Reporting Guidelines to Increase the Reproducibility and Comparability of Research on Microplastics

Micro- and nano-plastics, intestinal inflammation, and inflammatory bowel disease: A review of the literature

Plastics, encompassing a wide range of polymeric materials, and their downstream products (micro- and nanoplastics, MNPs) are accumulating in the environment at an alarming rate, and they are linked to adverse human health outcomes. Considering that ingestion is a main source of MNPs exposure, the impact of plastics is particularly relevant towards intestinal inflammation and inflammatory bowel disease (IBD). However, the study of MNPs has been limited by obstacles relating to sample collection, preparation, and microplastics analysis based on optical microscopy and chemical analysis, which we detail in this review alongside potential solutions. We summarize available data on human exposure to MNPs and overall health outcomes, with particular focus on data pertaining to intestinal inflammation, microbiome perturbations, and related outcomes. We include ecologic perspectives, and human, in vitro, and animal model studies. We discuss the way forward in MNPs and IBD research, including knowledge gaps and future research.

Assessment of microplastic pollution and polymer risk in the sediment compartment of the Limfjord, Denmark

Estuarine sediments intercept and temporarily retain microplastics before they reach the marine seafloor, impacting various organisms, including key commercial species. This highlights the critical need for research on microplastic exposure in these transitional environments. This study provides a detailed assessment of microplastic pollution in the sediment compartment of the Limfjord, a 1500 km2 large Danish fjord, and introduces the Polymer Hazard Index (PHI) as a tool for evaluating polymer-specific risks. Thirteen sediment samples were collected, covering an anthropogenic gradient along the fjord. State-of-the-art methods were applied for extracting and identifying (FPA-μFT-IR imaging) microplastics (10-5000 μm). Our results indicate that microplastic contamination is pervasive across all sampled locations with concentrations ranging from 273 to 4288 particles kg-1, with a predominance of small microplastics (<100 μm). The estimated mass-based concentrations ranged between 2.60 × 104-1.11 × 106 ng kg-1. Overall, we estimated a microplastic stock of 3.8 × 103-1.65 × 105 kg in the surface sediments of the Limfjord, i.e., some 2.5-110 kg km-2. The application of the PHI revealed significant risks associated with specific polymers, such as polyacrylonitrile (PAN) and acrylonitrile butadiene styrene (ABS), underscoring the importance of considering polymer-specific hazards in environmental assessments.

Examining ingested microplastics in fish: Considerations on filter pore size, analysis time, and material costs to design cost-effective projects

In recent years the microplastics research community has called for methods harmonization and standardized metrics of reporting microplastic attributes. While alignment of research practices is essential in obtaining robust microplastic data, resource managers need to balance how the cost and effort of methodologies compare to data output. The intention of this study is to compare two recommended methods for isolating anthropogenic microparticles in fish gastrointestinal tracts. Using Icelandic capelin (Mallotus villosus) as a study species, with potassium hydroxide (KOH) digestion, we compared a 1.2 μm filtration and 45 μm sieving protocols for isolating ingested anthropogenic microparticles. We compared methods based on the amount of time they took to conduct, the cost of the materials and equipment required, levels of procedural contamination, and data output. We found no significant differences in the materials costs or procedural contamination between the two methods. However, the two protocols resulted in anthropogenic microparticles with significantly different characteristics (i.e. colour, length, morphology), and the 45 μm sieving protocol took longer to conduct per sample. Our results contribute towards a more holistic understanding of microplastic research methods, their relative costs, and how they contribute to data outputs and development of large-scale monitoring programs.

Microplastic ingestion in five demersal, bathydemersal and bathypelagic fish species from the eastern Weddell Sea, Antarctica

Antarctica has traditionally been viewed as a relatively isolated ecosystem. Although still considered pristine, it is increasingly also being affected by microplastic pollution. Reported high sea floor concentrations raise concern that these ecosystems might act as major sink for microplastic pollution. This is significant as species in those remote ecosystems are likely more sensitive to rapid environmental change due to a high level of specialization, and lower tolerance levels. Microplastic ingestion in fish has barely been assessed in high latitude environments. Here we aimed to provide baseline data for the eastern Weddell Sea, which is particularly remote, and suggested for an area of conservation. By analyzing gastrointestinal tracts of 40 specimens from five species, we report an overall microplastic incidence rate of 0.23. This is lower than recent studies have found for other species in the Southern Ocean, and below global means. The highest incidence rate was detected in L. squamifrons (0.67), followed by P. evansii (0.29). The most common polymer was polyethylene recovered as 8 particles (42.1 %) from one specimen, while from the remaining 11 microplastics polyester was most common (36.8 %). This study shows that even in a remote region of the Antarctic Ocean with almost no vessel traffic, fisheries or touristic activity, bathydemersal and bathypelagic fish exhibit microplastic particles in their gastrointestinal tract.

Do plastic clean-up technologies work? What research does (and doesn't) tell us

Plastic pollution harms all levels of ecosystems and organisms; therefore, global plastic pollution must be addressed at all plastic life-cycle stages. One solution involves the clean-up and remediation of plastic pollution using technologies. To further our understanding of these technologies, we collated 102 clean-up technologies invented to prevent or collect plastic in aquatic environments and analyzed the non-peer-reviewed and peer-reviewed literature for effectiveness and ecological impact data. Across all available literature, effectiveness data were under-reported, lacked standardization, and were rarely tested by a neutral third party. This makes it difficult to make informed decisions when choosing which clean-up technology to deploy and evaluate the environmental impact of these technologies. Regulation and standardized reporting guidelines for clean-up technologies are an important next step for decision-makers interested in plastic pollution clean-up. As global interest in addressing plastic pollution grows, this research paves the path for the effective use of plastic clean-up technologies.

Investigating Exposure and Hazards of Micro- and Nanoplastics During Pregnancy and Early Life (AURORA Project): Protocol for an Interdisciplinary Study

BACKGROUND

Micro- and nanoplastics (MNPs) are emerging pollutants of concern with ubiquitous presence in global ecosystems. MNPs pose potential implications for human health; however, the health impacts of MNP exposures are not yet understood. Recent evidence suggests that MNPs can cross the placental barrier, underlying the urgent need to understand their impact on reproductive health and development.

OBJECTIVE

The Actionable eUropean ROadmap for early-life health Risk Assessment of micro- and nanoplastics (AURORA) project will investigate MNP exposures and their biological and health effects during pregnancy and early life, which are critical periods due to heightened vulnerability to environmental stressors. The AURORA project will enhance exposure assessment capabilities for measuring MNPs, MNP-associated chemicals, and plastic additives in human tissues, including placenta and blood.

METHODS

In this interdisciplinary project, we will advance methods for in-depth characterization and scalable chemical analytical strategies, enabling high-resolution and large-scale toxicological, exposure assessment, and epidemiological studies. The AURORA project performs observational studies to investigate determinants and health impacts of MNPs by including 800 mother-child pairs from 2 existing birth cohorts and 110 women of reproductive age from a newly established cohort. This will be complemented by toxicological studies using a tiered-testing approach and epidemiological investigations to evaluate associations between maternal and prenatal MNP exposures and health perturbations, such as placental function, immune-inflammatory responses, oxidative stress, accelerated aging, endocrine disruption, and child growth and development. The ultimate goal of the AURORA project is to create an MNP risk assessment framework and identify the remaining knowledge gaps and priorities needed to comprehensively assess the impact of MNPs on early-life health.

RESULTS

In the first 3 years of this 5-year project (2021-2026), progress was made toward all objectives. This includes completion of recruitment and data collection for new and existing cohorts, development of analytical methodological protocols, and initiation of the toxicological tiered assessments. As of September 2024, data analysis is ongoing and results are expected to be published starting in 2025.

CONCLUSIONS

As plastic pollution increases globally, it is imperative to understand the impact of MNPs on human health, particularly during vulnerable developmental stages such as early life. The contributions of the AURORA project will inform future risk assessment.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/63176.

