First biomonitoring of microplastic pollution in the Vaal river using Carp fish (Cyprinus carpio) "as a bio-indicator"

Detection and characterisation of microplastics in tap water from Gauteng, South Africa

This study reports the presence, concentration, and characteristics of microplastics (MPs) in tap water in three suburbs in Gauteng Province in South Africa. Physical characterisation was conducted using stereomicroscopy and scanning electron microscopy following staining of MPs with the Rose Bengal dye. The concentrations of MPs in all samples ranged from 4.7 to 31 particles/L, with a mean of 14 ± 5.6 particles/L. Small-sized (<1 mm) and fibrous-shaped MPs were most abundant in all samples. Fibers accounted for 83.1% of MPs in samples from all the three areas, followed by fragments (12.4%), pellets/beads (3.1%), and films (1.5%), with a minor variation in the distribution of shapes and sizes in samples from each area. Raman microspectroscopy was used for chemical analysis, and five polymers were identified, namely: high-density polyethylene, polyurethane, polyethylene terephthalate, poly(hexamethylene terephtalamide), and poly(acrylamide-co-acrylic acid). C.I Pigment Red 1, C.I. Solvent Yellow 4, Potassium indigotetrasulphonate, and C.I Pigment Black 7 were the colourants detected. These colourants are carcinogenic and mutagenic and are potentially toxic to humans. The prevalence of MPs in tap water implies their inadequate removal during water treatment. For instance, the presence of poly(AM-co-AA) suggests that drinking water treatment plants may be a potential source of MPs in tap water. Other polymers, e.g., high-density polyethylene may be released from pipes during the transportation of drinking water. The estimated daily consumption of MPs from tap water was 1.2, 0.71, and 0.50 particles/kg.day for children, men, and women, respectively. The findings of this study provide evidence of the presence of MPs in drinking water in South Africa, thus giving some insights into the performance of treatment plants in removing these contaminants and a benchmark for the formulation of standard limits for the amount of MPs in drinking water.

Validation of qPCR reference genes in the endangered annual killifish Austrolebias charrua considering different tissues, gender and environmental conditions

The annual killifish Austrolebias charrua is an endangered species, endemic to the southern region of South America, which inhabits temporary ponds that emerges in the rainy season. The main anthropogenic threat driving the extinction of A. charrua stems from extensive agriculture, primarily due to the widrespread use of glyphosate-based herbicides near their habitats. Annual killifishes have been used as models for ecotoxicological studies but, up to now, there are no studies about reference genes in any Austrolebias species. This represents an obstacle to the use of qPCR-based technologies, the standard method for gene expression quantification. The present study aimed to select and validate potential reference genes for qPCR normalization in the annual killifish Austrolebias charrua considering different tissues, gender and environmental conditions. The candidate reference genes 18 s, actb, gapdh, ef1a, shox, eif3g, and the control gene atp1a1 were evaluated in male and female individuals in three different tissues (brain, liver, and gills) under two experimental conditions (control and acute exposition to Roundup Transorb®). The collected tissues were submitted to RNA extraction, followed by cDNA synthesis, cloning, sequencing, and qPCR. Overall, 18 s was the most stable reference gene, and 18 s and ef1a were the most stable combination. Otherwise, considering all variables, gapdh and shox were the least stable candidate genes. Foremost, suitable reference genes were validated in A. charrua, facilitating accurate mRNA quantification in this species, which might be useful for developing molecular tools of ecotoxicological assessment based on gene expression analysis for environmental monitoring of annual killifish.

Distinct dynamics in mountain watersheds: Exploring mercury and microplastic pollution-Unraveling the influence of atmospheric deposition, human activities, and hydrology

