Generation of nanoplastics during the photoageing of low-density polyethylene

Microplastic accumulation dynamics in Han river headwaters: Sediment interactions and environmental implication

The prevalence of microplastic (MP) contamination has become a significant environmental concern due to its pervasive nature and persistent effects. While sediments are considered major repositories for MPs, information on their spatial distribution within these matrices is insufficient. This research examined both the horizontal and vertical presence of MPs in the sediments surrounding Lake Paldang in South Korea, alongside a comprehensive evaluation of the physicochemical characteristics of the samples obtained. The total content of MPs varied from 2.15 to 122.2 particles g-1. The average contents of MPs on surface sediments were 40.47, 34.14, 5.01, and 8.19 particles g-1 in north mainstream (NM), south mainstream (SM), tributary (TB), and Tributary catchment (TC) based on Sonae Island, Gyeongan stream, respectively. The most abundant MP types were polyethylene (PE), polytetrafluoroethylene (PTFE), and polypropylene (PP), accounting for more than 70% of the total MPs. The most abundant sizes of MPs were within 45-100 µm. At all sediment depths, polymers were distributed in the order PE, PP, and polyester in NM, SM, and TC, respectively, whereas PTFE mainly occurred in the surface layer. MPs distribution also exhibited seasonal variation as larger inflows and flow rates varied with season.

Research on the Migration and Adsorption Mechanism Applied to Microplastics in Porous Media: A Review

In recent years, microplastics (MPs) have emerged as a significant environmental pollutant, garnering substantial attention for their migration and transformation behaviors in natural environments. MPs frequently infiltrate natural porous media such as soil, sediment, and rock through various pathways, posing potential threats to ecological systems and human health. Consequently, the migration and adsorption mechanisms applied to MPs in porous media have been extensively studied. This paper aims to elucidate the migration mechanisms of MPs in porous media and their influencing factors through a systematic review. The review encompasses the characteristics of MPs, the physical properties of porous media, and hydrodynamic factors. Additionally, the paper further clarifies the adsorption mechanisms of MPs in porous media to provide theoretical support for understanding their environmental behavior and fate. Furthermore, the current mainstream detection techniques for MPs are reviewed, with an analysis of the advantages, disadvantages, and applications of each technique. Finally, the paper identifies the limitations and shortcomings of current research and envisions future research directions.

Sea surface microplastics in the Galapagos: Grab samples reveal high concentrations of particles <200 μm in size

Plastic pollution in the oceans is increasing, yet most global sea surface data is collected using plankton nets which limits our knowledge of the smaller and more bioaccessible size fraction of microplastics (<5 mm). We sampled the biodiverse coastal waters of the Galapagos Island of San Cristobal, comparing two different microplastic sampling methodologies; 1 l whole seawater grab samples filtered to 1.2 μm and sea surface plankton tows with a net mesh size of 200 μm. Our data reveal high concentrations of microplastics in Galapagos coastal waters surrounding the urban area, averaging 11.5 ± 1.48 particles l-1, with a four-order of magnitude increase in microplastic abundance observed using grab sampling compared with 200 μm plankton nets. This increase was greater when including anthropogenic cellulose particles, averaging 19.8 ± 1.86 particles l-1. Microplastic and anthropogenic cellulose particles smaller than 200 μm comprised 44 % of the particles from grab samples, suggesting previous estimates of microplastic pollution based on plankton nets likely miss and therefore underestimate these smaller particles. The particle characteristics and distribution of these smaller particles points strongly to a local input of cellulosic fibres in addition to the microplastic particles transported longer distances via the Humbolt current found across the surface seawater of the Galapagos. Improving our understanding of particle characteristics and distributions to highlight likely local sources will facilitate the development of local mitigation and management plans to reduce the input and impacts of microplastics to marine species, not just in the Galapagos but globally.

Sunlight-Driven Photochemical Removal of Polypropylene Microplastics from Surface Waters Follows Linear Kinetics and Does Not Result in Fragmentation

Floating microplastics are susceptible to sunlight-driven photodegradation, which can convert plastic carbon to dissolved organic carbon (DOC) and can facilitate microplastic fragmentation by mechanical forces. To understand the photochemical fate of sub-millimeter buoyant plastics, ∼0.6 mm polypropylene microplastics were photodegraded while tracking plastic mass, carbon, and particle size distributions. Plastic mass loss and carbon loss followed linear kinetics. At most time points DOC accumulation accounted for under 50% of the total plastic carbon lost. DOC accumulation followed sigmoidal kinetics, not the exponential kinetics previously reported for shorter irradiations. Thus, we suggest that estimates of plastic lifespan based on exponential DOC accumulation are inaccurate. Instead, linear plastic-C mass and plastic mass loss kinetics should be used, and these methods result in longer estimates of photochemical lifetimes for plastics in surface waters. Scanning electron microscopy revealed that photoirradiation produced two distinct patterns of cracking on the particles. However, size distribution analyses indicated that fragmentation was minimal. Instead, the initial population of microplastics shrank in size during irradiations, indicating photoirradiation in tranquil waters (i.e., without mechanical forcing) dissolved sub-millimeter plastics without fragmentation.

New versus naturally aged greenhouse cover films: Degradation and micro-nanoplastics characterization under sunlight exposure

The understanding of microplastic degradation and its effects remains limited due to the absence of accurate analytical techniques for detecting and quantifying micro- and nanoplastics. In this study, we investigated the release of nanoplastics and small microplastics in water from low-density polyethylene (LDPE) greenhouse cover films under simulated sunlight exposure for six months. Our analysis included both new and naturally aged (used) cover films, enabling us to evaluate the impact of natural aging. Additionally, photooxidation effects were assessed by comparing irradiated and non-irradiated conditions. Scanning electron microscopy (SEM) and nanoparticle tracking analysis (NTA) confirmed the presence of particles below 1 μm in both irradiated and non-irradiated cover films. NTA revealed a clear effect of natural aging, with used films releasing more particles than new films but no impact of photooxidation, as irradiated and non-irradiated cover films released similar amounts of particles at each time point. Raman spectroscopy demonstrated the lower crystallinity of the released PE nanoplastics compared to the new films. Flow cytometry and total organic carbon data provided evidence of the release of additional material besides PE, and a clear effect of both simulated and natural aging, with photodegradation effects observed only for the new cover films. Finally, our results underscore the importance of studying the aging processes in both new and used plastic products using complementary techniques to assess the environmental fate and safety risks posed by plastics used in agriculture.