Floating microplastics in Svalbard fjords: High spatial variability requires methodological consistency in estuarine systems

Microplastic pollution was studied in surface waters of Isfjorden, Svalbard in July 2021 as a part of an international regional harmonisation exercise. Surface microplastics (0.5-5 mm) were sampled with a neuston net in triplicate per study site in several branches of Isfjorden, covering populated and unpopulated fjords. High spatial variability of microplastic abundance (0-32,700 items/km2) was observed within a single fjord resulting from the hydrodynamic pattern formed through the interaction of surface currents, freshwater runoff, and wind conditions. Maximum microplastic abundance was not correlated with the distance from the local source and was instead defined by local small-scale hydrodynamics. Future recommendations for correct assessment of surface microplastics concentration in estuarine environments are presented.

Monitoring of contamination by microplastics on sandy beaches at Vulcano Island (Sicily, Italy) by hyperspectral imaging

In this work, the monitoring and characterization of large microplastics (1-5 mm) collected from sandy beaches of Vulcano Island (Aeolian Islands, Sicily, Italy) were carried out for the first time. Microplastics were sampled from two beaches, "Gelso" and "Sabbie Nere," in three different time periods. The following characteristics of microplastic samples were assessed: quantity, distribution, categories, color, polymer type, size, and shape parameters. The polymers were identified using hyperspectral imaging, whereas an automatic image analysis approach was employed to determine microplastics' morphological and morphometrical attributes. Finally, the microplastic diversity integrated index was computed to obtain information on the potential emission sources of microplastics. It was found that the concentration of microplastics varies from 0.27 particles/kg_dw to 1.35 particles/kg_dw with fragment being the main collected category, with minor amount of pellet, foam, film, and filament. The predominant color of microplastics was by far white, followed by blue and yellow. The identified polymers were polyethylene and polypropylene followed by expanded polystyrene, polyamide, polystyrene, and polyethylene terephthalate. The morphological and morphometrical characterization highlighted a large variability for most size and shape parameters. Finally, the Microplastics Diversity Integrated Index results showed average indices compared to the literature, with higher values for the "Gelso" site (0.656), indicating a higher heterogeneity of sources, with respect to "Sabbie Nere" beach (0.530).

Is intravenous infusion an unrecognized route for internal microplastic human exposure? A general assessment

As newly recognized environmental pollutants, microplastics (MPs, ≤5 mm in length) have been reported in various human tissues and fluids, including the spleen, liver, heart, blood and blood clots, raising global concerns about their impact on human health. This study investigated the characteristics of MPs in intravenous infusion and the removal of MPs from infusion products by infusion sets fitted with different filters using micro-Fourier Transform Infrared Spectroscopy. MPs were detected in infusion products, with an average abundance of 1.24 ± 1.44 items/unit (2.91 ± 3.91 items/L). The primary types of MPs identified were fragmented particles of polyethene and polypropylene, ranging in size from 15-100 µm. Internal filters in infusion sets played a crucial role in removing MPs, particularly fibrous ones, resulting in a reduction in both abundance and particle size of MPs in the human body. Moreover, this study conducted a general assessment of intravenous microplastic exposure among hospital patients and estimated the global per-person input of MPs via intravenous administration. It is an opportunity for us to gain a deeper understanding of MPs in intravenous infusion and provides guides selecting infusion devices, increasing awareness of associated health risks.

Eco-toxic Risk Assessment of microplastics in water and sediment across Nigeria Offshore, Gulf of Guinea

Globally, the environmental impacts of microplastics (MPs) as emerging pollutants have drawn a lot of attention. This study aimed to assess the distribution and associated potential ecotoxic risk of MPs in the water and sediment of Nigeria's offshore waters. Water and sediment samples were collected from sixteen (16) stations in October 2023 and analysed using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and stereomicroscopy. For physical characterization, the composition of MPs in sediment and water was 73 particles/kg and 48 particles/L, respectively, while the ATR-FTIR composition at the Eastern Zone (EZ) was 705 particles/L and 1033 particles/kg, the Central Zone (CZ) was 212 particles/L and 338 particles/kg, and the Western Zone (WZ) was 223 particles/L and 218 particles/kg. The identified MPs shapes were filaments, plastic films, fibre, and microbeads. Polychloroprene (CR) (18.10% and 16.86%) at EZ and CZ and polyvinyl alcohol (PVA) (20.64%) at WZ were most abundant in sediment, respectively. In comparison, PVA (22.3%, 22.2%, and 21.08%) was most abundant across EZ, CZ, and WZ in water. The polymer-based plastic contamination factors (ppCf) and pollution load index (pPLI) showed low contamination and pollution load, and the polymer risk index (pRi) showed medium and low risk in water and sediment, respectively. The polymer ecological risks index (pERI) showed a high-risk level (pERI: 1,001-10,000) in water and sediment across the EZ, CZ, and WZ of the Nigerian offshore waters. In marine environments, an extensive environmental monitoring program and trend forecasting for microplastics are crucial. This study will provide theoretical and technical support for developing efficient legislation or policy on the prevention and control of plastic pollution.

Beyond microbeads: Examining the role of cosmetics in microplastic pollution and spotlighting unanswered questions

The presence of microplastics in cosmetics and personal care products (C&PCPs) has been increasingly in the public eye since the early 2010s. Despite increasing research into the potential environmental and health effects of microplastics, most research to date on microplastics in C&PCPs has investigated "rinse-off" products, while the potential impacts of "leave-on" C&PCPs have been largely neglected, despite these products being purchased in greater volumes and often having two or more microplastic ingredients in their formulations(CosmeticsEurope, 2018b). This review aims to synthesize the current knowledge of microplastic in C&PCPs, assessing the potential environmental and human health impacts of C&PCPs and discussing the regulatory implications. The lack of studies on leave-on C&PCPs is significant, suggesting a severe knowledge gap regarding microplastic presence in, and emissions from, C&PCPs. There is a noticeable lack of studies on the (eco)toxicological consequences of microplastic exposure from C&PCPs. As a result, significant aspects of microplastic contamination may be overlooked in the microplastic legislations emerging globally (including from the European Commission), which intend to restrict microplastic use in C&PCPs but focus on rinse-off C&PCPs only. This review highlights the potential consequences of microplastics in leave-on C&PCPs for regulatory decision-making, particularly as alternatives to microplastics are considered during the phase-out periods and spotlights the need for sufficient monitoring and research on these alternatives, to avoid unforeseen consequences.

The use of vibrational spectroscopy and supervised machine learning for chemical identification of plastics ingested by seabirds

Plastic pollution is now ubiquitous in the environment and represents a growing threat to wildlife, who can mistake plastic for food and ingest it. Tackling this problem requires reliable, consistent methods for monitoring plastic pollution ingested by seabirds and other marine fauna, including methods for identifying different types of plastic. This study presents a robust method for the rapid, reliable chemical characterisation of ingested plastics in the 1-50 mm size range using infrared and Raman spectroscopy. We analysed 246 objects ingested by Flesh-footed Shearwaters (Ardenna carneipes) from Lord Howe Island, Australia, and compared the data yielded by each technique: 92 % of ingested objects visually identified as plastic were confirmed by spectroscopy, 98 % of those were low density polymers such as polyethylene, polypropylene, or their copolymers. Ingested plastics exhibit significant spectral evidence of biological contamination compared to other reports, which hinders identification by conventional library searching. Machine learning can be used to identify ingested plastics by their vibrational spectra with up to 93 % accuracy. Overall, we find that infrared is the more effective technique for identifying ingested plastics in this size range, and that appropriately trained machine learning models can be superior to conventional library searching methods for identifying plastics.

A study on the effect of fluorescently stained micro(nano)plastics on the full life history of Skeletonema costatum

As a new type of environmental pollutant, micro(nano)plastics have become a research hotspot in recent years, and their effects on the full life history of marine microalgae have not been studied. To investigate the effects of micro(nano)plastics on the growth, photosynthesis, physiological morphology and interaction of microalgae during the full life cycle, we selected fluorescently stained polystyrene (PS) plastic microbeads as the target pollutant. By sampling and testing the growth rate, photosynthesis and physiological morphology parameters of algal species, the influence of different concentrations of PS (10, 50 and 100 mg/L) and different particle sizes (0.1, 0.5 and 1 μm) on the full life history of Skeletonema costatum (S. costatum) was investigated. The results showed that after adding PS (particle sizes of 0.5 and 1 μm), the response of S. costatum showed a dual character, while adding the same kind of microplastics (MPs) with a particle size of 0.1 μm inhibited S. costatum throughout the full life cycle. Compared with previous studies, short-term experimental data may overestimate the true ecological risks of MPs. In addition, 0.1 μm fluorescent-stained MPs obviously accumulated around the microalgae, indicating that MPs mainly adhered to the surface of algal cells and may enter the food chain by direct or indirect ways, which can cause negative effects on the aquatic ecosystem. This study supports a more accurate assessment of the true risk of MPs to marine aquatic ecosystems.