The intensification of human activities all around the globe has led to the spread of micropollutants in high-mountain freshwater environments. We therefore aimed to assess the geospatial distribution and determine the potential sources of (total-) mercury (THg) and microplastics (MPs) in mountain freshwater ecosystems. To do so, we analyzed THg and MP concentrations in brown trout, biofilm, and sediments from lotic and lentic ecosystems in the Pyrenees - all subjected to different types of human pressure. Additionally, we assessed the potential impacts of these pollutants on fish, and explored the bioindication capacity of brown trout (Salmo trutta fario) and biofilm regarding THg and MP pollution. For the first time, we measured concentrations of MPs trapped in the matrix of freshwater biofilm. Our results suggest that THg in the Pyrenees might be explained by both legacy (regional) and distant sources, in combination with environmental characteristics such as the presence of peatlands or streamwater physicochemistry, while MPs in fish are linked to recent local pollution sources such as single-use plastics. In contrast, MPs in biofilm matrix and sediments indicate a combination of distant (i.e., atmospheric deposition) and recent local pollution sources. Moreover, hydrodynamics and plastic density likely control MP distribution in rivers. Based on Fulton's condition factor, we also found that higher THg concentrations caused a negative impact on fish health (K < 1), while no impact of MPs could be seen. Therefore, we suggest that brown trout and biofilm can serve as bioindicators of atmospheric deposition of THg in high-altitude lakes and that biofilm is a reliable bioindicator to assess MP pollution in remote environments. Brown trout may also act as a bioindicator of MP pollution, but only efficiently in more polluted areas.

The first evidence of microplastic presence in the River Nile in Khartoum, Sudan: Using Nile Tilapia fish as a bio-indicator

The extent of microplastics in African freshwater systems remains less investigated. In Sudan, there is no single study reporting microplastics in water bodies. This scoping study aimed to investigate the presence and characteristics of microplastics (MPs) in Nile Tilapia fish from the River Nile in Khartoum, Sudan. The digestive tracts of the fish were digested using 10% potassium hydroxide, and microplastic particles were extracted by density separation using sodium iodide. 567 particles of different sizes (0.04-4.94 mm), shapes (fibers, fragments, films, foams, and pellets), and colours (mostly green, black, blue, and grey) were identified as microplastics. The average abundance of microplastics was 72.02 ± 62.06 particles/kg, and the average intensity was 18.90 ± 9.17 MPs/fish. Small-sized (<1 mm), fibrous-shaped, and coloured microplastics were most abundant in all samples, representing 56%, 85%, and 84%, respectively. Surface examination by SEM showed signs of fragmentation such as cracks, pits, and pores. Two polymer types (high-density polyethylene and polypropylene) were identified by Raman spectroscopy. The predominance of fibers and fragments (94.5%) over pellets (0.35%) and the apparent signs of fragmentation may indicate that MPs are mostly secondary MPs. Wastewater effluent, domestic discharge, and recreational activities are the potential sources. This scoping investigation provided the first data on microplastic presence in the River Nile in Khartoum, and it could be used to guide future studies to fill research gaps in the region.

Microplastic Abundance and Sources in Surface Water Samples of the Vaal River, South Africa

Microplastics (MPs) have emerged as a global environmental concern due to their persistent nature. In South Africa, microplastic research has primarily focused on marine systems. However, recent years have seen a shift in focus to studying MPs in South African freshwaters. In this study, MPs with a minimum size of 0.055 mm in surface water of the Vaal River, South Africa, were reported. MPs were 100% prevalent, with a mean numerical abundance of 0.68 ± 0.64 particles/m3. Small-sized MPs of < 1 mm accounted for the largest proportion. MPs were chemically identified as high-density polyethylene, low-density polyethylene, and polypropylene according to their Raman spectra. The prevalence of fragments (41.6%) and fibers (38.5%) over pellets (8.1%) indicates that microplastics are from secondary sources. The prevalence of polyethylene and polypropylene is consistent with microplastics being from secondary sources. These polymers are commonly used in single-use plastics, packing bags, textiles, and containers. These characteristics are of great concern due to their implications on the bioavailability and toxicological impacts of MPs. Consequently, these properties may pose more hazards to aquatic biota inhabiting the Vaal River.

Does the mouth size influence microplastic ingestion in fishes?

This study investigated microplastic (MP) contamination in six tropical fish species of different mouth sizes and trophic levels from Saint Martin's Island, Bay of Bengal. A total of 309 microplastics (MPs) were extracted from the gastrointestinal tract (GT) of these selected fishes, where the presence of MPs was 100 %. The mean abundance of MPs was significantly varied among the species and ranged from 4.38 to 10 MPs/GT (p < 0.05). This study revealed that MP incidence was strongly correlated with the mouth-to-body ratio of the selected fishes (r = 0.424, p = 0.003) and trophic levels (r = 0.458, p = 0.002). Results suggest that fish with larger mouths are more likely to ingest MPs, intentionally or unintentionally, compared to those with smaller mouths.

