Critical Assessment of Analytical Methods for the Harmonized and Cost-Efficient Analysis of Microplastics

Microplastics in Arctic waters of the Finnish Sámi area

We explored the presence of microplastics in the Finnish Arctic Sámi home area. A dialogue between Indigenous knowledge and scientific field work produced data about microplastics in remote wilderness aquatic ecosystems. Methods included geographical Indigenous knowledge analysis, water sampling with fraction filtration, and imaging Fourier transform infrared spectroscopy. The MPs found were small; the mean particle size was 126 ± 121 μm. Particle concentrations of MPs in freshwater and marine samples varied between 45 and 423 MPs m-3 and the most common polymer types were polyethylene, polypropylene, and polyethylene terephthalate. In conclusion, because microplastics are present even in the wilderness areas, their abundance should be monitored to assess plastic pollution in the relatively pristine Arctic environments. Sámi Indigenous knowledge proved to be a beneficial and important initiator, because locals recognize the possible sources and transport pathways of plastic litter, and practical sampling sites in the complex freshwater systems of the area.

A fluorescence approach for an online measurement technique of atmospheric microplastics

Microplastic particles in the atmosphere are regularly detected in urban areas as well as in very remote locations. Yet the sources, chemical transformation, transport, and abundance of airborne microplastics still remain largely unexplained. Therefore, their impact on health, weather and climate related processes lacks comprehensive understanding. Single particle detection presents a substantial challenge due to its time-consuming process and is conducted solely offline. To get more information about the distribution, fluxes and sources of microplastics in the atmosphere, a reliable and fast online measurement technique is of utmost importance. Here we demonstrate the use of the autofluorescence of microplastic particles for their online detection with a high sensitivity towards different widely used polymers. We deploy online, single particle fluorescence spectroscopy with a Wideband Integrated Bioaerosol Sensor WIBS 5/NEO (Droplet Measurement Technologies, USA), which enables single particle fluorescence measurements at two excitation wavelengths (280 nm and 370 nm) and in two emission windows (310-400 nm and 420-650 nm). We investigated shredded (<100 μm) everyday plastic products (drinking bottles and yogurt cups) and pure powders of polyethylene terephthalate (PET), polyethylene and polypropylene. For the broad range of typical plastic products analyzed, we detected fluorescence on a single particle level using the WIBS. The online detection can identify particles smaller than 2 μm. In the case of microplastic particles from a PET bottle, 1.2 μm sized particles can be detected with 95% efficiency. Comparison with biological aerosols reveals that microplastics can be distinguished from two abundant pollen species and investigation of the complete fluorescence excitation emission maps of all samples shows that online identification of microplastics might be possible with fluorescence techniques if multiple channels are available.

Microplastics in aquatic systems: An in-depth review of current and potential water treatment processes

Plastic products, despite their undeniable utility in modern life, pose significant environmental challenges, particularly when it comes to recycling. A crucial concern is the pervasive introduction of microplastics (MPs) into aquatic ecosystems, with deleterious effects on marine organisms. This review presents a detailed examination of the methodologies developed for MPs removal in water treatment systems. Initially, investigating the most common types of MPs in wastewater, subsequently presenting methodologies for their precise identification and quantification in aquatic environments. Instruments such as scanning electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, Raman spectroscopy, surface-enhanced Raman spectroscopy, and Raman tweezers stand out as powerful tools for studying MPs. The discussion then transitions to the exploration of both existing and emergent techniques for MPs removal in wastewater treatment plants and drinking water treatment plants. This includes a description of the core mechanisms that drive these techniques, with an emphasis on the latest research developments in MPs degradation. Present MPs removal methodologies, ranging from physical separation to chemical and biological adsorption and degradation, offer varied advantages and constraints. Addressing the MPs contamination problem in its entirety remains a significant challenge. In conclusion, the review offers a succinct overview of each technique and forwards recommendations for future research, highlighting the pressing nature of this environmental dilemma.

Challenges and Recent Analytical Advances in Micro/Nanoplastic Detection

Despite growing ecological concerns, studies on microplastics and nanoplastics are still in their initial stages owing to technical hurdles in analytical techniques, especially for nanoplastics. We provide an overview of the general attributes of micro/nanoplastics in natural environments and analytical techniques commonly used for their analysis. After demonstrating the analytical challenges associated with the identification of nanoplastics due to their distinctive characteristics, we discuss recent technological advancements for detecting nanoplastics.

Nile red staining for rapid screening of plastic-suspect particles in edible seafood tissues

Concerns regarding microplastic (MP) contamination in aquatic ecosystems and its impact on seafood require a better understanding of human dietary MP exposure including extensive monitoring. While conventional techniques for MP analysis like infrared or Raman microspectroscopy provide detailed particle information, they are limited by low sample throughput, particularly when dealing with high particle numbers in seafood due to matrix-related residues. Consequently, more rapid techniques need to be developed to meet the requirements of large-scale monitoring. This study focused on semi-automated fluorescence imaging analysis after Nile red staining for rapid MP screening in seafood. By implementing RGB-based fluorescence threshold values, the need for high operator expertise to prevent misclassification was addressed. Food-relevant MP was identified with over 95% probability and differentiated from natural polymers with a 1% error rate. Comparison with laser direct infrared imaging (LDIR), a state-of-the-art method for rapid MP analysis, showed similar particle counts, indicating plausible results. However, highly variable recovery rates attributed to inhomogeneous particle spiking experiments highlight the need for future development of certified reference material including sample preparation. The proposed method demonstrated suitability of high throughput analysis for seafood samples, requiring 0.02-0.06 h/cm2 filter surface compared to 4.5-14.7 h/cm with LDIR analysis. Overall, the method holds promise as a screening tool for more accurate yet resource-intensive MP analysis methods such as spectroscopic or thermoanalytical techniques.

Multi-method analysis of microplastic distribution by flood frequency and local topography in Rhine floodplains

Rivers are important transport pathways for microplastics into the ocean, but they can also be potential sinks due to microplastic deposition in the sediments of the river bed and adjacent floodplains. In particular, floods can (re)mobilise microplastics from sediments and floodplains, (re)deposit and relocate them depending on the floodplain topography. The knowledge about fluvial microplastic input to floodplains, their spatial distribution and their fate in floodplain soils is limited. To investigate this topic, we sampled soil at a depth of 5-20 cm along three transects in three different Rhine floodplains. We analysed the soil samples in tandem with pyrolysis GC/MS and ATR- & μ-FPA-FTIR for their microplastic abundance and mass concentrations. To study the influence of flood frequency on the microplastic abundance in the three floodplains, we fitted a hydrodynamic flood model (MIKE 21, DHI, Hørsholm, Denmark) and related the results to the respective spatial microplastic distribution. We found similar microplastic distribution patterns in each floodplain. The highest microplastic abundance (8516-70,124 microplastics kg-1) and mass concentration (46.2-141.6 mg kg-1) were consistently found in the farthest transects from the Rhine in a topographical depression. This microplastic distribution pattern is detectable with both, pyrolysis GC/MS and FTIR. The strongest correlation between the results of both methods was found for small, abundant microplastic particles. Our results suggest that the spatial distribution of microplastics in floodplains is related to the combination of flood frequency and local topography, that ought to be explicitly considered in future studies conducted in floodplains. Finally, our results indicate that pyrolysis GC/MS and FTIR data are comparable under certain conditions, which may help in the decision for the analytical method and sampling design in future studies.