Design of a Weathering Chamber for UV Aging of Microplastics in the Mediterranean Region

Microplastics are an ever-growing concern in the environment. Their degradation may lead to greater absorption of toxic pollutants, which may ultimately pose a threat to human health. In the pursuit of understanding microplastics' fate, behavior, and toxicity, there is a vital need to understand their aging and weathering. For this, multiple weathering setup designs were put forward. However, standardization of a weathering setup presents a significant challenge to the field due to apparatus costs, wide range of experimental parameters, or the lack of detailed reporting. This work seeks to make much-needed data gathering more accessible by constructing a low-cost weathering chamber that simulates Mediterranean shore conditions. The weathering chamber incorporates UV irradiation, mechanical abrasion, and elevated temperatures. After extensive preliminary testing, the chamber was able to achieve the desired outcome along with UV-A irradiance values, which were similar to those in the Mediterranean.

Research priorities on microplastics in marine and coastal environments: An Australian perspective to advance global action

Plastic and microplastic contamination in the environment receive global attention, with calls for the synthesis of scientific evidence to inform actionable strategies and policy-relevant practices. We provide a systematic literature review on microplastic research across Australian coastal environments in water, sediment and biota, highlighting the main research foci and gaps in information. At the same time, we conducted surveys and workshops to gather expert opinions from multiple stakeholders (including researchers, industry, and government) to identify critical research directions to meet stakeholder needs across sectors. Through this consultation and engagement process, we created a platform for knowledge exchange and identified three major priorities to support evidence-based policy, regulation, and management. These include a need for (i) method harmonisation in microplastic assessments, (ii) information on the presence, sources, and pathways of plastic pollution, and (iii) advancing our understanding of the risk of harm to individuals and ecosystems.

Efficacy of chemical digestion methods to reveal undamaged microplastics from planktonic samples

Standardisation and validation of methods for microplastics research is essential. A major methodological challenge is the removal of planktonic organisms from marine water samples allowing for the identification of microplastics associated to planktonic communities. To improve the reproducibility and accuracy of digestion methods for the removal of planktonic biomass, we compared and modified existing chemical digestion methods. These digestion methods included an acidic digestion using nitric acid, alkaline digestions with potassium hydroxide (alkaline 1 digestion) and sodium hydroxide from drain cleaner (alkaline 2 digestion), an oxidative digestion using sodium dodecyl sulfate with hydrogen peroxide, and an enzymatic digestion using enzyme drain clean pellets. Chemical digestion of three densities of zooplankton communities (high, medium, and low) in the presence of five commonly found environmental microplastic pollutants (polyamide, polyethylene, polyethylene terephthalate, polypropylene, and polystyrene) were performed for each treatment. The chemical treatments were assessed for (i) their digestion efficiency of zooplankton communities by different biomass densities, and (ii) their impact on microplastic particles through the comparison of both chemical (Raman spectroscopy) and physical (length, width, and visual) changes, between the pre-treatment and post-treatment microplastic particles. The alkaline 1, alkaline 2 and oxidative methods demonstrated significantly better digestion efficiency (p < 0.05) than the modified enzymatic and acidic treatments. The acidic, alkaline 1, and alkaline 2, treatments caused the most damages to the microplastic particles. We suggest future studies to implement the oxidative digestion method with sodium dodecyl sulfate and hydrogen peroxide because of its high digestion efficiency, and low damage to microplastic particles. This method is similar to the wet peroxide oxidation digestion method used throughout the literature but can be implemented at a lower cost.

Vertical distribution of microplastics in an agricultural soil after long-term treatment with sewage sludge and mineral fertiliser

Sewage sludge applications release contaminants to agricultural soils, such as potentially toxic metals and microplastics (MPs). However, factors determining the subsequent mobility of MPs in long-term field conditions are poorly understood. This study aimed to understand the vertical distribution of MPs in soils amended with sewage sludge in comparison to conventional mineral fertiliser for 24 years. The depth-dependent MP mass and number concentrations, plastic types, sizes and shapes were compared with the distribution of organic carbon and metals to provide insights into potentially transport-limiting factors. Polyethylene, polypropylene and polystyrene mass concentrations were screened down to 90 cm depth via pyrolysis-gas chromatography/mass spectrometry. MP number concentrations, additional plastic types, sizes, and shapes were analysed down to 40 cm depth using micro-Fourier transform-infrared imaging. Across all depths, MP numbers were twice and mass concentrations 8 times higher when sewage sludge was applied, with a higher share of textile-related plastics, more fibres and on average larger particles than in soil receiving mineral fertiliser. Transport of MPs beyond the plough layer (0-20 cm) is often assumed negligible, but substantial MP numbers (42 %) and mass (52 %) were detected down to 70 cm in sewage sludge-amended soils. The initial mobilization of MPs was shape- and size-dependent, because the fractions of fragmental-shaped and relatively small MPs increased directly below the plough layer, but not at greater depths. The sharp decline of total MP concentrations between 20 and 40 cm depth resembled that of metals and organic matter suggesting similar transport limitations. We hypothesize that the effect of soil management, such as ploughing, on soil compactness and subsequent transport by bioturbation and via macropores drives vertical MP distribution over long time scales. Risk assessment in soils should therefore account for considerable MP displacement to avoid underestimating soil exposure.

Is paper bag plastic-free, without plastic in colourful logo area?

The concern over plastic contamination has led to bans on plastic shopping bags, often replaced by paper ones. However, logos painted or printed on paper bags may still contain plastics, as investigated herein. In some logos, for example, white pigment of titanium dioxide (TiO2) nanoparticles are bound with plastic binder onto the cellulose surface of the paper. This hybrid of plastic and nanoparticle is examined using scanning electron microscope (SEM) to characterise morphology physically, and Raman imaging to identify and visualise them chemically. Raman imaging scans the sample to separate images and identify not only plastic but also the co-formulated pigment. The scan generates a hyperspectral matrix containing hundreds to thousands of spectra, and subsequent analysis can enhance the signal-to-noise ratio. Decoding the hyperspectral matrix using chemometrics like principal component analysis (PCA) can effectively map plastic and pigment separately with increased certainty. The image can be further refined through 3-dimensional surface fitting for deconvolution, providing direct visualisation of the plastic-nanoparticle hybrid at a density of approximately 7.3 million particles per square millimetre. Overall, caution should be exercised when using paper bags, as they may not be entirely free of plastics. Raman imaging proves to be an effective method for identifying and visualising complex components, including plastics and nanoparticles. ENVIRONMENTAL IMPLICATION: The concern over plastic contamination has led to bans on plastic shopping bags, replaced by paper alternatives. However, some logos on paper bags may still contain plastics, which is investigated to confirm the presence of plastic-nanoparticle hybrid using SEM and Raman imaging. By employing decoding algorithms such as PCA to separately map plastic and pigment, and utilising 3D surface fitting to deconvolute the image, the hybrid plastic-nanoparticle is estimated at a density of approximately 7.3 million particles per square millimetre. It's important to exercise caution and not assume these items are plastic-free. This aspect of plastics may have been overlooked as another potential source of contamination.

Unveiling high concentrations of small microplastics (11-500 μm) in surface water samples from the southern Weddell Sea off Antarctica

Recent studies have highlighted the prevalence of microplastic (MP) pollution in the global marine environment and these pollutants have been found to contaminate even remote regions, including the Southern Ocean south of the polar front. Previous studies in this region have mostly focused on MPs larger than 300 μm, potentially underestimating the extent of MP pollution. This study is the first to investigate MPs in marine surface waters south of the polar front, with a focus on small MPs 500-11 μm in size. Seventeen surface water samples were collected in the southern Weddell Sea using an in-house-designed sampling system. The analysis of the entire sample using micro-Fourier transform infrared spectroscopy (μFTIR) with focal plane array (FPA) detection revealed the presence of MPs in all samples, with the vast majority of the MPs detected being smaller than 300 μm (98.3 %). The mean concentration reached 43.5 (± 83.8) MPs m-3, with a wide range from 0.5 to 267.2 MPs m-3. The samples with the highest concentrations differed from the other samples in that they were collected north of the continental slope and the Antarctic Slope Current. Sea ice conditions possibly also influenced these varying concentrations. This study reports high concentrations of MPs compared to other studies in the region. It emphasizes the need to analyze small MPs, down to a size of 11 μm or even smaller, in the Antarctic Treaty Area to gain a more comprehensive understanding of MP pollution and its potential ecological impacts.