Occurrence of rare earth elements in water, sediment, and freshwater fish of diverse trophic levels and feeding ecology: Insights from the Po river (northwest Italy)

To date, the occurrence of rare earth elements (REEs) in freshwater ecosystems has garnered limited attention in the scientific literature. Furthermore, a dearth of data exists regarding their potential bioaccumulation in freshwater fish. To fill this knowledge gap, we studied REEs concentrations in water, sediment, and fish specimens collected along the Po River (northwest Italy) and calculated biota-sediment accumulation (BSAF) and bioconcentration (BCF) factors, while taking into account fish feeding behavior and trophic level effects on the overall content of total REEs (ƩREEs). The fish communities were composed of native and non-native species. Remarkably low concentrations of REEs (<0.0003 mg/L) were detected in the water samples, indicating REEs insolubility. In contrast, sediment samples were found to be a good sink for REEs, with a higher mean ƩREEs recorded for the samples from the Moncalieri station (70.93 mg/kg). Notably, no significant differences in ƩREEs concentration were observed in the muscle tissue of fish samples from the three stations. The highest mean ƩREEs was recorded in the samples from the Murazzi station (0.027 mg/kg). The BSAF was very low, consistently below the unit, indicating an absence of bioaccumulation in fish muscle from sediment. In contrast, the BCF was high for several REEs, mainly for Sc and Y. While feeding ecology did not appear to affect REEs accumulation in muscle, there was a significant negative relationship between the trophic level and ΣREEs, indicating a trophic dilution of REEs from predator (Silurus glanis) to planktivorous (Alburnus arborella) fish. This study provides baseline concentrations, trophic transfers, and patterns of REEs in a river system. Further studies are needed to understand the transfer of REEs to other biotic components of lotic ecosystems.

Microplastic pollution in the gastrointestinal tract of giant river catfish Sperata seenghala (Sykes, 1839) from the Meghna River, Bangladesh

Freshwater rivers are considered the major route for microplastics (MPs), yet limited studies have been reported on MPs in freshwater river fish, especially in Bangladesh. This research reveals the intake of MPs by the giant river catfish Sperata seenghala, collected from the Meghna River, which is the only outlet of the Ganges-Brahmaputra River. Three locations, namely, Chandpur Sadar, Bhola Sadar, and Char Fasson, along the Meghna River, were selected in order to investigate the gastrointestinal tracts (GIT) of the fish. Ninety percent (n=27) of fish (n=30) were contaminated, with fragment-shaped MPs (65%) as the most abundant among the four types. A total of 179 MP particles were detected using micro-Fourier transformed infrared spectroscopy (μ-FTIR), with an average of 5.96 ± 1.32 MP particles per fish. Among the four size groups, the highest proportion of MPs (54%) occurred in the 45-100 μm group; the dominant color among the seven color groups was white (30%). The highest quantity of MPs was found in the relatively densely populated Chandpur Sadar region. Polypropylene-polyethylene copolymer (PP-PE, 23%) was proportionally dominant among the 15 types. No significant relationship was found between the total number of observed MPs and the GIT weight. This study will help us to understand MP pollution in S. seenghala that may transmit to the human body through the food chain.

The effects of environmental Microplastic on wharf roach (Ligia exotica): A Multi-Omics approach

This is the first report to evaluate the potential effects of microplastics (MPs) on wild wharf roaches (Ligia exotica) in a shoreline habitant. L. exotica is an important plastic detritus consumer in coastal area. A survey was conducted from May to June in the years 2019 and 2020 in two South Korean nearshore sites: Nae-do (as MPs-uncontaminated) and Maemul-do (as MPs-contaminated). MPs (>20 μm in size) were detected highly in gastrointestinal tracts of the L. exotica from Maemul-do, at an average level of 50.56 particles/individual. They were detected in much lower levels in the L. exotica from Nae-do. at an average rate of 1.00 particles/individual. The polymer type and shape were dominated by expanded polystyrene (EPS, 93%) and fragment (99.9%) in L. exotica from Maemul-do. Especially, Hexabromocyclododecanes, brominated flame retardants added to EPS, have been detected highly in L. exotica from Maemul-do (630.86 ± 587.21 ng/g l. w.) than those of Nae-do (detection limit: 10.5 ng/g l. w). Genome-wide transcriptome profiling revealed altered expression of genes associated with fatty acid metabolic processes, the innate-immune response-activating system and vesicle cytoskeletal trafficking in L. exotica from Maemul-do. The activation of the p53 signaling pathway (which is related to proteasome, ER regulation and cell morphogenesis) is likely to be involved in the EPS-uptake of wild L. exotica. Four neurosteroids were also detected in head tissue, and cortisol and progesterone concentrations differed significantly in L. exotica from Maemul-do. Our findings also suggest that resident plastic detritus consumer might be a useful indicator organism for evaluating pollution and potential effects of environmental microplastics.

