comparative analysis of these three techniques elucidates their strengths and limitations in the context of MPs removal. By shedding light on the intricate mechanisms underlying these removal methods, this review contributes to the theoretical foundation of microplastic elimination from wastewater and identifies future research trajectories and potential challenges.

Global discharge of microplastics from mechanical recycling of plastic waste

The increasing production of plastic products and generation of plastic waste have had increasingly negative environmental impacts. Although recycling could reduce plastic pollution, microplastics can be generated during the process of crushing plastic products during mechanical recycling. We conducted crushing tests with 13 different plastics and documented the size distribution of particles generated. We then estimated the discharge of microplastics associated with recycling and their removal in wastewater treatment plants. We estimated that the global discharge of microplastics would increase from 0.017 Mt in 2000 to 0.749 Mt in 2060. Although mechanical recycling was estimated to account for 3.1% of the total emissions of microplastics for 2017, discharges of microplastics from plastic recycling may increase, even if plastic pollution from well-known sources decreases. Non-OECD (Organization for Economic Cooperation and Development) Asia could be a major discharging region and would play a vital role in reducing discharges of microplastics. Reduction of the discharge of microplastics will require less use of plastic products and upgrading wastewater treatment in many countries.

Microplastic pollution: Understanding microbial degradation and strategies for pollutant reduction

Microplastics are ubiquitous environmental pollutants with the potential for adverse impacts on ecosystems and human health. These particles originate from the fragmentation of larger plastic items, shedding from synthetic fibers, tire abrasions, and direct release from personal care products and industrial processes. Once released into the environment, microplastics can disrupt ecosystems, accumulate in organisms, cause physical harm, and carry chemical pollutants that pose risks to both wildlife and human health. There is an urgent need to comprehensively explore the multifaceted issue of microplastic pollution and understand microbial degradation to reduce environmental pollution caused by microplastics. This paper presents a comprehensive exploration of microplastics, including their types, composition, advantages, and disadvantages, as well as the journey and evolution of microplastic pollution. The impact of microplastics on the microbiome and microbial communities is elucidated, highlighting the intricate interactions between microplastics and microbial ecosystems. Furthermore, the microbial degradation of microplastics is discussed, including the identification, characterization, and culturing methods of microplastic-degrading microorganisms. Mechanisms of microplastic degradation and the involvement of microbial enzymes are elucidated to shed light on potential biotechnological applications. Strategies for reducing microplastic pollution are presented, encompassing policy recommendations and the importance of enhanced waste management practices. Finally, the paper addresses future challenges and prospects in the field, emphasizing the need for international collaboration, research advancements, and public engagement. Overall, this study underscores the urgent need for concerted efforts to mitigate microplastic pollution and offers valuable insights for researchers, policymakers, and stakeholders involved in environmental preservation.