Analysis of microplastics in drinking water and other clean water samples with micro-Raman and micro-infrared spectroscopy: minimum requirements and best practice guidelines

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.

Smartphone microscopic method for imaging and quantification of microplastics in drinking water

Analysis of microplastics in drinking water is often challenging due to smaller particle size and low particle count. In this study, we used a low cost and an easy to assemble smartphone microscopic system for imaging and quantitating microplastic particles as small as 20 μm. The system consisted of a spherical sapphire ball lens of 4 mm diameter attached to a smartphone camera as a major imaging component. It also involved pre-concentration of the sample using ZnCl2 solution. The spike recovery and limit of detection of the method in filtered distilled and deionized water samples (n = 9) were 55.6% ± 9.7% and 34 particles/L, respectively. Imaging performance of the microscopic system was similar to a commercial bright field microscopic system. The method was further implemented to examine microplastic particles in commercial bottled and jar water samples (n = 20). The particles count in bottled and jar water samples ranged from 0-91 particles/L to 0-130 particles/L, respectively. In both sample types, particles of diverse shape and size were observed. The particles collected from water samples were further confirmed by FTIR spectra (n = 36), which found 97% of the particles tested were made of plastic material. These findings suggested that the smartphone microscopic system can be implemented as a low-cost alternative for preliminary screening of microplastic in drinking water samples. RESEARCH HIGHLIGHTS: Ball lens based smartphone microscopic method was used for microplastic analysis. Particles of diverse shape and size were found in bottle and jar water samples.

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.

Every breath you take: High concentration of breathable microplastics in indoor environments

The widespread presence of microplastics (MPs) in the air and their potential impact on human health underscore the pressing need to develop robust methods for quantifying their presence, particularly in the breathable fraction (<5 μm). In this study, Raman micro-spectroscopy (μRaman) was employed to assess the concentration of indoor airborne MPs >1 μm in four indoor environments (a meeting room, a workshop, and two apartments) under different levels of human activity. The indoor airborne MP concentration spanned between 58 and 684 MPs per cubic meter (MP m-3) (median 212 MP m-3, MPs/non-plastic ratio 0-1.6%), depending not only on the type and level of human activity, but also on the surface area and air circulation of the investigated locations. Additionally, we assessed in the same environments the filtration performance of a type IIR surgical facemask, which could overall retain 85.4 ± 3.9% of the MPs. We furthermore estimated a human MP intake from indoor air of 3415 ± 2881 MPs day-1 (mostly poly-amide MPs), which could be decreased to 283 ± 317 MPs day-1 using the surgical facemask. However, for the breathable fraction of MPs (1-5 μm), the efficiency of the surgical mask was reduced to 57.6%.

Validation of an FT-IR microscopy method for the monitorization of microplastics in water for human consumption in Portugal: Lisbon case study

The growing anthropogenic contamination of natural water by microplastics (MPs) confirms the urgent need to preserve this precious resource. MPs are part of the group of contaminants of emerging concern, and the occurrence studies in surface water and water for human consumption (WHC) are mandatory for environmental and human health risk assessment. This study aims to optimize and validate a Fourier transform infrared spectroscopy method coupled with optical microscopy (micro-FTIR) in transmission mode to monitor MPs in WHC. Water sample (250 mL; without sample pre-treatment) was filtered through 5 µm silicon filters. The infrared spectra identification was performed by OMNIC mathematical correlation, using various spectra libraries for polymers (including the in-house IR spectra library), a background reading on a clean silicon filter, and an aperture of 100 µm × 100 µm. The validated method showed good accuracy, with an average recovery for representative polymers of 91%, a relative standard deviation of 13%, and a reporting limit (RL) of 44 MPs/L. Sixty WHC samples from the Lisbon water supply system showed MPs ranging from 0 (< RL) to 934 MPs/L, with an average value of 309 MPs/L. The most representative polymers were polyethylene (PE, 76.8%), polyethylene terephthalate (PET, 6.9%), polypropylene (PP, 6%), polystyrene (PS, 4%), and polyamide (PA,4%). In terms of size, the microplastic particles had an average length and width of 76 µm and 39 µm, respectively.

Analysis of microplastics in commercial vegetable edible oils from Italy and Spain

In this work, assessment of microplastics (MPs) in commercial vegetable edible oils from Italy and Spain, including extra-virgin olive oil, olive oil, sunflower oil, and mixed seed oil, has been conducted for the first time. The method was based on sample dilution with ethanol:n-hexane (1:3, v/v), homogenization, vacuum filtration on macroporous silicon filters with 5 μm pore diameter to collect MPs, and automatic µ-FTIR spectroscopy for MPs detection and characterization. In the analysis of oil samples, a mean MPs abundance of 1140 ± 350 MPs/L was found. Observed MPs were characterized, being most of them fragments (81.2 %), with particle sizes < 100 µm (77.5 %), and mainly composed of polyethylene (50.3 %) and polypropylene (28.7 %), among others. Statistical analysis revealed that there were not significant differences (p-value > 0.05) in the abundance of MPs between oil samples or types.

Effects of Gamma Irradiation on Polyethylene Terephthalate and Detection of Microplastic Particles Down to 1 μm

In response to increasing concern about the impact of plastic degradation on the environment, this study investigates the degradation of virgin and recycled polyethylene terephthalate (PET) under γ-irradiation in aqueous solutions, with particular focus on the resulting formation of microplastic particles (MP). By exposing both virgin and recycled PET samples to different doses of γ-irradiation (10, 50, and 100 kGy), a comprehensive analysis using UV-vis spectroscopy, dynamic light scattering (DLS) and micro-Raman spectroscopy is presented. The results, highlighted by micro-Raman spectroscopy, show that γ-irradiation produces micrometer-sized plastic particles, with the recycled PET having a significantly higher MP content than its original counterpart. Careful examination reveals the presence of a stabilizer in samples of recycled PET juice bottles. This study not only contributes to our understanding of the effects of γ-irradiation on PET but also highlights the need for further research into the environmental impact of such processes. The insights gained shed light on the behavior of PET under γ-irradiation and the resulting impact on microplastic pollution and make an important contribution to our understanding of the broader environmental context.