Investigation of microplastics in advanced biological wastewater treatment plant effluent

In recent years, plastic pollution in the environment has also increased due to the increasing production and consumption of plastics worldwide. The presence of microplastics (MPs) in the environment from different sources is observed almost everywhere, especially in aquatic environments. A standard method for sampling, identification, and quantification of MPs in wastewater has not yet been established. In this study, it was aimed to determine the MPs and their characteristics in the effluent of an advanced biological domestic wastewater treatment plant. The seasonal changes of MPs in a year were revealed. Pre-treatments suitable for the studied wastewater were developed for visual determination of MPs. Fibers are the dominant type of MPs, with numbers ranging between 32.0 and 95.5 particle/L. MPs in five different polymer structures were determined by FTIR analysis. These are Polyethylene, Polypropylene, Polyester, Polyurethane and Polyethylene terephthalate. The results were evaluated according to QA/QC and determined to meet the standards.

Advancing microplastic surveillance through photoacoustic imaging and deep learning techniques

Microplastic contamination presents a significant global environmental threat, yet scientific understanding of its morphological distribution within ecosystems remains limited. This study introduces a pioneering method for comprehensive microplastic assessment and environmental monitoring, integrating photoacoustic imaging and advanced deep learning techniques. Rigorous curation of diverse microplastic datasets enhances model training, yielding a high-resolution imaging dataset focused on shape-based discrimination. The introduction of the Vector-Quantized Variational Auto Encoder (VQVAE2) deep learning model signifies a substantial advancement, demonstrating exceptional proficiency in image dimensionality reduction and clustering. Furthermore, the utilization of Vector Quantization Microplastic Photoacoustic imaging (VQMPA) with a proxy task before decoding enhances feature extraction, enabling simultaneous microplastic analysis and discrimination. Despite inherent limitations, this study lays a robust foundation for future research, suggesting avenues for enhancing microplastic identification precision through expanded sample sizes and complementary methodologies like spectroscopy. In conclusion, this innovative approach not only advances microplastic monitoring but also provides valuable insights for future environmental investigations, highlighting the potential of photoacoustic imaging and deep learning in bolstering sustainable environmental monitoring efforts.

Snapshot Sampling May Not Be Enough to Obtain Robust Estimates for Riverine Microplastic Loads

Wastewater treatment plants (WWTPs) have been described as key contributors of microplastics (MPs) to aquatic systems, yet temporal fluctuations in MP concentrations and loads downstream are underexplored. This study investigated how different sampling frequencies (hourly, weekly, and monthly) affect MP estimates in a stream linked to a single WWTP. Utilizing fluorescence microscopy and Raman spectroscopy, considerable hourly variations in MP concentrations were discovered, while the polymer composition remained consistent. This temporal variability in MP loads was influenced by MP concentration, discharge rates, or a mix of both. These results show a high uncertainty, as relying on sparse snapshot samples combined with annual discharge data led to significant uncertainties in MP load estimates (over- and/or underestimation of emissions by 3.8 billion MPs annually at this site). Our findings stress the necessity of higher-frequency sampling for better comprehending the hydrodynamic factors influencing MP transport. This improved understanding enables a more accurate quantification of MP dynamics, crucial for downstream impact assessments. Therefore, preliminary reconnaissance campaigns are essential for designing extended, representative site-monitoring programs and ensuring more precise trend predictions on a larger scale.

Assessing the current state of plastic pollution research in Antarctica: Knowledge gaps and recommendations

Antarctica stands as one of the most isolated and pristine regions on our planet. Regardless, recent studies have evidenced the presence of plastic pollution in Antarctic environments and biota. While these findings are alarming and put into perspective the reach of plastic pollution, it is necessary to assess the current knowledge of plastic pollution in Antarctica. In the present review, an updated literature review of plastic pollution in multiple Antarctic environmental compartments and biota was conducted. Studies were cataloged based on environmental compartments (e.g., sediments, seawater, soil, atmosphere) and biota from different ecological niches. A detailed analysis of the main findings, as well as the flaws and shortcomings across studies, was conducted. In general terms, several studies have shown a lack of adequate sampling and analytical procedures for plastic research (particularly in the case of microplastics) and standard procedures; thus, compromising the reliability of the data reported and comparability across studies. Aiming to guide future studies and highlight research needs, a list of knowledge gaps and recommendations were provided based on the analysis and discussion of the literature and following standardized procedures.

Microplastic contamination in salt-cured fish and commercial sea salts: an emerging food safety threat in relation to UN Sustainable Development Goals (SDGs)

Microplastic (MP) contamination in seafood, particularly processed varieties like dried and salt-cured fish, poses a significant threat to human health. This study investigated MP levels in 22 salt-cured fish species and commercial sea salts along the Indian east coast. Results showed substantially higher MP concentrations compared to global averages, with fragments and fibres (< 250 µm) composing 70% of identified MPs, primarily PVC and PS polymers (> 55%). Station 2 exhibited high pollution levels, with salt-cured fish averaging 54.06 ± 14.48 MP items/g and salt containing 23.53 ± 4.2 MP items/g, indicating a high hazard risk index. A modest correlation was observed between MP abundance, morphotypes, polymer composition in the salt, and their impact on fish products. Given the critical link between food safety, security, and public health, further research is imperative to mitigate MP contamination, aligning with UN Sustainable Development Goals (Goal 2, Goal 3, Goal 14, and Goal 15) for enhanced food safety and security.

Microplastics in the Indian and South Atlantic oceans translocate to gills, digestive glands, and muscle of the chokka squid Loligo reynaudii

Comparative microplastic (MP) data for cephalopods between oceans is scarce. Our aim was to quantify, characterise, and compare MPs in gills, digestive gland, and mantle of chokka squid from the South Atlantic Ocean (SAO) and Indian Ocean (IO) off the coast of South Africa. South African squid had more MPs compared with other studies (means = 2.0 and 0.4 in SAO and IO squid mantle, respectively). Blue fibres were dominant. Identifiable MPs were polyethylene. Despite IO water having higher MP concentrations than the SAO, SAO squid had higher MP concentrations. Dilution by growth is the likely reason for the lower MP concentrations. Fibres were shorter in SAO than IO squid. However, we could not explain why fibre and mantle lengths from both oceans were positively correlated. Squid may not be the best indicator of marine MPs. The characteristics of MPs in squid can be used to track stocks and migrations.

Blueprint for the design, construction, and validation of a plastic and phthalate-minimised laboratory

Micro and nanosized plastics (MNPs), and a range of associated additive chemicals, have become pervasive contaminants that humans and the environment are exposed to everyday. However, one of the principal challenges in their analysis is adequate strategies to minimise background contamination. Here a blueprint for a specialised plastics and additive-minimised clean room laboratory built for this purpose is presented. Common laboratory construction materials (n = 23) were tested, including acoustic baffles, ceiling materials, floor materials, glazing rubber, and silicone sealant. The % polymer content ranged from 2-76% w/w while the sum concentration of six phthalates ranged from 0.81 (0.73-0.86) to 21000 (15000-27000) mg/kg, assigning many of these materials as inappropriate for use in a clean room environment. The final design of the laboratory consisted of three interconnected rooms, operated under positive pressure with the inner rooms constructed almost entirely of stainless steel. Background concentrations of MNPs and phthalates in the new laboratory were compared to two Physical Containment Level 2 (PC2) laboratory environments, with concentrations of MNPs reduced by > 100 times and phthalates reduced by up to 120 times. This study reports the first known clean room of its kind and provides a blueprint for reference and use by future plastics research.