Microplastics in a small river: Occurrence and influencing factors along the river Oker, Northern Germany

Much attention regarding the environmental pollution by plastics had focused on the Oceans. More recently, contamination of freshwater ecosystems has been addressed but information from smaller rivers in moderately populated catchments is still comparatively scarce. This study explored the microplastic (MP) occurrence in the small regional river Oker, Northern Germany (catchment area 1822 km2, population of ca. 500,000, discharge approx. 12 m3 s-1). MPs (fibers and fragments in the size range 0.3-5 mm, identification by microscopy) were found in all 10 in-stream samples collected along the course of the river, ranging between 28 and 134 particles m-3 with an overall average of 63 particles m-3. This MP concentration found in the small river Oker is similar to, or higher than, that reported for larger rivers in similar environments in Central Europe. On average, higher MP concentration was found at urban (71 particles m-3) compared to rural sampling sites (51 particles m-3). Within the Oker catchment, in-stream MP concentration showed no or low correlation to the catchment-scale factors of catchment size and population. Additional samples taken from three locations directly influenced by discharges of potential MP point sources confirmed wastewater treatment plants of different capacities and an urban rainwater sewer as sources. Our results support findings that MP concentrations in small rivers are crucially influenced by local sources, superimposing linear relationships to factors of catchment size and -population. They show that even small rivers draining moderately populated catchments may exhibit comparatively high concentrations of MPs, and thereby represent underestimated pathways of MP in the environment.

The biodistribution of polystyrene nanoparticles administered intravenously in the chicken embryo

Nanoplastics can cause severe malformations in chicken embryos. To improve our understanding of the toxicity of nanoplastics to embryos, we have studied their biodistribution in living chicken embryos. We injected the embryos in the vitelline vein at stages 18-19. We injected polystyrene nanoparticles (PS-NPs) tagged with europium- or fluorescence. Their biodistribution was tracked using inductively-coupled plasma mass spectrometry on tissue lysates, paraffin histology, and vibratome sections analysed by machine learning algorithms. PS-NPs were found at high levels in the heart, liver and kidneys. Furthermore, PS-NPs crossed the endocardium of the heart at sites of epithelial-mesenchymal transformation; they also crossed the liver endothelium. Finally, we detected PS-NPs in the allantoic fluid, consistent with their being excreted by the kidneys. Our study shows the power of the chicken embryo model for analysing the biodistribution of nanoplastics in embryos. Such experiments are difficult or impossible in mammalian embryos. These findings are a major advance in our understanding of the biodistribution and tissue-specific accumulation of PS-NPs in developing animals.

Sampling of microplastics at a materials recovery facility

Detecting, separating, and characterizing airborne microplastics from other airborne particulates is currently challenging due to the various instrumental constraints and related sample preparation hurdles that must be overcome. The ability to measure these real-world environments is needed to better assess the risks associated with microplastics. To that end, the current study focused on developing a methodology for sampling and characterizing airborne microplastics. Particulate sampling was carried out at a municipal materials recovery facility near a conveyer belt containing sorted plastic materials to collect airborne environmental particles on filters. Nucleopore filters were mounted on Teflon support rings, coated with 100 nm aluminum to reduce the background signal for micro-Raman spectroscopy, and marked with a fiducial pattern using a laser engraver. The fiducial pattern was crucial in identifying samples, relocating particles, and efficiently enabling orthogonal measurements on the same samples. Optimum sampling conditions of 2 h at 25 L/min were determined using light microscopy to evaluate the particle loadings. The filters were then cut into slices which were attached to sections of thin beryllium-copper sheeting for easy transfer of the filter between microscopy platforms. Scanning electron microscopy was used to identify carbon-rich particles. Light microscopy was used to identify colored particles which were also carbon-rich which were then analyzed using micro-Raman spectroscopy to identify specific polymers.

Towards a reference material for microplastics' number concentration-case study of PET in water using Raman microspectroscopy

Increasing demand for size-resolved identification and quantification of microplastic particles in drinking water and environmental samples requires the adequate validation of methods and techniques that can be used for this purpose. In turn, the feasibility of such validation depends on the existence of suitable certified reference materials (CRM). A new candidate reference material (RM), consisting of polyethylene terephthalate (PET) particles and a water matrix, has been developed. Here, we examine its suitability with respect to a homogeneous and stable microplastic particle number concentration across its individual units. A measurement series employing tailor-made software for automated counting and analysis of particles (TUM-ParticleTyper 2) coupled with Raman microspectroscopy showed evidence of the candidate RM homogeneity with a relative standard deviation of 12% of PET particle counts involving particle sizes >30 µm. Both the total particle count and the respective sums within distinct size classes were comparable in all selected candidate RM units. We demonstrate the feasibility of production of a reference material that is sufficiently homogeneous and stable with respect to the particle number concentration.

A Novel High-Throughput Detection Method for Plastic Debris in Organic-Rich Matrices Based on Image Fusion

Plastic pollution pervades natural environments and wildlife. Consequently, high-throughput detection methods for plastic debris are urgently needed. A novel method was developed to detect plastic debris larger than 0.5 mm, which integrated an extraction method with low organic loss and plastic damage alongside a classification method for fused images. This extraction method broadened the size range of the remaining plastic debris, while the fusion solved the low spatial resolution of hyperspectral images and the absence of spectral information in red-green-blue (RGB) images. This method was validated for plastic debris in digestate, compost, and sludge, with extraction demonstrating 100% recovery rates for all samples. After fusion, the spatial resolution of hyperspectral images was improved about five times. Classification recall for the fused hyperspectral images achieved 97 ± 8%, surpassing 83 ± 29% of the raw images. Application of this method to solid digestate detected 1030 ± 212 items/kg of plastic debris, comparable with the conventional Fourier transform infrared spectroscopic result of 1100 ± 436 items/kg. This developed method can investigate plastic debris in complex matrices, simultaneously addressing a wide range of sizes and types. This capability helps acquire reliable data to predict secondary microplastic generation and conduct a risk assessment.

How many microplastics do you need to (sub)sample?

Analysis of microplastics in the environment requires polymer characterization as a confirmation step for suspected microplastic particles found in a sample. Material characterization is costly and can take a long time per particle. When microplastic particle counts are high, many researchers cannot characterize every particle in their sample due to time or monetary constraints. Moreover, characterizing every particle in samples with high plastic particle counts is unnecessary for describing the sample properties. We propose an a priori approach to determine the number of suspected microplastic particles in a sample that should be randomly subsampled for characterization to accurately assess the polymer distribution in the environmental sample. The proposed equation is well-founded in statistics literature and was validated using published microplastic data and simulations for typical microplastic subsampling routines. We report values from the whole equation but also derive a simple way to calculate the necessary particle count for samples or subsamples by taking the error to the power of negative two. Assuming an error of 0.05 (5 %) with a confidence interval of 95 %, an unknown expected proportion, and a sample with many particles (> 100k), the minimum number of particles in a subsample should be 386 particles to accurately characterize the polymer distribution of the sample, given the particles are randomly characterized from the full population of suspected particles. Extending this equation to simultaneously estimate polymer, color, size, and morphology distributions reveals more particles (620) would be needed in the subsample to achieve the same high absolute error threshold for all properties. The above proposal for minimum subsample size also applies to the minimum count that should be present in samples to accurately characterize particle type presence and diversity in a given environmental compartment.