Microplastics contamination in water supply system and treatment processes

Due to global demand, millions of tons of plastics have been widely consumed, resulting in the widespread entry of vast amounts of microplastic particles into the environment. The presence of microplastics (MPs) in water supplies, including bottled water, has undergone systematic review, assessing the potential impacts of MPs on humans through exposure assessment. The main challenges associated with current technologies lie in their ability to effectively treat and completely remove MPs from drinking and supply water. While the risks posed by MPs upon entering the human body have not yet been fully revealed, there is a predicted certainty of negative impacts. This review encompasses a range of current technologies, spanning from basic to advanced treatments and varying in scale. However, given the frequent detection of MPs in drinking and bottled water, it becomes imperative to implement comprehensive management strategies to address this issue effectively. Consequently, integrating current technologies with management options such as life-cycle assessment, circular economy principles, and machine learning is crucial to eliminating this pervasive problem.

Microplastics and non-natural cellulosic particles in Spanish bottled drinking water

This investigation explored the presence of microplastics (MPs) and artificial cellulosic particles (ACPs) in commercial water marketed in single use 1.5 L poly(ethylene terephthalate) bottles. In this work we determined a mass concentration of 1.61 (1.10-2.88) µg/L and 1.04 (0.43-1.82) µg/L for MPs and ACPs respectively in five top-selling brands from the Spanish bottled water market. Most MPs consisted of white and transparent polyester and polyethylene particles, while most ACPs were cellulosic fibers likely originating from textiles. The median size of MPs and ACPs was 93 µm (interquartile range 76-130 µm) and 77 µm (interquartile range 60-96 µm), respectively. Particle mass size distributions were fitted to a logistic function, enabling comparisons with other studies. The estimated daily intake of MPs due to the consumption of bottled water falls within the 4-18 ng kg-1 day-1 range, meaning that exposure to plastics through bottled water probably represents a negligible risk to human health. However, it's worth noting that the concentration of plastic found was much higher than that recorded for tap water, which supports the argument in favour of municipal drinking water.

Fate and behaviour of Microplastics (> 25µm) within the water distribution network, from water treatment works to service reservoirs and customer taps

Water treatment works have previously shown high efficiency in removing microplastics > 25 µm from raw source water. However, what is less well known is the extent to which microplastics of this size class are generated or lost within the water distribution network, particularly whether there is a greater presence in the customer tap than in the water treatment works outlet. This study focused on the presence of 21 different types of synthetic polymer particles with sizes larger than 25 µm examined through multiple rounds of sampling at outlets of water treatment works (WTW), service reservoirs (SR), and customer taps (CT) managed by seven different water companies in Britain. Nineteen different types of polymers were detected; their signature and concentration varied based on the round of sampling, the location within the water supply network, and the water company responsible for managing the supply. Among the polymers examined, polyamide (PA), polyethene terephthalate (PET), polypropylene (PP), and polystyrene (PS) were the most commonly found. Apart from PET having its highest concentration of 0.0189 microplastic per litre (MP/L) in the SR, the concentrations of the other three most frequent polymers (PS = 0.017 MP/L, PA = 0.0752 MP/L, PP= 0.1513 MP/L) were highest in the CT. The overall prevalence of this size of microplastics in the network is low, but there was a high variability of polymer types and occurrences. These spatial and temporal variations suggested that the MP in the distribution network may exist as a series of pulses. Given the presence and polymer types, the potential for some of the microplastics to originate from materials used in the water network and domestic plumbing systems cannot be ruled out. As found before, the absolute number of microplastics in the water distribution network remained extremely low.

Determination of Microplastics in Omega-3 Oil Supplements

Microplastics (MPs) are ubiquitous in the environment, posing a threat to ecosystems and causing increasing concerns regarding their impacts on the human body through exposure. However, there has been limited research on the presence of MPs in functional foods, despite them being consumed for health improvement. This study aimed to investigate MP occurrence in various omega-3 oils and oil products in the Korean market and its relation to the source of raw material or manufacture. MPs were investigated in omega-3 capsules and raw oil, sourced from both plant-based (PB) and animal-based (AB) sources. We developed a method of direct filtration with acetone washing for collecting and characterizing MPs larger than 5 μm using micro-Raman spectroscopy. The average number of MPs by mass was found to be 1.2 ± 1.7 MPs/g for PB raw oil, 2.2 ± 1.7 MPs/g for AB raw oil, 3.5 ± 3.9 MPs/g for PB capsule oil, and 10.6 ± 8.9 MPs/g for AB capsule oil. Polypropylene and polyethylene terephthalate were the major MP species (83-95%) found in omega-3 oil. The proportions based on size range remained consistent across all groups, with a trend of being detected at higher rates as the size decreased. The results reveal that the main reason for the MP contamination of omega-3 oil is not the source of raw material but the manufacturing and packaging process.

From the Caribbean to the Arctic, the most abundant microplastic particles in the ocean have escaped detection

Comprehensive methodologies for monitoring microplastics (MPs) in the ocean are critical for accurately assessing abundances across a broad size spectrum, and to document distributions, sources, sinks, temporal trends, and exposure risks for organisms. Discrete 0.5-L water samples from the northeastern-coast of Venezuela (NECV), Pacific-Arctic Ocean (PAO), and Gulf Stream Current (GSC) were analyzed by Raman microspectroscopy to detect MPs not captured by net-tow surveys. Equivalent spherical diameters (ESD) of most MPs were <5 μm, accounting for 68, 83, 86 % of total inventories in NECV, GSC, PAO samples. We did not observe a single MP particle >53 μm ESD. Abundances of MPs in the 0.5-200 μm size fraction were 5-6 orders of magnitude higher than previous surveys that were almost exclusively based on net tow collections of MPs > 300 μm ESD. Abundances of MPs in NECV samples were ~10-fold higher than those from PAO and GSC. The most abundant polymers were polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET), consistent with composition of plastic waste generated globally.

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.

In Vivo Tissue Distribution of Polystyrene or Mixed Polymer Microspheres and Metabolomic Analysis after Oral Exposure in Mice

BACKGROUND

Global plastic use has consistently increased over the past century with several different types of plastics now being produced. Much of these plastics end up in oceans or landfills leading to a substantial accumulation of plastics in the environment. Plastic debris slowly degrades into microplastics (MPs) that can ultimately be inhaled or ingested by both animals and humans. A growing body of evidence indicates that MPs can cross the gut barrier and enter into the lymphatic and systemic circulation leading to accumulation in tissues such as the lungs, liver, kidney, and brain. The impacts of mixed MPs exposure on tissue function through metabolism remains largely unexplored.