Investigation of microplastic ingestion in commercial fish from Surabaya river, Indonesia

Microplastics (MPs) were recognized as emerging environmental contaminants and ubiquitously distributed in aquatic environments, including in commercial biota. Fish are estimated as one of the most susceptible aquatic biota to ingesting microplastic (MP). Commercial fish cultivation is commonly developed in urban rivers. This situation may lead to food web safety and human health risks because most fish products are commercially available for consumption. Surabaya River, one of the main rivers in Indonesia, has been polluted by MPs. This river takes essential parts for providing clean water for Surabaya City and fishery. This study aimed to investigate: (1) MP ingestion, abundance, characteristics in commercial fish species in Surabaya River, and (2) potential influencing factors to MP ingestion in the fish. The MP ingestion was found in gills and gastrointestinal tracts (GITs) of seven commercial fish species from the Surabaya River. The highest MP abundance was found in the gill of Trichopodus trichopterus (280.73 ± 162.25 particles/g WW), in the GIT of Rasbora argyrotaenia (358.75 ± 121.98 particles/g WW), and in Notopterus notopterus (186 ± 130.81 particles/individual). The MP abundance was positively correlated to fish body size. The predominant MP polymer in both fish organs was cellophane. These MPs were mostly fiber-shaped, large-sized, and black-colored. The MP ingestion in the fish might be influenced by active/passive uptake routes, specific feeding habits, preference habitats, fish size, and MP characteristics. This investigation reveals the occurrence of MP ingestion in commercial fish, which is closely associated with human health risks via trophic transfer by accidental consumption.

Microplastics transport in a low-inflow estuary at the entrance of the Gulf of California

Microplastics (MPs) are recognized as a global emergent pollution impact, which can affect all food chains. Estimating MPs transport pathways in coastal ecosystems is needed to assess their likely effects. Here, we studied MPs accumulation and transport pathways in the Estero de Urias lagoon system (low-inflow estuary) using field data and a 3D particle model. Field results showed that the MPs present similar abundances throughout the study area during the dry and rainy seasons. Model simulations indicated that i) morphology and tidal currents caused the MPs discharged in the lagoon to remain inside, and ii) wind-induced currents caused the MPs in the coastal area to be transported to the southwest. These transport processes may be responsible for homogenizing MPs concentrations through the studied area. In addition, model simulations suggested that EUL-dense waters can export MPs from the coastal area to the sea bottom.

Occurrence of nano/microplastics from wild and farmed edible species. Potential effects of exposure on human health

The occurrence of nano/microplastics (N/MPs) has become a global concern due to their risk on the aquatic environment, food webs and ecosystems, thus, potentially affecting human health. This chapter focuses on the most recent evidence about the occurrence of N/MPs in the most consumed wild and farmed edible species, the occurrence of N/MPs in humans, the potential impact of N/MPs on human health as well as future research recommendations for assessing N/MPs in wild and farmed edible species. Additionally, the N/MP particles in human biological samples, which include the standardization of methods for collection, characterization, and analysis of N/MPs that might allow evaluating the potential risk of the intake of N/MPs in human health, are discussed. Thus, the chapter consequently includes relevant information about the content of N/MPs of more than 60 edible species such as algae, sea cucumber, mussels, squids, crayfish, crabs, clams, and fishes.