Use of an uncrewed surface vehicle and near infrared hyperspectral imaging for sampling and analysis of aquatic microplastics

Data on MP in aquatic environments have low resolution in space and time. Scaling up sampling and increasing analysis throughput are the main bottlenecks. We combined two approaches: an uncrewed surface vehicle (USV) and near infrared hyperspectral imaging (NIR-HSI) for sampling and analysis of MP > 300 μm. We collected 35 water samples over 4 d in a coastal area. Samples were analyzed using NIR-HSI and Fourier transform infrared spectroscopy (FTIR). Spiked samples were used to determine recovery. We conclude that using a USV can mitigate issues of traditional trawls like scalability, repeatability, and contamination. NIR-HSI detects more polyethylene but less polypropylene than FTIR analysis and reduces analysis time significantly. Highly variable concentrations were found at both sampling locations, with mean MP concentration of 0.28 and 0.01 MP m-3 for location A and B respectively. USV sampling in tandem with NIR-HSI is an effective analytical pipeline for MP monitoring.

Microorganism-mediated biodegradation for effective management and/or removal of micro-plastics from the environment: a comprehensive review

Micro- plastics (MPs) pose significant global threats, requiring an environment-friendly mode of decomposition. Microbial-mediated biodegradation and biodeterioration of micro-plastics (MPs) have been widely known for their cost-effectiveness, and environment-friendly techniques for removing MPs. MPs resistance to various biocidal microbes has also been reported by various studies. The biocidal resistance degree of biodegradability and/or microbiological susceptibility of MPs can be determined by defacement, structural deformation, erosion, degree of plasticizer degradation, metabolization, and/or solubilization of MPs. The degradation of microplastics involves microbial organisms like bacteria, mold, yeast, algae, and associated enzymes. Analytical and microbiological techniques monitor microplastic biodegradation, but no microbial organism can eliminate microplastics. MPs can pose environmental risks to aquatic and human life. Micro-plastic biodegradation involves fragmentation, assimilation, and mineralization, influenced by abiotic and biotic factors. Environmental factors and pre-treatment agents can naturally degrade large polymers or induce bio-fragmentation, which may impact their efficiency. A clear understanding of MPs pollution and the microbial degradation process is crucial for mitigating its effects. The study aimed to identify deteriogenic microorganism species that contribute to the biodegradation of micro-plastics (MPs). This knowledge is crucial for designing novel biodeterioration and biodegradation formulations, both lab-scale and industrial, that exhibit MPs-cidal actions, potentially predicting MPs-free aquatic and atmospheric environments. The study emphasizes the urgent need for global cooperation, research advancements, and public involvement to reduce micro-plastic contamination through policy proposals and improved waste management practices.

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.

Quantification of Polystyrene Uptake by Different Cell Lines Using Fluorescence Microscopy and Label-Free Visualization of Intracellular Polystyrene Particles by Raman Microspectroscopic Imaging

Environmental pollution caused by plastic is a present problem. Polystyrene is a widely used packaging material (e.g., Styrofoam) that can be broken down into microplastics through abrasion. Once the plastic is released into the environment, it is dispersed by wind and atmospheric dust. In this study, we investigated the uptake of polystyrene particles into human cells using A549 cells as a model of the alveolar epithelial barrier, CaCo-2 cells as a model of the intestinal epithelial barrier, and THP-1 cells as a model of immune cells to simulate a possible uptake of microplastics by inhalation, oral uptake, and interaction with the cellular immune system, respectively. The uptake of fluorescence-labeled beads by the different cell types was investigated by confocal laser scanning microscopy in a semi-quantitative, concentration-dependent manner. Additionally, we used Raman spectroscopy as a complementary method for label-free qualitative detection and the visualization of polystyrene within cells. The uptake of polystyrene beads by all investigated cell types was detected, while the uptake behavior of professional phagocytes (THP-1) differed from that of adherent epithelial cells.

COVID lockdown significantly impacted microplastic bulk atmospheric deposition rates

Here, microplastic atmospheric deposition data collected at an urban site during the French national lockdown of spring 2020 is compared to deposition data from the same site in a period of normal activity. Bulk atmospheric deposition was collected on the vegetated roof of a suburban campus from the Greater Paris and analysed for microplastics using a micro-FTIR imaging methodology. Significantly lower deposition rates were measured overall during the lockdown period (median 5.4 MP m-2.d-1) than in a period of normal activity in spring 2021 (median of 29.2 MP m-2.d-1). This difference is however not observed for the smallest microplastic size class. The dominant polymers identified were PP, followed by PE and PS. Precipitation alone could not explain the differences between the two campaigns, and it is suggested that the temporary drop in human activity during lockdown is the primary cause of the reduced deposition rates. This study provides novel insight on the immediate impact of human activities on atmospheric microplastics, thus enhancing the global understanding on this topic.

Generation of macro- and microplastic databases by high-throughput FTIR analysis with microplate readers

FTIR spectral identification is today's gold standard analytical procedure for plastic pollution material characterization. High-throughput FTIR techniques have been advanced for small microplastics (10-500 µm) but less so for large microplastics (500-5 mm) and macroplastics (> 5 mm). These larger plastics are typically analyzed using ATR, which is highly manual and can sometimes destroy particles of interest. Furthermore, spectral libraries are often inadequate due to the limited variety of reference materials and spectral collection modes, resulting from expensive spectral data collection. We advance a new high-throughput technique to remedy these problems using FTIR microplate readers for measuring large particles (> 500 µm). We created a new reference database of over 6000 spectra for transmission, ATR, and reflection spectral collection modes with over 600 plastic, organic, and mineral reference materials relevant to plastic pollution research. We also streamline future analysis in microplate readers by creating a new particle holder for transmission measurements using off-the-shelf parts and fabricating a nonplastic 96-well microplate for storing particles. We determined that particles should be presented to microplate readers as thin as possible due to thick particles causing poor-quality spectra and identifications. We validated the new database using Open Specy and demonstrated that additional transmission and reflection spectra reference data were needed in spectral libraries.

Microplastic pollution on historic facades: Hidden 'sink' or urban threat?

Despite the increasing concerns surrounding the health and environmental risks of microplastics (MPs), the research focus has primarily been on their prevalence in air and the oceans, consequently neglecting their presence on urban facades, which are integral to our everyday environments. Therefore, there is a crucial knowledge gap in comprehending urban MP pollution. Our pioneering interdisciplinary study not only quantifies but also identifies MPs on historic facades, revealing their pervasive presence in a medium-sized urban area in the UK. In this case study, we estimated a mean density of 975,000 fibres/m^2 (0.10 fibres/mm^2) for fibre lengths between 30 and 1000 μm with a ratio of 1:5 for natural to artificial fibres. Our research identifies three groups of fibre length frequencies across varied exposure scenarios on the investigated urban facade. Sheltered areas (4m height) show a high prevalence of 60-120 μm and 180-240 μm fibres. In contrast, less sheltered areas at 3m exhibit lower fibre frequencies but similar lengths. Notably, the lowest area (2-1.5m) features longer fibres (300-1000 μm), while adjacent area S, near a faulty gutter, shows no fibres, highlighting the impact of exposure, altitude, and environmental variables on fibre distribution on urban facades. Our findings pave one of many necessary paths forward to determine the long-term fate of these fibres and provoke a pertinent question: do historic facades serve as an urban 'sink' that mitigates potentially adverse health impacts or amplifies the effects of mobile microplastics? Addressing MP pollution in urban areas is crucial for public health and sustainable cities. More research is required to understand the multi-scale factors behind MP pollution in large cities and to find mitigation strategies, paving the way for effective interventions and policies against this growing threat.