OBJECTIVES

This study aims to investigate the impacts of polymer microspheres on tissue metabolism in mice by assessing the microspheres ability to translocate across the gut barrier and enter into systemic circulation. Specifically, we wanted to examine microsphere accumulation in different organ systems, identify concentration-dependent metabolic changes, and evaluate the effects of mixed microsphere exposures on health outcomes.

METHODS

To investigate the impact of ingested microspheres on target metabolic pathways, mice were exposed to either polystyrene (5 μ m ) microspheres or a mixture of polymer microspheres consisting of polystyrene (5 μ m ), polyethylene (1 - 4 μ m ), and the biodegradability and biocompatible plastic, poly-(lactic-co-glycolic acid) (5 μ m ). Exposures were performed twice a week for 4 weeks at a concentration of either 0, 2, or 4 mg / week via oral gastric gavage. Tissues were collected to examine microsphere ingress and changes in metabolites.

RESULTS

In mice that ingested microspheres, we detected polystyrene microspheres in distant tissues including the brain, liver, and kidney. Additionally, we report on the metabolic differences that occurred in the colon, liver, and brain, which showed differential responses that were dependent on concentration and type of microsphere exposure.

DISCUSSION

This study uses a mouse model to provide critical insight into the potential health implications of the pervasive issue of plastic pollution. These findings demonstrate that orally consumed polystyrene or mixed polymer microspheres can accumulate in tissues such as the brain, liver, and kidney. Furthermore, this study highlights concentration-dependent and polymer type-specific metabolic changes in the colon, liver, and brain after plastic microsphere exposure. These results underline the mobility within and between biological tissues of MPs after exposure and emphasize the importance of understanding their metabolic impact. https://doi.org/10.1289/EHP13435.

Micro- and nano-plastics in the atmosphere: A review of occurrence, properties and human health risks

The ubiquitous occurrence of micro/nano plastics (MNPs) poses potential threats to ecosystem and human health that have attracted broad concerns in recent decades. Detection of MNPs in several remote regions has implicated atmospheric transport as an important pathway for global dissemination of MNPs and hence as a global health risk. In this review, the latest research progress on (1) sampling and detection; (2) origin and characteristics; and (3) transport and fate of atmospheric MNPs was summarized. Further, the current status of exposure risks and toxicological effects from inhaled atmospheric MNPs on human health is examined. Due to limitations in sampling and identification methodologies, the study of atmospheric nanoplastics is very limited today. The large spatial variation of atmospheric MNP concentrations reported worldwide makes it difficult to compare the overall indoor and outdoor exposure risks. Several in vitro, in vivo, and epidemiological studies demonstrate adverse effects of immune response, apoptosis and oxidative stress caused by MNP inhalation that may induce cardiovascular diseases and reproductive and developmental abnormalities. Given the emerging importance of atmospheric MNPs, the establishment of standardized sampling-pretreatment-detection protocols and comprehensive toxicological studies are critical to advance environmental and health risk assessments of atmospheric MNPs.

A reliable method to determine airborne microplastics using quantum cascade laser infrared spectrometry

The number of studies dealing with airborne microplastics (MPs) is increasing but sampling and sample treatment are not standardized, yet. Here, a fast and reliable method to characterize MPs is presented. It involves the study of two passive sampling devices to collect atmospheric bulk deposition (wet and dry deposition) and three digestion methods (two alkaline-oxidative and an oxidative) to treat the samples. The alkaline-oxidative method based on KOH and NaClO was selected for a mild organic matrix digestion. In addition, some operational parameters of a high-throughput quantum cascade laser-based infrared device (LDIR) were optimized: an effective automatic tiered approach to differentiate fibres from particles (>90 % success in validation) and a criterion to establish positive matches when comparing an unknown spectrum against the spectral database (proposed match index > 0.85). The procedural analytical recoveries were very good for particles (82-90 %) and slightly lower for fibres (62-73 %). Finally, the amount and type of MPs deposited at a sub-urban area NW Spain were evaluated. Most common polymers were Polyethylene (PE), Polypropylene (PP) and Polyethylene terephthalate (PET). The deposition rates ranged 98-1220 MP/m2/day, ca. 1.7 % of the total collected particles. More than 50 % of the total MPs deposited were in the 20-50 μm size range, whereas fibres were mostly in the 50-500 μm size range.

Characteristics and risks of microplastic contamination in aquaculture ponds near the Yangtze Estuary, China

Microplastic pollution has been frequently reported in natural water environments, but studies on the occurrence and characteristics of microplastic in aquaculture environments especially in pond production system are relatively scarce. Herein, we investigated the abundance and characteristics of microplastic pollution in aquaculture ponds that farm different species (fish, prawn and crab) near the Yangtze Estuary, China. The average abundance of microplastic in pond water and sediment was 36.25 ± 6.79 items/L and 271.65 ± 164.83 items/kg, respectively. Compared to fish ponds (208.43 ± 57.82 items/kg), microplastic abundance was significantly higher in sediment of crab and prawn ponds (312.02 ± 38.76 and 248.87 ± 36.51 items/kg respectively). Across all ponds, transparent, white and black microplastic were the common colors. Fiber was the most common type, accounting for 40.9% and 58.6% in pond water and sediment, respectively. The size of microplastic was mainly distributed between 300 and 1000 μm. For microplastic polymer composition, polyethylene (PE) was predominant in pond water, accounting for 55%, followed by polyamide with 15%. The predominant polymer in sediment was PE with 34%, followed by polypropylene with 18%. As for the ecological risk assessment of microplastic, the pollution load index was 7.6 (risk level I) and 8.9 (risk level I) for pond water and sediment, respectively. The polymer hazard index was 85.3 (risk level II) and 12.1 (risk level II) for pond water and sediment, respectively. Taken together, the pollution risk index was rated as high and very high for pond sediment and water, respectively. These results provide a basis for the comprehensive evaluation and developing practical approaches to deal with microplastic in aquaculture pond, which is of great significance to the healthy development of pond aquaculture.

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.