At second glance: The importance of strict quality control - A case study on microplastic in the Southern Ocean key species Antarctic krill, Euphausia superba

The stomach content of 60 krill specimens from the Southern Ocean were analyzed for the presence of microplastic (MP), by testing different sample volumes, extraction approaches, and applying hyperspectral imaging Fourier-transform infrared spectroscopy (μFTIR). Strict quality control was applied on the generated results. A high load of residual materials in pooled samples hampered the analysis and avoided a reliable determination of putative MP particles. Individual krill stomachs displayed reliable results, however, only after re-treating the samples with hydrogen peroxide. Before this treatment, lipid rich residues of krill resulted in false assignments of polymer categories and hence, false high MP particle numbers. Finally, MP was identified in 4 stomachs out of 60, with only one MP particle per stomach. Our study highlights the importance of strict quality control to verify results before coming to a final decision on MP contamination in the environment to aid the establishment of suitable internationally standardized protocols for sampling and analysis of MP in organisms including their habitats in Southern Ocean and worldwide.

Development of a multi-spectroscopy method coupling μ-FTIR and μ-Raman analysis for one-stop detection of microplastics in environmental and biological samples

Current techniques for microplastics (MPs) analysis are diverse. However, most techniques have individual limitations like the detection limit of spatial resolution, susceptibility, high cost, and time-consuming detection. In this study, we proposed a multi-spectroscopy method coupling μ-FTIR and μ-Raman analysis for one-stop MPs detection, in which barium fluoride was used as the substrate alternative to the filter membrane. Compared with commonly used filter membranes (alumina, silver, PTFE and nylon membranes), the barium fluoride substrate showed better spectroscopic detection performance on microscopic observation, broader transmittable wavenumber range for μ-FTIR (750-4000 cm-1) and μ-Raman (250-4000 cm-1) detection, thus suitable for the multi-spectroscopy analysis of spiked samples. Further, the real environmental and biological samples (indoor air, bottled water and human exhaled breath) were collected and detected to verify the applicability of the developed multi-spectroscopy method. The results indicated that the average content of detected MPs could be increased by 30.4 ± 29.9 % for indoor air, 17.1 ± 13.2 % for bottled water and 38.4 ± 16.0 % for human exhaled breath, respectively in comparison with widely used μ-Raman detection, which suggested that MPs exposure might be underestimated using single spectroscopy detection. Moreover, the majority of underestimated MPs were colored and smaller sized (<50 μm) MPs, which could pose higher risks to human body. In addition, the proposed method consumed lower sample pre-treatment costs and was environmental-friendly since the barium fluoride substrate could be used repeatedly after being cleaned by organic solvent with reliable results (n = 10, CV = 10 %, ICC = 0.961), which reduced the cost of MPs detection by at least 2.49 times compared with traditional methods using silver membrane.

Microplastics in human urine: Characterisation using μFTIR and sampling challenges using healthy donors and endometriosis participants

Microplastics (MPs) are found in all environments, within the human food chain, and have been recently detected in several human tissues. The objective herein was to undertake an analysis of MP contamination in human urine samples, from healthy individuals and participants with endometriosis, with respect to their presence, levels, and the characteristics of any particles identified. A total of 38 human urine samples and 15 procedural blanks were analysed. MPs were characterised using μFTIR spectroscopy (size limitation of 5 μm) and SEM-EDX. In total, 123 MP particles consisting of 22 MP polymer types were identified within 17/29 of the healthy donor (10 mL) urine samples, compared with 232 MP particles of differing 16 MP polymer types in 12/19 urine samples from participants with endometriosis. Healthy donors presented an unadjusted average of 2589 ± 2931 MP/L and participants with endometriosis presented 4724 ± 9710 MP/L. Polyethylene (PE)(27%), polystyrene (PS)(16%), resin and polypropylene (PP)(both 12%) polymer types were most abundant in healthy donor samples, compared with polytetrafluoroethylene (PTFE) (59%), and PE (16%) in samples from endometriosis participants. The MP levels within healthy and endometriosis participant samples were not significantly different. However, the predominant polymer types varied, and the MPs from the metal catheter-derived endometriosis participant samples and healthy donors were significantly smaller than those observed in the procedural blanks. The procedural blank samples comprised 62 MP particles of 10 MP polymer types, mainly PP (27%), PE (21%), and PS (15%) with a mean ± SD of 17 ± 18, highlighting the unavoidable contamination inherent in measurement of MPs from donors. This is the first evidence of MP contamination in human urine with polymer characterisation and accounting for procedural blanks. These results support the phenomenon of transport of MPs within humans, specifically to the bladder, and their characterisation of types, shapes and size ranges identified therein.

Identifying laboratory sources of microplastic and nanoplastic contamination from the air, water, and consumables

Microplastic and nanoplastic research has proliferated in recent years in response to the escalating plastic pollution crisis. However, a lack of optimised methods for sampling and sample processing has potential implications for contaminating samples resulting in an overestimation of the quantity of microplastics and nanoplastics present in environmental samples. In response, a series of recommendations have been made, but most have not been quantified or validated sources of contamination. In the present study, we investigated sources of plastic contamination in common laboratory procedures including water sources (e.g., Milli-Q), consumables (e.g., unburnt glassware), airflow (e.g., fume hood) and dust. Using flow cytometry, we identified water, air flow and dust as sources of significant contamination. Milli-Q and reverse osmosis were the least contaminated sources when compared with tap water. Interestingly, current recommendations are to use glass consumables in replacement of plastic consumables, however, we have identified glassware and glass consumables as a significant source of contamination. Current best practice is to cover the glass tube with aluminium foil to reduce airborne contamination, but we found fresh aluminium foil to be a significant source of contamination, bringing light to the limitations foil has as a contamination control measure. Lastly, we identified significant quantities of microplastics and nanoplastics present in dust collected within the laboratory, suggesting this is a widespread and underestimated source of contamination. We have provided validated sources of contamination for both consumables and common laboratory procedures and provided mitigation strategies based on these. Additional recommendations include the appropriate design of experimental controls to quantify levels of introduced contamination based on methods and the detection techniques utilised. The application of these mitigation strategies and appropriate experimental design will allow for more accurate estimations on the level of microplastic and nanoplastic contamination within environmental samples.

Extent and risks of microplastic pollution in the Yangtze River. State of the science

The Yangtze River (YR) is the longest river in Asia and the third longest in the world, and is recognized as one of the most microplastic-polluted rivers globally. However, to date, no consistent and systematic risk assessment has been conducted for the YR basin or other rivers in China. Previous assessments of microplastic occurrence, distribution, or risks in the YR basin did not take into account the sometimes-limited quality of the data or compared incomparable data, which can lead to biased assessments. The actual prospective ecological risks of microplastic pollution in the YR basin are therefore unknown. In this review, we analyze data from 21 microplastic studies to assess the occurrence and distribution of microplastics and their characteristics. We also evaluate the quality of the studies using updated quality assurance/quality control (QA/QC) criteria. Although we observe an upward trend in QA/QC scores, indicating improved data quality, no study received positive scores on all critical criteria. The microplastic exposure data from the YR basin is among the highest reported for rivers and other aquatic systems worldwide, exceeding effect thresholds in some parts of the river. We recommend generating comprehensive monitoring data of higher quality, with a greater emphasis on smaller-size microplastics, so that future risk assessments can be performed with less reliance on data alignment.

Impact of a nanofiltration system on microplastic contamination in Geneva groundwater (Switzerland)

Microplastics (MPs) have been observed in the oceans, fresh waters, karstic water and remote water bodies. However, little is known on groundwater contamination, which is a natural resource of utmost importance for millions of people and is often perceived as a reliable source of water. Moreover, nanofiltration is perceived as a reliable technology to remove contaminants from water. In this study, large sample volumes of a silty-sandy gravel aquifer and the corresponding nanofiltered water were analysed for the presence of MPs (> 20 µm) using Fourier transform infrared (FTIR) microscopy. Concentration in ground water was 8 ± 7 MPs/m3 and increased to 36 ± 11 MPs/m3 in nanofiltered water. All MPs had a maximum Ferret diameter lower than 500 µm. Size distribution of MPs was towards the small size class (20-50 µm). In groundwater, 33% of MPs were detected in the smallest size class (20-50 µm) and 67% in the 50-100-µm-size class. In comparison, around 52% of MPs in nanofiltered water were observed in the 20-50 µm size class. Moreover, 33% of the MPs observed in nanofiltered water were in the 50-100 µm size class and 15% in the 100-500-µm-size class. From a chemical point of view, different plastic polymers were identified in groundwater and in nanofiltered water, such as polypropylene (PP), polyvinyl chloride (PVC), ethylene (vinyl acetate) copolymer (EVA), polyethylene (PE), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA) and other polymer materials (such as polystyrene-based copolymers, vinyl-based copolymers). Fibres were observed in all samples, but only a small number of fibres (near 1%) were identified as PP synthetic fibres in nanofiltered water. Furthermore, no clear difference of fibre concentrations was observed between groundwater (232 ± 127 fibres/m3) and nanofiltered water (247 ± 118 fibres/m3). Groundwater had extremely low levels of microplastics, and although the nanofiltration effectively removes suspended particulate matter, it slightly contaminates the filtered water with MPs.