Mechanistic Insights into Cellular and Molecular Basis of Protein-Nanoplastic Interactions

Plastic waste is ubiquitously present across the world, and its nano/sub-micron analogues (plastic nanoparticles, PNPs), raise severe environmental concerns affecting organisms' health. Considering the direct and indirect toxic implications of PNPs, their biological impacts are actively being studied; lately, with special emphasis on cellular and molecular mechanistic intricacies. Combinatorial OMICS studies identified proteins as major regulators of PNP mediated cellular toxicity via activation of oxidative enzymes and generation of ROS. Alteration of protein function by PNPs results in DNA damage, organellar dysfunction, and autophagy, thus resulting in inflammation/cell death. The molecular mechanistic basis of these cellular toxic endeavors is fine-tuned at the level of structural alterations in proteins of physiological relevance. Detailed biophysical studies on such protein-PNP interactions evidenced prominent modifications in their structural architecture and conformational energy landscape. Another essential aspect of the protein-PNP interactions includes bioenzymatic plastic degradation perspective, as the interactive units of plastics are essentially nano-sized. Combining all these attributes of protein-PNP interactions, the current review comprehensively documented the contemporary understanding of the concerned interactions in the light of cellular, molecular, kinetic/thermodynamic details. Additionally, the applicatory, economical facet of these interactions, PNP biogeochemical cycle and enzymatic advances pertaining to plastic degradation has also been discussed.

Toxic effects of aging mask microplastics on E. coli and dynamic changes in extracellular polymeric matter

Contamination of disposable medical masks has become a growing problem globally in the wake of Covid-19 due to their widespread use and improper disposal. Three different mask layers, namely the outer layer, the meltblown (MB) filler layer and the inner layers release three different types of microplastics, whose physical and chemical properties change after prolonged environmental weathering. In this study, physical and chemical changes of mask microplastics before and after aging were characterized by different characterization techniques. The toxic effect and mechanism of aged mask microplastics on Escherichia coli (E. coli) were studied by measuring the growth inhibition of mask microplastics, the change in ATPase activity, the change in malondialdehyde content and reactive oxygen species production, and the release of the chemical composition of exopolymeric substances (EPS). The microplastics of the aged MB filter layer had the most significant inhibitory effect on E. coli growth, reaching 19.2 % after 36 h. Also, under the influence of mask microplastics, ATPase activity of E. coli was inhibited and a large amount of EPS was released. The chemical composition of EPS has also changed. This study proposed the possible toxicity mechanism of mask microplastics and the self-protection mechanism of E. coli, and provided a reference for future research on the toxic effects of mask microplastics on environmental organisms.

Analytical challenges in detecting microplastics and nanoplastics in soil-plant systems

Microplastics (MPx) and nanoplastics (NPx) are increasingly accumulating in terrestrial ecosystems, heightening concerns about their potential adverse effects on human health via the food chain. Techniques aimed at recovering the most challenging colloidal fractions of MPx and NPx, especially for analytical purposes, are limited. This systematic review emphasises the absence of a universal, efficient, and cost-effective analytical method as the primary hindrance to studying MPx and NPx in soil and plant samples. The study reveals that several methods, including density separation, organic matter removal, and filtration, are utilized to detect MPx or NPx in soil through vibrational spectroscopy and visual identification. Instruments such as Pyrolysis Gas Chromatography Mass Spectrometry (Py-GCMS), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) Spectroscopy, and fluorescence microscopy are employed to identify MPx and NPx in plant tissue. In extraction procedures, organic solvents and sonication are used to isolate NPx from plant tissues, while Pyrolysis GC-MS quantifies the plastics. SEM and TEM serve to observe and characterize NPx within plant tissues. Additionally, FTIR and fluorescence microscopy are utilized to identify polymers of MPx and NPx based on their spectral characteristics and fluorescence signals. The findings from this review clarify the identification and quantification methods for MPx and NPx in soil and plant systems and provide a comprehensive methodology for assessing MPx/NPx in the environment.

Aging rate, environmental risk and production efficiency of the low-density polyethylene (LDPE) films with contrasting thickness in irrigated region

Physical thickness of low-density polyethylene (LDPE) films might determine the release rate of phthalic acid esters (PAEs) & structural integrity and affect production efficiency. However, this critical issue is still unclear and little reported. Aging effects were evaluated in LDPE films with the thickness of 0.006, 0.008, 0.010 and 0.015 mm in a maize field of irrigation region. The Scanning electron microscope (SEM) results showed that the proportion of damaged area (Dam) to total area of LDPE films was massively lowered with increasing thickness after aging. The highest and lowest Dam was 32.2% and 3.5% in 0.006 and 0.015 mm films respectively. Also, the variations in peak intensity of asymmetric & symmetrical stretching vibrations (ASVI & SSVI) were detected using Fourier transform infrared spectrum (FTIR), indicating that the declines in peak intensity tended to be slower with thickness. Interestingly, the declines in physical integrity were tightly associated with increasing exhalation rate of PAEs. Average releasing rate of PAEs was 38.2%, 31.4%, 31.5% and 19.7% in LDPE films from 0.006 to 0.015 mm respectively. Critically, thicker film mulching can lead to greater soil water storage at plough layer (SWS-PL) and better thermal status, accordingly harvesting higher economic benefit. Therefore, LDPE film thickening may be a solution to reduce environmental risk but improve production efficiency in arid region.

Study on the impact of photoaging on the generation of very small microplastics (MPs) and nanoplastics (NPs) and the wettability of plastic surface

Photoaging is one of the important reasons for the sharp increase of waste plastics, especially microplastics (MPs), in the environment. Therefore, studying the photoaging of plastics is of great significance for controlling plastic pollution from the source. Nevertheless, there are few studies on plastic photoaging from the perspective of polymer structure. Besides, the capacity of different types of plastics to generate MPs with small particle size is relatively little studied. In view of this, we conducted a preliminary study on the capacity of different types of plastics to generate MPs using flow cytometry. We also studied the impact of photoaging on different types of plastics. The results showed that flow cytometry can be used to quantify very small MPs (1-50 μm) and nanoplastics (NPs) (< 1 μm). Furthermore, photoaging often accelerates the generation of MPs and roughens plastic surface. Besides, photoaging can introduce some oxygen-containing groups onto plastic surface, thereby changing the wettability of plastic surface. Moreover, benzene rings in polymer structures may inhibit the generation of MPs but may promote the transformation of the plastic surface from hydrophobic to hydrophilic during photoaging. Although the changes in properties of plastics caused by photoaging have adverse effects on the environment, some new processes and materials still can be developed based on photoaging of plastics. This work contributes to a better understanding of the photoaging of plastics from the perspective of polymer structure, which has certain positive significance for controlling plastic pollution from the source.