UV Irradiation of Polyethylene Terephthalate and Polypropylene and Detection of Formed Microplastic Particles Down to 1 μm

The degradation of plastics upon UVC irradiation in aqueous solution and the formation of microplastic (MP) particles were investigated. Polypropylene (PP) and recycled and virgin polyethylene terephthalate (PET) were irradiated with a UV lamp emitting light at 254 nm. Irradiation was performed for 15 and 30 min, respectively, at an intensity of about 0.3 W cm-2 . The formation of MP was studied by Raman spectroscopy. The results showed that MP particles were formed after irradiation and that their number was significantly higher in the recycled PET than in the virgin material. The number of PP MP formed was lower compared to PET and was not significantly different after 15 and 30 min. In addition, ethanol was used as an alternative solvent to investigate how its chemical properties and interactions with UVC irradiation affect the degradation of PET and PP plastics. The use of ethanol and recycled PET resulted in a lower number of MP particles at both irradiation times. When ethanol was used after 30 min of irradiation, significantly more PP MP formed. The different chemical structures of PET and PP combined with the different solvent properties of water and ethanol contribute to the differences in their susceptibility to UVC degradation.

Rapid detection and identification of microplastics from nonchemically treated soil with CARS microspectroscopy

In conventional microplastic (MP) analysis, acid or alkaline digestion is a necessary pretreatment step to remove residual organic matter from environmental samples. However, such a digestion process is not only cumbersome and time-consuming, but also possibly cause severe chemical damage to the MP itself, often making accurate MP characterization difficult. This study demonstrates that broadband coherent anti-Stokes Raman scattering (CARS) microspectroscopy is useful for rapidly detecting and identifying MPs in natural soil without any digestion process. A feasibility test is performed with soil samples, which are known to require the most complicated chemical pretreatment for MP analysis, deliberately mixed with various MP particles. The C-H bond-specific CARS imaging and spectral analysis allow rapid MP particle search and chemical identification even in the presence of other residual particles and strongly fluorescent substances from the soil. It is anticipated that this nondestructive, chemical pretreatment-free CARS approach will be a beneficial tool for studying the ecological impacts of MPs absorbed by terrestrial life, such as plants and soil organisms, as well as for complementary analysis of MPs subject to chemical degradation by digestion in investigating the environmental contamination of the MPs.

Rapid single-particle chemical imaging of nanoplastics by SRS microscopy

Plastics are now omnipresent in our daily lives. The existence of microplastics (1 µm to 5 mm in length) and possibly even nanoplastics (<1 μm) has recently raised health concerns. In particular, nanoplastics are believed to be more toxic since their smaller size renders them much more amenable, compared to microplastics, to enter the human body. However, detecting nanoplastics imposes tremendous analytical challenges on both the nano-level sensitivity and the plastic-identifying specificity, leading to a knowledge gap in this mysterious nanoworld surrounding us. To address these challenges, we developed a hyperspectral stimulated Raman scattering (SRS) imaging platform with an automated plastic identification algorithm that allows micro-nano plastic analysis at the single-particle level with high chemical specificity and throughput. We first validated the sensitivity enhancement of the narrow band of SRS to enable high-speed single nanoplastic detection below 100 nm. We then devised a data-driven spectral matching algorithm to address spectral identification challenges imposed by sensitive narrow-band hyperspectral imaging and achieve robust determination of common plastic polymers. With the established technique, we studied the micro-nano plastics from bottled water as a model system. We successfully detected and identified nanoplastics from major plastic types. Micro-nano plastics concentrations were estimated to be about 2.4 ± 1.3 × 105 particles per liter of bottled water, about 90% of which are nanoplastics. This is orders of magnitude more than the microplastic abundance reported previously in bottled water. High-throughput single-particle counting revealed extraordinary particle heterogeneity and nonorthogonality between plastic composition and morphologies; the resulting multidimensional profiling sheds light on the science of nanoplastics.

Microplastics attenuation from surface water to drinking water: Impact of treatment and managed aquifer recharge - and identification uncertainties

River water can be used to recharge aquifers exploited for drinking water production. Several recent studies reported microplastics (MPs) in river water, and therefore, the potential contamination of groundwater by MPs is a growing concern among stakeholders and citizens. In this research, we investigate the fate of MPs (> 20 μm) along six different stages of a major Managed Aquifer Recharge (MAR)-water supply system in Switzerland. About 20 l of water were filtered using steel meshes at each location in triplicates. In the laboratory, MPs deposited on the anodisc filters were identified using Focal Plane Array (FPA) micro-Fourier-Transform-InfraRed (μFTIR) spectroscopy. The obtained hyperspectral data were processed using the imaging software Microplastics Finder for MPs identification and classification. Our results revealed a 20-fold decrease in MPs concentration from the Rhine River bed water (112 ± 27.4 MPs/l) to after the coagulation, flocculation and sedimentation (5.5 ± 2.2 MPs/l), a further 3-fold decrease to after the sand-filtration system (1.8 ± 0.9 MPs/l), corresponding to an overall removal efficiency of 98.4 %. The MPs concentrations remained low following MAR (2.7 ± 0.7 MPs/l) through a Quaternary gravel aquifer. Activated carbon filters did not substantially further reduce MPs concentrations. The percentage of fragments (≈95 %) prevailed over fibers (≈5 %) at all locations, with fibers being longer and more abundant in the river water. Overall, this study demonstrates the effectiveness of the treatment systems to remove MPs larger than 20 μm. Finally, we calculated an uncertainty in MPs concentrations of one order of magnitude depending on the user-defined parameters inside the MPs identification and classification model. The Quality Assurance/Quality Control approach followed during laboratory analysis highlighted an accumulation of surrogate particles at the edges of the disc, which would have an impact for MPs number upscaling.