Recognition and detection technology for microplastic, its source and health effects

Microplastic (MP) is ubiquitous in the environment which appeared as an immense intimidation to human and animal health. The plastic fragments significantly polluted the ocean, fresh water, food chain, and other food items. Inadequate maintenance, less knowledge of adverse influence along with inappropriate usage in addition throwing away of plastics items revolves present planet in to plastics planet. The present study aims to focus on the recognition and advance detection technologies for MPs and the adverse effects of micro- and nanoplastics on human health. MPs have rigorous adverse effect on human health that leads to condensed growth rates, lessened reproductive capability, ulcer, scrape, and oxidative nervous anxiety, in addition, also disturb circulatory and respiratory mechanism. The detection of MP particles has also placed emphasis on identification technologies such as scanning electron microscopy, Raman spectroscopy, optical detection, Fourier transform infrared spectroscopy, thermo-analytical techniques, flow cytometry, holography, and hyperspectral imaging. It suggests that further research should be explored to understand the source, distribution, and health impacts and evaluate numerous detection methodologies for the MPs along with purification techniques.

Microplastics in Ecuador: A review of environmental and health-risk assessment challenges

Pollution from plastic debris and microplastics (MPs) is a worldwide issue. Classified as emerging contaminants, MPs have become widespread and have been found not only in terrestrial and aquatic ecosystems but also within the food chain, which affects both the environment and human health. Since the outbreak of COVID-19, the consumption of single-use plastics has drastically increased, intensifying mismanaged plastic waste in countries such as Ecuador. Therefore, the aim of this review is to 1) summarize the state of MP-related knowledge, focusing on studies conducted with environmental matrices, biota, and food, and 2) analyze the efforts by different national authorities and entities in Ecuador to control MP contamination. Results showed a limited number of studies have been done in Ecuador, which have mainly focused on the surface water of coastal areas, followed by studies on sediment and food. MPs were identified in all samples, indicating the lack of wastewater management policies, deficient management of solid wastes, and the contribution of anthropogenic activities such as artisanal fishing and aquaculture to water ecosystem pollution, which affects food webs. Moreover, studies have shown that food contamination can occur through atmospheric deposition of MPs; however, ingredients and inputs from food production, processing, and packaging, as well as food containers, contribute to MP occurrence in food. Further research is needed to develop more sensitive, precise, and reliable detection methods and assess MPs' impact on terrestrial and aquatic ecosystems, biota, and human health. In Ecuador specifically, implementing wastewater treatment plants in major cities, continuously monitoring MP coastal contamination, and establishing environmental and food safety regulations are crucial. Additionally, national authorities need to develop programs to raise public awareness of plastic use and its environmental effects, as well as MP exposure's effects on human health.

Retention of microplastics and tyre wear particles in stormwater ponds

Stormwater runoff from urban areas contain a wide variety of pollutants which is typically managed using stormwater retention ponds. However, their performance with regards to emerging pollutants such as microplastics and tyre wear material remains unclear. In this study, samples of effluent water and sediments from four stormwater retention ponds were analysed for their content of microplastics and tyre wear material. Microplastics were analysed using state-of-the-art hyperspectral imaging technique while tyre wear material was analysed using pyrolysis-GC-MS. Microplastics were recovered in all samples and the mass balance revealed that on average 88% of small microplastics (<500 µm) were retain in the ponds while the removal efficiency for large microplastics (>500 µm) was 95%. Tyre wear material was identified in all sediment samples but found below the detection limit in three out of four effluent samples. On average 95% of the tyre wear material was removed by the retention ponds. The results from this study show that stormwater retention ponds are very effective in removing microplastics as well as tyre wear material from stormwater runoff.

What is hiding below the surface - MPs including TWP in an urban lake

Inland lakes play an important role as habitats for local species and are often essential drinking water reservoirs. However, there is limited information about the presence of microplastics (MPs) in these water bodies. Thirteen sediment samples were collected across a Danish urban lake to map MPs, including tyre wear particles (TWP). The lower size detection limit was 10 µm. MPs were quantified as counts, size, and polymer type by Fourier-transform infrared microspectroscopy (µFTIR) and mass estimated from the 2D projections of the MPs. As TWP cannot be determined by µFTIR, counts and sizes could not be quantified by this technique. Instead, TWP mass was determined by pyrolysis gas chromatography mass spectrometry (Py-GC/MS). The average MP abundance was 279 mg kg-1 (µFTIR), of which 19 mg kg-1 (Py-GC/MS) were TWP. For MPs other than tyre wear, the average MP count concentration was 11,312 counts kg-1. Urban runoff from combined sewer overflows and separate stormwater outlets combined with outflow from a wastewater treatment plant were potential point sources. The spatial variation was substantial, with concentrations varying several orders of magnitude. There was no pattern in concentration across the lake, and the distribution of high and low values seemed random. This indicates that large sampling campaigns encompassing the entire lake are key to an accurate quantification. No preferential spatial trend in polymer characteristics was identified. For MPs other than TWP, the size of buoyant and non-buoyant polymers showed no significant difference across the lake, suggesting that the same processes brought them to the sediment, regardless of their density. Moreover, MP abundance was not correlated to sediment properties, further indicating a random occurrence of MPs in the lake sediments. These findings shed light on the occurrence and distribution of MPs, including TWP, in an inland lake, improving the basis for making mitigation decisions.

Does microplastic analysis method affect our understanding of microplastics in the environment?

Two analytical methods - both in active use at different laboratories - were tested and compared against each other to investigate how the procedure influences microplastic (MP) detection with micro Fourier Transform Infrared Spectroscopy (μFTIR) imaging. A representative composite water sample collected from the Danube River was divided into 12 subsamples, and processed following two different methods, which differed in MP isolation procedures, the optical substrate utilized for the chemical imaging, and the detection limit of the spectroscopic instruments. The first instrument had a nominal pixel resolution of 5.5 μm, while the second had a nominal resolution of 25 μm. These two methods led to different MP abundance, MP mass estimates, but not MP characteristics. Only looking at MPs > 50 μm, the first method showed a higher MP abundance, namely 418-2571 MP m-3 with MP mass estimates of 703-1900 μg m-3, while the second method yielded 16.7-72.1 MP m-3 with mass estimates of 222-439 μg m-3. Looking deeper into the steps of the methods showed that the MP isolation procedure contributed slightly to the difference in the result. However, the variability between individual samples was larger than the difference caused by the methods. Somewhat sample-dependent, the use of two different substrates (zinc selenide windows versus Anodisc filters) caused a substantial difference between results. This was due to a higher tendency for particles to agglomerate on the Anodisc filters, and an 'IR-halo' around particles on ZnSe windows when scanning with μFTIR. Finally, the μFTIR settings and nominal resolution caused significant differences in identifying MP size and mass estimate, which showed that the smaller the pixel size, the more accurately the particle boundary can be defined. These findings contributed to explaining disagreements between studies and addressed the importance of harmonization of methods.