Occurrence of microplastic pollution in rivers globally: Driving factors of distribution and ecological risk assessment

Microplastics, as global emerging pollutants, have received significant attention worldwide due to their ubiquitous presence in the rivers. However, there is still a lack of clarity on the occurrence, driving factors, and ecological risks of microplastics in rivers worldwide. In this study, a global microplastic dataset based on 862 water samples and 445 sediment samples obtained from 63 articles was constructed, which revealed the temporal and spatial distribution of abundance and morphological characteristics of microplastics in rivers across the globe. In global rivers, the abundance of MPs in both water and sediment spans across 10 and 4 orders of magnitude, respectively. The MP comprehensive diversity index based on the physical morphological characteristics of MPs indicated a significant positive correlation between the pollution sources of MPs in different environmental media. Based on the data was aligned to the full-scale MPs, a novel framework was provided to evaluate the ecological risk of MPs and the interaction effects between the influencing factors driving the distribution characteristics of MPs in rivers around the world. The results obtained demonstrated a wide variation in the key driving factors affecting the distribution of microplastics in different environmental media (water and sediment) in rivers globally. The diversity indices of the morphological characteristics of MPs in densely populated areas of lower-middle income countries in Asia were significantly higher, implying that the sources of microplastics in these regions are more complex and extensive. More than half of the rivers are exposed to potential ecological risks of MPs; however, microplastics may pose only immediate risks to aquatic species in Burigang River, Bangladesh. This can provide valuable insights for formulating more effective scientific strategies for the management of MP pollution in rivers.

Microplastic Effect Tests Should Use a Standard Heterogeneous Mixture: Multifarious Impacts among 16 Benthic Invertebrate Species Detected under Ecologically Relevant Test Conditions

Microplastics require a risk assessment framework that takes their multidimensionality into account while exclusively considering robust data. Therefore, effect tests should use a diverse, environmentally relevant microplastic (ERMP) standard material that adheres to high-quality requirements. In this study, we provide chronic dose-effect relationships and effect thresholds for 16 benthic species exposed to ERMP. The ERMP was created from plastic items collected from natural sources and cryogenically milled to represent the diversity of microplastics. The test design met 20 previously published quality assurance and quality control criteria. Adverse effect thresholds (EC10) were determined at ERMP concentrations of 0.11 ± 0.17% sediment dry weight (Gammarus pulex, growth), 0.49 ± 0.68% sediment dry weight (Lumbriculus variegatus, growth), and 1.90 ± 1.08% sediment dry weight (L. variegatus, reproduction). A positive effect of microplastics, such as decreased mortality, was observed for Cerastoderma edule (EC10 = 0.021 ± 0.027% sediment dry weight) and Sphaerium corneum (EC10 = 7.67 ± 3.41% sediment dry weight), respectively. Several of these laboratory-based single-species effect thresholds for ERMP occurred at concentrations lower than those found in the environment. For other species, no significant effects were detected up to an ERMP dose of 10% dry weight.

Exposure protocol for ecotoxicity testing of microplastics and nanoplastics

Despite the increasing concern about the harmful effects of micro- and nanoplastics (MNPs), there are no harmonized guidelines or protocols yet available for MNP ecotoxicity testing. Current ecotoxicity studies often use commercial spherical particles as models for MNPs, but in nature, MNPs occur in variable shapes, sizes and chemical compositions. Moreover, protocols developed for chemicals that dissolve or form stable dispersions are currently used for assessing the ecotoxicity of MNPs. Plastic particles, however, do not dissolve and also show dynamic behavior in the exposure medium, depending on, for example, MNP physicochemical properties and the medium's conditions such as pH and ionic strength. Here we describe an exposure protocol that considers the particle-specific properties of MNPs and their dynamic behavior in exposure systems. Procedure 1 describes the top-down production of more realistic MNPs as representative of MNPs in nature and particle characterization (e.g., using thermal extraction desorption-gas chromatography/mass spectrometry). Then, we describe exposure system development for short- and long-term toxicity tests for soil (Procedure 2) and aquatic (Procedure 3) organisms. Procedures 2 and 3 explain how to modify existing ecotoxicity guidelines for chemicals to target testing MNPs in selected exposure systems. We show some examples that were used to develop the protocol to test, for example, MNP toxicity in marine rotifers, freshwater mussels, daphnids and earthworms. The present protocol takes between 24 h and 2 months, depending on the test of interest and can be applied by students, academics, environmental risk assessors and industries.

Training the next generation of plastics pollution researchers: tools, skills and career perspectives in an interdisciplinary and transdisciplinary field

Plastics pollution research attracts scientists from diverse disciplines. Many Early Career Researchers (ECRs) are drawn to this field to investigate and subsequently mitigate the negative impacts of plastics. Solving the multi-faceted plastic problem will always require breakthroughs across all levels of science disciplinarity, which supports interdisciplinary discoveries and underpins transdisciplinary solutions. In this context, ECRs have the opportunity to work across scientific discipline boundaries and connect with different stakeholders, including industry, policymakers and the public. To fully realize their potential, ECRs need to develop strong communication and project management skills to be able to effectively interface with academic peers and non-academic stakeholders. At the end of their formal education, many ECRs will choose to leave academia and pursue a career in private industry, government, research institutes or non-governmental organizations (NGOs). Here we give perspectives on how ECRs can develop the skills to tackle the challenges and opportunities of this transdisciplinary research field and how these skills can be transferred to different working sectors. We also explore how advisors can support an ECRs' growth through inclusive leadership and coaching. We further consider the roles each party may play in developing ECRs into mature scientists by helping them build a strong foundation, while also critically assessing problems in an interdisciplinary and transdisciplinary context. We hope these concepts can be useful in fostering the development of the next generation of plastics pollution researchers so they can address this global challenge more effectively.

Graphical Abstract

The NOAA NCEI marine microplastics database

Microplastics (<5 mm) pollution is a growing problem affecting coastal communities, marine ecosystems, aquatic life, and human health. The widespread occurrence of marine microplastics, and the need to curb its threats, require expansive, and continuous monitoring. While microplastic research has increased in recent years and generated significant volumes of data, there is a lack of a robust, open access, and long-term aggregation of this data. The National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI) now provides a global open access to marine microplastics data on an easily discoverable and accessible GIS web map and data portal ( https://www.ncei.noaa.gov/products/microplastics ). The objective of this data portal is to develop a repository where microplastics data are aggregated, archived, and served in a user friendly, consistent, and reliable manner. This work contributes to NCEI's efforts towards data standardization, integration, harmonization, and interoperability among national and international collaborators for monitoring global marine microplastics. This paper describes the NOAA NCEI global marine microplastics database, its creation, quality control procedures, and future directions.

Microplastics could be marginally more hazardous than natural suspended solids - A meta-analysis

Microplastics (MP) are perceived as a threat to aquatic ecosystems but bear many similarities to suspended sediments which are often considered less harmful. It is, therefore pertinent to determine if and to what extent MP are different from other particles occurring in aquatic ecosystems in terms of their adverse effects. We applied meta-regressions to toxicity data extracted from the literature and harmonized the data to construct Species Sensitivity Distributions (SSDs) for both types of particles. The results were largely inconclusive due to high uncertainty but the central tendencies of our estimates still indicate that MP could be marginally more hazardous compared to suspended sediments. In part, the high uncertainty stems from the general lack of comparable experimental studies and dose-dependent point estimates. We therefore argue that until more comparable data is presented, risk assessors should act precautionary and treat MP in the 1-1000 µm size range as marginally more hazardous to aquatic organisms capable of ingesting such particles.