Are fishes selecting the trash they eat? Influence of feeding mode and habitat on microplastic uptake in an artificial reef complex (ARC)

Every year, coastal countries generate ∼275 million tons of plastic, and the oceans receive from 4.8 to 12.7 million tons3. Pollution by synthetic polymers is even more problematic for the environment when this material is fragmented into small portions, forming microplastics (MPs). In the present study, we analyze the selection of MPs by the ichthyofauna based on the availability of the morphotypes and polymeric composition of microplastic in the environment and compare the amount of MP in surface water, water column, sediments and fish in different organs, trophic categories, habitats and areas with and without artificial reefs. In order to achieve this goal, the shape, color, abundance and chemical composition of MPs in the digestive tract and gills of 18 fish species in artificial reefs area and control area, were evaluated. A total of 216 fish were analyzed, and 149 (60 %) had MPs in at least one organ and showed a mean concentration of 1.55 ± 3.31 MPs/g. Of the 18 fish species collected in the reef complex area, 17 (94 %) included individuals with at least one MP in digestive tract or gills. Four species showed the higher selectivity of MP types, colors, and polymers. More MPs were found in the fish, surface water, water column and sediment in the artificial reef area compared to the control areas. This is the first evidence of MP selection by commercially important fish species in artificial marine structures worldwide. These results provide useful information on MP pollution in RAs and highlight yet another issue that must be considered in the management of fisheries resources in the region and in other reef complexes around the world.

Exposure to micro(nano)plastics polymers in water stored in single-use plastic bottles

Human exposure to micro (nano)plastics (MNPLs) has become a significant concern as a potential health threat. Exposure routes include ingestion, inhalation, and dermal contact, being food and drinking water the primary sources of oral exposure. Here we present the quantification of polymers of MNPLs particles from 700 nm to 20 μm in bottled water commercialised in Spain, including an estimation of the potential risk for daily consumers. We evaluated samples from 20 popular brands in 0.5 and 1.5 L plastic bottles. A double-suspect screening approach developed and validated in our research group for drinking water was adapted for bottled water samples. The identification and quantification of MNPLs-polymers in mass units and the tentative identification of plastic additives (PA) until the second level of confidence was carried out based on high-performance liquid chromatography coupled to high-resolution mass spectrometry (HPLC-HRMS). The results showed the presence of polypropylene (PP), polyethylene (PE) and polypropylene terephthalate (PET) in the samples. Among them, PE was the most frequently detected and quantified polymer (55% of samples) followed by PET which was detected in 33% of the samples and showing the highest concentration (4700 ng L-1). The median value of the sum of polymer concentrations was 359 ng L-1. In addition, 28 plastic additives were detected, where at least one of them was present in 100% of the samples. Stabilizers and plasticisers were the most frequently identified. A prioritisation study was performed using a multi-QSAR modelling software, where bis(2-ethylhexyl) adipate and bis(2-ethylhexyl) phthalate were estimated as the most potentially harmful compounds for human health. Overall, findings suggest that bottled water is a non-negligible route to exposure to MNPLs.

When microplastics meet electroanalysis: future analytical trends for an emerging threat

Microplastics are a major modern challenge that must be addressed to protect the environment, particularly the marine environment. Microplastics, defined as particles ≤5 mm, are ubiquitous in the environment. Their small size for a relatively large surface area, high persistence and easy distribution in water, soil and air require the development of new analytical methods to monitor their presence. At present, the availability of analytical techniques that are easy to use, automated, inexpensive and based on new approaches to improve detection remains an open challenge. This review aims to outline the evolution and novelties of classical and advanced methods, in particular the recently reported electroanalytical detectors, methods and devices. Among all the studies reviewed here, we highlight the great advantages of electroanalytical tools over spectroscopic and thermal analysis, especially for the rapid and accurate detection of microplastics in the sub-micron range. Finally, the challenges faced in the development of automated analytical methods are discussed, highlighting recent trends in artificial intelligence (AI) in microplastics analysis.

A review of recent progress in the application of Raman spectroscopy and SERS detection of microplastics and derivatives

The global environmental concern surrounding microplastic (MP) pollution has raised alarms due to its potential health risks to animals, plants, and humans. Because of the complex structure and composition of microplastics (MPs), the detection methods are limited, resulting in restricted detection accuracy. Surface enhancement of Raman spectroscopy (SERS), a spectral technique, offers several advantages, such as high resolution and low detection limit. It has the potential to be extensively employed for sensitive detection and high-resolution imaging of microplastics. We have summarized the research conducted in recent years on the detection of microplastics using Raman and SERS. Here, we have reviewed qualitative and quantitative analyses of microplastics and their derivatives, as well as the latest progress, challenges, and potential applications.

Review of scientific literature on available methods of assessing organochlorine pesticides in the environment

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs) widely used in agriculture and industry, causing serious health and ecological consequences upon exposure. This review offers a thorough overview of OCPs analysis emphasizing the necessity of ongoing work to enhance the identification and monitoring of these POPs in environmental and human samples. The benefits and drawbacks of the various OCPs analysis techniques including gas chromatography-mass spectrometry (GC-MS), gas chromatography-electron capture detector (GC-ECD), and liquid chromatography-mass spectrometry (LC-MS) are discussed. Challenges associated with validation and optimization criteria, including accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ), must be met for a method to be regarded as accurate and reliable. Suitable quality control measures, such as method blanks and procedural blanks, are emphasized. The LOD and LOQ are critical quality control measure for efficient quantification of these compounds, and researchers have explored various techniques for their calculation. Matrix interference, solubility, volatility, and partition coefficient influence OCPs occurrences and are discussed in this review. Validation experiments, as stated by European Commission in document SANTE/11813/2017, showed that the acceptance criteria for method validation of OCP analytes include ≤20 % for high precision, and 70-120 % for recovery. This may ultimately be vital for determining the human health risk effects of exposure to OCP and for formulating sensible environmental and public health regulations.

Ecological traits do not predict the uptake of microplastics by fishes in a Neotropical River

Pollution by synthetic polymers is even more problematic to the environment when this material is fragmented into small portions, forming microplastics (MPs). We analyzed the contamination of ichthyofauna by MPs in an important river of the Atlantic Rainforest in regard to abundance, diversity of morphotypes, polymers, colors, and sizes of the synthetic particles in 20 species of fish. Fish were collected in November 2019 and in March 2020 in five sites along the Pomba River. Of the 101 fish analyzed, 49 (49%) presented MPs in at least one organ. Of the 20 species of fish collected 13 included individuals with at least one MP in their analyzed organs. The organs, trophic categories and feeding areas did not affect the general abundance of MPs types. Blue MPs were predominant, followed by the colors black, red, and white. MP fibers represented 91% of total MPs. Most MPs were between 2 and 3 mm in size. Polyethylene terephthalate (PET), polypropylene (PP), polyamide (PA), polyvinylidene chloride "Nylon" (PVDC), and high-density polyethylene (HDPE) were detected in the fishes. The exposure of the fish species to MPs was associated mainly with individual size and species-specific aspects, regardless of ecological traits. Considering that 55% of the fish species studied are consumed by humans, it is necessary to study the potential impact of MP ingestion on human health and to understand to what extent we may be consuming both plastic particles and contaminants that are adsorbed to MPs.