Analysis of micro- and nanoplastics in wastewater treatment plants: key steps and environmental risk considerations

The analysis of micro- and nanoplastics (MNPs) in the environment is a critical objective due to their ubiquitous presence in natural habitats, as well as their occurrence in various food, beverage, and organism matrices. MNPs pose significant concerns due to their direct toxicological effects and their potential to serve as carriers for hazardous organic/inorganic contaminants and pathogens, thereby posing risks to both human health and ecosystem integrity. Understanding the fate of MNPs within wastewater treatment plants (WWTPs) holds paramount importance, as these facilities can be significant sources of MNP emissions. Additionally, during wastewater purification processes, MNPs can accumulate contaminants and pathogens, potentially transferring them into receiving water bodies. Hence, establishing a robust analytical framework encompassing sampling, extraction, and instrumental analysis is indispensable for monitoring MNP pollution and assessing associated risks. This comprehensive review critically evaluates the strengths and limitations of commonly employed methods for studying MNPs in wastewater, sludge, and analogous environmental samples. Furthermore, this paper proposes potential solutions to address identified methodological shortcomings. Lastly, a dedicated section investigates the association of plastic particles with chemicals and pathogens, alongside the analytical techniques employed to study such interactions. The insights generated from this work can be valuable reference material for both the scientific research community and environmental monitoring and management authorities.

Leveraging deep learning for automatic recognition of microplastics (MPs) via focal plane array (FPA) micro-FT-IR imaging

The fast and accurate identification of MPs in environmental samples is essential for the understanding of the fate and transport of MPs in ecosystems. The recognition of MPs in environmental samples by spectral classification using conventional library search routines can be challenging due to the presence of additives, surface modification, and adsorbed contaminants. Further, the thickness of MPs also impacts the shape of spectra when FTIR spectra are collected in transmission mode. To overcome these challenges, PlasticNet, a deep learning convolutional neural network architecture, was developed for enhanced MP recognition. Once trained with 8000 + spectra of virgin plastic, PlasticNet successfully classified 11 types of common plastic with accuracy higher than 95%. The errors in identification as indicated by a confusion matrix were found to be caused by edge effects, molecular similarity of plastics, and the contamination of standards. When PlasticNet was trained with spectra of virgin plastic it showed good performance (92%+) in recognizing spectra that had increased complexity due to the presence of additives and weathering. The re-training of PlasticNet with more complex spectra further enhanced the model's capability to recognize complex spectra. PlasticNet was also able to successfully identify MPs despite variations in spectra caused by variations in MP thickness. When compared with the performance of the library search in identifying MPs in the same complex dataset collected from an environmental sample, PlasticNet achieved comparable performance in identifying PP MPs, but a 17.3% improvement. PlasticNet has the potential to become a standard approach for rapid and accurate automatic recognition of MPs in environmental samples analyzed by FPA FT-IR imaging.

Sequential quantification of number and mass of microplastics in municipal wastewater using Fourier-transform infrared spectroscopy and pyrolysis gas chromatography-mass spectrometry

Plastic pollution is a significant environmental concern because microplastics (MPs) accumulate in various ecosystems; therefore, the accurate identification and quantification of MPs in environmental samples is crucial. This study presents a new sequential analytical method that combines Fourier-transform infrared spectroscopy (FTIR) and pyrolysis-gas chromatography/mass spectrometry (Pyr-GC/MS) to characterize and quantify MPs. FTIR with a microscope allows the identification of the polymer type and physical dimensions of MPs, whereas Pyr-GC/MS enables determining the chemical composition of MPs with plastic additives. Pretreated wastewater influent samples spiked with reference MPs were filtered through an Al2O3 disk for FTIR analysis, and the surface contents were collected and subjected to Pyr-GC/MS analysis. The mass of the reference MPs estimated using FTIR were in good agreement but were slightly lower than those obtained using Pyr-GC/MS. This finding supports the notion that the proposed sequential method can be used to determine both the number and the mass of MPs in environmental samples.

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.

A novel enzymatic method for isolation of plastic particles from human blood

Microplastic particles have been detected in the human body. This study aimed to develop a blood digestion method that preserves microplastics during analysis. Acidic and alkaline reagents, commonly used for isolating plastic particles from organic materials, were tested on human blood samples and microplastics. Nitric acid, hydrochloric acid, potassium hydroxide, and sodium hydroxide were examined over time. Additionally, a pepsin-pancreatin combination was utilized for blood digestion. Light microscopy assessed digestion efficiency and particle count changes, while Raman microspectroscopy distinguished between plastic and cell debris. The acidic reagents were ineffective in removing the organic material, while alkaline reagents were effective without significant effects on microplastics. Blood digestion using pepsin and pancreatin demonstrated efficient digestion without negative consequences for the particles. While potassium hydroxide digestion is already established, novel use of the pepsin-pancreatin combination was introduced to digest human blood, indicating its potential for isolating plastic particles from tissue and human food.

Microplastic ingestion and its effects οn sea urchin Paracentrotus lividus: A field study in a coastal East Mediterranean environment

Microplastics (MPs) are recognized as an increasing threat to the marine environment, but little is known about their effects on benthic organisms, including sea urchins, when ingested. For this purpose, wild sea urchins (P. lividus) and seafloor sediment samples were investigated across three coastal areas of Zakynthos Island (Ionian Sea), each exposed to different anthropogenic pressures, revealing a consistent pattern in MP abundance, shape, and color. Biomarkers related to oxidative stress, neurotoxicity, and genotoxicity showed no significant effects of MP ingestion in the sea urchins, except for a positive correlation between GST activity and ingested MPs, suggesting a possible activation of their detoxification system in response to MP ingestion. While MP concentrations in sea urchins and sediments were within the low range reported in the global literature, it remains crucial to conduct further investigations in areas with MP pollution approaching predicted levels to fully comprehend the potential effects of MP pollution on marine organisms.

Assessment of microplastic contamination in the Loire River (France) throughout analysis of different biotic and abiotic freshwater matrices

The contamination of microplastics (MP) in freshwater environments represent a major way for the MP transport in the environment. The assessment of MP pollution in freshwater compartments is then important to visualize the pressure and the impacts on medium, and to set up necessary measures. In this context, this study focused on the influence of anthropogenic activities of a medium French city (Angers) on MP levels in samples collected from the Loire River, the longest river in France. Abiotic and biotic matrices were collected upstream and downstream Angers. A first analysis was performed based on microscopy to determine the size, colour and shape of suspected MP and a complementary analysis by μ-FTIR (micro-Fourier Transform InfraRed) was conducted to determine the composition of plastic particles. Three organisms belonging to different trophic levels were studied: when the MP level was expressed per individual, the lowest abundance of MP was found in Tubifex sp. Followed by Corbicula fluminea, while the highest was measured in Anguilla anguilla. To establish the relationship with their habitat, the presence of MP in sediment and water was also analysed. Therefore, this works constitutes a complete overview of the MP levels in freshwater abiotic and biotic matrices. Overall, the presence of MP in analysed samples did not follow a particular pattern, neither in the sites nor matrices: the characteristics depending on a multifactorial outcome (feeding mode, organism size …). However, correlation of MP pattern between clams and sediment was quite evident, while the one between worms and their habitat was not. This demonstrates the relevance of investigating plastic contamination both in biotic and abiotic matrices. Finally, a standardisation of sampling and analytical analysis protocols would be helpful to make comparisons between studies more robust.

