Review of research on migration, distribution, biological effects, and analytical methods of microfibers in the environment

Kelp Forest Food Webs as Hot Spots for the Accumulation of Microplastic and Polybrominated Diphenyl Ether Pollutants

Kelp forests (KFs) are one of the most significant marine ecosystems in the planet. They serve as a refuge for a wide variety of marine species of ecological and economic importance. Additionally, they aid with carbon sequestration, safeguard the coastline, and maintain water quality. Microplastic (MP) and polybrominated diphenyl ethers (PBDEs) concentrations were analyzed across trophic levels in KFs around Todos Santos Bay. Spatial variation patterns were compared at three sites in 2021 and temporal change at Todos Santos Island (TSI) in 2021 and 2022. We analyzed these MPs and PBDEs in water, primary producers (Macrocystis pyrifera), grazers (Strongylocentrotus purpuratus), predators (Semicossyphus pulcher), and kelp detritus. MPs were identified in all samples (11 synthetic and 1 semisynthetic polymer) and confirmed using Fourier-transform infrared microspectroscopy-attenuated total reflectance (μ-FTIR-ATR). The most abundant type of MP is polyester fibers. Statistically significant variations in MP concentration were found only in kelps, with the greatest average concentrations in medium-depth kelps from TSI in 2022 (0.73 ± 0.58 MPs g-1 ww) and in the kelp detritus from TSI in 2021 (0.96 ± 0.64 MPs g-1 ww). Similarly, PBDEs were found in all samples, with the largest concentration found in sea urchins from Punta San Miguel (0.93 ± 0.24 ng g-1 ww). The similarity of the polymers can indicate a trophic transfer of MPs. This study shows the extensive presence of MP and PBDE subtropical trophic web of a KF, but correlating these compounds in environmental samples is highly complex, influenced by numerous factors that could affect their presence and behavior. However, this suggests that there is a potential risk to the systems and the services that KFs offer.

Deciphering morphology patterns of environmental microfibers: Insights into source apportionment

Microfibers, a prevalent form of microplastics, undergo diverse environmental interactions resulting in varied morphological changes. These changes can offer insights into their environmental trajectories. Despite its importance, comprehensive studies on microfiber morphology are scarce. This study collected 233 microfibers from the East China Sea and South China Sea. Based on morphological features observed in microscopic images of microfibers, such as curvature, cross-sectional shapes, diameter variations, and crack shapes, we identified a general morphological pattern, classifying the environmental microfibers into three distinct morphological types. Our findings highlight noticeable differences in morphological metrics (e.g., length, diameter, and surface roughness) across three types, especially the diameter. Microfibers of Type I had an average diameter of 19.45 ± 4.93 μm, significantly smaller than Type II (263.00 ± 75.15 μm) and Type III (299.68 ± 85.62 μm). Within the three-dimensional (3D) space fully defined by these quantitative parameters, the clustering results of microfibers are also consistent with the proposed morphology pattern, with each category showing a potential correlation with specific chemical compositions. Type I microfibers correspond to synthetic cellulose, while 94.79 % of Types II and III are composed of polymers. Notably, we also validated the great applicability of the morphology categories to microfibers in diverse environmental compartments, including water and sediments in nearshore and offshore areas. This classification aids in the efficient determination of microfiber sources and the assessment of their ecological risks, marking a significant advancement in microfiber environmental studies.

A study on textile microfiber contamination in the gastrointestinal tracts of Merluccius merluccius samples from the Tyrrhenian Sea

The increased demand and consumption of synthetic textiles have contributed to microplastic pollution in the form of microfibers. These particles are widely spread in the aquatic environment, leading to the exposure of marine biota, including edible species. The current study aimed to assess the extent of microfiber contamination in a commercially relevant fish species, Merluccius merluccius, which is considered a small-scale bioindicator for the monitoring of plastic ingestion in the Mediterranean coastal environment. The frequency of ingestion, abundance, and composition of textile microfibers isolated from the fish gut were characterized. Results showed the occurrence of microfibers in 75% of the samples, with a mean number of 10.6 microfibers/individual, of which 70% were classified as natural microfibers. The spectroscopic analyses confirmed both the visual identification of microfibers and the prevalence of cellulosic fibers. The obtained findings provided evidence of both natural/artificial and synthetic microfiber exposure in an important commercial fish species that, considering the consumption of small individuals without being eviscerated, may be a potential route of microfiber exposure in humans. Monitoring programs for fishery products from markets are needed to assess contamination levels and human health risks. In addition, measures to control microfiber pollution need to occur at multiple levels, from textile industries to international governments.