Microplastics: Human exposure assessment through air, water, and food

BACKGROUND

Microplastics (MP) are plastic particles with dimension up to 5 mm. Due to their persistence, global spread across different ecosystems and potential human health effects, they have gained increasing attention during the last decade. However, the extent of human exposure to MP through different pathways and their intake have not been elucidated.

OBJECTIVES

The objective of this review is to provide an overview on the pathways of exposure to MP through inhalation, ingestion, and dermal contact considering data from the open bibliography on MP in air, dust, food, water and drinks.

METHODS

A bibliographic search on Scopus and PubMed was conducted using keywords on MP in outdoor and indoor air, indoor dust, food including beverages and water and human intake (n = 521). Articles were sorted by their title and abstract (n = 213), and only studies reporting MP identification and quantification techniques were further considered (n = 168). A total of 115 articles that include quality assurance and quality control (QA/QC) procedures are finally discussed in the present review. Based on MP concentration data available in literature, we estimated the potential inhaled dose (ID), dust intake (DI), the estimated daily intake (EDI) via food and beverages. Finally, the total daily intake (TDI) considering both inhalation and ingestion routes are provided for adults, infants and newborns.

RESULTS

The concentrations of MP in outdoor and indoor air, dust, and in food and water are provided according to the bibliography. Human exposure to MP through dust ingestion, inhalation of air and food/drinks consumption revealed that indoor air and drinking waters were the main sources of MP.

CONCLUSIONS

This study reveals that humans are constantly exposed to MP, and that the indoor environment and the food and water we ingest decisively contribute to MP intake. Additionally, we highlight that infants and newborns are exposed to high MP concentrations and further studies are needed to evaluate the presence and risk of MP in this vulnerable age-population.

M. M. Ferraz M. Microplastics analytics: why we should not underestimate the importance of blank controls

Recent years have seen considerable scientific attention devoted towards documenting the presence of microplastics (MPs) in environmental samples. Due to omnipresence of environmental microplastics, however, disentangling environmental MPs from sample contamination is a challenge. Hence, the environmental (collection site and laboratory) microplastics contamination of samples during processing is a reality that we must address, in order to generate reproducible and reliable data. Here we investigated published literature and have found that around 1/5 of studies failed to use blank controls in their experiments. Additionally, only 34% of the studies used a controlled air environment for their sample processing (laminar flow, fume hood, closed laboratory, clean room, etc.). In that regard, we have also shown that preparing samples in the fume hood, leads to more microplastics > 1 μm) contamination than preparing it in the laboratory bench and the laminar flow. Although it did not completely prevent microplastics contamination, the processing of sample inside the laminar flow is the best option to reduce sample contamination during processing. Overall, we showed that blank controls are a must in microplastics sample preparation, but it is often overlooked by researchers.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s43591-023-00065-3.

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.

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 microfluidic approach for label-free identification of small-sized microplastics in seawater

Marine microplastics are emerging as a growing environmental concern due to their potential harm to marine biota. The substantial variations in their physical and chemical properties pose a significant challenge when it comes to sampling and characterizing small-sized microplastics. In this study, we introduce a novel microfluidic approach that simplifies the trapping and identification process of microplastics in surface seawater, eliminating the need for labeling. We examine various models, including support vector machine, random forest, convolutional neural network (CNN), and residual neural network (ResNet34), to assess their performance in identifying 11 common plastics. Our findings reveal that the CNN method outperforms the other models, achieving an impressive accuracy of 93% and a mean area under the curve of 98 ± 0.02%. Furthermore, we demonstrate that miniaturized devices can effectively trap and identify microplastics smaller than 50 µm. Overall, this proposed approach facilitates efficient sampling and identification of small-sized microplastics, potentially contributing to crucial long-term monitoring and treatment efforts.

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.

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.

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.

Common laboratory reagents: Are they a double-edged sword in microplastics research?

Understanding and communicating instances of microplastic contamination is critical for enabling plastic-free transitions. While microplastics research uses a variety of commercial chemicals and laboratory liquids, the impact of microplastics on these materials remains unknown. To fill this knowledge gap, the current study investigated microplastics abundance and their characteristics in laboratory waters (distilled, deionized, and Milli-Q), salts (NaCl and CaCl₂), chemical solutions (H₂O₂, KOH and NaOH), and ethanol from various research laboratories and commercial brands. The mean abundance of microplastics in water, salt, chemical solutions, and ethanol samples was 30.21 ± 30.40 (L^-1), 24.00 ± 19.00 (10 g^-1), 187.00 ± 45.00 (L^-1), and 27.63 ± 9.53 (L^-1), respectively. Data comparisons revealed significant discrepancies between the samples in terms of microplastic abundance. Fibers (81 %) were the most common microplastics, followed by fragments (16 %) and films (3 %); 95 % of them were <500 μm, with the smallest and largest particle sizes recorded being 26 μm and 2.30 mm, respectively. Microplastic polymers discovered included polyethylene, polypropylene, polyester, nylon, acrylic, paint chips, cellophane, and viscose. These findings lay the groundwork for identifying common laboratory reagents as a potential contributor to microplastic contamination in samples, and we offer solutions that should be integrated into data processing to produce accurate results. Taken together, this study shows that commonly used reagents not only play a key role in the microplastic separation process but also contain microplastic contamination themselves, requiring the attention of researchers to promote quality control during microplastic analysis and commercial suppliers in formulating novel prevention strategies.