Microplastics in soils during the COVID-19 pandemic: Sources, migration and transformations, and remediation technologies

The COVID-19 pandemic has led to a notable upsurge of 5-10 % in global plastic production, which could have potential implications on the soil quality through increased microplastics (MPs) content. The elevated levels of MPs in the soil poses a significant threat to both the environment and human health, hence necessitating the remediation of MPs in the environment. Despite the significant attention given to MPs remediation in aqueous environments, less consideration has been given to MPs remediation in the soil. Consequently, this review highlights the major sources of MPs in the soil, their migration and transformation behaviors during the COVID-19 pandemic, and emphasizes the importance of utilizing remediation technologies such as phytoremediation, thermal treatment, microbial degradation, and photodegradation for MPs in the soil. Furthermore, this review provides a prospective outlook on potential future remediation methods for MPs in the soil. Although the COVID-19 pandemic is nearing its end, the long-term impact of MPs on the soil remains, making this review a valuable reference for the remediation of MPs in the post-pandemic soil.

Fragmentation of nano- and microplastics from virgin- and additive-containing polypropylene by accelerated photooxidation

Plastic is ubiquitous in the environment, where it gradually weathers and fragments into nanoplastics (NPs) and microplastics (MPs); however, the weathering process and fragmentation rate are poorly understood. In this study, we quantitatively determined the abundances and size distributions of NPs and MPs produced from virgin polypropylene (PP) and additive-containing PP (PPa) sheets via photooxidation with water in a simulated sunlight chamber followed by vortexing. The fragmentation rate of PP and PPa were approximately 1.1 × 108 particles/cm2 and 1.0 × 108 particles/cm2, respectively, during 176 days of exposure in the chamber (corresponding to 2.7 years of exposure in an outdoor environment in the Republic of Korea). However, quadratic regression analysis of the relationship between total particles produced and exposure duration revealed that the PP fragmentation rate was faster than the PPa fragmentation rate after a sunlight exposure duration equivalent to 2.7 years. Furthermore, the mechanical stress of vortexing after photooxidation played an important role in the production of MPs; it had a smaller role in the production of NPs. The sizes of fragmented particles produced by photooxidation and mechanical stress followed a power law distribution, with a scaling exponent of α = 2.87 ± 0.15, which was similar to a three-dimensional fragmentation pattern. This study provides valuable insights into the weathering and fragmentation processes of plastics. Further studies on the environmental fate and impact of NP and MP production from plastic weathering and fragmentation, as well as the potential influence of plastic additives on these processes.

Leaching of herbicides mixtures from pre-exposed agricultural plastics severely impact microalgae

Farmlands represent a source of aged plastics and pesticides to the surrounding environments. It has been shown that chemicals can be sorbed and desorbed from plastics, but the interaction between plastic and mixtures of pesticides and their effects on freshwater biota has not been assessed yet. The aim of the work was to assess the potential role of agricultural plastics as vectors for a mixture of two herbicides and the impact of the herbicide mixture lixiviated from them towards the freshwater microalga Chlamydomonas reinhardtii. Pristine and aged polyethylene plastics collected from agricultural areas were exposed to the herbicides, bifenox, oxyfluorfen and their mixtures. The microalgae were exposed for 72 h to the leachates desorbed from plastics and the effect was quantified in terms of total chlorophyll content and several physiological parameters assessed by flow cytometry. Our results showed that changes in physicochemical properties (hydroxyl and carbonyl index, hydrophobicity, texture) in aged plastics increased their capacity to retain and to desorb the herbicides. Microalgae exposed to leachates containing bifenox, oxyfluorfen, or their mixture showed reactive oxygen species overproduction, lipid peroxidation, membrane potential hyperpolarization, intracellular pH acidification, and a loss of metabolic activity. The toxicological interactions of the leachate mixture were assessed using the Combination Index (CI)-isobologram method showing antagonism at low effect levels turning to synergism when the effect increased. In this work, we proved the hypothesis that ageing increases the capacity of agricultural plastics to behave as vector for toxic chemicals to the biota.

Exploring sorption of pesticides and PAHs in microplastics derived from plastic mulch films used in modern agriculture

The sorption and vector effect of microplastics on the transfer of pesticides and polycyclic aromatic hydrocarbons (PAHs), as well as its impact on agriculture remain largely unexplored. This comparative study is first to investigate the sorption behavior of different pesticides and PAHs at environmentally realistic concentrations by model microplastics and microplastics derived from polyethylene mulch films. Sorption was found to be up to 90% higher in the case of microplastics derived from mulch films as opposed to pure polyethylene microspheres. For microplastics from mulch films, the sorption percentages for pesticides in media containing CaCl₂ were reported to be: pyridate (75.68% and 52.44%), fenazaquin (48.54% and 32.02%), pyridaben (45.04% and 56.70%), bifenthrin (74.27% and 25.88%), etofenprox (82.16% and 54.16%) and pyridalyl (97.00% and 29.74%) at 5 μg/L and 200 μg/L pesticide concentration levels respectively. For PAHs, the sorption amounts were: naphthalene (22.03% and 48.00%), fluorene (38.99% and 39.00%), anthracene (64.62% and 68.02%) and pyrene (75.65% and 86.38%) at 5 μg/L and 200 μg/L PAH concentration levels respectively. Sorption was influenced by the octanol-water partition coefficient (log K_ow) and ionic strength. Kinetics of the process in the case of sorption of pesticides were best explained by pseudo-first order kinetic model (R² between 0.90 and 0.98) while the best fitting isotherm model was Dubinin-Radushkevich (R² between 0.92 and 0.99). Results suggest the presence of surface level physi-sorption through a micropore volume filling mechanism and the role of hydrophobic and electrostatic forces. Pesticide desorption data in polyethylene mulch films indicate that pesticides with high log K_ow were almost completely retained in mulch films, while those with lower log K_ow were desorbed rapidly into the surrounding media. Our study highlights the role of microplastics from plastic mulch films as vectors for pesticide and PAH transport at environmentally realistic concentrations and the factors that influence it.