Structural Identification and Observation of Dose Rate-Dependent Beam-Induced Structural Changes of Micro- and Nanoplastic Particles by Pair Distribution Function Analysis in the Transmission Electron Microscope (ePDF)

Micro- and nanoplastics (MNPs) are considered a possible threat to microorganisms in the aquatic environment. Here, we show that total scattering intensity analysis of electron diffraction (ED) data measured by transmission electron microscopy, which yields the electron pair distribution function (ePDF), is a feasible method for the characterization and identification of MNPs down to 100 nm. To demonstrate the applicability, cryo ball-milled powders of the most common polymers [i.e., polyethylene , polypropylene, polyethylene terephthalate, and polyamide] and nano-sized polystyrene and silica spheres were used as model systems. The comparison of the experimentally determined reduced pair density functions (RDFs) with model RDFs derived from crystallographic data of the respective polymers allows the distinction of the different types of polymers. Furthermore, carbon-based polymers are highly beam-sensitive materials. The degradation of the samples under the electron beam was analyzed by conducting time-resolved ED measurements. Changes in the material can be visualized by the RDF analysis of the time-series of ED patterns, and information about the materials in question can be gained by this beam damage analysis. Prospectively, ePDF analytics will help to understand and study more precisely the input of MNPs into the environment.

Adding Depth to Microplastics

The effects and risks of microplastics correlate with three-dimensional (3D) properties, such as the volume and surface area of the biologically accessible fraction of the diverse particle mixtures as they occur in nature. However, these 3D parameters are difficult to estimate because measurement methods for spectroscopic and visible light image analysis yield data in only two dimensions (2D). The best-existing 2D to 3D conversion models require calibration for each new set of particles, which is labor-intensive. Here we introduce a new model that does not require calibration and compare its performance with existing models, including calibration-based ones. For the evaluation, we developed a new method in which the volumes of environmentally relevant microplastic mixtures are estimated in one go instead of on a cumbersome particle-by-particle basis. With this, the new Barchiesi model can be seen as the most universal. The new model can be implemented in software used for the analysis of infrared spectroscopy and visual light image analysis data and is expected to increase the accuracy of risk assessments based on particle volumes and surface areas as toxicologically relevant metrics.

Testing of Different Digestion Solutions on Tissue Samples and the Effects of Used Potassium Hydroxide Solution on Polystyrene Microspheres

Microplastic particles are ubiquitous in our environment, having entered the air, the water, the soil, and ultimately our food chain. Owing to their small size, these particles can potentially enter the bloodstream and accumulate in the organs. To detect microplastics using existing methods, they must first be isolated. The aim of this study was to develop a non-destructive method for efficiently and affordably isolating plastic particles. We investigated the digestion of kidney, lung, liver, and brain samples from pigs. Kidney samples were analyzed using light microscopy after incubation with proteinase K, pepsin/pancreatin, and 10% potassium hydroxide (KOH) solution. Various KOH:tissue ratios were employed for the digestion of lung, liver, and brain samples. Additionally, we examined the effect of 10% KOH solution on added polystyrene microplastics using scanning electron microscopy. Our findings revealed that a 10% KOH solution is the most suitable for dissolving diverse organ samples, while enzymatic methods require further refinement. Moreover, we demonstrated that commonly used 1 µm polystyrene particles remain unaffected by 10% KOH solution even after 76 h of incubation. Digestion by KOH offers a simple and cost-effective approach for processing organ samples and holds potential for isolating plastic particles from meat products.

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.

Is Zooplankton an Entry Point of Microplastics into the Marine Food Web?

Microplastics (MPs) overlap in size with phytoplankton and can be ingested by zooplankton, transferring them to higher trophic levels. Copepods are the most abundant metazoans among zooplankton and the main link between primary producers and higher trophic levels. Ingestion of MPs has been investigated in the laboratory, but we still know little about the ingestion of MPs by zooplankton in the natural environment. In this study, we determined the concentration and characteristics of MPs down to 10 μm in zooplankton samples, sorted calanoid copepods, and fecal pellets collected in the Kattegat/Skagerrak Sea (Denmark). We found a median concentration of 1.7 × 10-3 MPs ind-1 in the zooplankton samples, 2.9 × 10-3 MPs ind-1 in the sorted-copepods, and 3 × 10-3 MPs per fecal pellet. Most MPs in the zooplankton samples and fecal pellets were fragments smaller than 100 μm, whereas fibers dominated in the sorted copepods. Based on the collected data, we estimated a MP budget for the surface layer (0-18 m), where copepods contained only 3% of the MPs in the water, while 5% of the MPs were packed in fecal pellets. However, the number of MPs exported daily to the pycnocline via fecal pellets was estimated to be 1.4% of the total MPs in the surface layer. Our results indicate that zooplankton are an entry point of small MPs in the food web, but the number of MPs in zooplankton and their fecal pellets was low compared with the number of MPs found in the water column and the occurrence and/or ingestion of MPs reported for nekton. This suggests a low risk of MP transferring to higher trophic levels through zooplankton and a quantitatively low, but ecologically relevant, contribution of fecal pellets to the vertical exportation of MPs in the ocean.

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.

Variability of microplastic loading and retention in four inland lakes in Minnesota, USA

Microplastic pollution (plastic particles < 5 mm) has potentially harmful impacts on aquatic ecosystems. Understanding the factors that impact microplastic loading and distribution within aquatic ecosystems is crucial for assessing potential threats from microplastics. Here we examine the extent of microplastic pollution in the surface waters and sediments of four small inland lakes in Minnesota, USA that represent a range of human impacts as well as a variety of watershed and lake characteristics. Surface water particulates and benthic sediments were collected in the summers of 2019 and 2020 to examine the loading of microplastics into these lakes and their distribution throughout the ecosystems. Lower size cut offs were set at 330 μm for surface water particulate samples and 250 μm for sediment samples. Watershed to surface area ratio (WS:SA) and urban development were the most influential factors on microplastic loading. Surface water microplastic concentrations ranged from 27,000 microplastics km^-2 in Elk Lake (small WS:SA and minimally developed) to 152,000 microplastics km^-2 in White Iron Lake (large WS:SA and low development). Concentrations in benthic sediments ranged from 30 microplastics kg^-1 dry sediment in White Iron Lake (forested watershed) to 270 microplastics kg^-1 dry sediment in Peltier Lake (urbanized watershed) and were not directly correlated to surface water concentrations. Results from this study highlight the characteristics of small lakes that influence spatial and temporal variability in microplastic loading, retention, and deposition of microplastics to sediments. Further, this study demonstrates the difficulties of accurately predicting microplastic loading and the importance of comprehensive sampling to account for the variability of microplastic loading and distribution in smaller inland lakes.

Co-occurrence of macroplastics, microplastics, and legacy and emerging plasticisers in UK soils

Despite a theoretical link between plastic and plasticiser occurrence in the terrestrial environment, there are few empirical studies of the relationship between these contaminants in soils. We carried out a field study to assess the co-occurrence of plastic waste, and legacy and emerging plasticisers in UK soils (n = 19) from various land uses (woodlands, urban roadsides, urban parklands, landfill-associated). Surface plastics and soil microplastics were quantified and characterised using ATR-FTIR and μ-FTIR. Eight legacy (phthalate) and three emerging (adipate, citrate, trimellitate) plasticisers were quantified using GC-MS. Surface plastics were found at higher prevalence at landfill-associated and urban roadside sites, with levels significantly (2 orders of magnitude) greater than in woodlands. Microplastics were detected in landfill-associated (mean 12.3 particles g^-1 dw), urban roadside (17.3 particles g^-1 dw) and urban parkland (15.7 particles g^-1 dw) soils, but not in woodland soils. The most commonly detected polymers were polyethene, polypropene and polystyrene. Mean ∑plasticiser concentration in urban roadside soils (3111 ng g^-1 dw) was significantly higher than in woodlands (134 ng g^-1 dw). No significant difference was found between landfill-associated (318 ng g^-1 dw) and urban parkland (193 ng g^-1 dw) soils and woodlands. Di-n-butyl phthalate (94.7% detection frequency) and the emerging plasticiser trioctyl trimellitate (89.5%) were the most commonly detected plasticisers, with diethylhexyl phthalate (493 ng g^-1 dw) and di-iso-decyl phthalate (96.7 ng g^-1 dw) present at the highest concentrations. ∑plasticiser concentrations were significantly correlated with surface plastic (R² = 0.23), but not with soil microplastic concentrations. Whilst plastic litter seems a fundamental source of plasticisers in soils, mechanisms such as airborne transport from source areas may be as important. Based on the data from this study, phthalates remain the dominant plasticisers in soils, but emerging plasticisers are already widespread, as reflected by their presence in all land uses studied.