Classification of household microplastics using a multi-model approach based on Raman spectroscopy

The extensive use of plastics leads to the release and diffusion of microplastics. Household plastic products occupy a large part and are closely related to daily life. Due to the small size and complex composition of microplastics, it is challenging to identify and quantify microplastics. Therefore,a multi-model machine learning approach was developed for classification of household microplastics based on Raman spectroscopy. In this study, Raman spectroscopy and machine learning algorithm are combined to realize the accurate identification of seven standard microplastic samples, real microplastics samples and real microplastic samples post-exposure to environmental stresses. Four single-model machine learning methods were used in this study, including Support vector machine (SVM), K-nearest neighbor (KNN), Linear discriminant analysis (LDA), and Multi-layer perceptron (MLP) model. The principal components analysis (PCA) was utilized before SVM, KNN and LDA. The classification effect of four models on standard plastic samples is over 88%, and reliefF algorithm was used to distinguish HDPE and LDPE samples. A multi-model is proposed based on four single models including PCA-LDA, PCA-KNN and MLP. The recognition accuracy of multi-model for standard microplastic samples, real microplastic samples and microplastic samples post-exposure to environmental stresses is over 98%. Our study demonstrates that the multi-model coupled with Raman spectroscopy is a valuable tool for microplastic classification.

Do drinking water plants retain microplastics? An exploratory study using Raman micro-spectroscopy

The retainment of microplastics (MPs) down to 1 μm by a Danish drinking water plant fed with groundwater was quantified using Raman micro-spectroscopy (μRaman). The inlet and outlet were sampled in parallel triplicates over five consecutive days of normal activity. For each triplicate, approximately 1 m³ of drinking water was filtered with a custom-made device employing 1 μm steel filters. The MP abundance was expressed as MP counts per liter (N/L) and MP mass per liter (pg/L), the latter being estimated from the morphological parameters provided by the μRaman analysis. Hence the treated water held on average 1.4 MP counts/L, corresponding to 4 pg/L. The raw water entering the sand filters held a higher MP abundance, and the overall efficiency of the treatment was 43.2% in terms of MP counts and 75.1% in terms of MP mass. The reason for the difference between count-based and mass-based efficiencies was that 1-5 μm MP were retained to a significantly lower degree than larger ones. Above 10 μm, 79.6% of all MPs were retained by the filters, while the efficiency was only 41.1% below 5 μm. The MP retainment was highly variable between measurements, showing an overall decreasing tendency over the investigated period. Therefore, the plastic elements of the plant (valves, sealing components, etc.) likely released small-sized MPs due to the mechanical stress experienced during the treatment. The sub-micron fraction (0.45-1 μm) of the samples was also qualitatively explored, showing that nanoplastics (NPs) were present and that at least part hereof could be detected by μRaman.

Evidence of microplastics in leachate of Randegan landfill, Mojokerto City, Indonesia, and its potential to pollute surface water

About 80-90 tons municipal solid waste (MSW) in Mojokerto City, Indonesia, is disposed of into Randegan landfill daily. The landfill was facilitated with a conventional leachate treatment plant (LTP). The plastic waste component in the MSW, which is 13.22 % weight, possibly contaminates leachate with microplastics (MPs). This research aims to determine the presence of MPs in leachate of the landfill, its characteristics, and the removal efficiency of the LTP. The potential of leachate as MP pollutant source to surface water was also discussed. Raw leachate samples were collected from the LTP inlet channel. Leachate samples were also taken from each LTP's sub-units. Leachate collection was performed two times using a 2.5 L glass bottle during March 2022. The MPs were treated using Wet Peroxide Oxidation method, and filtered using PTFE membrane. MP size and shape were determined using a dissecting microscope with 40-60 x magnifications. The polymer types in the samples were identified using Thermo Scientific™ Nicolet™ iS™ 10 FTIR Spectrometer. The average MP abundance in raw leachate was 9.00 ± 0.85 particles/L. MP shape in the raw leachate was dominated by fiber (64.44 %), followed by fragment (28.89 %), and film (6.67 %). The majority of the MPs were of black color (53.33 %). Abundance of 350 - <1000 μm sized MPs was the highest (64.44 %) in the raw leachate, followed by those of 100-350 μm (31.11 %), and 1000-5000 μm (4.45 %). MP removal efficiency of the LTP was 75.6 %, leaving <100 μm fiber shaped MP residuals of 2.20 ± 0.28 p/L in the effluent. Based on these results, effluent of the LTP is considered potential as MP contamination source to surface water.

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.

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.

Microplastics contamination and characteristics of agricultural groundwater in Haean Basin of Korea

The quality of groundwater is critical to human health. MPs have access to groundwater from the soil, polluted by various agricultural activities. However, to date, there have been no studies on the occurrence of MP in groundwater from an agriculture field without any adjacent sources of contamination, such as nearby landfills. In this study, the occurrence and distribution of MPs in groundwater of an agricultural area in the Haean Basin, Korea, without any definite source of pollution, was examined. MP and groundwater samplings were conducted in the dry season in 2020, the wet and dry seasons in 2021, respectively. In this study, the reliability of MP analysis was improved through good practices from laboratory to field campaigns, collecting large groundwater samples (300-500 L) volumes. Any involvement of plastic materials was avoided during the full procedures as possible and. Detailed investigation was conducted for the distribution of potential plastics sources like mulching, plastic covers, dripping pipes and shading nets, and hydrogeological properties affecting MPs occurrence. Groundwater MP concentrations of 0.02-0.15 particles/L (median = 0.06 particles/L), 0.02-2.56 particles/L (median = 0.43 particles/L) and 0.20-3.48 particles/L (median = 0.83 particles/L) were found in three rounds of sampling that comprised of the exploratory investigation in 2020, the wet season, and the dry season in 2021, respectively. The identified polymer types were polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS) and polyamide (PA). The MPs concentrations showed no statistically significant seasonal variation but revealed an apparent strong positive correlation (r = 0.71) of MPs with the amount of groundwater use. Findings of this study need more clarification from repeated samplings for multiple years. This study reveals the occurrence of MPs in groundwater in Korea for the first time to the best of our knowledge.

Microplastics in fishes in amazon riverine beaches: Influence of feeding mode and distance to urban settlements

Microplastic (MP) pollution is a global problem and has affected several biological levels even in protected areas. In the present study, MP contamination was investigated in fish associated with sandy beaches in a permanent environmental protection area in the Amazon. In order to achieve this goal, the shape, color, abundance, richness, and chemical composition of MPs in the digestive tract of 29 fish species in 24 beaches of the Machado River, western Brazilian Amazon, were evaluated. Linear mixed models (LMMs) were adjusted to test the effects of local human modification (HMc), distance from urban settlements, distance from the closest affluent, and trophic categories of fish species on microplastic abundance and richness in their digestive tracts. From the 1082 fish analyzed, 332 (30 %) presented MPs in their digestive tracts. A total of 617 MPs was found (1.8 ± 1.6 MPs; 4.5 ± 1.9 MPs/g fish). Omnivorous and insectivorous fish presented more MPs in sandy beaches located closer to urban settlements. However, carnivorous fish presented a higher abundance of MPs in their digestive tracts compared with the other trophic guilds. This is the first study to analyze plastic contamination in fish associated with sandy beaches in the Amazon (Brazil), and it revealed contamination of the ichthyofauna mainly related to the distance from urban settlements. Our results reinforce the need for better management of landscape surrounding protected areas to mitigate MP pollution.