Occurrence and ecological risks of microplastics and phthalate esters in organic solid wastes: In a landfill located nearby the Persian Gulf

Landfill sites are the main source of plastic waste. Thus, municipal solid waste (MSW) in landfills may act as a reservior of microplastics (MPs) and related pollutants such as phthalate esters (PAEs) into surrounding environment. However, there is limited information on MPs and PAEs in landfill sites. Levels of MPs and PAEs in organic solid waste disposed in a landfill of Bushehr port were investigated for the first time in this study. The mean MPs and PAEs levels in organic MSW samples were 12.3 items/g and 7.99 μg/g, respectively, and the mean PAEs concentration in MPs was 87.5 μg/g. The highest number of MPs was related to the size classes of >1000 μm and <25 μm. The highest dominant type, color, and shape of MPs in organic MSW were nylon, white/transparent, and fragments, respectively. Di (2-ethylhexyl) phthalate (DEHP) and diisobutyl phthalate (DiBP) were the dominant compounds of PAEs in organic MSW. Based on the finding of present study, MPs showed a high hazard index (HI). DEHP, dioctyl phthalate (DOP), and DiBP demonstrated high-level hazards for sensitive organisms in water. This work illustrated considerable MPs and PAEs levels from an uncontrolled landfill without adequate protection, possibly contributing to their release into the environment. The sites of landfill located near marine environments, such as Bushehr port landfill adjacent to the Persian Gulf, may indicate critical threats to marine organisms and the food chain. Continuous landfills control and monitoring, especially the ones near the coastal area, is highly recommended to prevent further environmental pollution.

Oligomer nanoparticle release from polylactic acid plastics catalysed by gut enzymes triggers acute inflammation

The health risks of exposure to 'eco-friendly' biodegradable plastics of anthropogenic origin and their effects on the gastrointestinal tract are largely unknown. Here we demonstrate that the enzymatic hydrolysis of polylactic acid microplastics generated nanoplastic particles by competing for triglyceride-degrading lipase during gastrointestinal processes. Nanoparticle oligomers were formed by hydrophobically driven self-aggregation. In a mouse model, polylactic acid oligomers and their nanoparticles bioaccumulated in the liver, intestine and brain. Hydrolysed oligomers caused intestinal damage and acute inflammation. A large-scale pharmacophore model revealed that oligomers interacted with matrix metallopeptidase 12. Mechanistically, high binding affinity (K_d = 13.3 μmol l^-1) of oligomers to the catalytic zinc-ion finger domain led to matrix metallopeptidase 12 inactivation, which might mediate the adverse bowel inflammatory effects after exposure to polylactic acid oligomers. Biodegradable plastics are considered to be a solution to address environmental plastic pollution. Thus, understanding the gastrointestinal fates and toxicities of bioplastics will provide insights into potential health risks.

The Minderoo-Monaco Commission on Plastics and Human Health

Background

Plastics have conveyed great benefits to humanity and made possible some of the most significant advances of modern civilization in fields as diverse as medicine, electronics, aerospace, construction, food packaging, and sports. It is now clear, however, that plastics are also responsible for significant harms to human health, the economy, and the earth's environment. These harms occur at every stage of the plastic life cycle, from extraction of the coal, oil, and gas that are its main feedstocks through to ultimate disposal into the environment. The extent of these harms not been systematically assessed, their magnitude not fully quantified, and their economic costs not comprehensively counted.

Goals

The goals of this Minderoo-Monaco Commission on Plastics and Human Health are to comprehensively examine plastics' impacts across their life cycle on: (1) human health and well-being; (2) the global environment, especially the ocean; (3) the economy; and (4) vulnerable populations-the poor, minorities, and the world's children. On the basis of this examination, the Commission offers science-based recommendations designed to support development of a Global Plastics Treaty, protect human health, and save lives.

Report Structure

This Commission report contains seven Sections. Following an Introduction, Section 2 presents a narrative review of the processes involved in plastic production, use, and disposal and notes the hazards to human health and the environment associated with each of these stages. Section 3 describes plastics' impacts on the ocean and notes the potential for plastic in the ocean to enter the marine food web and result in human exposure. Section 4 details plastics' impacts on human health. Section 5 presents a first-order estimate of plastics' health-related economic costs. Section 6 examines the intersection between plastic, social inequity, and environmental injustice. Section 7 presents the Commission's findings and recommendations.

Plastics

Plastics are complex, highly heterogeneous, synthetic chemical materials. Over 98% of plastics are produced from fossil carbon- coal, oil and gas. Plastics are comprised of a carbon-based polymer backbone and thousands of additional chemicals that are incorporated into polymers to convey specific properties such as color, flexibility, stability, water repellence, flame retardation, and ultraviolet resistance. Many of these added chemicals are highly toxic. They include carcinogens, neurotoxicants and endocrine disruptors such as phthalates, bisphenols, per- and poly-fluoroalkyl substances (PFAS), brominated flame retardants, and organophosphate flame retardants. They are integral components of plastic and are responsible for many of plastics' harms to human health and the environment.Global plastic production has increased almost exponentially since World War II, and in this time more than 8,300 megatons (Mt) of plastic have been manufactured. Annual production volume has grown from under 2 Mt in 1950 to 460 Mt in 2019, a 230-fold increase, and is on track to triple by 2060. More than half of all plastic ever made has been produced since 2002. Single-use plastics account for 35-40% of current plastic production and represent the most rapidly growing segment of plastic manufacture.Explosive recent growth in plastics production reflects a deliberate pivot by the integrated multinational fossil-carbon corporations that produce coal, oil and gas and that also manufacture plastics. These corporations are reducing their production of fossil fuels and increasing plastics manufacture. The two principal factors responsible for this pivot are decreasing global demand for carbon-based fuels due to increases in 'green' energy, and massive expansion of oil and gas production due to fracking.Plastic manufacture is energy-intensive and contributes significantly to climate change. At present, plastic production is responsible for an estimated 3.7% of global greenhouse gas emissions, more than the contribution of Brazil. This fraction is projected to increase to 4.5% by 2060 if current trends continue unchecked.