Occurrence and backtracking of microplastic mass loads including tire wear particles in northern Atlantic air

Few studies report the occurrence of microplastics (MP), including tire wear particles (TWP) in the marine atmosphere, and little data is available regarding their size or sources. Here we present active air sampling devices (low- and high-volume samplers) for the evaluation of composition and MP mass loads in the marine atmosphere. Air was sampled during a research cruise along the Norwegian coast up to Bear Island. Samples were analyzed with pyrolysis-gas chromatography-mass spectrometry, generating a mass-based data set for MP in the marine atmosphere. Here we show the ubiquity of MP, even in remote Arctic areas with concentrations up to 37.5 ng m^-3. Cluster of polyethylene terephthalate (max. 1.5 ng m^-3) were universally present. TWP (max. 35 ng m^-3) and cluster of polystyrene, polypropylene, and polyurethane (max. 1.1 ng m^-3) were also detected. Atmospheric transport and dispersion models, suggested the introduction of MP into the marine atmosphere equally from sea- and land-based emissions, transforming the ocean from a sink into a source for MP.

Developing and testing a workflow to identify microplastics using near infrared hyperspectral imaging

The analysis of microplastics (MP) is time-consuming which limits our capacity to monitor and mitigate plastic pollution. Here, near infrared (1000-2500 nm) hyperspectral imaging (NIR-HSI) offers an advantage over other spectroscopic techniques because it can rapidly image large areas relative to other systems. While NIR-HSI can successfully detect MP, accuracy and limitations of the method have not been fully explored. In addition, lack of open databases and analysis pipelines increases the barrier to use. In this work, we developed a spectral database containing preproduction pellets, consumer products and marine plastic debris, imaged using a Hyspex SWIR-320me imager. A SIMCA model identified four polymer types: polypropylene, polyethylene, polyethylene terephthalate and polystyrene (PP, PE, PET, PS) to identify MP in hyperspectral images. We determined the accuracy of size estimates for PS MP > 1000 μm using fluorescence microscopy and tested the impact of photooxidation on detection of plastics by NIR-HSI (PE, PP, PS, PET) and subsequent prediction by the SIMCA model. The model performed well across all polymers as shown by high specificity, sensitivity, and accuracy for internal cross validation (>88%), and sensitivity >80% for external validation. PS MP < 500 μm Feret diameter were not consistently detected by NIR-HSI when compared with fluorescence microscopy. However, estimates for Feret diameter were consistent for PS MP > 1000 μm. Analysis by NIR-HSI showed no spectral changes and SIMCA showed no decreased precision with increased photooxidation across polymer types. Recall varied across polymer type and photooxidation stage with no clear trends. This study shows that NIR-HSI is a rapid method which can accurately identify MP of the four most relevant polymer types, precluding the need to analyze particles one at a time. NIR-HSI can be a key technology for environmental monitoring of plastic debris where rapid analysis of multiple samples is required.

Riverine Microplastic Pollution: Insights from Cagayan de Oro River, Philippines

Rivers are vital water sources for humans and homes for aquatic organisms. Conversely, they are well known as the route of plastics into the ocean. Despite being the world's number one emitter of riverine plastics into the ocean, microplastics (MPs), or plastic particles less than 5 mm, in the Philippines' rivers are relatively unexplored. Water samples were collected from six sampling stations along the river channel of the Cagayan de Oro River, one of the largest rivers in Northern Mindanao, Philippines. The extracted microplastics' abundance, distribution, and characteristics were analyzed using a stereomicroscope and Fourier transform infrared spectroscopy (FTIR). The results showed a mean concentration of 300 items/m³ of MPs dominated by blue-colored (59%), fiber (63%), 0.3-0.5 mm (44%), and polyacetylene (48%) particles. The highest concentration of microplastics was recorded near the mouth of the river, and the lowest was in the middle area. The findings indicated a significant difference in MP concentration at the sampling stations. This study is the first assessment of microplastic in a river in Mindanao. The results of this study will aid in formulating mitigation strategies for reducing riverine plastic emissions.

High-Content Screening Discovers Microplastics Released by Contact Lenses under Sunlight

The widespread use of plastic products leads to the ubiquity of microplastics in daily life, while the release of microplastics from long-used contact lenses has not been reported due to the limitations of conventional detection methods. Here, we established a new and rapid method to capture and count microplastics by using a high-content screening system. This method can simultaneously measure the diameter, area, and shape of each plastic particle, and the reliability and applicability of this method were verified with commercial microplastics. It is estimated that 90,698 particles of microplastics could be released from a pair of contact lenses during a year of wearing. The microplastics in the leachates were confirmed to be released from the contact lenses by scanning electron microscopy and Fourier transform infrared spectroscopy fingerprint analysis. Our study reveals an undiscovered pathway of microplastic direct exposure to humans, highlighting the urgent need to assess the potential health risks caused by eye exposure to microplastics.

First insight into microplastic groundwater pollution in Latin America: the case of a coastal aquifer in Northwest Mexico

Microplastics have been studied on biota and other environmental domains, such as soils. Despite the importance of groundwater as a resource for millions of people worldwide as drinking water and personal hygiene, domestic, agricultural, mining, and industrial purposes, there are very few studies concerning microplastics in this domain around the world. We present the first study in Latin America addressing this topic. Six capped boreholes were analyzed in terms of abundance, concentration, and chemical characterization, at three different depths, from a coastal aquifer in Northwest Mexico. This aquifer is highly permeable and affected by anthropogenic activities. A total of 330 microplastics were found in the eighteen samples. In terms of concentration, the interval ranged from 10 to 34 particles/L, with an average of 18.3 particles/L. Four synthetic polymers were identified: isotactic polypropylene (iPP), hydroxyethylcellulose (HEC), carboxylated polyvinyl chloride (PVC), and low-density polyethylene (LDPE); with iPP being the most abundant (55.8%) in each borehole. Agriculture activities and septic outflows are considered the potential regional sources of these contaminants into the aquifer. Three possible transport pathways to the aquifer are suggested: (1) marine intrusion, (2) marsh intrusion, and (3) infiltration through the soil. More research about the occurrence, concentration, and distribution of the different kinds of microplastics in groundwater is needed to have a better understanding of the behavior and health risks to organisms, including human beings.