Prevalence and implications of microplastics in potable water system: An update

Synthetic plastics, which are lightweight, durable, elastic, mouldable, cheap, and hydrophobic, were originally invented for human convenience. However, their non-biodegradability and continuous accumulation at an alarming rate as well as subsequent conversion into micro/nano plastic scale structures via mechanical and physio-chemical degradation pose significant threats to living beings, organisms, and the environment. Various minuscule forms of plastics detected in water, soil, and air are making their passage into living cells. High temperature and ambient humidity increase the degradation potential of plastic polymers photo-catalytically under sunlight or UV-B radiations. Microplastics (MPs) of polyethylene terephthalate, polyethylene, polystyrene, polypropylene, and polyvinyl chloride have been detected in bottled water. These microplastics are entering into the food chain cycle, causing serious harm to all living organisms. MPs entering into the food chain are usually inert in nature, possessing different sizes and shapes. Once they enter a cell or tissue, it causes mechanical damage, induces inflammation, disturbs metabolism, and even lead to necrosis. Various generation routes, types, impacts, identification, and treatment of microplastics entering the water bodies and getting associated with various pollutants are discussed in this review. It emphasizes potential detection techniques like pyrolysis, gas chromatography-mass spectrometry (GC-MS), micro-Raman spectroscopy, and fourier transform infrared spectroscopy (FT IR) spectroscopy for microplastics from water samples.

Formation of disinfection by-products from microplastics, tire wear particles, and other polymer-based materials

Disinfection by-products (DBPs) are formed through the disinfection of water containing precursors such as natural organic matter or anthropogenic compounds (e.g., pharmaceuticals and pesticides). Due to the ever increasing use of plastics, elastomers, and other polymers in our daily lives, polymer-based materials (PBMs) are detected more frequently and at higher concentrations in water and wastewater. The present review provides a comprehensive and systematic analysis of the contribution of PBMs - including elastomers, tire waste, polyelectrolytes, and microplastics - as precursors of DBPs in water and wastewater. Literature shows that the presence of PBMs can lead to the leaching of dissolved organic matter (DOM) and subsequent formation of DBPs upon disinfection in aqueous media. The quantity and type of DBPs formed strongly depends on the type of polymer, its concentration, its age, water salinity, and disinfection conditions such as oxidant dosage, pH, temperature, and contact time. DOM leaching from elastomers and tire waste was shown to form N-nitrosodimethylamine up to concerning levels of 930 ng/L and 466,715 ng/L, respectively upon chemical disinfection under laboratory conditions. Polyelectrolytes can also react with chemical disinfectants to form toxic DBPs. Recent findings indicate trihalomethanes formation potential of plastics can be as high as 15,990 µg/L based on the maximum formation potential under extreme conditions. Our analysis highlights an overlooked contribution of DOM leaching from PBMs as DBP precursors during disinfection of water and wastewater. Further studies need to be conducted to ascertain the extent of this contribution in real water and wastewater treatment plants.

Removal of drug dexamethasone from aqueous matrices using low frequency ultrasound: Kinetics, transformation products, and effect of microplastics

Sonochemical oxidation was employed for the degradation of the drug dexamethasone (Dex). The oxidation at 20 kHz followed pseudo-first-order kinetics and increased with applied ultrasound power density. Acoustic cavitation at 71 W/L was able to eliminate 500 μg/L of dexamethasone from ultrapure water at inherent pH in less than 60 min. The oxidation was enhanced at pH 3 and decreased at increased Dex concentration. Scavenging experiments with tert-butanol showed that hydroxyl radicals play a crucial role in decomposition, where the reaction mainly occurs on the gas-liquid interface of the formed cavities. The addition of chloride did not affect Dex removal, while in the presence of 10 mg/L of humic acid or bicarbonate, the apparent kinetic constant decreased from 0.0423 ± 0.004 min^-1 to about 0.03 ± 0.002 min^-1. The rate in secondary effluent was 3.3 times lower than in ultrapure water due to the complexity of the actual matrix. Six transformation products were identified via high resolution LC-MS during the sonochemical oxidation of 3 mg/L Dex in ultrapure water. The presence of polyethylene or polystyrene microplastics slightly enhanced DEX sonodegradation. The effect of ultrasound irradiation at 71 W/L for 60 min on the microplastics surfaces was inconsiderable.

Recognition and movement of polystyrene nanoplastics in fish cells

Although nanoplastics are being increasingly scrutinized, little is known about their kinetic behavior in living organisms, especially in cellular systems. Herein, nonspecific interactions of three polystyrene nanoplastics (pristine-PS, NH₂-PS, and COOH-PS, with size range of 90-100 nm and at concentrations of 0-100 μg mL^-1) with zebrafish cells were quantified for their cellular uptake and exocytosis. Cell uptake of nanoplastics reached a peak within 2 h and then decreased. The overall nanoplastics uptake was dominated by PS-particle internalization. The estimated uptake rate was comparable among the different types of PS (pristine-PS, NH₂-PS, and COOH-PS), but the uptake capacity was related to their functionality. The clathrin-mediated and caveolae-mediated pathways were mainly involved in the uptake of the three nanoplastics. The internalized PS-particles were initially delivered to the cytoplasm but then transported to lysosomes using energy. Meanwhile, these PS particles were released by the cells via energy-free penetration and energy-dependent lysosomal exocytosis. PS-particles were removed by the cells at a relatively slow rate, and the estimated retention half-lives of these PS-particles were 10.1 h, 12.0 h and 15.1 h for pristine-PS, NH₂-PS and COOH-PS particles, respectively, in fish cells based on our kinetic measurements. Intracellular trajectory modeling of nanoplastics movement is critical for the environmental and human health risk assessment.