Polyethylene microplastics trigger cell apoptosis and inflammation via inducing oxidative stress and activation of the NLRP3 inflammasome in carp gills

Microplastics cause varying degrees of damage to aquatic organisms. Exposure to microplastics contaminated water, the gills are among the first tissues, after the skin, to be affected by microplastics. As an essential immune organ, prolonged stimulation by microplastics disrupts immune function not only in the gills but throughout the body, yet the underlying mechanisms remain elusive. A model of gill injury from exposure to polyethylene (PE) microplastics was developed in this study. H&E staining revealed that polyethylene microplastics caused gill inflammation, vascular remodeling, and mucous cell proliferation. An increase in collagen indicates severe tissue damage. Additional analysis showed that polyethylene microplastics profoundly exacerbated oxidative stress in the gills. TUNEL assay demonstrated cell apoptosis induced by polyethylene microplastic. The mRNA levels were subsequently quantified using RT-PCR. The results showed that polyethylene microplastics increased the expression of the nuclear factor-κB (NF-κB) pathway (NF-κB p65, IKKα, IKKβ) and apoptosis biomarkers (p53, caspase-3, caspase-9, and Bax). Nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasomes, which is an influential component of innate immunity, were overactive. What's more, the pro-inflammatory factors (TNF-α, IFN-γ, IL-2, IL-6, IL-8, IL-1β) that induce immune disorder also increased significantly, while the anti-inflammatory factors (IL-4, IL-10) decreased significantly. These results suggested that oxidative stress acted as an activation signal of apoptosis triggered by the NF-κB pathway and activating the NLRP3 inflammasome to promote inflammatory immune responses. The present study provided a different target for the prevention of toxin-induced gill injury under polyethylene microplastics.

Comparative Assessment of Microplastics in Surface Waters and Sediments of the Vaal River, South Africa: Abundance, Composition, and Sources

We extracted microplastics from surface water and sediment samples from the Vaal River in Johannesburg, South Africa. Average abundances of 0.61 ± 0.57 particles/ m 3 and 4.6 × 10²  ± 2.8 × 10²  particles/kg dry weight were recorded for water and sediment samples, respectively. In both sediment and water samples, more than 80% of microplastics were fragments and fibers of smaller than 2 mm. High-density polyethylene, low-density polyethylene, and polypropylene were the dominant polymers identified in both sample types. In addition, polyethylene co-vinyl acetate, polyester, polyurethane, and polyethylene/hexene-1-copolymer were also detected in sediment samples. Colored microplastics were the most commonly observed in both sample types; pigment yellow 83 was detected in surface water, and carbon black was detected in both sediment and water samples during Raman analysis. Taking into consideration the physical and chemical characteristics of the detected microplastics, their potential sources include inflow from tributaries, surface run-off from urban city centers, recreational activities, and wastewater effluent from industries and households. Environ Toxicol Chem 2022;41:3029-3040. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Pigment microparticles and microplastics found in human thrombi based on Raman spectral evidence

INTRODUCTION

Environmental microparticle is becoming a global pollutant and the entire population is increasingly exposed to the microparticles from artificial materials. The accumulation of microparticles including microplastics and its subsequent effects need to be investigated timely to keep sustainable development of human society.

OBJECTIVES

This study aimed to explore the accumulation of environmental particles in thrombus, the pathological structure in the blood circulation system.

METHODS

Patients receiving cardiovascular surgical operations were screened and twenty-six thrombi were collected, digested and filtered. Non-soluble microparticles were enriched on the filter membrane and then were analyzed and identified with Raman Spectrometer. The associations of particle status (presence or absence) or particle number in the thrombus and clinical indicators were examined. One strict quality control-particle detection system was designed to eliminate environmental contaminations.

RESULTS

Among twenty-six thrombi, sixteen contained eighty-seven identified particles ranging from 2.1 to 26.0 μm in size. The number of microparticles in each thrombus ranged from one to fifteen with the median reaching five. All the particles found in thrombi were irregularly block-shaped. Totally, twenty-one phthalocyanine particles, one Hostasol-Green particle, and one low-density polyethylene microplastic, which were from synthetic materials, were identified in thrombi. The rest microparticles included iron compounds and metallic oxides. After the adjustment for potential confounders, a significantly positive association between microparticle number and blood platelet levels was detected (P < 0.01).

CONCLUSION

This study provides the first photograph and Raman spectrum evidence of microparticles in thrombi. A large number of non-soluble particles including synthetic material microparticles could accumulate in arteries, suggesting that the risk of microparticle exposure was under-estimated and the re-evaluation of its health effects is urgently needed. There will be a series of reports on assessing the health effects of microparticle exposure in humans in the future and this research provided clues for the subsequent research.