Plastic Life Cycle

The plastic life cycle has three phases: production, use, and disposal. In production, carbon feedstocks-coal, gas, and oil-are transformed through energy-intensive, catalytic processes into a vast array of products. Plastic use occurs in every aspect of modern life and results in widespread human exposure to the chemicals contained in plastic. Single-use plastics constitute the largest portion of current use, followed by synthetic fibers and construction.Plastic disposal is highly inefficient, with recovery and recycling rates below 10% globally. The result is that an estimated 22 Mt of plastic waste enters the environment each year, much of it single-use plastic and are added to the more than 6 gigatons of plastic waste that have accumulated since 1950. Strategies for disposal of plastic waste include controlled and uncontrolled landfilling, open burning, thermal conversion, and export. Vast quantities of plastic waste are exported each year from high-income to low-income countries, where it accumulates in landfills, pollutes air and water, degrades vital ecosystems, befouls beaches and estuaries, and harms human health-environmental injustice on a global scale. Plastic-laden e-waste is particularly problematic.

Environmental Findings

Plastics and plastic-associated chemicals are responsible for widespread pollution. They contaminate aquatic (marine and freshwater), terrestrial, and atmospheric environments globally. The ocean is the ultimate destination for much plastic, and plastics are found throughout the ocean, including coastal regions, the sea surface, the deep sea, and polar sea ice. Many plastics appear to resist breakdown in the ocean and could persist in the global environment for decades. Macro- and micro-plastic particles have been identified in hundreds of marine species in all major taxa, including species consumed by humans. Trophic transfer of microplastic particles and the chemicals within them has been demonstrated. Although microplastic particles themselves (>10 µm) appear not to undergo biomagnification, hydrophobic plastic-associated chemicals bioaccumulate in marine animals and biomagnify in marine food webs. The amounts and fates of smaller microplastic and nanoplastic particles (MNPs <10 µm) in aquatic environments are poorly understood, but the potential for harm is worrying given their mobility in biological systems. Adverse environmental impacts of plastic pollution occur at multiple levels from molecular and biochemical to population and ecosystem. MNP contamination of seafood results in direct, though not well quantified, human exposure to plastics and plastic-associated chemicals. Marine plastic pollution endangers the ocean ecosystems upon which all humanity depends for food, oxygen, livelihood, and well-being.

Human Health Findings

Coal miners, oil workers and gas field workers who extract fossil carbon feedstocks for plastic production suffer increased mortality from traumatic injury, coal workers' pneumoconiosis, silicosis, cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer. Plastic production workers are at increased risk of leukemia, lymphoma, hepatic angiosarcoma, brain cancer, breast cancer, mesothelioma, neurotoxic injury, and decreased fertility. Workers producing plastic textiles die of bladder cancer, lung cancer, mesothelioma, and interstitial lung disease at increased rates. Plastic recycling workers have increased rates of cardiovascular disease, toxic metal poisoning, neuropathy, and lung cancer. Residents of "fenceline" communities adjacent to plastic production and waste disposal sites experience increased risks of premature birth, low birth weight, asthma, childhood leukemia, cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer.During use and also in disposal, plastics release toxic chemicals including additives and residual monomers into the environment and into people. National biomonitoring surveys in the USA document population-wide exposures to these chemicals. Plastic additives disrupt endocrine function and increase risk for premature births, neurodevelopmental disorders, male reproductive birth defects, infertility, obesity, cardiovascular disease, renal disease, and cancers. Chemical-laden MNPs formed through the environmental degradation of plastic waste can enter living organisms, including humans. Emerging, albeit still incomplete evidence indicates that MNPs may cause toxicity due to their physical and toxicological effects as well as by acting as vectors that transport toxic chemicals and bacterial pathogens into tissues and cells.Infants in the womb and young children are two populations at particularly high risk of plastic-related health effects. Because of the exquisite sensitivity of early development to hazardous chemicals and children's unique patterns of exposure, plastic-associated exposures are linked to increased risks of prematurity, stillbirth, low birth weight, birth defects of the reproductive organs, neurodevelopmental impairment, impaired lung growth, and childhood cancer. Early-life exposures to plastic-associated chemicals also increase the risk of multiple non-communicable diseases later in life.

Economic Findings

Plastic's harms to human health result in significant economic costs. We estimate that in 2015 the health-related costs of plastic production exceeded $250 billion (2015 Int$) globally, and that in the USA alone the health costs of disease and disability caused by the plastic-associated chemicals PBDE, BPA and DEHP exceeded $920 billion (2015 Int$). Plastic production results in greenhouse gas (GHG) emissions equivalent to 1.96 gigatons of carbon dioxide (CO2e) annually. Using the US Environmental Protection Agency's (EPA) social cost of carbon metric, we estimate the annual costs of these GHG emissions to be $341 billion (2015 Int$).These costs, large as they are, almost certainly underestimate the full economic losses resulting from plastics' negative impacts on human health and the global environment. All of plastics' economic costs-and also its social costs-are externalized by the petrochemical and plastic manufacturing industry and are borne by citizens, taxpayers, and governments in countries around the world without compensation.

Social Justice Findings

The adverse effects of plastics and plastic pollution on human health, the economy and the environment are not evenly distributed. They disproportionately affect poor, disempowered, and marginalized populations such as workers, racial and ethnic minorities, "fenceline" communities, Indigenous groups, women, and children, all of whom had little to do with creating the current plastics crisis and lack the political influence or the resources to address it. Plastics' harmful impacts across its life cycle are most keenly felt in the Global South, in small island states, and in disenfranchised areas in the Global North. Social and environmental justice (SEJ) principles require reversal of these inequitable burdens to ensure that no group bears a disproportionate share of plastics' negative impacts and that those who benefit economically from plastic bear their fair share of its currently externalized costs.