Like noodles in a soup: Anthropogenic microfibers are being ingested by juvenile fish in nursery grounds of the Southwestern Atlantic Ocean

The balance between marine health and ecosystem sustainability confronts a pressing threat from anthropogenic pollution. Estuaries are particularly susceptible to contamination, notably by anthropogenic microfibers originated from daily human activities in land and in fishing practices. This study examines the impact of anthropogenic microfibers on the whitemouth croaker in an estuarine environment of the Southwestern Atlantic Ocean during cold and warm seasons. The presence of anthropogenic microfibers was revealed in 64 % of juvenile gastrointestinal tracts, and 94 % of water samples, and concentrations were influenced by factors such as temperature, bay zone, and fish body length. Blue and black anthropogenic microfibers, with a rather new physical aspect, were dominant. This study highlights the impact of microfibers in a heavily anthropized body of water, subject to federal and local regulations due to the presence of commercially significant fish species inhabiting this area.

Efficacy of bacterial cellulose hydrogel in microfiber removal from contaminated waters: A sustainable approach to wastewater treatment

Microfibers (MFs), the dominant form of microplastics in ecosystems, pose a significant environmental risk due to the inadequacy of existing wastewater treatments to remove them. Recognising the need to develop sustainable solutions to tackle this environmental challenge, this research aimed to find an eco-friendly solution to the pervasive problem of MFs contaminating water bodies. Unused remnants of bacterial cellulose (BC) were ground to form a hydrogel-form of bacterial cellulose (BCH) and used as a potential bioflocculant for polyacrylonitrile MFs. The flocculation efficiency was evaluated across various operational and environmental factors, employing response surface methodology computational modelling to elucidate and model their impact on the process. The results revealed that the BCH:MFs ratio and mixing intensity were key factors in flocculation efficiency, with BCH resilient across a range of environmental conditions, achieving a 93.6 % average removal rate. The BCH's strong retention of MFs released only 8.3 % of the MFs, after a 24-hour wash, and the flocculation tests in contaminated wastewater and chlorinated water yielded 89.3 % and 86.1 % efficiency, respectively. Therefore, BCH presents a viable, sustainable, and effective approach for removing MFs from MFs-contaminated water, exhibiting exceptional flocculation performance and adaptability. This pioneer study using BCH as a bioflocculant for MFs removal sets a new standard in sustainable wastewater treatment, catalysing research on fibrous pollutant mitigation for environmental protection.

Microplastics Prevalence in Different Cetaceans Stranded along the Western Taiwan Strait

Microplastics (MPs) pollution is of global concern, which poses serious threats to various marine organisms, including many threatened apex predators. In this study, MPs were investigated from nine cetaceans of four different species, comprising one common dolphin (Delphinus delphis), two pygmy sperm whales (Kogia breviceps), one ginkgo-toothed beaked whale (Mesoplodon ginkgodens), and five Indo-Pacific humpback dolphins (Sousa chinensis) stranded along the western coast of the Taiwan Strait from the East China Sea based on Fourier transform infrared (FTIR) spectroscopy analysis. Mean abundances of 778 identified MPs items were 86.44 ± 12.22 items individual-1 and 0.43 ± 0.19 items g-1 wet weight of intestine contents, which were found predominantly to be transparent, fiber-shaped polyethylene terephthalate (PET) items usually between 0.5 and 5 mm. The abundance of MPs was found at a slightly higher level and significantly correlated with intestine contents mass (p = 0.0004*). The MPs source was mainly likely from synthetic fibers-laden sewage discharged from intense textile industries. Our report represents the first study of MPs in pelagic and deep-diving cetaceans in China, which not only adds baseline data on MPs for cetaceans in Asian waters but also highlights the further risk assessment of MPs consumption in these threatened species.