The influence of complex matrices on method performance in extracting and monitoring for microplastics

Previous studies have evaluated method performance for quantifying and characterizing microplastics in clean water, but little is known about the efficacy of procedures used to extract microplastics from complex matrices. Here we provided 15 laboratories with samples representing four matrices (i.e., drinking water, fish tissue, sediment, and surface water) each spiked with a known number of microplastic particles spanning a variety of polymers, morphologies, colors, and sizes. Percent recovery (i.e., accuracy) in complex matrices was particle size dependent, with ∼60-70% recovery for particles >212 μm, but as little as 2% recovery for particles <20 μm. Extraction from sediment was most problematic, with recoveries reduced by at least one-third relative to drinking water. Though accuracy was low, the extraction procedures had no observed effect on precision or chemical identification using spectroscopy. Extraction procedures greatly increased sample processing times for all matrices with the extraction of sediment, tissue, and surface water taking approximately 16, 9, and 4 times longer than drinking water, respectively. Overall, our findings indicate that increasing accuracy and reducing sample processing times present the greatest opportunities for method improvement rather than particle identification and characterization.

Shapes of Hyperspectral Imaged Microplastics

Shape matters for microplastics, but its definition, particularly for hyperspectral imaged microplastics, remains ambiguous and inexplicit, leading to incomparability across data. Hyperspectral imaging is a common approach for quantification, yet no unambiguous microplastic shape classification exists. We conducted an expert-based survey and proposed a set of clear and concise shapes (fiber, rod, ellipse, oval, sphere, quadrilateral, triangle, free-form, and unidentifiable). The categories were validated on images of 11,042 microplastics from four environmental compartments (seven matrices: indoor air; wastewater influent, effluent, and sludge; marine water; stormwater; and stormwater pond sediments), by inviting five experts to score each shape. We found that the proposed shapes were well defined, representative, and distinguishable to the human eye, especially for fiber and sphere. Ellipse, oval, and rod were though less distinguishable but dominated in all water and solid matrices. Indoor air held more unidentifiable, an abstract shape that appeared mostly for particles below 30 μm. This study highlights the need for assessing the recognizability of chosen shape categories prior to reporting data. Shapes with a clear and stringent definition would increase comparability and reproducibility across data and promote harmonization in microplastic research.

Patterns of microparticles in blank samples: A study to inform best practices for microplastic analysis

Quality assurance and quality control (QA/QC) techniques are critical to analytical chemistry, and thus the analysis of microplastics. Procedural blanks are a key component of QA/QC for quantifying and characterizing background contamination. Although procedural blanks are becoming increasingly common in microplastics research, how researchers acquire a blank and report and/or use blank contamination data varies. Here, we use the results of laboratory procedural blanks from a method evaluation study to inform QA/QC procedures for microplastics quantification and characterization. Suspected microplastic contamination in the procedural blanks, collected by 12 participating laboratories, had between 7 and 511 particles, with a mean of 80 particles per sample (±SD 134). The most common color and morphology reported were black fibers, and the most common size fraction reported was 20-212 μm. The lack of even smaller particles is likely due to limits of detection versus lack of contamination, as very few labs reported particles <20 μm. Participating labs used a range of QA/QC techniques, including air filtration, filtered water, and working in contained/'enclosed' environments. Our analyses showed that these procedures did not significantly affect blank contamination. To inform blank subtraction, several subtraction methods were tested. No clear pattern based on total recovery was observed. Despite our results, we recommend commonly accepted procedures such as thorough training and cleaning procedures, air filtration, filtered water (e.g., MilliQ, deionized or reverse osmosis), non-synthetic clothing policies and 'enclosed' air flow systems (e.g., clean cabinet). We also recommend blank subtracting by a combination of particle characteristics (color, morphology and size fraction), as it likely provides final microplastic particle characteristics that are most representative of the sample. Further work should be done to assess other QA/QC parameters, such as the use of other types of blanks (e.g., field blanks, matrix blanks) and limits of detection and quantification.

A Complete Guide to Extraction Methods of Microplastics from Complex Environmental Matrices

Sustainable development is a big global challenge for the 21st century. In recent years, a class of emerging contaminants known as microplastics (MPs) has been identified as a significant pollutant with the potential to harm ecosystems. These small plastic particles have been found in every compartment of the planet, with aquatic habitats serving as the ultimate sink. The challenge to extract MPs from different environmental matrices is a tangible and imperative issue. One of the primary specialties of research in environmental chemistry is the development of simple, rapid, low-cost, sensitive, and selective analytical methods for the extraction and identification of MPs in the environment. The present review describes the developments in MP extraction methods from complex environmental matrices. All existing methodologies (new, old, and proof-of-concept) are discussed and evaluated for their potential usefulness to extract MPs from various biotic and abiotic matrices for the sake of progress and innovation. This study concludes by addressing the current challenges and outlining future research objectives aimed at combating MP pollution. Additionally, a set of recommendations is provided to assist researchers in selecting appropriate analytical techniques for obtaining accurate results. To facilitate this process, a proposed roadmap for MP extraction is presented, considering the specific environmental compartments under investigation. By following this roadmap, researchers can enhance their understanding of MP pollution and contribute to effective mitigation strategies.

Detection of microplastics and nanoplastics released from a kitchen blender using Raman imaging

Microplastics and nanoplastics have secretly entered our daily lives but the extent of the problem is still unclear, as the characterisation is still a challenge, particularly for nanoplastics. Herein we test a blender that we use in our kitchen to make juice and we find that a significant amount of microplastics and nanoplastics (∼0.36-0.78 × 10⁹ within 30 s) are released from the plastic container. We advance the characterisation of microplastics and nanoplastics using Raman imaging to generate a scanning spectrum matrix, akin to a hyperspectral matrix, which contains 900 spectra (30 × 30). By mapping these hundreds of spectra as images, with help of algorithms, we can directly visualise the microplastics and nanoplastics with an increased sensitivity from statistical point of view. Raman imaging has a main disadvantage of the imaging resolution, originating from the diffraction of the laser spot, which is proposed to be improved by shrinking the scanning pixel size, zooming in the scanning area to capture details of nanoplastics. Using image re-construction towards deconvolution, the nanoplastics can be effective characterised and the bumpy image of microplastics stemming from the signal variation can be subsequently smoothened to further increase the signal-noise ratio. Overall, the advancements on Raman imaging can provide a suitable approach to characterise microplastics and nanoplastics released in our daily lives, for which we should be cautious.

Contamination and removal efficiency of microplastics and synthetic fibres in a conventional drinking water treatment plant in Geneva, Switzerland

Although it is known that freshwater resources are contaminated with microplastics (MPs), still limited information is known about the efficiency of large drinking water treatment plants (DWTP) to remove microplastics. Moreover, reported concentrations of MPs in drinking water variates from some units to thousands of units per litre and the sampling volumes used for MPs analysis are generally heterogeneous and limited. The present study evaluates the removal of MPs and synthetic fibres in the main DWTP of Geneva, Switzerland, by considering large sampling volumes at different time intervals. Furthermore, contrary to other studies, this DWTP does not count with a clarification process before sand filtration and coagulated water is sent directly to sand filtration. In this study a distinction is made between microplastics as fragments, films, pellets, and synthetic fibres. Raw water and effluents of each filtering mass (sand and activated carbon filtration) are analysed for the presence of MPs and synthetic fibres with sizes ≥63 μm using infrared spectroscopy. Concentrations of MPs in raw water range from 25.7 to 55.6 MPs/m³ and in treated water from 0 to 4 MPs/m³, respectively. Results show that 70 % of MPs are retained during sand filtration and total removal is equal to 97 % in treated water after activated carbon filtration. Concentration of identified synthetic fibres is low (average value of 2 synthetic fibres/m³) and constant in all steps of water treatment. Chemical composition of microplastics and synthetic fibres is found more heterogeneous in raw water than after sand filtration and activated carbon filtration, indicating the persistence of some types of plastics (like polyethylene and polyethylene terephthalate) in water treatment processes. Heterogeneities in MP concentrations are observed from one sampling campaign to another, indicating significant variations of MP concentrations in raw water.