Conclusions

It is now clear that current patterns of plastic production, use, and disposal are not sustainable and are responsible for significant harms to human health, the environment, and the economy as well as for deep societal injustices.The main driver of these worsening harms is an almost exponential and still accelerating increase in global plastic production. Plastics' harms are further magnified by low rates of recovery and recycling and by the long persistence of plastic waste in the environment.The thousands of chemicals in plastics-monomers, additives, processing agents, and non-intentionally added substances-include amongst their number known human carcinogens, endocrine disruptors, neurotoxicants, and persistent organic pollutants. These chemicals are responsible for many of plastics' known harms to human and planetary health. The chemicals leach out of plastics, enter the environment, cause pollution, and result in human exposure and disease. All efforts to reduce plastics' hazards must address the hazards of plastic-associated chemicals.

Recommendations

To protect human and planetary health, especially the health of vulnerable and at-risk populations, and put the world on track to end plastic pollution by 2040, this Commission supports urgent adoption by the world's nations of a strong and comprehensive Global Plastics Treaty in accord with the mandate set forth in the March 2022 resolution of the United Nations Environment Assembly (UNEA).International measures such as a Global Plastics Treaty are needed to curb plastic production and pollution, because the harms to human health and the environment caused by plastics, plastic-associated chemicals and plastic waste transcend national boundaries, are planetary in their scale, and have disproportionate impacts on the health and well-being of people in the world's poorest nations. Effective implementation of the Global Plastics Treaty will require that international action be coordinated and complemented by interventions at the national, regional, and local levels.This Commission urges that a cap on global plastic production with targets, timetables, and national contributions be a central provision of the Global Plastics Treaty. We recommend inclusion of the following additional provisions:The Treaty needs to extend beyond microplastics and marine litter to include all of the many thousands of chemicals incorporated into plastics.The Treaty needs to include a provision banning or severely restricting manufacture and use of unnecessary, avoidable, and problematic plastic items, especially single-use items such as manufactured plastic microbeads.The Treaty needs to include requirements on extended producer responsibility (EPR) that make fossil carbon producers, plastic producers, and the manufacturers of plastic products legally and financially responsible for the safety and end-of-life management of all the materials they produce and sell.The Treaty needs to mandate reductions in the chemical complexity of plastic products; health-protective standards for plastics and plastic additives; a requirement for use of sustainable non-toxic materials; full disclosure of all components; and traceability of components. International cooperation will be essential to implementing and enforcing these standards.The Treaty needs to include SEJ remedies at each stage of the plastic life cycle designed to fill gaps in community knowledge and advance both distributional and procedural equity.This Commission encourages inclusion in the Global Plastic Treaty of a provision calling for exploration of listing at least some plastic polymers as persistent organic pollutants (POPs) under the Stockholm Convention.This Commission encourages a strong interface between the Global Plastics Treaty and the Basel and London Conventions to enhance management of hazardous plastic waste and slow current massive exports of plastic waste into the world's least-developed countries.This Commission recommends the creation of a Permanent Science Policy Advisory Body to guide the Treaty's implementation. The main priorities of this Body would be to guide Member States and other stakeholders in evaluating which solutions are most effective in reducing plastic consumption, enhancing plastic waste recovery and recycling, and curbing the generation of plastic waste. This Body could also assess trade-offs among these solutions and evaluate safer alternatives to current plastics. It could monitor the transnational export of plastic waste. It could coordinate robust oceanic-, land-, and air-based MNP monitoring programs.This Commission recommends urgent investment by national governments in research into solutions to the global plastic crisis. This research will need to determine which solutions are most effective and cost-effective in the context of particular countries and assess the risks and benefits of proposed solutions. Oceanographic and environmental research is needed to better measure concentrations and impacts of plastics <10 µm and understand their distribution and fate in the global environment. Biomedical research is needed to elucidate the human health impacts of plastics, especially MNPs.

Summary

This Commission finds that plastics are both a boon to humanity and a stealth threat to human and planetary health. Plastics convey enormous benefits, but current linear patterns of plastic production, use, and disposal that pay little attention to sustainable design or safe materials and a near absence of recovery, reuse, and recycling are responsible for grave harms to health, widespread environmental damage, great economic costs, and deep societal injustices. These harms are rapidly worsening.While there remain gaps in knowledge about plastics' harms and uncertainties about their full magnitude, the evidence available today demonstrates unequivocally that these impacts are great and that they will increase in severity in the absence of urgent and effective intervention at global scale. Manufacture and use of essential plastics may continue. However, reckless increases in plastic production, and especially increases in the manufacture of an ever-increasing array of unnecessary single-use plastic products, need to be curbed.Global intervention against the plastic crisis is needed now because the costs of failure to act will be immense.

Fourier Transform Infrared Spectroscopy to Assess the Degree of Alteration of Artificially Aged and Environmentally Weathered Microplastics

Fourier transform infrared (FTIR) is a spectroscopy technique widely used to identify organic materials. It has recently gained popularity in microplastic (MP) pollution research to determine the chemical composition of unknown plastic fragments. However, it could also be used to evaluate the degree of ageing of MPs collected from the environment. In this context, the principal aim of our research has been to qualitatively evaluate the natural weathering of environmental MPs collected in an Italian freshwater body (the Ofanto River) using ATR-FTIR technology. Furthermore, we compared environmental particles to weathered artificial MPs under controlled light and temperature conditions and to unaltered pristine materials to assess the results. FTIR spectra were acquired using a Nicolet Summit FTIR (ThermoFisher Scientific) equipped with an Everest ATR with a diamond Crystal plate and a DTGS KBr detector (wavenumber range 4000-500 cm^-1, 32 scans per spectrum, spectral resolution of 4 cm^-1). The degree of ageing was assessed using three different indexes known to be related to changes in MPs: Carbonyl Index (CI), Hydroxyl Index (HI), and Carbon-Oxygen Index (COI). The overall results showed that the regions reflecting changes (hydroxyl groups, peaks from 3100 to 3700 cm^-1, alkenes or carbon double bonds, 1600 and 1680 cm^-1, and carbonyl groups, 1690 and 1810 cm^-1) appeared significantly modified in artificial and natural weathered particles compared to the pristine materials. The indexes calculated for polymers degraded under the artificial photo and thermo ageing conditions displayed a general tendency to increase with the time in contact with irradiation time. Particular enhancements of CI of PS fragment and PE pellet, HI of PE and PS fragments and PE pellet, and COI of PS fragment were observed. Otherwise, the following incubation of the same particles at a constant temperature of 45 °C did not further affect the chemical composition of the particles. Moreover, new unique peaks were also observed in the freshwater particles, almost all in the fingerprint region (1500-500 cm^-1). Differences in CI, HI, and COI were evidenced among the different morphological MP shapes. On the one hand, the CI calculated for the environmental PE pellets showed values ranging from 0.05 to 0.26 with a mean value of 0.17 ± 0.10. Most samples (57%) presented a CI with values between 0.16 and 0.30. On the other hand, fragments presented slicer modifications in the carbonyl region with CI values lower than pellets (0.05 ± 0.05). This index helps evaluate the degradation of PE MPs by UV light, increasing with enhancing residence time in the environment. Conversely, fragments showed greater values of HI (5.90 ± 2.57) and COI (1.04 ± 0.48) than pellets, as well as lines, which presented the maximum value of HI (11.51). HI is attributed to the bond vibrations of hydroxyl, carboxyl, or phenol groups. In contrast, COI is frequently attributed to the vibrations of C_O bonds found in carbohydrates, alkanes, secondary alcohols, and ketones. In conclusion, our results showed characteristics spectra acquired from environmental particles compared to pristine and artificial aged ones. The interpretation of our main results emphasizes the need to conduct ecotoxicological experimental studies using naturally weathered particles due to the unicity of their properties, which are more helpful for understanding microplastic pollution effects.