Interactions between microplastics and Culex sp. larvae in wastewater

Microplastics (MPs) are a growing issue because they endanger both aquatic organisms and humans. Studies have indicated that wastewater treatment plants (WWTPs) are one of the major contributors to MPs in the environment. However, studies on the abundance of MP contamination in WWTPs and its transmission into aquatic organisms are still scarce, especially in Egypt. The goal of this study was to examine the temporal fluctuations in the distribution of MPs in surface water and the dominant macroinvertebrate fauna (Culex sp. larvae) in a fixed wastewater basin in Sohag Governorate, Egypt. The average of MPs in the surface water was 3.01 ± 0.9 particles/L. The results indicated to seasonal variation of MP abundance in the wastewater basin that was significantly higher in winter than in the other seasons. The risk index for polymers (H), pollution load index (PLI), and potential ecological risk index (RI) were used to assess the degree of MP contamination. The basin has moderate H values (<1000) because of the presence of polymers with moderate hazard scores such as polyester (PES), polyethylene (PE), and polypropylene (PP). According to the PLI values, surface water is extremely contaminated with MPs (PLI: 88 to 120). The RI values of surface water showed higher ecological risk (level V). MPs in Culex sp. larvae were seasonally changed with an 85% detection rate, and an abundance average of 0.24 ± 0.65 particles/ind, MP concentration in Culex sp. larvae was influenced by the MP characters (shape, color, and polymer). The larvae of Culex sp. showed a greater preference for black and red fibrous polyester (PES) with sizes (<1000 μm) of MPs. These findings suggest that Culex sp. larvae prefer ingesting MPs that resemble their food. It is possible to overestimate Culex sp.'s preference for lower sizes because of their catabolism of MPs. To better understand the preferences of Culex sp. larvae for MPs, further controlled trials should be conducted. PRACTITIONER POINTS: Wastewater is highly contaminated with microplastics (MPs) in the different seasons. First report of detection of the seasonal abundance of MP in Culex sp. larvae. Culex sp. larvae showed a stronger feeding preference for MPs with specific characteristics. Smaller size and blue polyester fibers were the dominant characteristics of MPs in wastewater.

Influence of synthetic and natural microfibers on the growth, substance exchange, energy accumulation, and oxidative stress of field-collected microalgae compared with microplastic fragment

Synthetic microfibers (MFs), which are Microplastics (MPs), have not received attention commensurate with their abundance in the environment. Currently, limited studies on MFs have focused on their effects on marine organisms. It is therefore necessary to conduct exposure experiments of MFs on freshwater organisms to provide reference data for the ecological risk assessment of MFs. As a primary producer in freshwater ecosystems, microalgae have an ecological niche that is highly overlapping with that of MFs. In this study, we examined the effects of MFs on the growth of Chlorella and indicators of oxidative stress to examine their potential risk on the microalgae population. The results showed that inhibition rate of microalgae increased with MF concentration in the range of 0.01-100 mg/L. Compared with natural fibers such as cotton and wool, PET and PP fibers showed significant growth inhibition, but less so when in fragment form with the same material and concentration. PP and PET particles, whether fibers or fragments, increased the total antioxidant capacity of microalgal cells and caused oxidative damage. To determine the influence of MFs on the interaction of cells in the environment, the exchanged substances and accumulated energy of microalgae cells were also detected. The results indicated that PP and PET fibers, as well as fragments, increased the diameter and membrane permeability of microalgae cell, thus interfering with the cell division and substance exchange processes. PET fibers and fragments showed different interactions at the level of individual cells and populations. This suggests that the evaluation of MPs should consider examinations from cells to population and even community levels in the future.

Microplastics are ubiquitous and increasing in soil of a sprawling urban area, Phoenix (Arizona)

Microplastics are environmental contaminants that have been extensively studied in marine and aquatic environments; terrestrial ecosystems, where most microplastics originate and have the potential to accumulate, typically receive less attention. This study aims to investigate the spatial and temporal soil concentrations of microplastics in a large desert metropolitan area, the Central Arizona-Phoenix Long-Term Ecological Research (CAP-LTER) area. Soil samples from the Ecological Survey of Central Arizona (ESCA) surveys (2005 and 2015) were leveraged to study spatial distributions and the temporal change of microplastic abundances. The temporal soil microplastics data were supplemented by microplastics deposition fluxes in a central location within the area (Tempe, AZ) for a period of one year (Oct 5th, 2020 to Sept 22nd, 2021). Samples were processed and microplastics were counted under an optical microscope to obtain quantitative information of their distribution in soil. Results for the spatial variation of the microplastic abundances in soil samples in Phoenix and the surrounding areas of the Sonoran Desert from 2015 depict microplastics as ubiquitous and abundant in soils (122 to 1299 microplastics/kg) with no clear trends between different locations. Microplastics deposition fluxes show substantial deposition in the local area (71 to 389 microplastics/m2/day with an average deposition flux of 178 microplastics/m2/day) but the role of resuspension and redistribution by dust storms to deposition may contribute to the unclear spatial trends. Comparison between the 2005 and 2015 surveys show a systematic increase in the abundance of microplastics and a decrease in microplastics size. Micro-Raman spectroscopy identified a variety of plastics including PE, PS, PVC, PA, PES and PP. However, a majority of microplastics remained chemically unidentifiable. Polyethylene was present in 75 % of the sampling sites and was the most abundant polymer on average in all soil samples.