Formation, behavior, properties and impact of micro- and nanoplastics on agricultural soil ecosystems (A Review)

Micro and nanoplastics (MPs and NPs, respectively) in agricultural soil ecosystems represent a pervasive global environmental concern, posing risks to soil biota, hence soil health and food security. This review provides a comprehensive and current summary of the literature on sources and properties of MNPs in agricultural ecosystems, methodology for the isolation and characterization of MNPs recovered from soil, MNP surrogate materials that mimic the size and properties of soil-borne MNPs, and transport of MNPs through the soil matrix. Furthermore, this review elucidates the impacts and risks of agricultural MNPs on crops and soil microorganisms and fauna. A significant source of MPs in soil is plasticulture, involving the use of mulch films and other plastic-based implements to provide several agronomic benefits for specialty crop production, while other sources of MPs include irrigation water and fertilizer. Long-term studies are needed to address current knowledge gaps of formation, soil surface and subsurface transport, and environmental impacts of MNPs, including for MNPs derived from biodegradable mulch films, which, although ultimately undergoing complete mineralization, will reside in soil for several months. Because of the complexity and variability of agricultural soil ecosystems and the difficulty in recovering MNPs from soil, a deeper understanding is needed for the fundamental relationships between MPs, NPs, soil biota and microbiota, including ecotoxicological effects of MNPs on earthworms, soil-dwelling invertebrates, and beneficial soil microorganisms, and soil geochemical attributes. In addition, the geometry, size distribution, fundamental and chemical properties, and concentration of MNPs contained in soils are required to develop surrogate MNP reference materials that can be used across laboratories for conducting fundamental laboratory studies.

The relationship between microplastics in eastern oysters (Crassostrea virginica) and surrounding environmental compartments in Long Island Sound

Microplastics (MP, <5 mm) are found in coastal waters across various environmental compartments (biota, water, marine snow, sediment). The eastern oyster (Crassostrea virginica) is a commercially important species that ingests MP; however, oysters are discriminant suspension feeders that do not consume all particles to which they are exposed. This study explored the relationship between MP in oysters on a recreational oyster bed and the surrounding environmental compartments in Long Island Sound (LIS; USA). The quantity and types of MP in oysters, water, marine snow, and sediment samples were determined. Precautions were taken to minimize and monitor MP contamination in the field and laboratory to improve the quality of data collected. Microplastics were isolated from samples via chemical digestion, and any suspected particles were identified using micro-Fourier transform infrared spectroscopy. A total of 86 MP were identified out of 885 suspected particles across environmental media. The highest MP count in an individual oyster was nine, indicating low concentrations of MP in oysters and the surrounding environment. Few polymers, except polyethylene terephthalate, were shared between oysters and the surrounding environmental compartments. Sediments contained the highest number of MP across all environmental compartments (42 total). These data aid in determining the types of MP (polymer composition, shape, size) to which oysters are exposed and identified those ingested. The low numbers of MP recorded, coupled with the lack of alignment of polymers between oysters and their surrounding environment, demonstrates further that oysters are a poor bioindicator species for MP pollution.

How to establish detection limits for environmental microplastics analysis

Establishing analytical detection limits is crucial. Common methods to do so are suitable only for variables with continuous distributions. Because count data for microplastic particles is a discrete variable following the Poisson distribution, currently-used approaches for estimating the detection limit in microplastics analysis are inadequate. Here we evaluate detection limits with techniques for low-level discrete observations to develop proper approaches for estimating the minimum detectable amount (MDA) in microplastic particle analysis, using blank sample data from an interlaboratory calibration exercise for clean water (representing drinking water), dirty water (ambient water), sediment (porous media) and fish tissue (biotic tissues). Two MDAs are applicable: MDA_A to evaluate analytical methods, estimated with replicate blank data; and MDA_B for individual sample batches, calculated with a single blank count. For illustrative purposes, this dataset's overall MDA_A values were 164 counts (clean water), 88 (dirty water), 192 (sediment), and 379 (tissue). MDA values should be reported on a laboratory-specific basis and for individual size fractions, as this provides more useful information about capabilities of individual laboratories. This is due to wide variation in blank levels, as noted by MDA_B values (i.e., among different laboratories) from 14 to 158 (clean water), 9 to 86 (dirty water, 9 to 186 (sediment), and 9 to 247 (tissue). MDA values for fibers were considerably greater than for non-fibers, suggesting that separate MDA values should be reported. This study provides a guideline for estimation and application of microplastics MDA for more robust data to support research activities and environmental management decisions.

Impact of Fibrous Microplastic Pollution on Commercial Seafood and Consumer Health: A Review

The omnipresence of microfibers in marine environments has raised concerns about their availability to aquatic biota, including commercial fish species. Due to their tiny size and wide distribution, microfibers may be ingested by wild-captured pelagic or benthic fish and farmed species. Humans are exposed via seafood consumption. Despite the fact that research on the impact of microfibers on marine biota is increasing, knowledge on their role in food security and safety is limited. The present review aims to examine the current knowledge about microfiber contamination in commercially relevant fish species, their impact on the marine food chain, and their probable threat to consumer health. The available information suggests that among the marine biota, edible species are also contaminated, but there is an urgent need to standardize data collection methods to assess the extent of microfiber occurrence in seafood. In this context, natural microfibers should also be investigated. A multidisciplinary approach to the microfiber issue that recognizes the interrelationship and connection of environmental health with that of animals and humans should be used, leading to the application of strategies to reduce microfiber pollution through the control of the sources and the development of remediation technologies.

Raman imaging for the analysis of silicone microplastics and nanoplastics released from a kitchen sealant

Plastic products are used ubiquitously and can potentially release microplastics and nanoplastics into the environment, for example, products such as the silicone sealant used in kitchens. It is important to develop an effective method to monitor these emerging contaminants, as reported herein. By using advanced Raman imaging to characterize microplastics and nanoplastics from hundreds of spectra in a scanning spectrum matrix and not from a single spectrum or peak, the signal-to-noise ratio can be significantly increased, from a statistical point of view. The diffraction of the laser spot usually constrains the imaging resolution (such as at ∼300 nm), which is also pushed to the limit in this report by shrinking the scanning pixel size down to ∼50 nm to capture and image small nanoplastics effectively. To this end, image reconstruction is developed to successfully pick up the meaningful Raman signal and intentionally avoid the noise. The results indicate that the silicone sealant in a kitchen can release a significant amount of microplastics and nanoplastics. Overall, advanced Raman imaging can be employed to characterize the microplastics and even nanoplastics that are smaller than the diffraction limit of the laser via Raman imaging and image reconstruction toward deconvolution.

Identification of microplastic fibres released from COVID-19 test swabs with Raman imaging

Background

COVID-19 pandemic is not yet over, and it has been generating lots of plastic wastes that become a big concern. To catch the virus, for example, no matter via antigen or PCR test, swab is generally used for sampling. Unfortunately, the swab tip is commonly made of plastics, and thus it can be a potential source of microplastics. This study aims to propose and optimise several Raman imaging to identify the microplastic fibres released from different COVID-19 test swabs.

Results

The results show that Raman imaging can effectively identify and visualise the microplastic fibres released from the swabs. In the meantime, on the surface of the fibres, additives such as titanium oxide particles are also captured for some brands of swabs. To increase the result certainty, scanning electron microscope (SEM) is first employed to get the morphology of the released microplastic fibres, along with Energy-dispersive X-ray spectroscopy (EDS) to confirm the presence of titanium element. Then, Raman imaging is advanced to identify and visualise the microplastics and titanium oxide particles, from different characteristic peaks in the scanning spectrum matrix. To further increase the imaging certainty, these images can be merged and cross-checked using algorithms, or the raw data from the scanning spectrum matrix can be analysed and decoded via chemometrics, such as principal component analysis (PCA). Beyond the advantages, the disadvantages of the confocal Raman imaging (affected by focal height) and algorithms (non-supervised calculation) are also discussed and intentionally corrected. In brief, the imaging analysis (particularly the combined SEM with Raman) is recommended to avoid the possible result bias that might be generated from the single spectrum analysis at a selective but random position.

Conclusions

Overall, the results indicate that Raman imaging can be a useful tool to detect microplastics. The results also send us a strong warning that, if we worry about the potential microplastics contamination, we should be cautious to select the suitable COVID-19 testing kits.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12302-023-00737-0.