Random forest microplastic classification using spectral subsamples of FT-IR hyperspectral images

In this work, a random decision forest model is built for fast identification of Fourier-transform infrared spectra of the eleven most common types of microplastics in the environment. The random decision forest input data is reduced to a combination of highly discriminative single wavenumbers selected using a machine learning classifier. This dimension reduction allows input from systems with individual wavenumber measurements, and decreases prediction time. The training and testing spectra are extracted from Fourier-transform infrared hyperspectral images of pure-type microplastic samples, automatizing the process with reference spectra and a fast background correction and identification algorithm. Random decision forest classification results are validated using procedurally generated ground truth. The classification accuracy achieved on said ground truths are not expected to carry over to environmental samples as those usually contain a broader variety of materials.

Comparative evaluation of filtration and imaging properties of analytical filters for microplastic capture and analysis

Pollution by microplastics (MPs) is a growing problem that is now well-recognized, as concerning levels of MPs have been found in drinking water, food, and even human tissues. Given the evolving understanding of their toxicological effects on human health, MPs are an area of concern requiring further study. Consequently, there is a need for greater understanding of the performance characteristics of common MP analytical methods and where possible, for standardizing methods and reporting practices. Here, we report our work comparing filtration and imaging properties of five analytical filters suitable for MP capture and analysis. We compared track-etched polycarbonate with (PCTEG) and without gold coating (PCTE), polytetrafluoroethylene (PTFE), porous silicon (PSi), and gold-coated microslit silicon nitride membranes (MSSN-Au). Four of the filter types had a nominal 1.0 μm cut-off, except for PCTEG which had a 0.8 nominal cut-off. We examined the ultrastructure of each membrane type by electron microscopy to understand how their physical properties influence filtration and imaging performance. We compared clean water filtration rates and timed volume passage for each filter in comparison to its porosity and working surface area. We further compared optical microscopy imaging properties for each filter with model MP samples in both bright-field and fluorescent modes with accompanying Nile Red staining. In terms of absolute and surface area-normalized flow rates, our measurements ranked the filters in order of MSSN-Au > PTFE > PCTE > PCTEG > PSi. Similarly, we found MSSN-Au filters compared favorably in terms of optical microscopy performance. Collectively, these data will aid practitioners when choosing analytical filters for MP surveillance and testing.

Finding the Balance between Research and Monitoring: When Are Methods Good Enough to Understand Plastic Pollution?

Plastic pollution is an international environmental problem. Desire to act is shared from the public to policymakers, yet motivation and approaches are diverging. Public attention is directed to reducing plastic consumption, cleaning local environments, and engaging in citizen science initiatives. Policymakers and regulators are working on prevention and mitigation measures, while international, regional, and national bodies are defining monitoring recommendations. Research activities are focused on validating approaches to address goals and comparing methods. Policy and regulation are eager to act on plastic pollution, often asking questions researchers cannot answer with available methods. The purpose of monitoring will define which method is implemented. A clear and open dialogue between all actors is essential to facilitate communication on what is feasible with current methods, further research, and development needs. For example, some methods can already be used for international monitoring, yet limitations including target plastic types and sizes, sampling strategy, available infrastructure and analytical capacity, and harmonization of generated data remain. Time and resources to advance scientific understanding must be balanced against the need to answer pressing policy issues.

Previous successes and untapped potential of pyrolysis-GC/MS for the analysis of plastic pollution

There is growing concern from scientists, policy makers, and the public about the contamination of natural and indoor environments with plastics, particularly micro/nanoplastics. Typically, characterizing microplastics in environmental samples requires extensive sample processing to isolate particles, followed by spectroscopic methodologies to identify particle polymer composition. Spectroscopic techniques are limited in their ability to provide polymer mass or advanced chemical composition (e.g., chemical additive content), which are important for toxicological assessments. To achieve mass fraction quantification and chemical characterization of plastics in environmental samples, many researchers have turned to thermoanalytical spectrometric approaches, particularly pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Sample preparation for Py-GC/MS may be approached similarly to techniques needed for spectroscopic approaches (e.g., isolate particles on a filter), employ pressurized solvent extraction, or use ultrafiltration techniques to concentrate nanoplastics. Great strides have been made in using calibration curves to quantify plastics in complex matrices. However, the approaches to the pyrolysis thermal program, as well as calibrant and sample preparation, are inconsistent, requiring refinement and harmonization. This review provides a critical synthesis of previous Py-GC/MS work and highlights opportunities for novel and improved Py-GC/MS analysis of plastics in the future.

Innovative reference materials for method validation in microplastic analysis including interlaboratory comparison exercises

Reference materials (RMs) are vital tools in the validation of methods used to detect environmental pollutants. Microplastics, a relatively new environmental pollutant, require a variety of complex approaches to address their presence in environmental samples. Both interlaboratory comparison (ILC) studies and RMs are essential to support the validation of methods used in microplastic analysis. Presented here are results of quality assurance and quality control (QA/QC) performed on two types of candidate microplastic RMs: dissolvable gelatin capsules and soda tablets. These RMs have been used to support numerous international ILC studies in recent years (2019-2022). Dissolvable capsules containing polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyethylene (PE), and polystyrene (PS), in different size fractions from 50 to 1000 µm, were produced for one ILC study, obtaining relative standard deviation (RSD) from 0 to 24%. The larger size fraction allowed for manual addition of particles to the capsules, yielding 0% error and 100% recovery during QA/QC. Dissolvable capsules were replaced by soda tablets in subsequent ILC studies and recovery test exercises because they were found to be a more reliable carrier for microplastic RMs. Batches of soda tablets were produced containing different single and multiple polymer mixtures, i.e., PE, PET, PS, PVC, polypropylene (PP), and polycarbonate (PC), with RSD ranging from 8 to 21%. Lastly, soda tablets consisting of a mixture of PE, PVC, and PS (125-355 µm) were produced and used for recovery testing during pretreatment of environmental samples. These had an RSD of 9%. Results showed that soda tablets and capsules containing microplastics >50 µm could be produced with sufficient precision for internal recovery tests and external ILC studies. Further work is required to optimize this method for smaller microplastics (< 50 µm) because variation was found to be too large during QA/QC. Nevertheless, this approach represents a valuable solution addressing many of the challenges associated with validating microplastic analytical methods.

Comparison of two rapid automated analysis tools for large FTIR microplastic datasets

One of the biggest issues in microplastic (MP, plastic items  <5 mm) research is the lack of standardisation and harmonisation in all fields, reaching from sampling methodology to sample purification, analytical methods and data analysis. This hampers comparability as well as reproducibility among studies. Concerning chemical analysis of MPs, Fourier-transform infrared (FTIR) spectroscocopy is one of the most powerful tools. Here, focal plane array (FPA) based micro-FTIR (µFTIR) imaging allows for rapid measurement and identification without manual preselection of putative MP and therefore enables large sample throughputs with high spatial resolution. The resulting huge datasets necessitate automated algorithms for data analysis in a reasonable time frame. Although solutions are available, little is known about the comparability or the level of reliability of their output. For the first time, within our study, we compare two well-established and frequently applied data analysis algorithms in regard to results in abundance, polymer composition and size distributions of MP (11-500 µm) derived from selected environmental water samples: (a) the siMPle analysis tool (systematic identification of MicroPlastics in the environment) in combination with MPAPP (MicroPlastic Automated Particle/fibre analysis Pipeline) and (b) the BPF (Bayreuth Particle Finder). The results of our comparison show an overall good accordance but also indicate discrepancies concerning certain polymer types/clusters as well as the smallest MP size classes. Our study further demonstrates that a detailed comparison of MP algorithms is an essential prerequisite for a better comparability of MP data.