From oceans to dinner plates: The impact of microplastics on human health

Microplastics, measuring less than 5 mm in diameter, are now found in various environmental media, including soil, water, and air, and have infiltrated the food chain, ultimately becoming a part of the human diet. This study offers a comprehensive examination of the intricate nexus between microplastics and human health, thereby contributing to the existing knowledge on the subject. Sources of microplastics, including microfibers from textiles, personal care products, and wastewater treatment plants, among others, were assessed. The study meticulously examined the diverse routes of microplastic exposure-ingestion, inhalation, and dermal contact-offering insights into the associated health risks. Notably, ingestion of microplastics has been linked to gastrointestinal disturbances, endocrine disruption, and the potential transmission of pathogenic bacteria. Inhalation of airborne microplastics emerges as a critical concern, with possible implications for respiratory and cardiovascular health. Dermal contact, although less explored, raises the prospect of skin irritation and allergic reactions. The impacts of COVID-19 on microplastic pollution were also highlighted. Throughout the manuscript, the need for a deeper mechanistic understanding of microplastic interactions with human systems is emphasized, underscoring the urgency for further research and public awareness.

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

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

Efficiency of Coagulation/Flocculation for the Removal of Complex Mixture of Textile Fibers from Water

Synthetic fibers enter wastewater treatment plants together with natural fibers, which may affect treatment efficiency, a fact not considered in previous studies. Therefore, the aim of the present study was to evaluate the efficiency of the coagulation/flocculation process for the removal of a mixture of textile fibers from different water matrices. Natural and synthetic fibers (100 mg/L; cotton, polyacrylonitrile, and polyamide) were added to a synthetic matrix, surface water and laundry wastewater and subjected to coagulation/flocculation experiments with ferric chloride (FeCl3) and polyaluminum chloride (PACl) under laboratory conditions. In the synthetic matrix, both coagulants were found to be effective, with FeCl3 having a lesser advantage, removing textile fibers almost completely from the water (up to 99% at a concentration of 3.94 mM). In surface water, all dosages had approximately similar high values, with the coagulant resulting in complete removal. In laundry effluent, the presence of surfactants is thought to affect coagulation efficiency. PACl was found to be effective in removing textile fibers from laundry wastewater, with the lowest removal efficiency being 89% and all dosages having similar removal efficiencies. Natural organic matter and bicarbonates showed a positive effect on the efficiency of FeCl3 in removing textile fibers from surface water. PACl showed better performance in coagulating laundry wastewater while surfactants had a negative effect on FeCl3 coagulation efficiency.

Research and characterization of fibrous microplastics and natural microfibers in pelagic and benthic fish species of commercial interest

The ingestion of synthetic microfibers, the most prevalent type of microplastics in marine environments, and natural fibers was assessed in Engraulis engrasicolus and Mullus barbatus, two commercially important fish species in the Mediterranean Sea. Microfibers were isolated from the fish gastrointestinal tract using a 10% potassium hydroxide solution. For the microfiber characterization, the evaluation of specific morphological features using a light microscope, coupled with the Fourier-transform infrared (FTIR) analysis of a subsample of isolated particles, was applied. The preliminary results showed the occurrence of microfibers in 53 and 60% of European anchovy and Red mullet, respectively. A mean of 6.9 microfibers/individual was detected in anchovies, while on average Red mullet samples contained 9.2 microfibers/individual. The most common colors of fibers in both species were black, blue, and transparent. Visual characterization of fibers allowed the classification of 40% of the items as synthetic microfibers. FTIR spectroscopy confirmed the visual classification by fiber morphology. Microfibers were made of different typologies of polymers, represented by cellulose, cotton, and polyester. These findings confirm as the wide distribution of fibrous microplastics, and natural microfibers may impact both pelagic and deep-sea trophic webs. Despite the presence of microfibers in fish species poses a potential risk to human health, the literature is scarce regarding studies on the uptake by commercial marine fish mostly due to methodological issues. The visual characterization, corroborated by spectroscopic techniques, may be useful to differentiate synthetic and natural fibers, representing a fast and easy method to assess fibrous microplastic pollution in commercially important fish species.