In situ degradation of low-density polyethylene film in irrigation maize field: Thickness-dependent effect

Thickness of low-density polyethylene (LDPE) film might determine its mechanical strength, clean production and soil health. Yet, this issue is little understood. In situ aging effects were evaluated in LDPE films with the thickness of 0.006 mm, 0.008 mm, 0.010 mm and 0.015 mm in maize field. The data showed that maximum tensile force (TFmax), maximum tensile strength (TSmax) and elongation at break (EAB) were massively lowered with increasing thickness after aging. The greatest and lowest reduction magnitude of EAB was 27.6 % and 11.2 % in 0.006 mm and 0.015 mm films respectively. Also, the melting point (Tm) and crystallinity (Xc) under Differential Scanning Calorimeter (DSC) tended to decline with the increasing thickness. Moreover, the peak intensity of crystalline regions tended to transfer and concentrate on the amorphous regions, and such tendency became more pronounced in the thin films. Interestingly, there existed a pronounced distinct thickness-dependent effects on soil bulk density (SBD) and soil water-stable aggregate proportion. Thick plastic film mulching increased SBD but reduced the proportion of macroaggregates (mainly referred to 0.015 mm and 0.010 mm). In addition, thick film mulching slightly reduced the levels of soil organic carbon (SOC) and total nitrogen (TN), but significantly promoted the contents of soil labile C and N. Particularly, it significantly promoted above- & under-ground biomass of maize across two growing seasons (p < 0.05). To sum up, thickening LDPE film may act as a promising solution to improve LDPE film residue recycling, while benefiting for higher productivity. However, thick film mulching may cause a certain adverse impact on soil structure, and further investigations would be needed in the future.

Analytical methods for microplastics in the environment: a review

Microplastic pollution is a recently discovered threat to ecosystems requiring the development of new analytical methods. Here, we review classical and advanced methods for microplastic analysis. Methods include visual analysis, laser diffraction particle, dynamic light scattering, scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, thermal analysis, mass spectrometry, aptamer and in vitro selection, and flow cytometry.

The photochemical behaviors of microplastics through the lens of reactive oxygen species: Photolysis mechanisms and enhancing photo-transformation of pollutants

The photoaging mechanisms of various polymers have been explored based on the basic autoxidation scheme (BAS) before 10 years ago, however current research verified some defects in the BAS in both thermodynamic and dynamics. These defects are troublesome because they are associated with the hydrogen abstraction which is central to continuously perform the photooxidation process of microplastics. These found indicated that we might wrongly inferred photo-oxidation process of some microplastics. In addition, the important role of reactive oxygen species (ROS) in the type-dependent photoaging process of various microplastics has been revealed recently. In this case, fully and accurately understanding the photoaging mechanisms of different microplastics in environment is a priority to further manage the ecological risk of microplastics. Herein, this review aims to revise and update the degradation process of microplastics based on the revised BAS and in the perspective of ROS. Specifically, the modification of BAS is firstly discussed. The photoaging mechanisms of representative microplastics (i.e., polyethylene, polystyrene and polyethylene terephthalate) are then updated based on the corrected BAS. Additionally, the role of ROS in their photolysis process and the possibility of microplastics as photosensitizers/mediators to regulate the fate of co-existent pollutants are also analyzed. Finally, several perspectives are then proposed to guide future research on the photoaging behaviors of microplastics. This review would pave the way for the understanding of microplastic photoaging and the management of plastic pollution in environments.

The fragmentation of nano- and microplastic particles from thermoplastics accelerated by simulated-sunlight-mediated photooxidation

The plastic debris that washes ashore and litters the shoreline often undergoes weathering under sunlight exposure, such that it fragments to form nanoplastics and microplastics, but the fragmentation rate for many thermoplastics is unknown. In this study, three major thermoplastics were exposed to simulated sunlight in an accelerated weathering chamber to evaluate the speed of photooxidation-induced fragmentation. The initiation of photooxidation-induced fragmentation extrapolated from the accelerated weathering chamber to real sunlight exposure in South Korea followed the order of PS (< 1 year) > PP (< 2 years) > LDPE (> 3 years). The surface cracks created by photooxidation were not directly reflected in the initiation of fragmentation of thermoplastics. The initiation of fragmentation was faster in PS than other polymers, but the total abundance of particles produced, and increasing ratio (exposure/non-exposure) were comparable or lower than those of PP. The increasing ratio pattern between nanoplastics and small microplastics of PP differed noticeably from other polymers. The initiation of nanoplastic and small-microplastic fragmentation determined in this study will be useful for the further estimation of secondary microplastic production by weathering and thus for decision-making regarding methods for the timely removal of plastic litter in the environment.

Occurrence, seasonal distribution, and ecological risk assessment of microplastics and phthalate esters in leachates of a landfill site located near the marine environment: Bushehr port, Iran as a case

Plastic wastes are produced in a large amount everywhere, and are commonly disposed in landfills. So landfill leachate seems an obvious source of microplastics (MPs) and phthalate esters (PAEs) due to a huge usage as plastic additives and plasticizers. But this issue still lacks attention and the present study provides the first information on the levels of MPs and PAEs in the fresh landfill leachate of Bushehr port during different seasons. The mean levels of MPs and PAEs in the fresh leachate in all seasons were 79.16 items/L and 3.27 mg/L, respectively. Also, the mean levels of PAEs in MPs were 48.33 μg/g. A statistically significant difference was detected in the levels of MPs and PAEs among different seasons with the highest values in summer and fall. MPs with a size of >1000 μm had the highest abundance in all seasons. The most prominent shape, color, and type of MPs in the leachate were fibers black, and nylon, respectively. Dibutyl phthalate (DBP) and Di(2-ethylhexyl) phthalate (DEHP) were the most dominant PAEs present in the leachate samples. The results of this study revealed high hazard index (HI) and pollution load index (PLI) of MPs in all seasons. Dioctyl phthalate (DOP), DEHP, DBP, diisobutyl phthalate (DiBP), butyl benzyl phthalate (BBP), and diethyl phthalate (DEP) represented a high risk to the sensitive organisms. The results of this study showed that significant levels of MPs and PAEs may release into the surrounding environment from the landfill sites without sufficient protection. This issue is more critical when the landfill sites in particular are located near the marine environments like the Bushehr landfill that is located near the Persian Gulf, which can lead to serious environmental problems. Thus permanent control and monitor of landfills, especially in the coastal areas are highly needed to prevent further pollution.

Ageing and fragmentation of marine microplastics

The generation of small fragments from the environmental ageing of microplastics (MPs) is still a poorly known process. This work addresses the fragmentation of MPs obtained from marine debris consisting of polyethylene and polypropylene (PE and PP in environmental mixture) and polystyrene (PS) after exposure to accelerated ageing by irradiation and mechanical stirring. Number particle size distribution in the 1-100 μm range was assessed by combining laser diffractometry with particle counts from flow cytometry. The results showed the generation of a high number of small MP particles, which reached 10⁵-10⁶ items/mg of plastic with most fragments <2 μm. The results showed that environmentally aged MPs give rise to a larger number of small MPs in a pattern consistent with progressive fragmentation in the three spatial dimensions. The proportion of small MPs was much higher than that found in current sampling campaigns, suggesting a severe underestimation of the environmental presence of small MPs. We also demonstrated the generation of nanoplastics (NPs) in the fraction <1 μm from irradiated runs. The results showed that the mechanism that produced nanoplastics (NPs) from MPs was irradiation, which yielded up to 10¹¹-10¹³ NPs/g with particle size in the few hundreds of nm range. Our results are relevant for the assessment of fate and risk of plastic debris in the environment showing that the number of small plastic fragments produced during the ageing of MPs is much larger than expect from the extrapolation of larger size populations.

Polystyrene nanoplastics and wastewater displayed antagonistic toxic effects due to the sorption of wastewater micropollutants

The knowledge about the interaction of nanoplastics with other aquatic pollutants and their combined effects on biota is very scarce. In this work, we studied the interaction between polystyrene nanoplastics (PS NPs) (30 nm) and the micropollutants in a biologically treated wastewater effluent (WW). The capacity of PS NPs to sorb micropollutants was studied as well as their single and combined toxicity towards three freshwater organisms: the recombinant bioluminescent cyanobacterium, Anabaena sp. PCC 7120 CPB4337; the duckweed, Spirodela polyrhiza and the cladoceran, Daphnia magna. The endpoints were the inhibition of bioluminescence, the growth inhibition of the aquatic plant and the immobilization of D. magna after 24, 72 and 48 h of exposure, respectively. Combination Index (CI)-isobologram method was used to quantify mixture toxicity and the nature of interactions. PS NPs sorbed a variety of chemicals present in WW as micropollutants in a range of tens of ng/L to μg/L. It was found that those pollutants with positive charge were the main ones retained onto PS NPs, which was attributed to the electrostatic interaction with the negatively charged PS NPs. Regarding the toxicological effects, single exposure to PS NPs affected the three tested organisms. However, single exposure to WW only had a negative impact on the cyanobacterium and S. polyrhiza with no observed toxicity to D. magna. Regarding PS NPs-WW combined exposure, a reduction of toxicity in comparison with single exposure was observed probably due to the sorption of micropollutants onto PS NPs, which resulted in lower bioavailability of the micropollutants. In addition, the formation of PS NPs-WW heteroaggregates was observed which could result in lower bioavailability of PS NPs and sorbed micropollutants, thus lowering toxicity. This study represents a near-realistic scenario approach to the potential sorption of wastewater pollutants onto nanoplastics that could alter the toxicological effect on the biota.

Microplastics identification and quantification in the composted Organic Fraction of Municipal Solid Waste

Composted Organic Fraction of Municipal Solid Waste (OFMSW) is used in agricultural soils as a source of organic matter and nutrients. Besides, its use avoids landfilling or incineration following the principles of circular economy. It is well established that source separated OFMSW is suitable for compost production, but its quality depends on their content in non-compostable materials. In this work, we selected and studied the final refined compost form five OFMSW facilities over a five-month period. The plants displayed differences in collection systems, concentration on non-desired materials, treatment technology and density of served population. The presence of plastic was studied using a separation and identification process that consisted of oxidation and flotation followed by spectroscopic identification. The results showed a concentration of plastic impurities in the 10-30 items/g of dry compost range. The concentration of small fragments and fibres (equivalent diameter < 5 mm) was in the 5-20 items/g of dry weight range and were dominated by fibres (25% of all particles <500 μm). Five polymers represented 94% of the plastic items: polyethylene, polystyrene, polyester, polypropylene, polyvinyl chloride, and acrylic polymers in order of abundance. Polyethylene was more abundant in films, polystyrene in fragments, polypropylene in filaments, and fibres were dominated by polyester. Our results showed that smaller plants, with OFMSW door-to-door collection systems produced compost with less plastic of all sizes. Compost from big facilities fed by OFMSW from street bin collection displayed the highest contents of plastics. No debris from compostable bioplastics were found in any of the samples, meaning that if correctly composted their current use does not contribute to the spreading of anthropogenic pollution. Our results suggested that the use of compostable polymers and the implementation of door-to-door collection systems could reduce the concentration of plastic impurities in compost from OFMSW.